Hot pavement used as solar technology
SCHARWOUDE, Netherlands — If you've ever blistered your bare feet on a hot road you know how asphalt absorbs the sun's rays. Now, a Dutch company is siphoning the heat from roads and parking lots to heat homes and offices.
As climate change rises on the international agenda, the system built by the civil engineering firm Ooms Avenhorn Holding BV doesn't look as wacky as it might have 10 years ago when it was first conceived.
Solar energy collected from a 200-yard stretch of road and a small parking lot helps heat a 70-unit four-story apartment building in the northern village of Avenhorn. An industrial park of some 160,000 square feet in the nearby city of Hoorn is kept warm in winter with the help of heat stored during the summer from 36,000 square feet of pavement. The runways of a Dutch air force base in the south supply heat for its hangar.
And all that under normally cloudy Dutch skies, with only a few days a year of truly sweltering temperatures.
The Road Energy System is one of the more unusual ways scientists and engineers are trying to harness the power of the sun, the single most plentiful, reliable, accessible and inexhaustible source of renewable energy.
Ooms' thermal energy system is too expensive and inefficient to solve the world's energy problems. In fact, it was actually a spin-off of a method to reduce road maintenance.
A latticework of flexible plastic pipes, held in place by a plastic grid, is covered over by asphalt, which magnifies the sun's thermal power. As cool water in the pipes is heated, it is pumped deep under the ground to natural aquifers where it maintains a fairly constant temperature of about 68 F. The heated water can be retrieved months later to keep the road surface ice-free in winter.
The same system pumps cold water from a separate subterranean reservoir to cool buildings on hot days.
Though it doubles the cost of construction, the system's first benefits are a longer life for roads and bridges, fewer ice-induced accidents and less need to repave worn surfaces.
"We found we were gathering more energy in summer than we needed, so we asked a building contractor what we can do with the extra energy," said Lex Van Zaane, the commercial manager. The answer was to construct buildings near the tarmac and pipe hot water under the floor.
The installation cost is about twice as much as normal gas heating, but the energy required is about half of what would otherwise be needed.
Experimental technologies involve new methods to concentrate the sun's energy by using mirrors or lenses, or devices that track the sun's path across the sky. And scientists are working with electrochemical cells using a liquid rather than a solid component to absorb light.
