[Stoves] Good enough stove?

Sat Nov 21 22:38:03 CST 2015

Dear Frank

You ask a very important question: it is about the 'thermal efficiency'.

Do you think that the thermal efficiency refers to the fuel consumption? Because you are in a sense outside the system, ‎your opinion matters. If you are under the impression that the thermal efficiency tells us something about a stove, what is it exactly?

Because 'thermal efficiency' can mean half a dozen things at least, the perception of its meaning is important. Hence my interest.

"And we (you people) choose the stove for them and purchase in bulk. Am I right?"

No. I have never been involved in the bulk purchase of stoves. It is always some sort of assisted purchased with the models open to the vendors to try to sell. The supported models are tested first to see if they meet the program goals and customer preferences. People but what they want. In a refugee camp situation I believe the UNHCR‎, for example, does buy stoves in bulk and hand them out to camp occupants. That is a small % of stoves sold. There are models of stove that are only available through such programs, meaning they are not on the open market.

Sometimes the preferences for the purchaser align with the promoting agency, sometimes not. In Ulaanbaatar the customers wanted fuel savings (kg per day) and the project wanted PM2.5 reduction. Both were provided in the approved models.

The confusing thing is when the fuel saving is overstated because people report some proxy for the heat transfer efficiency instead of the energy consumption (represented by kg consumed).

It is a surprise to me that this has been so difficult to resolve. If it uses more fuel per day, then reporting that it 'uses less energy' is misleading. Right?

Regards
Crispin

Dear Crispin,

People buy cars not due to gas millage. They buy pick up trucks to haul dirt, old cars to save money, new cars so neighbors think they are rich, vans so they can crawl in the back to sleep and save on motels on road trips. Then there is the most important - the color.

The mistake the ’stove community’ makes is that they think they know why someone purchases a stove and they then tell them what stove they should buy. All we need to do is state what the stove is expected to do and the products left behind (ash, char) and let them pick. Of course producing the most clean burning stove and high thermal efficiency for a task should be our goal - but that does not necessarily compute to the one someone should purchase.

OK - I am not in the ‘field’ working like most of others. And stoves are being sold to many different clients. And the one we are all mostly targeting are the poorest of the poor. The ones really suffering. And we (you people) choose the stove for them and purchase in bulk. Am I right?

So it is important to have a selection (and qualities listed) to pick from *designed to use the fuel available* and *complete the task needed*.

> If the energy released in the chamber is important, you should argue why, and to whom, and what, if anything, it offers a customer while being free to describe various consumers of the information.

Everyone on this list working in the field knows more than I BUT from my learning it seems the poorest of the poor has a short supply of fuel, that it is being depleted and dangerous to obtain. Based on that we need very efficient stoves. And regardless of that we should be trying to produce them anyway - good science. And clean burning and less fuel for a task = clean air and better health.

And we are only talking cooking stoves - not room heating stoves or giving light. The others are for a different ’task’.

> One of the most interesting things about the stove designing community is a historical obsession with the heat transfer efficiency.

One of the most interesting things about the stove community to me is that they can’t design a test method for testing stoves with variables controlled and targeted for a specific fuel and location. All the heat transfer efficiency values that I know of has been done without control of the variables (Box 1) and fuel not representing a specific site - except for the studies done on site that are very costly and offer very little in the way of stove choices.

 Regards

Frank
Frank Shields

> On Nov 21, 2015, at 7:30 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
>
> Dear Frank
>
> "The importance of ‘outside’ the stove is left to the end user and is used to pick one stove over another."
>
> Well, that is why people buy cars based on their fuel consumption. ‎The compression ratio and the combustion efficiency is not useful information for the customer, only the design engineers.
>
> One of the most interesting things about the stove designing community is a historical obsession with the heat transfer efficiency. It was never a good guide to fuel consumption and with the advent of char makers, has become positively toxic to the stove selection process. People think they are being told the fuel consumption when they see "efficiency" numbers.
>
> If the energy released in the chamber is important, you should argue why, and to whom, and what, if anything, it offers a customer while being free to describe various consumers of the information.
>
> How would you approach that challenge?
>
> Regards
> Crispin
>
> Dear Crispin, Paul and Stovers,
>
> <snip>
>
>> 2.  Crispin asks:
>>> Which would you finance: a reduction in the energy drawn from the forest? Or a reduction in the energy released from the fuel consumed?
>> There is no single correct response.  Both should be calculated and reported.   And the circumstances need to be understood.
>>
>
>
> The Correct Response Is! …..    : )
>
>
> <snip>
> OR
>
> 1) (Crispin added) a reduction in the energy drawn from the forest?
> 2) the time it takes to gather fuel
> 3) the ability of the forest to regenerate
> 4) the type of fuel that is used (vegetative matter, dead twigs, wood)
> 5) business possibilities gathering wood
> 6) char (or not) being made
> 7) reduction of degrees of hazard gathering biomass
> 8) the number of wheelbarrow loads of wood being moved
> 9) etc. etc.
>
> All equal as a measure as the ‘reduction of energy drawn from the forest’. The importance of looking at it from outside the stove depends on the site specific situation. So for our purpose of testing stoves it is only important to look at it from inside the combustion chamber - “reduction of energy released from fuel consumption”. The importance of ‘outside’ the stove is left to the end user and is used to pick one stove over another.
>
> Therefore we only need to calculate the Energy Used in the Combustion Chamber in a 1) repeatable 2) accurate 3) with precision 4) and common producible results from all (certified) labs doing the tests. The ‘outside’ results can then be determined on a site specific and importance for the potential purchaser.
>
> So we start with Box 1 and get control of the fuel. Place limits on the fuel for a specific combustion chamber. Market the stove to locations having that fuel with those limits available.
>
> and we can start doing this any old time
>
> Regards
>
>
> Frank
>
> Frank Shields
>
>
>
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