Biomass Stoves
What are Biomass Stoves?
What do we mean by Biomass?
Biomass is material that is made from biological products, such as wood and plants that can be used to produce energy when burned. There are a number of different types of biomass fuels, however, the most popular types of biomass for domestic space heating and hot water purposes are logs, wood chips or wood pellets.
Biomass pellets are made from low-grade by-products of the wood processing industry such as dry sawdust and shavings, produced in large quantities. The material is compressed under high pressure and extruded through a mould to form pellets. The heat they produce is comparable to domestic heating oil, however, they are approximately 40%* cheaper and require less storage space than lower density fuels such as wood chips.
What are Biomass Stoves?
Biomass stoves can offer a very low cost supplemental (or in some cases, primary) heating source for the home. They may look like traditional wood burners, but the similarities end there. The two main types of system in the UK are:
Wood-Burning Stove
A modern wood-burning stove can burn a number of different types of wood products, from woodchips of varying sizes through to logs. They are set, lit, and stoked by hand like a traditional wood burner. However, they have the benefit of being far more efficient, and so require less amounts of wood than their predecessors. When they burn, they release less smoke during operation and produce dramatically less ash.
Pellet Stove
Pellet stoves are very similar to wood burning stoves, although instead of burning wood, they burn small biomass pellets. They are more sophisticated combustion appliances that have the advantage of being more user-friendly than a wood burning stove. Rather than having to set and light a fire on a daily basis, with a pellet stove pellets are automatically fed into the stove (from a hopper that generally holds about two to three days worth). The fire can also be lit electrically, and with some models this can actually be requested by text message remotely, so you can get your room warm for when you arrive.
Why is biomass considered a renewable low carbon fuel?
The primary source of energy contained within all biomass fuels is energy from the sun that is captured and stored via the process of photosynthesis. This energy can be released and used (e.g. by combustion). When this occurs, CO2 is released. However, the CO2 released is largely offset by that which was absorbed in the original growth of the biomass, or which will be captured in the growth of new biomass to replace the biomass being used (as illustrated above). Consequently biomass combustion is considered to be a low carbon technology if the material is derived from sustainable sources.
How Does a Pellet Stove Work?
Pellet stoves utilise electronically controlled combustion, blowers, and highly effective heat exchangers to provide reliable, efficient heating. You pour the pellets into a holding bin or hopper, which is located either at the top or bottom of the unit.
Most stoves have an electrically operated spiral conveyor (auger) that delivers pellets from the hopper to the combustion chamber. The auger's movement is operated by a control that is set manually or, for some stoves, by an optional wall-mounted thermostat. A fire's size depends on the rate of feed. The pellets are fed to a fire pot or burner ring in the combustion chamber. Combustion air is blown into the chamber to encourage a super-heated flame. You must light some pellet stoves; others are self-lighting.
Room air is drawn in by a fan and blown across the heat exchanger, which is heated to about 250C, and the warmed air is returned to the room. The sides and rear of many stoves are specially shielded in order to a create convection flow of heated air. Unlike the majority of wood stoves, most pellet stoves rely on convective heat, rather than radiant heat. As a result, most pellet stoves don't get too hot to touch which can be an important consideration for families with small children. Although some models deliver heat by a combination of convection and direct heating, where the glass front delivers the heat directly into the room.
Residual combustion gases are vented outside, normally through a 3-inch flue that exits out the unit's back or top. Though most pellet stoves don't require a conventional chimney, saving you from considerable expense and design inflexibility, most types draw better if the flue goes out through the wall and turns upward. For safety and soot control, it's wise to extend the vertical section past the eaves.
Biomass stoves produce heat which is transferred to air and used for space heating and in the case of back boiler models, water heating (not shown). 1. Pellet Hopper, 2. Spiral Conveyor, 3. Combustion Chamber, 4. Fan, 5. Heated air, 6. Glass front, 7. Flue, 8. Ashtray.
What Can IT Be Used For?
