ALBERT

Description: A permanent magnet linear generator for direct drive wave energy converters is a suitable power take-off system for ocean wave energy extraction, especially when coupled with a point absorbing buoy via a connection line. The performance of the linear generator is affected by the excursion of the translator along the stator. The optimal stroke is achieved when the midpoint of the oscillations coincides with the center of the stator. However, sea level changes due to, e.g., tides will shift these oscillations. This paper proposes a model able to detect the position of the translator from the generator output voltage. The algorithm will be integrated in the control system of a mechanical device that adjusts the length of the connection line in order to center the average position of the translator with the center of the stator. Thereby, the output power from the wave energy converter increases, and the mechanical stresses on the hull of the generator decrease. The results obtained by the model show good agreement with the experimental results from two linear generators, L2 and L3, deployed in the Lysekil wave energy research site, Sweden. The theoretical results differ from the experimental results by −4 mm for L2 and 21 mm for L3 with a standard deviation of 27 mm and 31 mm, respectively.

Description: RFID (Radio Frequency Identification) technology is widely used in industry but thus far has almost no applications for energy biomass logistics. A demonstration study was performed to build a real-time Web-based tracking system, denoted as RfIDER that uses RFID to manage energy biomass logistics. In the demonstration study, the functionality of this system was evaluated and further developed. The demonstration involved trucks carrying both composite and metal interchangeable containers with RFID tags mounted on them. Also, the productivity of all work phases in the transportation chain was examined and the readability of the RFID tags was evaluated. The demonstration study revealed that the RfIDER system enables following containers in real time through the supply chain and both storing and reading information on individual containers reliably, such as biomass owner, origin, destination, content, and quality. The RFID tags' readability was better with composite than metal containers. Potential benefits of the system demonstrated are real-time nature and accuracy of the data gathered and an opportunity to allocate and classify said data on the basis of customer needs. Possible logistical advantages include greater efficiency of unloading operations at the energy plant via use of existing information stored in the system.

Description: A transient analysis is performed in this paper for the wind turbines (WTs) struck by lightning. The equivalent circuits of blade, moving contact site, tower, and earth-termination system are built, respectively, and a set of analytic formulas are presented to evaluate their circuit parameters. By assembling the equivalent circuits of these separate parts, a complete model is set up for describing the lightning transient behavior of the WTs. Then, the transient responses can be obtained at different locations in the WT on the basis of the numerical solution to the network equations. In order to check the validity of the model, a laboratory experiment has been made on a reduced-scale WT. The model has also been applied to lightning transient analysis of an actual WT with a rated power of 2.5 MW.

Description: The alternate energy resources are replacing conventional energy sources for electricity production because of tremendously increasing environmental pollution and cost of fossil fuels. Wind power is one of the potential alternate energy resources and is being deployed actively. Wind power generation system comprises of wind turbine and electrical generator as essential parts interconnected through gear box. The conventional wind turbines are designed with adjustable blade pitch to regulate shaft speed of turbine or to withstand against heavy wind blows. In this paper, a technique for peak load sharing in the presence of utility supply using Pitch Frequency Control (PFC) is proposed for wind turbines. This technique has been simulated in MATLAB environment using Simulink. The simulation results show that PFC finds its applications with wind energy system having low speed axial flux synchronous generator as well as with the wind energy system with small gear ratio. This particular proposed PFC based control presents a cost effective technique for efficient peak load sharing and wind energy system free of power electronic converters.

Description: Precise forecasting of renewable energies such as solar and wind is becoming one of the very important concerns in developing modern electrical grids. Hence, establishing appropriate tools of weather forecasting with satisfactory accuracy becomes an essential preoccupation in today's changing power world. In this paper, an approach based on Principal Component Analysis (PCA) and Extreme Learning Machines (ELM) is proposed for the forecasting of time series. The PCA maps the data into a smaller subspace in which the components accounts for as much of the variability in the input space as possible. The variables extracted by the PCA are then introduced to the extreme learning machines, a learning algorithm much faster than the traditional gradient-based learning algorithms. The experiments carried out on three time series lead to: (i) The PCA as variable selection method shows a positive impact on the accuracy of the forecasting process. (ii) ELM model is significantly faster than Multi-Layer Perceptron Network, Radial Basis Function Networks, and Least Squares Support Vector Machines, while preserving the same accuracy level.

Description: Rapid and accurate load forecasting is essential for renewable yet highly stochastic power (such as wind and solar power) to be massively utilized in practice. While there are many load forecasting methods reported in the literature, most of which, however, do not literally guarantee the convergence of forecasting error. This paper proposes a new error correcting approach for load forecasting in power systems by using trajectory tracking stability theory. In principle, the proposed method is not an autonomous but heuristic correcting approach to assess and improve the results of other existing models. This method is able to ensure the convergence of forecasting error in theory and is independent of system model, making it more feasible and cost-effective for forecasting performance improvement. Simulation experiments confirm the effectiveness of the proposed method for multiple existing models and forecasting horizons.

Description: A two-cylinder, direct injection diesel engine was modified for a homogeneous charge compression ignition-direct injection (HCCI-DI) engine fueled with dimethyl ether. Effects of premixed ratio on HCCI-DI combustion characteristics were experimentally investigated. The results show that in HCCI-DI combustion, as premixed ratio Rp increases, the peak pressure increases and its phase advances gradually; the first peak of pressure rise rate increases and the second peak decreases, and their phase advances gradually. With the increase of Rp, the cool flame peak increases gradually, the peaks of premixed combustion and diffusion combustion decrease gradually. The in-cylinder pressure is decomposed using discrete wavelet transform, the details D1, D2, D3, D4, D5, and D6 are obtained. The relative energy value of pressure at D6, D5, and D4 decreases gradually. The same results are obtained at 0.32 MPa brake mean effective pressure (BMEP), 0.24 MPa BMEP, and 0.16 MPa BMEP. The combustion state plays an important role in determining wavelet relative energy distribution of in-cylinder pressure over details. With increases of Rp, the energy value of in-cylinder pressure at D6 increases gradually, but the energy value at D5 and D4 decreases. It transforms from at D4 and at D5, to at D6 with the increase of Rp.

Description: A generalized actuator disk (GAD) wind turbine parameterization designed for large-eddy simulation (LES) applications was implemented into the Weather Research and Forecasting (WRF) model. WRF-LES with the GAD model enables numerical investigation of the effects of an operating wind turbine on and interactions with a broad range of atmospheric boundary layer phenomena. Numerical simulations using WRF-LES with the GAD model were compared with measurements obtained from the Turbine Wake and Inflow Characterization Study (TWICS-2011), the goal of which was to measure both the inflow to and wake from a 2.3-MW wind turbine. Data from a meteorological tower and two light-detection and ranging (lidar) systems, one vertically profiling and another operated over a variety of scanning modes, were utilized to obtain forcing for the simulations, and to evaluate characteristics of the simulated wakes. Simulations produced wakes with physically consistent rotation and velocity deficits. Two surface heat flux values of 20 W m −2 and 100 W m −2 were used to examine the sensitivity of the simulated wakes to convective instability. Simulations using the smaller heat flux values showed good agreement with wake deficits observed during TWICS-2011, whereas those using the larger value showed enhanced spreading and more-rapid attenuation. This study demonstrates the utility of actuator models implemented within atmospheric LES to address a range of atmospheric science and engineering applications. Validated implementation of the GAD in a numerical weather prediction code such as WRF will enable a wide range of studies related to the interaction of wind turbines with the atmosphere and surface.

Description: Calcium borohydride, Ca(BH 4 ) 2 , one of the promising candidates for efficient hydrogen storage, has been synthesized successfully by the metathesis reaction between magnesium chloride and sodium borohydride in tetrahydrofuran in which the insoluble byproduct sodium chloride can be easily removed. And the hydrogen storage properties of its related Ca(BH 4 ) 2 -4LiNH 2 composite system with the presence of cobalt containing species as additives are systematically investigated. A doping of 5 wt. % CoCl 2 considerably decreases the dehydrogenation temperature of a mixture of Ca(BH 4 ) 2 -4LiNH 2 . More than 4.5 and 7 wt. % of hydrogen can be released at temperatures as low as ca. 165 and 178 °C, respectively. The effective catalytic species is determined to be cobalt particle which is formed on-site during ball milling process, having superior catalytic performance to cobalt powder as a catalyst. In addition, the results show that the amount of by-product NH 3 is less when dehydrogenated by volumetric release than by thermogravimetric analysis (TG), i.e., evolved NH 3 can react with borohydride for hydrogen release in closed reactor.

Description: In this communication, thermal performance of building integrated “Earth Air Tunnel Heat Exchanger” (EATHE) has been studied for a composite climate of Delhi. Mathematical model and building thermal simulation software (Energy Plus) are used for prediction of indoor air temperatures. The predicted results are validated through experimental results. Energy conservation potential both for heating and cooling of EATHE has been evaluated for winter and summer months in a specific year. Quantitative assessment of CO 2 mitigation has also been computed. It is observed that Coefficient of performance (COP) of EATHE is found between 6.3–13 during summer and 6.8–9.5 during winter season. The maximum drop in air temperature across the earth air tunnel is found to be 8.7 °C with air velocity of 2.69 m/s during peak summer and during winter season the room air temperature is raised by 5–7 °C. On the other hand, the system is capable of maintaining room temperature in the range of 27–30 °C during peak summer when outdoor temperature are in the range of 33–41 °C. EATHE integration with building can significantly reduce the electrical power consumption by 96.63 MWh annually, needed for space heating and cooling load. It is discovered from the study that this EATHE has potential of reducing global warming 8 by substantially mitigating CO 2 to the tune of 95 tonnes annually.

Description: The frequency control process and ensuring the security of supply in microgrids (MG) with high penetration of renewable energy sources demand the development of specific control systems and energy storage resources. This paper presents a three-phase battery energy storage system (BESS), designed to support the frequency in autonomous MG. Besides the basic functions, the proposed BESS includes enhanced features, which improves the MG frequency response. When placing the BESS near a consumer, which may also include small generators, the local power variations can be partially or totally compensated, thus relieving the MG of these perturbations. The proposed solution is experimentally evaluated within a laboratory MG prototype and with a 5 kW BESS.

Description: Application of micro-scale microbial fuel cells (MFCs) to power electronics is limited due to the high internal resistances associated with membranes. Laminar flow MFCs (LFMFCs) provide an advantage over conventional designs because the anode and the cathode are naturally separated due to the laminar flow regime that develops within the reactor, eliminating the need for membranes. However, our ability to fully harness the potential of LFMFC technology lags from a lack of in-depth understanding of anode/cathode analyte mixing and fundamental factors that maximize LFMFC's power-generating capabilities. We, therefore, investigated the anode colonization and respiration of the known exoelectrogenic bacterium, Geobacter sulfurreducens , in a micro-scale LFMFC. Current production was dependent on the location of the anode relative to the influent in continuous-flow operation, with the highest current density of 6.5  μ A/cm 2 recorded closest to the influent. Lateral diffusion of anode/cathode analytes, in addition to upstream substrate consumption, likely resulted in the observed differences in current production. As current increased, the number of bacterial cells on the anode measured using simultaneous microscopic observation, also increased. Although the current density obtained here was substantially lower than other micro-sized MFCs, these findings show that micro-scale LFMFCs adapted to microscopic observation can provide a unique tool for better understanding real-time anode colonization and overall reactor performance.

