ALBERT

Description: This paper presents the performance of a wind power system under failures in the lubricant system, and a procedure is proposed to detect the failure. According to the fact that the friction torque caused by the lubricant system, failure makes the maximum power point (MPP) of the wind system to be smaller than that of normal operation; for MPP tracking operations, the difference between actual and simulated (estimated) output power of the wind system is an indicator for the lubricant system failure. However, for non-MPP tracking operations, in which the demanded power is small enough to be satisfied by the failed wind system, the above indicator cannot be used to detect the lubricant system failure. In this case, the predetermined angular shaft speed ratio is used to detect the lubricant system failure. Moreover, the converter failure is considered in this paper, and a model-based fault detection filter is designed to detect the DC/DC converter failure in a wind system. The proposed detection filter consists of an observer combined with a residual signal generator, where the driving torque is assumed as an unknown bounded input in the proposed failure detection scheme. Numerical simulation results support the proposed detection procedures.

Description: Research on hybrid systems has emerged in recent years due to the current and growing global interest in the search for energy resources that lead to a decrease in fossil fuel use for power generation. Such systems are coupled to both conventional and non-conventional sources. Therefore, in this paper we present a review of hybrid energy systems, with emphasis on those which are engaged in photovoltaic solar energy. The purpose is to identify the different integration frameworks and types of storage capacities according to energy demand, geographic area, and other parameters. Finally, an overview of Mexico in relation to hybrid systems is presented as an attempt to motivate researchers, industry, and government to implement and develop these systems.

Description: This paper proposes a fuzzy control method for tracking maximum power point in photovoltaic (PV) power systems to solve a fast irradiation change problem. Perturb and Observe (P&O) is known as a very simple maximum power point tracking and is extensively disseminated. Fuzzy logic is also simple to investigate and provides fast dynamics. The suggested technique combines both fuzzy logic and P&O advantages. A fuzzy logic-based P&O algorithm is illustrated to identify the fault direction tracking of conventional P&O algorithm under trapezoidal irradiation change. The proposed algorithm is verified using Matlab/Simulink™ software. The robust tracking capability under rapidly increasing and decreasing irradiance is verified experimentally with a PV array emulator. Simulation and experimental results confirm that the proposed algorithm provides effective, fast, and accurate tracking compared to the conventional P&O algorithm.

Description: The increasing penetration of distributed generators (DGs) makes further interconnection of multiple energy carriers possible. In this paper, an integration model comprising IEEE-33 bus distribution network and a correspondingly designed water system is proposed with DG coupling of thermal and electrical energy. The integrated energy system incorporates the constraints of the distribution network, water system, and DGs and ensures that the electrical and thermal demands of the integrated energy system are satisfied simultaneously by energy flow. An optimal procedure including optimal sizing, positioning, and operation of DGs and gas boilers in a given system was implemented while minimizing the total costs of investment and operation. The model constitutes a mixed integer nonlinear problem, as it takes the power flow calculation and the nonlinear characteristics of DG efficiency into consideration. Therefore, the particle swarm optimization algorithm is employed to simulate the proposed model. The simulation results in conjunction with numerical studies reveal the impact of the water system on the optimal configuration of DGs and the advantages of the integrated energy system on economic considerations, voltage level, and net loss.

Description: Developing countries like Pakistan need a continuous supply of clean and cheap energy. It is a very common fear in today's world that the fossil fuels will be depleted soon and the cost of energy is increasing day-by-day. Renewable energy sources and technologies have the potential to provide solutions to long-standing energy problems faced by developing countries. Currently, Pakistan is experiencing a critical energy crisis and renewable energy resources can be the best alternatives for quickly terminating the need for fossil fuels. The renewable energy sources such as solar energy, wind energy, and biomass energy combined with fuel cell technology can be used to overcome the energy shortage in Pakistan. Biomass is a promising renewable energy source and is gaining more interest because it produces a similar type of fuel like crude oil and natural gas. Energy from biomass only depends upon the availability of raw materials; therefore, biomass can play an important role to fulfill the energy requirements of the modern age. The use of energy has increased greatly since the last century and almost all human activities have become more dependent on energy. Biomass, being a potential and indigenous candidate, could be a good solution to meet the energy needs of Pakistan. In this review paper, the detailed current energy requirements and solutions from available energy resources and the scope, potential, and implementation of biomass conversion to energy in Pakistan are explored with a special focus on the major province of Punjab and the advantages of biomass for energy purposes.

Description: Reducing wake losses in wind farms by deflecting the wakes through turbine yawing has been shown to be a feasible wind farm controls approach. Nonetheless, the effectiveness of yawing depends not only on the degree of wake deflection but also on the resulting shape of the wake. In this work, the deflection and morphology of wakes behind a porous disk model of a wind turbine operating in yawed conditions are studied using wind tunnel experiments and uniform inflow. First, by measuring velocity distributions at various downstream positions and comparing with prior studies, we confirm that the non-rotating porous disk wind turbine model in yaw generates realistic wake deflections. Second, we characterize the wake shape and make observations of what is termed as curled wake, displaying significant spanwise asymmetry. The wake curling observed in the experiments is also reproduced qualitatively in Large Eddy Simulations using both actuator disk and actuator line models. Results suggest that when a wind turbine is yawed for the benefit of downstream turbines, the curled shape of the wake and its asymmetry must be taken into account since it affects how much of it intersects the downstream turbines.

Description: Changes in the topology of distribution networks which is due to connecting or disconnecting of distributed generations (DGs) is a critical challenge in maintaining protection coordination in these networks. Protection coordination is generally retrieved after deciding optimal capacity and location of installing DGs. Nevertheless, in this paper, a new method is presented which merges the protection coordination of distribution networks in the process of sizing and siting DGs. The presented approach of this paper, in addition to identifying the optimal location and capacity of DGs with the purpose of increasing the benefits and reducing cost of installing these resources, is to also create a robust protection coordination. In order to provide a robust protection coordination, the capacity and location of fault current limiters are identified parallel with sizing and siting DGs. The protection coordination considered in this paper results in grouping different topologies of the network according to allowable memory of protective relays. On this basis, the protection coordination of all operational topologies of the network is guaranteed. In order to coordinate each group interval linear programming is suggested. This method reduces the number of protection coordination constraints of each group and simplifies appropriate protection coordination for the group. The proposed method is tested on Zanjan Regional Electric Board, Iran. Simulation results are reported and discussed.

Description: Vegetable insulating oils (VIOs) have attracted wide attention for their high flash point, high insulation performance and degradability. However, the unsaturated fatty acids contained in VIOs reduce their oxidation stability, which requires the addition of some antioxidants to ensure their usage. Here, we establish a high-performance liquid chromatography (HPLC) method for determination of antioxidants in VIOs. The standard calibration curves of 3 analytes (PG, BHA, BHT) all show high linearity, and the correlation coefficients are all above 0.9994. Limits of detection of all three analytes range from 0.003 to 0.010 mg/ml; limits of quantitation range from 0.010 to 0.033 mg/ml. The new HPLC method is proved ideally suitable for the analysis of commercialized transformer oil Cooper-FR3 with precision (%RSD = 0.3%–0.7%) and accuracy (%recovery = 100.0%–102.1%), suggesting that this method is an efficient tool for routine screening of antioxidant contents in VIOs. We used this method to monitor the changes of antioxidant contents in the oxidation of two VIOs–soybean oil and rapeseed oil.

Description: This paper introduces a stochastic reliability evaluation methodology for quantifying the impact of unmanaged plug-in hybrid electric vehicles (PHEVs') charging on the transformers' hottest spot temperature (HST)-dependent aging failures. Further, a novel PHEVs' charging management method has been proposed from the distribution transformers' dynamic thermal modeling perspective. The proposed reliability evaluation method provided the precise stochastic model corresponding to the PHEV owners' behavior. The introduced reliability evaluation methodology has been applied to an actual distribution system of the Hormozgan Regional Electrical Company in Iran under various PHEVs' charging scenarios. The numerical results imply that the distribution transformers' failures are adversely affected due to unmanaged PHEVs charging. The system under study has been simulated during a 10-year-period. The test results show that the transformers' HST-dependent failures due to the PHEVs' charging demand load exponentially increased as a function of system age. As revealed by the results, the proposed PHEVs' charging management methodology mitigates the aggregated peak load and transformers' HST by deferring the peak charging load to midnight.

Description: Under partial shading conditions, the power–voltage (P-U) curve may exhibit multiple local maxima. This makes it challenging to track the global maximum power point (GMPP). Additionally, in such conditions, conventional maximum power point tracking (MPPT) methods cannot be used to extract the GMPP. This paper describes a modified firefly algorithm (MFA) that can rapidly and accurately extract the GMPP under partial shading conditions. The algorithm introduces the concepts of the global and local firefly densities during each iteration, and devises two elimination mechanisms to adaptively adjust the firefly population. The proposed method is compared with the traditional MPPT algorithms under four different partial shading conditions. Simulation results demonstrate that the MFA can immediately and accurately track the global maximum under the partially shaded conditions, and that the proposed method outperforms conventional techniques in terms of tracking efficiency and speed.

Description: The parameters influencing gas alternative water (WAG) for CO 2 flooding in the low permeability block of the Jilin oil fields in China were investigated using the numerical simulation software, Eclipse. The minimum miscibility pressure was first determined based on slim tube tests. Comparisons were made between continuous water flooding, continuous CO 2 flooding, and WAG flooding methods. The oil recovery ratio of “gas injection first method” was higher than that of “water injection first method” and the mechanism of CO 2 displacement was analyzed. The optimum parameters for WAG flooding were 7 for the number of slugs, 0.3845 PV for the total injection volume, approximately 0.5742 for the gas/water slug ratio, and 120 days for the stewing time. The optimum injection timing of the switching depletion development to the WAG injection was 0.25 years and the earlier switching to the WAG injection after water flooding was more suitable for enhanced oil recovery. The maximal cumulative water injection by water flooding or by WAG flooding yielded the highest oil recovery ratio for homogeneous reservoir. The results do not only play a very important role in optimizing different development schemes but also provide theoretical basis for CO 2 flooding in low permeability hydrocarbon reservoirs.

Description: Experimental results on the performances of ten solar stills with different glass inclination angles are presented. The inclination angles selected are 10–55 in steps of 5°. Results demonstrate that the angles between 30° and 35° may be associated with the least still performance while those between 20° and 25° provide the optimum performance as far as the clean water productivity and cost effectiveness are concerned. Empirical modeling of the still operation produced good agreement with the experimental data.

Description: Water intake structure is an important element technology for small hydroelectric generation. Currently, intake structures with bar screens have been broadly introduced; however, these require constant maintenance to avoid the clogging of bars by dust or gravel. This study considers the optimal structure of bottom intakes by focusing on two criteria: efficient water intake and prevention of clogs by trapping trash. Grating was selected as the intake structure because it is convenient to construct, widely available, and cheaper than other materials. A flume experiment was conducted to examine the relation between the grating structure and the intake efficiency and trash-trapping rate. Results indicate a clear linear relation between the installation angle and water intake capacity. Furthermore, the trash-trapping rate is low for gratings that have high opening area ratios because their surface areas are small and friction resistance is low.

Description: Earth-abundant kesterite Cu 2 ZnSnSe 4 material is a promising candidate for the mass production of low-cost thin film solar cells. However, the synthesis of single-phase kesterite films is especially challenging, since the kesterite single-phase region in the equilibrium phase diagram is very narrow. In this study, the metal composition was varied within the Cu-poor composition range in order to study the presence of Sn-Se secondary phases. Both SnSe and SnSe 2 are found in copper-poor CZTSe absorbers where Zn/Sn   1 because the studied composition range is actually copper-poor zinc-rich and tin-rich. The Sn-Se secondary phases can be detected using X-ray diffraction, a bulk detection method. They are also detected at the absorber's surface by SEM and Raman spectroscopy. Therefore, when the Sn-Se phases are present, at least a part of them is located at the absorber's surface, which is highly detrimental to device performance. Acting as shunting paths, they reduce the device power conversion efficiency and demonstrate an apparent quantum efficiency effect under reverse bias. Removal of these phases from the surface by chemical etching greatly reduces their detrimental influence.

