Optimization of a Geothermal Multi–Generation Energy System: Energy, Exergy and Cost for Use in Coastal and Tropical Environments

Abstract

A considerable increase in global warming and climate change has seen in recent years; Resulting in effects as desertification of agricultural lands, changes in monsoon season, increase of floods, filling of land by rising sea level etc. At the same time, energy requirements are growing with the exponential increase of population, which most of the demand is covered by energy produced through fossil fuels. Fossil fuels has major drawback of releasing substantial amount of carbon emission, which is a major player in deteriorating the environment. As a result, extensive research is carrying on nowadays on utilizing renewable energy resources which provides clean energy with decreased emissions. In this paper, a multi-generation system is proposed to produce five outputs: electricity, hot water, cooling, drying-air and fresh water. Aim of the research is to design a stand-alone multi-generation system that can fulfill the energy needs of a small scale community/industry in the coastal or tropical areas in the region. This system uses isobutane-based, organic rankine cycle driven primarily from low/ moderate temperature geothermal resource to produce more than 0.8 MW of power and 150 tons of cooling capacity. Energy, exergy and cost analysis has been carried out to optimize the system. Being a coupled system, it maintains an efficiency of more than 20% under all ambient conditions with an overall exergic efficiency of more than 65%. Moreover, the effects of changing environmental temperature, changes in temperature of geo-water. Along with this, the effects of three different refrigerants have been studied.