Convert low temperature waste heat into power

[Screw1]

During compression, lots of heat is generated. With oil injected screw technology, this heat is approx. 60..80° above ambient. With oil free techonology, this can go up to 180°..200° above ambient.
This is quite some waste heat (80% of shaft input).
Is it feasible to convert part of this heat again into power, e.g. using stirling technology or ORC technology?
Or other kinds of technology?

 

[MintJulep]

You mean like this?

http://www.compressedairchallenge.org/content/library/factsheets/factsh10.pdf

http://www.domnickh.co.uk/tech_Cent...vation-and-Heat-Recovery_4.htm&getIndex=false

http://www.mne.psu.edu/me415/fall04/Kellogg3/

Or any of the several hundered other hits on the subject from Google?

 

[thermcool]

it is possible to generate power out of this waste heat but you have to see the returns from such powers generation. Generally the initial cost incurred on such systems is high but these give long time return.

you also have other option where you can use the waste heat for heating purpose directly. The more the conversion process you will add to any system the more complicated it will become and the less efficient at the same time.

 

[JStephen]

A lesson remembered from Thermodynamics class is that as the temperature differential drops, the maximum efficiency drops dramatically. So you may have gobs of waste heat there, but if the conversion is 2% efficient, you don't have much.

 

[toothless]

JStephen is correct. What you have is a lot of "low-grade" heat. If you need to heat an oil tank, a swimming pool, a greenhouse, etc., then you have something useful in this heat.

 

[thermcool]

well, this 2% energy hold out future

 

[willard3]

You could use a rankine cycle with working fluids other than water to produce work....big money, long payback.

80F above ambient will definitely heat domestic water or feedwater with low capital costs and short payback.

80F will also offset heating loads in outside air units with low capital cost and short payback.

Payback is also defined by cost of fuel which has spiked significantly lately and will make heat recovery much more attractive.

 

[unclesyd]

If you use cooling systems you should look at Chill-Vactors or Adsorption Refridgeration Machines. We use both to recover waste heat in your temperature range.

http://www.croll.com/_website/pr/vrefsys.asp

http://www.processrecovery.com/heat.htm

 

[Mattysdad]

in what form is the heat - hot water, hot oil, hot air ?

 

[davefitz]

for such a low temp, then the use of binary flids is resorted to.

For absorption air conditioning use of the heat, see the Yazaki literature (Li-Br). For power generation, see the Kalina literature ( NH3-H2O), as used in geothermal well applications.