[Stoves] FW: REQUEST for complete sets of raw data of cookstove tests.

[Paul Olivier]

Crispin,

If a stove is designed only to produce heat, then it makes sense to measure
efficiency in terms of the production of heat. But if a stove is designed
to produce syngas and biochar, we cannot measure efficiency only in terms
of the production of heat.

In my TLUD stove, both syngas and biochar are produced. The quantity of
each in a given batch cycle depends in part on the speed of the fan. If the
fan speed is high, resulting in a relatively high temperature of
gasification, more syngas and less biochar is produced. If the fan speed is
low, resulting in a relatively low temperature of gasification, less syngas
and more biochar is produced. This ratio of syngas to biochar is constantly
changing throughout the entire batch cycle. The operator trying to cook a
meal is not concerned about the ratio of syngas to biochar, but only about
the right temperature required to cook a particular dish.

In a stove that produces syngas and biochar, only syngas gets combusted. So
if we want to measure efficiency, we might look at how efficiently air is
applied to the syngas in achieving total combustion. What does not get
combusted (biochar) should be left out of the equation.

When syngas exits my TLUD, it contains a lot of heat (>500 C). To cool down
the syngas prior to combusting it would involve a huge loss of heat. One
might also argue that syngas burns more cleanly and more efficiently at
higher temperatures. That is why I am in favor of putting the burner right
on the top of the reactor. If more burners are needed in a kitchen setting,
more reactors, each with its own burner, are put in operation.

Here in Vietnam it is quite common the see pyrolyzers with one or more
remote burners. The syngas from these units is cooled down and routed
through PVC pipes to remote burners. Most of the heat contained in the gas
is lost, and the process temperature is so low that a lot of oils are
formed and condense out in this cooling process. Generally these oils are
used for nothing and have none of the value of either syngas or biochar.
Both the cooling down of the gas and the production of oils represent a
considerable inefficiency.

So how does one measure the efficiency of a stove? This is not an easy
question to answer.

Paul Olivier


On Thu, Apr 25, 2013 at 10:06 PM, Crispin Pemberton-Pigott <
crispinpigott at gmail.com> wrote:

> Dear Paul****
>
> ** **
>
> Here is the problem restated slightly better without prejudice re other
> biomass:****
>
> ** **
>
> If someone is interested in the char, it can be reported – it is in the
> raw data set. What Ron is proposing, to reduce the energy in the fuel
> consumed by the heat energy available in the remaining char, is akin to
> considering the fuel efficiency to be the energy efficiency which is
> precisely what created for us a problem in the first place. ****
>
> ** **
>
> The energy value of the char came from somewhere. Consider a stove that
> needs 2 tons of biomass per year to operate. If it produces ¼ of a ton of
> biomass energy equivalent in the form of char, fine. Say so. But saying so
> does not reduce the two tons of biomass it takes to feed the system. If you
> have (as you pointed out) a second stove that can utilise the charcoal,
> then that can be viewed as a ‘system’ by all and sundry, but is still does
> not change the fact that Stove 1 takes two tons of biomass each year which
> is what the reported fuel consumption should be. The impact of a system is
> not the same as the impact of a component of that system. The only debate
> left is how to report the fuel consumption and by-products.****
>
> ** **
>
> What has been happening that is wrong, in my view, is that stoves that
> actually take off 3 tons of biomass per year have been getting credit for
> taking only one ton and proclaimed to be ‘better’ and ‘more fuel efficient’
> than a two-ton stove. Plainly this is not the case and the test method has
> to report the fuel consumption correctly. It is a problem that the UNFCCC
> methodology (which measures energy efficiency) does not handle this well
> and it is being used for CDM trades. People are being cheated.****
>
> ** **
>
> Regards****
>
> Crispin****
>
> ** **
>
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-- 
Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
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