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Comment by ctdonath | Hacker News Reader

Variant idea: a small portable version for camping. Stick one end in a fire, USB plug for power connector at the other. 2.5W shouldn't be hard to get under conditions where "unreliable" is normal.

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It will be kind of heavy though. For simple charging of appliances, other projects are very interesting:

http://www.kickstarter.com/projects/ryochijiiwa/bootstrapsol...

http://www.kickstarter.com/projects/davefoster/lilypad-using...

I have a solar charger/battery. Surprising how often you can't get enough sun to matter, as you need many hours of continuous direct bright light to collect anywhere close to enough.

I'm imagining a sort of pencil-sized Sterling; stick one end in the fire and the other in a cup of cold water. Not reliant on ambient/weather conditions for power.

aah, that's very interesting.. though I'm skeptical a pencil sized one will be able to output that much of power :). The problem with Stirling engines is that power output is kind of low when compared with a similar sized IC engine.

I've got a miniature Stirling on my shelf. It's a two cylinder setup that runs off of two small alcohol lamps (about the equivalent of two candles), and is air cooled. It weighs about a pound (but could probably be lighter). I don't know exactly how much power it puts out, but it's not much - you can stop the flywheel with light finger pressure.

More heat would produce more power, but I think pencil sized may be a bit optimistic. I like the idea though.

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