[Stoves] kgharris stove test

[Crispin Pemberton-Pigott]

Dear Kirk and Paul

 

There were three numbers provided for power, the low the high and the test-high.

 

It was mentioned that there was a scale under the stove (which is a very good idea) and that readings were taken per 5 minutes (which is a pretty long interval).

 

Was the high power a maximum during the test phase, or the average over the phase? If it was the average then it should be presented like that because the phase includes an ignition. If it is the maximum firepower, that would not be the average including ignition.

 

If I say an electric stove has a 5 kW element, that is the maximum input power.  The cooking power is the input power times the heat transfer efficiency.  That is pretty straightforward.

 

So I wondered if the scale readings were used to determine the maximum power by using the burn rate, or if the power was determined in some other way. If it was scale-based, it means it is the average of the 5 minute intervals. If it was based on the scale, what energy content was applied? Was it the WBT sheet LHV (compensated for moisture? Was it the As Received, Ash-Free heating value? Was that value char-remaining-compensated to correct for the energy not released? 

 

The determination of the firepower of a stove is not nearly as easy as getting the cooking power, which in any case is what people experience when they use it.

 

At the moment I do not have a clear picture of what that 6 kW refers to, and as mentioned already, we don’t know the cooking power (delivered energy). Planning to introduce a design to a certain area will require taking a pretty good guess that the product is in the right cooking power range.

 

Because we don’t’ have the test spreadsheet with all the input numbers it is hard to know these answers, hence all the questions.

 

Dr Nurhuda provided a photo of a pot as proof that the PM is low for his latest stove. That is not a ‘test result’ in the numerical sense, but we can assume it must be pretty good.

 

Kirk provided some numbers from a WBT conducted at Aprovecho, which have emissions per MJ and per unit time etc. But we don’t have the numbers for the total MJ or the total time so we can’t tell a whole bunch of things we need to know to evaluate the performance or suitability. 

 

The best we could do is to share the official test spreadsheet so the missing metrics are available to those who need them. I cannot select a stove design based on an emissions per MJ if I don’t know how many MJ it is capable of delivering. I can rate a stove I have already selected using that metric.

 

I can’t select a stove design based on a heat transfer efficiency if I don’t know how much heat was involved. Similarly, the firepower combined with other metrics could be used to determine cooking capabilities but only if I am quite sure what that firepower number refers to: peak, average, smoothed 3-minute peak, and so on. 

 

What do we want to know?
Cooking power total.

Cooking power per sq cm.

System efficiency for some known and relevant task, expressed as the “Energy Efficiency”

Fuel flexibility.

Cost.

Durability.

Pot holding capacity.

Pot stability (when stirring).

Tilt stability.

PM mass per delivered MJ (used together with the cooking power)

CO mass per delivered MJ (ditto)

 

Note: the Energy efficiency is used as a proxy for relative fuel consumption to compare stoves. Very importantly, it must not refer to the heat transfer efficiency or any proxy of it. That is an internal relationship, and we want the black box version of the fuel consumption.

 

Most of these numbers can be calculated from the information recorded in a WBT spreadsheet.

 

Regards

Crispin

 

 

Paul,

 

Kirk and Crispin,

I BELIEVE I understand Crispin's question of "How is the 6 kW power measured?"

I think the answer is that it is based on the amount of energy released in the measured time to bring the water to boil (that being the high power time-period, but the calculation has nothing to do with the increase in water temperature. And that the energy measurement is based on the energy of the weighed fuel (adjusted for moisture content), and giving "credit" for the energy that is in the remaining charcoal.
Does that make sense? 

Yes

Kirk and Aprovecho testing personnel: Is that correct?

I’m not sure what you mean here.  At Aprovecho it is correct.  At Berkley it was the Berkley lab Engineer, experienced tech and students.  It has been a good and fun experience working with very bright people at both Aprovecho and Berkley.

Crispin: Were you expecting some other answer? What other way might be used?

The Kirk Harris Wonderwerk TLUD stove with Strata combustor will certainly be a featured item at the 5-day Stove Camp on 15 - 19 August at Aprovecho. Even if you cannot attend, you can give inputs and questions to Kirk (and to other attendees) via this Stoves Listserv.

Yes

Comment: Kirk points out that this is a research device. And that actual manufacturing with his advances is something that needs additional discussion and work. THIS issue of how to put it into production will be an important topic at Stove Camp and here on the Listserv.

Yes, thank you

Kirk H.

Paul

 

 

 

----- Original Message ----- 

From: Paul Anderson <mailto:psanders at ilstu.edu>  

To: Discussion of biomass cooking stoves <mailto:stoves at lists.bioenergylists.org>  

Sent: Wednesday, June 08, 2016 6:34 AM

Subject: Re: [Stoves] kgharris stove test

 

Kirk and Crispin,

I BELIEVE I understand Crispin's question of "How is the 6 kW power measured?"

I think the answer is that it is based on the amount of energy released in the measured time to bring the water to boil (that being the high power time-period, but the calculation has nothing to do with the increase in water temperature.   And that the energy measurement is based on the energy of the weighed fuel (adjusted for moisture content), and giving "credit" for the energy that is in the remaining charcoal.

Does that make sense?   

Kirk and Aprovecho testing personnel:  Is that correct?

Crispin:  Were you expecting some other answer?   What other way might be used?

The Kirk Harris Wonderwerk TLUD stove with Strata combustor will certainly be a featured item at the 5-day Stove Camp on 15 - 19 August at Aprovecho.  Even if you cannot attend, you can give inputs and questions to Kirk (and to other attendees) via this Stoves Listserv.

Comment:  Kirk points out that this is a research device.   And that actual manufacturing with his advances is something that needs additional discussion and work.   THIS issue of how to put it into production will be an important topic at Stove Camp and here on the Listserv.

Paul



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