Description: Solar irradiation is the main potential energy source used in various processes. An accurate estimation of solar irradiation becomes a challenge due to the unavailability of weather data in Algeria. Therefore, an operated model can offer an important alternative for calculating the solar irradiation including the minimum of the input data. The present study derives a simple model from a review of our previously published work. It aims to develop a new approach for the estimation of the global irradiation on the horizontal plane only based on the measured sunshine duration. Maps of solar energy are required by many system designs; for this reason, it is mandatory to draw the global solar irradiation maps for Algeria for all types of sky. Algebraic relative errors were used as indicators of the agreement between the experimental and the calculated global irradiation. It has been proved that the highest intensity of the solar irradiation is located around the area of Djanet and Tamanrasset, whereas the less intense area extends from Skikda zone to Annaba, and more exactly in around 7° longitude.

Description: A Luminescent Solar Concentrator (LSC) greenhouse and an identical control greenhouse were constructed with photovoltaic (PV) cells attached to the roof panels of both structures. The placement and types of PV cells used in the LSC panels were varied for performance comparisons. Solar power generation was monitored continuously for one year, with leading LSC panels exhibiting a 37% increase in power production compared to the reference. The 22.3 m 2 greenhouse was projected to generate a total of 1342 kWh per year, or 57.4 kWh/m 2 if it were composed solely of the leading panel of Criss Cross panel design. The LSC panels showed no signs of degradation throughout the trial demonstrating the material's robustness in field conditions.

Description: This paper presents the performance analysis of a new maximum power point tracking (MPPT) algorithm for solar photovoltaic (SPV) system using LUO converter. For effective utilization of the SPV panel, MPPT is essential. Hence, it is significant to simplify the tracking control algorithm with faster response, reduced ripple, higher efficiency, and cost-effective system. The proposed technique performs MPPT using a simple control technique by fine-tuning the duty cycle of the converter so as to make the input resistance of converter equal to the load resistance of the solar panel. Hence, the need for proportional–integral control loop is eliminated. The performance analysis of the proposed MPPT algorithm is compared with an existing perturb-and-observe algorithm in MATLAB simulation and experiment results of the proposed MPPT is implemented with the field programmable gate array controller using LUO converter with 40 W solar panel. From the results, it is proved that the response of the proposed method is faster than the existing perturb-and-observe method under varying solar irradiation conditions for the same step size. The input and output side ripples are considerably low and also the proposed algorithm has higher efficiency and low cost.

Description: The environmental concerns are gaining importance nowadays for power producing companies in the context of clean energy act. The efforts of reducing the harmful emissions beyond a certain level are being made by most of the power utilities in the developing countries. Consequently, the minimization of harmful emissions has also become an important objective function while solving the hydrothermal scheduling problem. The heuristic approaches are considered as potential solution methodologies for non-convex hydrothermal scheduling. This paper presents an Evaporation Rate based Water Cycle Algorithm (ERWCA) for the solution of non-convex Environmental Economic Scheduling of Hydrothermal Energy Systems (EESHES). This algorithm has been evolved from the water cycle nature of raining, formation of streams, and their movement towards the rivers and finally into the sea. ERWCA has been investigated on the standard test system of EESHES with three case studies: (i) Economic Cost Scheduling, (ii) Environmental Economic Scheduling, (iii) Economic Environmental and Cost Scheduling. The comparison of obtained results with the recent results in the literature shows the superiority of ERWCA in terms of both lower fuel cost and fuel emissions. Hence, ERWCA is a worthwhile addition to the algorithms which have successfully solved this complex and combinatorial bi-objective optimization problem.

Description: With the deterioration of the global greenhouse effect, the study of carbon dioxide emissions has received more and more international attention and accurate prediction of carbon dioxide emissions is also important for the formulation of reasonable energy-saving emission reduction measures. In this paper, the genetic algorithm is used to optimize the initial connection weights and thresholds of the traditional back propagation neural network (BPNN) which can give full play to the advantages of the genetic algorithm's global search capacity and BPNN's local search. The data of Hebei province in China during the period 1978–2012 are selected to carry out the carbon dioxide emissions prediction with the established model. In the view of the choice of input variables, the coal consumption, gross domestic product, total population, and urbanization level are examined by Pearson coefficient test. Auto correlation and partial correlation are applied to analyze the inner relationships between the historic carbon dioxide emissions, thus to select the input variables of BPNN. Besides, in order to verify the validity of the built model, the residual auto correlation and partial correlation are done upon the training set. The prediction results suggest the proposed model outperforms the compared models.

Description: A recent trend of the power system is the ever increasing number of distributed generators (DGs) utilizing renewable energy sources, which have output powers that fluctuate due to unpredictable weather and ambient conditions. This causes fluctuations in system frequency and bus voltages, resulting in poor quality power, higher prices for electricity, and increased chances of reverse power flow and voltage collapse. In order to allow higher levels of DG penetration, methods of reducing the effects of fluctuations must be implemented. This paper proposes a method to mitigate these fluctuations using controllable loads such as heat pump water heaters (HPs) and battery storage systems. The HPs are controlled using a decentralized bang-bang (on/off) control based on the cumulative distribution of water temperature of HPs in the local area and the local frequency. Battery systems are controlled using a smart frequency and voltage droop characteristics based control. The decentralized bang-bang control mitigates local frequency fluctuations by increasing active power consumption to lower frequency as well as decreasing active power consumption to increase the frequency. The smart droop characteristics based control applies a commonly used droop characteristics control to voltage and frequency; however, the control system monitors the state of charge (SOC) of the battery system and takes appropriate actions to prevent the SOC from reaching a critical level. The results of simulations show that fluctuations in frequency and bus voltage are mitigated by the application of the proposed control methodologies without adversely affecting the comfort level of consumers.

Description: This paper presents a model-based algorithm for fast tracking of maximum power point of a photovoltaic panel. Parameters of an equivalent circuit have been estimated based on experimental data and characteristic data provided by manufacturer. Since photoelectric current is highly temperature-dependent, the effect of temperature is considered in the model. The proposed method is based on the maximum power point locus of the solar panel. So the tracking speed is much faster than a model-free method. In the suggested technique, the voltage of maximum power point can be determined using output voltage and current of solar panel and the voltage of a point on the maximum power point locus with the same current, in three steps. The main novelty of the proposed model-based method is that there is no need to measure solar radiation. Experiment results are presented and prove the feasibility of the proposed maximum power point tracking method.

Description: A new simulation tool aimed at characterizing the thermal behavior of parabolic trough collectors over a wide range of pressures and gas mixtures in the vacuum chamber is presented in this study. The model is able to accurately predict overall efficiency and heat losses obtained in a number of experimental sources based on both on-sun and off-sun testing, with vacuum in the annulus and no hydrogen. Excellent agreement of the simulations with experiments including different gas compositions, especially with high hydrogen concentrations, is achieved through the use of molecular dynamics results for the determination of the accommodation coefficient of the mixture. Additional experiments were carried out to validate the accuracy of the model over a range of pressures between 10 −4 and 130 mbar. The accurate modelling of rarefied gas dynamics presented here also leads to an excellent agreement between simulations and experiments over the whole pressure range. An accurate determination of the performance in such extreme conditions is critical for an adequate Operation & Maintenance strategy, as well as the development of effective predictive and preventives plans.

Description: Study on how renewable energy use and economic growth interact with each other has been an active area of research. This study examines the impacts of renewable energy production (and consumption) on local economic development and income, for a panel data of the 31 provinces of China over the period 2000–2010 within a multivariable framework. Using regression with panels corrected standard errors, this study investigates the effects of renewable energy use on provincial real gross domestic production and local rural income. It is found that deployment of renewable energy use in rural areas has shown significant positive effects on income increase of rural households. But in general, most renewable energy use has negative impacts on economic growth except hydro power generation, improving the economic efficiency of renewable energy production and adjusting renewable energy related subsidy policies are of prime importance.

Description: There is an imperative need of developing new strategies and models for meeting the swelling demand of electricity in developing nations like India. One of the promising models for this would be Decentralized Distributed Generation (DDG). DDG locates the power generating source closer to the consumer utilizing locally available Renewable Energy (RE) resources, thereby decreasing the Transmission and Distribution (T&D) losses. Despite the numerous advantages with DDG, there have been some minor issues preventing its large scale deployment and utilization in India. This paper discusses the various technology options which can be used for DDG in India and the problems which the Indian power sector has been facing for a long time. This paper aims to provide a complete analysis of the best possible RE based technology options for DDG in India along with their cost of generation, benefits, barriers, applications, and the possible pathways for its deployment.

Description: Energy, especially oil, plays a special and irreplaceable role in the economic development, modern civilization, and social progress. With the rapid growth over the past few decades, China has gradually become a big power in oil consumption. In order to solve the contradiction between supply and demand as well as minimize social costs, it is necessary and useful to forecast the trend of China's oil consumption. In addition, reasonable and effective oil production and scheduling through forecasting progress also makes an important impact on the health economic development, social stability, and sustainable development. However, it is a challenging task to carry out such a forecasting because oil consumption is influenced by a number of factors, such as technology development, economic level, government policy, natural disaster, unexpected politic events, and so on. Therefore, it is difficult to forecast such a complex system with a single traditional model. This paper proposes an improved hybrid method known as GGNN, which combined the grey models, the back propagation (BP) neural network, and the genetic algorithm (GA) to take the advantages of linear model, nonlinear model, and swarm intelligence optimization, respectively. GM (1, 1) and improved grey models including an unbiased GM (1, 1), initial correction GM (1, 1), p value GM (1, 1), and background value GM (1, 1)are applied to capture the linear information. BP is widely used due to its nonlinear mapping capability; in this paper, it is used to capture the nonlinear information. Moreover, the GA is also applied to obtain the optimum weights and thresholds of the GGNN which is made up of all grey models and BP neural model. The superiority of this proposed method is examined by using the historical data of China's oil consumption. Assessment results demonstrate that the proposed method GGNN can improve the forecasting accuracy compared with some other existing methods.

Description: The extraction of maximum power from solar photovoltaic (PV) using Maximum Power Point Tracking (MPPT) methods is a promising research area in the recent past. Many methods including conventional methods, such as Hill Climbing and Incremental Conductance, and methods based on neural network, Fuzzy logic and bio-inspired algorithms, were proposed for MPPT application. However, all these methods suffer from drawbacks such as slower convergence, reduced power output, predominant steady state oscillations, larger memory requirement, and complex structure. Hence, in this paper an attempt is made to enhance existing Particle Swarm Optimization technique by emphasizing proper initial value selection. The key features of this method include the ability to track the global peak power accurately under partial shading conditions with almost zero steady state oscillations, faster dynamic response, and easy implementation. Simulations are carried out for different shading patterns and the results obtained are compared with existing methods. Further, simulation results are validated via experimental values.

Description: This study presents full transient numerical simulations of a cross-flow vertical-axis marine current turbine (straight-bladed Darrieus type) with particular emphasis on the analysis of hydrodynamic characteristics. Turbine design and performance are studied using a time-accurate Reynolds-averaged Navier–Stokes commercial solver. A physical transient rotor-stator model with a sliding mesh technique is used to capture changes in flow field at a particular time step. A shear stress transport k-ω turbulence model was initially employed to model turbulent features of the flow. Two dimensional simulations are used to parametrically study the influence of selected geometrical parameters of the airfoil (camber, thickness, and symmetry-asymmetry) on the performance prediction (torque and force coefficients) of the turbine. As a result, torque increases with blade thickness-to-chord ratio up to 15% and camber reduces the average load in the turbine shaft. Additionally, the influence of blockage ratio, profile trailing edge geometry, and selected turbulence models on the turbine performance prediction is investigated.