Description: A building integrated Borehole Heat Exchanger (BHE) has been designed and installed at Central Building Research Institute, Roorkee (29.87°N 77.88°E) India. The thermal performance and energy conservation potential (cooling potential) of installed BHE have been evaluated during summer months in the year 2013. The parametric study has also been done for its maximum performance. Quantitative assessment of CO 2 mitigation has also been computed. The constant BHE water temperature (approximately 25 °C) witnessed the transferring of heat from air to water and vice-versa. It is found that the air temperature is reduced by 8–13 °C during summer season at air velocity of 18.9 m/s from the inlet of the BHE (exit of blower), whereas outdoor temperature was recorded as 35–39 °C. This system is capable of maintaining room temperature between 26 and 30 °C during peak summer season. The cooling capacity is evaluated between 150 and 180 kW h. BHE integrated with building can significantly reduce the 39836.25 kW h of electrical power needed for space cooling load and it can reduce global warming by substantially mitigating the carbon-dioxide to the tune of 50.10 tonnes annually. During the parametric study, it is found that double U-tube, circular pipe with optimum pitch of 4 in. is needed to achieve higher performance from the BHE.

Description: Daily increasing demand of electrical energy and also recent developments in technology of distributed generations (DGs) have created special interest in using these units. On the other hand, capacitor insertion in the distribution feeders has been implemented by distribution companies for several years to reduce power loss and improve the voltage profile. Hence, according to the joint role of distributed generation units and capacitors, their optimal allocation will be influenced by each other. Therefore, in order to achieve the maximum benefits, this paper has discussed the optimal siting and sizing of DG resources and capacitors. One of the characteristics of the proposed method is that all technical and economical factors associated with installation of DGs and capacitors will be priced. For this purpose, all effective factors in optimal allocation and sizing of DG resources and capacitors are extracted and priced. For example, for the first time, the factor of voltage profile has been priced by the number of tapping. Using this approach, weighting the objective function parameters would be no more required. One of the other features of this paper is presenting an algorithm to determine the optimum number of DGs and capacitors. With this algorithm, power companies can find the optimum number of DGs and capacitors in the network they cover. The proposed method in this paper is tested on the 97-bus network of Bakhtar Regional Electrical Company in Iran Country.

Description: The Markovian properties within a wind turbine array boundary layer are explored for data taken in a wind tunnel containing a model wind turbine array. A stochastic analysis of the data is carried out using the mathematics of Markov processes. The data were obtained using hot-wire anemometry thus providing point velocity statistics. The theory of Markov process is applied to obtain a statistical description of longitudinal velocity increments inside the turbine wake. Comparison of two- and three-scale conditional probability density functions indicates the existence of Markovian properties in longitudinal velocity increments for scale differences larger than the Taylor microscale. This result is quantified by use of the Wilcoxon rank-sum test which verifies that this relationship holds independent of initial scale selection outside of the near-wake region behind a wind turbine. Furthermore, at the locations which demonstrate Markovian properties, there appears to be a well defined inertial subrange which follows Kolmogorov's −5/3 scaling behavior. The results show that directly behind the tips of the rotor and the hub, the complex turbulent interactions and large scale structures of the near-wake affect the Markovian nature of the field. The presence of a Markov process in the remaining locations leads to characterization of the development multiscale statistics of the wind turbine wakes using the most recent states of the flow.

Description: To make renewable Micro-Grid (MG) systems work as a sustainable set, one confronts a multi-objective, multi-constraint problem. To optimally operate these hybrid energy systems, one should consider the problems due to huge amount of raw data achieved through several measuring systems in different sections in a MG. In this paper, a new Smart Energy Management System (SEMS) is proposed and tested via simulation studies. The proposed SEMS performs some critical tasks such as data acquisition, data processing, and determining control signals for the MG. Two objective functions are defined for the SEMS to minimize the total operating cost and the net emission of the fossil fueled Distributed Generators with respect to some technical and reliability (Expected Energy Not Supplied index) constraints for the MG. The simulation results show a promising performance of the proposed SEMS for smart micro-grids.

Description: Modern horizontal axis wind turbine blades are long, slender, and flexible structures that can undergo considerable deformation, leading to blade failures (e.g., blade-tower collision). For this reason, it is important to estimate blade behaviors accurately when designing large-scale wind turbines. In this study, a numerical analysis considering blade torsional degree of freedom, geometric nonlinearity, and gravity was utilized to examine the effects of these factors on the aeroelastic blade behavior of a large-scale horizontal axis wind turbine. The results predicted that flapwise deflection is mainly affected by the torsional degree of freedom, which causes the blade bending deflections to couple to torsional deformation, thereby varying the aerodynamic loads through changes in the effective angle of attack. Edgewise deflection and torsional deformation are mostly influenced by the periodic gravitational force on the wind turbine blade.

Description: Improved power conversion efficiency (PCE) of flexible polymer bulk heterojunction solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C 61 -butyric acid methyl ester blends with a non-thermal annealing active layer have been obtained by using 1,2,4-trichlorobenzene as the solvent and 1,3,5-trichlorobenzene (135-TCB) as the additive. The influence of the solvent and additives on the performance and stability was investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), UV-vis and thermogravimetric analysis. The easily processed device using 135-TCB as additive on the ITO coated polyester substrate exhibits a PCE of ∼3.03% with Voc of 0.60 V, Jsc of 9.07 mA/cm 2 and fill factor of 55.7%, which is comparable to the device on the ITO glass substrate. AFM result revealed the enhanced performance is ascribed to the rough morphology of the active layer. So, larger interfacial area is formed. XRD measurement disclosed that the 135-TCB additive increases the crystallinity of P3HT. The accelerated heat aging decay curve showed the stability is also improved. The strategy of using the processing additive to control the morphology of flexible polymer solar cell without any thermal annealing is very attractive due to its simplicity and well suitable for future large scale production.

Description: In developing countries, though electrical energy has been recognized as a noteworthy input for their economic growth and societal development, nearly 2 × 10 9 people lack access to electrical energy use. Many national policies were designed to provide electric service to an entire population; nevertheless, all have encountered with significant barriers. Securing a passable electric service for isolated societies with small population and large distance from the main electricity grid has been proved to be a hard-hitting challenge to the energy policy strategists. To overcome the energy barriers and the energy scarcity of the secluded society, this paper proposes a sustainable, economic, and environmental friendly energy mix option with fossil-fuelled, wind, and solar energy systems as a curative solution.

Description: The main objective of the present study is to investigate the efficiency of seed sludge for the production of biogas from rice mill effluent using up flow anaerobic sludge blanket bioreactor. Response surface methodology coupled with three factors three level Box-Behnken response surface design was used to study the treatment process statistically. Effects of temperature, alkalinity dose, and flow rate on the chemical oxygen demand (COD) removal and biogas production were investigated and second order polynomial mathematical models were developed for the responses with high coefficient of determination values (R 2  〉 0.99). Analysis of variance was used to evaluate the adequacy of developed mathematical models and three dimensional response surface plots were constructed to study the interactive effects of process variables on the treatment efficiency. Optimum conditions were found to be temperature of 40 °C, alkalinity dose of 1.5 g CaCO 3 /l and wastewater flow rate of 6 l d −1 . Under these conditions 87% ofCOD removal and biogas production of 273 ml CH 4 /g COD were obtained.

Description: An improved tool for the shape qualification of parabolic trough mirror modules used in concentrated solar power plants was developed. The tool is based on the fringe reflection theory, in which sinusoidal fringe patterns are projected on a screen and their reflection over a specular surface is recorded by a camera. The observed distortions in the image are related directly to surface deviations from ideal geometry. Relevant aspects of the technique are its high spatial resolution (more than 1 × 10 6 points per mirror facet), short measurement time and easy setup. The developed tool (called FOCuS) is capable of calculating the local mirror slope deviations from its ideal design and the RMS value as a quality factor. Furthermore, the tool generates a file which can be loaded into CENER's TONATIUH ray tracing software, through a specially developed plug-in, for mirror modeling and intercept factor calculation with several tube absorber geometries.

Description: Low-concentration photovoltaic compound parabolic concentrators (PV-CPC) are a significant addition of solar cell application, especially in Building Integrated Photovoltaics, because it does not need a tracking system and can be installed in a stationary condition. However, higher concentrations correspond with the smaller half acceptance angle, which is a limitation but can be improved by a lens-walled structure. In this paper, to validate the rationale of this structure, a low-concentration PV-CPC using an acrylic lens-walled structure module was designed and fabricated with low-cost materials. The corresponding simulation was also performed with different materials to determine whether the factor that the truncation had a significant effect. The observed outcome implied that the low-concentration PV-CPC using an acrylic lens-walled structure has a larger half acceptance angle than the mirror CPC, and that a maximum optical efficiency of more than 80% can be achieved using Schott BK glass as the lens wall material. The lens-walled structure improved the angular acceptance of stationary low-concentration PV-CPC, providing a basis for further research.

Description: This paper presents a generalized optimal model for determining the location and rating of wind power generation in double auction competitive power market. The optimization technique has been used with an objective to maximizing the social welfare and profit to wind gencos company (WP-GENCO) while consider all system constraints. The performance of any electricity market is assessed by its impact on social welfare, which may be defined as “the difference of the benefit of the energy to society as measured by society's willingness to pay for its demand and the cost of energy.” Each distribution company (Disco) will pay an amount to independent system operator (ISO) for purchase the power and each generation company (Genco) will receive an amount from the ISO to sale the power. The amount to be paid by each Disco and amount to be received by each Genco has been determined by pay as bidding price approach. The social welfare has been then determined based on total payments and receipts. The proposed approach has been applied to modified IEEE 30-bus test system in which bidding at all generator buses and some load buses has been introduced.

Description: The paper discusses the “Clean Production” concept in which anthropogenic activities are compatible with ecosystems and essentially same as that of sustainable development. It is important for the eco-compatible biodiesel manufacturing that the production processes, product cycles, and consumption patterns contribute for human development and fulfils basic needs without degrading and disrupting the ecosystems. A Quantitative Assessment Model is proposed in this study to quantitatively assess the biodiesel production considering the scenarios of environmental, economic, and social aspects. The paper also suggests planning strategy so as to minimize the environmental, economic, and social degradation, and steps for implementing environmentally conscious design and manufacturing procedure.

Description: This paper presents modeling and simulation of the advanced photovoltaic (PV)/hydro based Hybrid Renewable Energy System (HRES) to electrify such isolated/remote areas, where grid accessibility is not possible. For 7.5 kW hydro generation system, a Self Excited Induction Generator (SEIG) with improved technique is used to optimize the utilization of hydro power. To achieve this aim, an uncontrolled bridge rectifier coupled with Hydro side Voltage Source Inverter is implemented for the SEIG based advanced hydro system. The PV system is configured by PV array, battery, DC/DC converter, maximum power point tracking controller, and PV side Voltage Source Inverter. A Constant Current Control scheme is developed in this paper to control active and reactive power flow and to synchronize hydro and PV systems. The proposed system uses fewer controlled switches, hence complexity of control has been reduced and system has higher efficiency and lower switching losses. The performance analysis of the HRES has been done to authenticate the existence of the system using the MATLAB software and results demonstrate that power quality of the proposed system is better and HRES is able to put into services.

