[Gasification] Underwater gasification?

[sam at bristolwireless.net]

Hi all

I wish to move a 22ft 1 tonne boat using wood power.

I have already considered gasification + combustion, gasification +  
stirling engines, even steam power!

My latest thought experiment is gasification + thermo-electric generators.

looking at the products of tegpower.com it seems like this may be  
viable, if somewhat expensive (£4k)

To move the boat at around three knots will take an estimated 40 -50  
amps http://www.floveroutboard.co.uk/outboards.html

Which will require approximately 50 of the TEGP15 thermo electric  
panels http://www.tegpower.com/products.html. I then need to keep one  
side of the panel at 20C (or lower) and the other at 260C. (but no  
higher than 325C)

Initially I considered doing this with an active water pump driven  
cooling system, which would be fine, however if the pump/wiring fails  
or gets blocked the considerable investment in TEG panels melts before  
your eyes.

So I figured given all the water around the boat it might be better to  
run a passive cooling system, and actively pump the air for the  
gasifier. That way if something breaks it just cools down and stops  
working.

Which leads me to the challenge of gasification underwater..

I have taken as a benchmark the mega fireplace gasifer  
http://www.woodgas-stove.com/how_to_use_woodgas_stoves.php which puts  
out 55,000 btu/hr which on paper is enough power.

So I am thinking about taking take a 14inch x 6ft diameter steel pipe  
with a sealed end and sticking a woodgas fireplace in it. Then feeding  
a air supply pipe down to the bottom, and using a fan to force the air  
in.

The TEG units will be attached to the inside of the pipe with some  
kind of heat conducting cement. The water temperature outside the pipe  
(typically 5C - 15C) will provide the passive cooling, and the heat  
rising up from the stove will heat the inner panel (maybe!)

I did a bad diagram here: http://i.imgur.com/SYpu2.jpg

I realise the engineering challenges of this are not trivial..

* Are forced updraft gasifiers harder to make/ less efficient on this scale?

* What would be a good guesstimate for the temperature at the bottom  
TEG? The top TEG? Above 325C?

The next step is to buy a the pipe and woodgas fireplace and do some  
real world tests. Is it worth me taking that next step? Do you see  
insurmountable problems?

Thanks

Sam