Geothermal Steam Production by Solar Energy

Abstract

A concentrating solar power (CSP) prototype is testing close to AH-6 geothermal well in Ahuachapán geothermal field, El Salvador. The prototype consists of two small parallel parabolic trough concentrators (PTC) and thermal oil as heat transfer fluid (HTF). Heat gain from PTC could be a booster for current geothermal power during picks of demanding. The possibility of increasing steam fraction of two phase mixing geothermal fluid, separated geothermal water and heating condensed steam are the main objective of the testing. A theoretical increment of 5 kg/s of steam (equivalent to 2 MWe) from separated water, at under current bore field conditions and facilities, needs 40 kg/s of HTF heated from 170 to 270°C through a PTC field of 40 trough arrows of 200m long and 4 m wide (land size 250m X 500m) with a similar design and local materials for the testing prototype. El Salvador is located inside the zone of higher solar irradiation of Central America. Solar light ranges from 8 to 11 hours. Direct solar irradiance has been recorded between 314 and 722 W/m2. Direct normal solar energy flux has been observed between 2.9 and 6.0 KWh/m2/day that correspond to 90% both cloudy and sunny days, respectively. During a 90% clear day and PTC operation from 8:00 to 13:30 local hours, HTF temperature changed from 158 to 243 °C. An entire oil mass of 688 Kg gained 41.3 KWh of useful heat for a thermal power average of 7.4 KW. For these operating conditions, solar to thermal efficiency results small, only 10.5%. It should be acceptable since the current PTC prototype presents high optical and heat losses due to mainly reflector materials used and heat absorber pipe design. Improvement of those elements and/or application of accurate technology should produce efficiency as higher as 50-60%.