[Gasification] Underwater gasification?

Daniel Chisholm dmc at danielchisholm.com
Wed May 18 20:13:05 CDT 2011


Sam conceptually speaking you would be using the thermoelectric generators
as a "transmission" of sorts - you are connecting hot flue gas on one side,
which the T.E.G. turns it into electrically generated shaft power on the
other side.  So the question becomes whether this is the best way for you to
convert heat from wood into shaft power for your propeller.

My initial thoughts are that this is probably not an effective way to get
this done.  One issue is that thermoelectric generators are very
inefficient, on the order of 1% or 2% (this means that you need to feed them
50hp or 100hp of thermal energy in order to produce 1hp of electrical
power).  Or, the 55,000 btu/hr heat source you quote might be expected to
produce 550-1100btu/hr of electrical power (which at 3412btu/hr per kilowatt
would be 0.16-0.32kW or about 1/6hp to 1/3hp).  In comparison an old
fashioned low pressure simple steam engine will probably give you 5% to 8%
efficiency (so several times more economical of wood than an T.E.G.) and a
small gasoline engine would be on the order of 20% (so wood would have to be
10X or even 20X cheaper than gasoline, which is quite unlikely

Another big factor is cost per unit of power, the panel you link to is $320
for a 30 watt panel, so we are talking about $10,000 per kilowatt (contrast
this to say a 100kW automotive engine that costs say $5000, or a how much a
10hp (7.5kW) outboard motor might cost).

Thermoelectric generators have a number of virtues, for example no moving
parts, maintenance free and very long life, quiet operation, etc., which
make them excellent choices for some unusual special applications.  But I
expect they are unlikely to be a good match for a principal power source
like boat propulsion.

-- 
- Daniel
Fredericton, NB  Canada
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