Apr 15, 2010

Inefficient power grid loses sixty percent of energy

The current system of generating electricity centrally and distributing it through the grid wastes as much as sixty per cent of energy -and it ain’t about to get any better, a leading UK academic has told Off-Grid.
Tim Green, Professor of Power Engineering at Imperial College London told us that efficiency losses in power generation are the biggest issue facing the power industry today.
He estimated that energy losses in the power grid during generation of electricity are between 45 per cent and 55 per cent, depending on the technology used. The transmission system run by National Grid which does the bulk shipping of electricity in the UK, loses a further two or three per cent. Local distribution networks run by big power companies have losses of between five and seven per cent.
“The local distribution networks have higher losses than National Grid because they operate at lower voltages,“ explained Professor Green.
Limited generating efficiency
But he said that it would be too expensive to make transmission more efficient and that generating efficiency is limited by the laws of physics. “(Transmission efficiency) could be improved if one was prepared to invest heavily in more wires and cables. But frankly it is not the biggest problem facing the industry.”
For networks, the real issues are how to accommodate low-carbon sources, such as wind, and still run a reliable and cost effective system, he said.
The story is very different for generation where he said efficiency is the biggest problem the industry has. “In energy generation you simply cannot achieve 100% efficiency -or anything close to it because of thermodynamic limitations such as maximum operating temperatures.”
However he was anxious to separate the issues of power generation and transmission, which he sees as unrelated, “It is highly misleading to lump generation and transmission networks together and give an overall loss figure because there are two different sets of issues at play and two different approaches needed.”
Of the conventional generating technologies, There are several competing generation technologies and some are more efficient than others, he said. “Combined Cycle Gas Turbines can achieve 55% efficiency or so and beats coal stations which do well to achieve 45%. If one can find a use for the “waste” heat in combined heat and power then the overall [efficiency] can be substantially better,” he says.
But he argued that conventional power sources compared well to newer technologies such as photo-voltaic, “Photo-voltaic panels have efficiencies in the range 10-25% depending on materials and cost.”

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