Energy and exergy analysis and comparison of different configurations of geothermal- fuelled poly-generation systems

Abstract

This paper presents and investigates several configurations of poly-generation systems fuelled by medium and low temperature geothermal water. Poly-generation has become an option that is being explored intensively to be implemented in geothermal systems of different countries, sinc e it offers the possibility to increase the use of geothermal energy by generating electric power, thermal energy, refrigeration or air conditioning (or other forms of usable energy) simultaneously, from a single source of primary energy. In this study, different configurations of poly-generation systems are developed and modeled, which allow to analyze and select a system of auto-generation, to replace conventional forms of energetic supply, based on technological energy proposals and exergetic analysis. These poly-generation systems consist of a subsystem based on an Organic Rankine Cycle (ORC), a cooling subsystem based on an absorption machine with Thermally Activated Technology (TAT) and heat exchangers for energy direct uses. The main objectives are to identify the best configuration to produce electricity, cold and heat with higher efficiency, as well as to determine opportunity areas to improve each of the system configurations. A detailed energy and exergy analysis is performed in the EES software environment taking into account geothermal sources at the temperature range of 80 - 150°C. The developed codes allow a wide energetic and exergetic analysis of different configurations of cycle-arrangements that integrate poly-generation systems. Finally, a poly-generation configuration that satisfies energetic requirements posed with the intention to improve geothermal energy use efficiency, based on energy and exergetic performance parameters is selected.