Sustainability Assessment of Most Relevant Solar Thermal Heat Systems
Abstract
Solar thermal heat systems are of high relevance and interest for the supply of low temperature heat for different purposes. Especially, hot water systems are dominating the solar-thermal market with non-pumped systems gaining more and more importance. The main objective of this paper is to assess most relevant small and medium sized as well as large scale district solar-thermal heat systems as to their sustainable development metrics. While 2017 about 94% of the energy provided by solar thermal systems was used for domestic hot water, currently a trend to larger solar thermal systems with seasonal storage coupled to district heating networks is discernible. Solar thermal at present contributes about 1% to total heat consumption. The share of solar district heating and solar process heat applications is steadily increasing despite it is still only representing 3 % of the global market (Weiss and Spörk-Dür, 2018). The potential contribution is much larger. Many national governments seek to realize this potential by offering subsidies and feed-in-tariffs. Assessing sustainable development for solar thermal heat systems is a complex discipline. The best heat system depends to a large extend on the climate region. If solar heat is intermittent, seasonal, economic storage of heat is advantageous. Significant cost reductions of solar thermal systems and a shift towards polymeric materials to regain market growth and to improve ecological performance is required. For the assessment a 5-step methodology developed by Ashby et al. (2016) is used.