Description: The Schottky barrier between the nanoporous TiO 2 /F–doped SnO 2 interface is extracted via experiment for the first time using two independent approaches. In the first approach, Ohmic contacts using Ti and Al on nanoporous TiO 2 film are made to facilitate temperature dependant IV measurements. An extracted barrier height of ∼0.6 eV at the TiO 2 /F–doped SnO 2 assuming a theoretical value of the Richardson's constant is obtained. The barrier height is incorrectly deduced to be 0.31 eV if a Richardson constant extracted from experimental data fitted to thermionic emission theory is employed. In the second approach, a voltage dependent barrier height of 0.53 eV at T = 285 K is extracted from the dark current characteristics of a dye sensitized solar cell contacted to the nanoporous TiO 2 film via the dye, electrolyte as normal. The analysis shows that in dye sensitized solar cell, the impact of such a barrier is dominant only beyond open circuit voltage conditions in the range above 1–1.2 V.

Description: We report on the influence of the substrate temperature during the 2nd and 3rd stage of the Cu(In,Ga)Se 2 3-stage co-evaporation process on the in-depth Ga and In concentrations and correlate these with the solar cell parameters and external quantum efficiency of soda-lime glass/Mo/CIGS/CdS/i-ZnO/ZnO:Al devices. An increased homogenization of the [Ga]/[III] fraction ([III] refers to the total concentration of the group 3 elements Ga and In) with temperature is found. In the investigated temperature range, the highest efficiency was measured for the lowest temperature and the steepest Ga-profile. The tendency of the short-circuit current density matches well with the notch-deepness. Surprisingly, the open-circuit voltage decreases for higher substrate temperatures, even though the Ga-concentration in the space-charge region increases. We propose back-grading variations and reduced back-interface recombination to explain this observation. For the highest of the tested temperatures of 540 °C, a homogenization of the Ga and In concentrations close to the surface is found. We explain this by the appearance of a liquid Cu 2-x Se phase at the end of stage 2 for this high temperature. Break-off experiments at this point are conducted and reveal morphological and compositional lateral inhomogeneities for T sub  

Description: Thin films of Cu 2 ZnSnS 4 (CZTS) were prepared by sulfurization of multilayered precursors of ZnS, Cu, and Sn, changing the relative amounts to obtain CZTS layers with different compositions. X-Ray Diffraction (XRD), Energy Dispersive X-Ray spectroscopy, and SEM were used for structural, compositional, and morphological analyses, respectively. XRD quantitative phase analysis provides the amount of spurious phases and information on Sn-site occupancy. The optical properties were investigated by spectrophotometric measurements and Photothermal Deflection Spectroscopy. These films show a clear dependence of the optical and microstructural properties on the tin content. As the tin content increases we found: (i) an increase in both crystalline domain and grain size, (ii) an abrupt increase of the energy gap of about 150 meV, from 1.48 to 1.63 eV, and (iii) a decrease of sub-gap absorption up to two orders of magnitude. The results are interpreted assuming the formation of additional defects as the tin content is reduced.

Description: Sodium addition is necessary to reach high efficiencies with Cu(In,Ga)Se 2 (CIGS) solar cells on metallic substrates. This can be achieved using DC-sputtered multilayer Mo back contacts including a sodium-doped layer (Mo:Na). In this study, 450 nm-thick Mo:Na layers were sputter-deposited on Ti foils using a working pressure ranging from 3.4 mTorr to 30 mTorr, and capped with 100 nm-thick, dense, pure Mo layers. The deposition pressure of the Mo:Na layers strongly affected their electrical resistance, optical reflectance, morphology, and crystal quality. The top Mo layer allowed controlling the electrical and optical properties of the back contact, but its own morphology was affected by the structure of the underlying Mo:Na layer. The Na concentration in the CIGS layer varied as a function of the deposition pressure of the Mo:Na layer, inducing changes in the absorber grain size and Ga distribution, as well as in the carrier density. Absolute conversion efficiency improvements over 3% were obtained using the sodium-doped back contacts on Ti foils, leading to a performance which was equivalent to the soda-lime glass reference.

Description: Detailed experimental studies on procedures of reducing “On-stove time” and cooking with minimum Energy (Heat) using new energy efficient cooking techniques have been carried out. The total minimum amount of heat, Q m (after subtracting radiation losses), to be delivered to the pot, the sensible heat required for cooking, h s , and on-stove time t 1 required to cook 1 kg of dry rice, using a new technique (Technique I) of cooking with a stove of effective power, P eff , 626 ± 10 W are found as 560 ± 6 kJ, 465 ± 5 kJ, and 911 ± 10 s, respectively; while conventional method with pressure cooker (Technique II) required Q m  = 824 ± 10 kJ heat and 1357 ± 16 s on-stove time. The corresponding energy and time without a pressure cooker (Technique III) were 1.5 MJ and 2640 s, respectively. When compared with other published works, our method gives the lowest energy to cook 1 kg of dry rice. The efficiencies of the cooking method for different techniques are evaluated. The Clean Development Mechanism potentials of the new cooking method are also evaluated. The results obtained are expected to help develop new cooking apparatus to cook with the lowest amount of energy and thus conserve food nutrient energy and protect environment by minimizing CO 2 and other toxic emissions associated with all kinds of stoves/ovens. Discussion is made how to apply Technique I in solar cooker to reduce the cooking time.

Description: Tropical rivers have high annual discharges optimal for hydropower and irrigation development. The Mekong River is one of the largest tropical river systems, supporting a unique mega-diverse fish community. Fish are an important commodity in the Mekong, contributing a large proportion of calcium, protein, and essential nutrients to the diet of the local people and providing a critical source of income for rural households. Many of these fish migrate not only upstream and downstream within main-channel habitats but also laterally into highly productive floodplain habitat to both feed and spawn. Most work to date has focused on providing for upstream fish passage, but downstream movement is an equally important process to protect. Expansion of hydropower and irrigation weirs can disrupt downstream migrations and it is important to ensure that passage through regulators or mini hydro systems is not harmful or fatal. Many new infrastructure projects (

Description: Doubly fed induction generator (DFIG) under grid fault has increasingly gained attention among researchers for the better protection and control of power system. However, existing studies which focus on the single DFIG are incomplete, because other DFIGs can significantly affect the transient process of DFIG in the wind farm. Thus, this paper investigates the correlation among the transient characteristics of DFIGs when a three-phase fault occurs in power grids. A vector model of a DFIG is built with consideration for the excitation regulation. Transient processes of the DFIG when wind farm contains different numbers of DFIGs are mathematically deduced by dividing the fault process into two periods according to converter regulation. The analytic expressions indicate the relationship between the transient electrical variables of a DFIG and the number of DFIGs is proposed to acquire the varying pattern of the correlation. The correlation phenomenon is verified both through analysis and simulation, which provide positive implications for the operation of wind power integrated systems.

Description: Awareness of energy savings and carbon reduction is gradually on the rise throughout the world, and in addition to lowering wasted energy use, countries are putting forth great efforts to develop renewable energies. Among these energies, the greatest growth is in solar photovoltaic. While the cross-strait (China and Taiwan) solar photovoltaic industry makes up over half of the global solar photovoltaic market share, its size can certainly not be underestimated, and thus its operating performance is very important. In this research, we take 2007–2012 cross-strait solar photovoltaic industry manufacturers as the research objectives in order to measure their operating performances, using the meta frontier production function by data envelopment analysis. The empirical results show that although in the six observation years Taiwan solar photovoltaic firms are better than China counterparts, the gap between them is getting smaller and smaller. Returns to scale analysis reveal that China solar photovoltaic firms still have room for improvement to adjust the scale to optimal level.

Description: Metal oxide semiconductor photoanodes with wide band gap and higher electron mobility are essential for efficient charge injection and transportation in dye sensitized solar cells (DSSCs). In the present study, tin oxide (SnO 2 ) was used as alternative semiconductor photoanode to the usually used TiO 2 in DSSC. The effect of dye adsorption time (DAT) on performance of Eosin-Y sensitized SnO 2 DSSC was studied. It was observed that the open circuit voltage (V oc ), fill factor, and short-circuit photocurrent density (J sc ) vary prominently with the DAT. The value of V oc was found to be 363 mV with 24 h DAT even if with low cost Eosin-Y dye and which was comparable to those obtained with costly Ru-based dyes.

Description: Generation expansion planning requires simulating the medium term power market. This can be done based on electricity price signals in the power market. The market clearing price is one of the most important factors to determine the incremental rate of private investor's profit. When calculating this parameter, the planners encounter greater uncertainties in a restructured power market than in a centralized market. This can be critical when renewable energies participate in this type of electricity market. In this study, the scenario based method is used to model a wind power plant in the restructured power market. The hourly output of the wind turbine generators is simulated based on a hybrid Auto Regressive and Moving Average-Monte Carlo method. Each scenario of the wind power plant as well as its occurrence probability is determined based on a data mining technique. Then, a new comprehensive model for the restructured power market is proposed to maximize the profit of investors as well as to determine the market clearing price by considering stochastic and rational uncertainties. The stochastic uncertainties include the demand and fuel price that are modelled by using the Monte-Carlo method. The Nash equilibrium in the rational uncertainty as a strategic behaviour of players in the power market is determined by using the Cournot game. The effect of the CO 2 tax rate and the bilateral contract are investigated in this study. Finally, the model is implemented in a test power market. According to the findings, this model can be used as a robust and comprehensive model to determine the market clearing price which can be applied for capacity expansion planning.

Description: Large eddy simulations of wind farms are performed to study the effects of wind turbine row alignment with respect to the incoming flow direction. Various wind farms with fixed stream-wise spacing (7.85 rotor diameters) and varying lateral displacements and span-wise turbine spacings are considered, for a fixed inflow direction. Simulations show that, contrary to common belief, a perfectly staggered (checker-board) configuration does not necessarily give the highest average power output. Instead, the highest mean wind farm power output is found to depend on several factors, the most important one being the alignment that leads to minimization of wake effects from turbines in several upstream rows. This alignment typically occurs at significantly smaller angles than those corresponding to perfect staggering. The observed trends have implications for wind farm designs, especially in sites with a well-defined prevailing wind direction.

Description: The power output of a wind turbine depends on the aerodynamic and geometrical characteristic of its airfoils, and therefore, the proper airfoil design for wind turbine blades is highly important. Furthermore, due to the usage of small wind turbines within city limits, the emitted noise is also a major issue. In the present work, “XFoil” and “NAFNoise” programs were used for flow analysis around blade cross sections (airfoils) and predicting the corresponding noise emission, respectively. Multi-objective optimization was carried out for maximizing the airfoil lift-to-drag ratio (C L /C D ) and minimizing the sound pressure level. With two above objective functions and by defining decision variables along with introducing physical and engineering constraints, genetic algorithm method was applied for optimization process. Moreover, ‘Fuzzy Bellman-Zadeh’ decision-making method was applied for selecting final optimal point from Pareto front. The results of this new method of airfoil shape analysis at various wind velocities showed about 26% average increase in C L /C D and 1.11% average decrease in noise emission in comparison with that for typical highly used S822 airfoil in small wind turbines.

Description: The main objective of this study is to develop single location appropriate models for the estimation of the monthly average daily global and diffuse horizontal solar radiation for Brasov, Romania. The study focuses particularly on models based on the sunshine duration and clearness index. The data used for the calibration of the models were collected during a period of 4 yr, between November 2008 and October 2012, at the Transilvania University of Brasov. The testing and validation of the models was carried out using data from the online SoDa database for Brasov for the year 2005. Different statistical error tests were applied to evaluate the accuracy of the models. The predicted values are also compared with values from three other known models concerning the global and diffuse solar radiation. A new mixed model was developed for the estimation of monthly average daily global horizontal solar radiation. The data processing was performed by means of a real-time interface developed with LabVIEW graphical programming language. The parameters taken into account were the relative sunshine, the clearness index, the extraterrestrial radiation, the latitude and the longitude. The methodology is simple and effective and may be applied for any region. Its effectiveness was proven through comparison with global models.

