Pumping heat

摘要

It was while hang-gliding that Jonathan Howes, a British aeronautical engineer, came up with an idea for a meteorologically powered engine to fly him between thermals, the columns of rising air which glider pilots use to gain altitude. It would use a thermal's updraught to turn a small turbine which captured some of the thermal's energy, for storage. Then, when in level flight, the pitch of the turbine blades would change and it would become a propeller driven by that stored energy. A neat thought. But what was truly novel was that the captured energy would be stored not as electricity in a battery, but as heat-or, rather, heat and cold-in two small reservoirs. Mr Howes has, however, yet to put such a device on his hang-glider because he is too busy building a far bigger version as part of the search for a cheap and reliable way to store electricity on the grid, a breakthrough which would transform the use of renewable energy.