Description: This paper reports the effects of engine design and operating parameters such as stroke length, ratio of bore to stroke length, compression ratio, equivalence ratio, engine load, biodiesel percentage, friction coefficient, engine speed and mean piston speed on engine performance and energy losses by experiments and a theoretical model based on the finite-time thermodynamics. In this study, the performance of a single cylinder, four-stroke, direct injection diesel engine fueled with diesel-biodiesel mixtures has been experimentally and theoretically investigated. The simulation results agree with the experimental data. After model verification, parametrical studies have been conducted for various conditions. The results showed that the biodiesel percentage and the cycle pressure ratio affect positively the engine performance. The friction coefficient has negative influence on the engine performance. The effective efficiency decreases with the increasing of the engine load, stroke length, and engine speed but effective power increases with increasing them. The effective power always increases with the increasing mean piston speed. However, the effective efficiency decreases at the constant stroke length condition, as it increases at the constant engine speed condition. The effective power and the effective efficiency increase with increasing equivalence ratio to a specified value and then begin to decrease for constant bore/stroke length conditions. The effective efficiency increases with decreasing equivalence ratio as effective power has an optimum value for constant compression ratio condition. The effects of bore/stroke length change at different conditions. At the constant compression ratio condition, the engine performance increases with increasing ratio of bore to stroke length. They are the optimum values which provide the maximum effective efficiency and maximum effective power at the other conditions. This study also reports the energy losses as the ratio of fuel energy and they are classified as friction losses, incomplete combustion losses, heat transfer losses, and exhaust losses. They are defined with respect to compression ratio. With the increasing compression ratio, the friction losses are constant for constant cycle temperature ratio and equivalence ratio, whereas the incomplete combustion losses increase at a constant cycle temperature ratio condition and are constant at constant equivalence ratio condition. The heat transfer losses increase and the exhaust losses decrease for both the conditions. The presented model could be used to optimize the performance of diesel engines fueled with biodiesel and it can be developed for all kinds of engines running at different conditions with various fuels.

Description: In this paper, the energy efficiency of airlines is measured. Number of employees and tons of aviation kerosene are chosen as the inputs. Revenue tonne kilometers, revenue passenger kilometers, and total business income are the outputs. Capital stock is selected as the dynamic factor. A new model, Virtual Frontier Dynamic range adjusted measure (RAM), is proposed to calculate the energy efficiencies of 22 airlines from 2008 to 2012. In Virtual Frontier Dynamic RAM, the reference DMU (decision-making unit) set and the evaluated DMU set are two different sets to distinguish between efficient DMUs. The results demonstrate the following: (1) Air Greenland exhibits the highest energy efficiency, while the efficiency score of Air France-KLM is at the bottom of the 22 airlines. (2) Aggregate airline energy efficiency consistently increased from 2008 to 2012.

Description: A new type of n-p-n transistor photovoltaic device based on CdS/multi-wall carbon nanotube (MWNT)/n-Si configuration was fabricated in a facile process. CdS quantum dots were deposited on fluorine-doped tin-oxide glass using a chemical bath deposition method, and MWNT film was coated on n-type Si substrate by airbrushing. The materials used for the n-p-n transistor solar cells were characterized by multiple techniques including X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman, Ultraviolet visible (UV-vis) spectrophotometer, and I-V characteristic measurements. The CdS layer acts as a good n-type material for the transistor solar cells. The thickness of the CdS layer can be controlled by the chemical bath deposition time to achieve different photovoltaic responses. I-V characteristic measurements show that the efficiency increases with increasing the thickness of the CdS thin layer. Compared with the tandem solar cells based on (p/n)–(p/n) semiconductor junctions, our n-p-n transistor solar cell has a simple structure without using tunnel junctions or wafer bonding schemes for interconnecting the cells.

Description: This study proposes a new method for direct generation of synthetic wind power time series for a wind farm. The method combines the random nature of wind with the operational information of the wind turbines (i.e., failure and repair rates). It uses chronological or sequential Monte Carlo Simulation instead of non-sequential one due to its usefulness and flexibility in preserving statistical characteristics of the chronological processes. The validity of the synthetic values generated by the proposed method and the conventional Markov Chain Monte Carlo methods is compared with the measured data in terms of average and variance values, Probability Distribution Function, and Auto-Correlation Function. Due to increasing interest in the use of the storage system in paralleling with wind power generation, a practical application of the proposed method is also included. Optimal sizing of various energy storage technologies is obtained through a cost-benefit analysis in a typical Micro-Grid.

Description: Food waste along with its two individual components, noodle waste and rice waste, were tested for bio-hydrogen production by using sludge as a source of mix consortia of Clostridium under different physical conditions (pH 5, 6, and 7; temperature 37 °C and 55 °C). The increase in pH increased the bio-hydrogen yield for all tested wastes, whereas an increase in temperature increased the bio-hydrogen yield just for food waste. The highest experimental yield of 115.76 ml/VS removed was produced in the mesophilic noodle waste reactor at pH 7. The drop in pH from 7 to 4.8 ± 0.2 was found optimum for bio-hydrogen production for all tested wastes under mesophilic as well as thermophilic conditions. Most of the hydrogen production was observed within 72 h of incubation, which can be used as the optimum bio-hydrogen production period for food waste. The bio-hydrogen yield, final volatile fatty acids (VFA), and glucose consumption at 72 h were analyzed with the help of the response surface methodology. The resultant plots represented an increase in glucose consumption with the increase in pH from 5 till pH 6 ± 0.5, after which glucose consumption started to decrease up to pH 7. The final VFA represented a similar trend as that observed for glucose except that the change in VFA production was observed due to the temperature and transition was observed at 47.5 ± 1.5 °C for food waste as well as for noodle waste.

Description: A new approach based on the use of external frequency converters for Nd:YAG solar pumped lasers providing effective conversion of solar-to-laser power is proposed. The possibility of a more than four-fold increase in Nd:YAG solar pumped laser efficiency is shown by the simulation calculation method.

Description: This paper uses monthly data for the time span 2006:M01 to 2014:M06, to study the relationship between electricity generation regimes, both ordinary and special, and economic activity in Portugal. An autoregressive distributed lag bounds test approach is pursued to analyse the short- and long-run dynamics between renewable/non-renewable electricity sources and industrial production. Results show that both ordinary thermal sources and hydro sources are driving forces behind electricity from the special regime. Economic activity is stimulating the special regime, but, conversely, the special regime hampers the growth of industrial production. It is demonstrated that a crucial role is being played by large-scale hydropower in accommodating the special regime in the electricity mix. This source is causing economic activity, while at the same time, backing up new renewable sources.

Description: CuZnS is a new promising material in thin film photovoltaics which is earth abundant and eco-friendly. Its electrical and optical properties can be controlled by varying atomic ratios of Copper and Zinc, so as to use it as absorber or window layers. Type of conductivity of this material can also be changed from n to p by adjusting Cu/Zn value. In the present work, we report improvement of cell parameters of CuZnS/In 2 S 3 hetero junction considerably from our own earlier reported values just by increasing Cu to Zn ratio in CuZnS. Current density increased from 5.4 mA/cm 2 to 10.7 mA/cm 2 , thereby enhancing conversion efficiency from 1% to 1.95%. Results are explained on the basis of improvement of multiple band structure.

Description: Lithium iron phosphate (LiFePO 4 ) batteries are widely used as power batteries for electric vehicle applications. For safety issues, it is important to estimate the State of Charge (SOC) of a battery accurately. The improved Thevenin equivalent circuit model is established according to the characteristics of the LiFePO 4 battery, and the model parameters are identified by experimental testing. Furthermore, a novel algorithm of SOC online estimation is proposed, which combines the open-circuit voltage method, ampere-hour integration, and Kalman filtering. The simulations and experimental results show that the improved Thevenin equivalent circuit model can enhance the accuracy of SOC estimation. This proposed algorithm could estimate the SOC precisely even with inaccurate initial values and current measurement errors and distinguish the performances between the batteries. The performance of the proposed SOC estimation method when the voltage sensor is unavailable has been investigated and presented as well. From the characteristics mentioned above, this novel approach is able to guarantee the reliability and safety of the batteries.

Description: The availability of reasonably accurate global solar radiation data is vital for the success of any solar project. However, only a few meteorological stations around the world capture these data as a result of the high cost of measuring equipment and the lack of technical capability in calibrating them. In an attempt to resolve this challenge, engineers and researchers have developed various alternatives to generate the data. In this paper, we surveyed the methods used in generating synthetic global solar radiation with a view to classifying them and bringing out the advantages and the challenges of each. This could motivate the development of a new set of robust prediction techniques that combines the strengths of different existing models for prediction purposes. The various prediction techniques can be generally classified into four categories: the regression techniques, the artificial intelligence methods, the statistical approaches, and the satellite imagery techniques. It is shown from the review that the regression techniques are widely used for the prediction of global solar radiation because of their simplicity. However, their accuracy depends on the completeness of the meteorological data employed in predicting global solar radiation. The statistical methods are based on the assumption that data have an internal linear structure that can be identified and used for prediction purposes. However, it is observed in the literature that the techniques, especially the time series techniques, are generally not good for short time prediction as the error in the prediction of the next value in a series is usually large. Satellite imagery is desirable if surface data for location does not exist. Generally, the use of surface measurements together with a cloud index based on satellite imagery is encouraged to increase the accuracy of prediction. Artificial intelligence methods have been generally favoured for their capability to handle complex relationships between the global solar radiation and the other meteorological data, and as well provide better accuracy and efficiency. This paper is important to engineers and researchers who are interested in the global solar radiation prediction methods.

Description: When the photovoltaic (PV) system is fully illuminated, the voltage-power characteristic of the array has one maximum power point (MPP). This point can be tracked by conventional maximum power point tracker algorithms. On the other hand, in partially shaded PV, the voltage--power characteristic has only one global MPP (GMPP) and multiple local MPPs. It is important to operate the PV system at GMPP for achieving optimal operation. This paper presents the application of two novel meta-heuristic optimization algorithms to extract GMPP from the PV system under partial shading conditions: The mine blast algorithm (MBA) and the teaching learning based optimization algorithm (TLBO). A proposed constrained objective function representing the PV array output power is also presented. Different patterns of shadows that strike the PV array surface are studied. The studied patterns are uniform ones, changing from 0% to 375% with steps of 25%, and non-uniform patterns with different locations of GMPP. The obtained results from each algorithm are compared, and the results show that the MBA based tracker is more reliable, more efficient, and superior to TLBO. A comparison with fuzzy logic control and adaptive neuro-fuzzy and particle swarm optimization based trackers has been done. The results ensure that the reliability of the MBA in solving the problem is addressed.

Description: Aiming at the multiple peaks phenomenon on the power-voltage characteristic curve of photovoltaic (PV) array under partially shaded conditions, this paper proposes a fast global maximum power point tracking method based on sliding mode control (SMC). First, according to the operating characteristics of PV arrays, a reduced scanning range is adopted to avoid large power fluctuations and the optimal scanning direction of global maximum power point (GMPP) is determined to avoid the repeating scanning of the PV curve, both of which reduce the scanning time greatly. Second, during the scanning and tracking process, SMC is introduced to move the operating point quickly to the reference value, which improves the scanning speed further. Finally, when the operating point is close to the GMPP, the control mode is switched from the SMC based tracking control to the SMC based maximum power point tracking control, which quickly stabilizes the operating point of the PV array at the GMPP, reducing the power ripple during steady-state operation. Furthermore, the proposed method is independent of PV parameters, due to the new open circuit voltage detection method proposed in this paper, which does not occupy extra time. Simulation and experimental results validate that the proposed method can guarantee accurate convergence to the GMPP with fast tracking process and low energy loss under partially shaded conditions.

Description: Geothermal heat pumps have several advantages over conventional heating and cooling systems. They can operate in both winter and summer, have high efficiencies, and do not directly emit any greenhouse gases during operation. Investors (in developing countries) can use Clean Development Mechanism as a source of financing for new or existing renewable energy facilities by selling Certified Emission Reductions credits (CERs), which represent the amount of CO 2 emission (1 CER = 1 tCO 2 eq) that is avoided using renewable energy. The aim of this paper is to analyze the possibility of CO 2 reduction by using geothermal heat pumps for fossil fuel displacement with applying Clean Development Mechanism. Results have shown that by using geothermal heat pumps during a 7-year crediting period, the estimated emission reduction would be 79.45 tCO 2 (equal to 80 CERs), enabling the investor to achieve profit from selling 80 CERs and thus helping to fund the proposed project activity. Three main factors which influence the amount of CO 2 reduction have been identified: carbon-dioxide emission factor for electricity source, efficiency of technology used for baseline scenario, and coefficient of performance (COP) of heat pumps.

