Electricity Generation From Stove?

I was just thinking, it might be cool to use some of the heat from a coal stove to make a bit of electricity.

This wouldn't actually "use" the heat, as long as it's generated using a temperature differential, and the power is used in the house. This is because, even if the generation method has very low efficiency, the heat is still used, and pretty much all electricity ends back up as heat.

There are 3 methods I can think of for making electricity:

1. Stirling engine generator. Yes, there is no "e" in Stirling. It is an engine that runs on a temperature differential. There is a commercially-available unit for woodstoves which directly drives a small fan to blow the air in the room around. There is another company which makes a larger cogeneration unit, which burns gas to generate both heat and electricity. The stirling engine in this is capable of producing 750 watts, which is not insignificant. This would be rather expensive, but would pay for itself about as quickly as a stove.

https://en.wikipedia.org/wiki/Stirling_engine

2. Thermocouples. The seebeck effect allows you to directly generate electricity from a temperature differential. Again, there is a small fan available for woodstoves that blows air around the room. There is also a commercial unit available that will run a circulation pump.

https://en.wikipedia.org/wiki/Thermoelectric_effect

3. Steam generation. This is probly the worst option, since it is quite complicated and would need more maintenance. This might be the easiest option for the do-it-yourselfer. It would just require a pressurized boiler and a small steam engine/generator. The steam could then be used in radiators.

Ideally, the method selected would produce enough power to run a stoker. This seems quite easy if you only have to run the pusher motor, since it goes so slowly, a very low-power system could be used.

To run blowers would require much more power, and if even more is available, it could be used for other purposes, such as lighting.

Has anyone though about or tried to produce power from the heat of your stove?

Not at all practical for a coal stove. Take a look a the post by "barley master" 250 HP boiler, firing rate = two tons per hour! Scale your stoves firing rate and see what HP you might have. Not much. Think of it like this... Put a tea kettle on your stove. What size steam engine do you think you could run?

Yanche

Ok,

250HP = 186.5KW

If it were all converted into electricity, that's enough for about 62 national average homes.

However, as I said, the idea isn't to run your whole house from the coal stove, just to make a small amount of supplemental electricity. Even a few tens of watts would be nice, and should be enough to run a stoker with efficient motors.

http://www.hi-z.com/

If you get the 20 watt thermocouple, it should easily be able to run an efficient 1-RPM DC motor in a stoker. Then you never have to worry about power failures.

Has anyone come up with a stoker that doesn't need electricity? (maybe you'd consider the hopper stoves to accomplish this).

I have a friend with one of the stirling motor fans on his cook-stove. It does move a little air, but it is really a weak motor. The fan blades aren't even in a guard, 'cause they can't inflict an injury.

I had thought that they would be pretty common but once I priced one, I saw why they aren't!!

It would be neat to be able to power either a stoker motor, or a circulating pump off of a thermocouple. Any idea how expensive a system would be to create about 1 amp of current?? My circulator pulls about .8 amps.

And how hot would you have to keep the stove? Would the thermocouple have to be in the firebox for it to be effective??

Neat idea, wonder if it could work.... Even a 'night light' burning off of the heat from the stove would be neat, as long as the cost wasn't too high.

Greg L

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I've always wanted to build a steam-powered generator for the house.

That was, until I researched the costs involved! I have no access to lathes or the metals required. Nor have I ever welded anything that needs to withstand several hundred PSI along with several hundred degrees -- probably not wise.....

Would be great to shut off the breaker & have coal supplying heat AND electricity!!

I'd probably be able to afford my property taxes for '07!

I have a 3 bladed EcoFan similar to this one http://www.ecofan.com/.
It generates electricity to power the fan from the heat of the stove. Mine is rated at 150 cfm but I think that is mostly marketing hype ,, maybe 50 cfm at best. It does move the heat some but not nearly as much as the 9" fan I put in the door way corner to move the heat to the end of my 85' ranch. I bought it at Walmart ,,, http://www.epinions.com/Lakewood_High_Velocity_Fan_9_Inch

LsFarm,

For one thing, I'm guessing you mean about 1 amp at 120V. It would probably be easier to replace that with a 12V DC motor, which could be much more efficient.

Here's a unit designed to power a circulator pump:

**Broken Link(s) Removed**

endinmaine,

Looking at the picture of that fan, it looks like it was designed by a moron. There's a big long upright section that has to conduct the heat from the base all the way to the fan, and is also right in the airflow. Most of the heat energy will be lost by the time it gets to the top. The thermocouple should be right at the bottom, almost against the stove, and it could also use a better heatsink at the top.

If designed well, I think that fan would work quite nicely.

Moose, do you have any idea what the thermocouple powered circulator pump costs?? And the capacity of the pump compared to say a TACO 007 or 011 pump??

Yes I did mean 1 amp at 120vac. If it was a DC 12v motor wouldn't you need 10amps to get the same power [watts?]

interesting idea.

Greg L

Greg,

It probably costs more than you'd get back in power savings. However, it might be useful if you're in an area with long or frequent power failures, ice storms and similar weather, or if you're concerned about long-term infrastructure disturbances (such as the power grid going down).

I'm not familiar with the pumps you're asking about.

Yes, you'd need 10 amps to get the same power. However, if you used a high-efficiency DC motor, you would need less. The unit on that site produces 20 watts, which would probly be enough for most circulator situations. You'd be better putting money into a more efficient pump and larger pipes than more thermocouples.

If you used the thermocouples on the Hi-Z site, you could get 120 watts for about $1000, which is somewhat comparable to solar panels.

Thanks Moose, I thought it would be prohibitively expensive. I can power the whole farm for about $70 per day with my standby generator, so it would take quite a power-outage to consume the cost of just one pump. And it wouldn't solve the problem of powering the rest of the farm anyway.

I can see your point though about using one where there is no power or frequent long term power outages.

Thanks for the info

Greg L

Check out E-Bay item 7613178206 for the way homeowners once made electricty using coal. I would love to own it!

Yanche

Now that would make a cool science project for keeping you busy over the winter!

I bet that thing sounds great when it gets up a full head of steam.

I was thinking about theoretically changing the Harman mag Stoker to all 12v and running a deep cycle battery off solar electric panels on the roof.

Or just use a $40 400w invertor from home depot, and use more solar electric panels to make up for the loss of efficiency.

Such a scheme would maybe be more fruitful than trying to create electricity off the stove. Although the stirling cycle engine is interesting (if overly complex and probably noisy)

Deep cycle batteries with solar power seems like the smartest way to go. Shouldn't take too much power for one decent sized panel. I've always wanted to play with solar. Could be a fun science project!