Integration of PVT systems into a solar district heating network serving a small-scale Italian urban area

In this paper a district heating system including a solar field for solar energy recovery, a short-term thermal energy storage, a long-term double U-pipe vertical borehole thermal energy storage, a natural gas-fired back-up boiler and a heat distribution network is investigated. The plant is devoted to satisfy the energy demand for heating purposes and domestic hot water production of a small-scale urban district under the climatic conditions of Naples (south of Italy). The investigation has been performed by considering four solar field configurations consisting of different combinations of solar thermal collectors and photovoltaic/thermal panels covering the same floor area. The analysis has been performed with reference to a 5-year period by means of the dynamic simulation software TRNSYS. The predicted 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.