RENEWABLES: Just Look Beneath Your Feet

By Sanjay Suri Reprint | | Print |

Sanjay Suri

BONN, Jun 7 2004 (IPS) - When they planned this new building in Bonn with renewable energy in mind, they decided to do no more than look beneath their feet.

Look to a depth of just about 20 metres. Because at that depth they found water at a steady temperature of 11 degrees C all year around. A good deal warmer than the freezing surface temperatures in the winter.

And so architect Karl-Heinz Schommer designed a building that would draw warmth from that water. Two wells were dug to draw water to heat the building. A heat pump was installed to bring the temperature up to a level enough to heat the building to about 20 degrees.

The pump works on a conventional energy source. But the temperature differential between ground water and piped water alone was enough to cut energy costs significantly.

"It really is very simple," Stephan Willers from Baehr Engineering which constructed the building told IPS. "People did not think of doing this before because there was no sense of an energy crisis."

What came up above the ground was designed to add efficiency to what came up from below. Schommer designed the building with clever use of glass surfaces to let in maximum sunlight through the year. "We optimised use of the heating pump by drawing a heating curve to work out just how much it needs to be used."

The result is that "one kilowatt of electricity now leads to six kilowatts of heating," says Willers. For purposes of this building it could mean many fewer barrels of oil to buy from Saudi Arabia.

Fine for Germany, but what about buildings in Saudi Arabia or in other hot tropical areas? The same geothermal technology can work there to help cooling rather than heating. Baehr is in fact engaged in construction projects using this technology in Saudi Arabia, Korea, China and Greece.

Temperatures 20 metres or some more below are a good deal less than surface temperatures. No wells can be dug in a desert but water storage tanks below will cool water from surrounding earth. That water can be drawn for efficient cooling, with alternating replenishment and withdrawal in a ‘pendulum’ system to ensure that surrounding earth maintains its relative cool.

"The earth is a big storage tank; we can draw energy from it but we also sometimes have to recharge it," says Willers.

Heating from the earth is being used by more than 75,000 homes all over Germany now, not always with the help of water drawn from a well. "They dig in a loop of pipes into the earth to a depth of 40 to 100 metres, and the relatively warm water coming in through the earth cuts energy costs by 60 percent," Uwe Burghardt from the ministry for transport and energy in the state of North-Rhine Westphalia told IPS.

The state government provides some subsidies for this, and an average home recovers the investment costs within about five years. "For a home owner this can mean very substantial savings then on," he said.

The state got its geology map to prepare temperature readings and the earth profile of the whole of the state to varying depths down to 100 metres. That data was put on a CD and offered for sale. Search facilities can provide data on the earth profile below every house in the state.

The CD priced at 10 Euros (12 dollars) was soon sold out. More are being prepared now to meet heavy public demand.

"Use of geothermal technology by 75,000 households in a total of 22 million is not a lot, but this is very recently developed technology and it is picking up fast," Burghardt said.

Digging that deep is still only scratching the surface of the earth, really. "You can get temperatures of around 100 degrees if you go down to a depth of about 2,000 metres," Dr Heinz Wilder from the Geological Service of North-Rhine Westphalia told IPS at its centre in Krefeld, one- and-a-half hours drive from Bonn. In this part of Germany, the earth gets hotter by about three degrees every 100 metres you go down.

Germany has set 100 metres as the limit for private drilling. Below that it becomes state property.

A good deal of Italy has a more fortunate gradient for geothermal energy purposes, Dr Wilder said. Far hotter temperatures are reached closer to the earth surface, and that means that geothermal energy can potentially be accessed more easily.

In France access to deep geothermal at Soulz sous Foret near Strasbourg has already produced heating energy being put to commercial use. Germany is experimenting with drilling down to 3,000 metres in Aachen in a first attempt to use deep geothermal energy.

Much of the world has begun to dig into its own backyard for energy. A Geothermal Implementing Agreement (GIA) in 1997 was extended for a further period of five years in 2001.

The agreement seeks to bring together national programmes for exploration, development and utilisation of geothermal resources. The programme is supported by the International Energy Association.

The European Commission, which is the European Union’s executive arm, and nine countries (Australia, Germany, Iceland, Italy, Japan, Mexico, New Zealand, Switzerland and the United States) had joined the association as of last month.

New successes have brought new realisation that the way forward may be the way down.