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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><b><span style='font-size:14.0pt;color:#1F497D'>Dear Crispin and Stovers, <o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:14.0pt;color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='font-size:14.0pt;color:#1F497D'><snip><o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:14.0pt;color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Paul >>With that distinction in mind, I then point out the Rocket stoves do NOT have a separately distinct reactor location. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Frank > We only need two numbers. The energy IN and a value related to task for calculating efficiency. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>The pot does not care about the way the fire consumes the fuel. It receives heat. If it receives it at an acceptable rate, the stove cooks acceptably. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>There is not yet agreement in this group as to what constitutes 'efficiency' in terms of fuel consumption. There is still talk about 'energy efficiency' which might refer to the energy released by burning some (not all) of the fuel and the work done, v.s. the energy that was potentially available in the fuel 'consumed' whether it was dropped, burned, charred, turned in to CO or anything else including heat.<o:p></o:p></span></p><p class=MsoPlainText><b><i><span lang=EN-CA style='color:#1F497D'>[Frank >] </span></i></b><span lang=EN-CA style='color:#1F497D'>A sticking point. We may end up deciding on a definition of efficiency because that the one we have a suitable method (at this time) and not the one we exactly want. Lets be flexible and cautious here or we will end up with a method that doesn’t work – again. My suggestion is to use E450c based on HHV DAF. Exclude moisture. We get the effects from moisture when we plot the as-received fuel as it is being used and I think that the best way to show what wet (or real) wood does. We calculate efficiency using the HHV values – but report the moisture content and weight loss from the stock pile in the 6 Box system. This so NGO reviewers picking out a stove for mass production can ‘read between the lines’ after comparing the efficiency values of different stoves. Dean, you and others know better than I but do we really know what the water in wood really does? Can we plot the results of a water boiling test against the same fuel but having increasing amounts of moisture and see changes? And get a straight line? If we can’t than I think all the calculations regarding dealing with water in the fuel is not a valid exercise. We should leave that to plotting biomass used. </span><span lang=EN-CA><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Frank > We lab people determine the energy we place in the Reactor and the value related to the finished task. What the reactor does with the energy to finish a Task determines a good working reactor or a wasteful one as determined via efficiency value. We lab people don't care what the reactor does with the unit of energy we place into the reactor. TLUD, Rocket, rice burning, dung burning, char burning - we don't care. That's only of interest of you stove designers. If you don't like the efficiency value we give you then you need to make some design changes. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>Well said! The test is technology independent, if it is a good one. If the metrics are correctly chosen, the results can make valid comparisons of performance, which as I said earlier are primarily defined by the policy managers or programme managers. That is usually total PMO, total CO and total fuel consumed per burn cycle.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Paul >>In Rocket stoves, the primary and secondary air are so intermixed (in such widely different proportions from one Rocket stove to another and even dependent upon using thick pieces of fuel verses many small pieces) that quantification is not likely to be trustworthy.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>Not to mention unnecessary and pointless for rating purposes. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Frank > …The efficiency value is a single number that is only related if things are done 'this way' and cannot be compared to tests done this 'other way'. I agree this is not the place for discussing the properties of combustion. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>If a test result cannot be compared with other test results obtained in the same project, they are not very useful. </span><span lang=EN-CA style='color:#1F497D'><o:p></o:p></span></p><p class=MsoPlainText><b><i><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'>[Frank >] Correct – and to make that comparison we need to either ‘control’ or ‘state’ the differences. <o:p></o:p></span></i></b></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>If the test method specifies, by trying to ‘control’ variables that really are variable, it needs better metrics that can take care of those variables while still reporting comparative performance. It is not true that nearly all variables have to be controlled. That is only necessary if you have not made a good choice about what to report. If you report the fuel consumption for an arbitrary task that is not relevant to the community of interest, the test has little value to anyone. If you choose a task that is relevant but which has metrics which do not reflect relevant parameters, again that is inviting disaster. Stove testers should not be afraid </span><b><i><span lang=EN-CA style='color:#1F497D'>[Frank >] If variables cannot be controlled than they need to be stated in the most organized and transparent means possible. I think that is my 6 Box system but that needs to be better organized and include a summery such that a reviewer can take a quick look, decide if a parameter is way out of line and then turn back to the page that describes that parameter in detail. When we can’t control the variables then that is the next best thing. As you say “not very useful” if the report is not organized for easy comparison. </span></i></b><span lang=EN-CA><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><b><i><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'> <o:p></o:p></span></i></b></p><p class=MsoPlainText><b><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'><o:p> </o:p></span></b></p><p class=MsoPlainText><span lang=EN-CA>Frank > Whatever happens, happens in the reactor. A given amount of E450c may do a single task like boil water or multi tasks like boil water, produce biochar, heat a room and give light. As to the number of tasks it does that only matters if it results in less trips to the corner pile of wood. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>It is for this reason that we have to deal correctly with the re-use of useable fuel. Because it is common to use leftover fuel, we should adapt to this reality. <o:p></o:p></span></p><p class=MsoPlainText><b><i><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'>[Frank >] True but the only way I see this being done now is fuel savings. </span></i></b><b><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'><o:p></o:p></span></b></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Paul >> As I see it, the INITIAL value and purpose of the Shields E450c proposal should be developed and (hopefully) accepted FOR GASIFIER SITUATION BASED ON MINIMAL AMOUNTS OF PRIMARY AIR. Maybe later there can be applications concerning Rockets and other stoves. But first we need to understand (and accept if correct) how E450c can help us test batch-fed gasifier stoves.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>I do not yet see why gasifiers deserve special treatment in terms of testing. It is a stove, it burns fuel. It produces heat, it conveys some of it to the pot(s). It produces emissions, it has leftovers (if it is a biomass stove). Yes there are people interested in the production of char. This is fine. If people want to know the mass of that char it is easy to report it. I people want to know the properties of that char, there is a fee attached above the regular test price. No problem. What do we <i>need</i> to know? We need to know the amount of new fuel drawn from the pile in the corner each time the test is replicated. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Frank > The measure of fuel is determine from the loss in weight from the stock pile. We start with 100 kg of wet as-received biomass. We determine the percent moisture so to calculate the dry equivalent of fuel for each gram of fuel removed. We determine the E450c in that dry fuel so now we have the E450c for each gram of fuel used. We wrap the stock pile in plastic so not to lose any moisture between tests. And plot the loss of weight of the stockpile over time (tasks, days, weeks, months, years) so to determine the fuel use for each task and for each home. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>Exactly! Now Frank, for which stoves do we <i>have</i> to find out anything about the leftover fuel? Is it only for those that re-use the fuel? It seems to me that unless there is an extra question asked, there is nearly no reason to measure the heat content of what is left. </span><b><i><span lang=EN-CA style='color:#1F497D'>[Frank >] </span></i></b><span lang=EN-CA style='color:#1F497D'>If we had a test method for doing it that worked we could – but we don’t. So its fuel savings we monitor. </span><span lang=EN-CA style='color:black'><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>What might be really helpful is a way to turn your simple approach into a poor man’s bomb calorimeter. It may require something like a correction for ash (which I think you didn’t mention but can easily be appended). <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><b><i><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'>[Frank >] Agree – I think for most fuels the ash will be small and is taken care of if using look-up tables. But should be in mind and used on fuels we suspect a lot of ash is present. And not necessary for stovers to test their own stoves during development. Its only really needed when official tests are done to compare stoves. For one fuel the ash is the same percentage of the weight of fuel used so will it make a difference if we call it 0% when it is 15% when used during stove development? <o:p></o:p></span></i></b></p><p class=MsoPlainText><b><i><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'>. </span></i></b><b><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'><o:p></o:p></span></b></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>I will try to reply directly to Ron Larsen’s question about the heat content of char remaining. People can have any test they want added to the necessary ones. It just costs more. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Frank > *For a task(s) using a fixed amount of biomass we just need to get the reactor to 450c or above.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>Exactly why?</span><b><i><span lang=EN-CA style='color:#1F497D'>[Frank >] </span></i></b><span lang=EN-CA style='color:#1F497D'> Not sure…. But temperatures > 450 have released all the energy we say is in the fuel and reactors of a lower temperature (is there such a thing?) will leave behind un-burned biomass causing efficiency values to calculate poorer. But if that is how the stove works that is what it is. So it doesn’t matter (to us heartless lab people). </span><span lang=EN-CA style='color:black'><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Frank > *For a task(s) using biomass feed into the reactor until the task(s) is completed (fuel left over) we then pick out the left over usable biomass that can be used in the next run. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Do we need to examine it if after each run the mass is the same? I think not. If there is a variation, we only need to know after the trio (or more) or runs is completed.<b><i><span style='color:#1F497D'>[Frank >] </span></i></b><span style='color:#1F497D'> agree</span><o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA>Frank > We add that to the next run and that reduces the trips to the stock pile and that shows up in the plotting of the stock pile. <o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>That is exactly the question being asked by programme managers. They want to see a reduction in that consumption. It is surprisingly easy to determine. It does not involve trying to characterise the heat content of remaining fuel because the fuel is either thrown into the next fire or disposed of in some manner (tossed, sold, ground up for medicines). Tests relevant to that subsidiary industry can be performed for anyone who wishes.<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><b><i><span lang=EN-CA style='font-size:14.0pt;color:#1F497D'><o:p> </o:p></span></i></b></p><p class=MsoPlainText><span lang=EN-CA style='color:black'>Regards<br>Crispin<o:p></o:p></span></p><p class=MsoPlainText><span lang=EN-CA style='color:black'><o:p> </o:p></span></p></div></body></html>