ALBERT

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Muthusamy Balajii, Subramaniapillai Niju〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present study, the feasibility of utilizing 〈em〉Musa spp〈/em〉 “Pisang Awak” peduncle derived ash as a highly effective renewable heterogeneous basic catalyst for transesterification of underutilized non-edible 〈em〉Ceiba pentandra〈/em〉 oil (CPO) was investigated. The physiochemical characteristics of the calcined banana peduncle (CBP) were studied by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy and Energy Dispersive Atomic X-ray spectroscopy (SEM-EDAX). Biodiesel was produced by a two-step esterification-transesterification process. In the first step, FFA content of the oil was reduced from 7% to 1.6% using reaction conditions of 1.0 vol% H〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 concentration, 1h reaction time, 1:4 v/v methanol to oil volumetric ratio with constant reaction temperature of 60 °C. In the second step, response surface methodology (RSM) using central composite design (CCD) was employed to determine the optimal process conditions of transesterification process variables. Based on the RSM results, the optimum process conditions for transesterification of CPO into fatty acid methyl ester (FAME) was found to be 1.978 wt% catalyst concentration, 60 min reaction time, 9.20:1 methanol to oil molar ratio with a maximum predicted FAME yield of 99.36% which was evaluated experimentally as 98.69 ± 0.18%.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119312480-fx1.jpg" width="268" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): S. Shiva Kumar, V. Himabindu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Boron doped Carbon Nanoparticles (B-CNPs) with various boron doping percentages have been successfully synthesized by chemical vapor deposition (CVD) method in the presence of ferrocene and boric acid, further the same was used as a support material for Palladium (Pd) catalyst. The synthesized Pd/B-CNPs with various amounts of palladium (5-30 wt%) were used as a hydrogen evolution electrode in PEM water electrolysis for hydrogen production. The Pd/B-CNPs surface morphological studies and electrochemical performances have been investigated by FE-SEM, EDS, TEM, ICP, XRD, XPS and Cyclic Voltammetry methods. The membrane electrode assemblies (MEAs) have been fabricated using synthesized Pd/B-CNPs and its performance studied in single cell PEM water electrolyser at various experimental conditions. The synthesized 30 wt% Pd/B〈sub〉3〈/sub〉-CNPs (B-doping 6.68 at%) results have shown competitive electrochemical performance (1 A cm〈sup〉−2〈/sup〉 with 2.04 V at 80 °C) and stability. Therefore the synthesized 30 wt% Pd/B〈sub〉3〈/sub〉-CNPs can be used as a promising alternative for Pt based electrocatalysts for HER in PEM cells.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119312558-egi103XPW7ZDF3.jpg" width="442" alt="Image 10373" title="Image 10373"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Gong Chen, Yong Tang, Longhua Duan, Heng Tang, Guisheng Zhong, Zhenping Wan, Shiwei Zhang, Ting Fu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Micro-grooved aluminum flat plate heat pipes (MFPHPs), fabricated by hot extrusion and subsequent inner surface treatment via chemical corrosion, were developed to improve the thermal efficiency and reduce the costs of solar collectors. Thermal performances of MFPHPs, including temperature distribution, maximum heat transfer capability, and thermal resistance, were experimentally conducted. The effects of treatment time and solution concentration on the thermal performance enhancement of MFPHPs were also investigated. The experimental results show that inner surface treatment can substantially enhance the thermal performance of MFPHPs, and different treatment morphologies of inner surfaces result in differences in thermal performance enhancement. The optimal treatment parameters were determined to be a treatment time of 10 min with a solution concentration of 1.5 moL/l. This resulted in the optimal thermal performance enhancement: an increase of approximately 80% in heat transfer capability and a decrease of more than 44% in thermal resistance, compared to the untreated MFPHP. This study provides a convenient, effective, and low-cost method to enhance the thermal performance of MFPHPs applied in solar collectors.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Sergio Paniagua Bermejo, Alba Prado-Guerra, Ana Isabel García Pérez, Luis Fernando Calvo Prieto〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Quinoa is a pseudo-cereal employed to provide nutrition and sustenance for a long time. Currently, the consumption of seeds of this plant is increasing. The seed are the only nutritionally part, which implies that both the husks like the rest of biomass represent a residue vaguely studied. Authors had studied the thermal behavior of these quinoa inedible parts. Fuel properties, biomass composition and DTG profiles were done for an oxidative atmosphere under different heating rates in the same way that several characteristic combustion indexes were estimated. Also, DTG profiles for a non-oxidative environment together with the characterization of the char obtained were showed. Results denoted that quinoa biomass presented a more suitable nature for combustion process compared with the husks. Furthermore, combustion DTG profiles showed two different stages: devolatilization and ignition. The maximum combustion weight loss value (20.63%/min) was achieved for biomass under a 40 K/min rate. DTG profiles under inert atmosphere evidenced two weight loss stages clearly influenced by the cellulose and lignin content. Once again, biomass was the one with the better behavior instead of the husk for this pyrolysis process. Biomass which had good values in terms of yield (26.02%) and heating value (15.41 MJ/kg).〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119312431-egi107K48GW0W9.jpg" width="484" alt="Image 1074809" title="Image 1074809"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Ethan E. Lust, Karen A. Flack, Luksa Luznik〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Flow field results are presented for the near-wake of an axial-flow hydrokinetic turbine in the presence of surface gravity waves. The turbine is a 1/25 scale, 0.8 m diameter, two bladed turbine based on the U.S. Department of Energy's Reference Model 1 tidal current turbine. Measurements were obtained in the large towing tank facility at the U.S. Naval Academy with the turbine towed at a constant carriage speed and a tip speed ratio selected to provide maximum power. The turbine has been shown to be nearly scale independent for these conditions. The selected wave form was intended to represent oceanic swell encountered off the U.S. eastern seaboard. The resulting model wave is a deep water wave, in terms of relative depth, traveling with the “current”, in the opposite direction of the towing carriage. Velocity measurements were obtained using a submersible, planar particle image velocimetry (PIV) system at streamwise distances of up to two diameters downstream of the rotor plane. PIV ensembles were obtained for phase locked conditions with the reference blade at the horizontal position. Phase averaged results for no-wave and wave conditions are presented for comparison showing further expansion of the wake and shear layer in the presence of waves as compared to the no-wave case. When ensembles are selectively sampled on the wave phase, a high degree of coherency is shown to remain and the wake width is shown to undulate with the passing of the wave, with the vertical displacement range on the same order as that of a particle under similar conditions. The impact of waves on turbine tip vortex helical structure is also examined. Waves are shown to change the location of adjacent helices. In the streamwise direction, this changes the pitch of the helix, shown in previous studies to affect the downstream wake recovery distance. In the vertical direction, depending on the wave-induced flow field at the time they were created, vortices are forced outward, into the mean flow or inward, into the wake core, potentially enhancing kinetic energy transport and accelerating the re-energization process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Sadegh Khajepour, Mehran Ameri〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In this paper, the effect of using three solar fields in a solar thermal power plant has been evaluated. Two separate solar direct steam generations are used to provide a portion of the energy required by the high-pressure turbine and low-pressure turbine. The third solar field is used for molten salt energy storage. If the energy stored during the daytime is not enough, the fossil fuel boiler will provide the rest of the energy needed. Given the current price of natural gas, the use of solar energy is not cost-effective, regardless of environmental issues, government incentives or external costs, such as health costs. Furthermore, the use of solar energy for the power plant was unable to make a significant reduction in electricity cost, regardless the 3.5$/MMBTU natural gas price. However, considering the complexity of the solar system, the use of solar energy for the price of the current natural gas is not recommended. By increasing the price of natural gas, the use of solar energy is more economically feasible.〈/p〉 〈p〉The results of the study show that the use of three solar fields (two separate solar fields to produce superheated steam for a high-pressure turbine and low-pressure turbine and a solar field for energy storage using molten salt as thermal energy storage medium) rather than one solar field reduces electricity consumption by 1.83%–13.78% for the price of 9 $/MMBtu natural gas. Although each of the first and second solar fields produce different energy quantities, and therefore, require different field areas, the field coefficient of the field is the same for both solar fields.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Fei Yu, Gongyi Huang, Chuanzhong Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An explicit parameter-extraction method is proposed to estimate the values of fitting parameters in lumped-parameter equivalent circuit model of industrial solar cells. The explicit method is based on polynomial fitting curves on Matlab platform, TCAD device simulation results of Silvaco Atlas, and experimental data of silicon-based solar cells’ current-voltage characteristics. Such an explicit parameter-extraction method can be directly applied into the analytical solutions to one-diode lumped-parameter equivalent circuit model to complete the simulations for electrostatic properties of solar cells. First, the current-voltage characteristics of industrial silicon-based solar cells are also derived analytically as the previous works completed by other researchers and the four key factors especially for the maximum power formula are solved through the effective diode approach. Second, polynomial curve is used to fit current-voltage characteristics from simulation and experiment results of solar cells under illumination. Third, the polynomial fitting result, the short circuit current, and the open circuit voltage are used to extract explicitly all of five parameters included in the one-diode lumped-parameter equivalent circuit model for industrial solar cells. Finally, the extracted fitting parameters are substituted into the analytical solution to current-voltage characteristics and the obtained current-voltage characteristics are compared with device simulation results from Silvaco Atlas and experimental data from silicon-based solar cells. As a result, such an explicit extraction procedure could be regarded as a fast and accurate method to estimate model parameters in industrial solar cells, which is important for not only photoelectric device simulations but also process analysis.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): S. Vijayan, T.V. Arjunan, Anil Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a low cost indirect forced convection solar dryer integrated with porous bed sensible heat storage medium has been developed and studied under the climatic conditions of Coimbatore for drying bitter gourd slices. The experimental setup consists of a solar collector with 2 m〈sup〉2〈/sup〉 area, drying chamber and a centrifugal blower to force the air. The main objective of the study is to investigate the effect of mass flow rate of air on the exegetic and pickup efficiencies of the solar drying system for drying bitter gourd slices. The results indicate that the mass of the bitter gourd slices was reduced from 4000 to 723 g in 7 h at the mass flow rate of air 0.0636 kg/s in solar drying system. The average exergy efficiency values vary from 28.74% to 40.67% for the mass flow rates of air from 0.0141 to 0.0872 kg/s respectively. The average pickup efficiency of the drying air varied from 54.29% to 17.18% for various mass flow rates of air and it decreases with increase in mass flow rate of air. The effective moisture diffusivity of bitter gourd slices was observed from 8.6293 × 10〈sup〉−10〈/sup〉 to 12.9585 × 10〈sup〉−10〈/sup〉 m〈sup〉2〈/sup〉/s, whereas for open sun drying it gives the lowest value of 0.9568 × 10〈sup〉−10〈/sup〉 m〈sup〉2〈/sup〉/s. Environmental impact analysis indicated that the energy payback time for the indirect solar dryer is found to be 2.21 years only. The CO〈sub〉2〈/sub〉 mitigation and earned carbon credit values for the developed system are 33.52 tons and INR 10894 to 43576 for the expected lifetime of 35 years. Impact analysis shows that the solar dryer is a suitable solution for preserving the agricultural products with environmental sustainability.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Wanli Zhang, Hanxue Sun, Zhaoqi Zhu, Rui Jiao, Peng Mu, Weidong Liang, An Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The development of efficient non-metal catalysts (NMC) towards oxygen reduction reaction (ORR) in both acidic and alkaline electrolyte is of great importance for construction of new generation fuel cell. Herein, we demonstrate the fabrication of N-doped hard carbon nanotubes prepared by carbonization of melamine-incorporated nanotube-like conjugated microporous polymers (CMPs), as novel electrocatalysts for efficient ORR. As a kind of metal-free electrocatalyst, the as-prepared carbon nanotubes exhibit superior ORR activity not only in alkaline electrolyte but also in acidic condition. Interestingly, obvious enhancement on the diffusion-limited current density (increased by 1.8 mA cm〈sup〉−2〈/sup〉) for the N-doped products in acid solution is observed by comparison with that of carbonized CMPs nanotubes without N-doping. Furthermore the catalysts also show better methanol immunity than that of commercial 20 wt% Pt/C. And only a slight decrease (14 mV negative shift) in half-wave potential is detected after 5000 cycles in 0.1 M KOH, indicating an ideal electrochemical stability which makes the N-doped hard carbon nanotubes promising candidate as an efficient electrocatalyst for ORR, by combination with their desirable electrocatalytic ORR activity, methanol tolerance and stability.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Ziqian Kong, Baoping Tang, Lei Deng, Wenyi Liu, Yan Han〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Aimed at identifying the health state of wind turbines accurately by comprehensively using the change information in spatial and temporal scale of the supervisory control and data acquisition (SCADA) data, a novel condition monitoring method of wind turbines based on spatio-temporal features fusion of SCADA data by convolutional neural networks (CNN) and gated recurrent unit (GRU) was proposed in this paper. First, missing value complement and selection of variables with Pearson prod-moment correlation coefficient were applied to improve the effectiveness of SCADA data. Second, a deep learning model was constructed by the structures of CNN and GRU. The spatial features in SCADA data were extracted by CNN at every step, and the temporal features in the sequence of spatial features were extracted and fused by GRU. Third, the historical healthy SCADA data was used to train the normal behavior model. At last, the trained model received measured data and output the predicted values. The entire residual between the actual data and the predicted output was calculated to put into the exponential weighted moving average control chart for recognizing the condition of the wind turbine. The effectiveness and availability of the proposed method were proved in measured SCADA data experiments.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): S.S. Simões, J.S. Ribeiro, D. Celante, L.N. Brondani, F. Castilhos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study aimed the investigation of a potential heterogeneous catalyst for the interesterification reaction for soybean biodiesel production. Different types of catalysts (Y Zeolite, MgO, Nb〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 and mixed oxides) were tested in this work. Ca–Mg–Al mixed oxide with 40% wt. Ca was the more suitable catalyst for interesterification reaction. Effects of temperature, catalyst content and methyl acetate to oil molar ratio on product yields were investigated through kinetic experiments. Kinetic behavior of intermediate compounds was also assessed. The best experimental condition was 325 °C, 40:1 methyl acetate/oil molar ratio and 5% wt. of catalyst/oil, with a global yield of 68.55% reached in 80 min with pressure ranged between 5 and 10 MPa. A catalyst reusing test was carried out in this condition. The reaction could be performed for at least three times with the same initial catalyst without a significant activity decay.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119310432-egi10650Q3NZMP.jpg" width="500" alt="Image 106503" title="Image 106503"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Chun Yang, Wei-Qin Cao, Xiao-Feng Ji, Jian Wang, Tao-Lin Zhong, Yu Wang, Qing Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉It is about a method to build direct biomass cells enabling complete fuel oxidation. Heated at a temperature from 40 °C to 90 °C, the fuel (glycerol) will be esterified in a solution of phosphoric acid to form monophosphate. A fuel cell fed with thus partly phosphorylated glycerol come with open circuit voltages varying from 0.65 to 0.83 V. The current densities are close to the values of a fuel cell run in a solution of NaOH, but 10 times higher than that of a cell with a neutral electrolyte (e.g. Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉). Under optimized conditions, peak values of current density and power density are obtained at about 20 mA cm〈sup〉−2〈/sup〉 and 2.2 mW cm〈sup〉−2〈/sup〉 respectively. Thereafter a series of oxidized C〈sub〉1〈/sub〉–C〈sub〉3〈/sub〉 intermediates are detected in the discharged solutions. More importantly several cycles of fuel refeeding do not lead to any accumulation of glycerol or the discharging intermediates. This means in situ phosphorylation can successfully activate the fuel and facilitate its’ complete oxidation. Though discharging performance needs to be further improved, this partly phosphorylation method can be simple and effective to increase fuel utilization percentages in direct saccharide cells.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119310468-fx1.jpg" width="293" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Michael V.W. Cuttler, Jeff E. Hansen, Ryan J. Lowe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Despite Australia having one of the most abundant offshore wave energy resources globally, there remains a lack of understanding of how this offshore resource extends into the coastal zone where most wave energy converters would be deployed. We used the phase-averaged wave model SWAN to simulate 38 years (1980–2017) of wave conditions near Albany, Western Australia, which has been proposed as a future commercial wave energy development site. The nearshore (30 m depth) wave resource varied seasonally and interannually with the wave energy flux and mean wave direction negatively correlated to the phase of the Southern Annular Mode (SAM) and positively correlated to the latitudinal position of the subtropical high-pressure ridge. As a result, the observed positive trend in SAM over recent decades may cause a decrease in nearshore wave energy (including fewer storm events) and an anti-clockwise (more southerly) rotation in wave direction. These changes may facilitate wave energy development and extraction by reducing the number and magnitude of extreme events during which wave energy cannot be extracted and equipment can be damaged. The interannual fluctuations in the wave resource can be significant and should be considered during the site selection for wave energy projects.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Mohammad Mustafa Ghafurian, Hamid Niazmand, Ehsan Ebrahimnia-Bajestan, Robert A. Taylor〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Water vapor is vital both as an energy carrier and as an intermediary state for removing impurities from water. In nature, transpiration occurs when water is transported (against gravity) from the roots to the underside of leaves where it evaporates. Using this process, one large tree can pump and purify 400 L of water each day. Based on trunk cross-sectional area, this corresponds to a water flux range of ∼100–1000 kg/m〈sup〉2〈/sup〉day, but based on evaporation area it only corresponds to a rate of ∼0.1 kg/m〈sup〉2〈/sup〉day. Compared to industrial mechanisms of producing water vapor (i.e. typical thermal-driven systems have a flux of ∼4000 kg/m〈sup〉2〈/sup〉day), natural wood has a relatively low flux. In an effort to boost the flux of sustainable, natural wood, we investigated wood surface modifications, laser carbonization and deposition of gold nanolayers, which achieved an instantaneous evaporation rate of ∼4 kg/m〈sup〉2〈/sup〉h—under 3 kW/m〈sup〉2〈/sup〉 light intensity, exceeding all previous studies of synthetic materials (including 3.8 kg/m〈sup〉2〈/sup〉h reported by Zhou et al. in a 2016 Nature Photonics article) for solar steam generation applications. The cost analysis of different natural and synthetic material-based techniques for solar steam generation indicated that the carbonization and laser treatments are very cost-effective and even the gold coating was comparable to previously reported synthetic materials. Based on these results, we suggest that natural, surface-modified poplar wood could represent a viable alternative to synthetic materials for liquid/vapor separation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Manzoore Elahi M. Soudagar, Nik-Nazri Nik-Ghazali, M.A. Kalam, Irfan Anjum Badruddin, N.R. Banapurmath, Mohamad Azlin Bin Ali, Sarfaraz Kamangar, Haeng Muk Cho, Naveed Akram〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The potential use of aluminium oxide nanoparticles as nanofuel additives was investigated on honge oil methyl ester and diesel fuel blend. The nanofuel blends were prepared by dispersing aluminium oxide in varying quantities in a HOME(B20) (20% biodiesel+80% diesel). Sodium dodecyl sulfate (SDS), an anionic surfactant, was used for a stable dispersion of aluminium oxide nanoparticles in the fuel blends. HOME(B20) fuel with concentration levels of 20, 40, and 60 ppm of aluminium oxide nanoparticles (HOME20, HOME2040 and HOME2060) with varying ratios of SDS surfactants were prepared using ultrasonication technique. The investigated properties of diesel, honge oil biodiesel and nanofuel blends were in agreement with the ASTM D6751-15 standards. The dispersion and homogeneity were established and characterized by using the Ultraviolet–Visible (UV–Vis) spectrometry. The UV–Vis spectrometry results illustrated an increase in absorbance level with a relative increase in the concentration of surfactant. The highest absolute value of UV-absorbency was observed for a mass fraction of 1:4 (Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 NPs to SDS ratio). The investigation was performed at a constant speed of 1500 rpm, and BP of 0 kW, 1.04 kW, 3.12 kW, 4.16 kW and 5.20 kW. The fuel HOME2040 demonstrated an overall improvement in the engine parameters, the brake thermal efficiency (BTE) enhanced by 10.57%, while there was a decline in brake specific fuel consumption (BSFC) by 11.65% and the engine exhaust emission: HC, CO, and smoke reduced by 26.72%, 48.43%, and 22.84%, while the NOx increased by 11.27%. Similarly, the addition of aluminium oxide nanoparticles in HOME(B20) fuel blend resulted in decent reduction in the combustion duration (CD), ignition delay period (ID), improvement in the peak pressure, and a marginal increase in heat release rate (HRR) and cylinder pressure at maximum loading conditions. Based on the experimental results, it is concluded that the aluminium oxide nanoparticles in HOME(B20) fuel demonstrated an overall improvement in the engine characteristics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Kai Feng, Huan Li, Zhou Deng, Qiao Wang, Yangyang Zhang, Chengzhi Zheng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two-phase anaerobic digestion (TPAD) is a commonly used method for recovering energy from food waste, even though the relationship between fermentation type and methane production has not to be thoroughly investigated. In this study, homolactic acid fermentation (HOLA), heterolactic acid fermentation (HELA), butyric acid fermentation (BUA), and mixed acid fermentation (MA) were used in the first phase, and the corresponding methane production levels were compared. HELA and MA resulted in the maximum methane yields of 290 and 287 ml per gram chemical oxygen demand (COD), respectively, but they were not significantly higher than the yield of 279 ml/g COD from single-phase anaerobic digestion (SPAD). During methanogenesis, BUA led to the fastest hydrolysis and methane production rates, followed by MA and HELA. In spite of the similar potential for methane production and energy recovery, TPAD using either BUA, MA, or HELA as the fermentation phase exhibited at least 50% greater methane production efficiency than SPAD. Overall, HELA and MA were found to be the best choices in terms of treatment efficiency and energy recovery.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119311474-egi1000T2WR0GV.jpg" width="353" alt="Image 100020" title="Image 100020"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Io Antonopoulou, Athanasios Spanopoulos, Leonidas Matsakas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The ability of the oleaginous yeast 〈em〉Trichosporon fermentans〈/em〉 to efficiently produce lipids when cultivated in dried sweet sorghum was evaluated. First, lipid production was evaluated in synthetic media mimicking the composition of sweet sorghum stalks and optimized based on the nitrogen source and C: N ratio. Under optimum conditions, the lipid production reached 3.66 g/L with 21.91% w/w lipid content by using a mixture of sucrose, glucose and fructose and peptone at C: N ratio 160. Cultivation on pre-saccharified sweet sorghum stalks offered 1.97 g/L, while it was found that sweet sorghum stalks can support yeast growth and lipid production without the need for external nitrogen source addition. At an attempt to increase the carbon source concentration for optimizing lipid production, the Crabtree effect was observed in 〈em〉T. fermentans〈/em〉. To this end, the yeast was evaluated for its potential to produce ethanol under anaerobic conditions in synthetic media and sweet sorghum. The ethanol concentration at 100 g/L glucose was 40.31 g/L, while utilizing sweet sorghum by adding a distinct saccharification step and external nitrogen source offered ethanol concentration equal to 23.5 g/L. To the authors’ knowledge, this is the first time that the Crabtree effect is observed in 〈em〉T. fermentans〈/em〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 147, Part 1〈/p〉 〈p〉Author(s): Hamed H.H. Aly〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Forecasting of renewable energy resources and their output power is playing a key role to improve the grid energy efficiency by making some load generation management. Tidal currents output power is depending on the tidal currents constitutions (speed magnitude and direction) forecasting. The accuracy of the tidal currents forecasting models is very important especially when we deal with smart grid and renewable energy integration. Many models are proposed in the literature for tidal currents forecasting but most of the models are not able to control the requirements of the smart grid due to their accuracy. This paper is proposing hybrid approaches for harmonic tidal currents constitutions forecasting based on clustering approaches to improve the system accuracy. These hybrid models involve various combinations of Wavelet and Artificial Neural Network (WNN and ANN) and Fourier Series Based on Least Square Method (FSLSM) techniques. The proposed work is validated by using two different datasets; one for tidal currents speed magnitude and the other one for tidal currents direction as well as K-fold cross validation. Simulations results prove the importance of the proposed models to improve the system performance. The proposed models are tested based on actual tidal currents data collected from the Bay of Fundy, Canada in 2008.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 147, Part 1〈/p〉 〈p〉Author(s): Jinghua Yu, Kangxin Leng, Hong Ye, Xinhua Xu, Yongqiang Luo, Jinbo Wang, Xie Yang, Qingchen Yang, Wenjie Gang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Roof receives heat directly from the solar radiation and outdoor air, and the heat transfer of the roof is often greater than that of any external wall. The building roof is usually overheated in summer, causing a great increase in the air conditioning load and negative effects on indoor thermal comfort. Thus improving the thermal insulation performance of the roof is essential for reducing air conditioning energy consumption and improving indoor thermal comfort. In this paper, an innovative pipe-embedded ventilation roof with outer-layer shape-stabilized PCM (named VRSP for short) was proposed. The heat gain is stored in the PCM to migrate excessive heat during the day and released through air ventilation at night. A three-dimensional transient-state heat transfer model of the VRSP system was built by CFD. The effects of phase transition temperature range of PCM, thickness of PCM layer and airflow rate in the ventilation duct on the thermal performance of the structure in five representative climate regions of China were evaluated. Results show that the optimum phase transition temperature ranges of PCM in severe cold region, cold region, hot summer and cold winter region, hot summer and warm winter region and mild region are 31–33 〈sup〉°〈/sup〉C, 34–36 〈sup〉°〈/sup〉C, 36–38 〈sup〉°〈/sup〉C, 34–36 〈sup〉°〈/sup〉C and 29–31 〈sup〉°〈/sup〉C, respectively. The optimum thicknesses of the PCM layer are 25–30 mm, 25–30 mm, 30–35 mm, 25–30 mm and 20–25 mm, respectively. The suitable airflow rates are 1.5–1.9 m/s, 1.6–2.0 m/s, 2.1–2.5 m/s, 1.9–2.3 m/s and 1.4–1.8 m/s, respectively. The conclusion provides valuable guides for the application of VRSP under various climate conditions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 147, Part 1〈/p〉 〈p〉Author(s): Julio Luna, Ole Falkenberg, Sébastien Gros, Axel Schild〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aim of this work is to deploy an advanced Nonlinear Model Predictive Control (NMPC) approach for reducing the tower fatigue of a wind turbine (WT) tower while guaranteeing efficient energy extraction from the wind. To achieve this, different Artificial Neural Network (ANN) architectures are trained and tested in order to estimate the tower fatigue as a surrogate of the traditional Rainflow Counting (RFC) method. The ANNs receive data stemming from the tower top oscillation velocity and the previous fatigue state to directly estimate the fatigue progression. The results are compared to select the most convenient architecture for control implementation. Once an ANN is selected, an economic-tracking NMPC (etNMPC) solution to reduce the fatigue of the WT tower is deployed in real-time. The closed-loop results are then compared to a baseline controller from a renowned WT simulation tool and a classic etNMPC implementation with indirect fatigue minimisation to demonstrate the improvement achieved with the proposed strategy. Finally, conclusions regarding computational cost and real-time deployment capabilities are discussed, as well as future lines of research.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 147, Part 1〈/p〉 〈p〉Author(s): Yang Cai, Wei-Wei Wang, Cheng-Wei Liu, Wen-Tao Ding, Di Liu, Fu-Yun Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper proposed one novel Thermo-Electric Ventilation (TEV) system driven by the concentrated photovoltaic-thermoelectric generator (CPV-TEG), which could use the electric power converted directly from solar energy by CPV-TEG. The effects of incident solar irradiance, number of thermoelectric generators, and ambient air temperatures on the power output of CPV-TEG have been analytically investigated through energy balance and first law of thermodynamics. Furthermore, input current and number of thermoelectric coolers were sensitively varied to optimize the performance of TEV system respectively in heating and cooling modes. Finally, an integrated theoretical and numerical approach was proposed to match the power output of CPV-TEG with the power input of TEV. Modeling results indicate that the output power from CPV-TEG could satisfy the energy demand of TEV system when the input currents of thermoelectric coolers were no more than 2.5 A and 2.8 A respectively for cooling and heating modes. Minimum energy and exergy efficiencies of the system in winter heating mode were confirmed to be 1.67 and 0.24 respectively, which were far higher than that in summer cooling mode. This research may be helpful for enhancing performance and reducing exergy destruction of thermoelectric ventilation system, simultaneously.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 147, Part 1〈/p〉 〈p〉Author(s): Weiwei Zhang, Sheng Huang, Shiyong Wu, Youqing Wu, Jinsheng Gao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The ash fusion characteristics and co-gasification activities of different biomasses (corn straw (CS), rice straw (RS) and rice husk (RH)) are investigated in an ash fusion temperature (AFTs) analyzer and a thermo-gravimetric analyzer (TGA). Moreover, the transformation behaviors of mineral matters during CS/RH and RS/RH co-gasification processes are calculated by FactSage software. Results show that the ash fusion characteristic temperatures (AFTs) of CS/RH and RS/RH mixtures both increase with increasing RH ratio, and the maximum ratio of 75% CS and 55% RS in CS/RH and RS/RH mixtures can avoid the melting and slagging problems during co-gasification processes. Under the desirable RH ratio, the gasification activities of CS/RH and RS/RH mixtures increase with increasing CS or RS ratio. Besides, the increased AFTs of CS/RH and RS/RH mixtures are mainly ascribed to the increased contents of high-melting point quartz [SiO〈sub〉2〈/sub〉] and tridymite [SiO〈sub〉2〈/sub〉] and the decreased content of low-melting point silicate with the increase of RH ratio.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 147, Part 1〈/p〉 〈p〉Author(s): Masoud Kharati-Koopaee, Arman Fathi-Kelestani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research, the effect of wave steepness on the hydrodynamic efficiency of an oscillating water column is examined at different chamber lengths and bottom slope angles. Results show that the best device efficiency for low wave frequencies is obtained at high chamber length and for high wave frequencies, the best device performance is achieved at low chamber length. Numerical findings reveal that for high wave steepness, the change in the chamber length has a negligible effect on the device efficiency at low wave frequencies and at high wave frequencies, the best device performance is attained at low chamber length. Results indicate that for the shoreline oscillating water column, the change in the bottom slope angle away from the resonance condition has a negligible effect on the device efficiency and at resonance condition, high bottom slope angle is preferred in order to obtain the best device efficiency. It is found that at high wave steepness, the device efficiency decreases and no specific resonance condition could be observed. It is also shown that the sensitivity of the device efficiency around the optimal device performance to the damping produced by power take-off device decreases as the wave steepness increases.