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Joined: Jan 2004
Posts: 615
Jps1006 Offline OP
In this article:
they mention using these generators in a grid-connected way. I have also read and heard about residential applications where you can use solar and/or wind power to "spin the meter backwords".

Has any of you ever done any of these types of installations? How does this work?

I noticed something in the article about sycronizing to the grid. How does that work? anyone ever done this?

I would love to at some point in the future (after extensive research and some training I'm sure) get into these types of energy conserving installations. I'm sure once you run the cost recovery numbers it isn't too hard of a sell. I think as our demand for energy increases and our supply decreases, we will eventually be forced to some of these trickier installations.

And just as a personal opinion, I think it is a disgrace to burn natural gas for nothing other than heat such as a furnace or hot water heater with out extracting electricy out of the burn such as in the types machines in the article. I'm sure there are collectively megawatts of power going up our flues every day (for those of us in natural gas areas) Every heat producing appliance should be a generator at the same time.

Joined: Nov 2002
Posts: 456
At the efficiency of modern fuel burining heating appliances, I don't think there is really enough residual energy to cost effectively extract. If you have "mid" efficiency appliances and are worried, upgrade to high efficiency appliances.

Joined: Apr 2002
Posts: 2,527
There has been some of this Out West. Search on “E-NET metering” at the California Energy Commission, Pacific Gas and Electric, SoCal Edison and San Diego Gas and Electric. For under 10kW, it is possible but it’s a lot of work just getting the utility to accept a new system. There are a lot of hoops to jump through. The respective utilities are very specific on what they’ll accept for interconnection. UL Standard 1741, IEEE 929 and [for photovoltaics] NEC 690 are enforced to the letter. Good luck.

Joined: Oct 2000
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Broom Pusher and
There have been quite a number of Co-Generation applications done in Commercial areas.

Worked on one which employed two 60 KW 480 VAC 3Ø Gennys (connected in Parallel) as an auxilliary power source with options to sell power back to the PoCo.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Sep 2003
Posts: 650

These microturbine units don't work by recovering energy that the fuel burning appliance wastes. As you note, modern fuel burning appliances are _very_ efficient, in terms of thermal energy released by the fuel versus thermal energy delivered to whatever you want to heat up.

Instead you should think of these microturbine systems in which electricity is generated relatively inefficiently, but then the waste heat goes to heating up something that you were going to heat up anyway.

With a modern gas water heater, you might put 98% of the thermal energy of the fuel into the water. With one of these turbines, then if you are lucky 30% of the thermal energy of the fuel is delivered as electricity, and maybe 55% or 60% is delivered as heat to your water, and 10% or 15% goes up your exhaust stack.

However the system is viable because electricity is a much more valuable form of energy than heat.


Joined: Jan 2004
Posts: 615
Jps1006 Offline OP
Hey guys, thanks for the responses. Scott thanks for the keyword. I'm curious who was responsible for jumping through all of the red tape on your job. i.e. utility and emmisions issues. And how does it syc. with the utility?

Jon, I think it works a little differently than that. I had it explained this way: first of all your 92% efficient gas furnace isn't really 92% effecient. It can extract 92% of the thermal energy, but that's not all of the energy. When you burn gas it expands. That expansion of molecules can be used to do work as well with no effect on the amout of heat produced. So the concept is to have the expansion of the burn turn the turbine for electricity and then take the heat (which you would have produced anyway) and use that for heating. I was told a 92% furnace really is only using around 50% of the available energy.

Joined: Nov 2002
Posts: 456
But on a high efficincy furnace, the exhaust is fan forced, and most of the the force on that is produced by the fan.

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