Heat naturally flows from hot things to cold things, and since there are few places colder than the vacuum of space, that’s a great place to beam excess heat. A Stanford University (US) team has developed a roof-mounted system that can cool a building by doing just that. The process is called radiative sky cooling, and its goal is to cool homes and buildings without using any external power source. The specially designed panel draws thermal radiation out of the building at a wavelength that allows it to pass through the Earth’s atmosphere and straight out into space. The system is used to chill water, which is then be piped through a building to cool it. The next step in the development is to integrate these cooling panels into air conditioning and refrigeration systems. One of the main applications they are targeting is the mammoth task of cooling large computer data centres.