Optimization of a renewable energy hybrid system

Abstract

It has become increasingly important to eliminate fossil fuel as a power generation source. Fossil fuel is one of the main sources of greenhouse gases, and the Korean government has officially announced its aggressive plan for reducing greenhouse gases. As a result, the Korean government has been expanding its renewable energy generation facilities

therefore, the reduction of fossil fuel is a major policy issue. In this context, expanding renewable energy generation facilities can be a viable measure for reducing the use of fossil fuel in urban areas. This study evaluated the feasibility of a renewable energy hybrid system in Gwangyang-si, which has the lowest degree of carbon emissions among the Korean municipalities. To facilitate this analysis, HOMER(Hybrid Optimization for Electric Renewables) was used to determine the following factors: power grid features, actual power consumption, renewable and sustainable energy sources and distribution facilities. HOMER is the economic feasibility analysis simulation program for renewable energy hybrid systems that was developed by NREL(National Renewable Energy Laboratory). HOMER is an optimization program that aims to find a small-scale power configuration combination that minimizes cost by designing off-grid and grid-connected power systems. This software analyzes a variety of renewable energy sources. In this study, a sensitivity analysis was conducted on the renewable energy hybrid system that was built based on the monthly mean wind velocity and the fuel price of Gwangyang-si for 2014. This sensitivity analysis found that the PV 5%,grid 95% hybrid system was better for the environment than the grid-diesel system. If a carbon tax is introduced, the PV 5%, grid 95% hybrid system has a higher. The levelized COE(cost of electricity) of the grid-diesel system was compared with that of the PV-grid hybrid system. The results showed that the COE of the PV-grid system was higher than that of the grid-diesel system. However, the PV-grid system was much better for the environment because the quantity of greenhouse gases emitted was substantially decreased. The annual $CO_2$ emissions of the grid-diesel system were 752,921kg/yr, whereas the annual $CO_2$ emissions of the PV-grid hybrid system were 722,739kg/yr. Thus, the PV-grid hybrid system can substantially reduce the discharge fee over 30 years. Moreover, if there is a penalty for discharging carbon, then the difference between the NPC(net present cost) for 5% renewable energy and the NPC of the current system would decrease. That is, there would be a higher ROI(return on investment) for renewable energy if a carbon tax was levied. Recently, the environmental pollutant discharge fee has been increasing. For instance, the EU is planning to increase the environmental pollutant discharge fee. Thus, the investment value of renewable energy will likely increase. The technical feasibility of a renewable energy hybrid system that is modeled based on an energy storage facility such as a fuel battery is also analyzed. The limitations of this paper and possible future studies will be discussed in the last section of this paper.