This method makes use of the exposed thermal mass of a building to be cooled by the outside air during the night. Exposed concrete floors are the most effective cooling medium. Vaulted or coffered soffits offer the maximum radiant surface. The cooling stored in the fabric is released as radiant cooling or an air stream directed over surfaces during the day. Vents or windows are automatically opened at night to admit the cool air. During the day warm air is vented to the atmosphere. The fact that it is radiant cooling may allow the air temperature to be slightly higher than the norm whilst still maintaining comfort conditions.
Night cooling of a high thermal mass structure can offset about 20-30 W/m2 of heat gain during the day, reducing the peak temperature by about 2-3°C.
The system is optimized if there is cross ventilation and internal solar gains are kept to a minimum. The method works best if there is a large diurnal temperature range with night temperature below 20°C. Also, the best results are achieved in narrow open plan spaces, say 15 m maximum between façades. There is the limitation that heat gains should not exceed 30 W/m2.
Was this article helpful?
The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.