Energy storage in the power system

What are energy storage systems?

According to the definition in the Energy Law Act, an energy storage system is an installation that allows the storage of electrical energy and its injection into the power grid. The storage process involves converting electrical energy into another form, storing it, and then reconverting it back into electrical energy.

The primary purpose of energy storage is to balance supply and demand for electricity. In practice, this means storing surplus energy during periods of low demand or high RES production to use it during peak demand or when renewable energy production is insufficient. The ability to “shift” energy over time is crucial for maintaining the stability of the entire power system.

Energy storage systems benefit both energy producers and consumers. Producers can optimize energy sales by storing it during periods of low prices and selling it when prices are higher. End-users can minimize costs by storing energy during cheaper tariff periods and using it during more expensive ones.

Energy storage technologies

As the energy transition progresses, various energy storage technologies are evolving. They can be categorized into three main groups: mechanical, electrochemical, and chemical storage systems.

Among mechanical storage systems, pumped hydro storage (PHS) is the most widespread. These “giant batteries” use gravity to store energy by pumping water to a higher elevation when energy is cheap and releasing it through turbines when energy demand increases. PHS systems are characterized by high efficiency and low failure rates, making them strategic assets for the stability of national energy systems. Other mechanical solutions, such as compressed air energy storage (CAES) or liquid air energy storage (LAES), also offer opportunities for large-scale energy storage.

In the category of electrochemical storage, lithium-ion batteries dominate, known for their use in consumer electronics and electric vehicles. Their popularity in the energy sector is growing due to high energy density and declining costs. Flow batteries, particularly those using vanadium technology, are gaining traction thanks to their ability to simultaneously charge and discharge and their long lifespan.

Hydrogen-based technologies present a promising alternative for long-term energy storage. Hydrogen produced through water electrolysis using excess energy from RES can be stored and later used to generate electricity in fuel cells.

The role of energy storage in the energy transition

Energy storage systems play a critical role in integrating renewable energy sources into the power system. They support grid stability by mitigating the effects of variability in RES production and helping maintain the quality parameters of electrical energy. In practice, this means that even when the sun isn’t shining or the wind isn’t blowing, the power system can rely on previously stored energy to ensure continuity of supply.

Energy storage systems contribute to optimizing the use of energy infrastructure. They reduce the need for investments in additional generation capacity, which would otherwise be used only during peak demand periods. Instead, existing resources can be used more efficiently, translating to lower costs for the entire energy system.

What else should you know about energy storage systems?

The future of energy storage technology looks promising but is not without challenges. Key areas of development include increasing storage capacity, improving lifespan, and reducing costs. Intensive research is being conducted into new materials for battery production, more efficient methods of hydrogen electrolysis, and innovative concepts for mechanical energy storage. One of the most exciting directions for development is the implementation of smart grids that integrate advanced energy management systems with distributed energy storage. These solutions can enhance the flexibility and resilience of the power system while optimizing the use of renewable energy sources.

In Poland, where the energy sector is undergoing significant transformation, investing in the energy transition, including the development of energy storage systems, is becoming a vital component of the national energy strategy.