Vacuum flash geothermal power plants: second law analysis and optimization

Hibara et al. (1990) describe the concept of a vacuum-flash geothermal steam plant. The idea involves the use of near-boiling-point water available at numerous hot spring areas. The authors show that a steam plant using a vacuum pump to create the flash process for steam generation can compete thermodynamically and economically with binary plants of small capacity. However, the "thermal efficiency" they quote is very low (1.4%) and might discourage the use of such a scheme. This paper examines vacuum-flash plants using second law analysis, a thermodynamically appropriate method to assess the performance of the system (Moran, 1982; DiPippo and Marcille, 1984), and the results are both more revealing and more encouraging.