Conceptual design of solar/geothermal hybrid system focusing on technical, economic and environmental parameters

Abstract The costs of gas transportation and its environmental/security impacts in Iran have led to evaluating geothermal/solar renewable sources instead. Regarding the high potential of geothermal/solar in Sistan/Baluchestan province, Iran, which have still no access to the global gas network, these resources create a desirable plan. This paper attempted to present/compare four possible solar-assisted ground source heat pumps to supply four purposes of electricity demand, heating/cooling, and domestic hot water. First, the energy needed in the region was designed with DesignBuilder. Then, each proposed system was modeled in Polysun software using a photovoltaic-thermal and a vertical geothermal heat exchanger. Afterward, all probable plans were evaluated and compared technically, economically, and environmentally. The results indicated that the maximum/minimum values of the coefficient of heat pump performance for direct heat exchanger and series systems were 4.39/3.87. Also, the optimal plan was introduced with 4957/10667kWh electricity consumption/production. Besides, an economic analysis was estimated for the optimal strategy with an investment return of 7years. The designed system prevented 5089kgCO2 emissions annually. By means of this integrating hybrid system, Sistan/Baluchestan province would become a significant renewable power plant globally, and a considerable techno-economic and environmental challenge would be dissolved in Iran.