Life cycle assessment of a future central receiver solar power plant and autonomous operated heliostat concepts

Up-scaling in power plant size and new innovative concepts in the solar field design are among the most promising ways to reduce the costs of future concentrated solar tower power plants. Besides the economic benefits, the knowledge about the ecological impacts of new concepts is of increased interest in view of the climate targets set. This paper aims to assess the ecological impacts of two autonomous operated heliostat concepts within a future solar tower power plant. Both concepts include a photovoltaic (PV) energy supply for the heliostats, combined with either an LiFPO4 or an LiNMC battery system. Both are compared with a conventional energy supply system. The analysis for comparing the different heliostat concepts is embedded in a life-cycle assessment (LCA) of a 440 MW solar tower plant with a 12,166 MWhth molten salt thermal storage. For the solar tower power plant and the autonomous operated heliostat concepts new LCA inventories were developed. The environmental impacts assessed include the Global Warming Potential (GWP), which is found between 15 and 105 gCO2eq/kWhel, for the entire solar plant depending on the share of fossil fuel co-firing. Indirect life cycle emissions excluding fossil fuel co-firing and thus associated with the life-cycle of the power plant components show, that the conventional solar field is the main contributor to GWP with 9.5 gCO2eq/kWhel. Results for both autonomous concepts demonstrate, that reductions in the impact on climate change are at about 10% compared to the solar field with conventional heliostats. Thus it is demonstrated, that heliostat concepts with an autonomous renewable energy supply lead to considerable reductions in life cycle emissions.