Comparison of photovoltaic and solar thermal cooling systems for office buildings in different climates

Abstract

Photovoltaic systems combined with electrical compression chillers offer a high potential for energy efficient cooling with a high economic feasibility. Due to much higher energy efficiency ratios of electric chillers compared to sorption cooling systems, the heat rejection system is much smaller and thus auxiliary energy and water consumption lower than in sorption cooling systems. The overall system efficiency, auxiliary energy consumption and achievable solar fraction depend on the photovoltaic module technology, the compression chiller energy efficiency ratio and obviously on the temporal correspondence of solar cooling production and cooling demand. A systematic simulation study was carried out to evaluate the overall performance of photovoltaic compression cooling systems in office buildings for different climatic conditions worldwide. For each location and cooling demand the solar energy production for different surface areas was calculated and solar fractions, EER and auxiliary energy demand was determined. It could be shown that the primary energy savings for solar electric cooling and heating are comparable to solar thermal systems. As solar thermal systems include hot storage, they mostly provide higher solar fractions and in some cases higher primary energy savings. If electricity export to the grid or for appliance use is included in the primary energy analysis, photovoltaic cooling systems always have higher primary energy savings.The total cooling costs for solar electric cooling are comparable to solar thermal cooling systems, if there is no feed in tariff for the excess PV electricity. If a grid export is possible and paid for, solar electric cooling systems are always more advantageous.