A techno-economic analysis of a high vacuum solar system integrated into a prosumer-based district heating network

Sharing thermal energy from distributed solar plants through district heating networks is recognized to be crucial in the transition to 100% renewable systems. However, few studies have explored the benefits and challenges for users who install solar thermal plants and sell surplus heat to the network, thus becoming “prosumers”. Through a validated model of a bidirectional district heating substation, this paper examines the feasibility of integrating high vacuum solar thermal technology into an office building connected to a district heating network in Mediterranean regions. The heat generated by solar collectors is utilized not only during the heating season but also in the cooling period through an absorption chiller, with the possibility of delivering the heat surplus to a thermal network. The study investigates different scenarios based on different sizes of the solar system to analyze the impact on energy savings and profitability. Results show that being a prosumer highly increases the exploitation of the heat produced by the solar plant and lets it cover up to 73.8% of the heating demand by solar energy and up to 43% of the cooling demand by the absorption chiller. The economic analysis indicates that incorporating an absorption chiller may render the investment unprofitable, highlighting the need for a targeted financial support system. Moreover, the importance of minimizing thermal energy curtailment is evidenced. The present work provides a preliminary assessment of the potential benefits and challenges arising for a thermal prosumer with high-vacuum collectors in Mediterranean regions with moderate climatic conditions while pointing out the future routes to be investigated for promoting the spread of small-scale solar prosumers in district heating and cooling networks. • The energy and economic benefits of high-vacuum solar collectors and an absorption chiller in a Mediterranean office substation are analyzed. • The impact of the solar plant size and energy curtailment on the selling price of heat is examined. • Bi-directional heat exchange with DHN increases the exploitation of solar energy. • In colder regions, up to 28.6% of the heat from the solar plant can be sold to the network. • The inclusion of an absorption chiller increases the minimum selling price of the heat by 23.5%.