A prototype solar device that produces enough hot air from the sun's rays to drive the turbines of a 50 kw power station has brought the prospect of cheap, solar-generated electricity a step closer. The solar energy collector has been successfully tested by Israeli researchers at the Weizmann Institute of Science, Jerusalem. Many modern power stations use hot gas to drive the turbines that produce electricity. The gas must be between 1,200 and 1,350 c and must reach pressures of between 10 and 30 bar. Existing solar collectors, which focus the sun's rays on tubes of air, cannot do this. The new device focuses the sun's rays through a quartz window to heat ceramic pins around which air flows. The array of pins --- which researchers have nicknamed the 'porcupine' -- absorbs solar energy and transfers it to the air. As the ceramic pins have a large surface area they transfer heat to the surrounding air very efficently.