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Power plants stockpile energy in the summer for the coming winter


The everyday life of power plants changes with the seasons. In spring and summer as the need for heating subsides when outdoor temperatures rise. From the outside it might seem like little is happening at power plants in the summer, but nothing could be further from the truth. We asked our experts how the seasons affect power plant operations, how less demand for fuel is reflected in sourcing fuel and what impacts are seen in the circular economy.

“As demand for district heat subsides in the spring, we adjust heat production in line with needs and generally in March-April, we run down the Toppila power plant to wait for summer maintenance and then re-start it in the autumn,” says Mikko Vesterinen, Production Director. Even though things quieten down at Toppila for the summer, the same can’t be said of Oulun Energia’s Laanila biopower plant, where production continues throughout the summer and provides any district heat capacity needed in Oulu. In the best-case scenario, district heat during the late spring and summer can be produced using just biofuels and solid recovered fuel (SRF) without peat.

Oulun Energia’s Laanila ecopower plant also basically operates all year round, apart from a couple of inspections. “Since the plant generally operates continuously at full capacity, the changing seasons don’t really affect the plant and fuel for it is steadily stockpiled,” Vesterinen says.

Even though operations at the other power plants can’t necessarily be seen from the outside, residents of Oulu can see the work at the Merikoski power plant in the spring and summer. “Peak flow rates from floods usually occur in the spring and may be so great at times that we have to run the water past the turbines and into the flood channel, where people notice it,” Vesterinen says. As spring progresses, work at the Merikoski power plant also heralds the arrival of summer. “A sure sign of summer is the opening of the Merikoski  fish pass and the installation of the pumps to work the fountains in the ornamental pools,” Mikko laughs.


Frost heave and restocking

On the fuel front, the arrival of spring and summer is reflected in lower fuel consumption and depletion of stocks when the remaining fuel stocks stored in the plants’ yards are used up. After this, stocks will start to build up once delivery volumes exceed the amount used. Spring presents its own problems as far as sourcing is concerned.

“Spring brings with it frost heave, which challenges deliveries of wood chippings and most of the forest fractions are supplied from along load-bearing road links. Once the frost heave eases, supplies continue from alongside forest roads,” says Lauri Heilala, Director, Fuel Sourcing. Heilala says that the beginning of summer is marked by pine weevils buzzing around. The weevils are attracted to the power plants by sawdust supplied by local sawmills which is stored in the yards. “At times in the spring, summer and early autumn, we’re also “abuzz” as we get ready for the coming winter and needs of the heating season,” Heilala smiles.

Summer bustle in the circular economy

The arrival of spring and summer means a busy time for our circular economy company Syklo. “There’s more waste in the summer because of brisk construction and renovation activity – this also means that in some places that more SRF is produced than can be used in power production,” says Teemu Koskela, Managing Director of Syklo. Like elsewhere, Syklo spends the summer getting ready for the winter. Stocks accumulated in the simmer are important in the winter, when there is less waste available even though recycled fuel consumption is high. “Despite the hustle and bustle of summer or the sharp winter frosts, we at Syklo are in good spirits throughout the year,” Koskela laughs.