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Bright winters

Bright winters

作者:巫座  时间:2019-03-07 01:02:05  人气:

By Michelle Knott IT MAY seem like madness to try to grow strawberries in the middle of a Swedish winter, but it’s possible. And farmers at such high latitudes could double their winter yields with acrylic panels that deflect more light onto the crops, say Australian researchers. Plant growth depends on both the temperature and the amount of light available for photosynthesis. However, when you install double-glazing to keep greenhouses warm, the glass reflects more than 20 per cent of the winter light away from the crops. But Ian Edmonds and Darren Pearce from the Queensland University of Technology believe that you can almost double the amount of available light in winter by replacing the inner layer of glazing with laser-cut acrylic panels. The extra light should have a dramatic effect on the crop yield. “At low light levels the increase in crop yield is directly proportional to the increase in illuminance,” says Edmonds. The pair describe their scheme in the latest edition of the journal Solar Energy (vol 66, p 255). The panels have a series of fine, parallel grooves. When light hits them, it is deflected down onto the crop by a combination of refraction and internal reflection. “On the face of it, it sounds like an excellent idea,” says Barry Robertson, horticultural services manager at the John Innes Centre in Norwich. “If you can cut down on supplementary lighting, it’s one of the biggest savings you can make.” Edmonds says that the scheme should be most useful at latitudes between 40° and 60° in countries where the sky tends to be clearer in winter, such as in the northern US,