Pellet Fuel Appliances
Pellet fuel appliances burn small, 3/8–1 inch (100–254 millimeter
[mm])-long pellets that look like rabbit feed. Pellets are made from
compacted sawdust, wood chips, bark, agricultural crop waste, waste paper,
and other organic materials. Some models can also burn nutshells, corn
kernels, and small wood chips. They are more convenient to operate and
have much higher combustion and heating efficiencies than ordinary wood
stoves or fireplaces. As a consequence of this, they produce very little
air pollution. In fact, pellet stoves are the cleanest of solid
fuel-burning residential heating appliances. With combustion efficiencies
of 78%–85%, they are also exempt from United States Environmental
Protection Agency (EPA) smoke-emission testing requirements. Pellet stoves
have heating capacities that range between 8,000 and 90,000 Btu per hour.
They are suitable for homes as well as apartments or condominiums.
Most pellet stoves cost between $1,700 and $3,000. However, a pellet
stove is often cheaper to install than a cordwood-burning heater. Many can
be direct-vented and do not need an expensive chimney or flue. As a
result, the installed cost of the entire system may be less than that of a
conventional wood stove.
Pellet fuel appliances are available as freestanding stoves or
fireplace inserts. Freestanding units resemble conventional cordwood
heaters in that they generally heat a single room well, but not adjacent
rooms unless you use a fan to force the warm air into those other spaces.
There are also fireplace inserts that fit into existing fireplaces.
Several companies now make pellet-fired furnaces and boilers for
replacement of, or a supplement to, gas or oil fired furnaces and boilers
in residential space heating systems.
All pellet fuel appliances have a fuel hopper to store the pellets
until they are needed for burning. Most hoppers hold 35 and 130 pounds (16
and 60 kilograms [kg]) of fuel, which will last a day or more under normal
operating conditions. A feeder device, like a large screw, drops a few
pellets at a time into the combustion chamber for burning. How quickly
pellets are fed to the burner determines the heat output. The exhaust
gases are vented by way of a small flue pipe that can be directed out a
side wall or upwards through the roof. More advanced models have a small
computer and thermostat to govern the pellet feed rate.
Pellet appliances usually require refueling only once a day, and since
the fuel is compressed and bagged, the operator does not have to lift
heavy, dirty logs. Most pellet appliance exteriors (except glass doors)
stay relatively cool while operating, reducing the risk of accidental
burns. Since pellet stoves burn fuel so completely, very little creosote
builds up in the flue, posing less of a fire hazard.
Unfortunately, pellet appliances are also more complex and have
expensive components that can break down. They also require electricity to
run fans, controls, and pellet feeders. Under normal usage, they consume
about 100 kilowatt-hours (kWh) or about $9 worth of electricity per month.
Unless the stove has a back-up power supply, the loss of electric power
results in no heat and possibly some smoke in the house.
Source: U.S. Department of Energy |
