Energy, exergy, and exergoeconomic analysis of power generation cycle based on independent geothermal and solar energy

The increasing energy demand in industrial and operational units and corresponding concerns about the limited fossil resources as well as environmental pollutions urge the researchers to generate electricity from renewable energy sources such as wind, geothermal, solar, and biofuels. In the present work, the use of solar and geothermal energy in producing electricity is investigated. The proposed cycle is capable of producing power by using both solar and geothermal energy sources simultaneously or can be used separately to generate electricity. Organic Rankine Cycles (ORCs), which benefit working fluids like refrigerants, have been employed. These cycles are able to produce electricity from low-temperature energy sources. The cycle is designed to employ two evaporators as high temperature and low temperature ones and, consequently, is equipped with two turbines as high and medium pressure ones. The governing equations of mass balance and first and second laws of thermodynamics were applied to each cycle component. A numerical code is written and solved by EES software. The performance of the proposed cycle was analyzed by energy and exergy viewpoints and the first and second law efficiencies were calculated. Therefore, the amount of exergy destruction and exergy efficiency of each component was defined. To evaluate the cost of the final product, which is electricity, exergoeconomic analysis, as an efficient tool, was carried out and the final cost of products was defined. Parametric study of the effect of different designing parameters, such as pinch point temperature difference and evaporator temperature on the energy and exergy performance and cost of the product was done. The obtained results showed that the best second law efficiency was related to high-pressure turbine, whereas the low-pressure turbine acquires the highest value of exergoeconimc factor. The average electricity production cost based on power generation in low- and high-pressure turbines was calculated as (0.102$/kwh).