Thermodynamics Applied to Geothermal Power Plants: Case Study—Unit 5, Cerro Prieto, Baja California Mexico

Cerro Prieto Geothermal Power Plant has a capacity of 720 MW. The earliest 5 units are 23 years old, and unit 5 from Cerro Prieto Uno was restored in 2008. This paper presents a thermodynamic analysis on the effects that has the increase of non condensable gases content in geothermal steam. Results show that the cooling water temperature will rise due to the energy entering the system with the water flow of the new vacuum system that feeds the condenser. Normal operation would be limited and there exists a risk of not sustaining the condenser’s pressure. The new vacuum system, should extract from the condenser a flow 4 times larger, requiring 27% more steam at a higher pressure, as well as 4.5 times the quantity of cooling water. At this condition, the water returning to the condenser is 4.3 times larger than the original at a higher temperature, increasing in 218% the associated energy. A thermal behavior model was obtained for the cooling tower. In the most likely scenario the cooling tower exit temperature will be higher than the required, and to maintain the equilibrium it will be necessary to lower the condenser thermal load by reducing the steam flow to the turbine and accordingly, the power delivered.Copyright © 2011 by ASME