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Yang Hu, Yunhua Xi, Chenyang Pan, Gengda Li, Baowei Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With development of grid-connected wind power, data-driven wind turbine power curve (WTPC) becomes vital for many valuable applications whereas it is hugely affected by the potential outliers in supervisory control and data acquisition (SCADA) system. In this paper, high-fidelity WTPC modeling and its application on condition monitoring are deeply studied. Firstly, through irregular space-division and nonlinear space-mapping, stepwise data cleaning procedure is proposed. On this basis, the cleaned data are used for high-fidelity modeling where optimized least square support vector machine (LSSVM) is chosen for deterministic WTPC modeling and conditional kernel density estimation (CKDE) is selected for uncertainty modeling after comparison where the models are updated via the sliding time window mechanism. Using the consistency of historical data-driven models in a certain future time window, a daily condition monitoring system, including daily multi-index system and improved fuzzy comprehensive evaluation method (FCEM), is established to monitor future wind turbine condition. Finally, measured data from a wind farm in north China are acquired for validation. The results show that the outliers are effectively cleaned for high-fidelity WTPC modeling. The daily condition monitoring system including daily raw data preprocessing, multi-index system and FCEM algorithm can provide efficient daily rating score.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): M. Brito, R.B. Canelas, O. García-Feal, J.M. Domínguez, A.J.C. Crespo, R.M.L. Ferreira, M.G. Neves, L. Teixeira〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mechanical constraints have a non-negligible influence in the motion of oscillating wave surge converter (OWSC) devices. The key novelty of this paper is a numerical simulation tool for OWSCs that does not neglect or significantly compromise mechanical constraints such as hydraulic power take-off (PTO) system, revolute joints and frictional contacts among components. The paper is aimed at presenting the key components of the numerical simulation tool and at validating it with laboratory data featuring an OWSC with mechanical constraints under regular and irregular waves. It is based on the implementation of the multibody solver of Project Chrono under the Smoothed Particle Hydrodynamics (SPH) model of DualSPHysics, where the SPH solver resolves the interaction between wave and flap and the multibody solver resolves the interaction between flap and mechanical constraints. Comparison between numerical results and experimental data show that the numerical simulation tool properly predicts the dynamics of the OWSC. Furthermore, in what concerns hydrodynamics of the near-flap flow, the computed and measured free-surface elevations and phase-averaged flow field show reasonable agreement. Once properly validated, the numerical simulation tool is then applied to study the influence of several mechanical constraints, PTO damping characteristics and flap inertia on the hydrodynamic of the OWSC. The viability of OWSC design solutions based on the developed numerical simulation tool is emphasised, in view of its performance in the test cases to which it was subjected.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Krystyna Bryś, Tadeusz Bryś, Marderos Ara Sayegh, Hanna Ojrzyńska〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The soil heat fluxes (G) in subsurface shallow depth soil layer (SSDSL) are characterized by dynamics of diurnal, monthly, seasonal and annual behaviour. The soil heat very often is underestimated as a part of heat balance of the pedosphere, because its values are relatively small in comparison with sensible turbulent heat and latent heat fluxes. These fluxes concern mainly with net solar radiation and natural thermal properties of soils and plant cover. The soil heat in SSDSL is jointed with commonly widely available and relatively easy acquiring energy resources. This paper aims to present the thermal regime of heat fluxes in SSDSL and its climatic conditions in central Europe, taking into consideration the agriculture periphery characteristics of Wroclaw (Poland). The measurement results gathered across ten years (August 2007–July 2017) and the conducted thermal analysis aim to evaluate the utilisation of SSDSL as a heat source for ground coupled heat pumps (GCHP). The measurements of G (positive soil heat fluxes G 〉 0 and negative G 〈 0) were done between the active surface (for both of bare soil and grassy area) and their lower layers on an 8 cm depth. The soil temperature data between 5 cm and 10 cm below the ground and the temperatures of the active soil surfaces are also represented and discussed. The ten-year annual average sums for G 〉 0 reached 331,8 MJ∙m〈sup〉−2〈/sup〉 (92,2 kWh∙m〈sup〉−2〈/sup〉) for the bare soil and 179,0 MJ∙m〈sup〉−2〈/sup〉 (49,7 kWh∙m〈sup〉−2〈/sup〉) for the grassy area. The similar ten-year values for G 〈 0 reached 330.3 MJ∙m〈sup〉−2〈/sup〉 (91.8 kWh/m〈sup〉2〈/sup〉) for the bare soil and 170.6 MJ/m〈sup〉2〈/sup〉 (47.4 kWh/m〈sup〉2〈/sup〉) for the grassy area. The heat fluxes of the 5 cm depth soil were higher than for the 8 cm and 10 cm soil. The obtained results fortify the importance and engineering role of the soil heat fluxes in SSDSL. The current results of the thermal analysis and detailed clarifications of the soil positive and negative heat fluxes confirms the energy potential of SSDSL as an environmental friendly, efficient heat source for operation of GCHP through the year.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Ashmore Mawire, Tlotlo M. Lefenya, Chidiebere S. Ekwomadu, Katlego A. Lentswe, Adedamola B. Shobo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal performances of three packed bed latent heat medium temperature thermal energy (TES) storage systems are evaluated during charging and discharging cycles at low (4 mL s〈sup〉−1〈/sup〉), medium (6 mL s〈sup〉−1〈/sup〉) and high (8 mL s〈sup〉−1〈/sup〉) flow-rates. The three phase change materials (PCMs) used in the storage systems are adipic acid, erythritol and eutectic solder (Sn63Pb67). Each TES tank comprises of a packed bed of 40 similar aluminium spherical capsules with the three different PCMs inside each tank. The thermal performance of these systems is evaluated in terms of the temperature profiles, total energy, total exergy, useful energy and useful exergy, during charging and discharging. Erythritol did not undergo phase transition during discharging at all the flow-rates due to super-cooling. The erythritol TES system shows the greatest efficiencies with regards to all the performance parameters considered with an overall energy efficiency of about 39.1%. The efficiencies of all the TES systems generally decreased with an increase in the heat transfer fluid (HTF) flow-rate. Although the eutetic solder TES stored and discharged greater quantities of energy at all the flow-rates, its performance was reduced by the lower degree of thermal stratification in the tank and longer charging and discharging times.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Bin Yang, Jiemei Liu, Yawei Song, Ning Wang, Han Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The preparation process of three common nanocomposite phase change materials (NCPCMs) was studied by using the single-factor test method, and the influences of drying treatment, additives, ultrasonic power and time, base liquid volume and particle concentration on the stability of NCPCMs were analyzed. The results are as follows: (1) Drying treatment had the most significant effect on the stability of ZnO NCPCMs. Additive treatment has the most significant effect on the stability of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, and the improvement degree is about 9 times of CuO and 2 times of ZnO. (2) The ultrasonic power treatment method has the most significant effect on the stability of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 NCPCMs. For the sample with the worst preparation effect, the relative absorbance of the uniformly dispersed Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 NCPCMs increased by 20.30%. (3) The stability of ZnO NCPCMs was significantly affected by ultrasonic time treatment and base liquid volume. Under the two preparation conditions, the relative absorbance of the uniformly dispersed ZnO NCPCMs increased by 65.67% and 38.24%, respectively, relative to the worst-performing samples. (4) The particle concentration factor has the most significant effect on the stability of CuO NCPCMs. At the same time, the optimal preparation scheme of NCPCMs was obtained.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Biao Xiao, Lin He, Shihang Zhang, Tingting Kong, Bin Hu, R.Z. Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to solve the problems of atmospheric pollution and haze caused by traditional coal-fired heating, the promotion and application of clean energy heating methods is urgently needed. The air-source heat pumps are applied in the residential buildings to replace traditional coal-fired heating in Beijing and Tianjin. Limited to the cost and economic conditions, air-source heat pumps are usually installed with the traditional steel radiator. The unreasonable selection and operation of equipment can lead to low energy efficiency of partial load operation. The importance of finding an economical and efficient alternative scheme, therefore, is beyond words. The experimental research and computational fluid dynamics simulation on the performance and air distribution of air-to-air heat pump and air-to-water heat pump under the same operating conditions are done in this paper. The results demonstrate that ATAHP has bigger heating capacity than ATWHP, the decrease of the actual operation COP of ATAHP is 28.30% which is smaller than that of ATWHP by 15.45% with the ambient temperature decreasing from 7 °C to −20 °C. Thus, ATAHP is better than ATWHP at low temperature operation conditions. The temperature and velocity distribution of indoor air with ATWHP is more uniform, but the high speed air with high temperature with ATAHP blows to the head and feet directly. Consequently, the air distribution with ATAHP is more in line with the requirements of thermal comfort. To conclude, ATAHP has better performance and thermal comfort, and ATAHP is more suitable than ATWHP to be applied and popularized in northern China.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): P. Elguezabal, A. Lopez, J.M. Blanco, J.A. Chica〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Active façade systems incorporating solar thermal collectors currently offer very promising energetic solutions. From among the available systems, a simple solution is the unglazed heat collector for potential integration in low-temperature applications. However, when adopting system definitions, the modification of some design parameters and their impact has to be fully understood. In this study, the case of an unglazed collector integrated into a sandwich panel is assessed and a specific analysis is performed for a proper assessment of the influence of key design parameters. Based on that case study of the real built system, a CFD model is developed and validated and a parametric assessment is then performed, by altering the configurations of both the panel and the hydraulic circuit. In this way, the potential of each measure to harness solar energy can be evaluated and each parameter with its different level of impact can be highlighted, to identify those of higher relevance. A characterization of the real solution completes the study, by providing the efficiency curves and the total energy collected during the experimental campaign. The maximum estimate of the efficiency of a 6 m〈sup〉2〈/sup〉 façade was within a range between 0.47 and 0.34 and the heat loss factor was between 4.8 and 7.5. The case study exercises reveal the real energy efficiency and solar production patterns. There was also an opportunity to consider significant improvements to increase the output of the active façade. The main conclusions concerned the different criteria that improved the definition of the system and greater comprehension of alternative designs that may be integrated in the underlying concept.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119311711-fx1.jpg" width="455" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Yafei Shen, Yuewei Zhou, Yuhong Fu, Niyu Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The activated carbons were synthesized from rice husk (RH) and rice husk pellet (RHP) by the two-step pyrolysis (carbonization followed by KOH activation). Based on their textural properties, the activated carbons were comparatively studied for sorption of phenol (tar model compound) in different phases. The surface area (S〈sub〉BET〈/sub〉) and pore volumes of RH and RHP chars could be significantly improved with increasing the amount of KOH. Particularly, the RH char-3 showed a highest S〈sub〉BET〈/sub〉 (1818.45 m〈sup〉2〈/sup〉/g) with a higher micro-porosity (93.3%), so the KOH activation of RH char favored the development of microporous structures. Compared with the RH char-3, the RHP char-3 with relatively low S〈sub〉BET〈/sub〉 (1320 m〈sup〉2〈/sup〉/g) showed a meso-microporous structure along with a lower micro-porosity (69.2%), contributing to a higher breakthrough adsorption capacity (740 mg/g) of gaseous phenol. Generally, the adsorption capacity of phenol in the gas phase was higher than that in the liquid phase. RHP favored to form the hierarchical porous carbon enhancing the phenol molecules transportation via the outer layer and then the phenol molecules uptake by the adsorption sites on the inner layer. Also, the appropriate moisture in biochar benefited for adsorption, while the excessive water formed the liquid film, controlling the molecules transport.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119311875-fx1.jpg" width="271" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): L. Florentino-Madiedo, E. Díaz-Faes, C. Barriocanal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cokes made from briquettes composed of a high volatile bituminous coal combined with four different biomasses and four different binders were analyzed in order to evaluate the influence of these materials on their mechanical strength. The results presented in this work are part of a more extensive research plan aimed at widening the range of alternative raw materials that can be included in coking blends. The briquettes were studied by means of proximate and elemental analyses and density evaluation, whereas the cokes were subjected to micro-strength, compression strength, porous characterization and quantitative evaluation of the textural composition by means of polarized light microscopy (PLM). Various parameters derived from these different techniques were used to explain the effects of biomass and binder on the strength of the coke prepared with the briquettes. Bituminous binders are the most effective because they increase Gieseler fluidity and have a lower volatile matter content than molasses and paraffin. The biomasses that gave rise to the most resistant bio-cokes were lignin and a bio-coal, derived from hydrothermally treated waste lignocellulosic biomass.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Ester Sales-Setién, Ignacio Peñarrocha-Alós〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Wind turbine pitch misalignments provoke aerodynamic asymmetries which cause severe damage to the turbine. Hence, it is of interest to develop fault tolerant strategies to cope with pitch misalignments. Fault tolerant strategies require the information regarding the diagnosis and the estimation of the faults. However, most existing works focus only on open-loop misalignment diagnosis and do not provide robust fault estimates. In this work, we present a novel strategy to both estimate and diagnose pitch misalignments. The proposed strategy is developed at a wind farm level and it exploits altogether the information provided by the temporal and spatial relations of the turbines in the farm. Fault estimation is first addressed with a closed-loop switched observer. This observer is robust against disturbances and it adapts to the varying conditions along the wind turbine operation range. Fault diagnosis is then achieved via statistical-based decision mechanisms with adaptive thresholds. Both the observer and the decision mechanisms are designed to guarantee the desired performance. Introducing some restrictions over the number of simultaneous faulty turbines in the farm, the proposed approach is ameliorated via a bank of the aforementioned observers and decision mechanisms. Finally, the strategies are tested using a well-known wind farm benchmark.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): François-Xavier Faÿ, Eider Robles, Marga Marcos, Endika Aldaiturriaga, Eduardo F. Camacho〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Improving the power production in wave energy plants is essential to lower the cost of energy production from this type of installations. Oscillating Water Column is among the most studied technologies to convert the wave energy into a useful electrical one. In this paper, three control algorithms are developed to control the biradial turbine installed in the Mutriku Wave Power Plant. The work presents a comparison of their main advantages and drawbacks first from numerical simulation results and then with practical implementation in the real plant, analysing both performance and power integration into the grid. The wave-to-wire model used to develop and assess the controllers is based on linear wave theory and adjusted with operational data measured at the plant. Three different controllers which use the generator torque as manipulated variable are considered. Two of them are adaptive controllers and the other one is a nonlinear Model Predictive Control (MPC) algorithm which uses information about the future waves to compute the control actions. The best adaptive controller and the predictive one are then tested experimentally in the real power plant of Mutriku, and the performance analysis is completed with operational results. A real time sensor installed in front of the plant gives information on the incoming waves used by the predictive algorithm. Operational data are collected during a two-week testing period, enabling a thorough comparison. An overall increase over 30% in the electrical power production is obtained with the predictive control law in comparison with the reference adaptive controller.