A Life Cycle Assessment Based Comparison of a Large and a Small Scale Geothermal Electricity Production System

Abstract

Greenhouse gas (GHG) emissions from fossil fuel electricity production cause a big problem on global warming. Using renewable energy, such as wind, solar and geothermal energy, is a more sustainable solution to produce electricity. During the operating phase of a geothermal energy power plant, there are much less GHG emissions compared to conventional power plants. But how sustainable are geothermal electricity production systems considering the whole life cycle, from construction, operation to closure of the power plant? Most research on the life cycle assessment (LCA) of geothermal energy (GTE) systems is conducted on largescale geothermal power plants (installed capacity > 5MW) to assess their environmental performance. Little is known on the LCA of small-scale GTE systems. In this study the environmental impacts of a large-scale GTE flash system (with an installed capacity of 110MW) is compared with a small-scale binary GTE system (the installed capacity is 500KW) using LCA, for the construction and operation stages. The results showed that a small-scale binary system is more sustainable when considering the deep well drilling process and power plant building during the construction phase, while a large-scale flash system shows a better environmental performance when considering the process of power plant machinery production and pipeline construction. A small-scale binary system is more sustainable in the operation phase as there are no gas emissions.