Life cycle CO2 emission assessment of an organic Rankine cycle based geothermal power plant

Abstract

Geothermal resources are well-recognized as a clean and low-carbon emission energy resource for power generation and heat supply. However, CO2 emissions occur during the construction, operation, and decommission stages of geothermal power plants. In this work, the life cycle CO2 emission characteristics of a geothermal power plant based on the organic Rankine cycle are systematically evaluated. The effect of the organic working medium and the recuperative cycle on CO2 emissions of the whole system are analyzed. Sensitivity analysis is conducted by varying the parameters of output power and the sources of the substituted electricity. Results reveal that a considerable amount of CO2 would be released due to the construction of geothermal wells and plants; however, the production of electricity could offset a much larger amount of CO2 emission. The net CO2 emission of the considered geothermal system during its lifespan reaches approximately −300 thousand tCO2e. In addition, the total amount of CO2 emission reduction relies heavily on the output power and the substituted electricity sources.