Thermodynamic evaluation and optimization of a solar geothermal hybrid system in Northern Chile

Chile is developing a national strategy to reduce the external dependence on energy supply sources, for which renewable resources must provide 20% of the electricity generation by 2025. As the northern part of the country exhibits a large arid desert area that has the highest radiation levels in the world and a considerable amount of active geothermal areas, proposing the hybridization of both renewable resources together is deemed advantageous considering the benefits that each resource presents and allows exploring potential synergies between both. A thermodynamic model is developed using the Engineering Equation Solver (EES) software in order to evaluate the performance of a single-flash power plant assisted by a parabolic trough collector system for four different geothermal reservoir conditions. The benefits of delivering the solar thermal energy to the superheating or evaporating processes are analyzed, in order to achieve the maximum 2nd law efficiency for the generation of additional power, or to reduce the geothermal fluid flow consumption. The results in the single-flash hybrid system show that the superheating process generates 0.23 kW of additional power per kW of thermal energy, while enhancing the brine evaporation produces only an additional 0.16 kW of power per kW of solar thermal energy. Hence, the single-flash hybrid power plant is able to produce at least 20% of additional power output and increase at least 3% the exergetic efficiency. This hybrid flash system presents a promising alternative towards the generation of additional power output and extending the lifetime of a geothermal well.