[Stoves] 2 KW Woodgas generator with turbine

[Thomas Reed]

Dear Andrew:

Right on!  Visions are great, but can be red herrings...

TOM REED     BEF



CEDESOL Foundation wrote:
> On 3/18/07, andrew <list at sylva.icuklive.co.uk> wrote:
>   
>> On Sunday 18 March 2007 10:24, Crispin Pemberton-Pigott wrote:
>>
>>     
>>> This guy speaks as if it is normal to generate 2 KW worth of
>>> electricity from wood gas using his burner.
>>>       
>> Firstly this topic is better at [gasification] rather than [stoves],
>> complication, safety and capital expense means the waste heat is
>> never likely to be a prime use of the technology, least of all for
>> cooking.
>>
>> He may generate 2kW(e) but what is the cost in input kW(t)? My guess
>> is around the 5% mark, probably no better than a modern TEG. I say
>> this because we built a pyrolyser with a bit more sophistication
>> than this. it ran at 2bar above atmospheric. Now think about this
>> the next time you pump up a car tyre, it's a non insignificant
>> pressure. So the containment has to be internally insulated and
>> pressurised, the "skin" has to withstand this and to do so must leak
>> a bit of heat.
>>
>> Why do I compare it with a pyrolyser? It's because there are
>> difficulties with complete gasification such that for this use it is
>> actually quite a bit easier just to deal with pyrolysis offgas and
>> discard the char. I think even fairly successful gasifiers running
>> reciprocating ic engines have tended to leave a lot of char with the
>> ash.
>>
>> Terra Preta enthusiasts will see an opportunity similar to that
>> presented by a TLUD stove once carbon trading/offsets work at the
>> micro level.
>>
>> There are a number of means of pushing up the conversion from these
>> low pressure "agricultural" gas turbines but they involve
>> significant cost. An increase from 11% to 20% was mooted for a 250kW
>> output with a pressure ratio of 2.9:1.
>>
>>     
>>> There is quite a lot to see (including a 120,000 RPM turbine) at
>>>       
>> Maybe but how safe is a turbine with an inlet temperature of ~1000C
>> running continuously, when it was designed to operate at an inlet
>> temperature of 500C for a vehicle life of a few thousand running
>> hours?
>>     
>>> My simplest interpretation of it is that he is using a vehicle
>>> turbocharger to compress the gasifier...yes?
>>>       
>> Most likely the compressor provides compressed air for both the
>> combustion and the gasification, the containment all running under
>> pressure.
>>
>>     
>>> Or is it burning the
>>> gas to drive the turbine and get electric power from the shaft?
>>>       
>> He'll be burning the gas in a separate combustion region and then
>> expanding the products through the turbine, even with wood the thing
>> will need quite a lot of dilution air to get the turbine inlet
>> temperature low enough (you might be able to do this with the water
>> from green wood but it would likely interfere with the gasification
>> part too badly).
>>
>>     
>>> Either way there is a lot of heat to cook with left over.
>>>       
>> Definitelyy probably about 600C, but the food would fly and the cook
>> would go deaf.
>>
>> Should anyone in UK want to further the concept I may know a man that
>> could find the bits still, unless they're already en route to a
>> smelter in China.
>>
>> Andrew Heggi
>>
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>>     
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