Stabilising the grid with flexibility pools

The rapid expansion of solar energy poses challenges. Production is volatile and forecasts challenging. To keep grid frequency in balance, power must be fed in or removed within seconds. To that end, the Axpo Group operates flexibility pools, in which even church heating systems and emergency generators become small but important parts of the energy transition.

Photovoltaic capacity in Switzerland has more than doubled during the past five years. This  development also brings challenges, however, as the production of solar energy is volatile. When the sun shines, a lot of energy is generated. But as soon as clouds appear, production suddenly collapses. Volatility in itself would not be a problem, but smaller energy suppliers in particular do not have the capabilities and resources to reliably forecast production from solar plants at all times. 

For the electricity system to remain stable, production and consumption must always remain in balance. Even small deviations from the standard grid frequency of 50 hertz (Hz) can lead to outages. To prevent this, systems are needed that can feed electricity into the grid or draw it from the grid within seconds.

Flexibility and a secure energy supply

The national grid company Swissgrid is responsible for the stability of Switzerland’s transmission system. To keep the electricity grid stable, it procures balancing power and balancing energy from specialist suppliers. Balancing power means that systems are ready to react immediately when necessary. If this power is actually called up, it is referred to as balancing energy. Swissgrid procures around one gigawatt (GW) of this flexibility in both directions, roughly equivalent to the output of the Gösgen nuclear power plant.

Axpo’s virtual power plants

Axpo is one of the leading providers of such services in Switzerland. To be able to react at short notice, Axpo operates several flexibility pools in addition to its own power plants. These pools bundle a wide range of systems into a virtual power plant. They include hydropower facilities, batteries, waste recycling and industrial plants, electric cars, emergency generators and even church heating systems.

Axpo’s flexibility pools currently number around 1,700 systems from 15 technologies with a total output of more than 1.4 GW. That is more than the output of the Leibstadt nuclear power plant. The operators of these systems receive a share of the proceeds. For them, participating in a flexibility pool can be an important additional source of income, creating an incentive to invest in renewable energies and flexible energy solutions.

Contributing to a stable energy system

Pooling is key to a secure and efficient energy supply. The bundling of many small and medium-sized systems strengthens the stability of the Swiss electricity grid, improves the efficiency of electricity markets, and makes it easier to integrate renewable energies. With its flexibility pools, Axpo is laying the foundations for a reliable electricity supply, even in an increasingly decentralised system.