[Gasification] Underwater gasification?

[GF]

In the 1890's a patent was issued for an invention for the propulsion of a vessel using the explosion of gas above a column of watet which was forced out of the vessel
in the opposite direction to the desired direction of navigation. The process could be reversed for slowing down purposes. This invention preceeded Humphrie's pump by about thirty years. A jet propelled vessel using heated biomass as fuel with only a couple of moving components sound  worthy of investigation.
I do remember sailing toy boats with a coil of tube as the "engine" with a candle providing enough heat to boil the water within the coil causing a pulse jet out back.

GF




-----Original Message-----
From: Daniel Chisholm <dmc at danielchisholm.com>
To: Discussion of biomass pyrolysis and gasification <gasification at lists.bioenergylists.org>
Sent: Wed, May 18, 2011 9:14 pm
Subject: Re: [Gasification] Underwater gasification?


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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