A laptop computer can double as an effective portable knee-warmer — pleasant in a cold office. But a bigger desktop machine needs a fan. A data centre as large as those used by Google needs a high-volume flow of cooling water. And with cutting-edge supercomputers, the trick is to keep them from melting. A world-class machine at the Leibniz Supercomputing Centre in Munich, for example, operates at 3 petaflops (3 × 1015 operations per second), and the heat it produces warms some of the centre’s buildings. Current trends suggest that the next milestone in computing — an exaflop machine performing at 1018 flops — would consume hundreds of megawatts of power (equivalent to the output of a small nuclear plant) and turn virtually all of that energy into heat.
Read the article here http://www.nature.com/news/computer-engineering-feeling-the-heat-1.11993
