Wednesday 19/12/2007 Page: 12
WHEN it comes to renewable energy it has long been a case of use it or lose it - until now. Two companies - one using solar energy, the other using wind energy - are deploying new technology to crack the problem of how to preserve excess energy and make what has been a feelgood exercise for individuals into a viable power source for entire communities.Storage for renewable energy has largely been limited to compressing air underground, where it can later be released under pressure, or pumping water high above ground and capturing the energy in turbines when gravity pulls the water back down. Both techniques are effective, but they require suitable locations and much infrastructure.
The new solution, developed over the past six years by an Australian scientist, Robert Lloyd, overcomes the obstacles by harnessing energy that would be wasted. It uses graphite - as in graphite pencils - to absorb and retain heat for extended periods. The energy can then be redeployed as superheated steam that spins a turbine on demand rather than merely when the wind blows or the sun shines. "By using this energy storage system... we can add significant value to solar or wind energy so it is worth more in the market... " says the chief executive of Lloyd Energy Storage, Steve Hollis.
His company is designing renewable energy sites for Cloncurry in north-western Queensland, and Lake Cargelligo in western NSW. The Queensland project is set to make Cloncurry, population 4828, the first town in Australia to depend exclusively on solar power. Nearly 7200 mirrors will aim sunlight into holes in the bottoms of 54 elevated graphite cubes and heat them to up to 1800 degrees for steam turbines.
Similarly, CBD Energy, which has licensed the Lloyd technology, will build a windpowered version of the graphite system on King Island. The island, 85 kilometres north-west of Tasmania, relies primarily on diesel to generate power for its 1800 residents. The $15 million joint venture between CBD Energy and Hydro Tasmania will not make the island wholly powered by renewable energy, but it aims to eliminate the need for 1.25 megalitres of diesel fuel a year, says CBD's chief engineer, John Giannasca.
To achieve this, CBD will install two megawatts of wind turbines to supplement an existing system as well as six graphite blocks, each one the size of a standard shipping container. A few solar panels will be also be available for periods when the island is without wind. All of these would feed a 250-kilowatt steam turbine for power, Giannasca says. CBD Energy would heat its graphite blocks to 800 degrees.
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