Solar thermal systems for sustainable buildings and climate change mitigation: Recycling, storage and avoided environmental impacts based on different electricity mixes

Solar thermal systems play a pivotal role in the building sector. However, for the development of sustainable energy systems, different parameters should be taken into account. The present article sets out to present a multidimensional approach. To this end, the first part of the article discusses energy policies, placing emphasis on solar thermal applications. The second part of the article is based on Life Cycle Assessment (LCA) and evaluates the environmental performances of a thermal-energy-storage device and other components appropriate for solar thermal systems for buildings. The analysis has been based on global warming potential, cumulative energy demand, ReCiPe and USEtox. The results show that steel and copper are the materials which are responsible for the major part of the storage-device impact. Based on ReCiPe endpoint/with characterisation, steel and copper present 2.2E-03 DALY (damage to human health) and 5.9E-06 (species.yr) (damage to ecosystems). The results show that the metallic components have the highest environmental impacts. By involving recycling, a remarkable reduction in these impacts can be achieved. Issues related to building-integrated solar systems and future prospects are also discussed. Moreover, the avoided impacts due to the use of a solar thermal system instead of using a conventional electric heater for hot water production have been evaluated, considering multiple environmental indicators. The results based on the Spanish electricity mix have been compared with those based on the Italian electricity mix. In both cases, the findings verify that solar thermal systems offer considerable avoided environmental impacts.