Description: In this paper, the wind turbine positioning problem is discussed. Binary-real coding method that combines binary coding method with real coding method is proposed. Wind turbine layout is optimized based on the linear wake model and genetic algorithm, with the target of minimizing the cost per unit power output or maximizing the profit of wind farm. Turbine power curve model with power control mechanisms is used and Weibull distribution is employed to describe the wind conditions. Two cases with simple models and a case with realistic models are used to test the present method. The results show that the new coding method inherits the advantages of both methods. The positions and the number of turbines are adjusted in the evolution process. The proposed coding method obtains the best number of wind turbines and the optimized layouts. It is an effective solution strategy for wind turbine positioning problem.

Description: In this paper, a mathematical model is used to determine the solar radiation incident on an inclined surface and the optimum slope angles for each month, season, and year are calculated for solar hybrid collectors. We recommend on how the collected energy can be increased by varying the tilt angle. First, we esteem the global solar radiation on a horizontal surface of a thermal photovoltaic hybrid collector (PVT) for a clear sky. The data set of the solar radiation at Ghardaïa (Algeria) measured during 2013 was used to analyze the models of global solar radiation estimation. The models of performance are evaluated by using the coefficient of correlation (R 2 ), the absolute average error skew (mean absolute error, MABE), average quadratic error (mean square error RMSE), the percentage of the average error (MPE), and the percentage of average absolute error. Then the anisotropic and isotropic models that provide the most accurate estimation of the total solar radiation has been used to determine the optimum collector slope. Particle swarm optimization method was applied to obtain the tilt angle setting of the tilt angle of PVT collector. The objective was to improve the efficiency of PVT collector. The results show that these models used are very well designed. The coefficient of correlation (R 2 ) varies from 0. 90 to 0. 99. For the percentage of errors of prediction (MABE and RMSE) lowered by 0.1, it is observed also that the angle of inclination of PVT collector takes different values during the year and that the collector received more solar energy compared to collector without optimal angle.

Description: This is the second part of the assessment of primary energy conversions of oscillating water columns (OWCs) wave energy converters. In the first part of the research work, the hydrodynamic performance of OWC wave energy converter has been extensively examined, targeting on a reliable numerical assessment method. In this part of the research work, the application of the air turbine power take-off (PTO) to the OWC device leads to a coupled model of the hydrodynamics and thermodynamics of the OWC wave energy converters, in a manner that under the wave excitation, the varying air volume due to the internal water surface motion creates a reciprocating chamber pressure (alternative positive and negative chamber pressure), whilst the chamber pressure, in turn, modifies the motions of the device and the internal water surface. To do this, the thermodynamics of the air chamber is first examined and applied by including the air compressibility in the oscillating water columns for different types of the air turbine PTOs. The developed thermodynamics is then coupled with the hydrodynamics of the OWC wave energy converters. This proposed assessment method is then applied to two generic OWC wave energy converters (one bottom fixed and another floating), and the numerical results are compared to the experimental results. From the comparison to the model test data, it can be seen that this numerical method is capable of assessing the primary energy conversion for the oscillating water column wave energy converters.

Description: This paper presents a risk-based decision-making framework for the Distributed Generation (DG)-owning retailer to determine the optimal participation level in the forward and the day-ahead electricity markets, as well as the optimal scheduling of DG units. The energy price in the day-ahead market is very volatile and varies every hour. Also, unpredicted failures of DG units may impose a great financial loss on the retailer. Therefore, the retailer has to evaluate the effects of uncertain parameters to hedge the financial loss. In this paper, the financial risk associated with the uncertain prices is evaluated using the chance constraint optimization method. The normal density function is applied to model the probabilistic realizations of uncertain prices, and scenarios are generated via the scenario tree technique. Moreover, the availability of generation units is modeled by the availability probability. The proposed risk-based framework allows the retailer to determine the optimal strategy at the given risk level. The objective-function of the presented model is based on maximizing the expected profit in a way that ensures the specific profit constraint will be satisfied at the operation period with a defined probability. The performance and efficiency of the presented decision-making framework are analyzed on the sample DG-owning retailer, and the optimal framework is simulated under different risk levels.

Description: Flexible Cu 2 ZnSnS 4 (CZTS) thin films are more advantageous than those on rigid glass substrates. In this study, vacuum-based magnetron sputtering was utilized to fabricate CZTS thin films on flexible polyimide substrates. Zn/Sn/Cu precursors were sputtered and then sulfurized. The influences of sulfurization temperature on the structural, compositional, morphological, electrical, and optical properties of the fabricated thin films were analyzed. The experimental results show that the CZTS structures form on the polyimide substrates after sulfurization. The crystallinity of CZTS enhances and the secondary phases in the thin films decrease with increasing sulfurization temperature. Single-phase CZTS thin films are obtained for sulfurization temperatures reaching 450 °C. The compositions of the fabricated thin films are Cu-poor and Zn-rich. The fabricated CZTS thin films show p-type conductivity. The direct optical band gaps of the thin films range from 1.51 eV to 1.55 eV. The absorption coefficients of these films are larger than 1 × 10 4  cm −1 above the band gap edge. The experimental results reveal the feasibility of the deposition of CZTS thin films on polyimide substrates by vacuum-based methods. The fabricated thin films can suitably function as absorbers for solar cell applications.

Description: The main objective of this study is to develop single location appropriate models for the estimation of the monthly average daily global and diffuse horizontal solar radiation for Brasov, Romania. The study focuses particularly on models based on the sunshine duration and clearness index. The data used for the calibration of the models were collected during a period of 4 yr, between November 2008 and October 2012, at the Transilvania University of Brasov. The testing and validation of the models was carried out using data from the online SoDa database for Brasov for the year 2005. Different statistical error tests were applied to evaluate the accuracy of the models. The predicted values are also compared with values from three other known models concerning the global and diffuse solar radiation. A new mixed model was developed for the estimation of monthly average daily global horizontal solar radiation. The data processing was performed by means of a real-time interface developed with LabVIEW graphical programming language. The parameters taken into account were the relative sunshine, the clearness index, the extraterrestrial radiation, the latitude and the longitude. The methodology is simple and effective and may be applied for any region. Its effectiveness was proven through comparison with global models.

Description: The power output of a wind turbine depends on the aerodynamic and geometrical characteristic of its airfoils, and therefore, the proper airfoil design for wind turbine blades is highly important. Furthermore, due to the usage of small wind turbines within city limits, the emitted noise is also a major issue. In the present work, “XFoil” and “NAFNoise” programs were used for flow analysis around blade cross sections (airfoils) and predicting the corresponding noise emission, respectively. Multi-objective optimization was carried out for maximizing the airfoil lift-to-drag ratio (C L /C D ) and minimizing the sound pressure level. With two above objective functions and by defining decision variables along with introducing physical and engineering constraints, genetic algorithm method was applied for optimization process. Moreover, ‘Fuzzy Bellman-Zadeh’ decision-making method was applied for selecting final optimal point from Pareto front. The results of this new method of airfoil shape analysis at various wind velocities showed about 26% average increase in C L /C D and 1.11% average decrease in noise emission in comparison with that for typical highly used S822 airfoil in small wind turbines.

Description: An offshore wind turbine in shallow water is installed by a self-elevated mobile unit that is usually referred to as a jack-up barge or jack-up vessel. The jack-up vessel consists of a buoyant platform together with independent legs that can position the vessel above the water, thereby reducing external loadings for a safe operation condition. The retrieval process for the jack-up legs can be very difficult due to the high extraction resistance caused by soft soil. In soft clay, high suction force can develop around the spudcan attached at the end of the jack-up legs. Therefore, a jetting system is required to break the suction in order to pull out the legs. It is important to design the jetting system with an optimized piping arrangement to allow the easy operation. Various factors must be considered in the design of the jetting piping system since the level of embedment, type of soil, and pipe sizes and locations can affect the performance of the system. In this paper, we present the characteristics of west coast geological features by subsea geological survey and the design of jetting system that was analyzed using pipe flow analysis program.

Description: With the increased awareness on excessive energy consumption, increasing fuel cost and negative environmental impact (ozone depletion and global warming) of the major heat generation systems and processes, the ability of heat pumps to generate high temperature with very efficient use of energy and minimal environmental impact has gained lots of awareness over the years. Some domestic and most industrial heating and refrigeration applications demand very high temperature lifts. Single-stage cycles do not practically support these applications since their performance and reliability decrease greatly. High temperature generation can be successfully executed through the use of cascade heat pump. This study analyzes the effects of compressor speed and electronic expansion valve (EEV) opening on the performance of the cascade heat pump in heating mode. The rate of increase of capacity with high-stage (HS) EEV opening at higher HS compressor speed is larger than it at high low-stage (LS) compressor speed. The slope of the capacity with the HS EEV opening was much steeper at small opening range than that at large opening range. When the LS compressor speed increased, the maximum Coefficient of Performance (COP) occurred at larger HS EEV opening than the standard opening. The COP variation at the range of low HS compressor speed had smaller dependency on the LS EEV opening than that at the range of high HS compressor speed.

Description: In this paper, a new approach to model the graphene-based silicon nanowires Schottky junction (SiNWs/G) solar cells taking into account Shockley-Read-Hall, Auger, radiative and surface recombinations is presented. The model results show that the performance of the SiNWs/G solar cells is much better than those of bulk Si/G counterpart solar cells. Then, a particular attention is paid to the effects of the number of graphene layers on the performance of the n- and p-type SiNWs/G solar cells. It is found that the performance of p-type SiNWs/G is more efficient than n-type SiNWs/G solar cell for the monolayer and bilayer graphene. Furthermore, the p-SiNWs/G solar cell parameters as functions of the temperature, doping concentration, and the SiNWs density and filling ratio are investigated. A comparison of our calculated results with published experimental data is shown to be in good agreement.

Description: Most renewable energy technologies suffer from an intermittent characteristic due to the diurnal and seasonal patterns of the natural resources needed for power generation; therefore, a complementary energy storage system must be considered. The pumped hydropower plant is a suitable alternative to consider as an energy storage device for hybrid systems. The hybrid optimization model for electric renewables (HOMER) optimization model is widely used around the globe for designing, comparing, or evaluating the performance of hybrid power systems, but it does not include an explicit component to model a pumped hydropower facility. This paper describes a method for representing a pumped hydropower plant by creating an equivalent battery in HOMER, and the procedure was accompanied by a detailed example. An additional example of a wind-hydro hybrid power system with controlled parameters is presented to validate the method. The results support that the procedure explained in this paper adequately represents the pumped hydropower plant as an equivalent battery.

