How to wring power from the night air

SOLAR POWER is all very well, but it is available only during daylight hours. If something similarly environmentally friendly could be drawn on during the hours of darkness, that would be a great convenience. Colin Price, an atmospheric scientist at Tel Aviv University, in Israel, wonders if he might have stumbled across such a thing. As he told a meeting of the International Union of Geodesy and Geophysics, held in Montreal in July, it may be possible to extract electricity directly from damp air—specifically, from air of the sort of dampness (above 60% relative humidity) found after sundown, as the atmosphere cools and its ability to hold water vapour diminishes.Dr Price’s apparatus is a pair of concentric metal cylinders. The outer cylinder is earthed while the inner one is not, creating a capacitor. Passing suitably moist air through the inner cylinder causes that cylinder to accumulate electric charge, thus creating a potential difference between the cylinders which could be harnessed to drive a current through an external circuit.