Electric Generation with Low-Enthalpy Geothermal Sources for Self-Consumption in the El Guayacán Hotel in Guanacaste, Costa Rica

Abstract

Through the Distributed Generation pilot project, promoted by the Costa Rican Institute of Electricity, there is the option to launch the self-generation of electricity as an option to hotels and spas located near places with volcanic activity which at the same time are covered by the ICE’s distribution networks. That’s how the first local and regional project pilot dealing with the exploitation of low-enthalpy geothermal resources for self-consumption came to be. To start the project, some promising locations around the Miravalles and Rincón de la Vieja volcanoes were analyzed, all of them with the adequate range of temperature for electrical generation with this kind of geothermal resources. From there, the appropriate location was found: Hotel El Guayacán, situated inside the volcanic caldera of the Miravalles volcano, and which uses a hot spring (outflow) coming from the volcano. The heat source corresponds to a steam and gas escape in a place about 2 500 m2, with a temperature of 95 °C, a pH of 5.82, and high content of carbonates (HCO3-) and silicates (SiO2) among others. Since the pH value does not discard the use of steel piping, an all-steel ‘ad hoc’ heat exchanger was used to proceed with the tests. Among the fundamental information to define the power plant capacity, the team obtained the hotel’s electricity consumption, deciding on this data that it would be necessary to install a 5 kWe power plant to supply those needs and reduce the electric bill to almost nothing on even zero. Taking this in consideration and the temperature range mentioned before, an ORC power plant with an 8% performance was proposed, as mentioned before. Preliminary estimations shows that the total power output of the entire outcrop could reach 224 kWe.