Heating with Wood Pellets

Pellet Fuel Appliances

Pellet fuel appliances burn compacted pellets usually made of wood, but they can also be derived from other organic materials. Some models can burn nutshells, corn kernels, and small wood chips.

Pellet fuel appliances are more convenient to operate than ordinary wood stoves or fireplaces, and some have much higher combustion and heating efficiencies. As a consequence of this, they produce very little air pollution. In fact, pellet stoves are the cleanest solid fuel, residential heating appliance. Pellet stoves that are certified by the EPA are likely to be in the 70% to 83% efficiency range. 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 conventional wood-burning heater. Many can be direct-vented to the room 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 wood heaters in that they generally heat a single room well, but not adjacent rooms unless they have a fan to force the warm air into those other spaces. Pellet-fireplace inserts 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 between 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 sidewall 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. However, because the fuel is compressed, the bagged pellets can be difficult to lift.  Some models use bulk-filled storage systems and are fully automatic.

Most pellet appliance exteriors (except glass doors) stay relatively cool while operating, reducing the risk of accidental burns. Pellet stoves burn fuel so completely that 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. Moreover, they need to be cleaned by the homeowner on a weekly basis and by a professional on an annual basis. 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.

Pellet Fuel

Pellet fuel is normally sold in 40-pound (18-kg) bags at about $3 to $4 each or about $180 to $250 a ton. Most homeowners who use a pellet appliance as a main source of heat use two to three tons of pellet fuel per year. Pellet fuel appliances are almost always less expensive to operate than electric resistance heating, oil, and propane-fueled appliances.

Most pellet fuels have a moisture content of 5% to 10%. Well-seasoned firewood is usually around 20%. A few pellet manufacturers contain either petroleum or non-petroleum lignin used as a lubricant in the pellet production process, though most contain no additives.

The Pellet Fuels Institute launched the PFI Standards Program, a third-party accreditation program providing specifications for residential and commercial-grade fuel. This standard assures the consumer of the highest quality pellet when certified pellets are purchased.

You can also check pellet fuel quality by inspecting the bag for excessive dirt and dust, which can form clinkers in the stove. There should be less than one half of a cup of dust at the bottom of a 40-pound (18-kg) bag. Pellet stoves designed for low-ash content (typically top-fed stoves) tend to operate poorly when used with pellets of a higher ash content. Many pellet appliance manufacturers are redesigning their products to burn pellets with varying ash contents.

Most pellet fuel appliance dealers either maintain a supply of pellets or recommend a supplier. You may also check the local telephone listings under “Fuel” or “Pellet Fuel,” or inquire at a local tree nursery or at home and garden supply stores.

Article Source: Energy.gov

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Dave Noelke