Description: The utilization of lignocelluloses for biogas production is limited for several aspects, and an efficient pre-treatment is essential to increase the enzyme accessibility of cellulose. This research focused on the mechanism of biogas production and biodegradation properties under the treatments with different acid agents, including sulfuric acid (H 2 SO 4 ), acetic acid (CH 3 COOH), and phosphoric acid (H 3 PO 4 ). The H 3 PO 4 pretreated corn stover was then co-digested with cow dung in a pilot test to investigate the performance of acid pretreatment in practice. The results showed that the main compositions of corn stover were cellulose, hemicellulose, and lignin, and their proportions in the corn stovers were increased after the acid pretreatments. This hence increased the final biogas yields (up to 40.75%), methane content, and promoted the biodegradation process. More significantly, the acid pretreatments delayed the appearance of the peak value of the biogas yield for 3 to 8 days depending on the acid concentrations. This study proposed that the dilute weak acid pretreatment, especially H 3 PO 4 pretreatment, efficiently enhanced the biogas production by increasing the degradation of hemicellulose. Further on, the H 3 PO 4 pretreatment also improved the stability of fermentation, which would benefit the biogas generation in practice. This research contributes to a better understanding of the mechanism of acid influence on enhancing the biogas generation and substrate biodegradation, and provides pratically sound guidance for reclamation of lignocellulosic materials.

Description: A 1 kW e integrated auxiliary power unit (APU) system consisting of an autothermal reformer and a solid oxide fuel cell (SOFC) unit, as well as balance-of-plant components, was designed and analyzed. A relatively easy-to-approach SOFC model was developed in order to conveniently calculate V-I and P-I curves and the system's net efficiency at different operating conditions. The effects of steam to carbon and oxygen to carbon ratios in the reactants, channel dimensions of the SOFC unit, and hydrocarbon fuel types on the integrated APU system's performance were discussed. Five hydrocarbon fuels including diesel, Jet-A, gasoline, ethanol, and methanol were studied as fuel sources for the APU system. The system's net efficiency around 35% is possible for all the tested fuels in the current density range of 100–400 mA/cm 2 . The APU system was also verified to be thermally self-sustainable in the steady state operation by a thermal management analysis.

Description: This study describes a method to quantify the visual impact of an offshore wind farm, as seen from the coast. In brief, the method involves distinguishing between the visual impact due to the intrusion in the observer's vision field and the un-aesthetic effect of the arrangement unevenness. Both parameters, visual intrusion and unevenness, can be quantifiable; therefore, a final indicator for the visual impact of the wind farm can be calculated for a specific wind farm layout. Two approaches are presented to calculate the visual intrusion, which give rise to similar results. The method has been programmed and included in an application that has been tested with two known wind farm layouts, showing a complete coherence of the results given by the method. This method provides the designer with a tool that allows him to take into account the estimated visual impact of a wind farm under study. If an algorithm is used to look for the optimum location/layout for an offshore wind farm, its programmer can include this method in order to obtain a trade-off between maximum profitability and minimum visual impact.

Description: The main aim of this paper is to review different optimization techniques and to describe the importance of the Honey Bee Mating Optimization (HBMO) Algorithm for the modeling of fuel cells. HBMO algorithm is a nature inspired one that simulates the process of real Honey Bee Mating and the natural foraging behavior of honey bee has been discussed. The objective function has been framed for the static modeling of proton exchange membrane fuel cell by considering certain constraints. HBMO is implemented to optimize the appropriate parameter and it is mainly dependent upon the parameter decisions; therefore, it results in improved computation. The proposed HBMO is compared with the conventional algorithms like simulated annealing, pattern search, particle swarm, and genetic algorithm reported in the literature. By using the HBMO technique, the electrical, fuel processor, hydrogen, oxygen, and water response times are analyzed and compared with the other algorithms. The results are validated. The proposed HBMO algorithm surpasses the above mentioned optimizers in terms of accuracy.

Description: This study aims to analyze the relationship between carbon dioxide (CO 2 ) emissions, economic growth, and coal and oil consumption in Brazil, Russia, India, China, Turkey, and South Africa by using the bounds test approach autoregressive distributed lag (ARDL) over the period from 1969 to 2011. According to ARDL analysis results, it is determined short-run and long-run relationships among selected variables. Three long-run estimators: ARDL cointegration, dynamic ordinary least squares, and fully modified ordinary least squares are utilized to test the robustness of the estimation results. The Granger causality and the forecast error variance decomposition approaches indicate the evidence of a causal relation between variables. According to empirical results, there are the evidence of a uni-directional Granger causality from real gross domestic product (GDP) to carbon dioxide (CO 2 ) emissions in analyzed countries, uni-directional causality from coal consumption to carbon dioxide (CO 2 ) emissions, uni-directional causality from oil consumption to carbon dioxide (CO 2 ) emissions in China, India, Turkey, and South Africa and bi-directional causality in Brazil and Russia. Meanwhile, there is bidirectional causality from GDP to coal consumption, from coal consumption to oil consumption for Brazil, Russia, China, Turkey, and South Africa. India's causality results reveal a bidirectional causality from GDP to coal consumption, oil consumption, and carbon dioxide (CO 2 ) emissions, and the results of forecast error variance supported the results of the causality test.

Description: A thin cupric oxide film (CuO), straddled with graphene nanoparticles, is proposed as a promising absorber layer for solar cell application. The influence of the graphene nano-particles on the optical, electrical, and photovoltaic properties of the CuO thin film is investigated in detail. Graphene nano-particles incorporated CuO (G-CuO) film, grown via sol-gel deposition, shows a reduction in the optical transmittance and reflectance, and an enhancement in its electrical conductivity. Photovoltaic properties, investigated through a p -(G-CuO)/ n -Si heterojunction cell, shows a significant increase in short circuit current from 0.12 mA/cm 2 to 0.82 mA/cm 2 . The fill factor was also found to increase to 40% from 20%. The significant improvement in efficiency of the G-CuO solar cell is attributed to the synergetic effect provided by graphene in enhancing the absorption of visible light and increasing its electrical conductivity, while concurrently suppressing charge recombination in the bulk semiconductor.

Description: The paper estimates solar radiation in the Southern areas of Pakistan using the climate data of thirty years (1981–2010) for 25 meteorological stations located in the three provinces of Pakistan, i.e., Baluchistan, Punjab, and Sindh. For this purpose, five different radiation models are designed: Sunshine hour-based model, Temperature-based model, Cloud-based model, Meteorological parameters-based model, and Meteorological and Geographical Parameters-based Model. The forecasting efficiency of these models is evaluated using mean predicted errors and Theil inequality coefficient. The results reveal that the Meteorological and Geographical parameters-based models are the most accurate methods for estimating solar radiation in Pakistan. Forecasting efficiency results show that the estimates of solar radiation of all the models is much better for Baluchistan as compared to Punjab and Sindh.

Description: Photovoltaic companies have been developing very rapidly in China and facing huge financial crisis as well. By adopting the Z-score and multi-regression models, this paper evaluated the financial risks of China's 57 solar photovoltaic companies, in an attempt to reveal the relationships between managerial power, ownership concentration, and their financial risks. Empirical results show that the expansion of photovoltaic companies' managerial power significantly increases the financial risks of these companies. More specifically, (1) combining board chairman and the Chief Executive Officer (CEO) increases their financial risks; (2) the size of the board of directors and the tenure of the CEO have positive correlations with their financial risks; and (3) the percentage of management shareholdings and the degree of ownership concentration have negative correlations with their financial risks. Management implications are proposed accordingly based on the findings of this study.

Description: Conventional methods for solving distribution systems planning (DSP) problem are related to the expansion of distribution systems such as substation reinforcement and feeder replacement. Nowadays, distributed generations (DGs) in various types are a new option for DSP. This paper presents a new approach to solve the DSP problem including DGs with respect to the reliability of the system. The impact of different types of DGs in order to improve the system reliability are modeled and studied by the adequacy transition rate using the Markov model. The objective functions of this optimization problem are power losses, DGs installation and operation cost, reliability indices such as energy not supplied, average interruption frequency, and average interruption duration. Since this optimization problem has a nonlinear complex nature, classical mathematical methods cannot guarantee to achieve the global optimum solution. To solve this problem, a fuzzy interactive multi-objective particle swarm optimization is developed based on Pareto solutions. The model resolves decision variables as follows: location, size, and type of the DG units. The results on IEEE 34-bus distribution system show the effectiveness of the proposed method rather than previous works for reliability assessment.

Description: This paper presents a model based method to estimate the internal core temperature of a service power cable subject to intermittent loading. The estimation is then used to control the loading so that the cable can be safely utilized to the limit of its capability. The method considers the temperature dependence of the cable resistance and is insensitive to the variations in the environment. The model is backed by laboratory experiment and the effectiveness of the dynamic rating approach is evaluated by simulation.

Description: The effect of chemically synthesized activated carbon (AC) on the performance of microbial fuel cell (MFC) was investigated in this study. Coconut fiber was used as a source material for synthesizing the AC. The AC with different ranges (5, 10, and 15 mg/cm 2 ) was coated on the anode electrode surface to investigate and compare the performance of MFC with the control electrode (plain surface). The experimental results showed that the AC-5 (5 mg/cm 2 ) coated electrode produced a peak power density (5.8 W/m 3 ) which was higher than the control (plain) electrode (3.8 W/m 3 ). The MFC performance in terms of power density and chemical oxygen demand (COD) removal efficiency was increased with increasing loading quantity of AC. When an AC-15 (15 mg/cm 2 ) coated was electrode used in the MFC, the highest power density of 9.5 W/m 3 with a COD removal efficiency of 74.8% was observed. Cyclic voltammetry analysis visualized the clear enhancement in electrochemical activity with an AC coated electrode. The effect of wastewater COD concentration on the performance was also investigated. The AC derived from coconut fibers can be considered as a biocompatible material to enhance MFC performance.

Description: Most of the photovoltaic (PV) solar systems track none or only basic monitoring data, thus the investor has no or limited information about the performance, quality, and reliability of a PV system. In this paper, we report on a methodology to evaluate a large number of PV systems on a regional or even countrywide level. The methodology is based on an apparent performance ratio, a factor close to the temperature compensated performance ratio, although based on solar irradiation data from the closest meteorological station. The methodology is compared to a more detailed evaluation procedure and a comprehensive evaluation of a PV system where all the required—both electrical and meteorological—data are monitored. The results confirm that the apparent performance ratio is very similar to the temperature compensated performance ratio of a PV system.

Description: Data Mining techniques have been applied to data collected from a 222 kWp CdTe (Cadmium Telluride) photovoltaic (PV) generator to predict faults or special conditions that occurs due to shadows, bad weather, soiling, and technical faults. Five types of errors have been distinguished and its impact on the PV system performance has been evaluated. Up to date, this computing approach has needed the simultaneous measurement of environmental attributes that an array of sensors collected. This study presents a model to assess the state of the PV (photovoltaic) generator and an algorithm that classifies its state without measuring ambient conditions. The result of a 222 kWp CdTe PV case study shows how the application of computing learning algorithms can be used to improve the management and performance of the photovoltaic generators and underlines the environmental parameters as clue attributes to find faults during the PV performance. Although the application of this method requires computational effort, the result deals with an easy-implementing decision tree, which can be installed in small device.

Description: The configuration of hybrid energy systems has a great influence on the cost of generated energy from the system. This paper introduces a design, simulation, assessment, and selection of optimum autonomous hybrid renewable energy configuration out of three different configurations. The proposed hybrid system contains photovoltaic (PV), wind, diesel, and battery energy systems. A new computer program has been designed to simulate different configurations of hybrid energy systems. A genetics optimization smart technique using a genetic algorithm has been used to calculate the optimum sizing for each component at different configurations of the hybrid system for minimum cost and highest reliability. The optimum penetration ratio of renewable energy systems (PV and wind) will be selected according to the lowest price. Actual data for one remote site in Saudi Arabia has been used in the input data of this computer program. Sensitivity analysis has been carried out to show the conditions for selecting any configuration under study. The results obtained from this study can help researchers, designers, and decision makers to answer many open questions regarding the design and installations of hybrid renewable energy systems.

