[Stoves] Top lit updraft combustors

[Law, Steven (MOECC)]

I will attach here the same excel spreadsheet I sent a few moments ago, to make sure everybody sees it so we can have a discussion where we are all on the same page.

I noticed the first website, they have it right, same as me, but the first comment at the bottom was to say they have it backwards and the reply saying that it was not backwards but correct. It seems we have much work to do on this matter!

From: Ronal W. Larson [mailto:rongretlarson at comcast.net]
Sent: December 18, 2017 4:56 PM
To: Law, Steven (MOECC)
Cc: Norbert Senf; Discussion of biomass; mhatech at yahoogroups.com; Sauve, Terrence (OMAFRA); John Ackerly
Subject: Re: [Stoves] Top lit updraft combustors

Steven,et al:

            Apologies.  I’m a lapsed EE and these issues never appeared in my world  (now primarily thinking charcoal in soil).  For that soil end use of the char,  I can’t think of a reason for caring about LHV or HHV or the same with “efficiency” tacked on (but that’s probably naive).

            I don’t propose to look much further at this issue, but wonder if these two articles found on the first page of Google results is similar to your issue.

http://adgefficiency.com/energy-basics-hhv-versus-lhv/

http://www.powermag.com/plant-efficiency-begin-with-the-right-definitions/

            In particular, however, if we are trying to determine the appropriate way to handle produced char in a world of stoves boiling water - I believe your concern not about HHV and LHV, but about their respective efficiencies could be very important in the charcoal world.  Some on this list say that the best way is to simply handle that char energy as a pure “waste” (similar to the way you probably treat ash).  So. I’d like to hear more about your work - especially if about half the potential energy (in char) is deemed a better economic (and societal) bargain if NOT consumed for cooking/boiling  purposes.

            Is it possible this is an interesting question?

Ron



On Dec 18, 2017, at 2:29 PM, Law, Steven (MOECC) <Steven.Law at ontario.ca<mailto:Steven.Law at ontario.ca>> wrote:

Hi Ron,
In the email below I am referring to the HHV or LHV reported efficiency, not the calorific value. If LHV efficiency is 90% then HHV efficiency is <84% dependent on moisture content.
You are right that if we are referring to calorific value in MJ/kg then HHV is always greater than LHV, on either a consistent wet or dry basis. This is also a function of moisture content if expressed on a wet basis and can vary widely. I believe the numbers you have shown below are reported on a dry basis and on that basis don’t vary too much.
Steven

From: Ronal W. Larson [mailto:rongretlarson at comcast.net]
Sent: December 18, 2017 4:04 PM
To: Law, Steven (MOECC)
Cc: Norbert Senf; Discussion of biomass; mhatech at yahoogroups.com<mailto:mhatech at yahoogroups.com>; Sauve, Terrence (OMAFRA); John Ackerly
Subject: Re: [Stoves] Top lit updraft combustors

Steven et al:

            Can you check your nomenclature below?.  Wiki assures me that HHV>LHV.  Typical numbers there are 21.2 and 17 MJ/kg.  I see 18 MJ/kg a lot for rough estimates - as it works nicely with other numbers.  Of course 30 MJ/kg for charcoal for similar rough calculations.

Ron


On Dec 18, 2017, at 9:24 AM, Law, Steven (MOECC) <Steven.Law at ontario.ca<mailto:Steven.Law at ontario.ca>> wrote:

Hello all,

I have finally completed a proper study of reporting efficiency using LHV and HHV. It was much more complicated than I thought it would be, and now I know why this is such a mess!

Just remember that HHV is always less than LHV, and anything above 100% is WRONG and cannot possibly conserve energy or mass and is therefore unscientific.

When an LHV efficiency from Europe is 90% (which is actually a reasonable number), the HHV efficiency is a maximum of 84% or usually less, depending on the moisture content of the wood fuel and is more typically 75-80%. This is important, HHV efficiency is extremely dependent on fuel moisture whereas LHV is less so, but only for non-condensing boilers.

Again, this is for non-condensing combustion devices, because when you throw in high efficiency condensing heat recovery all the numbers get screwy and LHV no longer applies. Everything has to be re-done for condensing boilers and only HHV can be used, I will repeat LHV cannot be used for anything where condensation of the flue gas occurs in the heat recovery device!

I think I have a proper engineering calculation procedure mapped out to deal with all of the above issues and I will begin to roll this out a little bit at a time since I need to review it again before sending anything out. It is a scientific method that is based on conservation of mass and energy and I hope that this new calculation procedure will help to solve some current problems in the industry.

Best regards, Steven


From: Norbert Senf [mailto:norbert.senf at gmail.com]
Sent: December 14, 2017 10:36 AM
To: Ronal W. Larson
Cc: Discussion of biomass; mhatech at yahoogroups.com<mailto:mhatech at yahoogroups.com>; Law, Steven (MOECC); Sauve, Terrence (OMAFRA); John Ackerly
Subject: Re: [Stoves] Top lit updraft combustors



On Thu, Dec 14, 2017 at 9:38 AM, Ronal W. Larson <rongretlarson at comcast.net<mailto:rongretlarson at comcast.net>> wrote:(snip)

So all that to say I like your “beneficial to all” approach.   What do you recommend as a first “harmonizing" fix we could start talking about?

Very good question.
Comparing even commercial heating stoves on emissions and efficiency between North America and Europe is very difficult:
- Europe uses LHV, whereas we use HHV to define efficiency, roughly a 9% difference. Quite common to see European numbers of "90% efficient" thrown around loosely and even advertised here. Using HHV, you can have efficiency higher than 100%.
- PM comparisons are next to impossible between different test methods. Until recently, Europe has been regulating on CO, which is much easier to measure. Their PM measurements are normally done with a hot filter, and therefore capture only "dust" and not condensible organic semi-volatiles.

- There is no escape here (North America) from having to compare with the defacto standard of  "The EPA Number".
This is expressed as grams per hour of PM, defined as the number you get when you follow the procedures in EPA Method 28 and EPA Method 5G ( a prescribed fueling and firing cycle and a dilution tunnel PM method that is impossible to conduct in the field). When you get into the weeds of "what is the repeatability of your laboratory method", the answer is "we don't know", and the next best answer is "plus or minus 40%, based on limited data".
For a heat storing appliance such as a masonry heater, PM in g/h (emissions rate) makes no sense, since it is zero for 90% of the heating cycle. Countries like Australia and New Zealand, with a similar dilution tunnel PM method, use g/kg (emissions factor). European PM numbers are often reported in mg/m3 of normalized exhaust gas.
The Condar has been very interesting for us. As a very tiny industry of enthusiasts, it is an affordable way to get our own reasonably equivalent data. We now have direct comparison data running it against EPA Method 5G on a regular stove, pellet stoves and masonry heaters at several EPA-accredited labs as well as a national laboratory.

If I were looking at a TLUD, for example, I'd want to know "what is the emission number, expresses as grams of PM per kilogram of fuel, using a dilution method ?". This is usually the number of interest for public health authorities, because it is thought to be the best way to model particulate emissions into the atmosphere. So perhaps this might serve as a proposal for a harmonizing measure?

--
Norbert Senf
Masonry Stove Builders
25 Brouse Road, RR 5
Shawville Québec J0X 2Y0
819.647.5092
www.heatkit.com<http://www.heatkit.com/>

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