Energy storage facilities: A key component of the energy transition. Part 1

Energy storage facilities play a fundamental role in managing electricity flows. Their main function is to store excess energy produced during periods of lower demand and release it at times of peak consumption. Essentially, these systems operate on a similar principle to batteries used in electronic devices, but are scaled for industrial needs. They allow better use of renewable energy sources that do not always provide energy continuously (e.g., at night for solar power or during windless periods for wind power).

From a technology point of view, energy storage facilities vary in both performance and application. We can divide them into several main categories.

• Pumped storage power plants - The largest and oldest energy storage systems. They operate by pumping water into a higher reservoir during times of energy surplus, and then generating energy by flowing this water through turbines when needed. These systems have a large capacity, but require specific geographic conditions.
• Compressed air storage (CAES) - Energy is stored by compressing air in underground caverns. During times of demand, the air is expanded and drives turbines. CAES have long storage times, but their efficiency is lower than other technologies.
• Flywheels - Energy is stored as kinetic energy in a rotating flywheel. When the demand for energy increases, the kinetic energy is converted into electrical energy. Flywheels have a very high power density, making them ideal for short-term stabilization operations.
• Electrochemical batteries - The most popular solution in energy storage. Lithium-ion batteries are the most common, although there are other technologies such as lead-acid or flow batteries. These systems have high efficiency and are increasingly used for grid stabilization and in the renewable energy sector.
• Thermal storage - Energy is stored in the form of heat, which can be used in a variety of applications, such as heating buildings or cooling with water or ice. Such systems can be effective in the context of heating, but their use in electricity is limited.

From a technical point of view, energy storage facilities are characterized by several basic parameters that determine their efficiency and application in various sectors.

• Storage capacity - Determines how much energy a given system can store and is expressed in kilowatt-hours (kWh) or megawatt-hours (MWh). Capacity depends on the power of the system and the length of time it can supply energy. For example, a 50 MW storage system that can operate for 4 hours has a capacity of 200 MWh. However, this does not mean that such a system must always operate at full capacity. If a load of 25 MW is required, the system can store energy for a longer time (200MWh / 25 MW = 8 h)
• Energy density - Refers to the ratio of stored energy to storage mass or volume. The higher the energy density, the smaller the space occupied by storage of the same capacity. For example, lithium-ion batteries have an energy density of 150-265 Wh/kg, making them attractive for mobile applications such as smartphones and electric cars.
• Power density - Indicates how quickly a given system can release energy. This is especially important in situations where quick responses are needed, such as in grid stabilization. Power density is measured in W/kg or W/liter and is a key factor in industrial applications.

• Efficiency (cycle efficiency) - Determines how much of the input energy (storage charge) can be recovered after it is released from storage. It is measured as a percentage and depends on the technology. For example, lithium-ion batteries have efficiencies of 85-95%, while other technologies, such as CAES, may have lower efficiencies.

• Storage time - This is a parameter that determines how long a system can store energy. Some technologies, like flywheels, are ideal for short-term applications (seconds or minutes), while pumped storage plants can store energy for days or even weeks

When designing energy storage, such as large-scale energy storage, the aspect of space will be very important. Batteries with higher energy density will simply take up less of it. Pumped storage power plants, for example, require very large amounts of water and massive reservoirs to do their job on a large scale.

Global investment in energy storage has increased significantly over the past few years, driven by the growing share of renewables and the ongoing decarbonization of energy systems. In 2023, the global installed capacity of energy storage systems exceeded 50 GW, a significant jump compared to previous years.

The largest energy storage facilities are in the United States, China and Europe, although countries such as Australia and India are also rapidly developing their storage systems. In the U.S., the largest energy storage facilities are located in California and are mainly used to stabilize the solar-based grid. China, on the other hand, is developing huge storage systems as part of its strategy to increase the share of RES, especially in the context of its growing wind power industry.

Europe has also been at the forefront of developing energy storage technologies, driven by ambitious climate goals and a drive to decarbonize the economies of European Union member states. In 2023, installed energy storage capacity in Europe was about 15 GW, with Germany, the United Kingdom, Spain and Italy accounting for the largest shares.

• Germany: the leader in Europe in terms of installed energy storage capacity, mainly due to the development of lithium-ion battery technology and pumped storage power plants. Germany has also introduced numerous support programs for the installation of home energy storage systems, encouraging the development of distributed energy storage.
• United Kingdom: The country is betting on the development of energy storage to stabilize a grid that relies heavily on wind power. The largest installations are in Scotland and on the coasts, where offshore wind farms are located.
• Spain and Italy: These countries are rapidly developing energy storage due to the large share of solar energy. Spain, in particular, has invested in large-scale storage installations for industrial use, thanks to its abundant sunshine.

Energy storage is a key component of a future electricity system based on renewable sources. As technology advances, it is expected that storage capacity will continue to increase and installation costs will decrease. New technologies such as flow batteries, supercapacitors and superconducting energy storage could revolutionize the market in the coming decades.

In my next article on energy storage, I will answer the questions: 

• How much do energy storage units cost? 
• How many of them are needed to meet the needs of business consumers?
• What are the plans for the development of energy storage?