A large variety of biomass stoves are available in a number of styles, both traditional and modern, for freestanding and also fireplace inserts. The freestanding stoves can generally be placed against most outside walls and a flue created. The fireplace inserts allow you to use an existing fireplace as a location for the stove to sit in. Biomass stoves can be used in the following applications:
Space Heating
The most common use of a biomass stove is to provide space heating for a single room. and they generally have 5-7 kW output that is sufficient for this purpose. They can sometimes be positioned to provide supplemental heating for adjoining rooms.
Space Heating & Water Heating
It is also possible for some models to be fitted with a back boiler that can provide water heating when the stove is lit. These tend to have higher outputs and should be sized according to water requirement and alternative water heating sources.
Is It Suitable For My Requirements?
Biomass can be an excellent supplementary source of heating and can provide a perfect solution to reducing energy bills. However, deciding whether a biomass system is appropriate for you or your project requires consideration of a number of factors. The following are some general principles that will help you decide whether it is a technology you would like to consider in more detail for your property:
Fuel Supply & Quality
Whenever a biomass installation is planned, the intended sources of fuel should always be included in the planning and the equipment specified accordingly. In the UK, pellets are available by the bag and in some areas by bulk tanker. Green Energy Doctor can assist you in finding a suitable fuel supply.
Fuel Cost
A cost comparison with the home's current heating fuel should be done. Any financial savings would be dependent on a comparison with alternative fuels and on the specific type of biomass fuel used and the regional price variances.
Fuel Storage
Any design must ensure that there is a suitably large and dry area, that is sufficiently close to the intended site of the stove to store the wood or pellets. Green Energy Doctor can advise on a suitable storage area or system.
Flue
If your stove is installed on an outside wall, a simple flue can be used for venting. The vent material must be specifically designed for wood fuel appliances and there must be sufficient air movement for proper operation of the stove. Chimneys can be fitted with a lined flue that is more suitable for a stove insert that would sit in the fireplace.
Location
Choosing the right location to get the most out of you stove is an important consideration. It should be located in an area of the house you want to be the warmest. This is usually the main floor area where kitchen, living and dining rooms are located and where the family normally spend most of their time.
Maintenance
Pellet stoves have a variety of moving parts and motors that require occasional maintenance. It's a good idea to select a model that gives you easy access to any parts that need care.
Electricity Supply
Although wood burning stoves can operate without an electric power supply, a pellet stove requires electricity to operate by blowing air into the combustion chamber and moving the pellets in. You should ensure a electrical supply is available and also consider that if the power fails, it will stop burning. However battery back-ups are available.
Planning
If the building is listed or in an area of outstanding natural beauty (AONB), then you will need to check with your Local Authority Planning Department before a flue is fitted.
Regulations
The installation must comply with all safety and building regulations.
What Are The Benefits?
Reduce Your Energy Bills
Wind energy is one of the lowest-priced renewable energy technologies available today. With the correct location and a turbine system that is sized correctly according to your power requirements, you can expect to save between 25 - 30% off your electricity annually.
Reduce Your Impact On The Environment
Wind energy is fuelled by the wind, so it's a clean fuel source. Wind energy doesn't pollute the air like power plants that rely on combustion of fossil fuels, such as coal or natural gas. Wind turbines don't produce atmospheric emissions that cause acid rain or greenhouse gasses.
Reduce Your Dependency On Fossil Fuel Imports
The wind is a free source of energy and is estimated to be secure for the next few million years. This can provide you with the peace of mind that a significant proportion of your energy is under your control and will not increase in price as a result of foreign government actions or the prevailing economic climate.
Sell Surplus Electricity Back To Grid
If your wind turbine is producing more electricity than you require, the excess can be exported back onto the National Grid using an export meter. The rate paid various from company to company but some tariffs offer over 10p per kWh.
Sell Renewable Obligation Certificates (ROC's)
Eligible sustainable generators, including consumers are awarded these digital certificates for every 1000kwhrs of electricity generated. Energy Companies are required to generate a minimum level of their electricity output from sustainable sources. If they have not managed to produce the required amount of green energy themselves they must buy ROCs on the open market to make up the shortfall. This certificate can be sold to electricity suppliers for up to �40, this equates to an additional 4p per kWh.
How to Get Started...
To organise a no obligation site visit or to start moving your project forward contact the Green Energy Doctor today on:
T: 0845 009 5652
E: info@greenenergydoctor.co.uk