Electricity From Renewable Sources Can Increase With Flexible Systems

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Within 20 years, electricity production in Sweden is to use only renewable sources. One obstacle to this is the fact that the energy flow from solar and wind power is uneven, and depends on the weather. However, research from Linköping University shows that a flexible energy system in which district heating, electricity production, and industry work together to balance energy consumption can contribute to achieving this goal.

The Swedish Energy Policy Agreement passed by the Swedish parliament came into force in 2016, and states that by 2040 Swedish electricity production will use only renewable sources. This will require an expansion of wind power and, to a lesser extent, solar power.

The problem is that wind power does not provide as stable a flow of energy as fossil sources. When it’s windy, the system produces excess energy that must be exported, while the situation is the opposite when it’s calm – electricity must be imported. It is currently possible to control the variation to a certain extent, using hydroelectric power to provide stability. However, if the fraction of wind and solar energy increases, additional methods will be needed to balance the system. This is a challenge, given that the consumers expect a reliable supply of electricity, independent of the weather conditions.

Economic driving force

The problem can be partially solved by reconfiguring to use flexible systems in which district heating, electricity production and industry cooperate. The operation of heat pumps and combined heat and power plants in the district heating system can be controlled such that it helps to balance the electricity system. And industry, which accounts for approximately 37% of total electricity consumption, also has a potential for providing a partial solution.

“Many processes within industry are run at maximum capacity, using the principle of ‘lean production’, which makes it difficult to be flexible. However, these ideas are at the same time the main economic driving force. Reconfiguration would be possible if it were possible to reduce costs by becoming flexible without this having an adverse effect on production,” says Maria Johansson, associate professor in the Department of Management and Engineering (IEI) at Linköping University. 

The researchers have based their work on a scenario in which the amount of wind power increases from the current 28 TWh to 55 TWh, with zero contribution from nuclear energy. In this scenario, Sweden would have to increase its import of electricity by 21 TWh. Export would also increase and would exceed the current capacity of the cables that link Sweden with its neighbours, i.e., we would have excess electricity. A portrait of a women. In the background you can see wind turbines

The researchers used computer simulations to show that by combining all systems such that they work in a flexible manner, the amount of excess electricity could be reduced by 74%, and the required import by 36%. Furthermore, the electricity system would become more stable.

“It’s all about shifting energy consumption to different times. It’s necessary to increase the flexibility of the demand, since it’s more difficult to increase the flexibility of the supply. And then it’s possible to look at energy storage in the district heating system, to a certain extent, but this is a topic for future research,” says Danica Djuric Ilic, associate professor at IEI.

Flexibility markets

The researchers compare the concept with the way in which consumers run their dishwashers and washing machines when the electricity price is lower, as a consequence of a high production of electricity from wind power and a low demand for electricity. This contributes to the peaks of electricity consumption becoming lower when electricity is expensive, i.e. when production from wind power is low and the demand for electricity is high. If the same principle could be introduced into industry, and the electricity consumption better matched to the supply of electricity from wind and solar power, the balance in the electricity system could be improved. This would make it possible to increase the fraction of electricity from renewable sources, but it would require large-scale coordination. The researchers also conducted interviews with energy-supply companies and industrial actors, in order to examine obstacles, drivers, and incentives for user flexibility.

“Industries must analyse their energy consumption to determine which processes can be made more flexible without affecting production. Credible flexibility markets in which flexibility is bought and sold may be one solution. This requires smart systems that control and coordinate the consumption of electricity, and systems that can predict more accurately the electricity produced by wind and solar power plants, which depends, of course, on the weather,” says Maria Johansson.