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Publisher's Letter

Gas-fired trigeneration is a worthwhile concept

While you may be concerned about your ever-increasing energy bills, there is another electricity problem that may soon confront a lot of Australians: power blackouts. The truth is that all the eastern States have a chronic shortage of electricity generators. For a variety of reasons, the States have not been building new coal-fired power stations and they are increasingly using the available generation capacity. And while they have been trumpeting wind farms and roof-top solar installations, these will provide a very small fraction of the total demand.

It will only need a series of very hot days this summer or perhaps a major power station or grid fault to cause some serious blackouts. And since all the eastern States, including Tasmania, are interconnected, the blackouts could potentially be state-wide or even more extensive.

There is no easy solution to this problem. Since there is a lack of generating capacity and since everyone with an air-conditioner is likely to run it whenever the temperature rises, the result is likely to be power rationing to wide areas or worse, the blackouts may be sudden and widespread. Or maybe the authorities will be proactive and if very hot weather is predicted, they may appeal to consumers to curtail their use of air-conditioning.

All of which makes a recent proposal by Sydney’s Lord Mayor, Clover Moore, all the more interesting. Ms Moore is proposing that all of the Sydney CBD should be powered from small gas-fired trigeneration plants. Undoubtedly, this is partly to appeal to inner-city “green voters” anxious about “carbon emissions” but it makes a lot of sense anyway.

While many readers are probably familiar with gas-fired co-generation plants, they may not be familiar with trigeneration, which is not a new concept, incidentally. Co-generation refers to a plant which typically has a gas-fired turbine running an alternator to generate electricity. Waste heat from the exhaust of the gas turbine is then used to flash water into steam to drive a steam turbine and alternator to generate more electricity. Trigeneration typically takes waste heat from the water condensate of the steam turbine to run an absorption refrigeration system for air-conditioning. Other variations use the waste heat for heating in a building.

Whatever variant is used, it is a great deal more efficient than coal-fired power stations or gas-fired co-generation plants and that means that far less hydrocarbons are burnt to generate a given quantity of energy, so that is a big advantage. Furthermore, the proposed trigeneration plants would be installed in existing buildings and would no doubt be able to be brought on line much more quickly than any large conventional power plant.

The concept also has the advantage of being a local power source which means that there are less transmission losses from the point of generation to where it is used.

Of course there has been criticism of the idea. One problem to be solved, apart from matters like planning regulations and finance, is the large quantity of natural gas that will be required and whether existing supplies in the city will be adequate. And some people have been concerned about the amount of local pollution that might be created by these gas-fired plants. I would say, “Don’t worry about it!”

After all, any pollutants generated by clean-burning gas turbines are likely to be minimal compared to those from all the diesel-powered standby generators already present in the central business districts of our State capitals. Many of those standby generators are already committed to the grid via lucrative contracts with electricity distributors.

So if you notice a haze over your capital city during hot days this summer, it could well be due to those diesel generators.

Maybe we really should consider nuclear power!

Leo Simpson


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