Potential for geothermal energy 'huge'

ALEX FENSOME
Last updated 05:00 03/10/2012

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A guest speaker at the Southland Energy Conference believes geothermal energy is possible in Southland despite the notable lack of volcanoes and hot springs.

Many New Zealanders think of geothermal as large-scale electricity projects using volcanically superheated water, such as seen around Taupo.

But in Europe, particularly Scandinavia, heat naturally stored in the ground is used to warm buildings.

Brian Carey, the head of government research body GNS Science geothermal department, will give a talk on the technology in Invercargill tomorrow night.

Mr Carey said geothermal heat pumps, using heat naturally stored in the ground or in water, had huge potential in New Zealand.

To heat a building, coils of pipes are laid underground near a building and filled with fluid. Heated to a natural 6 or 7 degrees centigrade, the fluid is fed into a heat pump.

"You take heat from the ground and use a little bit of energy from electricity to pump it to a higher temperature," Mr Carey said. "We're talking the top few metres of the ground."

If there was a groundwater source near the building, that water, naturally around 10-12 degrees, could be used. The heat was then fed into the building through underfloor pipes.

He said seawater could also be used to cool a building - in summer, much of Stockholm's CBD is cooled by water from the Baltic Sea.

To cool, the principle works in reverse. Cold water, from the sea, or a lake, is fed to the heat pump before being pumped into the building.

It could work anywhere in New Zealand, even in Southland, he said.

"The temperature in the ground [in Southland] is warm enough," Mr Carey said. "It gets replenished by solar energy . . . it's a big storage for that."

The technology was not yet suited to most homes because of the cost of retrofitting, he said.

But it could be used on high-end new build houses and large buildings such as schools and stores.

"Dunedin Airport has got a system which uses aquifier water for all its heat and cooling."

Other New Zealand examples include the Te Wharewaka building on Wellington's waterfront.

GNS Science research into the Swedish heat-pump market showed the cost of installing a system was $30,000, but technology had advanced so much it was paid back within 10 years.

Mr Carey said GNS had helped to set up the Geothermal Heat Pump Association, of which he was chairman, to spread knowledge of the technology.

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- The Southland Times

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