Feasibility of operation of the existing geothermal resource of the south-east sector of the Miravalles geothermal field, Costa Rica

Abstract

Due to increased fuel costs and the global energy crisis, geothermal energy plays a key role as a clean, renewable and cheap energy source to be considered a proper energy substitute for fossil fuels. The main objective of this report is to propose possible exploitation systems of the geothermal resource in the east-southeast sector of the Miravalles geothermal field by using data obtained from wells already drilled at this site. The wells already drilled show a non-condensible gas (NCG) content ranging from 1.52% to 13.09% (weight based). Several candidate power cycles were analyzed and their power output calculated. For each cycle, options regarding NCG extraction were studied. Finally, a preliminary technical and economical comparison was made between the candidate cycles to investigate feasibility of operation. The results show that the lowest cost in terms of capital cost per kW was achieved with a single-flash cycle with a binary bottoming cycle. Close in cost was a double-flash cycle with a binary bottoming cycle. The second system has the advantage of low sensitivity to NCG composition which is an important advantage in the field under consideration.