The processes of electricity production from geothermal resources at Olkaria IAU and Olkaria II Power Plants 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 plants, pinpoint the locations and quantities of exergy losses and wastes and suggest ways to address them and improve the overall performance of the power plants. Both Olkaria IAU and Olkaria II power plants share steam supply system and have a combined installed capacity of 336MWe from 6 generators In the analysis, the power plants were 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 IAU Power Plant has an overall second law efficiency of 45% and an overall 1st law efficiency of 15% while Olkaria II power plant has an overall second law efficiency of 42% and an overall 1st law efficiency of 14%. It was concluded that the lower performance of Olkaria II is likely as a reult of the aged equipment and recommended that a redevelopment of the plant may be necessary.

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