Enhancing Geothermal Power Project Performance and Sustainability by Repowering with Bottoming Cycles

Abstract

Many existing geothermal power plants have unutilized geothermal energy which, if tapped, could provide additional generating capacity in a cost effective manner, without the need to drill new wells. Such untapped energy is found in the separated brine and at times in excess steam pressure between the well head and the power plant turbine inlet. The ability to increase power production, by modest amounts can lead to significant increase in profitability. Furthermore, adding power production without drawing further on the resource serves to create an economically viable and sustainable project. This paper shall focus at the case histories of several geothermal re-powering applications utilizing brine, including the 5MW brine recovery binary power plant at the Brady power plant in Nevada installed in August of 2002, the 10 MW brine recovery binary power plant at Momotombo in Nicaragua operational since early 2003 and the 20 MW Miravalles V brine recovery plant installed by ICE Costa Rica. The experience of these plants and others demonstrate that cold injection of brine, after the energy has been converted into electric power, can be accomplished without causing problems of scaling in the heat exchangers of the power plant, injection piping system or well bores, and without affecting the productivity of production wells.