Description: This research describes a novel system of four Savonius wind rotors, aligned in parallel. A solar panel system, generating power by solar energy, was positioned in front of the parallel system to guide the airflow impinging on the rotors. This array was installed in rural areas to generate electric power. The effect of the solar panel deflector arrangements, used to guide the air stream, was investigated. This type of plant development has not previously been examined. We employed a computational fluid dynamics software, Fluent, to analyze the flow fields and system performance prior to experimentation, then compared these simulations to our experimental data. The parameters studied include wind velocity, wind direction (with/without solar panel deflector), and the rotational speed of the rotors to identify the relationship between the tip-speed ratio (TSR) and power coefficient (Cp). For the numerical simulation results at TSR 0.8, the maximum Cp value of the parallel system without a solar panel deflector was 0.289, whereas at the optimal spacing between the parallel systems with a deflector (50 cm), the Cp was 0.389. This represents a difference factor of 1.35 between the two Cp values. The velocity vector distribution showed that the deflector could guide the airflow to impinge on the rotors from below, gaining extra wind power. The experimental results show that the wind velocity and rotational speed of the wind rotors exhibit large fluctuations in open fields. To combat this, experiments were repeated in both day and night conditions, in different seasons, to gather a range of Cp and TSR values. The average measured wind speed was 6.99 ± 1.52 m/s. Four Savonius wind rotors in a parallel system can generate 8.25 kW h of energy per day, with an optimal power generation efficiency of 20.7%. Our 3-kW hybrid wind and solar system, which used optimal simulation conditions to determine its experimental design, can generate 14.55 kW h of power per day, with a corresponding optimal power generation efficiency of 21.7%. Our measured Cp curve shows that a deflector can improve the system performance by up to 10.1%.

Description: Due to environmental issues and the upward trend of fossil fuel prices, the study of renewable energy (RE) based generation and their effects on the electrical system has become an important part of the government's energy policies and university projects. In RE generation, as solar photovoltaic (PV) systems are modular, silent, and transportable and demonstrate ease of installation, they have attracted a greater amount of attention specifically in those areas which receive considerable average solar radiation per day such as Malaysia. However, connecting solar PV farms to the grid like any other distributed generation (DG) units poses serious issues which arise in the distribution network. This paper presents a novel fault location algorithm based on the recording of short circuit power values at the primary substation of unbalanced radial distribution networks including PV systems. The recorded values are evaluated by a designed and tuned multi-layer feed forward neural network and the fault distances from the source are estimated accordingly. In order to highlight the accuracy of the presented method, the scenario is also repeated by recording the peak values of short circuit current which have been mostly used in the published intelligent fault location studies and the obtained results via two different values are compared with each other. The results reveal that the presented algorithm using a small scale input set is able to precisely locate different fault types in the unbalanced distribution networks including DG units.

Description: Herein, we reported a well-controlled hydrothermal synthesis of Co 3 O 4 nanowires using CoSO 4 as a cobalt precursor and glycerol as a morphological directing agent. Scanning electron microscopy was employed to observe the growth of nanowires. As an important synthetic parameter, reaction time is spanned from 4 to 24 h, which played an important role in the morphology and properties of materials. When the reaction time was 4 h, the resulting Co 3 O 4 nanoparticles assembled into some short nanorods. While increasing the reaction time, the nanorods grew into long nanowires with large aspect ratio, and then attached into bundles when the reaction time was extended up to 24 h. Electrochemical characterization shows that Co 3 O 4 nanowires prepared by hydrothermal reaction for 12 h exhibited the highest catalytic activity for oxygen evolution reaction (OER) among all synthesized nanowires and nanoparticles using the similar method. The enhanced OER activity of the 12 h-prepared Co 3 O 4 nanowires should be attributed to the increased electroactive surface area because observed from the cyclic voltammogram, the 12 h-prepared Co 3 O 4 nanowires possessed the highest surface area among all tested samples. It was also illustrated that there existed a close correlation of the OER catalytic activity with the transition of oxidation state and the density of activity sites of the catalyst exposing to the electrolyte solution during the electrolysis. Though both Co 3 O 4 nanowires and nanoparticles exhibited a considerable loss in OER activity during the stability testing, after polarization for 4 h at 1.7 V (versus a reversible hydrogen electrode), the Co 3 O 4 nanowires still produced the higher catalytic current than that of the Co 3 O 4 nanoparticles showing a slightly higher stability than the particles because of the nanowire structure.

Description: During scale-up of microbial fuel cell (MFC), a proportional increment in power does not usually occur determining the importance of maximum possible anode chamber volume ( V an ) to exploit electrogenesis and achieve maximum energy recovery. A systematic approach is proposed for determining the optimal single anode chamber volume and the minimum anode surface area ( A an ) of an MFC. The optimal anode chamber volume was estimated based on the substrate required to produce a defined maximum current that is likely to be produced from the basic electromotive force equation. The A an was obtained by considering the area required for biofilm formation, the substrate utilization rate by electrogens, the MFC polarization curve, charge transfer kinetics and mass transport overpotential. Based on the theoretical bio-electrochemical considerations, the maximum V an and minimum A an required for each anode chamber are proposed for electrogenesis to dominate. A single V an of a few litres will only be optimal for treating wastewater. With wastewater of chemical oxygen demand (COD) of 5 g l −1 and considering a Coulombic efficiency and a COD removal of 80% each, a V an of 2.02 l is optimum for a single anode chamber to produce a current up to 750 mA; which is the maximum possible current estimated from electromotive force equation. Any additional volume provided will leave the substrate unused by electrogens and encourage methanogenesis. Adopting this volume for each anode chamber in a MFC stack is recommended for treating wastewater under the assumptions of the analysis. Charge transfer kinetics dominate the minimum A an required, which satisfies the area required for biofilm formation, MFC polarization, and mass transfer. The minimum A an should be provided in a MFC to ensure the dominance of electrogenesis.

Description: This paper introduces an optimal design method of swept blades for Horizontal Axis Wind Turbines, which comprehensively takes both annual energy production (AEP) and blade root loads into account. The start position of sweep curve, tip sweep, and the first-order derivative of the sweep curve at tip are design variables, Maximum AEP and minimum blade root loads are optimization objectives; meanwhile, non-dominated sorting genetic algorithm II is applied to find the optimal result. The sweep curve is modeled by a three order polynomial, while power coefficient C P and AEP are calculated by blade element and momentum method, and blade root loads are evaluated by GH Bladed. A sweep curve design case is demonstrated in this paper. AEP, extreme and damage equivalent load (DEL) of blade root M y of the optimal result, is evaluated. By adding the backward sweep curve to the baseline blade, AEP is increased by 1.34%, M y extreme load is significantly dropped, M x extreme load is almost the same as the baseline, while M z extreme load is increased in low wind speed. Furthermore, all of the DELs of M x , M y , and M z are reduced except at the wind speed range near rated wind speed. This was due to the same controller parameter as the baseline.

Description: A numerical simulation for the wake deviation effect in a wind farm is carried out using the full rotor model of the National Renewable Energy Laboratory 5 MW wind turbine. The downstream wind turbine decreases its performance significantly due to the upstream wake interference. To reduce this effect, a control strategy based on the yaw angle is adopted to skew the trajectory of an upstream wake, thereby avoiding the downstream wind turbine and improving the efficiency of whole wind farm power generation. In this paper, the commercial CFD software STAR-CCM+ was used to simulate the wind farm which contains two tandem wind turbines operating in the atmospheric boundary layer condition. The results show that the wind farm's total power increases when the upstream wind turbine applies a yaw angle intentionally. According to the analysis of velocity contours, wake centerlines, and vortex structures, a counter-rotating blade tip vortex pair is observed to be responsible for the wake deviation effects concentrated on the hub height, which reveals that the influence of a yawed wake on the downstream wind turbine may be slightly underestimated.

Description: Microalgae such as Chlorella vulgaris contain sufficient fatty acids to suggest their use as feedstocks for biodiesel production. Their capacity to remove nitrogen, phosphate, and other nutrients from a culture medium makes them a potentially useful element in urban wastewater treatment systems. A two-stage process was used to grow Chlorella vulgaris under mixotrophic and autotrophic conditions in artificial wastewater and urban wastewater media. Growth rate, nutrient removal, and lipids accumulation were quantified. Initially, the media were nitrogen-enriched (90 mg −1 ; Stage I), and then nitrogen limited (30, 20, and 10 mg l −1 ; Stage II). Growth was not inhibited under either of the culture conditions, and nitrogen uptake rates were above 90%. Total organic carbon removal was higher (56.2%–86%) under mixotrophic conditions than under photoautotrophic conditions (15.2%–69%). Lipids productivity was 2.7 times higher under mixotrophic conditions and nitrogen limitation than under photoautotrophic conditions and nitrogen limitation. Palmitic acid and linoleic acid accounted for 25.0% of total fatty acids contents, which is an adequate profile for biodiesel production. Culture of C. vulgaris in urban wastewater can improve the efficiency of nitrogen and total organic carbon removal, and water reuse, while simultaneously producing algal biomass with sufficient lipids content and an acceptable fatty acids profile for use as a biodiesel feedstock.

Description: Renewable energy sources (RES) can be a significant source of profit. However, different RES projects can bring various benefits to their investors, raising the question—Which RES project to select? The objective of this study is to provide answers to two questions: (1) Which factors/criteria should be used in the RES project selection procedure; (2) Which RES project should the investor select out of a group of prospective projects? The study was conducted in a company operating in the energy sector in Serbia. In order to find answers to the above-mentioned questions, the study employed a hybrid methodology integrating the SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis and the Analytical Hierarchy Process (AHP). First, the Company's management defined the goal and project alternatives. The goal was to select an optimal RES project suitable for the specific circumstances in the Serbian energy sector, and also for the Company's potentials. The alternatives included: a hydro energy project, a solar energy project, a wind energy project (WEP), and a biomass energy project. Then, the decision-making group was formed, consisting of four company's experts (hereinafter collectively referred to as “the decision-makers”), of different professional backgrounds and affiliations. Second, the decision-makers employed SWOT analysis on the RES projects in Serbia to obtain the decision-making criteria. The decision-making procedure has to be based on 20 SWOT factors. However, each criterion is not of equal importance for investors. This shortcoming has been overcome by introducing AHP. Pairwise comparison was performed using the Expert Choice 2000 software. According to the results, the top-ranking project is the WEP.

Description: Biodiesel derived from simultaneous esterification and transesterification of waste cooking oil has been attracting consideration as a replacement green fuel for diesel fuels, as it is economically feasible and circumvents the issue of energy versus food, which is estimated to take place with current biodiesel production techniques. In this optimization study, iron-manganese doped zirconia-supported molybdenum oxide catalyst has been prepared and used in the synthesis of waste cooking oil based biodiesel by a simultaneous esterification and transesterification method. The catalyst is prepared via an impregnation method and consequently characterized by XRD, TEM, TGA (thermogravimetric analysis), TPD-NH 3 , and Brunauer–Emmer–Teller (BET) techniques. The simultaneous process for biodiesel production has been assessed and improved statistically via response surface methodology in combination with the central composite design. It has been established that the process for synthesis of waste cooking oil based biodiesel achieved about 96.8% biodiesel yield at a best condition of 200 °C, waste cooking oil/ methanol molar ratio of 1:30 and 5.0 wt. % as loading of the catalyst. The highest ester yield of 96.8% has been obtained due to the improved physicochemical properties of zirconia-supported molybdenum oxide catalyst which accesses diffusion of the reactants to the active sites.

