Life cycle assessment (LCA) of solar thermal tower power plants

Abstract

Due to the growing world population and its increasing energy demand, the construction of new power plants is inevitable. At the same time, it is necessary to keep the rise of the global average temperature well below 2 °C compared to pre-industrial level in order to significantly reduce the impacts and risks of climate change. Therefore, an environmental friendly energy infrastructure is required to reduce greenhouse gas emissions. Solar thermal power plants are a promising technology, as they provide the possibility to buffer solar energy in a thermal storage. Thus, it can produce electricity according to the demand and is independent of meteorological fluctuations. A life cycle assessment is necessary to assess the environmental impact of a solar thermal power plant and its individual components. This work analyses the extent of the environmental effects of solar thermal tower power plants in the following selected impact categories according to the CML-method: Global Warming Potential (GWP 100 years), Abiotic Depletion potential (ADP elements), Eutrophication potential (EP) and Acidification Potential (AP). The most ecologically relevant components are identified and modelled with different specifications in order to compare the influence of different building types. Furthermore, the life cycle assessment model is applied to different geographical locations in order to enable site-specific considerations. The selected locations are Upington in South Africa, Evora in Portugal and Calama in Chile. The life cycle inventory is generated based on an extensive literature research and forms the foundation for the modelling of solar thermal tower power plants in the LCA software GaBi ts. As a result, the most ecologically relevant components are determined. A comparison of the different locations allows statements on the ecological potential of solar thermal tower power plants at a specific site. The heliostats and the molten salt (MS) as heat transfer fluid and storage medium dominate the impact on the GWP 100 years. The heliostats consist mainly of steel and glass and are needed in large numbers. The molten salt is used in a high amount and consists of a mixture from sodium nitrate and potassium nitrate which both have a high impact on GWP. Moreover, the transport and the construction on site have relevant contributions to GWP. The impact of the transport results from the large mass of all shipped components. The impact of the construction on site has copper cables as the main contributor. The end-of-life scenarios have a significant effect on the total impact. Depending on the recovery of the metals and especially the further use of the molten salt, the environmental impact is decisively influenced.