Energy assessment of thermal solar-powered district heating and cooling networks for a cluster of buildings in Mediterranean climate

Abstract

The urgent need to cut carbon dioxide emissions in buildings is pushing towards efficient, eco-friendly solutions for meeting heating and cooling demands such as renewable-based district heating and cooling networks. In this context, very few studies have investigated the potential of these technologies in Southern Mediterranean regions, characterized by predominant cooling demands and large availability of renewable energies. In this respect, this work proposes an energy analysis of modern district networks composed of solar collectors, absorption chillers, heat pumps, and thermal energy storage, serving a cluster of buildings in Southern Italy. Using a dynamic model for a double-loop ring network and solar plant developed in Transient System Simulation tool, different scenarios are simulated. Specifically, a baseline scenario, where thermal demand is met individually, is compared with low-temperature (60-85 degrees C) and ultra-low-temperature (7-20 degrees C) networks. An examination of primary energy consumption, carbon dioxide emissions, temperatures, and pressure within the network reveals that the proposed improvement scenarios lead to energy savings respectively from 62% to 82% compared to autonomous heating and cooling systems. Additionally, ultra-low temperature district reduces heat losses in pipes by 67.4% compared to low-temperature operation. However, the energy needed by booster heat pumps in the case of an ultra-low temperature network leads to higher primary energy consumption of a factor of 2.1 compared to the case of a low-temperature network. The present work provides a picture of the energy and environmental benefits achievable by these innovative systems in cooling-dominated areas, underlying the need for future research for spreading these systems in these regions.