500 kW direct contact pilot plant for East Mesa

A 500 kW powerplant utilizing a direct contact heat exchanger (DCHX) between the geothermal brine and the isobutane working fluid is nearing completion at the East Mesa Component Test Facility. The primary purpose of the plant is to evaluate the performance potential of the direct contact system in a size much larger than the small exploratory units that have been tested to date. Thermodynamic performance of DCHX binary power systems has been demonstrated in small 10 kW research test rigs (Refs. 1, 2, and 3), however, characteristics that affect the economics and practicality of long term operation need to be evaluated. Three factors influencing plant performance and cost are: (1) the control of noncondensables that contaminate the power cycle condenser, (2) the equipment required to limit working fluid losses, and (3) the control of scaling or performance robbing deposits in critical components. These factors are not unrelated and control of one often impacts control of the other two. Operating data and research with the 500 kW pilot plant should demonstrate a solution to all three of these factors and provide design guidelines for larger plants.