Solar panels cool water by radiating heat into air. Image credit: A. Raman/Stanford University
The scientists at Stanford University, California have developed a cooling system which is capable of reducing the inside temperature of a building in a very hot (desert) climate condition by over 20% with the help of specially designed solar panels without increasing the electricity consumption or water evaporation.
We have been hearing about solar water heaters, but this technology developed at Stanford University when gets implemented commercially will lower the cost of industrial-scale air conditioning and refrigeration drastically.
These new water cooler solar panels that are necessarily installed on the rooftop, are made up of three components. The first component is a plastic layer with a silver coating which reflects nearly 100% incoming sunlight, thus keeps the panel away from heating up in the summer days, during the scorching heat. The plastic layer sits on the top of the second component- a coiled copper tube. Water is circulated through this tube, in turn, it sheds heat to the plastic. Then this heat is radiated out by the plastic on top of the tube at a wavelength which is in the range of the infrared (IR) spectrum, this can not be absorbed by the atmosphere and instead, goes all the way to outer space. Finally, the whole panel is encased in a thermally insulating plastic housing, this ensures that almost all the heat radiated away comes necessarily from the circulating water and not from the surrounding air.
To conduct the actual field trial the scientists recently placed three such water cooling panels on the roof a building at their university campus. Each panel area was 0.37 square meters. Water was circulated through these at the rate of 0.2 litres every minute. The result they reported was, this setup cooled the water as much as 5°C below the ambient temperature. The test was conducted over 3 days. Later they modelled o show how their panels would help if integrated with a typical air conditioning plant for a two-story building in Las Vegas, Nevada. The results were astonishing and this setup would lower the electrical demand required for air conditioning by almost 21%. The scientists have recently published the detailed report in the magazine Nature Energy.