[Stoves] Fuel calculators

[Crispin Pemberton-Pigott]

Dear Calculating Stovers               

 

There is a website

http://www.fpl.fs.fed.us/products/publications/specific_pub.php?posting_id=1
7526
<http://www.fpl.fs.fed.us/products/publications/specific_pub.php?posting_id=
17526&header_id=p> &header_id=p

 

with a Fuel Value and Power calculator accessible through the links near the
top. One is

 

('/documnts/techline/fuel-value-calculator.xlsx');

 

That file looks like this:



 

There is a link at the bottom to

http://www.fpl.fs.fed.us/documnts/techline/fuel-value-calculator.pdf

 

which has a nice table of fuels and some estimated heating costs associated
with moisture and product efficiency.

 

So, I have a question: what are the underlying assumptions used when
calculating the energy and efficiencies - assumptions used by the USDOE,
USDA Forest Service, EPA and manufacturers?

 

What makes it difficult to work out fundamental numbers using these charts
is there is no attempt to do the calculations based on the methods that have
been popularised in this Stoves group: i.e. do everything in Joules and
calculate the answer at the end.

 

That may be from a long history of strong European, particularly German and
Dutch, involvement in the small stove sector. My first question is, are all
these American heat contents, given in BTU/ton, based on the HHV, dry? 

 

When conducting an exploration of EPA methods last year with CAU we
discovered that in no case was the dry heating value used, it was always
given with a certain moisture content and expressed on an HHV basis (wet).
This is very convenient if one has a bomb calorimeter and very inconvenient
if one wants to assess the fuel per test and use a baseline LHV. 

 

As the choice of a mass-based metric is already a complicating factor,
because a different species has a different energy content per unit of mass,
comparisons between tests are either difficult or vague. Pick one.
Expressing emissions on the basis of mass burned is equally antiquated and
fraught.

 

Proposals by the manufacturers to the EPA have consistently tried to get
them to use energy based calculations as per Europe and per this stove group
- because it is more accurate and makes more sense. 

 

So if anyone know, perhaps Tom M, the values given in the column "Hardwood,
kiln dried (8% moisture)" in the chart at
http://www.fpl.fs.fed.us/documnts/techline/fuel-value-calculator.pdf - is
the efficiency based on the HHV or LHV? From what I read it seems it is the
HHV. I have seen some complaining about the European efficiency and US
efficiency comparisons directly related to the HHV/LHV question.  The logic
behind using HHV that might be the existence of condensing furnaces. 

 

If we start to build really high efficiency heat exchangers we the small
stove community will have to start looking into fundamental changes in some
of the formulae.

 

Thanks

Crispin

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