High Value of Low-Pressure Geothermal Steam

Abstract

Over the pressure range of 1-20 bar abs where most geothermal power plants operate, a 10% pressure loss of saturated steam causes a power loss of about 12 kWe/(kg/s) steam flow rate (Le. electrical energy loss of 12 kJkg steam). For example, a steam pressure loss from 10 to 9 bar abs (1 bar drop = 10% loss) causes an electrical energy loss of 12 kJkg (at 80% turbine efficiency and 0.1 bar abs condenser pressure); but a pressure loss fkom 1 to 0.9 bar ab (0.1 bar drop = 10% loss) causes a loss of 13 kJkg. This is worth abut %4000/year per kg/s of steam at 5 cents/kWh and 80% plant factor. Hence, pressure loss of low-pressure steam costs much more than the same pressure loss of high-pressure steam. Therefore, attention should be paid to reducing pressure loss in low-pressure geothermal steam.