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The Age

Savings from the ground up

Author: Anne Thompson
Date: 17/04/2010
Words: 1097
Source: AGE
          Publication: The Age
Section: Domain
Page: 4
Geothermal pumps keep heating and cooling costs low and are efficient all year round, writes Anne Thompson.

MILLIONS of Europeans and Americans have installed geothermal heat pumps, reducing their power bills and minimising their carbon footprints. But Australians have been slow to link up with this underground energy source.

Geothermal heat pumps (or ground-source heat pumps) circulate liquid, usually water or antifreeze, through the earth. Heat can be transferred from the earth to the liquid (heating mode) or dispersed to the earth (cooling mode). The underground heat exchange reduces the amount of electricity that would otherwise be used to heat or cool a building.

Efficiency is increased because, unlike air temperature, there is little seasonal variation in ground temperature. Thirty metres below Melbourne, the ground temperature is consistently 12 degrees.

The year-round benefit of geothermal energy is reflected in the industry's catch-cry: Solar is good while the sun shines, wind is good while the wind blows but geothermal is good 24/7.

The Victorian government followed the same thinking when it named its 2007 geothermal energy pilot program the Four Seasons. The two-year program operated in regional areas where there was no access to natural gas. One million dollars was allocated to help cover installation costs and the program's spokesman, Shaun Inguanzo, says the pilot demonstrated a public interest in geothermal heat pumps. He says two factors are driving the response  the increasing cost of home heating and the desire for more sustainable energy.

Mr Inguanzo says interest in ground-source heat pumps is growing in both regional and metropolitan areas.

B'rush Ski Lodge in Mount Hotham received a Four Seasons grant in 2008. Now the heating and hot water in the 530-square-metre, split-level building link to two geothermal heat pumps.

Lodge member Murray Neilson drew on his skills as an electrical and electronic engineer to manage the project.

Mr Neilson prepared energy audits for the lodge before and after the system was installed. He presented his 2007-09 findings to the Alpine Resorts Sustainability Forum at Thredbo last year and says the economies would "wake the dead". Gas consumption has been virtually eliminated and electricity use has declined slightly. "We're saving about $10,000 a year," Mr Neilson says.

The technology for geothermal systems, which was commercialised overseas in the 1970s and 1980s, suits conditions here and Australian research is contributing to global expertise. In Victoria, the Centre for GeoExchange and Renewable Energy Infrastructure is continuing the work of the Four Seasons pilot.

Melbourne company Direct Energy installs geothermal heat pumps in residences and businesses throughout Victoria. These are "direct geo-exchange systems", where refrigerant is run through underground copper pipes, says technical director Donald Payne, Direct Energy

co-owner with Justin McFarlane. "Most people think of hot-rock type geothermal, where you're going down three to five kilometres to generate electricity. That's different from what we are doing here.

"We're effectively using solar energy. We're not actually using the core's heat. We're using the stable temperature in the ground  only 30 metres into the ground  which is the sun's energy that has been stored there for many, many years."

Direct Energy uses a refrigerant that boils at minus 10 degrees. The ground heat boils the refrigerant, changing it from liquid to vapour, thus creating energy. For cooling, the reverse applies.

"The ground is changing the state of the refrigerant for us  for free," Mr McFarlane says.

"With a conventional airconditioning system you have a fan box with a coil inside and it's sucking or blowing hot or cold air across the coil, trying to change the state of the refrigerant, which can use a lot of energy. Geothermal systems are very efficient."

Once installed, a geothermal heat pump system looks much like any other heating or cooling system, using regular ducting, radiators or coils and thermostat controls. Outside the house, the system is unobtrusive. The pump unit is about the size of a bar fridge  and makes a very similar sound.

"You can put them inside your garage, plant room or attic," Mr Payne says. "There's a lot of flexibility because you don't require that air flow, which you do for a conventional system."

Drilling costs lift the price of installation above that of a conventional system. Three to six holes are usual for a typical house. "Each hole provides  in Victoria  about 3? kilowatts of heating or cooling capacity. A normal home will need anywhere from 10 to 20 kilowatts," Mr McFarlane says.

Cheaper running costs mean the pay-back period can be as soon as five to seven years, he says. "Savings can be up to 70 to 80 per cent. In a normal home, 80 per cent of the billing is on heating, cooling and hot water production. We can save up to 80 per cent of that energy usage."

Contacts

Centre for GeoExchange and Renewable Energy Infrastructure, phone 0409 971 988

cgrei.com.au

Direct Energy, phone 8598 0686 directenergy.com.au

Less power to the people

THE inspiration for Surrey Hills resident James Blyth to install geothermal technology came when he saw British design expert Kevin McLeod explain the benefits on his television show, Grand Designs.

"We were renovating our old Californian bungalow, which had no heating or cooling, so we knew we'd have to install something anyway," Mr Blyth says. "We liked the idea of being environmentally friendly, so we investigated further."

The installation was not trouble-free  an inconvenience lessened because Mr Blyth was not actually living in the house at the time.

"The drillers found a river about 20 metres below ground level," he says. "We had our own gushers and it took around 10 long days to get the holes drilled and the pipes put down into the ground."

The initial setback has not affected the ongoing running of the system. Geothermal-assisted airconditioning, ducted ceiling heating and hot-water service the four-bedroom house. Mr Blyth says nothing unusual is required for the upkeep of the above-ground units  not so the external system.

"The installers came back and did a top-up to the underground pipes  just like you add antifreeze to your car."

Some 2? years later, Mr Blyth is enjoying his green heating and cooling system.

"The heat and cool coming from the system is different from normal heating," he says. "The cooling is softer  not like an arctic wind blowing through."

Having not lived in the house before the geothermal system was installed, Mr Blyth says he cannot compare the before-and-after running expenses but he is happy. "We're using less power. We moved from a house about half the size of our current home but our fuel bills have remained pretty constant, which suggests (given there's inflation, too) that geothermal is a fair bit cheaper to run."

 
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