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Muhammad Abdullahi Sokoto, Bijoy Biswas, Jitendra Kumar, Thallada Bhaskar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The prospect of de-oiled seed cakes of African star apple (ASA) and Silk cotton (SCS) as a source of bio-oil was investigated using slow pyrolysis. The study was carried out at a temperatures range of 300–450 °C with a heating rate of 10 °C min〈sup〉−1〈/sup〉 for 60 min residence period in a nitrogen atmosphere. The optimum bio-oil yields for SCS (33.1%) and for ASA (48.3%) were achieved at 400 °C. The Bio-char yield decreases from 300 °C to 450 °C (38%–28%) for ASA seedcake which could be due to greater primary decomposition of the biomass samples. A similar trend also observed for SCS with a lowest bio-char yield of 32% at 450 °C. The GC-MS analysis showed that ASA bio-oil has an acids (25.15%), phenolics (18.35%), and hydrocarbons (18.58%) as the major compounds. N-containg compounds (38.17%), carboxylic acid (23.79%), and phenolic (16.57%) were the dominant compounds in SCS bio-oil. The FT-IR absorption peak showed at 1660 cm〈sup〉−1〈/sup〉 (C = N stretching) with higher intensity for SCS bio-oil. At optimum temperature 400 °C, 72% of ASA feedstock was converted into bio-oil and gaseous products (conversion), while 68% conversion was obtained from SCS at optimum temperature 400 °C.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Rahul G. Makade, Siddharth Chakrabarti, Basharat Jamil, C.N. Sakhale〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The primary objective of the present work is to introduce a new method, i.e., 〈em〉Theory of Experimentation〈/em〉 for prediction of monthly average global solar radiation. Meteorological data for 15 years is accessed considering six input predictors (i.e., latitude, longitude, altitude, relative humidity, temperature, and sunshine hours). Global solar radiation model is developed using various input parameters, and the accuracy of the developed models is assessed using statistical errors. The established model forms are also compared with the models available in the literature. Also, Global Performance Indicator is employed to sort the models for the development of the ranking system. A five-variable global solar radiation model (M-06) is found the best amongst all the proposed models (on training dataset) where the determination coefficient is 0.9424, and the mean percentage error is −0.1524%; whereas, for validation dataset, a two-variable regression model was seen to be the best. The study reveals that the effectiveness of the developed Global solar radiation model does not increase with an increase in the input variables; however, altitude, relative humidity, and sunshine hours are the dominating parameter. The proposed method exhibits a high potential of use in the prediction of monthly average global solar radiation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Fırat Es, Emel Semiz, Efe Orhan, Ezgi Genç, Gamze Kökbudak, Gulsen Baytemir, Raşit Turan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Passivated emitter and rear cell (PERC) concept with an already developed roadmap for 24% efficiency will be leading the photovoltaics industry in the upcoming years. In a few industrial pilot lines, efficiencies above 22% have already been attained. Pilot lines have important roles in bridging lab scale proven concepts with the products which are ready for mass production. Therefore, GUNAM Photovoltaic Line which is specialized on PERC concepts has been established to overcome the barriers that hinder the performance of c-Si solar cells in PERC concepts in a relevant environment. The aim of this article is to show how a loss analysis can be employed in a practical way in an industrially relevant environment. The analysis depends on the first results of the studies from 6 months ramp up period of GPVL. A batch of standard PERC type solar cells with p-type base and atomic layer deposited Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 rear passivation have been fabricated during the ramp up of the line. A detailed gain-loss analysis was performed to address the optical, electrical and recombination losses in order to increase the cell efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Jian Li, Ranhui Liu, Peng Yuan, Yanli Pei, Renjing Cao, Gang Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The rapid development of the wind turbine industry has brought with it increasingly serious environmental problems regarding noise generated by turbines. Therefore, wind turbine noise has become an important research topic to solve the larger issue of environmental noise. Using computational fluid dynamics software and a large eddy simulation turbulence model, the aerodynamic noise created by a 3.0-MW high-power double blade is calculated using the FW-H acoustic model. The discrete characteristics of the tip noise spectrum are determined according to the static pressure and flow field distribution of the double blade. Based on the IEC standard, a monitoring point is selected as the noise-testing index of the fan, and the sound pressure level at this point is determined. The most appropriate location to install the wind turbine is determined based on restrictions on the decibel levels for wind farms. This method can be used not only to study the aeroacoustic characteristics of the blade, but also for guidance regarding the suitable noise level in the installation area of the wind turbines.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Xuanmin Yang, Kang Kang, Ling Qiu, Lixin Zhao, Renhua Sun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pruned apple tree branches are abundant and ideal raw material for biomass carbonization due to less ash. It would provide valuable guide to study the effect of carbonization conditions on the biochar characteristics for high-efficiency energy utilization of pruned branches. In this study, we systematically investigated the effects of carbonization conditions on yield and fixed carbon content by using the reaction temperature, heating rate, and holding time as factors in an experiment. The results were evaluated through a single-factor test and response surface analysis. Based on the results of single-factor experiments, the following conditions were determined to be appropriate for the carbonization of pruned apple tree branches: a temperature of 500 °C, heating rate of 4 °C/min, and holding time of 120 min. According to the central composite design test of the response surface methodology, the temperature, heating rate, and holding time had an extremely significant effect on yield and fixed carbon content. The effects of the main factors influencing yield decreased in the order temperature 〉 holding time 〉 heating rate, whereas that on the fixed carbon content was temperature 〉 heating rate 〉 holding time. In the range of the factor levels studied, the interaction between temperature and holding time has a significant effect on yield and an extremely significant effect on the fixed carbon content. The interactions between pairs of the other factors did not significantly affect the yield or fixed carbon content.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119311681-egi10BF6PLTRB1.jpg" width="500" alt="Image 1061" title="Image 1061"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Mario A. Heredia Salgado, Luís A.C. Tarelho, Daniel Rivadeneira, Valeria Ramírez, Danny Sinche〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The 〈em〉Jatropha curcas〈/em〉 fruit shells (JCFS) and 〈em〉Jatropha curcas〈/em〉 seed cake (JCSC) have drawbacks when used as fuel, namely flame front instabilities and short combustion periods. In this work, a blend of 25 wt% 〈em〉Jatropha curcas〈/em〉 pellets with 75 wt% of pruning residues (PR) resulted in a fuel mixture that promote a stable flame front and the combustion process could be sustained for periods larger than 60 min. The improvement in the combustion of the blend composed of 〈em〉Jatropha curcas〈/em〉 pellets and PR, when compared to mono-combustion of 〈em〉Jatropha curcas〈/em〉 pellets, can be explained in result of the better fuel properties given by PR to the fuel blend. It was observed that PR combustion is associated to higher temperatures in the flame gases and the CO concentration in the flue gas is less than 1500 mg/Nm〈sup〉3〈/sup〉 (dry gases, 13% vol. O〈sub〉2〈/sub〉), thus in accordance to the European standards for solid fuel stoves. Although the PR fraction in the biomass mixtures is high (75 wt%), the observed CO concentration in the flue gas during combustion of the fuel blends was higher than 1500 mg/Nm〈sup〉3〈/sup〉 (dry gases, 13% vol. O〈sub〉2〈/sub〉) especially in the fuel mixtures that incorporate JCFS in their composition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): S. Román, B. Ledesma, A. Álvarez, C. Coronella, S.V. Qaramaleki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Water hyacinth hydrothermal carbonization was studied under different temperature (160–250 C), time (30–120 min) and biomass/water ratio (10–50%) conditions. The research was designed following response surface methodology, which was very useful to infer interactions between variables and to develop models predicting the system behaviour with good accuracy. Output functions were solid yield, hydrochar C and N content, as well as their captures, and heating value. It was found that while temperature was the most influential variable promoting HTC reactions, time and even biomass load were decisive to provide particular C and N captures; based on these results, reaction mechanisms were discussed. On the other hand, 2D graphs allowed to build different scenarios in which target properties might be achieved under a wide range of dissimilar conditions, leading to process optimization. The study was complemented by exploring hydrochar surface properties by N〈sub〉2〈/sub〉 adsorption at 77 K, SEM micrography and XPS analyses.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Çiğdem Şahin, Halide Diker, Dimitra Sygkridou, Canan Varlikli, Elias Stathatos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, graphene oxide (GO) was synthesized via Tour method and then modified with two different amine sources that contained different branched alkyl chains. The GO and modified GOs (mGOs) with dihexylamine (DHA) and 2-ethylhexylamine (2EHA) as amine sources were used respectively as buffer layers in mixed halide mesoporous perovskite solar cells (PSCs) in order to examine whether they could improve their performance. GO and mGO samples were characterized by several techniques such as X–Ray Diffraction, X–Ray photoelectron spectroscopy (XPS), Raman analysis and thermal gravimetric analysis (TGA). The preparation of the CH〈sub〉3〈/sub〉NH〈sub〉3〈/sub〉PbI〈sub〉3-x〈/sub〉Cl〈sub〉x〈/sub〉 perovskite solution was performed using standard Schlenk techniques under argon atmosphere to attain a homogeneous coverage of the perovskite film. The solar cells with the additional layer of mGO derivatives between perovskite and hole transporting layer showed an improved overall performance compared to the reference devices which was attributed to the enhanced charge carrier transport via the mGOs. In particular, 10% increase to the overall performance of the solar cells was monitored in devices where 2-ethylhexylamine (2EHA) modified GO was used, compared to standard cell without buffer layer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Shahryar Khalique Ahmad, Faisal Hossain〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study explores the maximization of hydropower generation by optimizing reservoir operations based on short-term inflow forecasts derived from publicly available numerical weather prediction (NWP) models. Forecast fields from the NWP model of Global Forecast System (GFS) were used to force the Variable Infiltration Capacity (VIC) hydrologic model to forecast reservoir inflow for 1–16 days lead time. The optimization of reservoir operations was performed based on the forecast of inflow. The concept was demonstrated for two dams in the United States. Results showed that a significantly greater amount additional hydroelectric energy benefit can be derived consistently than the traditional operations without optimization and weather forecasts. Goals of flood control and dam safety were also not compromised when exploring opportunities for hydropower maximization. An alternate data-based technique was also demonstrated to improve the forecasting skill and efficiency. The study clearly underscores the additional value of weather forecasts that are available publicly and globally from NWP models for any dam location for hydropower maximization. Given the on-going effort to coordinate strategies for sustainable energy production from renewable energy sources, it is timely that this concept be expanded further to current hydropower dam sites around the world.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Hoai-Nam Nguyen, Paolino Tona〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The main objective in hydrodynamic control of wave energy converters (WECs) is the maximization of the energy captured from the waves. Latching control, model predictive control and “PI” control are examples of implementable strategies surveyed in the literature. “PI” control is the common name of a form of hydrodynamic control where the control force applied to the captor is a proportional-integral feedback of captor velocity. While suboptimal, it has the merit of being simple, requiring only straightforward computations and can be considered a standard solution for WECs with a four-quadrant power takeoff (PTO) system. Adaptive “PI” control has been already discussed in the literature, usually using a gain-scheduling approach, with optimal gains precomputed off-line for a representative set of sea states and applied as a function of estimated sea state conditions. In most literature, only average on-line estimations of sea states have been proposed, with time windows of several minutes. Such intermittent adaptive control laws are clearly suboptimal in terms of energy recovery, since the control gains are not continuously updated whereas the sea state is continuously time-varying. In this paper we present a continuously adaptive “PI” control strategy, whose gains are adapted on-line on a wave-to-wave basis, based on a real-time estimate of the dominant wave frequency of the wave force. The PTO efficiency is taken into account. The proposed control method is validated and compared through experiment for irregular sea states.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Liang Zhao, Yuming Xing, Xin Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents a low melting point Bi–Pb–Sn–Cd alloy as the phase change material (PCM) for a thermal management system. Compared with an organic PCM (stearic acid (SA)), which has a similar melting point of ∼69 °C, the thermophysical properties of the two PCMs were characterized, which revealed that the low melting point alloy (LMPA) had much larger thermal conductivity (∼125.22 W/mK) and volumetric latent heat (∼365.5 MJ/m〈sup〉3〈/sup〉). The analysis results of a 270-day compatibility experiment using scanning electron microscopy (SEM) and the energy dispersive spectrum (EDS) showed that the LMPA had good compatibility with the aluminium alloy and copper. With the same dimensions, the LMPA-based heat sink outperforms the SA and copper foam/SA composite based heat sinks at various power input levels, which could effectively reduce the temperature of the heater and extend the effective managed time at least 1.5 times. The LMPA-based heat sink could also discharge heat more efficiently, which is preferred for cyclic operation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Haoshu Cai, Xiaodong Jia, Jianshe Feng, Wenzhe Li, Yuan-Ming Hsu, Jay Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper studies the application of Multi-Task Gaussian Process (MTGP) regression model to enhance the numerical predictions of wind speed. In the proposed method, a Support Vector Regressor (SVR) is first utilized to fuse the predictions from Numerical Weather Predictors (NWP). The purpose of this regressor is to map the numerical predictions at coarse geographical nodes to the desired turbine location. In subsequent analysis, this SVR prediction output is further enhanced by the MTGP regression model. Based on the validation results on the real-world data from large-scale off-shore wind farm, the prediction accuracies of the NWP are significantly improved at both the short-term horizons (1–6 h ahead) and the long-term horizons (7–24 h ahead) by employing the proposed method. More importantly, the short-term prediction accuracy after enhancement is found comparable or even better than the cutting-edge statistical models for short-term extrapolations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Liu Chen, Yikun Tan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel desiccant wheel air conditioning system that uses high-temperature chilled water from natural cold source (DWACS + HCW) is proposed. The proposed system integrates the renewable regeneration heat source and natural cold source, which are beneficial for energy saving. A model of the proposed system was developed, and the main components and the overall model were experimentally validated. The performance and the effects of the important parameters of the system under high humidity (32 °C, 80% RH), moderate humidity (32 °C, 60% RH) and low humidity (32 °C, 40% RH) conditions was studied numerically. The results showed that the system could achieve the supply air to the required temperature and humidity ratio in high, moderate and low humidity conditions, and compared to conventional solar desiccant wheel air conditioning systems (SDWACS), the energy performance is more efficient mainly due to high cooling and dehumidification capacity of surface air-cooler with high temperature chilled water.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Indu Ambat, Varsha Srivastava, Sidra Iftekhar, Esa Haapaniemi, Mika Sillanpää〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The main objective of the present paper comprises the investigation of biodiesel production from low-cost feedstock such as lard oil and waste cooking oil (WCO) using Sr–Al double oxides. Nanocatalyst was characterised FTIR, XRD, SEM, TEM, BET and XPS. The Sr:Al with 3:1 M ratio showed the best catalytic activity in the conversion of both oils to fatty acid methyl ester. The effect of acetone and tetrahydrofuran (THF) as a co-solvent for transesterification were compared and the best result was obtained with 5% THF. The mutual effect of the nanocatalyst and co-solvent on biodiesel production was investigated. The characterisation of biodiesel synthesised from lard oil and WCO was performed with GC-MS, 〈sup〉1〈/sup〉H and 〈sup〉13〈/sup〉C NMR. Moreover, the optimum reaction parameters for transesterification reaction was analysed and the yield was determined by 〈sup〉1〈/sup〉H NMR. The maximum yield of 99.7% and 99.4% of lard oil methyl ester and WCO biodiesel were observed with a 0.9 wt% catalyst amount, 1:5.5 oil to methanol ratio in a reaction time of 45 min at 50 °C and 60 °C, respectively. The properties of biodiesel from lard oil and WCO were determined by the EN 14214 method. The regeneration, characterisation and reusability of regenerated catalyst was observed.