Marrying wind and hydro in Tasmania

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Market opportunities and green power were the main topics of discussion at the 4th Renewable Energy Technologies and Remote Area Power Supplies Conference held in Hobart, Tasmania, recently. The traditional focus of the conference, remote area power, gave way this year to an emphasis on integrating renewables into utility grid networks, reports Muriel Watt, a long time researcher at the Centre for Photovoltaic Devices and Systems

Watt, who presented a paper on assessing the value of renewables, says green power schemes were still the darling newcomer idea of the conference, but that utilities were just beginning to understand the value that renewables can add to their businesses. Inherent in this analysis, she says, was the use of life-cycle assessment as an objective comparison of energy options.

Although photovoltaics was the dominant technology discussed, there were updates on the planned Crookwell wind farm of 5 MW in New South Wales, due to be built this year, and Tasmania's new King Island wind plant. The major interest in wind, however, came from Peter Davis, general manger of energy services at Tasmania's Hydro Electric Corporation. Davis presented a paper discussing the potential of wind in the HEC's 2500 MW hydroelectric system, characterised by an average load of 1100 MW, a peak of about 1500 MW, and a demand that increased 4% last year.

Wind advocates have heavily criticised the HEC for failing to develop the island's substantial wind resource. Davis confirmed the belief in substantial wind potential by stating that four of the best coastal sites totalling 170 square kilometres has average wind speeds in excess of 7.5 m/s at a height of ten metres. These sites have the potential to generate 160-370 MW of wind power a year. Davis added that each of the four locations should contain enough individual wind turbine sites to construct a 100 MW wind farm that would generate about 350 GWh a year. A key feature of the Tassie wind sites, he said, is the narrow band width of the wind speeds, making periods of extreme wind or lulls fairly rare.

The location of the best wind resources is on the west coast of Tasmania, at least 25 kilometres from existing transmission lines, which would raise the cost of wind power there by about AUS$ 0.01/kWh. Davis noted, however, that some small wind farms could be connected to existing high voltage distribution feeders where good wind resource and spare capacity in the distribution lines exists.

Davis also said the addition of wind power to the state's run-of-river hydro stations presented some problems as these stations are given priority in load scheduling. When the combined wind production and run-of-river production exceed system demand, a spill of wind energy would occur and this could be 10% of wind production. Dumping this generation would push up the overall cost of the wind power.

Davis quoted a 1985 HEC study that showed a maximum penetration of wind at 10% of the total generation capacity, but added that recent changes to the HEC required this amount to be reconsidered. He also noted the possibility of feeding substantial wind power into the proposed AUS$500 million high voltage transmission link in the Bass Strait between the island and the mainland of Australia.

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