Small Heating Plants

The numbers of small bioenergy-fuelled heating plants are increasing rapidly. As oil prices rise, oil-fired plants are widely shifting over to bioenergy, with old oil-fired boilers replaced by boilers that can be fuelled with wood-based biomass.

Commercial scale biofuel boilers (100 kW-1 MW) can be used for heating schemes that warm a single large building such as an industrial facility or provide district heating for several commercial and/or residential buildings in a neighbourhood.

Biofuel boilers of this size have widely been fitted in Finland to replace oil boilers, though in many cases oil boilers may be kept connected to the system to provide an alternative heat source or supplementary capacity to meet peak demand.

To keep costs down, small heating plants should usually have plenty of suitable fuel storage space and automatic systems that enable heat production to be monitored remotely.

The most important elements of small-scale heating plants are:

• Fuel storage space with an automatic feeding system;
• Boiler fed by an automatic fuel feeding system;
• Control system with instrumentation to facilitate monitorin; and
• Connections to the heating pipe network.

A back-up boiler or electric heating system may also be needed, depending on the size of the plant.

Chips or pellets?

The advantages of wood pellets include low moisture content and ease of storage and handling. One drawback has been a considerable recent increase in wood pellet prices.

Quality requirements for wood chips are an important factor for smaller heating plant boilers whose fuel feeding systems may not be able to cope with oversized chips. Such boilers need to be supplied with uniform wood chips with suitable moisture content, though the same is true for any other facilities using wood chips.

Mixing wood chips and pellets can improve the efficiency of heat production during peak winter use, or enable the use of any batches of poorer quality wood chips delivered to the facility from time to time.