Uncovered PVT collectors for night radiative cooling of buildings

摘要

The potential of using uncovered photovoltaic-thermal (PVT) collectors for night radiative cooling of buildings is studied both theoretically and experimentally. Within the competition Solar Decathlon Europe 2010, large PVT modules have been installed on the roof of a small residential zero energy building and were used to dissipate, during the night, the heat stored in the building (in a water store and a PCM ceiling). Mean cooling power between 40 and 65 W/m~2 have been measured depending on the sky conditions and the temperature levels with electrical COP between 17 and 30. Additionally, a simulation thermal model has been developed and validated against measurement data. The model was used to simulate the energy concept of the house mentioned above for the climate of Madrid. The night cooling system covers directly more than 40 % of the cooling loads through the PCM ceiling and the activated floor in free cooling. Also, the PVT collectors allow a very efficient operation of the reversible heat pump in cooling mode (SPF 4.3) by maintaining low temperatures in the water store. Finally, the potential of night radiative cooling is investigated numerically for different climates and different operating conditions of temperatures and mass flow rates.