Wood Heating Systems
Wood has been the most important fuel used by humans for thousands of years. The renewed interest in wood fuel is being driven by economic and environmental concerns – wood fuel is increasingly price competitive with fossil fuel alternatives and the environmental benefits of wood fuel are now being recognised and valued. Wood fuel also has a key environmental benefit over fossil fuels in that wood is ‘carbon neutral’ when wood that is combusted to produce energy is replaced by new trees. Traditionally the systems used were inefficient open fires however these systems have now been replaced by more efficient systems.
Wood fuels come in a number of different forms:
- Picture of woodchips
- Wood Chips
These are produced mainly from forestry residues. They are a bulk fuel and more generally used for larger buildings or district heating projects. Storage is important
as the ideal moisture content should be no more than 30% for domestic applications
Chips are produced using machinery with sharp knives which will define the size of the chips . The boiler selected will determine the size of the chips to be used.
- Wood Pellets
Picture of wood pellets
Wood pellets are made from sawdust, compressed into uniform diameter (6 to 8 mm pellets).They are a clean, renewable, standardised fuel and should conform to European Quality standards for pellets as defined in CEN/TC 14961.
One tonne of pellets contains the same amount of energy as 500 litres of oil and has a volume of 1.8m3.
Storage of the pellets is very important as they need to be kept dry ( less than 8% moisture )to ensure the efficiency of the system
- Wood Briquettes
Picture of wood briquettes
Wood Briquettes are also made of sawdust and are larger version of wood pellets. They also need to be protected from rain and frost to ensure efficiency
- Wood logs
picture of wood logs
These are produced from forestry. the logs can be up to 100cm long and 15cm tick.
In Tipperary, there have been in excess of 200 domestic Biomass systems installed since the introduction of the Greener Homes Scheme.
Description of the system
Wood heating system schematic
A Biomass system is composed of:
<!–[endif]–><!–[if !ppt]–><!–[endif]–>
- A Fuel supply and storage . For effficient running of system, the fuel supply should be of good quality. Storage would be important as the wood needs to be kept dried, the location should be of easy access for delivery and uploading.
- Fuel distribution this will feed the wood supply to the combustion system. For wood pellets for example this would the auger feeding into the system
- Fuel combustion system . This will turn the wood supply into heat. Combustion sytems include stoves, boilers…..
- Heat distribution system. These are also called heat emitters, will get the heat into the rooms . There are various types ranging from traditional radiators , underfloor heating and room heaters.
- Controls. These will help to monitor the output of heat throughout the proces and will include timeswitch, thermostats, programmers…..
Type of combustion sytems available
Pellet stoves are stand alone units which are particularly well suited to open plan areas
Log boilers would be better suited to larger systems
pellet boilers are ideal for domestic hot water and heating in most houses
Log boilers would be better suited to larger systems
pellet boilers are ideal for domestic hot water and heating in most houses
Other aspects to consider when installing a system
- Flue
The flue system will get rid of the exhaust from the boiler
- Air supply
This is very important for the safe operation of the system. Best practise is to rely upon dedicated ventilation and not on air infiltration and/or leakage in the room.
- Insulation of the pipes
This is very important especially if the combustion system is located away from the house for example in a garage. By insulating the pipes you are reducing the heat losses.
For more infomation about Wood Heating Systems and the grants available
SEAI administer the grants. More information can be found on their website
They also have additional information on Wood Heating and buyers guides
One of the first European projects the agency worked on was focusing on assessing the potential for developing a market for wood pellets in relation to the domestic market
Other useful contacts:
