Nearly all systems using cordwood gasification or pellet-fueled boilers perform best when the system includes a thermal storage tank. That tank absorbs heat during the boiler’s typical 2 to 4 hour burn-cycle, allowing the boiler to remain at or close to steady state conditions. This increases thermal efficiency and significantly reduces particulate emissions.

A thermal storage guideline for pellet-fueled boilers is 2 gallons of water per 1,000 Btu/h of the boiler’s rated output. For cordwood gasification boilers, the guideline is 130 gallons of water per cubic foot of the boiler’s primary combustion chamber. When these guidelines are applied, even residential systems require substantial amounts of thermal storage.