Thermo-economic sensitivity analysis by dynamic simulations of a small Italian solar district heating system with a seasonal borehole thermal energy storage

Solar energy is a promising option for reducing both energy consumption and harmful gas emissions. Seasonal thermal energy storage is a challenging key technology able to minimize the mismatch between the availability of the solar energy and the thermal energy demand. In this paper, a solar district heating system (basically composed of a solar collectors array, a short-term thermal energy storage (STTES), a long-term borehole thermal energy storage (BTES), an auxiliary natural gas-fired boiler and a heat distribution network) has been analysed by means of dynamic simulations over a 5-year period when serving a district composed of 6 typical single-family houses under the climatic conditions of Naples (center Italy). A sensitivity analysis has been carried out by simulating 27 configurations obtained by varying solar collectors area, volume of STTES and volume of BTES. The simulations results have been compared with those associated to a conventional heating system in terms of primary energy consumption, carbon dioxide equivalent emissions, operating costs as well as simple pay-back period in order to (i) evaluate the potential benefits, (ii) explore the influence of the components size on the system performance and (iii) establish some simple rules for the initial design of the main subsystems.