Performance of Solar Façade for Space Cooling During the Summer in the UK

The solar facade is an unglazed transpired solar collector that mounted on the side of the building which receives the most sunlight. It consists of two channels where the surface contact with the ambient environment (exterior) is a transpired aluminum plate. With fans-assisted system, the air adjacent to the front surface of the collector is drawn through the holes so that heat that would otherwise be lost by convection from the collector is captured by the airflow into the plenum. The wall in between that separates the two channels is a wetted wall made of sandtiles, where the surface expose to the cooled air channel is coated with water resistant material. Santile material is chosen so that meanwhile keeping the surface wet, retaining the water to minimise the excess water collected at the water tray. The air from the transpired absorber is high temperature air that heats the wetted wall and caused water evaporation on the wet surface. The hot air with moisture and heat is exhausted to ambient. Due to the evaporation process, wetted wall is cooled and at the same time it absorbs heat from the air in the second channel and hence cools the air in the second channel. The cooled air is then supplied to the room. Since the wetted wall is coated with water resistant material and moisture is brought out to the ambient, the air is cooled without additional moisture. A simple mathematical model is developed to study the performance of the system. The model shows that the hotter the ambient air temperature, the greater the air in the second channel will be cooled. During the hot months in the UK which is from May to August, the model predicts that the system with solar façade and wetted sandtile wall areas of 500m² each, it is able to reduce the ambient air temperature for about 3 to 6K.