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119312492-fx1.jpg" width="360" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Jianbing Chen, Yupeng Song, Yongbo Peng, Søren R.K. Nielsen, Zili Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Both the operational and ultimate load conditions should be considered in the structural design and reliability assessment of wind turbine systems. In the operational condition, the fatigue load experienced by wind turbine blades is of great concern in design which highly relies upon the rotor’s rotation. Three kinds of methods have been developed to explore the rotational sampling effect of wind speeds on wind turbine blades, which, however, are somewhat inconvenient in practical applications. In view of the recent developments in wind field simulation, a novel rotational sampling method allowing for the analytical expression of fluctuating wind speeds on rotating blades is proposed in the present paper. In contrast to the existing methods, the proposed method circumvents the decomposition of cross power spectrum density (PSD) matrix and the interpolation in spatial and temporal dimensions. In particular, a closed-form expression of the rotational sampling spectrum is provided, thereby the mechanism of transfer of turbulent kinetic energy in frequency domain is quantitatively revealed. For illustrative purposes, fatigue analysis of the blades of a 5-MW offshore wind turbine is carried out, demonstrating the non-negligible influence of the rotational sampling on the fatigue load of blades and the competitive efficiency of the proposed method.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Wei Xu, Changping Liu, Angui Li, Ji Li, Biao Qiao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The application of air source heat pumps is mainly restricted by the outdoor ambient temperature, which causes poor application effects in the severe cold region of China. This paper proposes an innovative hybrid energy system of “solar air collector + air source heat pump + energy storage” that is utilized to save energy for ultra-low energy building in severe cold region. The feasibility and performance of this hybrid energy system is studied in Hailar which is located in severe cold region of China. The hybrid energy system is introduced and the dynamic characteristics of the key components of the system are analyzed in combination with the local meteorological conditions. The results indicate that, in Hailar, where the outdoor heating calculation temperature is lower than −30 °C and solar energy resources are not particularly abundant, the peak inlet air temperature of the air source heat pump increases by no less than 10 °C and the coefficient of performance of the system is expected to be higher than 3.0 under extremely low temperature conditions. Warm air from solar air collector can be supplied for heating without ASHP operation if its temperature is higher than 25 °C. These results provide some references for the application of the hybrid energy system in the severe cold region of China.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Zhiqiang Gong, Peiwen Fang, Zhenbo Wang, Xiaoyu Li, Zhentong Wang, Fanzhi Meng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pyrolysis characteristics of microalgae (MA) and its chemical extraction residue (MR) were evaluated and compared using a thermal analyzer and a tube furnace reactor. Results showed that the pyrolysis process of MA and MR can be divided into three stages, which corresponded to the volatile of free water, the decomposition of organic compounds and the stabilization of residues, respectively. Due to the removal of lipids after MA extraction, only one weight loss peak was recorded in the second stage of MR. Using the methods of Friedman, FWO and Starink, the average activation energies of MA and MR were calculated as 204.72 and 178.51 kJ/mol, respectively. Pyrolysis oil, gas, and char products were obtained from both MA and MR pyrolysis. Main gas products from pyrolysis of MA and MR contained CO〈sub〉2〈/sub〉, CO, H〈sub〉2〈/sub〉 and CHs. Compared with MA pyrolysis, the relative contents of CHs were lower (〈59%) during MR pyrolysis, but the contents of CH〈sub〉4〈/sub〉 were higher. Results for higher hydrocarbons (C〈sub〉4-6〈/sub〉, C〈sub〉6+〈/sub〉) were lower in MR than in MA pyrolysis. MR pyrolysis can be a promising method for the waste treatment with high value-added pyrolysis liquid and gases products.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119309140-fx1.jpg" width="374" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Bruno Vasconcelos da Rosa Pin, Regina Mambeli Barros, Electo Eduardo Silva Lora, Oscar Almazan del Olmo, Ivan Felipe Silva dos Santos, Eruin Martuscelli Ribeiro, João Victor de Freitas Rocha〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study analyzed biogas production from the anaerobic digestion of Coffee Wastewater (CWW), in Brazil. Physicochemical analyzes of CWW were performed before and after biodigestion. Four biodigesters B1, B2, B3, B4 maintained at 37 °C ± 2 °C were connected to a gasometer. 1.35 L of CWW and 0.15 L of inoculum (sludge from an Upflow Anaerobic Sludge Blanket) were fed into biodigesters B3 and B4, resulting in a total substrate level of 1.5 L for each one. Biodigesters B1 and B2 were fed 1.5 L of CWW that was pH adjusted to 6–8 in all four biodigesters at the start of the biodigestion. Theoretical estimations were given for the biomethane potential (BMP) arising from the chemical oxygen demand (COD). Given the BMP values, economic feasibility analysis was performed for a biogas system implemented in a coffee roasting production system under three scenarios: I - BMP for CWW COD without inoculum; II - BMP for CWW COD with inoculum; and III - BMP for the minimum required level of CWW COD needed for the system to be economically viable. The highest methane content observed was 11.4% in B4, which had the highest relative methane production to removed volatile solids (17.31 LkgVS〈sup〉−1〈/sup〉〈sub〉rem〈/sub〉).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Kamal Kumar Agrawal, Rohit Misra, Ghanshyam Das Agrawal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal performance of ground-air heat exchanger (GAHE) depends on the rate of heat transfer between air and soil, which is governed by thermal properties of soil surrounding the GAHE pipe. Soil thermal properties around GAHE pipe can be improved either by increasing its moisture contents or by using some thermally enhanced backfilling materials. In the present study experimentally investigates the thermal performance of ground-air heat exchanger system using a sand-bentonite mixture (dry as well as wet) and compare their performance with the ground air heat exchanger system having native soil (dry as well as wet) as backfilling material. The study acknowledges the highest cooling capacity (125 W) for GAHE with wet sand-bentonite as backfilling material, and after 6 h of continuous operation, it is 38.4%, 18.4% and 11.1% higher than that obtained with dry native soil, dry sand-bentonite and wet native soil, respectively. The study also revealed that thermal performance deterioration factor (TPDF) increases with the duration of the operation. At airflow velocity of 5 m/s, after 6 h of continuous operation highest TPDF is noticed for ground-air heat exchanger with dry soil (0.22); whereas, lowest TPDF is observed for ground-air heat exchanger system with wet sand-bentonite (0.07).〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉Schematic of laboratory experimental setup of GAHE system.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119312315-fx1.jpg" width="271" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Renata A.B. Lima-Corrêa, Cínthia S. Castro, Amanda S. Damasceno, José M. Assaf〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉MgAl hydrotalcite was successfully prepared through the sol-gel method and modified by 〈em〉in situ〈/em〉 addition of base metals (Me = K, Ba, Sr and La). The Me–MgAl hydrotalcites were calcined and the obtained oxides were evaluated as catalysts for ethylic transesterification in order to investigate their potential application for biodiesel production. The Me–MgAl characterization revealed that the materials present different crystalline structures and the metal addition caused surface area reduction and increased the apparent crystallite size. On the other hand, the addition of the base metals to hydrotalcite deeply affected the base properties of the oxides, increasing their catalytic activity. Particularly, the Ba–MgAl presents the highest amount of strong base sites which resulted in a high conversion (≈90%) in the model transesterification reaction between methyl acetate and ethanol. Furthermore, an ester conversion of about 80% was reached in soybean oil transesterification. Moreover, the Ba–MgAl can be reused for 3 batch cycles with low deactivation. These results suggest that Ba–MgAl can be considered a promising heterogeneous catalyst for biodiesel production.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Basar Bozkaya, Wim Zeiler〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Aquifer thermal energy storage (ATES) systems, which utilize underground water for heat exchange with buildings, have been proven to be an excellent heating and cooling source. However, their operation is limited by strict regulations, one of which is the requirement for balance in the amount of heat transfer to the ground. Systems are highly exposed to cooling dominated loads, which results in excess heat injection into the ground. Commonly, an air handling unit is utilized to expel heat from the ATES system. This is known as the direct compensation (DC) method. In this study, an alternative approach that uses night ventilation (NV) was presented as a promising solution in combination with DC. Night ventilation can be used to decrease the cooling load and by using NV the system can avoid excess heat injection into the ground. The DC method was combined with NV under various control settings and compared with a system that uses only DC. The optimal operational setting between DC and NV operation was determined based on simulating a case study building. The study determined that the energy performance of the system can be improved by 16% by optimally adapting NV to the DC method.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Quan-Zhong Liu, Wen-Tao Su, Xiao-Bin Li, Ya-Ning Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dynamic behavior during load rejection process of a reversible pump-turbine is numerically investigated based on the dynamic grid method. For the dynamic characteristics, the external features like runner rotation speed, torque and flow rate are analyzed. Then the time-frequency characteristics of pressure fluctuations at different positions (like guide vane, vaneless space, runner inlet and draft tube) are discussed in details. During the unsteady process of load rejection, four peculiar frequency bands, are identified and their sources are assessed. These frequency bands are 2 low frequency-high amplitude components, marked as zones 〈em〉a〈/em〉 and 〈em〉b〈/em〉, which occur around the zero-torque condition. Another 2 high frequency-high amplitude components, marked as zones 〈em〉c〈/em〉 and 〈em〉d〈/em〉, appear near the maximum reversed flow condition. Besides, the rotor-stator interaction plays an important role in the pressure pulsation bands distribution, showing components multiples of runner rotational frequency. They could propagate towards both upstream and downstream. For reversed flow condition, it is also found that the entrance flow from draft tube into runner contributes most energy to the pressure fluctuations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): H. Jokar, M. Mahzoon, R. Vatankhah〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dynamic modeling and free vibration analysis of horizontal axis wind turbine (HAWT) blades in the flap-wise direction are addressed in this paper. Blade kinetic and potential energy are evaluated while taking into account the influences of gravity force, centrifugal force, and the blade rotary inertia. Using Hamilton's principle, a nonlinear partial differential equation with time and space varying coefficients together with appropriate boundary conditions is derived as a novel and comprehensive dynamic model for the blade vibration in the flap-wise direction. After linearizing and simplifying the nonlinear model, the Rayleigh-Ritz method is employed to find natural frequencies and their associated mode shapes. Furthermore, the National Renewable Energy Laboratory (NREL) 5-MW reference wind turbine is chosen to investigate the effects of the rotary inertia, angular velocity, hub radius, pitch and precone angles on its dynamic characteristics. It is shown that increasing the hub radius and the angular velocity or decreasing the rotary inertia, significantly increases the natural frequencies while design parameters such as pitch or precone angles slightly affect the dynamic characteristics of the blades. The accuracy of the simplified model is also verified by comparing results for natural frequencies with some existing data in the literature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Shifeng Fu, Yuan Zheng, Kan Kan, Huixiang Chen, Xingxing Han, Xiaoling Liang, Huiwen Liu, Xiaoqing Tian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to explore the impact load and instantaneous fluid pressure of transient flow on pump station system under the nonregulative operating conditions, the transient characteristics of an axial flow pump during start-up process are investigated experimentally and numerically. To simulate transient flow of the pump, the rational speed is set by force coupling. In order to simulate the movement of the gate with two flap doors attached, the moving mesh technique is adopted. The results of numerical simulation agree well with the experimental data. During the start-up transient process, the transient characteristics parameters, such as pump rotational speed, head, and flow rate change significantly. Transient impact head rises to a peak of 1.87 times the rated head as the rotational speed reaches the rated speed. The whole impeller passage is full of recirculation, flow separation and vortices. The pressure distribution of the impeller blade changes obviously. In the process of pump start-up, the vortex core zones gradually increase, massively appear at the leading edges of the blade and in the passage of the impeller at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉t〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉0.6〈/mn〉〈/mrow〉〈/math〉 s, and then decrease. Our studies could help to avoid pump vibration and blade crack in engineering.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Ahmed Fathy, Mohamed Abd Elaziz, Abdullah G. Alharbi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fuel cells (FCs) penetrated strongly in many applications, modeling of FCs became a major challenge in recent years due to their characteristics, there are some missing data in the datasheet. This paper presents a novel hybrid optimization approach comprising vortex search algorithm (VSA) and differential evolution (DE) for estimating the optimal unspecified parameters of the proton exchange membrane fuel cell (PEMFC). The parameters to be evaluated are seven, ξ〈sub〉1〈/sub〉, ξ〈sub〉2〈/sub〉, ξ〈sub〉3〈/sub〉, ξ〈sub〉4〈/sub〉, λ, R〈sub〉c〈/sub〉 and b to minimize sum squared deviation between the experimental and calculated polarization curves. The hybridization between VSA and DE is proposed to enhance the performance of VSA and prevent falling in local optima, DE is used as a local search method to promote the process of exploitation followed in VSA. The analysis is performed on different PEMFCs, 250 W stack, NedStack PS6, BCS 500-W, and SR-12 PEM 500 W, the obtained results are compared to those obtained via other approaches. In 250 W stack, four sets of actual voltage have been used, two of them are used for the optimization process while the others are employed to check the validity of the obtained model. The obtained results confirmed the superiority and reliability of the proposed approach.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Mohammad Rezvanpour, Danial Borooghani, Farschad Torabi, Maryam Pazoki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study aims to investigate how Calcium Chloride Hexahydrate (CaCl〈sub〉2〈/sub〉·6H〈sub〉2〈/sub〉O) as a phase change material (PCM) can regulate the PV cells temperature and improve the electrical performance of photovoltaic panels in a completely cold environment in Tehran, Iran. Moreover, TRNSYS simulation software was employed to validate the experimental Results. Also, a novel kind of facile and cost-effective system design and data acquisition were introduced. A general analysis for all the experiments’ days and an investigation on a particular day at the end of November for having a closer look was done. Then, a comparison between experimental and simulation results was performed. In this regard, experimental outcomes showed a maximum temperature drop by 26.3〈sup〉∘〈/sup〉C (38% of reduction) for the PV-PCM panel compared to the conventional PV module. Furthermore, PV-PCM panel benefited from a power output increase by 1.16 W (24.68% of increase) during November and December. Finally, modeling outcomes followed the experimental data perfectly with very low errors. With this in mind, the minimum and the maximum difference between experimental and simulation results were 0.96% and 8.25% respectively, which demonstrated a great agreement between these data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 146〈/p〉 〈p〉Author(s): Roman I. Egorov, Alexander S. Zaitsev, Hong Li, Xin Gao, Pavel A. Strizhak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nowadays, the recovery of combustible industrial waste is a very popular approach to supply cheap fuel to various consumers. However, due to the physical and chemical properties of the waste, it requires special preparation to be used effectively. The main features of the direct light-induced conversion of waste-derived coal-water compositions to syngas were investigated. Unlike classical techniques, the proposed method involves solar light, which is a renewable energy source. The fundamental intensity thresholds were shown when fuel was gasified by nanosecond pulses (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mn〉8〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mi〉J〈/mi〉〈mo linebreak="badbreak"〉/〈/mo〉〈mi〉c〈/mi〉〈msup〉〈mrow〉〈mi〉m〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉) and continuous wave laser light (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mn〉700〈/mn〉〈mo linebreak="goodbreak" linebreakstyle="after"〉−〈/mo〉〈mn〉800〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mi〉W〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉/〈/mo〉〈mi〉c〈/mi〉〈msup〉〈mrow〉〈mi〉m〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉). Such light flow parameters are fully achievable by solar radiation. The dependencies of syngas component concentrations on the light intensity were shown as well as similar dependencies for the conversion rate and specific conversion energy (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mo〉∼〈/mo〉〈mn〉3.5〈/mn〉〈mspace width="0.25em"〉〈/mspace〉〈mi〉M〈/mi〉〈mi〉J〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉/〈/mo〉〈mi〉k〈/mi〉〈mi〉g〈/mi〉〈/mrow〉〈/math〉 for optimal gasification conditions).〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119311668-fx1.jpg" width="363" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Yuchen Tang, John W.M. Cheng, Qinwei Duan, Cheuk Wing Lee, Jin Zhong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The power output of solar photovoltaics (PV) may have sharp fluctuations and its impact has to be carefully evaluated before integrating significant PV facilities into the power grid. Variability of solar resources is best measured by ground-based measurements. However, distributed ground-measured solar data is not available everywhere, and it would take considerable cost and time to obtain such data. Therefore, it is important and beneficial to model and estimate the variability of distributed PV generation even with insufficient solar data at each location. This study proposes a new methodology to generate spatially-distributed synthetic PV data based on detailed ground measurements collected at a few sites. The synthetic PV data is examined with specific criteria and the feasibility for simulating spatially-distributed PV generation is verified. A case study for Hong Kong is conducted using both the real and synthetic solar data. It is demonstrated that individual PV facilities can have significant fluctuations on a minute-by-minute basis, but the fluctuations can be significantly reduced if PV facilities are more spatially-distributed. The improvement to the estimation of solar variability with the proposed method is illustrated and the significance of its applications is discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Wenguang Ding, Li He, Dinka Zewudie, Huilin Zhang, Tanjia Binte Zafar, Xinde Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As interdisciplinary research, this Gender and Energy study innovatively revealed the crucial role of Tibetan women in using, saving and developing energy. We chose a typical Tibetan area named Gannan Prefecture in northwestern China, we chose three total grassland counties in Gannan; all three communities still have a nomadic lifestyle and do not have sufficient energy. After we concluded the close relationship between gender and energy in this area, we compared our research area with other Tibetan area those are located in Sichuan, Qinghai and Tibet. This comparison helped to figure out the relationship between Tibetan women and energy in China. The results showed a significant increase of total household energy consumption and the energy efficiency and the decrease of the disease rate because of using renewable energy and clean devices. It also improved women's empowerment in household energy management and promoted cultural change. However, a Tibetan woman's daily working time increased by 1 h from 15 h/day to 16 h/day. The reasons behind gender inequity include Religion influence, Social change and Industrial structure. This paper conclude the changes and attempts to analyze the internal factors, and tries to bring about some policy advice to benefit the Tibetan women.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Zongxi Qu, Wenqian Mao, Kequan Zhang, Wenyu Zhang, Zhipeng Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Precise and reliable wind-speed prediction is vital for wind-farm operational planning. However, wind speed series usually have complex features, such as non-linearity and volatility, which makes the wind energy forecasting highly difficult. Aimed at this challenge, this paper proposes a forecasting architecture based on a new hybrid decomposition technique (HDT) and an improved flower-pollination algorithm (FPA)-back propagation (BP) neural network prediction algorithm. The proposed HDT combines the complete ensemble empirical mode decomposition adaptive noise (CEEMDAN) and the empirical wavelet transform (EWT), which is unique, since the EWT is specifically employed to further decompose the high frequency intrinsic mode functions (IMFs) generated by CEEMDAN to reduce prediction complexity. And then an improved BPNN with the flower-pollination algorithm is applied to forecast all of the decomposed IMFs and modes. To investigate the forecasting ability of the proposed model, the wind speed data collected from two different wind farms in Shandong, China were used for multi-step ahead forecasting. The experimental results show that the proposed model performs remarkably better than all of the other considered models in one-step to five-step wind speed forecasting, which indicates that the proposed model is highly suitable for non-stationary multi-step wind speed forecasting.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Ioannis Kougias, Sándor Szabó, Alexandros Nikitas, Nicolaos Theodossiou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Several Mediterranean islands are not connected to the main electricity grid yet meaning that independent local grids cater for their power requirements, mainly using imported fossil fuels whose resources scarcity, especially during the high-demand summer months, is a significant challenge. Seasonal variability in power demand, fuel price volatility, as well as a growing tourism development, impose some additional complexity. The present study analyses specific island grids of the Aegean Sea. Selected islands are analysed as case studies over a 20-year period (2016–2036). The developed energy modelling exercise uses a Harmony Search Algorithm in its core. It investigates whether the deployment of renewable energy sources could lead to a sustainable system, decrease the current burden from the government budget, and support local resources. In doing so we examine whether an increased share of RES, battery storage, and their combination could reduce islands’ reliance on imports and potentially eliminate the current heavily subsidised status quo. The results show that a 30% increase of the consumption will require increases in installed power capacities by 40–70%, in the best case scenario. The latter involves significantly lower per-kWh cost, between 17% and 36% of the current values, due to the large share of RES.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): T. Osório, P. Horta, M. Collares-Pereira〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The use of solar thermal energy to supply industrial process heat is one of the most promising areas for solar market growth. Whereas low temperature (T 〈 100 °C) applications and the higher end of medium temperature applications (200 °C 〈 T 〈 400 °C) are well suited for stationary collectors and line-focusing tracking collectors, respectively, a gap in collector offer exists in between. Non-imaging CPC (Compound Parabolic Concentrator) type concentrators show the potential to cover this gap when designed for a quasi-stationary (or seasonally tilt adjusted) operation, making use of the advantages of concentration while not depending on tracking systems, thus presenting a great potential for low cost production. Many factors, from the geometrical design to materials, production, installation conditions, O&M, operation temperature and resource availability have an impact on the performance and cost, and must be accounted for to find the optimum collector design. In this study, we developed a method for a customized design of a quasi-stationary CPC-type collector in which the Levelized Cost of Heat delivered is minimized. This methodology, based on a database of several collector configurations, will make it easier for any manufacturer to identify the most cost-effective solution for a particular installation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Karthik Rajendran, James D. Browne, Jerry D. Murphy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper documents a techno-economic assessment of biomethane feedstocks from urban, rural, and coastal settings. Additionally, the effect of three upgrading technologies was investigated, ranging from commercialised systems (water scrubbing) to more advanced systems: power to gas systems employing hydrogen to capture CO〈sub〉2〈/sub〉; and microalgae cultivation utilising CO〈sub〉2〈/sub〉 in biogas. In total, nine scenarios were investigated based on a combination of the three feedstock groups and the three upgrading technologies. The levelized cost of energy and the incentive required to allow financial sustainability were assessed. The assessment showed that water scrubbing was the cheapest upgrading method. The optimum scenario was the combination of urban based feedstock (food waste) with water scrubbing upgrading costing 87€/MWh, equivalent to 87c/L diesel equivalent. The incentive required was 0.13 €/m〈sup〉3〈/sup〉 (or per L of diesel equivalent), however if power to gas was used to upgrade, an incentive of 0.40 €/m〈sup〉3〈/sup〉 was required. This was expected as food waste attracts a gate fee. Rural-based plants (using slurries and grasses) are expected to provide the majority of the resource however, for this to become a reality incentive in the range 0.86–1.03 €/m〈sup〉3〈/sup〉 are required.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148118312941-fx1.jpg" width="428" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Terence Macquart, Alireza Maheri〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Variable-speed stall-regulated (VS-SR) wind turbines can be designed to produce power as efficiently as variable-speed pitch-controlled (VS-PC) systems. However, amongst the main drawbacks of VS-SR systems high transient power and low predictability have been the primary factors in favour of adopting VS-PC system for multi-MW wind turbines. Cyclic and stochastic loads leading to fatigue failure is one of the prime considerations for large wind turbines. In contrast to the current trend of research, which is focused on load alleviation by integrating active flow controllers, this paper highlights the potential benefits of VS-SR wind turbines in reducing fatigue loads. Adopting the NREL 5 MW wind turbine as the baseline, blades are redesigned for stall-regulation. It is shown that a well-designed VS-SR wind turbine experiences significantly less fatigue loads compared to VS-PC systems. It also results in low power transients near and above rated wind speed. Taking into account added complexity, mass and maintenance costs of wind turbines utilising active flow controllers and in view of the recent progresses that have been made regarding the aeroelastic stability of stalled blades, VS-SR systems seem to have a role to play in the design of future wind turbines.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): E.L.V. Eriksson, E.MacA. Gray〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For a successful transition to a renewable energy economy, optimisation of renewable energy systems must evolve to take into account not only technical and/or economic objectives, but also environmental and socio-political objectives. A Normalised Weighted Constrained Multi-Objective (NWCMO) meta-heuristic optimisation algorithm has been proposed for achieving a compromise between mutually conflicting technical, economic, environmental and socio-political objectives, in order to simulate and optimise a renewable energy system of any configuration. In this paper, an optimisation methodology based on these four classes of objective is presented. The methodology was implemented using Particle Swarm Optimisation and tested against data from the literature. In the Case Study the original results could be reproduced, but the newly-implemented algorithm was further able to find a more optimal design solution under the same constraints. The influence of additional quantified socio-political inputs was explored.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): M.I. Dieste-Velasco, M. Díez-Mediavilla, D. Granados-López, D. González-Peña, C. Alonso-Tristán〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Daylighting is recognized as an important and useful strategy in the design of energy efficient buildings. Daylight is still the best source of light for good colour rendering and visual comfort. In this study, a new model of global luminous efficacy over a horizontal surface is proposed. A comparative study of eighteen classic models is presented, to obtain global horizontal illuminance, using both, the original formulation and new formulae with local adaptations, in order to determine the most suitable models for the conditions in Burgos (Spain). With this aim in mind, the selected models consisted of six models developed for all sky conditions, five models for clear sky conditions, three for partly cloudy sky and four for modelling overcast sky conditions. These eighteen models were also compared with the proposed model using experimental global illuminance measurements for different sky conditions. It was shown that the proposed model behaved in a better way than most of the classic models selected from the literature; both for all sky conditions and for particular sky conditions (clear, partly cloudy and overcast). The proposed model was therefore generally applicable, with no need to employ a different model for each particular sky condition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Laureen Meroueh, Karthik Yenduru, Arindam Dasgupta, Duo Jiang, Nick AuYeung〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As greenhouse gases threaten our environment, it has become increasingly necessary to replace consumption of fossil fuels with renewable energy. Without energy storage, solar cannot provide power at night during times of peak demand, resulting in a gap between supply capabilities and demand. Solar thermochemical energy storage (TCES) has potential to resolve this critical temporal issue. An 800MWh〈sub〉th〈/sub〉 TCES subsystem has been designed to cost-effectively convert solar energy to electricity. An evaluation of each required component is provided, including the reactor chemistry. Strontium carbonate decomposition is used to densely store high temperature thermal energy via chemical reaction, while two different CO〈sub〉2〈/sub〉 storage methods are considered. To determine the practical feasibility of these schemes, a probabilistic analysis has been performed to explore exergy and energy efficiency, and cost. It has been found that a scheme storing CO〈sub〉2〈/sub〉 via sorbents is capable of ∼71% energy and ∼87% exergy efficiency, and an installed cost of ∼48 USD kWh〈sub〉th〈/sub〉〈sup〉−1〈/sup〉.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148118312552-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Cheng-Long Wang, Jing-Hu Gong, Jia-Jie Yan, Yuan Zhou, Duo-Wang Fan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The efficiency of GaAs solar cell was significantly reduced resulting from non-uniformity of energy flux-density on receiver surface, and damage of solar cells was made by “hot spots”. In this paper, a light funnel is added between the concentrator and the receiver to improve the uniformity of energy flux-density on receiver surface, which is designed according to the ray tracing method. The simulation result shows that the uniformity of the energy flux-density on the receiver surface is 92.26%, which agrees with the experimental result (94.64%). According to the maximum output efficiency of GaAs solar cell, the layout range of the cell is determined. The simulation results shown that the cell is arranged in the radius of 58 mm, which is similar to the experimental value (60 mm), and the effective area rate of the photoelectric conversion is 69.4%. At normal operation temperature (20 °C), the photoelectric conversion efficiency is 29.64%, and the total efficiency is about 83%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Enrico G.A. Antonini, David A. Romero, Cristina H. Amon〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Accurate quantification of wake losses is crucial in wind farm economics. Computational Fluid Dynamics (CFD) has been proven to be a reliable solution to simulate many complex flows, but several studies showed that its effectiveness in wind farms simulations has not always been consistent. In this work, we investigate the causes for that inconsistency and propose a modeling framework to overcome them. A CFD model was developed using the actuator disk technique to simulate the wind turbines and the surface boundary layer approximation to simulate the ambient conditions. The developed CFD model was implemented for three different wind farms with publicly available experimental measurements. The predictions of CFD model were post-processed with an innovative method that uses a Gaussian-weighted average of a set of CFD results for different wind directions to account for the wind direction uncertainty in the experimental data. Our results show that the proposed method significantly improves the agreement of the CFD predictions with the available experimental observations. These results suggest that the discrepancies between CFD predictions and experimental data reported in previous works, attributed to inaccuracy of the CFD models, can be explained instead by the uncertainty in the wind direction reported in the data sets.