I finally laid hands on one of these, the BioLite thermoelectric power generation stove and have had some fun trying it out. I've covered these before, in a WishLust post, so I was really happy when a good deal came my way.
The general principle is this: a steel pot, an inner layer with air-holes, a protective outer mesh to prevent accidental contact with the hot pot, built in folding legs, and an attachable, thermocouple driven, high-capacity battery, with both USB output and an internal fan to drive the fire.
The fire output is measured as 3.4 kW (at low power with the fan) and 5.5 kW (With the fan at high power). I haven't yet timed it, but BioLite state that it takes as little as 4.5 minutes to boil 1 liter of water, but obviously boiling times vary by strength of fire, which then comes back to the quality of the fuel used.
Officially, 46g (1.6 oz) of wood to boil 1 liter of water, when I used it, I simply chopped up a fistful of wood, and fed it in, feeding as it went. One thing to note is that with a small combustion pot, you need to feed it regularly, as it burns down rapidly, more so if the fan is set to high.
The varnished pine ex-furniture I was using here went up like a candle, but I expect that denser, or damper wood to burn a bit lower and slower. Charcoal would be an ideal fuel, but anything form hay (which I used to light it) to paper and cardboard, twigs, pinecones, whatever, would do. If you have the fire going, and can fit the solid fuel into the firepot, it will probably work.
The output of the USB varied, with the intensity of the fire, but is documented as 2W @5V at a continuous burn, and a peak output of 4W @5V. This in turn gives a phone such as the iPhone 4S (2G) 20 minutes of charging provides 60 minutes of talk time.
As with the boil times, charging times would vary by device and by the strength of the fire.
I really like how by clever design the fan/charging pod, fits neatly into the fire pot, with the thermocouple poking out.
When packed, its 21cm (8.25") tall, and 13cm (5") around, and weighs only 930g (33 oz).
The triangular trivet which clips over the scalloped triangular metal lip provides extra security for placing pots or cups on the top, for cooking, water sterilizing, or what-have-you, doesn't clip nicely back onto the lip when the charging pod is stored, but the whole package comes with a nylon drawstring bag, so you're covered.
The USB port is nicely fitted, and covered by a silicone flap which keeps it drip, splatter and ash-free when not in use. The external honeycomb grill shields you from direct burns, but still heats up pretty swiftly, so don't try picking it up once burning.
I look forwards to coupling this with my newly-replaced PowerPot XL and doubling the off-grid charging and powering that I can offer my camp-site.
If the little BioLite looks a bit small for your needs, they also make these jumbo versions too, the BaseCamp.