[Stoves] Energy loss in making high grade fuels

[Tom Miles]

Ron, Andrew

A very rough estimate:
Gross Calorific Value (dry basis) for wood pellets is 5.5 kWh/kg or 5,500
kWh/tonne. (4.6 kWh/kg at 10 % MC). 
(Biomass Combustion and Co-firing Handbook, S.van Loo and J Koppejan (ed),
http://www.ieabcc.nl/ )

Fuel to dry wood increases the wood requirement to make a tonne of pellets
by about 15%, or 15% x 5,000 = 825 kWh. 
Electrcial energy for the pellet plants we design is between 130-150
kWhe/tonne. Specific energy for the pellet machine is about 80 kWe. The rest
is auxiliary equipment for conveying, sizing, etc. 150 x 5  (energy from
wood at 20% efficiency) = 750 kWh. (750/5500 = 14% of GCV)
Total 750+825 = 1575 kWh/tonne. 
1575/5500 = 29% of GCV

Dr. Sahab Sokjansanj, Oak Ridge National Laboratory, and others have done
more detailed analyses that have been published in US Department of Energy
reports and journals of the American Association of  Agricultural and
Biological Engineers (ASABE). 
http://www.esd.ornl.gov/people/sokhansanj/
  
There has also been significant work funded by the EU in the last five years
on pelleting energy requirements. 

Regards,

Tom


-----Original Message-----
From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
ajheggie at gmail.com
Sent: Thursday, March 15, 2012 1:15 AM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Energy loss in making high grade fuels

On Wed, 14 Mar 2012 04:28:33 +0000 (UTC), rongretlarson at comcast.net
wrote:

>A widely different number was given by wiki at 2% for pelletizing

This was the figure mooted by the pellet die makers when we were involved
with setting up in Wales. It was strictly for the pressing operation and
took no account of comminuting, drying or conveying the raw material or
produce.

It is also the electricity required, which if bought from the UK grid has
been converted from thermal power at a rate of 30%.

AJH


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