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Töreboda – home to glulam and VänerEnergi

VänerEnergi AB is one of a growing number of Swedish district heat companies retrofitting boilers with an Organic Rankine Cycle (ORC) turbine to become combined heat and power (CHP) plants producing electricity for self-consumption and/or the local grid. Commissioned in 2019, it was an auspicious year for Töreboda, glulam, and VänerEnergi.

VänerEnergi’s Töreboda district heating plant seen from the entrance to the Moelven Töreboda industrial estate. The multi-coloured buffer tank has a volume of 850 m3.

Founded in 1989 and jointly owned by the municipalities of Mariestad and Töreboda, VänerEnergi AB is in many ways a typical municipal district heating company that seeks to adapt and evolve to provide local, low-cost and eco-friendly heat to its citizens. The company owns and operates biomass-fired district heating operations in the towns of Mariestad, Töreboda, and Lyrestad.

In Mariestad, the largest of the three towns (population c. 16 600), heat is produced by Katrinefors Kraftvärme AB (KKAB), a combined heat and power (CHP) plant developed in 2002 and jointly owned by Metsä Tissue AB that operates the Katrinefors tissue mill in Mariestad, and VänerEnergi.

Consisting of two biomass-fired co-generation units with flue gas condensing, KKAB supplies steam, district heat, and electricity using forestry residues, woodchips, and fibre sludge from the tissue mill as fuel. In addition, residual heat from the wastewater treatment plant (WWTP) is recovered for the heat network.

History in the making

In the town of Töreboda (population c. 4 600), VänerEnergi’s plant was originally built as a heat-only plant. That changed in mid-2018 when the company decided that it would invest around SEK 1.8 million (≈ EUR 176 000) to install a 50kW ORC turbine from Againity AB.

This is a good investment for the environment. One of the major advantages of being able to produce electricity while producing heat is that electricity is produced when we need it the most, that is, during the winter. Furthermore, both fuel efficiency and total plant efficiency are improved. So as far as we are concerned, there was really no reason not to make the investment, said Kjell-Åke Wallström, District Heating Manager for VänerEnergi.

The Töreboda heat plant is located on the outskirts of the town on a site owned by and adjacent to a wood processing plant operated by Moelven Töreboda AB. Part of the Norway-headed solid wood processing group Moelven Industrier ASA, Moelven Töreboda produces glue-laminated (glulam) timber structures for construction, as evidenced in the heating plant building itself.

The Töreboda district heating plant building uses glulam in its structure and timber cladding on the facade.

As a “by the way”, the visible ceiling beams in Stockholm Central train station main hall also came from the Töreboda glulam plant. Spanning 24 metres, the arched glulam beams were made and installed during 1925 – 1928. The glulam plant itself was established in 1918 and operational in 1919, which by some accounts, makes it the world’s oldest operational glulam facility.

Briquette producer

Commissioned in 2011, VänerEnergi’s Töreboda heat plant consists of two hot water boilers, a primary baseload 4 MWth boiler that operates year-round, and a secondary seasonal load 4 MWth boiler that comes online during the heating season. In addition, there is an 11 MWth oil-fired back-up boiler that uses bio-oil.

The entire heat plant, including ancillaries such as storage silos, hot water buffer tank, conveyors, ash removal, and flue gas filters were supplied by the Danish company Weiss ApS, now part of compatriot Linka Energy A/S.

The woodchip infeed to the secondary 4 MWth boiler and a glimpse (bottom right) of the 11 MWth bio-oil prepped back-up boiler. All three boilers and ancillaries were supplied by Weiss.

The primary load 4 MW boiler uses dry wood shavings and sawdust from Moelven’s production process. This is supplied directly to a storage silo from where it is fed to the boiler.

Since the supply from Moelven exceeds the boiler demand, the excess volume of shavings and sawdust is briquetted and stored onsite by VänerEnergi.

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