Fully automated systems employ a chip storage bin, typically below grade, that can hold one and a half to two tractor loads of woodchips (35-50 tons).
The bin is loaded by a self-unloading truck with no need for onsite staff assistance. From the chip storage bunker, the fuel is fed automatically to the boiler. No operator intervention is required for fuel handling. Vendor systems vary in terms of capacity and automation features.
Fully automated systems generally require very little operator attention—typically about one hour daily. They are a good match for buildings where the maintenance staff has a large work load and cannot spend much time on the heating plant.
These systems are best suited to larger schools and other buildings with significant heat loads and high conventional fuel costs since the system construction costs are relatively high.
Equipment provided and installed by the vendor includes the automated equipment to unload the storage bin, fuel-handling equipment that carries woodchip fuel to the boiler (conveyors and augers), combustion chamber and boiler, combustion air supply fans, boiler connection to the stack, controls, safety devices, and possibly emissions-control equipment.
Green woodchips (mill or forest residue, 25-50% moisture content)
Hot water or steam (boiler system)
Size (Boiler Output)
1-10 Million Btu/hr
Below-grade concrete bin (min.capacity 3500cu.ft.)
Automated from bin to combustion (no operator labor)
Operator Work Load
Approximately 30 minutes daily
Minimum 2 tuned firing levels (or modulating control)
Automated control of fuel feed and combustion air rate
"Idle" or lame maintenance mode
None required (unless required by state regulations)
Must meet applicable state regulations, if any
Manual or automated
Boiler with standard controls
Automated fuel reclaim system (in base of bin)
Automated fuel handling system (bin to combustion)
Wood system wiring (from system control panel)
Breaching (from boiler to stack)
Installation of all vendor-supplied equipment
Coordination with general contractor
(Plumbing connection by others)
(Fuel bin and boiler room construction by others)
(Bonding generally not required)