The district heating experts at Stadtwerke Gießen AG (SWG) have set another milestone for a sustainable energy supply: Reinhard Paul (Technical Director) and Matthias Funk (Head of District Heating Supply) together with Dr Gerd Hasselbach (Head of Municipal Cleaning and Pooh Office) have commissioned a biomass cogeneration plant fuelled by wood chips on the premises of the municipal cleaning and pooh office. After a short trial period, the plant is now in continuous operation. The biomass boiler plant with a firing capacity of 990 kW is integrated into SWG's existing district heating supply network and will supply heat for the city centre and Weststadt in future. The fuel used will be wood chips from waste wood and landscape conservation wood. This will replace fossil fuel-fired heating systems in the western and city centre areas. Project manager Jens Hanig (district heating supply employee) estimates that the plant will use around 1,500 tonnes of wood chips from residual wood per year and convert this into heat. With a capacity utilisation of at least 5,500 hours per year, the plant could achieve an annual output of at least 4,700 MWh (megawatt hours) - this corresponds to the heating requirements of around 240 single-family homes.
The woodchippings are transported from the fuel store to the boiler hopper by a fully automatic crane. From here, the fuel is fed into the boiler via two parallel-running screws, where it is burnt. SWG uses the heat from the combustion process to heat water - the hot water is transported to the district heating customers via the pipework system. The flue gases from the combustion process are channelled through a highly efficient, three-stage flue gas cleaning system, which prevents additional fine dust pollution caused by burning wood. During this process, the heat contained in the flue gas is extracted by a flue gas heat exchanger and transferred to the district heating water. The system is therefore operated using condensing technology.
The advantage of supplying heat with wood chips is that residual wood is disposed of in an environmentally friendly manner, a renewable fuel is used and the substitution of fossil fuels means that there is no additional carbon dioxide (CO2) pollution in the air.
Stadtwerke already operates two other wood-fired heating plants in Giessen. The commissioning of this plant brings SWG one step closer to its goal of generating 15 per cent of its district heating with renewable energy sources.