| Title | Exergy Analysis of Olkaria I Power Plant, Kenya |
|---|---|
| Authors | Clety Kwambai Bore |
| Year | 2010 |
| Conference | World Geothermal Congress |
| Keywords | Geothermal, Exergy, Energy, Efficiency, Second law analysis |
| Abstract | The processes of electricity production from geothermal resources at Olkaria I Power Plant in Kenya were analysed using exergy analysis method. The objectives of the analysis were to determine the overall second law (Exergy) efficiency of the power plant, pinpoint the locations and quantities of exergy losses and wastes and suggest ways to address the exergy losses and wastes. In the analysis, the power plant was simplified into sub-systems, each with distinct exergy inflows and outflows and approximated into steady state flow. The theory and mathematical formulations were adapted from the book ‘Exergy methods of thermal plant analysis’ and several online internet publications. Mathematical models for exergy flows were developed and analysed using the Engineering Equation Solver (EES) software to perform the calculations. The degree of thermodynamic perfection (measure of performance) was based on the rational efficiency concept. Few assumptions and simplifications were made. The results showed that Olkaria I Power Plant has an overall second law efficiency of 42% and an overall 1st law efficiency of 15%. The analysis revealed that 6 MW exergy is wasted in the separated brine while 11 MW exergy is lost in the steam transmission system. Significant losses were found to occur in the turbines, condensers and the GES system. Although the exergy in the wasted brine is relatively small compared to that in the steam, it could still be put to useful work at some investment cost. It was concluded that exergy analysis is an important tool for analysing the performance of geothermal plants and should be incorporated into their designs. It was suggested that the steam transmission system should be investigated further to determine the causes of exergy losses and that ways of utilising the exergy in the brine be investigated. |