Description: Because of the maturity of its technology, small scale hydropower generation is one of the main energy sources to be considered to provide electricity to areas far from the national grid. Very often, because of the economic limitations of the communities that can be supplied with electricity, these projects are unappealing from the entrepreneur's point of view; however, they can have such a great positive impact on the life of these communities, with little impact on the environment, that they may well justify subsidies for their construction. This paper describes a mathematical model that combines multicriteria analysis and a knapsack problem formulation for optimizing the distribution of limited financial resources among several options available of hydropower projects with a stochastic behavior in their initial cost. The test data were obtained mainly from 14 prefeasibility studies of sites in rural Nicaragua with potential for small hydropower. Five scenarios are presented, assessing the impact of multicriteria and different subsidy conditions or economic efficiency requirements. The results indicate that the presented method is suitable to be used for an efficient distribution of limited monetary resources for funding small hydropower projects, and, therefore, can be a useful tool in decision making process. The proposed method can be adapted for application to projects based on other forms of renewable energy, and can also be adapted for prioritization of projects based on different energy resources.

Description: Catalytic performance of palladium supported on activated carbons and mesoporous aluminosilicate Al-SBA-15 were investigated at 300 °C under 8 MPa H 2 for hydrotreating of bio-oil model compounds, including phenol, anisole, and furfural. With Pd/C catalysts, phenol, anisole, and furfural have been mainly hydrogenated into cyclohexanol, 1-methoxycyclohexane and (tetrahydro-furan-2-yl)-methanol, respectively. Pd/C shows high hydrogenation activity, but poor deoxygenation ability. Differently, in the presence of Pd/Al-SBA-15, the main hydrotreating products of phenol, anisole, and furfural are cyclohexane, cyclohexane, and tetrahydropyran. The high hydrodeoxygenation activity of Pd/Al-SBA-15 is due to the synergistic effect of the noble metal, which has high hydrogenation ability and the support, which has acidic property, high surface area, and large pore size.

Description: In this paper, a mathematical model is used to determine the solar radiation incident on an inclined surface and the optimum slope angles for each month, season, and year are calculated for solar hybrid collectors. We recommend on how the collected energy can be increased by varying the tilt angle. First, we esteem the global solar radiation on a horizontal surface of a thermal photovoltaic hybrid collector (PVT) for a clear sky. The data set of the solar radiation at Ghardaïa (Algeria) measured during 2013 was used to analyze the models of global solar radiation estimation. The models of performance are evaluated by using the coefficient of correlation (R 2 ), the absolute average error skew (mean absolute error, MABE), average quadratic error (mean square error RMSE), the percentage of the average error (MPE), and the percentage of average absolute error. Then the anisotropic and isotropic models that provide the most accurate estimation of the total solar radiation has been used to determine the optimum collector slope. Particle swarm optimization method was applied to obtain the tilt angle setting of the tilt angle of PVT collector. The objective was to improve the efficiency of PVT collector. The results show that these models used are very well designed. The coefficient of correlation (R 2 ) varies from 0. 90 to 0. 99. For the percentage of errors of prediction (MABE and RMSE) lowered by 0.1, it is observed also that the angle of inclination of PVT collector takes different values during the year and that the collector received more solar energy compared to collector without optimal angle.

Description: A floating Tension Leg Platform (TLP) wind turbine was constructed at scale 1/200 and its dynamic response was analysed experimentally in co-directional wind and waves. The wind turbine was Froude scaled and a new rotor was designed to yield maximum power and Froude scaled thrust at the low model Reynolds number. Physical limitations due to the large scaling ratio further meant that some structural adjustments were necessary. Nacelle and floater accelerations were measured by means of two accelerometers. The TLP was moored with four different tendon configurations and exposed to different constant wind speeds and irregular sea states as well as a range of regular waves. It was found that an increase in wind speed reduces the wave-induced floater motion but causes slightly larger nacelle displacements. Further, the orientation of the spokes relative to the direction of wind and waves influences the pitch stiffness and thereby the nacelle displacements. Inclining the tendons towards the wind turbine reduces the nacelle displacements significantly and reduces the occurrence of slack tendons, but increases the inline tilt-motion of the rotor. Application of a very stiff mooring configuration increases the occurrence of slack tendons and the magnitude of the pitch accelerations. In a robust commercial design, however, slack tendons must be avoided. The experiments demonstrate the ability of the wind turbine model and the experimental setup to give insight to the dynamic characteristics of floating TLP wind turbines.

Description: Occurrence of liquefaction in saturated sandy deposits under structure foundation can cause a wide range of structural damages from minor settlement to general failure because of bearing capacity loss. By comparing traditional foundations for offshore wind turbines, the soil inside and underneath the composite bucket foundation is subjected to the overburden pressure from the foundation self-weight and constrained by a half-closed bucket skirt. The objective of this paper is to clarify the effects of the soil-foundation interaction on the soil liquefaction resistance around the skirt and under the foundation. The dynamic response of the composite bucket foundation during earthquake, including coupled soil mode of porous media, is calculated using the ADINA finite-element program. A typical configuration of composite bucket foundation is used for the analysis, and two earthquake waves (peak ground accelerations of 0.035 g and 0.22 g) are applied as the base acceleration. The results show that the composite bucket foundation exhibited good resistance to seismic action by improving the anti-liquefaction capacity of the soil inside and under the foundation because of the overburden pressure of the self-weight and the constraint effect of the skirt.

Description: This study presents a thorough methodology for wind park design and micro-siting. It encompasses all aspects of wind project development and prefeasibility analysis. This approach uses the long-term wind data taken from on site measurements. Collected data are analyzed statistically. Then, wind resources are estimated and a choice of the best fitted wind turbines is performed. An optimal layout for wind turbines is proposed using the Windstation and 3DEM software. The main contribution of this paper is to evaluate the amount of accuracy given by this methodology in terms of predicting the future annual energy production of wind projects. To achieve this objective, the methodology was applied to a specific site which already contains an installed wind park. The test case wind farm is located in the north-east of Tunisia. The evaluation is performed by comparing the estimated energy production with real-time operation database of the wind park. Finally, the paper discusses the prospects of wind farm upgrading in order to make better use of the local wind resource.

Description: A recently developed in-house computational fluid dynamics (CFD) code is used to simulate an H-Darrieus wind turbine. Aerodynamic performance of the simulated Darrieus turbine having different number of blades and turbine solidity is analyzed and compared for different tip speed ratios. As expected, the power coefficient of the simulated Darrieus turbine increases with the increase of tip speed ratio until a maximum is reached. However, the power coefficient then decreases with further increases in the tip speed ratio. The calculated power curve is in good agreement with experimental results. The results obtained suggest that this developed CFD code can accurately predict the aerodynamic characteristics of an H-Darrieus turbine. In addition, it is found that the solidity has considerable influence on the power coefficient of the simulated turbine in the present work. The smaller the solidity, the higher will be the optimal tip speed ratio and the wider will be the range of tip speed ratios at which the H-Darrieus turbine remains high power coefficient. If solidity is very low, the performance of a 2-bladed Darrieus turbine is obviously better than that of turbines with 3 and 4 blades. For moderate to high solidity, the power coefficients of the 2-bladed Darrieus wind turbine are similar to those of the 3-bladed turbine and are higher than those of the 4-bladed turbine. Moreover, the power coefficient increases with increasing solidity at low tip speed ratios. When the tip speed ratio is close to the optimum value, the power coefficient initially increases and then decreases with the increase of solidity. At high tip speed ratio, the power coefficient decreases with increasing solidity. An in-depth investigation is also conducted on the findings observed in this study and presented in Part 2 of this work, in which the mechanism of the effect of solidity on power coefficient has been explored based on the vortex structure of the flow field with the aid of this self-developed CFD code.

Description: The traditional influence coefficient dynamic balancing method for multi-rotor series shafting, such as turbine-generator sets, gas turbines, compressor trains, and others, usually needs to startup many times using trial weights along the rotor. Based on finite element model analysis for the multi-rotor series shafting, a virtual dynamic balancing methodology which only needs to collect data of vibration response at operating speed without trial weights is developed in this paper. According to shafting structure and operating parameters, the dynamic finite element model was built by using rotor dynamics theory and finite element simulation technology. The shafting dynamic characteristics and weighted influence coefficient matrix can be gotten by exciting virtual unbalance force on the balance place correspondingly. The effectiveness and flexibility of the proposed method have been illustrated by solving a shafting dynamic balancing example with no trial weights requirements. It is believed that the new methods developed in this work will help in reducing the time and cost of the equipment manufacturer or field dynamic balancing procedures.

Description: This study used the meteorological data of 11 cities to calculate the spatial distribution and seasonal variation of the effective wind and solar energy along the coastal area of Bohai Bay, China. The results show that the effective wind energy decreases with an increased distance from the sea within a 120 km range of the sea; the maximum proportion of the effective wind energy is in the spring, and the minimum is in August. In addition to the effect of latitude, the spatial distribution of solar energy is also related to the proportion of sunlight. The solar energy allocation each month was consistently higher than the effective wind energy in the study area, it comes to maximum in June and minimum in December. Coupling the utilization of wind and solar energy not only extends the utilization time but it can also improve the guarantee rate of clean energy. The gradation of wind and solar energy's combined guarantee rate is greatest in May, followed by June, April, March, and July; the combined energy supply in other months is lower and varies little. The spring and summer months, which have a high proportion of combined wind and solar energy, require the most electricity for agricultural production in the study area. Thus, the supply and demand of energy correspond well and great potential exists for the comprehensive utilization and development of wind and solar energy in the study region.

Description: Security risk assessment difficulties brought about by uncertainties can be solved by probabilistic power flow. A security risk assessment scheme of the power system using fast probabilistic power flow is proposed in this paper. The scheme applied probabilistic power flow on fast decoupled power flow model, considering multi-scenario of wind power and static characteristics of power systems, gaining the probabilistic distribution information of each desired variable by improved Von Mises method based on cumulants. Besides voltages and branch flows, the scheme can also obtain the distribution of frequency to assess the power system completely, which is not concerned in conventional probabilistic power flow calculation. The proposed algorithm was realized by programming based on Matpower 4.0. The examples executed on IEEE RTS-24 system demonstrate the rapidity, validity, and prospect for online application of the proposed scheme.

Description: In this paper, the wind turbine positioning problem is discussed. Binary-real coding method that combines binary coding method with real coding method is proposed. Wind turbine layout is optimized based on the linear wake model and genetic algorithm, with the target of minimizing the cost per unit power output or maximizing the profit of wind farm. Turbine power curve model with power control mechanisms is used and Weibull distribution is employed to describe the wind conditions. Two cases with simple models and a case with realistic models are used to test the present method. The results show that the new coding method inherits the advantages of both methods. The positions and the number of turbines are adjusted in the evolution process. The proposed coding method obtains the best number of wind turbines and the optimized layouts. It is an effective solution strategy for wind turbine positioning problem.

Description: Dhaka, the capital city of Bangladesh, is one of the fastest growing cities in Southern Asia, having population of more than 13 million, and is expected to accommodate more than 20 million by 2025. This growth has been accompanied by the growth of urban slums and the subsequent challenges to access basic urban services like water, sanitation, clean energy, and transport for the urban poor. Despite its importance for basic survival, electricity supply is not recognized as a basic urban service, as a result of which, the poverty alleviation and basic infrastructure provision programs have not addressed this issue completely. On the basis of a stakeholder interaction approach, following a set of logically sequenced questions to assess the availability, accessibility, affordability, reliability and continuity of usage of electricity, this study assesses the current status of electricity access in an urban poor area of Dhaka and identifies barriers to electricity access from both demand and supply side. Barriers specific recommendations are also suggested based on the experiences from field visit and the best practices outside Bangladesh are also identified.

