Electricity Storage: Energy Ready When the System Needs It

We need electricity at every moment, yet its generation and consumption do not always coincide in time. This is precisely where storage comes into play. It makes it possible to draw energy from the grid at times of surplus, retain it, and return it when the system needs it.

With the growing share of renewable sources, the decentralisation of generation, and higher demands on the flexibility of the electricity system, storage is becoming not only a technological issue but also a significant element of energy security and the resilience of critical infrastructure.

Electricity storage as an essential service

Annex No. 1 to Act No. 367/2024 Coll. classifies electricity storage among the essential services of critical infrastructure as follows:

Sector: Energy

Subsector: Electricity

Category of entities: participants in the electricity market pursuant to a specific regulation

Essential service: electricity storage

Central authority: Ministry of Economy of the Slovak Republic

What does electricity storage actually mean?

Electricity has one specific characteristic – in the electricity system, a balance between its generation and consumption must be maintained practically at all times. Storage relaxes this time constraint to a certain extent.

In practice, it involves drawing electricity from the grid or a device, converting it into a form of energy that can be retained, and subsequently using it at a later time.

This may involve, in particular:

·       battery storage – BESS (Battery Energy Storage Systems),

·       pumped-storage hydroelectric power plants,

·       mechanical systems, for example flywheels or energy storage using compressed air,

·       thermal forms of accumulation,

·       and, prospectively, other long-duration energy storage technologies as well.

Each technology has different parameters, response time, capacity, and the length of time over which it can retain energy. It is precisely the combination of various technologies that may in the future be one of the foundations of flexible and resilient energy systems.

Why is storage so important for the electricity system?

An electricity storage facility is not merely a "big battery." In a modern energy system, it can fulfil several roles simultaneously.

It can absorb surplus electricity, help balance the differences between generation and consumption, provide flexibility, support the stability of the system, reduce the need to curtail generation from renewable sources, and, in certain configurations, help manage outages or local problems in the grid.

Its importance is growing especially with the development of photovoltaic and wind sources. After all, the sun does not generate according to instantaneous consumption, and the wind does not blow according to the needs of the electricity system.

We therefore need to move energy generated at times of surplus into periods when there is a shortage of it. Storage thus creates a time bridge between the generation and consumption of electricity.

The numbers show how big a change awaits us

The development of European energy shows that the importance of flexibility and storage will grow rapidly. According to European Commission data, renewable sources accounted for approximately 47% of electricity generation in the EU in 2024. By 2030, their share is estimated at approximately 69%, and by 2050 at up to 80%. Along with this, the need for flexibility in the electricity system is also growing. In 2030, it should reach approximately 288 TWh, which represents around 24% of total electricity demand in the EU.

The storage market itself is therefore changing rapidly. At the beginning of 2026, the European Union had approximately 55 GW of energy storage capacity, whereby, according to the European Commission, this capacity will need to be increased to approximately 200 GW by 2030.

The global trend is even more pronounced. According to the International Energy Agency, approximately 108 GW of new battery capacity was commissioned worldwide in 2025, which represented a year-on-year increase of approximately 40%. Approximately four fifths of the new capacity consisted of utility-scale storage.

Battery storage has thus become the fastest-growing technology in the electricity sector. This demonstrates a fundamental change: storage facilities are gradually shifting from being a supplement to the electricity system to becoming one of its strategic components.

New technology also brings new risks The greater the importance storage has for the stability of the electricity system, the more important it will be to protect the storage facilities themselves and the systems that control them.

Technological and fire risks

Especially with large battery systems, it is necessary to account for the risk of cell failure, overheating, short circuits, or so-called thermal runaway – an uncontrolled thermal process that can lead to a fire and its spread between individual cells. Safety must therefore be addressed already at the design stage of the device – from monitoring the temperature and state of the batteries, through fire protection, to the physical arrangement of the individual parts of the system.

Cyber risks

A modern battery storage facility is also a digitally controlled energy device.

The Battery Management System (BMS), Energy Management System (EMS), communication interfaces, remote management, and connection to trading and dispatch systems create a digital environment that may be the target of a cyberattack.

Compromising the control of a storage facility may mean its shutdown, incorrect charging or discharging, manipulation of operational data, or disruption of the services provided to the electricity system.

