Optimal Sizing of a Micro-Hydrokinetic Pumped-Hydro-Storage Hybrid System for Different Demand Sectors

Abstract

Due to high investment costs of renewable energy systems, optimal sizing of hybrid renewable energy system is critical to adequately meet the load demand at low cost. Studies based on optimal sizing of the hydrokinetic hybrid systems used the hybrid optimization model for electric renewable (HOMER) software as a simulation tool. The HOMER Legacy Version that was used in these studies does not have a built-in hydrokinetic module in its library. As a result, the authors used a wind turbine module to model a hydrokinetic turbine. In this study, the optimal size of a river-based micro-hydrokinetic pumped-hydro-storage (MHK-PHS) hybrid system is determined using HOMER Pro Version 3.6.1 since it has a built-in hydrokinetic module in its library. The results obtained using HOMER Pro Version 3.6.1 will be compared to the results obtained using the methodology adopted by previous researchers (using HOMER Legacy Version). The objective is to validate the best economical approach for sizing a hydrokinetic hybrid system. The second objective of the study is to investigate the effect brought by different demand sectors such as residential, commercial, and industrial load on sizing and operation of the proposed MHK-PHS hybrid system. The results have shown that the methodology applied in HOMER Legacy Version leads to oversizing of the storage system. This resulted into higher initial capital cost, net present cost (NPC), levelized cost of energy (COE), and operating cost. The results also proved that for the same daily energy consumption, a type of a demand sector does not affect the size of a hydrokinetic turbine and annual excess energy. Instead, it affects the size of the storage capacity as well as the size of the hydro-turbine. The commercial load profile proved to lead to the lowest state of charge (SOC) of the storage reservoir.