Primary Energy Saving Potential of Solar Cooling in Residential Buildings

Cooling in residential buildings becomes more important due to the rising insulation requirements and the increasing human comfort. Therefore, systems that provide heating as well as cooling with a low primary energy consumption will be in future more preferred than conventional single-unit systems. Solar thermal installations can here provide in addition to the domestic hot water and heating demand a significant contribution to the cooling requirement in residential buildings. In this study, low-energy residential buildings with different solar heating and cooling systems are analyzed concerning their primary energy consumption. To cover a large range of different weather conditions, two locations (Madrid and Wu¨rzburg) with different solar energy supply are considered. Further, a conventional solar heating supply system including one or more typical room air-conditioners is as reference system selected. The different systems are modeled by the system simulation platform TRNSYS. In a first step, the question is addressed of whether a solar thermal system with standard dimensioning, taking the domestic hot water and heating demand into account, is sufficient to meet the cooling requirements. To cover the cooling demands, a small-scale thermally driven absorption chiller has been selected. In a next step, the studied systems are compared in terms of primary energy saving as a function of the solar cooling fraction. The simulation results have shown that regions with a high solar energy supply do not take advantage of solar thermal cooling, due to the higher cooling demand. On average, 70% of the cooling demands can be covered by a standard dimensioned solar thermal system. At the same time, a primary energy saving up to 90%, compared to currently installed room air-conditioning units can be achieved.