Description: In this study, the catalytic effects of impregnated catalysts of K 2 CO 3 , alkali earth, and transition metal salts in lignite-CO 2 gasification were investigated. The gasification experiments were conducted over a temperature range of 800–900 °C at atmospheric pressure. Catalysts such as K 2 CO 3 , Ca(OH) 2 , CaCO 3 , Ce(NO 3 ) 3, and Fe(NO 3 ) 3 were impregnated on Mongolia coal using aqueous solutions in a rotary evaporator. The modified volumetric reaction model of the gas-solid reaction was applied to the experimental data to obtain kinetic information. The catalytic activity of single catalysts followed the sequence K 2 CO 3  〉 Ca(OH) 2  〉 CaCO 3 〉 Fe(NO 3 ) 3  ≈ Ce(NO 3 ) 3 . The reaction rate with K 2 CO 3 can be enhanced by the addition of Ca(OH) 2 . The synergistic effect of K 2 CO 3 4 wt. % + Ca(OH) 2 1 wt. % exhibited the highest catalytic activity at 900 °C and the lowest activation energy.

Description: This is an investigation on the development of a numerical assessment method for the hydrodynamic performance of an oscillating water column (OWC) wave energy converter. In the research work, a systematic study has been carried out on how the hydrodynamic problem can be solved and represented reliably, focusing on the phenomena of the interactions of the wave-structure and the wave-internal water surface. These phenomena are extensively examined numerically to show how the hydrodynamic parameters can be reliably obtained and used for the OWC performance assessment. In studying the dynamic system, a two-body system is used for the OWC wave energy converter. The first body is the device itself, and the second body is an imaginary “piston,” which replaces part of the water at the internal water surface in the water column. One advantage of the two-body system for an OWC wave energy converter is its physical representations, and therefore, the relevant mathematical expressions and the numerical simulation can be straightforward. That is, the main hydrodynamic parameters can be assessed using the boundary element method of the potential flow in frequency domain, and the relevant parameters are transformed directly from frequency domain to time domain for the two-body system. However, as it is shown in the research, an appropriate representation of the “imaginary” piston is very important, especially when the relevant parameters have to be transformed from frequency-domain to time domain for a further analysis. The examples given in the research have shown that the correct parameters transformed from frequency domain to time domain can be a vital factor for a successful numerical simulation.

Description: In this paper, transient computational fluid dynamics (CFD) simulations of a straight-bladed Darrieus type vertical axis wind turbine were performed by means of an in-house CFD code. The Spalart-Allmaras turbulence model was implemented in the numerical code for the turbulence. Particular emphasis was placed on effect of interaction between vortices and blades on the aerodynamic performance of the simulated turbine at different tip speed and solidity ratios. The obtained results suggested that vortices were shed from previous blade passages and the close encounter of a rotor blade with these vortices can have a considerable impact on power coefficient of the simulated turbine during operation at different tip speed ratios. As a result, possible reasons for the changes in the behavior of this type of turbine due to the variation of tip speed ratio and solidity were proposed.

Description: A proton conducting polymer electrolyte nanocomposite membrane has been fabricated by using poly (vinyl alcohol) (PVA), Chitosan, and poly (styrene sulfonic acid) (PSSA) polymers and montmorillonite Cloisite ® 30B clay with the objective of its application in direct methanol fuel cells. Comparative studies of a PVA/PSSA/Chitosan/Cloisite30B clay composite membrane with a base PVA/PSSA membrane has been carried out by using thermal gravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, X-ray diffraction, methanol permeability and proton conductivity measurements. Properties of the membrane have been compared with Nafion ® 117 at identical test conditions. Methanol permeability of the PVA/PSSA/Chitosan/Cloisite30B clay composite membrane has been found to be superior to that of PVA/PSSA as well as Nafion117 membranes. Water uptake of the membrane is much higher compared to the Nafion117 membrane. Proton conductivity of the membrane has been found in the range of 10 −2 S cm −1 at room temperature and 70% relative humidity. Selectivity of the membrane is in the range of 10 4  S s cm −3 , which is better than that of Nafion117.

Description: In recent years, Chinese wind power has progressed rapidly, such that most accessible high quality, onshore sites are either operational or at least in some stage of development. Thus, offshore wind power has become the new industry focus. This paper reviews the development of China's offshore wind power and its current status. All aspects of preliminary planning, design, approval, construction, O&M, and electricity pricing policy are discussed from a developer's perspective. Data and key points are introduced, based on current engineering practices. European developments are reviewed briefly to help assess similar problems and issues in China. This study suggests that China's relative lack of experience must be recognized. Nevertheless, the development of this nascent technology is already underway.

Description: To improve the accuracy of short-term load forecasting, a differential evolution algorithm (DE) based least squares support vector regression (LSSVR) method is proposed in this paper. Through optimizing the regularization parameter and kernel parameter of the LSSVR by DE, a short-term load forecasting model which can take load affected factors such as meteorology, weather, and date types into account is built. The proposed LSSVR method is proved by implementing short-term load forecasting on the real historical data of Yangquan power system in China. The average forecasting error is less than 1.6%, which shows better accuracy and stability than the traditional LSSVR and Support vector regression. The result of implementation of short-term load forecasting demonstrates that the hybrid model can be used in the short-term forecasting of the power system more efficiently.

Description: Accurate wind speed prediction provides essential information for system operation and management with wind power integration. Most existing prediction methods chose to model original data directly without considering the inherent characteristics of wind speed time series. However, the properties of characteristic components can offer better information for prediction. This paper proposes to extract the characteristic components of original data using the ensemble empirical mode decomposition and sample entropy techniques. For the multi-step ahead forecasting of characteristic components, a multiple-input multiple-output (MIMO) based extreme learning machine model is constructed. The effectiveness of the proposed approach is illustrated by applying it to two real wind farm datasets. The extracted characteristic components are shown to be of much lower complexity and the MIMO strategy is found to be better than the common iterated strategy and direct strategy. Moreover, compared to the existing neural networks based methods, the proposed approach has been demonstrated to be a more effective method in both prediction accuracy and computational cost.

Description: A dynamic synchronous d-q reference frame based modeling and a novel adaptive higher order sliding mode control theory for doubly fed induction generator (DFIG) based wind energy conversion system (WECS) have been proposed in this paper. As depicted from the literature, the sliding mode control strategy involving computation of converter currents introduces some inaccuracies for optimal extraction of the power references of the DFIG. On the contrary, the proposed method contributes with some important features such as chatter-free performance and heftiness in terms of transient response of the non-linear systems subjected to dynamic conditions such as lower and higher wind speeds. Consequently, a higher order sliding mode controller using the active and reactive power of the DFIG as controller inputs has been proposed in this paper. As compared with the other two methods, the proposed higher order sliding mode power control souvenirs a significantly improved as well as stable performance of the DFIG based WECS in terms of reduced settling time as well as quickly damping out the oscillations exhibited by the system. The robustness and stability of the proposed control strategy has been validated in MATLAB environment, in terms of the comparison of its performance with traditional proportional-integral and existing first-order sliding mode controller (employing converter current as input) subjected to a wide range of disturbances for sub and super synchronous mode of operation of the DFIG subjected to lower and higher wind speeds along with the available practical wind speed data, as depicted in the simulation and result section.

Description: The transient fault characteristics of power systems undergo profound changes with the large-scale application of doubly fed wind turbines. Thus, the short-circuit current (SCC) contributed by doubly fed induction generation (DFIG) should be fully understood for the operation of power systems. However, the SCC of DFIG is difficult to analyze under excitation control when the voltage drops partially. A requisite analysis of the coupling between excitation control and the electromagnetic process under symmetric fault is conducted in this study. The transient disturbances in the control loop under fault are analyzed by constructing a vector dynamic model of rotor current. The simplified expressions of SCCs under different control modes are deduced. The characteristics of the SCCs are obtained from these simplified expressions. The effects of excitation control on transient behavior are analyzed considering that controls are usually designed under normal conditions. The theoretical analyses are validated by simulations.

Description: This paper proposes an integrated low-voltage ride-through (ILVRT) scheme to improve the transient responses of the doubly fed induction generator (DFIG) based wind turbines. The proposed strategy integrates a series-dynamic-resistor, a dc-link chopper, and a crowbar (CRW) with a coordinated switching control strategy. Generally, when the CRW short-circuits the rotor windings, the rotor-side power converter (RSPC) is blocked and the DFIG becomes a squirrel-cage induction generator. This temporary configuration acquires its magnetization current from the grid, which leads to a more voltage-dip. On the other hand, if the CRW is combined with the series R-L circuit, the RSPC remains connected to the slip-rings, and hence, the active/reactive ( P-Q ) control is partially maintained. Moreover, the terminal voltage depression is reduced compared to when only the CRW scheme is applied. Following a brief discussion of two conventional LVRT strategies, the proposed ILVRT scheme is designed with an improved switching control algorithm which minimizes the CRW activation time. By applying the proposed ILVRT approach, the negative effects of the grid faults and two conventional strategies can be avoided. Finally, the performance comparison between the two conventional LVRT strategies and the proposed ILVRT scheme is conducted with the simulation results using MATLAB/Simulink software.

Description: In this paper, an algorithm for maximum power point tracking (MPPT) for photovoltaic based generation systems has been proposed. The technique is primarily based on “bang-bang” (hysteresis) control strategy. It is implemented using digital signal processor (DSP) TMS320F2812, which controls the DC-DC boost converter to enhance accuracy and speed. Code Composer Studio v3.1 is used to program DSP TMS320F2812. As compared to the conventional techniques for MPPT, the proposed configuration results in a simple configuration and a good overall efficiency. A complete description of various aspects of the system is presented, such as converter design, programming of the controller, and tuning of system components. Results obtained from simulation studies and experimental investigations show conformity to the proposed concepts.

Description: The paper deals with a comparative analysis (in terms of energetic efficiency) between the mono-axis and dual-axis tracking solutions implemented on a photovoltaic (PV) string. The study reveals which solution is more efficient in the geographical area of Braşov, and under which conditions. The tracking efficiencies of the mono-axis and dual-axis systems are compared considering two orientation programs: seasonal and annual. Taking into account the technical and economical aspects, besides the energy gain of the dual-axis system, it was concluded that a mono-axis tracking system is preferred for the studied geographical area. The study is performed by using the virtual prototype of the PV tracking system, which is approached in mechatronic concept. An algorithm for the optimal design of the step-by-step tracking law is also developed, the maximization of the energetic efficiency of the PV string with solar tracker being the optimization goal. Finally, experimental data are used to validate the simulation results.

Description: Given the rapid increase of residential energy consumption in Beijing, the question of how to promote residential energy-saving behavior is an emerging topic that is increasingly engaging the attention of scholars. To address this issue, this paper provides an empirical analysis that identifies and explores the determinants of an energy-saving behavioral intention among residents from the perspective of the theory of planned behavior (TPB). A theoretical model was constructed by refining and extending the classic TPB model according to the scope and requirements of this study and the existing situation in China. Survey data collected from 276 residents in Beijing were analyzed, and hypothesized relationships in the model were then verified using a structural equation model. The results show that subjective norms, environmental attitudes, information publicity, lifestyles, and perceived behavioral control significantly influence residents' energy-saving behavior, while demographic factors, such as educational background, household income, and age, had no obvious effects on behavioral intentions. Although knowledge regarding energy did not exert a direct influence on residents' energy-saving behavioral intentions, it did exert an indirect influence via environmental attitudes. Our results indicate that the role of households in saving energy expenditure should be emphasized, and financial incentives could be adopted to help promote environmental awareness among Beijing's residents. In addition, environment-friendly and energy-saving habits should also be inculcated.

