Dear Crispin and all, (to be posted also at www.drtlud.com )
I have been reading the previous messages, and now offer some comments:
1. The FULL data from the Quad 2 tests were provided to stimulate
discussions, and I am delighted that Crispin and some others are digging
into it as an example of the testing procedures. I do not run the
rests and do not participate in the definition of the test procedures.
Maybe other stove manufacturers could release (or point to current
availability of) full results of tests on their stoves. I will not
study their data from the point of view of test procedures, but others
might.
2. I accept Crispin's position about the difference between FUEL
efficiency and ENERGY efficiency, but with this observation: Crispin
said something like: "Fuel from the woodpile" or "wood from the fuel
pile" should be what is counted. TLUDs take in fuel and operate best
if the full batch of fuel is pyrolyzed, leaving behind char that is
certainly not like the original fuel. That original fuel is gone!!
Therefore, if "fuel put into the stove, minus that SAME fuel that can be
saved" is the amount considered in the FUEL efficiency, then a TLUD
could use more fuel that other stoves. HOWEVER:
3. This could imply that the stove was operated until the end of
pyrolysis even if that was many minutes after the complete WBT was
conducted. Unfair disadvantage to batch stoves. PARTIAL SOLUTION
that creates havoc is that the SAME stove could be operated identically
with the amount of fuel carefully calculated to have pyroylsis end
within a minute after the WBT was completed. Fill a TLUD with 3 kg of
fuel for one test run, and then do it with 1 kg for the second test
run. In other words, Crispin's correct statement (that the original
loading of 1600 grams of wood) is NOT related to the amount of FUEL used
up until the time of the completion of the WBT.
4. Because TLUDs can utilize so many different types of dry biomass
EQUALLY WELL, and because reduction of burning of WOOD is so important,
then what if the test was done with maize cobs or with stalks or with
briquettes from true "waste" or with inedible Jatropha seeds? Then
the following would be true:
"No fuel was taken from the woodpile" and "No wood was
taken from the fuel pile."
So the impact of WOODY fuel savings means the TLUDs are the clear
winners!!!
Remember, the definition that the fuel is to be some uniform type of
WOOD (to ensure comparability between the stoves) is what has forced the
TLUDs to be tested with wood. How well I remember the Stove Camps at
Aprovecho (I have attended seven thus far) where the kiln-dried Douglas
fir was the only acceptable fuel for the testing.
5. About testing of char-making stoves, that include the TLUDs:
Granted that char is not the original fuel.
But the remaining char can have substantially greater value on a weight
basis (and perhaps in other ways also) than the biomass that was the
feedstock. And that char can be for A) burning or for B) biochar (soil
amendment) or for C) carbon sequestration/climate change/carbon
credits. AND B and C can be cumulative!!!! Or D) it could be
thrown away.
Example: Actual figures: Chip Energy has a Biomass Furnace (AVUD,
not TLUD) that can use pellets (and other dry biomass), with a resultant
yield of much heat plus char. Pellets purchased retail at under one
dollar for 10 pounds will yield 2 pounds of char that is quite
respectable for sale as biochar at one dollar for 2 pounds. THAT
Biochar has 5 times the monetary value by weight compared to pellets.
Meanwhile, all of the heat energy was essentially FREE to heat the Chip
Energy building during the winter months.
If this example is transformed to be a cookstove (and it is, in the
TLUDs), the HEAT for cooking could be considered free if the user gives
reasonable value to the char as biochar. And do it with maize cobs in
a rural village where the soil is poor and responds well to the addition
of biochar.
So, concerning FUEL effeciency, W H O R E A L L Y C A R E S
what the numbers are from the WBT xxx.yy?
Yes, I really do care. and we all should care. but "do not crucify
the TLUDs on a cross of carbon."
Fix (adjust, not "fix" as in illegal horseracing) the tests any way that
allows for true differences between stoves to be observed. Just
please do not have testing that poisons the waterhole for those who are
working with TLUD and other micro-gasifier stoves.
Professional chemical engineer Hugh McLaughlin and I are examining the
issues of testing, and output (if any) should be ready before ETHOS in
late January. The task is not a pleasant one.
