Exergetic and Energetic Analysis of Power Generation from Geothermal Resources in Pakistan

Abstract

World is presently facing an unprecedented energy challenge. This situation is even graver in developing and under developed countries like Pakistan. Future solution of this challenge lies in harnessing renewable and other sustainable energy resources. Geothermal energy is one of such options. This paper presents an analysis of possibilities of exploiting this resource in Pakistan. Geological research underlines presence of several geothermal resources in country. Most of the geothermal resources of the world lie near the seismic belts and Pakistan too is situated in the western rifted margin of Indo-Pakistan sub continental plate. The presence of geothermal resources is strengthened by the development of alteration zones and fumaroles in different regions of the country, presence of hot springs and indication of quaternary volcanism. There exist several medium and low temperature geothermal sources up to temperatures of 200°C in different areas of Pakistan. The present work addresses the idea of power generation from geothermal energy sources in Pakistan. The work encompasses the review of geothermal resources in Pakistan and the application of engineering principles for the exploitation of these resources. The work includes a comparative Energetic and Exergetic study of different geothermal power plant concepts, based on the source temperature. Cycles incorporated in this study are simple Organic Rankine Cycle (ORC), Organic Rankine Cycle with an Internal Heat Exchanger, Regenerative Organic Rankine Cycle & Regenerative Organic Rankine Cycle with an Internal Heat Exchanger. A thermodynamic model is developed for ORC and validated using available data from literature. Numerical and analytical analysis is carried out for finding the optimum working conditions and working fluid. The performance of each configuration of cycle has been analyzed in terms of energetic & exergetic efficiency, exergy destruction rate, fuel depletion ratio, relative irreversibility and productivity lack. It is observed that the increase in geothermal source temperature results in an exponential increase in maximum cycle output and a linear increase in turbine inlet temperature. It is also proposed to use internal heat exchanger and regeneration to increase the effectiveness of cycle.