Retrofitting a Geothermal Power Plant to Optimize Performance: A Case Study

Abstract

Performance evaluation of a 12.8-MW single-flash design geothermal power plant in Northern Nevada is conducted using actual plant operating data, and potential improvement sites are identified. The unused geothermal brine reinjected back to the ground is determined to represent about 50 percent of the energy and 40 percent of the exergy available in the reservoir. The first and second-law efficiencies of the plant are determined to be 6 percent and 22 percent, respectively. Optimizing the existing single-flash system is shown to increase the net power output by up to 4 percent. Some well-known geothermal power generation technologies including double-flash, binary, and combined flash/binary designs as alternative to the existing system are evaluated and their optimum operating conditions are determined. It is found that a double-flash design, a binary design, and a combined flash/binary design can increase the net power output by up to 31 percent, 35 percent, and 54 percent, respectively, at optimum operating conditions. An economic comparison of these designs appears to favor the combined flash/binary design, followed by the double-flash design.