Solid Biofuels - Central Heating
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Central Cordwood Furnaces and Boilers & Chip/Pellet-fired Furnaces and Boilers
Date introduced on the Market:
Commonly available since the early 1950’s.
Maturity of the technology:
Central wood furnaces are a low stage of technical evolution, while certain wood boilers have improved their performance, efficiency and emissions significantly in recent years. Chip/pellet-fired furnaces and boilers are in the second stage of technological development.
Expertise required for installation and operation:
Installation requires sheet metal/plumbing and electrical abilities, which are typically beyond the abilities of the owner. Installation should only be carried out by experienced, trained professionals. Operation by the owner typically requires limited training, but careful observation, to ensure good operating conditions.
Range of Operational & Maintenance requirements:
Central furnaces or boilers typically require one-to-twice daily refuelling. Once good operating practice is established, maintenance should be at least seasonal plus frequent ash removal. Pellet/chip systems typically require refuelling daily to every few days, normally will need brief daily inspection of operation and periodic ash disposal. Occasional servicing of motors & moving parts
Range of size:
Sizes are similar to twice that of a conventional oil or gas furnace. Chip and pellet systems normally range in size from that of a single car garage to a machine shed, depending mainly on how much fuel storage is incorporated. A dedicated storage area is also required to keep firewood, chips and pellets from becoming contaminated with dirt and to control moisture content.
Range of heat outputs:
Outdoor boilers range in output from around 30MJ/h to over 100 MJ/h
Chip and pellet boilers range upward in output from about 30 - 250 MJ/h.
Type of energy produced:
Units provide hot water as heat transfer medium.
Range of current capital cost per unit of delivered energy:
Central furnaces start at around $70/MJ
Central boilers start at around $100/MJ
Pellet systems start at around $120/MJ
Chip systems start at around $200/MJ
System advantages:
Central systems do provide the capability of heating the whole house. Chip and pellet systems share this advantage, as well as potentially long intervals between refuelling, and higher efficiency combined with lower emissions.
Limitation of the system:
Central furnaces are typically inefficient, can have high pollutant emissions, can spill toxic combustion products into the house, and can result in safety concerns and chimney fires, if not properly managed, Some advanced combustion central boilers have reduced these limitations significantly.
Chip systems are likely to require occasional removal of jammed chips and daily maintenance such as removal of clinkers in the firebox, plus periodic servicing of the various motors and moving parts associated with the unit.
Pellet systems are likely to need periodic removal of clinker from the combustion chamber as well as ash removal and occasional servicing of various motors and other moving parts. Corn fired systems often require more frequent removal of clinker and coke deposits.
All systems may require occasional replacement of insulation and baffles in high temperature areas.
Range of life expectancy:
All these units should have a life expectancy of 20+ years, provided they are well-run, with occasional replacement of components as they reach their design life.
Modified: 03-31-2008
