A BRITISH inventor said he had patented a wind-up radio that will run without batteries or electricity. The inventor, Trevor Baylis, said he planned to market the radio in Third World countries where people had little money to spend on batteries but needed news and information. ''There's quite a large spring . . . All one does is simply wind the thing up and as it slowly unwinds so it generates electricity, enough to run the radio,'' Mr Baylis said. How do people make solar energy? Solar energy is created by the sun. Humans can take the solar energy and convert it into electricity through the use of special man-made cells. These cells collect the sunlight and turn it into electric current through the use of chemicals. Brick (sun-dried) houses have long been known to collect heat during the day and release it at night.