Description: The impact of controlling the aspect ratio variation on glass substrate for a p-i-n a-Si:H solar cell was investigated and reported. Compared to a flat glass substrate (Corning Eagle XG), we demonstrate an increase of haze ratio from 1% to 79.1%, and an increment in the aspect ratio from 0.1 to 1.16, which is an increase to a high slope angle, using wet chemical etching. Optical transmittance measurements show a major improvement of from 92% to 96% for a wavelength of between 300 and 1100 nm, compared to the reference flat glass. A p-i-n a-Si:H solar cell was simulated using Advanced Semiconductor Analysis simulation based on these haze ratio and aspect ratio results, and yielded an increase in short-circuit current density (J sc ) from 15.38 to 18.74 mA/cm 2 , as the aspect ratio was increased from 0.1 to 0.84.

Description: Mahua seed ( Madhuca indica ) was co-pyrolyzed with waste polystyrene (Thermocol) with an aim to increase the yield and fuel properties of the pyrolytic oil. Co-pyrolysis was carried out at a temperature of 525 °C in a semi-batch reactor. Co-pyrolysis experiments were performed by varying Mahua seed to waste polystyrene ratios such as 1:1, 2:1, 4:1, and 8:1. The condensed liquid product was collected as aqueous and oil phase. The fuel properties and composition of the co-pyrolytic oil were evaluated and compared with that of Mahua seed pyrolytic oil. The process was optimized on the basis of high energy content of the pyrolytic oil. The synergistic effect of waste polystyrene during co-pyrolysis with Mahua seed (at the ratio of 2:1) yielded high calorific value, low pH, and low viscous co-pyrolytic oil in comparison with seed pyrolytic oil. Gas chromatography–mass spectrometry (GC-MS) analysis of co-pyrolytic oil confirmed that the amount of esters increased during co-pyrolysis, which resulted in an increased calorific value.

Description: This paper makes a comparative investigation of the three basic non-isolated dc-dc converters used as interface for maximum power point tracking (MPPT) application in photovoltaic generators using the direct duty ratio control tracking algorithm. Analysis of the buck, boost, and buck–boost converters has been undertaken to study the behavior of the converter's performance with respect to the changing atmospheric conditions and in-turn duty ratio variation (as a result of MPPT) and the tracking efficiency of each converter. Effect of different resistive loads on the output of the converter side has also been considered for the three topologies and it has been observed that the buck-boost converter is the only converter which is able to track the maximum power point under variation of insolation, temperature, and loading effect, with the highest tracking efficiency.

Description: Finding bacterial strains for effective hydrogen production and optimization of the fermentative conditions are two major approaches to promoting commercial application of bio-hydrogen. In the present study, we carried out experiments to examine factors that affected H 2 yield in Enterobacter sp. CN1. The result showed that H 2 could be produced from formate alone and the yields were positively correlated with formate concentrations. Moreover, the yield of H 2 from xylose was significantly increased in the presence of formate, revealing that formate is not only a good carbon source but also promotes H 2 production from xylose in strain CN1. The production of H 2 from formate was not affected by pH; however, H 2 production from xylose at pH 7 was higher than that at pH 6, no matter if formate is presence or absence in the medium. Further, H 2 production from pyruvate was inhibited completely when sodium hypophosphate (HPP) was present, but formate-dependent H 2 production was mostly not affected. In addition, H 2 production from glucose or xylose was dramatically reduced but sill detectable in the presence of HPP, suggesting that formate hydrogenlyase is the main pathway responsible for H 2 production from xylose in Enterobacter sp. CN1. To confirm the above hypothesis, the formate hydrogenlyase activator ( fhlA ) gene was cloned and over-expressed in strain CN1. Compared with the wild-type, recombinant CN1 strain increased H 2 production per gram of xylose and per gram of cells by 10.5% and 18.8%, respectively, in the presence of xylose.

Description: The properties of binary H 2  + CH 4 clathrate hydrates have been estimated using the extended van der Waals and Platteeuw statistical thermodynamic model that takes into account the lattice relaxation, host-guest, and guest-guest interactions as well as the quantum nature of guest behavior in the clathrate cavities. It has been found that at a small methane concentration in the gas phase the stable hydrate phase has cubic structure II (CS-II) and at a methane concentration of 6% stabilizes cubic structure I, which is metastable in the case of the pure hydrogen hydrate. This is in agreement with recent experimental data. The amount of hydrogen storage depends on the methane concentration in the gas phase as well as the thermodynamic conditions of hydrate formation. Hydrogen storage up to 2.6 wt. % can be achieved in the binary H 2  + CH 4 CS-II hydrate at T = 250 K.

Description: In this paper, an integrated energy-exergy-based evaluation was conducted on an entire bio-dimethyl ether (bio-DME) system established using ASPEN PLUS. The system contained a novel combination of biomass torrefaction unit (BTU) and entrained-flow gasification (EFG) followed by single-step DME synthesis, including DME purification, as well as heat recovery and cogeneration. The mass and energy balances were calculated in detail and compared with those cited in previous literature. The overall energetic and exergetic efficiencies of the system were found to be 55.2% and 46.9%, respectively. The exergy rates for all processes involved in the system were calculated and the locations as well as magnitudes of exergy losses were determined. Subsequently, the causes of exergy losses were deeply analyzed followed by pointing out the corresponding improvement potentials. Further investigation indicated that considerable improvement could be achieved for BTU and EFG, where the largest and second largest exergy loss took place. According to the parametric investigation based on energetic and exergetic efficiencies, controlling the BTU and EFG operation at 250 °C and 1200 °C, respectively, was proposed to improve the efficiency of the system and increase the overall exergetic efficiency to 52.6% while reducing the total exergy losses by 5.7%.

Description: In this paper, we first proceed to develop the mathematical tools for the calculation of CO 2 emissions abatement (annual and total) due to the installation of concentrating solar power (CSP) plants instead of the traditional systems. For this, we take into account the targets for the CSP cumulative installed capacity from several scenarios elaborated by the International Energy Agency. We have also developed in this paper mathematical closed-form expressions for the evaluation of the extra-costs of implementing these scenarios, and calculated the unit costs of the CO 2 emissions avoided by the new CSP systems. The obtained results are shown both graphically and numerically, and their applications to energy planning policies are discussed. From the results exposed in this paper, it is possible to evaluate the economic advantages of installing the new CSP plants in those geographical areas with higher pollutant electricity mixes, as well as the planning of the most convenient calendar for CSP systems implementation.

Description: Two step methods have been used for the deposition of ZnO porous films onto a fluorine doped tin oxide coated glass substrate, involving spin coating, followed by the doctor blade. Deposited ZnO films were sensitized with rose bengal (4, 5, 6, 7-tetrachloro- 2′, 4′, 5′, 7′ tetraiodofluorescein) dye and has been used as a photoanode in a dye sensitized solar cell (DSSC). Performances of DSSCs were studied at a different dye sensitization time. As a consequence, enhancement of power conversion efficiency from 0.83% to 1.90% has been observed. The morphology of films is characterized by scanning electron microscopy. Electrochemical impedance spectroscopy has been used to understand the electron transfer at the interfaces.

Description: Generated power by 5 MW wind turbine was predicted by using measured wind data at weather station called Herald of Meteorological and Oceanographic Special Unit-1 (HeMOSU-1) which is installed at south west coast of Korea. Transient time history of turbulent wind was generated from 10-min mean wind speed stored at HeMOSU-1 and then it was used in estimation of electric power by Bladed. Those estimated powers were used in both polynomial regression and neural network based power estimation. They were compared with each other for daily power and yearly power. Effect of mean wind speed and turbulence intensity was quantitatively analyzed and discussed. This technique further can be used to assess lifetime power of wind turbine.

Description: An offshore wind turbine in shallow water is installed by a self-elevated mobile unit that is usually referred to as a jack-up barge or jack-up vessel. The jack-up vessel consists of a buoyant platform together with independent legs that can position the vessel above the water, thereby reducing external loadings for a safe operation condition. The retrieval process for the jack-up legs can be very difficult due to the high extraction resistance caused by soft soil. In soft clay, high suction force can develop around the spudcan attached at the end of the jack-up legs. Therefore, a jetting system is required to break the suction in order to pull out the legs. It is important to design the jetting system with an optimized piping arrangement to allow the easy operation. Various factors must be considered in the design of the jetting piping system since the level of embedment, type of soil, and pipe sizes and locations can affect the performance of the system. In this paper, we present the characteristics of west coast geological features by subsea geological survey and the design of jetting system that was analyzed using pipe flow analysis program.

Description: A floating Tension Leg Platform (TLP) wind turbine was constructed at scale 1/200 and its dynamic response was analysed experimentally in co-directional wind and waves. The wind turbine was Froude scaled and a new rotor was designed to yield maximum power and Froude scaled thrust at the low model Reynolds number. Physical limitations due to the large scaling ratio further meant that some structural adjustments were necessary. Nacelle and floater accelerations were measured by means of two accelerometers. The TLP was moored with four different tendon configurations and exposed to different constant wind speeds and irregular sea states as well as a range of regular waves. It was found that an increase in wind speed reduces the wave-induced floater motion but causes slightly larger nacelle displacements. Further, the orientation of the spokes relative to the direction of wind and waves influences the pitch stiffness and thereby the nacelle displacements. Inclining the tendons towards the wind turbine reduces the nacelle displacements significantly and reduces the occurrence of slack tendons, but increases the inline tilt-motion of the rotor. Application of a very stiff mooring configuration increases the occurrence of slack tendons and the magnitude of the pitch accelerations. In a robust commercial design, however, slack tendons must be avoided. The experiments demonstrate the ability of the wind turbine model and the experimental setup to give insight to the dynamic characteristics of floating TLP wind turbines.

Description: With the increased awareness on excessive energy consumption, increasing fuel cost and negative environmental impact (ozone depletion and global warming) of the major heat generation systems and processes, the ability of heat pumps to generate high temperature with very efficient use of energy and minimal environmental impact has gained lots of awareness over the years. Some domestic and most industrial heating and refrigeration applications demand very high temperature lifts. Single-stage cycles do not practically support these applications since their performance and reliability decrease greatly. High temperature generation can be successfully executed through the use of cascade heat pump. This study analyzes the effects of compressor speed and electronic expansion valve (EEV) opening on the performance of the cascade heat pump in heating mode. The rate of increase of capacity with high-stage (HS) EEV opening at higher HS compressor speed is larger than it at high low-stage (LS) compressor speed. The slope of the capacity with the HS EEV opening was much steeper at small opening range than that at large opening range. When the LS compressor speed increased, the maximum Coefficient of Performance (COP) occurred at larger HS EEV opening than the standard opening. The COP variation at the range of low HS compressor speed had smaller dependency on the LS EEV opening than that at the range of high HS compressor speed.

Description: In this paper, transient computational fluid dynamics (CFD) simulations of a straight-bladed Darrieus type vertical axis wind turbine were performed by means of an in-house CFD code. The Spalart-Allmaras turbulence model was implemented in the numerical code for the turbulence. Particular emphasis was placed on effect of interaction between vortices and blades on the aerodynamic performance of the simulated turbine at different tip speed and solidity ratios. The obtained results suggested that vortices were shed from previous blade passages and the close encounter of a rotor blade with these vortices can have a considerable impact on power coefficient of the simulated turbine during operation at different tip speed ratios. As a result, possible reasons for the changes in the behavior of this type of turbine due to the variation of tip speed ratio and solidity were proposed.

