Approximately $7000MW$ of geothermal electricity are produced worldwide. The process is that naturally occurring steam or hot water that is not far below the earth's surface $($for example, hot spring$)$ is brought to the surface and used to heat a working fluid in a binary fluid power generation cycle, such as that shown in Fig $5\mathrm{.}1.($Geothermal water $($and steam$)$ are not directly injected into a turbine, as the dissolved salts and minerals would precipitate and quickly damage the equipment.$)$ For geothermal water at temperatures less than $200C,$