Wood chip boilers are similar to pellet boilers apart from the fuel itself. Modern woodchip boilers are highly efficient, clean burning and are totally automatic. Wood chip boilers are more suitable for larger domestic and commercial applications. Some models designed for wood chip can also burn pellets; however boilers designed specifically for pellets cannot generally use wood chip. A wide range of boiler systems are commercially available but all share the same basic features of a boiler, a chip storage facility and a feed mechanism.
Wood chips are made from whole trees, branch wood or coppice products which are mechanically chipped. Ideally the wood needs to have been air-dried before chipping, or chipped then allowed to dry.
Wood chips are delivered into a local bunker close to the boiler; on demand the wood chips are augered into the boiler which maintains a constant fuel supply.
Wood chip boilers have combustion control technology for constant heat performance, some have vertical self-cleaning heat exchange surfaces and built in safety features such as rotary sluice prior to final combustion feed auger to prevent any back burn.
Many boilers do not have to run constantly due to auto ignition, they can run for a short period and then switch off until next needed.
- Can replace fossil fuelled boilers
- Fully automatic control/feed system
- Wood chips are cheaper than pellets
- Installations can be designed to burn pellets, sawdust & briquettes
- Boilers can be grouped together for redundancy and peak heat demands
- Remote boiler control over network or internet can be provided
- Eligible for Domestic & Non Domestic RHI
- Higher installation cost than fossil fuel
- Require larger fuel bunker than pellets
- Requires correct sized graded fuel
- Requires local maintenance & inspection
- Requires annual maintenance by engineer
- Requires ash removal
Wood Chip Feed Systems
Wood chips are usually stored in timber floored bunkers. A flexi-blade agitating head feeds the fuel into a central auger which then transports the material into the boiler feed system. For large bunkers the blades are hinged for extra reach.
Wood chips are more bulky than pellets, delivery in bulk is usual so provision to deposit them into a bunker by tipping or conveying is designed into the installation. Key considerations are access for vehicles, proximity to boiler and frequency and method of fuel delivery.