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Hi. I am new to this community but have become very interested in
Stirling Engines and the potentual they have. We are in the process
of installing a 55 KW Stirling powered generator at the Wastewater
Treatment Facility I work at. It will be powered off of the Methane
gas we produce in our Anaerobic Digestors. The heat recovered off the
engine will be used to heat the Digesters along with a couple
buildings. The power produced will be used on-site to offset our
power costs.

My question is:

Can anyone tell me if anybody has looked at powering a Stirling using
heat from water such as sewer water (Wastewater). It may take a heat
pump to draw enough of the heat out of the water to raise the
temperature up to the level needed to power the Stirling. Wastewater
is ussually pretty warm. Thank You

Your present application of a Methane gas fired Stirling engine-generator is an excellent method of gas use and by product use of the waste heat.

It would be counterproductive to use a heat pump with the waste water to power another Stirling.

Heating Stirling with heat pump doesen't work, heat pump draws more energy than Stirling can produce, but there are these LTD (Low Temperature Difference) stirlings that can use lower temperature differences. Unfortenately they are big and unefficient, but if the energy is FREE like sunshine or geothermal, then it might be worth trying.

LTD low efficiency is due to low delta T., a consequence of the Carnot efficiency. There is a lot of effort wasted into trying to scheme a way to use atmospheric temperature to heat/cool an enclosed space such as a house.

The system of the OP is essentially a CHP, Combined Heat and Power unit. It burns the waste methane gas from the digester to run the Stirling engine, with a red heat at the hot cap, then uses the waste heat for heating offices etc. of the dispksal plant.

I'm sorry, I gave a wrong picture due my limited english. I ment to say that "forget heat pumps".

But if theres absolutely free "not-so-low" temperature difference to use, then it might be usable with Stirling if the power need is few watts...