In matters of clever design, nature has often got there first
Jan 21st 2012 | from the print edition
A virtuous spiral
SOLAR-POWER stations take up a lot of room. They need either vast arrays of photovoltaic panels, which convert sunlight directly into electricity, or of mirrors, which direct it towards a boiler, in order to raise steam and drive a generator. The space these arrays occupy could often be used for other purposes.
Two researchers from the Massachusetts Institute of Technology have now devised a better and more compact way of laying out arrays of mirrors. Slightly to their chagrin, however, and somehow appropriately, they found when they had done the calculations that sunflowers had got there first.
Alexander Mitsos and Corey Noone started with the observation that existing concentrated solar-power plants, as those which drive boilers are known, usually have their mirrors arranged in a way that resembles the seating in a cinema. The mirrors are placed in concentric semicircles facing a tower, on top of which the boiler and the turbine sit. That arrangement, however, sometimes results in the mirrors shading each other as the sun’s position in the sky changes, even though the mirrors are usually attached to robotic arms that track the sun as it moves.
According to their report in Solar Energy, Dr Mitsos and Mr Noone found that they could do better. They divided each of the mirrors in a real power plant, PS10, in southern Spain into about 100 pieces. (Or, rather, they divided a computer representation of each mirror.) They then plugged each of those pieces into a computer model that calculated all of the energy losses by noting points where mirrors were not optimally oriented to the sun and places where they hindered one another by blocking incoming or reflected rays. It then rejigged them into a better arrangement.