Journal of Renewable Energy
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Modeling of an Electrical Energy Switching System in Multisource Power Plants: The Case of Grid Connected Photovoltaic and Wind Power Systems

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Journal of Renewable Energy publishes papers relating to the science and technology of renewable energy generation, distribution, storage, and management. It also covers the environmental, societal, and economic impacts of renewable energy.

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Journal of Renewable Energy maintains an Editorial Board of practicing researchers from around the world, to ensure manuscripts are handled by editors who are experts in the field of study.

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Research Article

DFT Studies of p-N,N-(Dimethylamino) Benzoic Acid with Para or Meta–Electron Withdrawing or Donating Moieties for Dye-Sensitized Solar Cells (DSSCs)

Solar energy is receiving considerable attention worldwide. Our contribution here focuses on fabricating p-N,N-(dimethylamino) benzoic acid (4-DMABA) donor-π-acceptor derivatives for use in dye-sensitized solar cells (DSSCs). The gas-phase and solvated 4-DMABA and some of its electron donating or withdrawing ortho or meta derivatives were studied theoretically. Density functional theory (DFT) and time-dependent DFT (TD-DFT) were applied to visualize their structural, molecular, photoelectrical, electronic, and photophysical parameters. The parameters for monitoring DSSC efficacies include HOMOs, LUMOs, energy gaps, wavelengths, oscillator strengths, light harvesting efficiencies (LHE), electron injection driving forces (ΔGinject), regeneration driving forces (ΔGregen), open circuit voltages (VOC), and short-circuit current densities (Jsc).

Research Article

Design and Optimization of a Wind Turbine for Rural Household Electrification in Machakos, Kenya

Machakos is an area characterized by low wind speeds in the range of 0.5 m/s to 5 m/s with an annual average wind speed of 3.5 m/s. Maximum power generation from wind requires the appropriate design of the conversion system. In this study, two HAWT rotor blades were fabricated using Styrofoam and aluminium with a pitching mechanism to maximize power. The system was tested in a wind tunnel environment at a wind speed range of 0 m/s−20 m/s. RPMs and torque were measured and then used to calculate the TSR and power coefficients at different pitching angles. Energy optimization was performed by varying the pitch angles from 0 to 40 degree and rotational speeds, blade shape, and also a variation of blade materials. The analysis of tip speed ratios showed positive skewness implying high potential for significant energy generation at low wind speeds. At the rated wind speed of 5 m/s, Styrofoam blades performed optimally at a pitch angle of 20 degree with a tip speed ratio (TSR) of 2.1 corresponding to a Cp of 0.465. This translates to 238 W of power. Aluminium type performed optimally at a pitch angle of 15 degree with a TSR of 1.9 corresponding to a CP of 0.431, a power estimate of 220 W. These findings showed that Styrofoam blades were more effective and thus suitable for application in wind systems. The understanding gained from this study could be useful to the HAWT research community and can be extended to the turbine designs for small-scale microgrids and utility applications.

Research Article

Feasibility Study of a Hybrid PV/Hydro System for Remote Area Electrification in Rwanda

Rwanda is among the least developed countries on the globe with total access to electricity not exceeding 63%, where the rest of the population lives in areas with no access to electricity. One such a place, which is the focus of this research, is Musanze district (1.4919 S, 29.5572 E), where 60% of the population in this area are located in remote areas, which makes the task of their electrification via grid system very difficult. Micro hydropower has been developed so far to reduce the deficit of energy access in this area. However, the power generated is not enough to cover the area, and the major problem is the decrease in river water level in the dry season, which affects the power generation. In this work, the feasibility of a hybrid PV/hydroelectric supply system is studied and optimized to increase the number of homes accessing electricity in this area. A 200 kW Mutobo micro hydro system in Musanze district under operation is considered a case study where a 100 kW PV array tied to the micro hydropower system is designed. The optimized PV-hydro hybrid system was proposed using a modified and O MPPT algorithm to enhance the PV-generated power. The model was designed and simulated using MATLAB/Simulink, and data recorded from Mutobo micro hydropower station, Rwanda Energy Group, and National Meteorological Agency were used to estimate solar energy potentials. The results showed that the hybrid PV/hydro system is feasible and effectively contributes to the power shortage mitigation in remote areas during the dry season.

Review Article

Renewable Energies in Ghana in Relation to Market Condition, the Environment, and Food Security

Energy is essential to the development of a country, and several studies have been carried out on the production and use of energy by industrialised countries. However, little research and development has been carried out in developing countries on renewable energy. Also, the importance of traditional fuels such as biomass has not been emphasised in developing countries like Ghana, which rely on fossil fuels. Ghana relies heavily on imported petroleum fuel obtained from fossil fuels. However, fossil fuels are faced with many limitations including environmental pollution and an escalating price. Hydropower, biomass, biofuel, wind, and solar energy are the major renewable energy resources expected to be fully exploited in the future. This study, therefore, assesses the sources of the main renewable energy in relation to policy, the conditions of the market and food security. The government of Ghana has put in place a favourable business environment for the renewable energy sector by setting explicit feed-in tariffs (FITs). In addition, various acts and legislation have been passed and formulated by the relevant institutions (Renewable Energy Act (832) of 2011). The study revealed that there is an increase in the exploitation and use of energy from renewable resources when compared with the past decades. However, this exploitation is still limited due to barriers such as the cost of technologies, financing issues, and scientific and technical barriers.

Review Article

A Review on Computational Fluid Dynamics Applications in the Design and Optimization of Crossflow Hydro Turbines

In recent years, advances in using computational fluid dynamics (CFD) software have greatly increased due to its great potential to save time in the design process compared to experimental testing for data acquisition. Additionally, in real-life tests, a limited number of quantities are measured at a time, while in a CFD analysis all desired quantities can be measured at once, and with a high resolution in space and time. This article reviews the advances made regarding CFD modeling and simulation for the design and optimization of crossflow hydro turbines (CFTs). The performance of these turbines depends on various parameters like the number of blades, tip speed ratio, type of airfoil, blade pitch, chord length and twist, and its distribution along the blade span. Technical aspects of the model design, which include boundary conditions, solution of the governing equations of the water flow through CFTS, and the assumptions made during the simulations are thoroughly described. From the review, a clear idea on the suitability of the accuracy CFD applications in the design and optimization of crossflow hydro turbines has been provided. Therefore, this gives an insight that CFD is a useful and effective tool suitable for the design and optimization of CFTs.

Research Article

Performance Analysis of Clear Sky Global Horizontal Irradiance Models: Simple Models Adapted for Local Conditions

Evaluation of the maximum solar energy potential of a given area for possible deployment of solar energy technologies requires assessment of clear sky solar irradiance for the region under consideration. Such localized assessment is critical for optimal sizing of the technology to be deployed in order to realize the anticipated output. As the measurements are not always available where they are needed, models may be used to estimate them. In this study, three different models were adapted for the geographical location of the area under study and used to estimate clear sky global horizontal irradiance (GHI) at three locations in the subtropical desert climate of Namibia. The three models, selected on the basis of input requirements, were used to compute clear sky GHI at Kokerboom, Arandis, and Auas. The models were validated and evaluated for performance using irradiance data measured at each of the sites for a period of three years by computing statistical parameters such as mean bias error (MBE), root mean square error (RMSE), and the coefficient of determination (R2), normalized MBE, and normalized RMSE. Comparative results between modelled and measured data showed that the models fit well the measured data, with normalized root mean square error values in the range 4–8%, while the R2 value was above 98% for the three models. The adapted models can thus be used to compute clear sky GHI at these study areas as well as in other regions with similar climatic conditions.

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