Electricity Generation with Wood Heat

[matt walker]

I thought I'd start a new thread to follow up on my experiments with making electricity from my rocket mass heater. So far, I've easily been able to build my own little "ecofan" type fan units for the top of the barrel. This is probably the best use I've found so far for these cheap Peltier elements I'm using as the power source. I've also been successful building a "joule thief" circuit to power a group of LED lights with the same element. This is a bit more complicated than the fan, but works very well and was pretty straight forward. I'm only generating about .5v from one element, so it's pretty limited what you can do, but it's pretty cool to play with and so far has been cheap. Due to the low voltage, it's necessary to build the step up DC to DC converter to power even one LED, thus the "joule thief."

I would say that for sure the fan is worth while, since it performs a very useful function of moving the warm air off the barrel into the room, and helps break up stratification in the room. So far, the lighting is more novelty than very useful, but I am going to play with that a bit more tonight and see what's possible. I'll post more once I finalize some experiments and can give some better advice, but for now, here's a couple links:

Joule Thief circuit: You need this to run LEDs with one Peltier element.
http://www.evilmadscientist.com/2007/we ... ule-thief/
http://www.instructables.com/id/Make-a-Joule-Thief/

Homemade Eco Fan video: Not mine, obviously, but pretty much exactly what I did. Same heat sinks, even. This is a pretty awesome little project, since a store bought one is around $100 and up.
http://www.youtube.com/watch?v=g3fHGIPFqpY

Peltier element:
http://www.amazon.com/Tec1-12706-Thermo ... ds=peltier

[DevilsBrew]

Is there any way to store the electricity so that you can use it for larger items at another time?

Does the fan or the lights draw energy away from the stove? Is it too little to make a difference?

[matt walker]

It's such a small amount of energy, it wouldn't be worth storing in my opinion. As for robbing heat, it just seems to pass most of it right on through, so no noticable loss there. The fans are definitely useful though, certainly worth the small price of admission. My housesitter bought a nice Ecofan while I was on the road, and left it here for me. They do make a significant difference in the even distribution of the heat in the room. I'm very pleased to have discovered for myself an easy, inexpensive way to build one.

[matt walker]

I played with this a bit more last night, I'm actually getting some very useable light out of this thing at this point. It's pretty great as a fire monitor, actually. When the lights go out, it's time to add more wood. I'm going to keep working on this, perhaps I'll make a video here in a couple days when I get it refined a bit. If I don't get distracted trying to build a cookstove now that Adam has my head whirling around thinking about that problem.

[DevilsBrew]

First a light, then a phone, then an ipod, etc...this technology could be rather useful, especially in a power outage.

I am not a fan of the sign up stuff for free so I am guessing they encased a full rocket in brick work. I am also guessing they have a valve system for the stove top. That would be an easy build for you, Matt. All that brick masonry isn't even necessary except for aesthetic purposes.

[matt walker]

Took me a minute to figure out what you were talking about in that second paragraph. I've seen the build pics of that one, it's pretty straight forward. Certainly could build anything along those lines, but not for free. Lots of cash tied up in that build. Not that there's anything wrong with that, just out of reach for me. No, I'm thinking of something entirely new, or at least, a new approach. I have an idea.

[mannytheseacow]

I've been scratching my head- I don't know what that second paragraph is about?

[DevilsBrew]

[mannytheseacow]

Oh! Roighty roight then! I get it. It doesn't help that I'm a bit slow.... Nor does the homebrew...

[matt walker]

Erm, beg to differ on the last point there, my friend. Homebrew ALWAYS helps.