[Stoves] Purpose of testing and the lengua

Mon Feb 24 16:21:26 CST 2014

Frank,
 I am hardly one to talk when it comes to typos but your note caught me for its potential double entendre'. 
One would "cut to the chase' to indeed get to the point, unless one wanted to simply relax on such as a chaise lounge  and ponder the discussion by cutting to same. Which did you intend ?
Hasta Richard

On Feb 24, 2014, at 2:06 PM, Frank Shields wrote:

Dear Crispin,

I, as others have mentioned, appreciate all the calculations and info you provide. Wish my job was doing this full time so I could put in the time justified to the work you put into this and give to us.

I cut to the chaise….

When people’s livelihood depends on someone picking their stove for distribution over another their choice need be based on very accurate and justifiable reasons.  

At the moment we are using a comparative test to pretend the result is ‘certified’, meaning ‘absolute’ but in reality, the lab and the procedure and the number of replications, even the calibration protocols and lab training would not really allow one to claim with precision that the result was ‘certified’ correct. We have to do what we can with the equipment available, in the time we have and in a spirit of fairness.

If the results from this process go into a list of stove and then used to pick the one to be used – I think it not good enough, in fact meaningless, with all the added variables.

The bottom line is the products have to be much better on emissions, reasonably better on fuel consumption, and bought because people want to own and use them. In other words high adoption.

This line has three components: emissions, fuel consumption and adaption. We are just dealing with Fuel Consumption. Emissions and adaption is for a later discussion – but very connected.

One of the very confusing things that has permeated the stove testing community is the erroneous idea that the heat value in the fuel left over has a great deal of significance.

Only important if you go through all the work of determining it and then use it in the calculations.

Regarding Char:
Well, it might have all sorts of values, but it is not relevant to the amount of fuel needed to start and run the stove the next time.

I agree. But it is important for adaption considerations. So should be mentioned with each stove and nice if we can come up with best guess for the quality of the char and what it might be used for. Not for fuel consumption discussions.

Thanks

Frank

Frank Shields
Control Laboratories; Inc.
42 Hangar Way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at biocharlab.com
www.controllabs.com

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Crispin Pembert-Pigott
Sent: Monday, February 24, 2014 11:13 AM
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] Purpose of testing and value given to char left.

Dear Frank

You have captured this correctly:

>I think we are all in agreement with Crispin the final purpose is to save trees and to Ron it’s important to place a value on the char left over.

They are two different questions and they have two different answers. Both have value.

>You suggest we determine the wood used for each burn and after several burns we have the average wet wood used.

Actually we have a protocol for this and it is included in the Test Method.

>It will take many Runs (I suggest  ~ten statistically?)

We are using three.

>And then we go to the next house and how many more houses, all using the same stove (the variable), to come up with a statistical value.  

This is not actually necessary. There are ways of using focus group to make a determination that is accurate enough to make a comparative assessment. Remember something very important that changes the number of tests required (a lot):

We are seeking comparative fuel consumption, not absolute numbers. This can be shortened to a comparative test, not a certified result.

At the moment we are using a comparative test to pretend the result is ‘certified’, meaning ‘absolute’ but in reality, the lab and the procedure and the number of replications, even the calibration protocols and lab training would not really allow one to claim with precision that the result was ‘certified’ correct. We have to do what we can with the equipment available, in the time we have and in a spirit of fairness.

It is easy when we are not trying to get a 5% or 10% improvement. As with the stove replacement programme in Mongolia, we only allow into the programme stoves that are at least 90% better than the baseline product. That is a huge difference so there is no quibbling as to whether the product is 15% or 12% better. It has to be 90% to 98% better to be interesting to us.

In the final analysis, the exact reduction a stove gives, say 21% v.s. 25% improvement, is not as important as being sure that lots of people adopt a better stove, and they are happy with it and use it most of the time. Being really sure it is 24% better and only used 30% of the time is not really what we want to see in the final analysis.

For this reason the social science surveys that were conducted were really good, detailed examination of what is cooked, and when, by whom and so on.

>Then we give all these same houses a different stove for testing. Is this your plan? 

Nope. That is not practical. The bottom line is the products have to be much better on emissions, reasonably better on fuel consumption, and bought because people want to own and use them. In other words high adoption. Turning that into numbers is always a nightmare and we do the best we can. In this case it is with a new protocol that is strongly informed by local patterns of use. That should give us more predictable results in the field. Because the social science (social impact potential) has been assessed beforehand, we can make a pretty good estimate of whether or not a stove will be acceptable. One metric is cooking power, another is controllability. A third is lighting speed. Another is cost and durability.

>A lab test using fuel Energy as a proxy reduces the variables such that a lot of tests can be done in a short time at a reasonable cost. Like was done before. The biggest variable is the left over energy after the WBT ended and this can be accurately done using a calorimeter on a dried and ground sample –as done at Aprovecho OR my past suggested E450c method.

One of the very confusing things that has permeated the stove testing community is the erroneous idea that the heat value in the fuel left over has a great deal of significance. It has significance if you want to know the heat transfer efficiency. It does not have a lot of significance if the fuel is not useful in the next fire. For example, you might accurately determine the heat value of tiny chips of charcoal in the ash. And what would you do with het number? It would not tell you anything about how much fuel it uses because that ‘fuel’ is a ‘mechanical loss’ (meaning energy lost without burning it).

Fuel consumption is not determined by measuring the energy content of fuel left over. It is measured by determine the amount of fuel needed each time the burn cycle is completed. That is all. It is really a lot simpler than people have made out.

>As for the value to be placed on the char left over: The quality of this char ranges from toxic to plants –to- sucking up nitrogen –to- adding heavy metals –to- producing a large plant and doubling production. To place a value one needs to collect a quantity and determine its value –if any for a purpose.

Well, it might have all sorts of values, but it is not relevant to the amount of fuel needed to start and run the stove the next time. Because the question we have been asked is ‘How much fuel does this stove use, on average, in that community?” we should answer it to the best of our ability.

>…For marketing we may be able to state that stove such-and-such consistently puts out a char of quality to improve soils, sequester carbon or can be used for char cookers -after collecting a composite of the char from a stove and testing it.  

That is all interesting information, supplying answers to different questions, not the one that is most frequently asked.

Regards
Crispin

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