Description: The erbium oxide based water splitting (Eb-WS) cycle was thermodynamically studied by using the HSC Chemistry software and databases. The first step of the Eb-WS cycle involves thermal reduction of E r 2 O 3 , whereas the second step corresponds to the production of H 2 via water splitting reaction. Equilibrium compositions associated with the thermal reduction and water splitting steps were determined by performing HSC simulations. Influence of partial pressure of oxygen ( P O 2 ) in the inert purge gas on thermal reduction temperature ( T H ) and equilibrium compositions associated with the solar thermal dissociation of E r 2 O 3 was identified. Furthermore, energy and exergy analysis of the Eb-WS cycle was carried out to estimate the cycle ( η c y c l e ) and solar-to-fuel conversion efficiency ( η s o l a r − t o − f u e l ). Simulation results indicate that the η c y c l e and η s o l a r − t o − f u e l of Eb-WS cycle increase with the decrease in T H . Also, the η c y c l e and η s o l a r − t o − f u e l can be increased further via the recuperation of the heat released by the water splitting reactor and the quench unit. The η s o l a r − t o − f u e l of Eb-WS cycle was observed to be equivalent to that of ceria cycle.

Description: With rapid increasing of wind power generating capacity, the influence of wind power on power system planning and operation becomes more and more severe. Wind power time series modeling is the basis of evaluating the influence accurately of wind power on power system, which is very important to annual wind power dispatch planning and installed capacity optimization. In this paper, a novel modeling method of wind power time series based on the definition and identification of the fluctuation process is proposed. The Gaussian function is proved to be a good choice to sketch the fluctuation process and the visualization self-organizing map clustering algorithm is used to classify the fluctuation process. The expected wind power time series is achieved by studying the statistical feature of the sample data and by analyzing the transfer characteristic of the fluctuation processes. The comparative analysis on the statistical feature of the generated time series and the sample data is presented. In terms of the 15 min and 1 h variation, autocorrelation function, monthly mean and hourly mean of the generated wind power, the proposed method in this paper are better than the commonly used Markov Chain Monte Carlo method. The proposed method can keep the variation and process characteristic of the wind power, which is very important for the study of stochastic planning and operation of the wind power in power system.

Description: This paper describes a modelling approach suitable for assessments of future scenarios for renewable energy integration in large and interconnected power systems, based on sequential optimal power flow computations that take into account variability in power consumption, in renewable power production, energy storage, and flexible demand. The approach and the implementation as an open source Python package called Power Grid And Market Analysis is described in some detail. Particular emphasis is put on the modelling of energy storage systems, and the use of storage values as a means to define storage utilisation strategies. A case study representing a 2030 scenario for the Western Mediterranean region is then analysed using this approach. The main aim of this study is to assess the benefit for the system of adding flexibility in terms of storage associated with concentrated solar power or flexible demand. But other results are also presented, such as the resulting energy mix, generation costs, price variations, and grid congestion.

Description: This paper reports an improved acoustic energy harvester with a tapered Helmholtz cavity. The harvester consists of a bimorph piezoelectric composite plate and a Helmholtz resonator (HR) with a tapered cavity. The architecture, operational mechanism, fabrication, and characterization of the harvesters are described. The harvesters are tested under sinusoidal sound pressure levels (SPLs) inside a lab as well as random SPLs in a real ambient acoustical environment. When a harvester with a tapered HR and without proof mass attached to its piezoelectric plate is characterized at a sinusoidal SPL of 130 dB, a maximum power of 90.6  μ W is delivered to 1 kΩ load. In comparison, a similar harvester with a cylindrical shape HR produced a maximum power of 51.4  μ W under the similar acoustic conditions. It is found that 76.26% increase in power is achieved with the tapered cavity for the HR. Furthermore, due to the attachment of a proof mass (0.84 g) with the harvester, its power production capability is further increased by 103.3%, from 90.6 to 184.18  μ W. Moreover, in a real environment, the maximum voltage amplitudes of about 260 and 280 mV are produced by the harvester when placed in the surrounding of a motorbike and domestic electric generator, respectively.

Description: Using a sample of 18 prefecture-level cities in Henan province, this study explored the regional allocation of energy intensity reduction targets from the following three viewpoints: equity principle with common but differentiated responsibilities; intensity reduction target fulfillment; and economic differences and reduction potential among regions. Based on a preliminary decomposition model, an analytic hierarchy process (AHP) and Ward's hierarchical clustering, an intensity allocation method is proposed. First, the preliminary regional decomposition scheme is presented via the preliminary decomposition model. Then, a multi-criteria evaluation system consisting of four layers and covering 13 evaluation indicators is developed via the AHP method, and the evaluation results are analyzed via the cluster method to further improve the preliminary scheme. As decision makers may have different preferences when allocating the reduction burden, we allocate different weights to the indicators and analyze the results using a sensitivity analysis. The clustering results indicate that the 18 regions of Henan are divided into five categories, and each category has its own significant characteristics. Regions with high obligation and potential should share the largest reduction burden. The allocation results show that seven regions, including Zhengzhou and Luoyang, are expected from 2016 to 2020 to exceed the provincial average decrease rate of 16%.

Description: Uncertainty management of the large scale wind power resources is mainly known as one of the most challenging aspects in future electricity market operations, where network operation may put at risk due to the wind power forecasting errors. Therefore, it is necessary to evaluate the impact of the wind power uncertainty on the operator risk-taking by using validated tools. This paper proposes a new mixed integer linear programming model for joint energy and reserve market clearing taking into account the co-optimization of the market clearing and operation cost of the thermal units. Also, wind power uncertainty is handled by means of two-stage stochastic programming and risk concept is introduced and formulated via a well-known measure to account for operator risk taking level. The proposed model is formulated as a two-stage stochastic programming where it clears the joint energy and reserve markets considering different penetration and forecasting accuracy levels of the wind power. Furthermore, supplementary terms are added to the objective function and constraints of the problem in order to measure the risk related to the wind power uncertainty.

Description: Meeting the goals set by the Energy Independence and Security Act requires evaluation of all potential feedstock sources including arid and semi-arid portions of the western United States (U.S.). The objective of this study was to assess the lignocellulosic feedstock potential in stream buffers of the inland Pacific Northwest. A 3-yr (2010–2012) experiment was conducted at two sites within each of the three precipitation zones (low, mid, and high). At each site, barley ( Hordeum vulgare L.), wheat ( Triticum aestivum L.), alfalfa ( Medicago sativa L., cultivar Ladak), tall wheatgrass ( Agropyron elongatum Podp. cultivar Alkar) (TWG), and a mix of alfalfa and tall wheatgrass (MIX) were planted in a randomized complete block experimental design. Productivity followed precipitation; in the high and mid precipitation zones, the MIX and TWG treatments showed potential production of 3,079 ± 262 l ha −1 and 3,062 ± 235 l ha −1 . Productivity in the low zone was inadequate or unreliable as a source of feedstocks. A geographic information system was then used to identify the area available for stream buffers with soil resources that matched the experimental results within each precipitation zone. In 3.7 × 10 6 ha of dryland cropland, 44 656 ha (1.5%) available within the mid and high precipitation zones is capable of producing 147 million liters of ethanol. This potential contribution is 0.3% of the lignocellulosic ethanol production expected by the year 2022. Though not a substantial contribution, the added benefit of producing energy for on-farm consumption might provide an additional incentive for landowners and managers to install conservation buffers.

Description: Advancement in technology has reduced the size and power consumption of wireless sensor nodes (WSNs), which leads to the possibility of a battery's replacement with alternative power sources, such as energy harvesters. For WSNs, harvesting energy from ambient vibration has great promise. This paper reports on the recent advancements in the development of vibration-based, non-resonant energy harvesters (NR-EHs). Based on the transduction mechanism, non-resonant electromagnetic energy harvesters (NR-EMEHs), non-resonant electrostatic energy harvesters (NR-ESEHs), and non-resonant piezoelectric energy harvesters (NR-PEEHs) have been successfully developed and reported. The frequency band of NR-EMEHs, NR-ESEHs, and NR-PEEHs is 0.5 to 140 Hz, 85 to 100 Hz, and 5 to 120 Hz, respectively. Moreover, these NR-EHs are subjected from low to high acceleration levels (0.102 to 16.1 g) during characterization. The overall size of the produced NR-EHs is in meso scale. The power generation of the reported NR-EMEHs is in the range from 0.75 to 2200  μ W. NR-ESEHs are reported to produce power from 0.7 to 35.3  μ W; however, the power production by the developed NR-PEEHs ranges from 3 to 18.5  μ W. These NR-EHs are shown to produce power densities from 0.01103 to 8461.54  μ W/cm 3 which are reasonably sufficient to operate most of the commercially available wireless acceleration sensor nodes.

Description: The automotive exhaust-based thermoelectric generator integrated with a three-way catalytic converter (TWC) can convert the thermal energy of exhaust gas into an electric energy, and solve the compatibility issues with an exhaust system. More power can be generated when the temperature of heat exchanger is higher. However, the performances of TWC are also affected by the temperature of the heat exchanger. To get more power generation and reduce the impact on the TWC, three heat exchangers with different section shapes were simulated and corresponding surface temperature and back-pressure were compared. Then three kinds of fins were employed in heat exchangers to figure out the effects. Finally, the results showed that the section shape had no obvious effect on the distribution of temperature and pressure in heat exchangers, but the arrangement of the fins inside the heat exchanger had a heavy impact on the performance of the heat exchanger. According to the simulation results, the heat exchanger in which the direction of fins was skewed to the streamwise could get higher temperature and output power at 192.96 W.

Description: In this paper, an optimal appliance management strategy proposed is participated in by both energy suppliers and customers. Through mathematical description of the appliance operation, a suitable plan is derived to satisfy both the power limits requested from the power suppliers and the least electricity bills from the end-users. Furthermore, the power suppliers will monitor the behaviours of the energy requirement from the customers. When the demanded electricity is close to the limits, the supplier will send a feedback signal to ask the end-users to stop using some kinds of appliances or postpone their operation for a while. When the demand is too low, a signal will also be sent to the end-users from the supplier to remind that some flexible appliances can be activated or used in order to achieve the “peak load shifting.” Renewable energy is also taken into account in the distribution network as auxiliary energy suppliers. Simulation experiments have been performed to prove the effectiveness of the proposed strategy.

Description: The Savonius rotor seems to be a promising wind turbine as it not only has the simplest and cheapest design but also is capable of yielding a higher annual energy output at low wind speed than the Darrieus rotor. Moreover, the Savonius rotor can also be used in ventilation systems, for local electricity production, as the start-up device for the Darrieus rotor, and small hydrokinetic turbines operating at low velocity. As a two-blade Savonius rotor suffers from negative average static torque coefficient (AC TS ) at some azimuth angles and large-amplitude variation of AC TS , several studies have been conducted in recent years to improve AC TS . The three-blade rotor seems to be a potential candidate for AC TS improvement. However, less research has been done on three-blade rotors with a 180° arc and central shaft at different gap ratios (GRs) for different wind speeds. Therefore, the focus of the present work is to compare the two- and three-blade rotor in terms of AC TS and power coefficient (C P ) through a wind tunnel experiment. Results show that the wind speed had a small effect on AC TS . However, negative azimuth angle range is narrowed and the negative azimuth angle range is moved upward as GR increased. Hence, the Savonius rotor with three blades could not only eliminate the negative range of AC TS but also smooth AC TS curves. In terms of the C P , the maximum power coefficient of the two-blade configuration was approximately 1.5 times that of the three-blade configuration. The 1/6 GR test data exhibited the attainment of super performance for all wind speed and blade number.

Description: To enhance the value of corn stalk and promote the utilization of corn stalk in pellet fuel, the pelletizing process of corn stalk rind using a flat die pelletizer was studied. A central composite design (CCD) methodology of four factors and five levels was applied to determine the effects of four process variables, i.e., material temperature, moisture content, die hole length-diameter ratio, and spindle speed, on responses such as pellet density and power consumption per ton. The statistical analysis of data was performed using Design-expert software and second-order polynomial models generated after analysis of variance applied for the responses. Using response surface methodology, the optimal range of process variable was obtained as follows: material temperature of 78.7 to 91.1 °C moisture content of 17.6% to 26.9%, die hole length-diameter ratio of 2.62–3.04, and spindle speed of 168.2–210.5 rpm. Under these conditions, the pellet density is over 1.0 g/cm 3 and power consumption per ton is below 90 kW · h/t.

