DYNAMIC PERFORMANCE SIMULATION OF A SOLAR HEATING AND COOLING SYSTEM INCLUDING A BOREHOLE THERMAL ENERGY STORAGE SERVING A SMALL ITALIAN RESIDENTIAL DISTRICT Antonio ROSATO *,1 , Antonio CIERVO 1 , Francesco GUARINO 1 , Giovanni CIAMPI 1 , Michelangelo SCORPIO 1 , Sergio SIBILIO 1 *1 Department of Architecture and Industrial Design, University of Campania Luigi Vanvitelli, Aversa (CE), Italy * Corresponding author; E-mail: antonio.rosato@unicampania.it A centralized solar hybrid heating and cooling system satisfying the thermal, cooling and sanitary water demands of a typical Italian small district composed of six residential buildings situated in Naples (southern Italy) is modelled, simulated and analyzed through the software TRNSYS over a period of 5 years. The plant is based on the operation of solar thermal collectors coupled with seasonal borehole storage; the solar field is also composed of photovoltaic solar panels connected with electric energy storage. An adsorption chiller powered by solar energy is adopted for cooling purposes, while a condensing boiler is used as an auxiliary unit. The performance of the proposed system has been assessed from energy, environmental and economic points of view and contrasted with the operation of a typical Italian heating and cooling plant, highlighting the following main results: (i) saving of primary energy consumption up to 40.2%; (ii) decrease of equivalent CO 2 emissions up to 38.4%; (iii) reduction of operating costs up to 40.1%; (iv) simple pay-back period of about 20 years. Key words: borehole thermal energy storage; electric energy storage; solar energy; district heating and cooling; adsorption chiller. 1. Introduction The building sector consumes around 40% of the total energy consumption, and it is in charge of the major portion of the greenhouse gas emissions [1]. Solar district heating and cooling systems have attained relevant attention, playing a worldwide leading role with more than a thousand of applications installed [1]. Even if solar energy is easily and economically accessible in most part of the planet, one of the longstanding barriers to solar energy technology lies in the remarkable misalignment of solar energy availability with respect to heating requirements. Seasonal storages permit to store thermal energy for periods of up to several months, so that they could represent a challenging key technology for addressing this time-discrepancy. According to an extensive literature review, Rad and Fung [2] came to the conclusion that seasonal Borehole Thermal Energy Storages (BTES) are characterized by the most advantageous conditions for long-term energy storage thanks to the large amounts of energy involvement and relatively low cost of storage material. BTESs consist of closed- loops where heat is charged or discharged by vertical or horizontal Borehole Heat Exchangers (BHEs) which are installed into boreholes below the ground surface. After drilling, a “U” pipe is inserted into the borehole; the borehole is then filled with a high thermal conductivity grouting material. BHEs can