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The purpose of this paper is to evaluate the cost benefit of a self-optimized solar-wind-hydro hybrid energy supply and to compare the outcome with a similar optimization done with the HOMER software. In reality HOMER optimization software has long been used for hybrid system optimization and many do consider it as the reference software for any optimization related to hybrid energy systems. However, due to some few lack of flexibility in the setting-up of constraints and also the ignorance of the true optimization approaches used by the HOMER, it has become necessary to develop selfoptimized algorithms based on rigorous mathematical models. One of these self-optimized models, developed in a previous study, was presented in this paper and was tested with data collected at Accra, Ghana. Results show that the cost of electricity proposed by the HOMER, 0.307$/kWh, is slightly lower than the one obtained through the self-optimized method, 0.442$/kWh. Moreover looking at the dynamism of selecting different sources to achieve the optimization at a lower rate for the user, more credit is given to the developed method than the HOMER because the self-optimization method gives more priority to the wind turbine than the solar plant due to the higher electricity cost of solar (0.64$/kWh). It was however observed that the HOMER software does the opposite in terms of priority. Moreover the probability of unmet load is lower with the self-optimized method than the HOMER result which consists of a big contribution because it is a major quality measure for hybrid systems to always satisfy the load request.

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This paper consists of an extensive review on the modeling of hydropower plant. First a background was provided on all components needed to develop a full and comprehensive model on hydropower plant including penstock, governor, turbine and generator. The review of existing models was started with simple analytical models that were followed by system modelling. The complexity of modeling the dynamic aspect of water flowing through the penstock as well as the opening and closing of wicket gate have led to the development of complex control systems to model hydropower plant. Those complex models were rather represented as systems instead of been analytical. They are mostly equipped with numerous feedback as well as modern control systems such as fuzzy logic and PID control logic that improves their performances. However, these models are most often constructed and simulated with software of which Matlab is a fundamental one. In line with this, the paper investigated a simulation of hydropower plant including a model of hydraulic turbine, governor and synchronous machine, all simulated under Matlab software. A three phase to ground fault was introduced in the model at t=0.2s and remove after t=0.4s and this shows that the generated voltage quickly regained its stability due to the high excitation voltage that was maintained by the PID control system incorporated in the hydraulic turbine model. The speed of the motor also regained stability but this case was slower than the voltage one. In all, simulation results showed a perfect generation of energy from hydropower plant that was robust enough to resist faults.

This paper performs a technoeconomic comparison of two hybrid renewable energy supplies (HRES) for a specific location in Ghana and suggests the optimal solution in terms of cost, energy generation capacity, and emissions. The two HRES considered in this paper were wind/hydrogen/fuel-cell and wind/battery storage, respectively. The necessity of this study was derived from the rise and expansion of hybrid renewable energy supply in a decentralised network. The readiness to embrace these new technologies is apparently high, but the best combination for a selected location that brings optimum benefits is not obvious and demands serious technical knowledge of their technical and economic models. In the methodology, an analytical model of energy generation by the various RE sources was first established, and data were collected about a rural-urban community in Doderkope, Ghana, to test the models. HOMER software was used to design the two hybrid systems based on the same load profiles, and results were compared. It turns out that the HRES 1 (wind/hydrogen/fuel-cell) had the lowest net present cost (NPC) and levelized cost of electricity (COE) over the project life span of 25 years. The energy reserve with the HRES 2 (wind/battery storage) was huge compared to that with the HRES 1, about 270% bigger. Furthermore, with respect to the emissions, the HRES 2 was environmentally friendlier than the HRES 1. Even though the battery storage seems to be more cost-effective than the hydrogen fuel-cell technology, the latter presents some merits regarding system capacity and emission that deserve greater attention as the world looks into more sustainable energy storage systems.