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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.
Quick Facts:
| Primary Fuel |
Green woodchips (mill or forest residue, 25-50% moisture content) |
| Energy Output |
Hot water or steam (boiler system) |
| Size (Boiler Output) |
1–10MillionBtu/hour |
| Fuel Storage |
Below-grade concrete bin (min.capacity3500cu.ft.) |
| Fuel Handling |
Automated from bin to combustion (no operator labor) |
| Operator Work Load |
Approximately 30 minutes daily |
| Combustion Control |
PLC-based panel Minimum 2 tuned firing levels(or modulating control) Automated control of fuel feed and combustion air rate “Idle” or lame maintenance mode DDC compatible |
| Stack Emission |
None required (unless required by state regulations) |
| Control Device |
Must meet applicable state regulations, if any |
| Ash Removal |
Manual or automated |
| Vendor-Supplied |
Boiler with standard controls |
| Equipment |
Combustion chamber Automated fuel reclaim system (in base of bin) Automated fuel handling system (bin to combustion) Control panel Wood system wiring (from system control panel) Breaching (from boiler to stack) |
| Vendor Responsibilities |
Installation of all vendor-supplied equipment Coordination with general contractor Warranty Service capability (Plumbing connection by others) (Fuel bin and boiler room construction by others) (Bonding generally not required) |
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