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Md Tasbirul Islam, Nazmul Huda, R. Saidur〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study performs a techno-economic analysis of concentrating solar power (CSP) technologies for Malaysia. The solar resource assessment was done by analyzing various rural and regional locations using NASA Surface Meteorology and Solar Energy database. Three different technologies, parabolic trough collector (PTC), solar power tower (SPT) and solar parabolic dish (SPD) were assessed under different economic criterions. Results based on the analysis show that PTC and SPT type plants are particularly suitable for locations at East and Peninsular Malaysia. However, considering simple payback, the net present value (NPV) and internal rate of return (IRR), it is found that PTC type CSP plant will be the most eligible for CSP plant development. Sensitivity analysis is performed to investigate the effect of the levelized cost of electricity (LCOE) on the various project discount rate. Regional renewable energy policy development and regulatory reform in feed-in-tariff (FiT), hybrid technology (PTC with biogas, solar PV and biomass) implementation, project financing under clean development mechanism (CDM) and lesson learned from international experience in local PTC equipment manufacturing are some of the crucial future policy outlooks that need to be applied for CSP technology implementation, as well as long-term sustainable renewable energy system development in the country.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Burak Kurşun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, the effect of the internal longitudinal fins with the flat and sinusoidal lateral surface on the thermal performance of the parabolic trough receiver tube was investigated. Nusselt number (Nu), friction coefficient (f), thermal enhancement factor (ψ) and circumferential temperature difference (ΔT〈sub〉max〈/sub〉) were evaluated by the numerical analyzes. Analyzes were carried out using the different amplitude (a) and periodic length (p) values of the sinusoidal geometry for the different Reynolds numbers (Re). It was observed that the most important factors affecting the heat transfer were the fluid inlet temperature (T〈sub〉in〈/sub〉) and the a value. The highest enhancement in the Nu was found to be 25% and 78% for the flat and sinusoidal fin, respectively. The ΔT〈sub〉max〈/sub〉 with the sinusoidal lateral surface geometry decreased in the range of 66–164 K. With the increase in the Re, the ψ remained approximately constant for the flat fin geometry (ψ ≈ 1,43). For the sinusoidal lateral surfaces, the ψ fell below 1 in high amplitude and Re values. For the T〈sub〉in〈/sub〉 in the range of 300–600 K, the ψ value in the range of 0.85–2.32 were obtained. The results of the analysis revealed that the sinusoidal lateral surface geometry contributes to the heat transfer enhancement.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Lukas Mohr, Vanessa Burg, Oliver Thees, Evelina Trutnevyte〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A fast and effective uptake of bioenergy can be fostered by identifying regions where both the resources availability and socio-economic contexts are suitable. This paper uses cluster and hot spot analysis on the spatially-explicit data of bioenergy potential in 2294 Swiss municipalities. The identified clusters, hot spots and cold spots of municipalities in terms of bioenergy are then assessed for their socio-economic characteristics. As a result, five municipality clusters (groups) with similar bioenergy potential structure in Switzerland are identified: (1) forest wood, (2) manure, (3) mixed agriculture, (4) low potential and (5) anthropogenic bioenergy municipalities. Swiss bioenergy hot spots lie in urban or intensely farmed areas of the Central Plateau, while the cold spots are located in the Alps. The socio-economic analysis shows that factors such as household income, political orientation and population density differ strongly between various clusters, hot spots and cold spots. These results help to find areas where new bioenergy projects are best located from a resource and socio-economic perspective and allow developing bioenergy promotion strategies that are tailored to local circumstances.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119303982-fx1.jpg" width="423" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): S. Beetham, J. Capecelatro〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work presents a numerical study of biomass pyrolysis in turbulent riser flow. Eulerian–Lagrangian simulations of unbounded sedimenting gas-solid flows are performed to isolate the effects of particle clustering on the production of syngas and tar. This configuration provides a framework to resolve the relevant length- and time-scales associated with thermal, chemical and multiphase processes taking place in the fully-developed region of a circulating fluidized bed riser. A four-step kinetic scheme is employed to model the devolatilization of biomass particles and secondary cracking of tar. Two-way coupling between the phases leads to clusters of sand particles that generate and sustain gas-phase turbulence and transport biomass particles. Neglecting the heterogeneity caused by clusters was found to lead to a maximum over-prediction of syngas yield of 33%. Further, it was found that two-dimensional simulations over-predict the level of clustering, resulting in an under-prediction of syngas and tar yields.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119304008-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Cunfeng Ke, Yaning Zhang, Yanan Gao, Yaoyu Pan, Bingxi Li, Yunpu Wang, Roger Ruan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a CFD model was developed to simulate syngas production from microwave-assisted air gasification of biomass. The energy source term under microwave irradiation was coupled in the model to describe the effect of microwave power and the gasification model was established by Euler-Euler method in commercial software Ansys Fluent. Both gas and solid phases were treated as continuous phases, and they have independent governing equations. The two-fluid model was used to describe the two-phase flow and interaction, and the standard 〈em〉k〈/em〉-〈em〉ε〈/em〉 model was used to close the governing equations. The heterogeneous reaction rate between gas and solid and the homogeneous reaction rate between gases were calculated by the finite rate/eddy dissipation model. The fast and transient control characteristics of microwave heating were loaded into the gasification reaction model through UDF compiling function.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Tamilselvan Pachiannan, Wenjun Zhong, Tiemin Xuan, Bei Li, Zhixia He, Qian Wang, Xiong Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Application of biodiesel is very important for reducing the consumption of fossil fuels and improving emissions performance of internal combustion engines in the transportation field. Hydrogenated catalytic biodiesel has attracted more attention due to the high quality and eco-friendly nature. Hence, in order to provide more fundamental data for applying this biodiesel in engines, the spray liquid length, ignition and combustion characteristics for both diesel and hydrogenated catalytic biodiesel has been researched in a constant volume combustion chamber to see their differences and similarities, which can be used for determination of the possible proportion of hydrogenated catalytic biodiesel in blends for further research in engines. The results show that the spray liquid length of hydrogenated catalytic biodiesel is shorter than that of diesel fuel, which indicates that hydrogenated catalytic biodiesel has better atomization and less chance for occurrence of wall-impingement. While a shorter ignition delay of hydrogenated catalytic biodiesel reveals that it cannot be applied in blends with a large proportion due to knocking combustion. However, a shorter ignition delay of hydrogenated catalytic biodiesel means that it is a highly active fuel which can be used to engines as a blend for new advanced combustion modes. The lift-off lengths were compared with different optical methodologies. Lift-off length is more sensitive to fuel properties rather than temperature under low ambient temperature conditions. The relationships between spray liquid length and lift-off length and between ignition delay and lift-off length were also compared.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Ivan Bortel, Jiří Vávra, Michal Takáts〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study presents the experimental results from comparison of standard diesel fuel, pure hydrotreated vegetable oil (HVO) and a blend consisting of 30% HVO and 70% standard diesel fuel. The renewable fuel called HVO helps to reduce well to wheel emissions of CO〈sub〉2〈/sub〉 and suppresses disadvantages of fatty acid methyl ester (FAME). Experiments have been done on a passenger car size single cylinder compression ignition engine equipped with a contemporary common rail injection system. Tested operating modes and procedure were based on a World Harmonized Stationary Cycle (WHSC). Common gaseous emissions, smoke number, opacity, particulate matter (PM) and particle number (PN) were measured. Weighted average of measured quantities per the test and individual modes of the test were analyzed. Results confirm positive or neutral influence of HVO on the most of measured emission components and performance parameters. The decrease in order of tens of percent was observed in case of emissions of CO, THC, PM and opacity. Emissions of NO〈sub〉x〈/sub〉 and CO〈sub〉2〈/sub〉 decreased and power increased in order of percentage. The effect on PN was not consistent.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Rajat Kanti Samal, M. Tripathy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The purported social, economic and environmental benefits are resulting in increased wind penetration in existing power systems. However, due to inherent uncertainty of wind energy, thermal generators are expected to maintain security and reliability of power systems. Further, in view of the huge investments in existing power plant installations, thermal power may not be completely replaced by renewable energy sources such as wind power in near future. Therefore, reduction in capacity factor of the existing thermal generators due to wind integration is a major policy concern. This aspect must be juxtaposed with benefits of wind integration such as cost savings and emission reduction. The current study introduces a Capacity Factor Violation Index (CFVI) to evaluate the impact of wind integration on capacity factor of thermal generators. A distance metric comprising of cost savings, emission reduction, network losses and CFVI is proposed based on Compromise Programming (CP). Sensitivity analysis is performed by varying the wind penetration and turbine ratings and the impact on the distance metric is investigated. The proposed methodology is comprehensively demonstrated in eleven popular test power systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Pejman Salimi, Omid Norouzi, S.E.M. Pourhoseini, Pietro Bartocci, Ahmad Tavasoli, Francesco Di Maria, S.M. Pirbazari, Gianni Bidini, Francesco Fantozzi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, Cladophora glomerata, a harmful seaweed, is converted into an olive-shaped magnetic biochar by a slow pyrolysis process catalyzed by iron. The resultant magnetic biochar has a high surface area of 296.4 m〈sup〉2〈/sup〉 g〈sup〉−1〈/sup〉 with a carbon-rich structure that makes it suitable to be used as an electrode in Li-ion batteries. The catalytic pyrolysis process showed significant effect on steam reforming, ketonization and deoxygenation and/or denitrogenation reactions. The overall quality of the pyrolysis products increases: the gas contains a higher percentage of hydrogen (up to 22%), while the oil is enriched in furans (with a selectivity of about 14%). The electrochemistry behavior of magnetic biochar has been also evaluated, using galvanostatic charge–discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analyses. The electrochemical results indicated a higher initial specific discharge capacity (740 mAh g〈sup〉−1〈/sup〉) and great cyclic stability for magnetic electrode as compared to the biochar electrode.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Jing Zhang, Decong Zheng, Kai Wu, Xiuquan Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study used Response Surface Methodology to investigate the effects of moisture content, temperature and applied pressure on the density, durability and impact resistance of millet bran briquettes. Furthermore, this study analyzed the optimum conditions for preparing the millet bran briquette using Generalized Distance Function. It was found that the density, durability and impact resistance of the millet bran briquettes increased as the temperature increased and as the moisture content decreased. As pressure increased, density, durability and impact resistance of the briquettes initially increased and then decreased. High-quality briquettes made of millet bran could be produced within the range of moisture content from 5% to 10%, temperature from 80 °C to 110 °C and pressure from 110 MPa to 130 MPa. The optimum moisture content, temperature and pressure were 5.4%, 101.9 °C, and 122.7 MPa, respectively. The density, durability and impact resistance under optimum conditions were 1.21 g cm〈sup〉−3〈/sup〉, 95.7% and 99.64%, respectively. Millet bran possessed good fuel quality and could be successfully used as professional feedstock for producing solid biofuel.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Rade M. Ciric〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Climate change mainly caused by increased greenhouse gases and reduced fossil fuel reserves, have launched a more intensive use of renewable energy on a global scale. One of the oldest types of the renewable sources is well known small hydro electric facility. In this paper description of small hydro plant location, selection of the turbine, sizing of the plant, connecting plant to the grid, as well as the legal aspect and environmental impact of the future facility in Serbia are presented and discussed. Besides, techno-economic analysis of future small hydro electric plant is presented and discussed. The main contribution of this paper is multidisciplinary approach to complex analysis of building, integration, economic performance and environmental impact of a small hydro-plant demonstrated on the specific site in Serbia. Finally, major barriers and threats for the growth of the small hydro-electric power capacity have been identified and proposals to increase the penetration level of the small hydro and other renewable sources into the grid in Serbia are made. To increase the contribution of the small hydro and other renewables in Serbia and South-East Europe countries, the gouverments should remove all the bariers and strongly encourage the investment in the renewable energy sector.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Ganesh Kumar Poongavanam, Balaji Kumar, Sakthivadivel Duraisamy, Karthik Panchabikesan, Velraj Ramalingam〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study aims at analyzing the heat transfer and pressure drop characteristics the by determination of improved Nusselt number in a double pipe heat exchanger, whose outer surface of the inner tube is modified through the shot peening process. The attained convective heat transfer coefficient (CHTC) and pressure drop of water flow in the heat exchanger with this modified surface are first measured and compared with a high conductivity copper tube construction. The study is to analyze the variations in CHTC and the pressure drop of the activated carbon (AC) - solar glycol (SG) based nanofluid. The experiments stimulated nanomaterials volume concentrations of the nanofluids such as 0.2%, 0.4% and 0.6%. The Nusselt numbers at mass flow variation rates in the range of 0.04, 0.055 and 0.08 kg/sec with shot peened heat exchanger. The presence of AC nanomaterials in the SG enhances the Nusselt number by 26.25%, 40.79%, and 57.06% for 0.2, 0.4 and 0.6% volume concentrations respectively, at a mass flow rate of 0.04 kg/sec in the shot peened heat exchanger. The average CHTC of the nanofluid containing 0.6% of AC nanomaterials is noted to be augmented to a maximum of 71% at 0.04 kg/sec.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): M.N. Nabi, M.G. Rasul, M. Anwar, B.J. Mullins〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study investigated the impact of the addition of a novel series of biodiesels on diesel engine performance, emissions and combustion characteristics. Two non-edible biodiesels, namely waste cooking oil and macadamia oil (〈em〉Macadamia integrifolia〈/em〉) biodiesels were experimentally tested in this study. The fuel blends were prepared in such a way that the fuel oxygen remains at 3.35 wt% in the blend. A 4-stroke, 4-cylinder, naturally aspirated diesel engine was used for all experiments. The engine was coupled and loaded with an eddy current dynamometer. The experimental results indicated that compared to diesel, all diesel-biodiesel blends show no significant changes in engine performance, but higher combustion efficiency and significant reductions in all major diesel emissions with a little penalty of NOx emission. Fuel energy and exergys were almost unchanged or slightly lower than diesel.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): C.I. Rocabruno-Valdés, J.G. González-Rodriguez, Y. Díaz-Blanco, A.U. Juantorena, J.A. Muñoz-Ledo, Y. El-Hamzaoui, J.A. Hernández〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The objective of this research was to develop a direct artificial neural network with the ability to predict a corrosion rate of metals in different biodiesel. Experimental values were obtained by the electrochemical noise technique, EN, as well as, information reported in the literature. A backpropagation model was proposed with three layers; metal and biodiesel composition, blend biodiesel/diesel, total acid number (TAN), temperature and exposure time were considered as input variables in the model. The best fitting training data were acquired with 24:4:1, considering a Levenberg –Marquardt learning algorithm, a hyperbolic tangent and linear transfer functions in the hidden and output layer respectively. Experimental and simulated data were compared satisfactorily through the linear regression model with a correlation coefficient of 0.9885 and a mean square error, MSE, of 2.15 × 10〈sup〉−4〈/sup〉 in the validation stage. Furthermore, the model agreed the requirements of the slope and the intercept statistical test with a 99% confidence. The obtained results indicated that the ANN model could be attractive as corrosion rate estimator.