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Posted by D Sherman [72.47.9.228] on Wednesday, July 13, 2011 at 18:08:03 :
In Reply to: Re: Goin Solar. O/T posted by mannyc [68.165.89.2] on Wednesday, July 13, 2011 at 09:15:44 :
A lot of people who are setting up natural-gas fired gen-sets are making use of the cooling water either for space heating or domestic hot water (hopefully via a heat exchanger -- I wouldn't want to drink water that's been through an engine). If you work out the numbers, and have a use for the heat, this turns out to be an extremely efficient way to burn natural gas. The electricity that comes out of it is very nearly free if you compare this system to an ordinary gas-fired water heater (60-70% efficient).
Of course the downside is maintenance compared to a simple water heater. If you leave an engine running all the time just to produce hot water, you've got to consider not just the cost of lube oil and filters, but occasional overhauls. On the other hand, if you were planning to run a natural gas fired gen-set a lot of the time anyway, it's definitely worth the extra plumbing to make use of what would otherwise be waste heat.
A spark-ignition internal combustion engine is typically no better than 40% efficient at the flywheel without accessories. That means 60% of the energy goes out the radiator. If you can pipe that hot coolant though, say, hydronic heating coils, or even just put the genny in a shed next to the shop and have it circulate shop air rather than outside air through the radiator, you're way ahead in terms of energy savings.