Description: This paper presents a risk-based decision-making framework for the Distributed Generation (DG)-owning retailer to determine the optimal participation level in the forward and the day-ahead electricity markets, as well as the optimal scheduling of DG units. The energy price in the day-ahead market is very volatile and varies every hour. Also, unpredicted failures of DG units may impose a great financial loss on the retailer. Therefore, the retailer has to evaluate the effects of uncertain parameters to hedge the financial loss. In this paper, the financial risk associated with the uncertain prices is evaluated using the chance constraint optimization method. The normal density function is applied to model the probabilistic realizations of uncertain prices, and scenarios are generated via the scenario tree technique. Moreover, the availability of generation units is modeled by the availability probability. The proposed risk-based framework allows the retailer to determine the optimal strategy at the given risk level. The objective-function of the presented model is based on maximizing the expected profit in a way that ensures the specific profit constraint will be satisfied at the operation period with a defined probability. The performance and efficiency of the presented decision-making framework are analyzed on the sample DG-owning retailer, and the optimal framework is simulated under different risk levels.

Description: This is the second part of the assessment of primary energy conversions of oscillating water columns (OWCs) wave energy converters. In the first part of the research work, the hydrodynamic performance of OWC wave energy converter has been extensively examined, targeting on a reliable numerical assessment method. In this part of the research work, the application of the air turbine power take-off (PTO) to the OWC device leads to a coupled model of the hydrodynamics and thermodynamics of the OWC wave energy converters, in a manner that under the wave excitation, the varying air volume due to the internal water surface motion creates a reciprocating chamber pressure (alternative positive and negative chamber pressure), whilst the chamber pressure, in turn, modifies the motions of the device and the internal water surface. To do this, the thermodynamics of the air chamber is first examined and applied by including the air compressibility in the oscillating water columns for different types of the air turbine PTOs. The developed thermodynamics is then coupled with the hydrodynamics of the OWC wave energy converters. This proposed assessment method is then applied to two generic OWC wave energy converters (one bottom fixed and another floating), and the numerical results are compared to the experimental results. From the comparison to the model test data, it can be seen that this numerical method is capable of assessing the primary energy conversion for the oscillating water column wave energy converters.

Description: In this study, the catalytic effects of impregnated catalysts of K 2 CO 3 , alkali earth, and transition metal salts in lignite-CO 2 gasification were investigated. The gasification experiments were conducted over a temperature range of 800–900 °C at atmospheric pressure. Catalysts such as K 2 CO 3 , Ca(OH) 2 , CaCO 3 , Ce(NO 3 ) 3, and Fe(NO 3 ) 3 were impregnated on Mongolia coal using aqueous solutions in a rotary evaporator. The modified volumetric reaction model of the gas-solid reaction was applied to the experimental data to obtain kinetic information. The catalytic activity of single catalysts followed the sequence K 2 CO 3  〉 Ca(OH) 2  〉 CaCO 3 〉 Fe(NO 3 ) 3  ≈ Ce(NO 3 ) 3 . The reaction rate with K 2 CO 3 can be enhanced by the addition of Ca(OH) 2 . The synergistic effect of K 2 CO 3 4 wt. % + Ca(OH) 2 1 wt. % exhibited the highest catalytic activity at 900 °C and the lowest activation energy.

Description: Flexible Cu 2 ZnSnS 4 (CZTS) thin films are more advantageous than those on rigid glass substrates. In this study, vacuum-based magnetron sputtering was utilized to fabricate CZTS thin films on flexible polyimide substrates. Zn/Sn/Cu precursors were sputtered and then sulfurized. The influences of sulfurization temperature on the structural, compositional, morphological, electrical, and optical properties of the fabricated thin films were analyzed. The experimental results show that the CZTS structures form on the polyimide substrates after sulfurization. The crystallinity of CZTS enhances and the secondary phases in the thin films decrease with increasing sulfurization temperature. Single-phase CZTS thin films are obtained for sulfurization temperatures reaching 450 °C. The compositions of the fabricated thin films are Cu-poor and Zn-rich. The fabricated CZTS thin films show p-type conductivity. The direct optical band gaps of the thin films range from 1.51 eV to 1.55 eV. The absorption coefficients of these films are larger than 1 × 10 4  cm −1 above the band gap edge. The experimental results reveal the feasibility of the deposition of CZTS thin films on polyimide substrates by vacuum-based methods. The fabricated thin films can suitably function as absorbers for solar cell applications.

Description: Security risk assessment difficulties brought about by uncertainties can be solved by probabilistic power flow. A security risk assessment scheme of the power system using fast probabilistic power flow is proposed in this paper. The scheme applied probabilistic power flow on fast decoupled power flow model, considering multi-scenario of wind power and static characteristics of power systems, gaining the probabilistic distribution information of each desired variable by improved Von Mises method based on cumulants. Besides voltages and branch flows, the scheme can also obtain the distribution of frequency to assess the power system completely, which is not concerned in conventional probabilistic power flow calculation. The proposed algorithm was realized by programming based on Matpower 4.0. The examples executed on IEEE RTS-24 system demonstrate the rapidity, validity, and prospect for online application of the proposed scheme.

Description: In the present work, polydisperse zinc oxide composed of nano and submicron size particles is used to prepare photo-anode for dye sensitized solar cell. The particles are synthesized through auto-combustion route and characterized in terms of their phase formation behavior as well as morphological properties. UV-vis diffused reflectance spectra of the prepared photo-anode show its promising dye uptake and incident light scattering behavior. The prepared cells reveal ∼3.2% solar to electric conversion efficiency. The fairly acceptable efficiencies of the cells are attributed due to the efficient scattering of incident light and reasonable dye uptake within polydisperse particulate photo-anode.

Description: This study investigates the empirical relationship between energy consumption, international trade, and real income in the USA, which is the second largest energy consuming country following China. It employs bounds tests to level relationships and conditional error correction models through Auto-Regressive Distributed Lag specification. Using annual data from the 1960 to 2010 period, the results reveal a long-term relationship between energy consumption, international trade, and real income in the USA. It is also found that energy consumption is determinant of exports, imports, and real income. Conditional Granger causality tests suggest that there is a feedback relationship between energy consumption, international trade, and real income in the long-term for the USA economy.

Description: To compensate for the limitation of the energy intensity indicator and to constrain energy consumption growth more directly and severely, China had decided to implement the Total Energy Consumption Control (TECC) policy during the 12th Five-Year Plan (FYP). This paper analyzes the situation of energy consumption in 3 scenarios based on the energy consumption trend during the 11th FYP, the energy intensity reduction target during the 12th FYP, and the TECC policy. The Energy Conservation Comprehensive Evaluation System (ECCES) which includes 5 indicators reflecting energy conservation responsibility and 3 indicators reflecting energy conservation difficulty has been built, and Analytic Hierarchy Process (AHP) and Entropy methods are used to determine the weights of 8 basic indicators. According to the ranking of comprehensive evaluation scores of ECCES, 30 provinces are divided into 5 clusters, which are assigned 3%, 3.5%, 4.2%, 5.5%, and 6.8% of controlled energy consumption growth rate, respectively. By comparing and analyzing energy consumption situations in 3 scenarios, we find that the TECC policy has the strongest constraint effect, and can achieve unification of provincial and national energy conservation goals. The provincial decomposition result of energy consumption controlled target of TECC policy roughly remains consistent with the current economic and energy development layout of China that the provinces in southeast coastal developed areas are assigned lower controlled energy consumption growth rate while the backward inland provinces are assigned higher growth rates.

Description: This paper presents a novel control method for Maximum Power Point Tracking of wind turbines (WTs) equipped with a Permanent Magnet Synchronous Generator (PMSG) and a Direct Matrix Converter (DMC). The method calculates the optimum wind turbine speed and maximizes the extracted power from wind turbine. This is done by Hill Climb Search method, which is simple and does not need to know the generator parameters and no need to solve the complicated differential equations of generator. WT rotor speed is compared with its optimal value and then DMC controls WT until its rotor speed reaches its optimum value. Under this situation, maximum power is extracted from WT and is injected to the grid with unity power factor. It is implemented by controlling the phase and the amplitude of the DMC output voltage by Venturini switching method. Simulations are done on a 2 MW PMSG WT in MATLAB/SIMULINK to obtain the results, the wind speed was varied both using the Van Der Hoven method and changing the wind step. The obtained results verify the accuracy and simplicity of proposed method.

Description: Solid oxide fuel cell (SOFC) is being developed for a wide variety of applications because of their high efficiency, reliability, and fuel adaptability. In this paper, a grid connected SOFC system is presented by using PSCAD software. The power conditioning unit (PCU) is used for simulation studies and also the transformer is used for electrical isolation. The simulation studies of the SOFC dynamic model are investigated for three case studies. In the first simulation study, the SOFC dynamic model is connected to constant and variable DC loads without PCU. The second simulation study is performed for three phase AC load conditions. The AC performance of SOFC is tested under an AC load through the transmission line of 400 V at the length of 10 km. The last simulation study is implemented for the grid connected SOFC system. In the grid connected case study, a three bus system, which includes an infinite bus, a load bus and a fuel cell bus, is formed under AC load conditions. The results show the fast response capabilities of the grid connected SOFC system in different case studies and various load types.

Description: Commonly used wind power forecasts methods choose only one representative wind turbine to forecast the output power of the entire wind farm; however, this approach may reduce the forecasting accuracy. If each wind turbine in a wind farm is forecasted individually, this considerably increases the computational cost, especially for a large wind farm. In this work, a compromise approach is developed where the turbines in the wind farm are clustered and a forecast made for each cluster. Three clustering methods are evaluated: K-means; a self-organizing map (SOM); and spectral clustering (SC). At first, wind turbines in a wind farm are clustered into several groups by identifying similar characteristics of wind speed and output power. Sihouette coefficient and Hopkins statistics indices are adopted to determine the optimal cluster number which is an important parameter in cluster analysis. Next, forecasting models of the selected representative wind turbines for each cluster based on correlation analysis are established separately. A comparative study of the forecast effect is carried to determine the most effective clustering method. Results show that the short-term wind power forecasting on the basis of SOM and SC clustering are effective to forecast the output power of the entire wind farm with better accuracy, respectively, 1.67% and 1.43% than the forecasts using a single wind speed or power to represent the wind farm. Both Hopkins statistics and Sihouette coefficient are effective in choosing the optimal number of clusters. In addition, SOM with its higher forecast accuracy and SC with more efficient calculation when applied into wind power forecasts can provide guidance for the operating and dispatching of wind power. The emphasis of the paper is on the clustering methods and its effect applied in wind power forecasts but not the forecasting algorithms.

Description: Mn 3+ /Mn 2+ redox couple with high reaction potential was successfully introduced into a redox flow battery, and the hybrid V/Mn flow cell with multiple redox couples based on Mn(III)/Mn(II) vs. V(III)/V(II) and V(V)/V(IV) vs. V(III)/V(II) was investigated. The results show that the concentration of sulfuric acid of 4 M is suitable for the viscosity, electrical conductivity, and electrochemical performance. Redox flow battery employing V/Mn and V as positive and negative active species was assembled and the charge-discharge performance was evaluated. The hybrid V/Mn flow cell exhibits good capacity retention and energy efficiency can reach up to 80% over 40 cycles. The energy density of 17.85 W h l −1 is achieved for V/Mn hybrid cell, 25.3% higher than that of all vanadium cell.