Physical and cyber security therefore cannot be assessed separately in the case of energy storage facilities.

Dependence on supply chains

Battery technologies are also closely intertwined with global supply chains.

The manufacture and operation of storage facilities depend on the availability of critical raw materials and components, production capacities, power electronics, software, and specialised service. The concentration of the production or processing of certain components in a limited number of countries may create strategic dependencies.

The risk therefore need not be only the failure of the device itself, but also a situation in which it is not possible to secure a replacement component, service, or an update of the control system within a reasonable time.

Physical and environmental risks

Utility-scale storage facilities are physical energy infrastructure, and therefore they must also account for vandalism, sabotage, extreme temperatures, floods, fire, storms, or other natural phenomena.

For critical infrastructure, it is therefore not enough to ask:
"How will we prevent a failure?"

Equally important is the question:
"What will we do when a failure or attack occurs despite all measures?"

It is precisely the ability to continue providing the essential service and to restore its full-fledged provision as quickly as possible that is the essence of the resilience of critical infrastructure.

Storage changes the logic of the energy sector

Traditional electricity supply was based primarily on the principle that generation must respond to consumption at every moment.

Storage facilities bring another option into the system: part of the energy can be shifted in time.

This fundamentally changes the possibilities for managing the system. Surplus energy from photovoltaics generated during the day can be used in the evening. A battery can respond to the needs of the system within a very short time. Storage facilities can cooperate with generation, consumption, aggregation, and demand management, and create complex flexible solutions.

The boundaries between producer, consumer, and provider of flexibility are thereby gradually blurring. And that is precisely why the view of critical infrastructure is also changing. It is not enough to protect power plants, substations, and transmission lines. Attention must also be extended to storage facilities, data and communication systems, software, supply chains, and control technologies, on which the functioning of the energy sector will increasingly depend.

The role of the Critical Infrastructure Association of the Slovak Republic in electricity storage

With the growing importance of electricity storage, the nature of the risks that need to be monitored in the electricity sector is also changing. Utility-scale storage facilities interconnect energy technologies, power electronics, digital control, communication systems, and global supply chains. Their security therefore cannot be assessed merely as a technical issue.

The Critical Infrastructure Association of the Slovak Republic can support, in this area, a comprehensive assessment of the risks associated with the operation of electricity storage systems – from physical and fire safety, through the cyber protection of control systems, to dependence on technology manufacturers, spare parts, software, and service capacities.

Particular attention is warranted especially in the case of battery storage (BESS), in which energy and cyber security are directly interconnected. The Battery Management System and the Energy Management System determine the safe and efficient operation of a storage facility, and their disruption can affect not only the device itself but, in the case of significant capacities, also the services provided to the electricity system.

An important topic is at the same time the resilience of the supply chain. In the case of storage facilities, it is necessary to monitor the availability of battery cells and other key components, power electronics, control technologies, spare parts, and professional service. The failure of a strategic supplier or the long-term unavailability of a critical component may significantly extend the time needed to restore the device.

The Association can therefore create an expert platform for sharing experience among operators of energy infrastructure, technology companies, security experts, academia, and public administration, identify new risks associated with the development of storage facilities, and support the preparation of continuity and recovery scenarios for this essential service.

With the growing role of accumulation in the electricity sector, it will indeed become increasingly important not only to build new capacities, but also to know which technologies and suppliers they depend on, what threats they face, and how quickly we are able to restore their function in the event of a serious incident.

Energy we have stored has value only when it is available

The development of electricity storage will be one of the significant changes that the electricity sector will undergo in the coming years. The more, however, the electricity system depends on storage facilities, the more important their reliability, security, and ability to withstand incidents will be.

For critical infrastructure, therefore, it will not be decisive only how much energy we are able to store. What will also be decisive is whether we are able to use it safely and reliably precisely at the moment when we need it most. And it is precisely then that a piece of technological equipment becomes part of the resilience of the entire energy infrastructure.



In the next part of the series on essential services, we will remain in the energy sector, but move into the area of nuclear energy. We will look at the essential services whose safe and reliable provision is an inseparable part of the functioning of the critical infrastructure of the Slovak Republic.