Novel Energy Sources... Heat from the Street

cy

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A new way of collecting solar energy

SOMETIMES, the simplest ideas are the best. To absorb heat from the sun efficiently—to use it, for example, to heat water—you need large, flat, black surfaces. One way to do that is to construct those surfaces specially, on the roofs of buildings. But why go to all that trouble when cities are full of black surfaces already, in the form of asphalted roads?

This was the thought that occurred ten years ago to Arian de Bondt, an engineer who works for a Dutch building company called Ooms. Eventually, Dr de Bondt persuaded his employers to follow it up. The result is that their headquarters in Scharwoude is now heated in winter—and also cooled in summer—by a system that relies on the surface of the road outside.

The heat-collector itself is a circuit of connected water pipes. Most of them run from one side of the street to the other, just under the asphalt layer. Some, however, dive deep into the ground.

In summer, when the surface of the street gets hot, water pumped through the pipes picks up this heat and takes it underground through one of the diving pipes. At a depth of about 100 metres lies a natural aquifer into which a series of heat exchangers have been built. The hot water from the street runs through these exchangers, warming the groundwater, before returning to the surface via another pipe. The aquifer is thus used as a heat store.

In winter, the circuit is changed slightly.

http://www.economist.com/science/tq/displaystory.cfm?story_id=9933350
 
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