Biomass power plants – Energy from wood

In a wood-fired power plant, wood is burnt instead of fossil fuels such as coal, crude oil or gas. Otherwise, a wood-fired power plant is based on the same operating principle as a coal-fired power plant. Both are steam power plants, in which water passes through a thermodynamic cycle and the heat of a fire is converted into electrical energy.

In a closed system, water is evaporated and superheated under high pressure in a boiler. The steam is released into a steam turbine that drives an electric generator. The steam released is condensed to water using a refrigerant, and feed pumps then conduct this water back to the steam raising unit.

The crucial difference, however, lies in the fuel used. In contrast to fossil fuels, wood is CO₂-neutral, because the CO₂ released during combustion has originally been absorbed from the air by the plants while they were growing. It is mainly low-grade wood assortments such as logging remains, sawmilling off-cuts and old forest growth that is used as fuel. It is usually necessary to pulverise the wood to woodchips before use. A mid-sized wood-fired power station requires 100,000 tonnes of wood per year and generates electricity for 24,000 households.