Engineers please read-practical problem inside

[trains are bad]

I have a woodburning 'boiler' that keeps water at 180*f.

I need a way to generate elecricicy off that. I only need enough power to turn an automotive alternator or some other even smaller generator. It only needs to keep a car battery charged. So i need maybe 2 amps DC contiuous.

Since it's not steam, I cannot use a steam engine. I've heard of something called a sterling engine that would run off hot water.

[aut911]

ever heard of a candle turbine?

Little peice of sheet metal shaped like a propeller. the heat from the candles underneath makes the turbine spin because of the whole heat rising thing. Im not in any way shape or form an engineer but I hope that helps. Just so long as the heat coming from the boiler is enought to turn the turbine, a simple pulley system could be arranged to turn your alternator. And since cold water is more dense than hot, you could in theory make a water turbine by taking some of the hot water and running it through a long copper tube. the tube would be connected to a water pump of some sort ( like one from a boat or even a drill powered one) and then either into a sink or drain. The only problem with that is that you would be constantly filling your boiler. By the way, a stirling engine would work. Its simply a pneumatic ram hooked up similary like a steam powered train, with a counter wieght to keep it moving in the right direction. Well anyways, at the apex of the cycle of the ram, the main seal comes in contact with an exaust port(hole) and the counter weight wheel returns it to its original position.

aut

[Lurker27]

You could always make it a steam tubine by pumping out some pressure...jsut belt rive from your steam turbine, turn the system on via manually cranking and let it self sustain.

[vf-xx]

Getting ready to head out to work this morning. When i get back I'll whup out the thermo book and look up a sterling engine for you.

[fastev]

Why not skip right over the "boiler" and use the exhaust heat and gases from the wood burning stove? I'm not sure how you would rig up a turbine, but you'd have a constant supply of moving air to spin it with.
Now that I think about it, you can get an old turbo charger from an automotive scrapyard pretty inexpensively. I bought one a few years ago that came off a Caterpillar diesel for $40. It was only the compressor side, (if you aren't familiar with turbos just ask, I'll explain) but the sompressor veins are in a sealed "tube" and the inlet and outlet were about 4 inches-- probably about what your chimney pipe is. A pully on the turbine shaft would spin an alternator...

[trains are bad]

There is no exhaust.

What I need is a stirling engine, but I cannot find any practical, commercially available models.

[SeeK]

I have a woodburning 'boiler' that keeps water at 180*f.

I need a way to generate elecricicy off that. I only need enough power to turn an automotive alternator or some other even smaller generator. It only needs to keep a car battery charged. So i need maybe 2 amps DC contiuous.

Since it's not steam, I cannot use a steam engine. I've heard of something called a sterling engine that would run off hot water.

Lead acid batteries usually keep their charge pretty well. If you need 2A DC continuous then you need to check out your electrical system. You could throw a meter between the battery and terminals to see your actual draw.

There are solar panels to keep batteries topped off:

http://www.batterystuff.com/battery/solar_chargers.htm

This would most likely be cheaper than trying to build something. The other alternative is a new battery in the 1000-1200 CCA range and it would last a few years.

[syko2102]

I'm not really an engineer, but I wanna say i remember something from auto shop that said alternators made A/C current hence the name alternator, and that the generator, or what they used to put in cars was the means of making D/C current. If someone knows more about this please correct me and inform all of us.

[SeeK]

I'm not really an engineer, but I wanna say i remember something from auto shop that said alternators made A/C current hence the name alternator, and that the generator, or what they used to put in cars was the means of making D/C current. If someone knows more about this please correct me and inform all of us.

I believe all generators create AC (alternating current) due to the magnetic flux generated by moving a magnet perpendicular to a wire (sounds similar to the HES discussions?).

A bridge rectifier is used to take only the positive or negative part of the output to create DC (Direct current). It would look like this on an oscilliscope: ^v^v^v^v into ^-^-^-^-^
A capacitor is used to fill in the gaps and even out the voltage: -------------

As you can see 1/2 of the energy is wasted so there are full wave bridge rectifiers to pipe the lower part into the upper part. A capacitor is still used to fill in but it doesn't have to fill in as much.

[Fixion]

There is no exhaust.

What I need is a stirling engine, but I cannot find any practical, commercially available models.

I don't know if a sterling engine would be effective at that temperature. They are usually heated by fire. But who knows.

I don't know where to get them, but I know there are commercial sterling engines. Before you consider getting one, make sure it would be hot enough to run it.