Valorization of Olkaria Brine Resources for Secondary Power Generation

Abstract

Geothermal two phase mixture flow reaching the surface consist primarily of a significant brine constituent of 50 - 90 % by mass, or from another point of view the volume in the two phase pipes is mainly of the steam component, since steam is about 80 times less dense than brine, and therefore occupies 80 times more volume by weight. In Olkaria only the steam component that varies from 50 - 10 % is separated from the mixture and utilized for generating electricity. The massive brine resource still contains extractable energy is currently left unused [estimated total separated brine is about 3,500 t/h = 682.5 MWt] that recovered at 5% efficiency would become new and free 34 MWe without need for additional drilling. As development of Olkaria fields progress beyond the current 200 MWe to over 600 MWe from the steam component only, additional brine resources will be at the disposal of the developers abundant with recoverable energy. Methods and approaches of utilizing this already available energy have been employed for a limited scope of direct uses, while the majority is re-injected back into the reservoir at separation. Expensive ORC machines exist to utilize the energy in electricity generation. The impact of lower reinjection temperature schemes is discussed.