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Power Generation - Compressed Air vs. Superheated Steam

07/27/2009 7:58 AM

i want 2know that is it in thermal power plant compressed air can be used in the place of super heatd steam for production of electrical energy? YES or NOT, if yes then tell that upto what pressure the air can be compressed so that this air can rotate the turbine as per the required speed?

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Guru
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#1

Re: regarding power generation

07/27/2009 8:03 AM

It's not generally done, because air's latent heat cannot be used at ordinary conditions of temperature and pressure to be found in a power plant. Steam is a much more useful fluid than air in that respect, as thermodynamic cycles using it lead to greater thermodynamic efficiency than were air to be used, which is important to power generation organisations.

The maximum pressure that any fluid can be built up to is related to the strength of the materials containing it and the ratio of their cross-sectional areas. There is a limit, which is the yield stress of the metals forming the container, and metals are stronger in this respect than non-metals.

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#2

Re: Power Generation - Compressed Air vs. Superheated Steam

07/27/2009 9:02 AM

Compressed air would be part of the cycle of a gas turbine? I would therefore advise you google information on the subject.

Regards JD.

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#3
In reply to #2

Re: Power Generation - Compressed Air vs. Superheated Steam

07/30/2009 5:00 AM

When compressing air, heat is also generated.

Minimum compressor work is done for isothermal compression, but in a gas turbine it is adiabatically heated. This is no problem as that heat doesn't need to be supplied by the fuel.

Stored compressed air has cooled down to ambient temperature so that heat loss has to be supplied when burnt in a turbine.

On the other hand, if low cost off peak power can be used to generate the compressed air, it could still be worthwhile as not only is the energy used to make it cheap, but gas turbines can be brought on line very quickly and hence are good for peak lopping.

Wet compressed air is a dead loss as the water used to cool the air on compression all condenses out when the air cools down.

Limits to pressure are essentially dictated by the cost of the required pressure storage vessel. It could be feasible to use old mine shafts to store quite high pressures, but this isn't always available.

Generally, the cost of compressing air makes it uneconomic as an energy storage.

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