Contents lists available at ScienceDirect Resources, Conservation & Recycling journal homepage: www.elsevier.com/locate/resconrec Full length article Comparative life cycle assessment of geothermal power generation systems in China Yongzhen Wang a,b , Yanping Du c , Junyao Wang d, *, Jun Zhao b , Shuai Deng b , Hongmei Yin b a Department of Electrical Engineering, Energy Internet Research Institute, Tsinghua University, Beijing, 100084, China b Key Laboratory of Efficient Utilization of Low and Medium Grade Energy, Tianjin University, Tianjin, 300350, China c China-UK Low Carbon College, Shanghai Jiao Tong University, Shanghai, 200240, China d Guangdong Research Center for Climate Change, Sun Yat-Sen University, Guangdong, 510006, China ARTICLEINFO Keywords: Geothermal power generation system Environmental impacts Life cycle assessment Geothermal reservoir ABSTRACT 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 mgSO 2 /kWh, 3.88∼80.49 gCO 2 /kWh, 4.78∼32.50 mgPO 4 3- /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 geo- thermal power generation system is with the lowest environmental impacts. 1. Introduction In 2017, hot dry rock (HDR) with a temperature of 236 °C was exploited in Gonghe basin of Qinghai province in China (Anon, 2019). This represents a significant breakthrough of drilling and exploitation with HDR and enables the use of new methods for geothermal power generation in China, namely geothermal power generation based on enhanced geothermal system (Luo et al., 2012; Li et al., 2014; Cheng et al., 2014, 2016; Noorollahi et al., 2017). Until now, there are four configurations of geothermal power generation system (GPGS) avail- able in China: the double stage flash power plant exploiting high-tem- perature geothermal energy, located in South West; the single stage flash power plant, adopted for utilization of medium-temperature geothermal energy, located in South East; the binary power system based on organic Rankine cycle (ORC), suits for utilizing the low-tem- perature geothermal energy, located in North East; and the enhanced geothermal system (EGS) that will be constructed in North West. In fact, geothermal energy is enormously distributed all over the world, and it can be converted into electric energy as a base load for its advantage of stability (Siouane et al., 2017). Compared to other renewables, such as solar energy and wind energy, geothermal energy is more stable as it uses water, steam as energy medium (Bertani, 2016; Lund, 2011; Rubio- Maya et al., 2015). Therefore, the capacity factor of GPGS can be as high as 74 % or more and the total capacity of geothermal power generation system (GPGS) is expected to be more than 160 GW in 2050 (Goldstein, 2020). However, GPGS is currently challenging for larger scale application as its high cost (Zhao et al., 2016). As a consequence, solar energy and wind energy are preferably utilized as the primary renewable energy in most countries, while the total capacity of geo- thermal power plants in the world is only 12 GW in 2015 (Martinot et al., 2005; Bajpai and Dash, 2012; Roland, 2012). Thus, methods for improving the energy efficiency and economic and environmental im- pact of GPGS need to be developed. Numbers of researchers have conducted systematic optimization studies on different GPGSs. For example, Clarke and McLeskey (2015) performed the multi-objective optimization for a binary geothermal https://doi.org/10.1016/j.resconrec.2019.104670 Received 7 September 2019; Received in revised form 25 November 2019; Accepted 26 December 2019 ⁎ Corresponding author at: Guangdong Research Center for Climate Change, Sun Yat-Sen University, Guangdong, 510006, China. E-mail address: wangjunyao_hkust@126.com (J. Wang). Resources, Conservation & Recycling 155 (2020) 104670 Available online 07 January 2020 0921-3449/ © 2020 Elsevier B.V. All rights reserved. T