Going underground for clean energy
What’s the secret to cooling your home on a hot summer’s day, while cutting back on greenhouse emissions? You might just be walking on it.
Guillermo Narsilio is working on technology which uses the cool temperature of what’s underneath the ground to chill down buildings. This can cut carbon emissions by up to 75 per cent compared with traditional air-conditioning.
But there’s a catch. Narsilio says there’s a “fear factor” associated with the technology, which has rarely been used in Australia. So his team from the University of Melbourne is not just researching the technology, its installing and monitoring it.
“If people are not aware, they will never use it,” says Narsilio, a geotechnical engineer (he studies soil and rocks). “We’re trying to let Australians know about this technology.”
The team installed the technology – called “shallow geothermal” – in the Elizabeth Blackburn School of Sciences near the University campus in Melbourne.
28 boreholes were drilled 50 metres below ground. Plastic pipes carry water underground, where the temperature is a steady 18 degrees C, then return it to the surface. In summer the air above is usually warmer than the soil, so the water cools down the building via a heat pump. The system works in winter too; the soil is usually warmer than the air, so the heat pump uses that warmer water to heat the building. (This is different from the geothermal technology which sinks much deeper boreholes into hot rocks to generate electricity).
This can cut carbon emissions by up to 75 per cent compared with traditional air-conditioning.
The school’s 120 kilowatt system does use electricity – to circulate the water, and for the heat pump – but less than conventional heating/cooling systems.
“The key for us is to reduce energy consumption,” says Narsilio, who studied in Argentina and the US before taking up a research fellowship at the University of Melbourne in 2006. (He liked it so much he stayed, and is now an Australian Research Council Future Fellow.)
The school installation cost about $200,000 and saves money through lower energy bills. In other countries, systems are paying for themselves through lower bills in as little as two or three years.
Shallow geothermal is quite widely used for heating in Europe and the US, and Narsilio thinks it can take off in the southern hemisphere. His team, co-led by Professor Ian Johnston, has taken calls from India, Thailand and Mauritius, although Narsilio thinks geothermal may work best in temperate climates. “We’re in ideal conditions,” he says of Victoria.
The school is part of a program the University’s Department of Infrastructure Engineering is running to instal shallow geothermal at 30 properties across Victoria – homes, commercial buildings, etc. It’s funded by the Victorian government and involves engineering companies Geotech and Direct Energy. It’s the largest monitored shallow geothermal project in the world.
And researchers are teaming up with academics from Cambridge University, which has expertise on the mechanical side of geothermal energy. Links have been formalised and Melbourne PhD student Olga Mikhaylova, originally from Russia, will study at Cambridge in 2015.
Narsilio, who has the habit of sizing up buildings around the Melbourne University campus to see if geothermal can be installed – the answer is often yes – thinks the public is ready to hear more about geothermal.
“People are in general interested, people ask me, ‘tell me more’,” he says. “There is no logical reason I can see for this not taking off.”
Image couresty of Peter Casamento
Geotechnical Engineering Researcher
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