The project is a small CHP plant at Eskilstuna in Sweden, which uses biomass fuels such as wood. It produces 38MWe and 71MWth. A further 15MW of heat comes from the flue gases. The new plant is designed to replace an oil/peat boiler, which was erected 25 years ago.
The plant was ordered in 1998 and began supplying electricity to the grid in December 2000. It is owned by Eskilstuna Energi och Miljo AB (EEM) and will be used for a combination of electricity generation and district heating. The total plant will cost €67 million. The Swedish Government invested €13 million, and EEM invested €54 million, which they expect to recoup within 7-10 years. Bubbling fluidised-bed units are particularly efficient when firing fuels with low heating value, high moisture and ash content.
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Plant make-up
ABB Power Generation has supplied the plant with its Powerformer HV power generator. ABB Stahl AB will supply the steam turbine. The distinctive feature of the generator is its direct connection to the transmission grid. In the case of Eskilstuna, the Powerformer is being directly linked to a 136kV substation.
The Eskilstuna plant was the first plant ever to be supplied with Alstom’s Powerformer HV generator, although subsequently it has been ordered by Vattenfall at the hydroelectric facility at Porsi, and elsewhere.
Power generator
The Powerformer uses cylindrical windings, as opposed to the standard rectangular ones. This allows it a much higher rated voltage by creating even electric fields. This is a transfer from cable technology.
Claimed advantages for the Powerformer include a claimed greater efficiency of up to 2% more than a conventional system, reduced reactive power losses due to the elimination of the transformer, fewer components, improved availability, lower replacement inventories, more compact plant, easier maintenance thanks to fewer moving parts and a lower environmental impact because of the lower life-cycle cost. ABB estimates that all these advantages may reduce the overall lifetime cost by 30%, with maintenance cut by as much as 10%.
This product is being marketed on grounds of improved reliability and improved performance. The machine at Eskilstuna has a rated voltage of 136kV, a rated capacity of 42MVA, and a rated speed of 3,000rpm. The order is worth $10 million.
Boiler
Kvaerner Power supplied the bubbling fluidised bed boiler and the flue gas cleaning, including condensing scrubber estimated to be worth €15 to €20 million. The boiler will use wood fuel and other biomass. Thanks to its large forestry and sawmill industry, Sweden has an enormous supply of this from the country’s extensive forests. The boiler is designed to minimise polluting emissions. It has a steam capacity of 110MW and a thermal capacity of 192MW.
Alternative energy in Sweden
The Swedish market is a good one for environmentally conscious alternative energy, since there is a strong commitment to renewable energy. This is based on the drive to reduce nuclear generation as a proportion of the overall power mix, without using more fossil fuels. This was a result of a referendum in 1980. The government recognises the difficulties of such a move and is cautious on the issue.
The effort to achieve this may not succeed, but it does give an impetus to the search for alternative energy sources. Both ABB and Kvaerner Power are well-established in the Scandinavian markets, thanks to their extensive local connections.
