District heating systems based on low-carbon energy technologies in Mediterranean areas

Heating and cooling are responsible for 70% of energy consumption in European buildings, with renewables covering only 18%. To reduce emissions in the building sector, district heating based on low-carbon energy is identified as a key technology for the transition to a low-carbon economy. However, currently only 16% of thermal district networks are based on biomass, and around 3.2% on solar. This paper analyses the application of solar and biomass district heating systems in the low-to-moderate population density areas of the Mediterranean. These areas are characterised by high solar and biomass availability, and lack of space restrictions, along with particular challenges for implementation. A methodology for viability analysis and optimised integration is presented. The methodology is applied to a case study in the south of Spain. The results show that with a linear heat density greater than 1.5 MWh/m, there could be viability with internal rates of return higher than 7.4 and 9.8%, and payback period below 13 and 10 years, for solar and biomass systems respectively. The use of seasonal thermal energy storage allows the solar fraction to be increased from 55 to 75%. Sizing and design strategies for their viable implementation in Mediterranean areas are extrapolated from the analyses.