coppice-farm/index.html
Old maple stumps have multiple new trunks growing out of them. Some of these individual trunks are cut and new shoots are allowed to turn back into trunks.
The attempt is to provide household heating with totally renewable energy.
Maple has a high energy content per weight.
3680 lbs/cord
1.8 kw hrs/lb
dried maple is about 75% of the weight of green wood
it takes me 30 minutes to cut 110 lbs of wet wood (which should give about 80 lbs of dry wood).
If the new stove will have an energy conversion factor of 45 %. Energy in the wood that goes into the house as heat.
each kw-hr of heat requires 1.2 lbs of wood
1.2 lbs of wood requires .33 minutes (i.e.20 seconds) of my time just to cut it. Which makes my time cutting wood worth $25 per hour (if I make it equivalent to the cost of electricity).
Comparing this to electricity, natural gas and oil options
electricity
$0.14 per kw hr (current average PGE rate)
electric heaters are 100% efficient at deliving heat to the house
oil
$1.80 per gallon for home heating fuel
oil contains 1.24 * 10^ BTU per gallon --> 1.24*10^5 *(2.928 * 10^-4 kw hr/btu) = about 36 kw hr per gallon.
1 gal of gas can give 11 kw-hr in a generator that works at abou 30% efficiency. This means that I can generate my own electricity for $1.80 gal gas/11 kw-hr or $0.16 per kw-hr
taken from http://www-personal.umich.edu/~rcnh/gs102/EnergyEquiv.html
furnace is ** % efficient
dollar per kw hr heat delivered to house
Value of wood for heating
Measurements are being taken now to determine how much time it takes to cut and process one trunk.
preliminary measurements
2004.01.13 31 lbs of wood in ten minutes (batch 1) - from fallen limb
2004.01.13 113 lbs of wood in 30 minutes (batch 2) - from coppice cutting
Cut down one trunk in a coppice. I weighed the total amount of wood and then cut it up into 16 inch sections and put it into dry. The trunk was about 8 years old.
dried these for 150 days
% decrease in weight had a range batch 1 went down to 77% of its original weight, batch 2a to 69% and batch 2b to 65%
The numbers for batch 2 are less than reported for other maple (75%) but this was a fresh, small tree with wet bark in the middle of winter.