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Vacuum-Bag Lumber Kiln on a Concrete Pad Using Wood Fired Boiler Water Heat

Power & Fuel Budget Infographic

Vacuum-Bag Kiln, Wood-Fired Hot Water Version

Same 5,000 board-foot charge, same concrete pad and vacuum bag — heat now comes from a wood-fired boiler through hot-water platens, not electric blankets

Charge: 5,000 bd ft
60% → 8% MC
Cycle: 58 hours
Heat source: wood-fired boiler
Delivery: hot-water platens

How it works

WOOD-FIRED BOILER 0.63 cords / charge (scrap / waste wood) CIRCULATOR 1 hp hot supply cooler return REINFORCED CONCRETE PAD VACUUM BAG (≈26 in Hg) 10 hp VACUUM PUMP ALUMINUM PLATENS — hot water conduction heating

Only the vacuum pump, circulator pump, and boiler auxiliaries (fan, auger, igniter) draw grid power. The heat itself comes from burning wood fuel, not electricity.

Fuel & process energy — design case (60% → 8% MC)

2,491 kWh
Heat delivered to wood
3,114 kWh
Heat needed at platens (+25% loss)
0.63 cords
Dry hardwood fuel (70% boiler eff.)
~2,530 lb
Wood fuel per charge

Electrical load — pumps & controls only

7.46 kW
Vacuum pump (10 hp)
0.75 kW
Circulator pump (1 hp)
1.5 kW
Boiler auxiliaries
10.7 kW
Total connected load
Vacuum pump 7.46 kW
Vacuum pump Circulator pump Boiler auxiliaries Controls

Electric vs. wood-fired — same charge, same kiln

Electric resistance blankets

Connected load110.0 kW
Energy per charge3,515 kWh
Cost @ $0.11/kWh$386.70
Service required175–200 A, 480 V 3φ

Wood-fired hot water

Connected load10.7 kW
Electric energy per charge290 kWh
Electric cost @ $0.11/kWh$31.89
Service required≈50–60 A, single/split-phase
−90%
connected electrical load

If the fuel isn't free

Wood fuel @ $200/cord $126.52
+ electric parasitic load $31.89
Total (fuel purchased)
$158.41 / charge

Electrical Savings per Year Using Wood Boiler for Heat Source

Running back-to-back with no turnaround loss, the kiln completes 151 charges a year (58-hr cycles, 8,760 hrs/yr) — about 755,000 board feet.

Electric resistance design: 530,886 kWh/yr → $58,397/yr at $0.11/kWh.

Wood-fired hot water design (pumps + controls only): 43,785 kWh/yr → $4,816/yr.

Annual electrical savings: 487,101 kWh, or $53,581/yr (92% less grid electricity).

That comes at the cost of about 95 cords/yr of wood fuel. If that wood isn't actually free and you priced it at $200/cord ($19,030/yr), the wood-fired design still comes out $34,551/yr ahead of the electric design (59% total cost savings) — the boiler fuel is just cheaper per delivered BTU than grid electricity even when it isn't free.

CONTACT TEL: 608-238-6001 Email: greg@globalmicroturbine.com | AMP | PDF