Paul
Paul S. Anderson, PhD aka "Dr TLUD"
Email: [email protected] Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 12/6/2012 11:37 PM, Crispin Pemberton-Pigott wrote:
Dear Frank
I am going to discuss the WBT 4.1.2 below, not the UCB-WBT 3.1 which
is old now.
What matters is what people who select stoves for their promotion
programmes /think/ the fuel consumption number is. If people think
that conducting 15 back to back water boiling tests will require a
wood pile with a mass of 15 times the WBT fuel consumption number,
then we should provide a consumption number that is the actual fuel
consumed per replication of the test. We speak of 'dry fuel' because
of course the moisture content affects the mass consumed. Correcting
for it is reasonable.
Is there any doubt that people think the 'fuel consumption' recorded
by the end of the test is the amount of fuel consumed?
Here is the text from the CREEC laboratory at the bottom of the Quad 2
TLUD test:
"The Quad 2 stove boils 5L of water in 27 minutes, uses 636 g of wood
to boil and simmer (cook) 5L and has an energy use of 11713KJ."
This gives the impression to any careful reader that the fuel consumed
per WBT is 636 g. The actual fuel needed each time the stove is
operated is about 1600 g.
Most interestingly the energy consumption is 11,713 Joules. It is
energy efficient. The dry fuel equivalent of that amount of energy is
indeed 636 dry g of fuel (gum tree). So why the large difference? It
is because of the charcoal produced, not burned, and unburnable in
that stove. This was what Jim Jetter and others have been discussing
with me off-list.
The suggested fuel consumption definition attempts to describe, for
many different stove types, how to determine the new fuel you would
need per replication to keep on repeating an experiment, in this case
the WBT 4.1.2.
Because some stoves can use fuel remaining from the previous cooking
cycle. In that is the case, the each test should /start/ with that
same 'left over fuel' from a previous cycle. If you claim that the
remaining char can be used in the same stove next time, prove it by
starting the test with the typical amount left from an earlier
identical cycle. The advantage of this approach is it corrects for
fuel heat determination errors that are almost impossible to correct
in a simple lab.
Suppose starting a stove wasted, each time, 250 g of fuel just to get
the fire going properly. That is not unused fuel, it is needed each
time because of some characteristics of the stove. We count it even
though the energy needed to cook on the established fire starts
counting when the pot goes on. The 'energy needed' is the figure used
to calculate the thermal efficiency from the fire to the pot. It is a
valuable metric for the design who needs to know how the stove
structure is performing.
As seen when calculating the CO2, CO and other gas outputs, the
difference between fuel consumption and energy production is real.
Simply stated, a stove can be energy efficient but fuel inefficient.
Regards
Crispin
+++++++++++++
Dear Crispin,
"Fuel consumption : The mass quantity of new, raw fuel required to
replicate any prescribed performance cycle, per replication, ignoring
the results of the first cycle in any series of such replications.
Combustible material in any condition remaining from one replication
which may be used by the same device as fuel in the next should be so
used unless it is common practice in the target community not to do so
in which case the test may be conducted with new raw fuel only."
Not sure if this applies here but it seems to me the error is at the
start (heating up stove body, getting the fire lite etc) and at the
end (measuring flaming fuel left over). To test stoves we can continue
the burn for a long time (simmering and boiling) using a --lot- more
fuel reduces these two errors at the ends and may give a better
indication of stove efficiency. If we can't get the bias and
precision needed when trying to simulate a 'meal' we may need to go to
these longer times -- and I think we should. You say that when you
say : The mass quantity of new, raw fuel required to replicate any
prescribed performance cycle. It's the amount of fuel (time burning)
that is adjusted. To determine efficiencies at start and end is
entirely another procedure. As I see it.
Frank
*From:*Stoves [mailto:[email protected]] *On
Behalf Of *Crispin Pemberton-Pigott
*Sent:* Thursday, December 06, 2012 4:12 PM
*To:* Stoves
*Subject:* Re: [Stoves] FW: ETHOS 2013: Where is the New Data on Stove
Performance in the Field?
Dear Jim
I am just getting to your message of Nov 30. I have not been ignoring
the conversation. I have just read it and respond as follows:
Snipped the long but useful message.
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