Description: As a wind turbine generates power, induced velocities, lower than the freestream velocity, will be present upstream of the turbine due to perturbation of the flow by the rotor. In this study, the upstream induction zone of a 225 kW horizontal axis Vestas V27 wind turbine located at the Danish Technical University's Risø campus is investigated using a scanning Light Detection and Ranging (lidar) system. Three short-range continuous-wave “WindScanner” lidars are positioned in the field around the V27 turbine allowing detection of all three components of the wind velocity vectors within the induction zone. The time-averaged mean wind speeds at different locations in the upstream induction zone are measured by scanning a horizontal plane at hub height and a vertical plane centered at the middle of the rotor extending roughly 1.5 rotor diameters ( D ) upstream of the rotor. Turbulence statistics in the induction zone are studied by more rapidly scanning along individual lines perpendicular to the rotor at different radial distances from the hub. The mean velocity measurements reveal that the longitudinal velocity reductions become greater closer to the rotor plane and closer to the center of the rotor. Velocity deficits of 1%–3% of the freestream value were observed 1 D upstream of the rotor, increasing at the rotor plane to 7.4% near the edge of the rotor and 18% near the center of the rotor while the turbine was operating with a high estimated mechanical coefficient of power ( C P ) of 0.56 yielding an estimated axial induction factor of 0.25. The velocity reductions relative to the freestream velocity become smaller when the turbine's coefficient of power decreases; for a low C P of 0.16 resulting in an estimated induction factor of 0.04, the velocity deficits are ∼1% of the freestream value 1 D upstream of the rotor and only 6% at the rotor plane near the center of the rotor. Additionally, the mean radial wind speeds were found to increase close to the edge of the rotor disk indicating an expansion of the incoming flow around the rotor. Radial velocity magnitudes at the edge of the rotor disk of approximately 9% and 3% of the freestream longitudinal wind speed were measured for the abovementioned high and low C P values, respectively. Turbulence statistics, calculated using 2.5-min time series, suggest that the standard deviation of the longitudinal wind component decreases close to the rotor, while the standard deviation of the radial wind component appears to increase. When the turbine was operating with a high C P of 0.54 resulting in an estimated induction factor of 0.22, standard deviation decreases of up to 22% of the estimated freestream value and increases of up to 46% were observed for the longitudinal and radial components, respectively, near the center of the rotor.

Description: The rapid development of wind energy in Japan and the associated high uncertainties and fluctuations in power generation present a big challenge for both wind power generators and electric grids. Accurate and reliable wind power predictions are necessary to optimize the integration of wind power into existing electrical systems. In this study, a hybrid forecasting system of wind power generation was developed by integrating the Kalman filter (KF) with the high resolution Weather Research and Forecasting (WRF) model as well as an empirical formula of wind power output (power curve). The system has been validated with observations including wind speed and power output over a six-month period for 15 turbine sites at a wind farm in Awaji-island, Japan. The results show that the tuned WRF model is able to provide hub-height wind speed prediction for the target area with reliability to some extent. The predicted wind field can be substantially improved by the Kalman filter as a post-processing procedure. The 15-turbine averaged improvements of mean error, root mean square error, and correlation coefficient are 97%, 22%, and 10%, respectively. Meanwhile, the Kalman filter also demonstrates a promising capability of reducing the uncertainties in the power curve model. Systematic validations regarding both wind speed and power output were carried out against the observations for the target wind farm, which show that the hybrid power forecasting system presented in this paper can be an effective and practical tool for short-term predictions of wind speed and power output in Japan area.

Description: As a promising renewable energy source, wind energy has increasingly gained worldwide attention. Providing high accuracy wind energy forecasting allows us to improve the economic and social benefits of wind power management, which reduces the generation costs and improves the security of the wind power system. In this paper, a novel hybrid forecasting model called E-SA-BP, which combines ensemble empirical mode decomposition, a simulated annealing (SA) algorithm, and a back-propagation neural network (BPNN), is developed to perform wind speed forecasting. First, ensemble empirical mode decomposition is used to decompose the original wind speed data series aiming to de-noise and then reconstruct the data series. Next, BPNN is applied to perform short-term wind speed forecasting, because BPNN can implement any complex nonlinear mapping function (as proven by mathematical theory) and approximate an arbitrary nonlinear function with satisfactory accuracy. However, due to the instability of the structure of the BPNN, SA is utilized to optimize the weight and threshold values of the BPNN through simulating the annealing process of metal objects after heating. Last, the data of six wind speed observation sites in Jiaodong Peninsula of China are chosen to test the performance of the forecasting models. The results show an effective decrease in the forecasting errors of E-SA-BP when it is compared with the Moving Average(1), Exponential Smoothing (ES)(1), ES(2), Autoregressive Moving Average Model, Autoregressive Integrated Moving Average, BP, SA-BP, and E-BP models.

Description: In this paper, a double-glazed solar air heater (SAH) using paraffin wax as phase change material (PCM) was designed, fabricated, and tested under the climatic condition of Mashhad, Iran (latitude, 37° 28′ N and longitude, 57° 20′ E) during three typical days in the summer. The PCM stores solar radiation of the sun as latent and sensible heat during daytime and then restores such stored energy during the night. Exploitation of both first and second laws of Thermodynamics, the energy and exergy efficiencies of this system are assessed. According to the experiments undertaken, it is found that the daily energy efficiency of the system varies between 58.33% and 68.77%, whereas the daily exergy efficiency varies from 14.45% to 26.34%. Eventually, the economic analysis shows that the cost of 1 kg of heated air utilizing double-glazed SAH would be 0.0036$.

Description: An electric vehicles aggregator is in fact an intermediate between electric vehicles and the operator of the power grid. The Electric Vehicles (EVs) aggregator is responsible for the management of EVs in order to supply the owners with their orders and also for maximizing the profit of the power grid in the electricity market. In this study, an optimization model was developed for the operation of the EVs aggregator with an energy storage system in the reserve services market of the distribution network. In the proposed model, the reserve services market was formed after termination of the energy market. In this paper, the markets were created 24 h earlier.

Description: Renewable energies—such as solar photovoltaic power, hydropower, wind power, and forest biomass—have a key role in the European Union (EU) policy aimed at enhancing energy security and mitigating climate change. The new target established by European Commission for 2030 is a 30% improvement in energy efficiency, 40% less greenhouses gas emissions, and 27% increase in energy generation from renewable sources. In order to achieve this target, it will be necessary to define a political strategy to increase renewable energies' production. The renewable energies' production generates different kinds of environmental impacts, depending mainly on the energy source. For this reason, transdisciplinary and local expertise are crucial in order to assess impacts on various ecosystem services and to choose the best renewable energy sources to develop. This study evaluates the potential effects of renewable energies development on Alpine ecosystem services using a questionnaire-based survey. The questionnaire was administrated to a sample of 45 experts in several Alpine areas. Experts' opinions are fundamental for anticipating potential social costs and benefits caused by renewable energies and ensuring a successful formulation and implementation of energy policies, reducing conflicts and improving cooperation among the different groups of interest.

Description: To make large-algae cultivation systems sustainable, commercial fertilizer inputs should be minimized. One means of achieving this is to maximize the recycle of nutrients used in algae cultivation. In addition to recycling nutrient-containing water from algae harvesting and dewatering, after harvesting algal biomass can be used as a substrate for anaerobic digestion, which can then generate mineralized nutrients to be used for further cultivation. In this study, the effect of recycling media and using mineralized nutrients during Scenedesmus cultivation was investigated. The recycled media proved to be able to support cell growth with nutrient replenishment, and it could be recycled for cultivation up to four times. Algae biomass was subjected to anaerobic digestion, and the liquid digestate and the total digestate were tested as nutrient sources. The digestate was rich in ammonium ions and proved to be a sufficient replacement for urea. When both urea and ammonium ions were available in the media, the assimilation of urea by algal cells slowed down compared to the case where urea was the only nitrogen source.

Description: A technique that makes use of supervised machine learning (support vector regression) to correct systematic errors in long-term model wind time series is presented. The technique—Empirical Wind Output Correction (EWOC)—is computationally efficient and is particularly effective over complex terrain. In addition to error correction, EWOC acts as a non-linear feature identification tool by ranking the input site characteristics according to their ability to reduce the overall error. Independent regression functions are constructed for the mean and variance of the wind speed using an observational training data set comprising 109 onshore sites throughout Europe. Corrections are applied to Virtual Met Mast ™ (VMM) corrected time series, hindcast Numerical Weather Prediction output (Euro4), and raw Modern-Era Retrospective analysis for Research and Applications and ECMWF Re-Analysis (ERA)-interim reanalysis data. Reductions of approximately 40% in the Mean Absolute Error of the mean and variance of the wind speed compared to the source data are obtained. The quality of fit of the EWOC corrected wind speed distributions is examined through their Kullback-Leibler Divergences (KLD). Reductions of approximately 40% and 60% in the KLD are achieved compared to VMM corrected and raw ERA data, respectively. Possible methods for improving and extending the technique are suggested, including ways of maximising the size and quality of the training data set using a limited set of wind speed observations.

Description: Solar cell modelling primarily involves the formulation of the non-linear current versus voltage (I-V) curve. Determination of parameters plays an important role in solar cell accurate modelling. This paper presents an application of the hybrid Nelder-Mead simplex search method and modified Particle Swarm Optimization technique for identifying the parameters of solar cell and photovoltaic module models. The proposed technique is used to identify the unknown model parameters, namely, the generated photocurrent, saturation current, series resistance, shunt resistance, and ideality factor that govern the current-voltage relationship of a solar cell. A measurement data of 57 mm diameter commercial (R.T.C. France) silicon solar cell and a module consisting of 36 polycrystalline silicon cells (Photowatt-PWP 201) are used to test and verify the consistency of accurately estimating various parameters. Comparative study among different parameter estimation techniques is presented to demonstrate the effectiveness of the proposed approach. Furthermore, to verify the accurateness of the proposed technique, an experimental test bench unit is built using 72 mono-crystalline silicon cells (HIP-210NKHB5-2 module) on different environment conditions.

Description: An alternative method of testing maximum power point tracking and solar Photo Voltaic (PV) system performance with a solar PV emulator is presented in this paper. Solar PV emulators are Hardware-in-Loop setup, which mimics the characteristics of a PV panel. Further, these emulators are supplementary to strenuous field testing and commercial solar PV training systems available for research prototyping. In this paper, a solar PV emulator built using a DC-DC Buck Converter and dSPACE ds1104 controller is proposed. In addition, MATLAB/SIMULINK Environment is used to construct the Mathematical Model of Solar PV Module. The proposed Solar PV Emulator has the following features: (1) ease in interfacing with faster dynamic response, (2) ability to monitor and control in real-time using a control desk, (3) higher bandwidth DC-DC buck converter, (4) stable output with lower response time, (5) lower output voltage and current ripple, and (6) capability to reproduce near accurate static and dynamic characteristics of any solar PV module. To illustrate the performance of the proposed emulator, the I-V characteristics of a shell SP70 PV panel are obtained. To further understand the dynamic and steady state behaviour of the system, experimentations are done at different operating conditions. Finally, to know the suitability of the proposed emulator for maximum power point tracking, the Perturb & Observe algorithm is tested for uniform and partial shading conditions.

Description: In this paper, an efficient control is proposed and implemented to minimize the power fluctuation of grid connected photovoltaic (PV) with supercapacitor energy storage system (SCESS). The SCESS is used to minimize the power fluctuation caused by changes in temperature and irradiation. The optimal size of the SCESS and its control strategy are developed for continuously charging and discharging SCESS to achieve its objectives. Adaptive Neuro-fuzzy Inference System is developed in real time using dSPACE to generate the maximum power from the PV system. The SCESS is integrated with the system through a bi-directional buck boost converter. The system model and the control strategy have been developed in Real Time Digital Simulator (RTDS) that consists of PV array, buck converter, buck-boost converter, and voltage source converter (VSC). To transfer the available DC power to the grid, an independent P-Q control is proposed and implemented for the VSC. The proposed controller is examined through hardware in the loop setup using RTDS and dSPACE 1104 controller. Furthermore, the superiority of the proposed approach has been confirmed by comparing the results with those reported in the literature.

