Comparative life cycle assessment of geothermal power generation systems in China

This study concerns the assessment of the environmental impacts of geothermal power generation systems using life cycle assessment approach. Particularly, four types of typical geothermal power generation systems in China based on different technologies (double flash, single flash, binary and enhanced geothermal system) are involved in the case study, and critical environmental impacts of acidification potential, global warming potential and eutrophication potential are evaluated for the above geothermal power generation systems based on their energy system analysis models. Analytical results reveal that environmental impacts of geothermal power generation systems are significantly affected by well drilling process. In general, construction process contributes more than 60 % of acidification potential while running process is the major source of eutrophication potential. Environmental impacts vary for each geothermal power generation system due to their different configurations as well as reservoir conditions (namely geothermal gradient). Acidification potential, global warming potential and eutrophication potential of the cases are among 30.43∼250.05 mgSO₂/kWh, 3.88∼80.49 gCO₂/kWh, 4.78∼32.50 mgPO₄³⁻/kWh. In particular, environmental impacts of geothermal power generation systems can be largely reduced with a larger geothermal gradient, and it's the reason that South West double Flash geothermal power generation system is with the lowest environmental impacts.