Maximum electrical generation from a quantity of wood:

I just fielded a question on the Yahoo wood gas forum about the maximum amount of electricity that could be generated from a quantity of wood.  Here is my reply:

Bone dry wood can produce 8600 Btu/lb when burned perfectly.

1 Btu = .000293 kWhr’s

Therefore 1lb(or .454kg) has (1lb * 8600 Btu/lb * .000293 kWhr/Btu) = 2.52kWhr’s of thermal energy stored in it.

Now if we consider converting that thermal energy into electrical energy I get something on the order of:

Actual maximum output = (Gasifier efficiency)*(engine efficiency)*(genhead efficiency)*(energy input)

Actual maximum output = (.7)*(.2)*(.7)*(2.52 kWhr/lb)

Actual maximum output = .25 kWhr/lb or (.25 kWhr/.454kg = .55 kWhr/kg)

Realistic output accounting for wood moisture ~ .2 kWhr/lb or .44 kWhr/kg

So in order to run my inefficient house that uses 40kWhr’s/day I would need about 200lbs of wood per day to satisfy my electrical demands.  In my case I have an in law apartment, three hot water heaters, an electric stove, an electric clothes dryer, a furnace, and my plasma cutting shop.  If I were to reclaim the exhaust heat from the generator for water heating I could probably cut that number in half.