| Energy is among the most significant enablers of socioeconomic development that has proven to be a strong challenge for Rwanda.since many decades,unbalanced national installed electricity capacity and demand,low electricity access,high electricity tariffs,unstable electricity,frequent blackouts,and significant untapped natural local energy resources(including solar energy)have persisted.As a result,off-grid photovoltaic systems are suggested as the solution to the issue of energy shortage and chaos in this master’s thesis.In this master’s thesis,the designing and optimization of off-grid solar photovoltaic(PV)systems for Rwanda is studied.It was based on community load located in Rwanda,with a daily load capacity of 1.60 kWh/day and 193.05 kWh/day for the stand-alone solar PV for one residential house and off-grid PV microgrid system for rural community respectively.The microgrid software HOMER(Hybrid Optimization of Multiple Energy Resources)through its optimizer and its proprietary derivative-free algorithm were used to perform the design,simulation,optimization,and analysis of microgrid electricity power generation systems options energy storages.The modelling and optimization were subjected to finding the affordable and high green energy technology suitable to supplying electricity to the community load while fulfilling the constraints conditions such as the annual capacity to satisfy the load,the percentage of the penetration of renewable energy,effectiveness,sustainability and impact level on climate change toward the clean environment(minimal or zero gas emissions).The results showed that the stand-alone PV for an individual household was optimal for both off-grid users.Then,the shading effect of different PV modules is studied.In order to help users choose the right solar photovoltaic module,based on the numerical model of photovoltaic module,piecewise function principle,series parallel circuit,and MATLAB simulation model using Simulink.The study was based on the mathematical model of PV modules,theory of series¶llel circuit,piecewise function,and Matlab/Simulink simulation.The eight PV modules namely hybrid amorphous/microcrystalline(a-Si+ μc-Si),monocrystalline(c-Si),hybrid amorphous/monocrystalline(mono+a-Si),Copper Indium Gallium Selenium(CIGS),Copper Indium Selenium(CIS),cadmium telluride(CdTe),amorphous(a-Si),and polycrystalline(pc-Si/mc-Si)were analysed in details through simulations in the cases of uniform and non-uniform partial shading(1000 W/m2,350W/m2 and 550 W/m2),two different PV modules were selected for each PV type to make the research results more universal.The results showed that due to the diversity of structures and materials,the shading effect deeply decreased the current while the voltage increased,resulting in various net output power decreases(reduction)and different shade impact factor levels.Generally,the thin-film types were found to be with better low light performance than crystalline modules.Therefore,the thin-film PV types are recommended for use when shading cannot be avoided.Also,hybrid of mono+a-Si PV module type showed higher efficiency and is recommended for non-cost sensitive projects,for cost sensitive,the c-Si is recommended.With proper PV choices,the microgrid be further be modelled smoothly.Finally,modeling optimal cost strategy for grid-connected solar PV microgrids under variable loads is studied.Taking Rwanda power grid as the research object(because of its expensive electricity price),two cost optimization approaches namely heuristic based approach and linear programming optimization algorithm were modeled and implemented in Matlab/Simulink through codes programming and scripting in order to search and achieve optimal daily operational cost and management strategy for the grid connected solar PV microgrid in this study.The results show that the linear programming was found to be more optimal algorithm than heuristic based approach.According to the research in this master’s thesis,(1)New energy sources including solar energy can truly solve the power energy supply for remote areas and national grid-connected customers in Rwanda,the established optimal solar PV microgrid power generation system modeling and optimization schemes are effective,(2)adaptability of different types of PV modules to shading is different,the thin-film PV modules showed a better adaptability to shading conditions than for crystalline PV modules,thin film PV modules can be recommended when shading cannot be completely avoided,the hybrid of mono+a-Si PV module type shows higher efficiency but it is recommended only for non-cost-sensitive projects,for cost-sensitive,c-Si PV modules can be recommended,(3)the proposed linear programming algorithm was effective for microgrid daily energy optimization and management. |
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