Description: The Turkish manufacturing sector has become the dynamo of the economy, driven by imported natural gas. However, the country's dependency on imported energy has also increased vulnerability of the country to the specter of unexpected supply shocks, and hence the long-term sustainability of industrialization. Thanks to long-term contracts which provide relatively cheap imports of natural gas, Turkey has sufficient “breathing space” to develop alternative energy sources. In the meantime, the country must adopt a rational pricing policy for imported natural gas to ensure allocative efficiency. Accordingly, this paper offers an econometric “gas-price-growth” model which reveals that long-run equilibrium relationship exists between each pair of variables such as natural gas prices, crude oil prices, taxes on gas and real exchange rates. Rapid changes in capital markets and possible risks associated with high inflation may increase future prices of natural gas in Turkey. Furthermore, this study revealed the existence of a unidirectional causalities running from real exchange rates and taxes towards real gas prices for household and industry. The study estimated the magnitude of how the exchange rate and the crude oil price could affect the natural gas prices in Turkey. The results reveal that when there is a 1% increase in real exchange rate of Turkey, it causes 0.144% increase in industry gas prices. The estimated results for household demand also indicate that when there is a 1% increase in taxes, the household prices increase by more than 0.65%. When industry demand is concerned, a 1% increase in taxes causes more than 0.77% increase on industry gas prices in Turkey. The fiscal decisions of government in Turkey may have a great impact on natural gas prices.

Description: In this work, two-dimensional and three-dimensional simulations on the flow in a room coupled with a facade of passive heating system type In-In (Trombe wall) were conducted numerically to determine the temperature and velocity fields in the influence of the variation of the modified Rayleigh number, which itself depends on the characteristics of the fluid and heat flow due to sunshine. The behavior of boundary layers in natural convection is analyzed along the Trombe wall in our periodically heated imposed flow. Thermal and dynamics modeling of the problem were made by a computational fluid dynamics (CFD) calculation, based on the finite volume method to model both the fluid flow and heat transfer. To take account of the strong temperature gradient and velocity near the walls, we chose a structured tight mesh near the walls and a little wider mesh elsewhere. The results have shown that for Gr h  〉 4 × 10 8 , the flow regime is laminar, while for Gr h  〉 10 9 , the flow regime becomes turbulent.

Description: To handle the challenges created by the integration of large-scale wind power for the normal operations of power systems, the development of bundled wind-thermal generation systems (BWTGSs) is now being considered in China. This paper proposes a two-stage optimal planning method to determine the optimal scheme of matched thermal generating units (TGUs) in a BWTGS and the optimal load that the BWTGS should take. In the first stage, a basic optimization model taking into account the operation characteristics of BWTGS and the load pattern of the receiving power system is constituted to obtain the optimal TGU scheme. In the second stage, a heuristic method called the window search method is designed to optimize the base load of the BWTGS and further reduce the system unit generation cost. Numerical analyses demonstrate the effectiveness of the proposed method.

Description: Lifting line vortex models have been widely used to predict flow fields around wind turbine rotors. Such models are known to be deficient in modelling flow fields close to the blades due to the assumption that blade vorticity is concentrated on a line and consequently the influences of blade geometry are not well captured. The present study thoroughly assessed the errors arising from this approximation by prescribing the bound circulation as a boundary condition on the flow using a lifting line free-wake vortex approach. The bound circulation prescribed to free-wake vortex model was calculated from two independent sources using (1) experimental results from SPIV and (2) data generated from a 3D panel free-wake vortex approach, where the blade geometry is fully modelled. The axial and tangential flow fields around the blades from the lifting line vortex model were then compared with those directly produced by SPIV and the 3D panel model. The comparison was carried out for different radial locations across the blade span. The study revealed the cumulative probability error distributions in lifting line model estimations for the local aerofoil flow field under both 3D rotating and 2D non-rotating conditions. It was found that the errors in a 3D rotating environment are considerably larger than those for a wing of infinite span in 2D flow. Finally, a method based on the Cassini ovals theory is presented for defining regions around rotating blades for which the lifting line model is unreliable for estimating the flow fields.

Description: This paper proposes an uninterruptible all-electric smart house equipped with photovoltaic system and storage battery. There is a control delay in the conventional control system, because the system uses root mean square or average values for the control method. Therefore, it causes transient currents when load variation and system faults occur. The transient current adversely affects the in-house loads (e.g., precision equipment). In this paper, the control delay is reduced by using a control system with single-phase dq -transformation information. Therefore, the smart house achieves a reduction of the transient current caused by load variation and system faults through the use of instantaneous inverter control. The effectiveness of the proposed method is verified by simulation results given by the Matlab/SimPowerSystems ® environment.

Description: A thermal growth model for microalgae that are not heavier than water with the consideration of heat transfer and growth-temperature dependence in photobioreactor (PBR) is developed. The microalgae growth performance is studied, and influences of various parameters on the performance are examined. Improved methods are proposed to increase the biomass concentration in the PBR. Results show large increase in biomass productivity due to the addition of a mixer in the PBR, and slightly larger increase in productivity when cultivating microalgae at several middle layers with a mixer and filter membranes. Some layers in the PBR may effectively act as insulation layers in this case. This work lays a solid foundation for further study on the effect of the mixing on the growth and productivity of microalgae in the PBR.

Description: This paper describes a technology for condensable vapor from pyrolysis (often referred to as “tar”) of oil palm empty fruit bunch, EFB, to be collected—by EFB char substrate—in the form of pyrolytic carbon to produce a value-added EFB char and to make EFB able to be utilized as a supplementary solid fuel. Chemical vapor infiltration method was employed at atmospheric pressure for tar vapor to undergo secondary decomposition to produce pyrolytic carbon to be deposited within porous char. Porous char in a packed bed was used as the substrate, and impregnated with pyrolytic carbon using tar vapor as a reactant. Char substrate was prepared by slowly heating coarse EFB particles in the packed bed to 400 °C in nitrogen atmosphere. Tar vapor was obtained from fast pyrolysis of fine EFB particles at 400–700 °C, and the weight ratio of fine EFB particles—the tar source—to char substrate was increased from 0.5 to 4.0. The amount of carbon contents of the resultant products by this process was compared to those without carbon deposition. After carbon deposition, EFB char has substantially increased in carbon contents which promise higher heating values than those of EFB char with no carbon deposition. The resultant products can be used as a partial substitute to the now depleting fossil fuels.

Description: Radiation heat transfer has very many applications in building physics. In such studies, one has to deal with radiant energy exchanges between surfaces of different orientation and aspects. Two principal cases that may be cited here are exchanges between (i) surfaces that share a common edge and are at an angle to each other, and (ii) surfaces that are parallel to each other. Examples that may be cited here are walls of buildings and also ceiling and floor areas. In a previous work, the authors presented a generalised, numerical-oriented solution for analysing radiant exchange that belongs to case (i) cited above. In the present article, a generalised treatment for case (ii) is presented. A software tool is also provided for analysing the radiant exchange for surfaces that are parallel to each other and have uniform or non-uniform reflectivity, incident irradiation and/or emission. As a demonstration of the applicability of the present work, calculation of incident reflected irradiation on the walls of urban street canyons with varied orientation and non-uniform reflectivity is presented. Finally, the application of the presently developed tools for enhancing building design has been highlighted.

Description: Evaluation and validation of photovoltaics performance models for different technologies and climate regions is of high interest for photovoltaic (PV) systems deployment. There are many tools for modelling the performance of PV arrays; some of them are free or open source. This work presents the results of modelling five different rooftop PV arrays in the range of 1 kW using the Sandia Array Performance Model during one complete year in Madrid. The evaluation of the Sandia model has shown a rather good performance in general, even though several empirical parameters in the input were unknown and were taken from other similar modules in the Sandia database. Particularly, high accuracy has been found in modelling the p-Si array with −0.07% of relative error in the annual energy output. Larger errors were found in the case of a-Si and m-Si (back contact) arrays.

Description: This work aims to optimize the design and operation of a heat pipe photovoltaic-thermal (HP-PV/T) panel integrated with a phase change material (PCM) thermal storage water tank to produce electricity and hot water for an office building. A transient mathematical model for the integrated HP-PV/T-PCM system was used to predict its performance for known environmental and solar conditions and PCM melting point. The validated model was applied on a typical office space in the city of Beirut to obtain an optimal design using a derivative free genetic algorithm. The incremental system cost associated with a heat pipe and PCM tank was used in the optimization to obtain a design resulting in minimum annual auxiliary heating cost to meet the hot water demand while providing the electricity needs at a lower number of PV panels due to improved efficiency. An optimal system of 4 kW (20 PV panels each at 1.6 m 2 ) was found to meet the electric power needs all year round. The optimal PCM storage tank size per panel was 37 l at PCM total mass of 22.42 kg with melting temperature of 33 °C.

Description: The actuator disc (AD) model is commonly used to simplify the simulation of horizontal-axis wind-turbine aerodynamics. The limitations of this approach in reproducing the wake losses in wind farm simulations have been proven by a previous research. The present study is aimed at providing an experimental analysis of the near-wake turbulent flow of a wind turbine (WT) and a porous disc, emulating the actuator disc numerical model. The general purpose is to highlight the similarities and to quantify the differences of the two models in the near-wake region, characterised by the largest discrepancies. The velocity fields in the wake of a wind turbine model and a porous disc (emulation of the actuator disc numerical model) have been measured in a wind tunnel using stereo particle image velocimetry. The study has been conducted at low turbulence intensity in order to separate the problems of the flow mixing caused by the external turbulence and the one caused by the turbulence induced directly by the AD or the WT presence. The analysis, as such, showed the intrinsic differences and similarities between the flows in the two wakes, solely due to the wake-induced flow, with no influence of external flow fluctuations. The data analysis provided the time-average three-component velocity and turbulence intensity fields, pressure fields, rotor and disc loading, vorticity fields, stagnation enthalpy distribution, and mean-flow kinetic-energy fluxes in the shear layer at the border of the wake. The properties have been compared in the wakes of the two models. Even in the absence of turbulence, the results show a good match in the thrust and energy coefficient, velocity, pressure, and enthalpy fields between wind turbine and actuator disc. However, the results show a different turbulence intensity and turbulent mixing. The results suggest the possibility to extend the use of the actuator disc model in numerical simulation until the very near wake, provided that the turbulent mixing is correctly represented.

Description: The aerodynamic performance of two very thick wind turbine airfoils, DU00-W-401 and CAS-W1-450, is examined by experimental and computational methods at a Reynolds number of 1 × 10 6 . The measurements were carried out in a wind tunnel with a cross-sectional dimension of 1.5 m × 1.5 m and a length of 2.5 m. The results are compared with predictions from Reynolds-averaged Navier-Stokes (RANS) simulation with a k- ω turbulence model and a transition model. To eliminate the unstable effect, three runs of measurements were conducted and then the results were averaged. The lift performance of DU00-W-401 is in good agreement with a previous research result, showing the experimental method is reliable. RANS well predicts the lift performance at the linear region on the lift curve, but tends to underestimate the drag and overestimate the lift in post-stall condition. The pressure drag taking a large proportion to the total drag results in a high drag coefficient for the very thick wind turbine airfoil. A three-dimensional characteristic is observed in the experiments by comparing surface pressure at different spanwise positions.

Description: The physicochemical properties and hygroscopicity of biochar derived from tobacco stem pyrolysis were investigated to get the effect of pyrolysis temperature (250–950 °C). The chemical composition and structure of biochar were characterized with proximate and ultimate analysis, X-ray fluorescence, and two-dimensional perturbation-based correlation infrared spectroscopy (2D-PCIS) based on Fourier-transform infrared spectroscopy. The physical pore structure was analyzed by Brunauer-Emmett-Teller surface area. Results showed that surface area and pore volumes of biochar increased, while biochar yield, volatile matter, H/C and O/C ratios decreased with the increasing pyrolysis temperature. The 2D-PCIS analysis suggested that the intensity of hydroxyl groups and aromatic skeletal changed greatly with pyrolysis temperature. Tobacco stem biochar was abundant in Ca and K and contained P, Mg, S, and Cl, while N was low and decreased with temperature. Tobacco stem biochar produced at 550 °C has the lowest hygroscopicity under 50%–70% humidity. Biochar produced from tobacco stem may not be suitable to be used as fuel while it can be developed for soil amendment and adsorbent by optimizing pyrolysis conditions and modifications.