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Sivakumar Esakkimuthu, Venkatesan Krishnamurthy, Shuang Wang, Abd El-Fatah Abomohra, Sabarathinam Shanmugam, Sankar Ganesh Ramakrishnan, Sadhasivam Subrmaniam, Swaminathan K〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The strategic microalgal lipid production without growth reduction is the desideratum for sustainable microalgal biodiesel production. The present study investigated the effect of polysorbates (polysorbate 20, polysorbate 40, polysorbate 60 & polysorbate 80) supplementation on growth, biomass and lipid production of microalga 〈em〉Tetradesmus obliquus〈/em〉 BPL16〈em〉. T. obliquus〈/em〉 BPL16 at controlled condition showed 12.5% dry cell weight (DCW) of lipid content and 0.8 g L〈sup〉−1〈/sup〉 of biomass production. Each of the four tested polysorbates at various concentrations magnificently influenced the green microalga with a maximum lipid production of 47.1% DCW and 46.5% DCW achieved at 0.15% of polysorbate 80 and 0.1% of polysorbate 60 supplementations respectively. The maximum biomass (2.6 g L〈sup〉−1〈/sup〉) production was achieved at 0.15% of polysorbate 40 and polysorbate 60 supplementation respectively. In addition, neutral lipids and vital fatty acids proportion increased at high lipid productive conditions enabled by polysorbate supplementation.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119304161-egi1065HWN6TCN.jpg" width="461" alt="Image 10656" title="Image 10656"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Mohammad Sadegh Javadi, Seyed-Ehsan Razavi, Abdollah Ahmadi, Pierluigi Siano〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A multi-objective wind farm integration framework is proposed in this paper which considers the composite generation and reliability assessment and annualized operating and investment cost evaluation. An emission-controlled policy is adopted such that the amount of SOx and NOx decreases in line with renewable resource planning. Since the incorporation of large-scale distant wind farms is a problem of the multi-objective mixed-integer type with nonlinearities and non-convexities, this paper utilizes a fast elicit multi-objective Non-dominated Sorting Genetic Algorithm II (NSGA II) by probabilistic indices. It is noted that the impacts of the unavailability of the transmission system are modeled employing DC Optimal Power Flow (OPF) based on the incidence matrix together with the static security evaluation. Furthermore, in order to assess the performance of the suggested approach, the model is implemented on the Roy Billinton Test System (RBTS). Afterwards, distant wind farms integration into Iran’s South-West Regional Grid (ISWRG) is studied.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Ahmed Sadeq Al-Fatesh, Hanan atia, Ahmed Aidid Ibrahim, Anis Hamza Fakeeha, Sunit Kumar Singh, Nitin K. Labhsetwar, Hamid Shaikh, Shamsudeen O. Qasim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biogas, an emerging renewable replacement to natural gas (fossil fuel), is 60–70% methane and 30–40% CO〈sub〉2〈/sub〉 by volume and can be produced from organic matter by anaerobic bacteria. Dry reforming of methane (DRM) technology has gained growing interest as this reaction converts natural gas/biogas into syngas that can be used for the generation of clean fuel, alcohols and variety of other chemicals. In this study, a Ni based catalyst supported over mesoporous silica (MCM-41) and promoted by gadolinium (Gd) metal was synthesized and tested for its activity for DRM reaction. The catalytic performance of the catalyst was found to be greatly enhanced with about 0.1 wt% Gd loading. Thus, Gd can act as promoter for Ni based catalyst in DRM reaction. This catalyst converts CH〈sub〉4〈/sub〉 and CO〈sub〉2〈/sub〉 with high conversions, i.e. 〉87% and 〉91% respectively, into syngas having H〈sub〉2〈/sub〉/CO ratio nearly equal to 1 showing potential for catalyzing this reaction.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119303878-egi10WV4VBN82X.jpg" width="411" alt="Image 10482" title="Image 10482"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Nurgul Ozbay, Adife Seyda Yargic, Rahmiye Zerrin Yarbay Sahin, Elif Yaman〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study is aimed to investigate thermal and catalytic pyrolysis of banana peel. In the first part of the study, banana peel was pyrolyzed by varying the temperatures between 400 and 700 °C. It was seen that higher temperature caused in lower bio-oil and bio-char yields but higher gas yields and optimum temperature was determined as 550 °C. In the second part, the mesoporous material Al-SBA-15 with the typical hexagonal arrangement of SBA-15 verified via XRD possesses Lewis and Brönsted acid sites (NH〈sub〉3〈/sub〉-TPD), large surface area and wide pore diameter (N〈sub〉2〈/sub〉 physisorption) was able to catalyzing of banana peel biomass resulting in bio-oil yields of 18–28% with varying catalyst/biomass ratios (0, 5, 10, 15, 20 wt%). The highest bio-oil yield from the catalytic pyrolysis was 18.64% with 15 wt% catalyst/biomass ratios. The composition and physical properties of the bio-oils were reported that the catalyst increased oxygen removal from the bio-oil and also developed the production of desirable products like phenolics and aromatic compounds. The results confirmed the catalytic pyrolysis of banana peel was well related to the textural properties of catalysts.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119303763-fx1.jpg" width="360" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Leon Mishnaevsky〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A short overview of main repair techniques for wind turbine blades and the related problems of computational mechanics is presented. Computational models of the leading edge erosion of wind turbine blades, injection repair and viscous flow, patch/scarf repair as well as curing and adhesive development are reviewed. Both the degradation of wind turbine blades during service (caused by surface erosion, surface cracking, delamination, fiber failure) and the repair procedures (coating, patch and scarf attachment, injection and curing of adhesives) represent the multiscale processes, controlled by geometrical., blade, patch, scarf geometries), mechanical (strength of composite, strength of adhesive, coating, stress distribution) and physical/chemical effects (curing, viscous flow, humidity, temperature and UV effects). For the further optimization of repair technology and efficiency, multi-physical, multiscale computational models should be employed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 140〈/p〉 〈p〉Author(s): Ahmet Sarı, Amir Al-Ahmed, Alper Bicer, Fahad A. Al-Sulaiman, Gökhan Hekimoğlu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Myristic acid (MA) with a melting temperature around 54 °C has huge prospects for solar passive thermal energy storage applications. However, like all other fatty acids (FA), it is also suffers from issues like leakage and low thermal conductivity (TC), when considered for latent heat thermal energy storage (LHTES) applications. Here, to overcome the seepage problem, MA was incorporated within the silica fume (SF) using simple direct impregnation method. To deal with the TC issue, prepared SF/MA pre-composite was doped with carbon nanotubes (CNTs) at three different weight percentage (0.3, 0.5 and 1.0 wt%) and eventually enhanced its TC by about 9.4%, 21.9% and 43.8%, respectively. The chemical and morphological structures of the SF/MA/CNTs developed as novel shape-stabilized composite PCMs (SS-CPCMs) were evaluated by FTIR, XRD, SEM and DSC analysis. The heat storage capacities of the doped and undoped SS-CPCMs were found in the range of about 87–91 J/g with good thermal stability up to 190 °C. Long standing-thermal cycling study was performed with the selected SS-CPCM doped with CNTs (1.0 wt%). No visible degradation or chemical changes were observed even after 1000 thermal cycles. CNTs doping significantly improved the heating and cooling performance of SF/MA composite.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148119304148-egi1045VMVNS7L.jpg" width="328" alt="Image 10457" title="Image 10457"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 134〈/p〉 〈p〉Author(s): Tesfayesus Zinare Mamo, Abhishek Dutta, S. Anuradha Jabasingh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a pilot scale continuous stirred-tank reactor (CSTR) was used to investigate the startup of an anaerobic system, followed by a bench scale test to analyze the biogas production. Wastewater from pressing and crushing leaves of the pineapple crop was used as a substrate in the CSTR. During the study period, the organic loading rate (OLR) was gradually increased and parameters such as volatile fatty acids (VFA), temperature, pH, bio-gas production and chemical oxygen demand (COD) were carefully monitored. The result of the bench scale test showed the potential of the wastewater for producing the biogas. The study indicated an OLR of 3.8 g COD/L/d, and a maximum biogas production of 3.3 L/d, with an average of 2.8 L/d. The COD removal efficiency reached its highest peak with a value of 64.8%, when the OLR was 3.43 g COD/L with the hydraulic retention time (HRT) of 20 days. Based on the measurements made throughout the test period, there were no indications of the presence of toxic elements in the wastewater, which could inhibit the anaerobic degradation process. This study is an attempt to provide a vigorous solution for the pineapple industry wastewater scenario, thereby aiming at sustainable energy production.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148118313776-egi10K2JW6BLCL.jpg" width="246" alt="Image" title="Image"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Hewei Tang, Boyue Xu, A. Rashid Hasan, Zhuang Sun, John Killough〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The successful modeling of wellbore heat exchangers requires tight coupling between the formation heat conduction and the wellbore thermal dynamics. In this paper, we developed three representative solutions: a fully numerical solution that treats both formation and wellbore numerically, a semi-numerical solution that treats formation analytically and wellbore numerically and a fully analytical solution that treats both formation and wellbore analytically. The outlet temperature, pressure, and heat flow rate predicted by the three solutions are compared. The results of this comparison indicate that the fully numerical solution is the only accurate solution for the early transient time. After the system reaches quasi-steady state, temperature and heat flow estimated from all three solutions are in very good agreement. The analysis of transient fluid properties and mass flow rates revealed that constant fluid property model cannot accurately estimate the pressure loss for the system. The newly proposed fully analytical solution is applied in an economic analysis problem for calculating the optimal insulation thickness and mass flow rate to minimize the cost of generated power.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 134〈/p〉 〈p〉Author(s): Chao Wang, Enqi Bu, Ying Chen, Zhengdong Cheng, Jingtao Zhang, Riyang Shu, Qingbin Song〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Photocatalytic reforming of biomass-derived hydrocarbons and water has been confirmed as an efficient approach for hydrogen production. In this work, anatase TiO〈sub〉2〈/sub〉 based Janus-type catalyst was synthesized by a selective surface modification method to realize Pickering interfacial catalytic hydrogen production through photoreforming of bio-derived biphasic system. The results showed that the Janus-type catalyst possessed a huge potential for promoting hydrogen production in biphasic system. Although the surface electrochemical hydrogen evolution property was examined to be slightly attenuated after surface modification, the as-prepared Janus-type TiO〈sub〉2〈/sub〉 exhibited almost doubled photoreforming H〈sub〉2〈/sub〉 yield at the emulsion interface than that of the bare TiO〈sub〉2〈/sub〉 in conventional biphasic system, and over 10 times higher than that of the bare TiO〈sub〉2〈/sub〉 in pure water. This excellent performance was mainly due to the exposed Janus-type anatase TiO〈sub〉2〈/sub〉 at the interface offering the high accessibility to reactants with larger mass transfer area. The reaction rate was found to be associated with the concentration of Janus-type catalyst which could directly influence the size evolution of emulsion droplet. In cyclic reaction tests, the established Pickering interfacial catalytic hydrogen production system revealed that both emulsification performance and catalytic stability had a strong influence on the cyclic stability.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0960148118310644-egi10HC08PMK8J.jpg" width="301" alt="Image" title="Image"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 134〈/p〉 〈p〉Author(s): Gregory W. O'Neil, Tian Qing Yen, Michael A. Leitch, Gary R. Wilson, Emily A. Brown, David A. Rider, Christopher M. Reddy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Unique algal lipids known as alkenones were evaluated as potential phase change materials (PCMs). Alkenones were isolated and purified from commercial 〈em〉Isochrysis〈/em〉 algal biomass and their thermal properties evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Alkenone crystallinity appears to impact latent heat of fusion (ΔH〈sub〉fus〈/sub〉), however both the ΔH〈sub〉fus〈/sub〉 and melting temperature (∼65 °C) of two different alkenone compositions obtained from separate commercial 〈em〉Isochrysis〈/em〉 suppliers were nearly identical. Compared to a synthetic 〈em〉bis〈/em〉-fatty acid PCM, alkenones showed improved thermal stability by TGA and comparable ΔH〈sub〉fus〈/sub〉 (up to 275 J/g) by DSC. Overall the results demonstrate competitive properties for alkenones to other renewable and non-renewable PCMs such that alkenones represent a promising and potentially superior alternative for various ‘green’ PCM technologies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 133〈/p〉 〈p〉Author(s): Ahmed Laouari, Adel Ghenaiet〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The simulated pressure-time, recorded at several monitoring points through the components of a small Francis turbine, show that the rotor - stator interactions (RSI) cause strong pressure fluctuations and torque oscillations even for the best efficiency operating point (BEP). The pressure fluctuations frequency and the mode shape and their sequence are predicted. At the low discharge operating point the significant drop in the static pressure is distinguishable at the inlet of the runner. The amplitude of the dominant frequencies at the low discharge operating point are larger than at BEP, in addition to other captured frequencies related to the occurrence of the vortex rope in the draft tube. The pressure fluctuations occurring in the vaneless space tend to propagate beyond the runner outlet and are influenced by the interactions between the runner and the draft tube. At most unstable operating conditions the pressure pulses within the runner passages are mainly related to RSI and channel vortices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 134〈/p〉 〈p〉Author(s): Krishnadass Karthick, S. Suresh, Harjit Singh, Grashin C Joy, R. Dhanuskodi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal interface resistance of Thermoelectric Generator (TEG) plays a vital role in power production. Improving surface finish of contact surfaces, applying pressure between the contact surfaces and use of Thermal Interface Material (TIM) are few methods of reducing thermal resistance and thereby improving the efficiency of TEG. There is a need to evaluate the influence of these methods and use them optimally for TEG system. Experiments were carried out to study the influence of parameters such as thermal conductivity of TIM, contact pressure, surface roughness and heat source temperature on the voltage and power outputs from TEG. Experimental results are validated with simulations using mathematical heat transfer model and COMSOL〈sup〉TM〈/sup〉 Multiphysics numerical model. Appreciable agreement is seen between the experimental observations and model outputs. Experimental and model results indicate 0.6 W/mK as optimum thermal conductivity for TIM material. Hence, use of costly TIMs like MWCNT (Multi Wall Carbon Nano Tube) and copper nanoparticles may not be required for the selected application. The contact pressure and surface roughness have appreciable influence when air is used as TIM. These factors have insignificant influence for TIMs with higher thermal conductivity. Increase in heat source temperature increases voltage and power output of TEG.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Renewable Energy, Volume 134〈/p〉 〈p〉Author(s): Santiago Salamanca, Pilar Merchán, Antonio Adán, Emiliano Pérez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This paper presents an original method for the analysis of the geometric and optical properties of parabolic solar trough collectors using laser scanners and image processing techniques. The aim of the paper is to propose a methodology with which to automatically analyse geometric errors in the mirror and receiver, in addition to presenting an empirical assessment of one of the most important factors that determines the entire energy efficiency of solar plants, which is optical efficiency.〈/p〉 〈p〉The definition of 〈em〉canonical images〈/em〉 has allowed us to characterise a set of parameters that evaluates errors on both the surface of the parabolic reflector and regarding the orientation of the receiver. In this framework, energy efficiency is established in terms of two parameters, denominated as the 〈em〉interception index〈/em〉 and the 〈em〉concentration index〈/em〉.〈/p〉 〈p〉The proposed method has been tested on-site on real surfaces of parabolic solar trough collectors in an operating solar thermal plant. The results obtained are sufficiently accurate and reliable to be able to recommend that researchers and plants reproduce this method in this kind of installations.〈/p〉 〈/div〉 〈/div〉