Frequency Stabilization with the Help of C&I Energy Storage Systems
The energy transition is bringing fundamental changes to the power supply. With the increasing share of renewable energies such as wind and solar power, grid stability is facing new challenges. Frequency stabilization, in particular, is gaining importance in this context. Commercial & Industrial (C&I) energy storage systems are developing into a key instrument for maintaining grid stability.
Fundamentals of Frequency Stabilization
The grid frequency is a critical parameter in every power grid. In Europe, the standard frequency is 50 hertz and may only fluctuate within very narrow limits – typically between 49.8 and 50.2 hertz. A balance between power generation and consumption is essential for frequency stability. If generation exceeds consumption, the frequency increases. If consumption exceeds generation, the frequency decreases.
In conventional power grids, frequency stabilization was primarily ensured by large power plants with rotating masses (synchronous generators). Due to their inertia, these provide natural damping against frequency changes. With the decline of these conventional generators and the rise of volatile renewable energies, a gap in the system's inertia is emerging, requiring new solutions.
The Role of C&I Energy Storage Systems
C&I energy storage systems represent an ideal technology for frequency stabilization. Unlike conventional power plants, they can respond to frequency fluctuations almost instantly – within milliseconds instead of seconds or minutes. This response speed makes them particularly valuable for primary control power (PCP), the first line of defense against frequency deviations.
Modern C&I battery storage systems have capacities ranging from several hundred kilowatts to several megawatts and are specifically designed for industrial applications. They are characterized by high cycle stability, precise control technology, and robust construction. This enables them to handle thousands of charge and discharge cycles per year for frequency regulation services without significant degradation.
Technical Functionality of Frequency Regulation
Frequency regulation with C&I storage systems is based on continuous monitoring of the grid frequency. Special measuring devices record the current grid frequency with high accuracy, typically with a resolution of 0.001 Hz or better. Based on these measurements, the battery system reacts according to the predefined control curves.
At underfrequency (below 50 Hz), the battery systems discharge energy into the grid, which corresponds to an additional power plant and stabilizes the frequency. At overfrequency (above 50 Hz), however, they absorb excess energy, which acts like an additional load and lowers the frequency. This symmetrical control is proportional to the frequency deviation – the greater the deviation from the setpoint, the stronger the response of the storage system.
A key advantage of battery storage systems is their bidirectional nature: They can both output and absorb power. Conventional power plants, on the other hand, can only provide additional power or reduce their output, which limits their flexibility and leads to increased wear and tear due to frequent load changes.
Frequency stabilization with the help of C&I energy storage systems
The energy transition is bringing fundamental changes to the power supply. With the increasing share of renewable energies such as wind and solar power, grid stability is facing new challenges. Frequency stabilization, in particular, is gaining importance in this context. Commercial & Industrial (C&I) energy storage systems are developing into a key instrument for maintaining grid stability.
Fundamentals of Frequency Stabilization
The grid frequency is a critical parameter in every power grid. In Europe, the standard frequency is 50 hertz and may only fluctuate within very narrow limits – typically between 49.8 and 50.2 hertz. A balance between power generation and consumption is essential for frequency stability. If generation exceeds consumption, the frequency increases. If consumption exceeds generation, the frequency decreases.
In conventional power grids, frequency stabilization was primarily ensured by large power plants with rotating masses (synchronous generators). Due to their inertia, these provide natural damping against frequency changes. With the decline of these conventional generators and the rise of volatile renewable energies, a gap in the system's inertia is emerging, requiring new solutions.
The Role of C&I Energy Storage Systems
C&I energy storage systems represent an ideal technology for frequency stabilization. Unlike conventional power plants, they can respond to frequency fluctuations almost instantly – within milliseconds instead of seconds or minutes. This response speed makes them particularly valuable for primary control power (PCP), the first line of defense against frequency deviations.
Modern C&I battery storage systems have capacities ranging from several hundred kilowatts to several megawatts and are specifically designed for industrial applications. They are characterized by high cycle stability, precise control technology, and robust construction. This enables them to handle thousands of charge and discharge cycles per year for frequency regulation services without significant degradation.
Technical Functionality of Frequency Regulation
Frequency regulation with C&I storage systems is based on continuous monitoring of the grid frequency. Special measuring devices record the current grid frequency with high accuracy, typically with a resolution of 0.001 Hz or better. Based on these measurements, the battery system reacts according to predefined control curves.
At underfrequency (below 50 Hz), the battery systems discharge energy into the grid, which corresponds to an additional power plant and stabilizes the frequency. At overfrequency (above 50 Hz), however, they absorb excess energy, which acts like an additional load and lowers the frequency. This symmetrical control is proportional to the frequency deviation – the greater the deviation from the target value, the stronger the response of the storage system.
A key advantage of battery storage systems is their bidirectional nature: They can both supply and absorb power. Conventional power plants, on the other hand, can only provide additional power or reduce their output, which limits their flexibility and leads to increased wear and tear due to frequent load changes.
Primary Control Reserve and Other System Services
Primary control reserve (PRL), also known as frequency containment reserve (FCR), is the most important frequency regulation service for battery storage systems. It is activated automatically and must be fully available within 30 seconds. Payment is based on the capacity retained, typically in euros per megawatt per hour.
In addition to primary control reserve, C&I storage systems can also provide other system services. Secondary control reserve (SRL) or automatic frequency restoration reserve (aFRR) is activated after primary control reserve and is intended to replace it. The minute reserve (MRL) or manual frequency restoration reserve (mFRR) ultimately follows the secondary control power and serves to restore the system's balance in the long term.
In addition, high-performance battery storage systems can also contribute to voltage stability by providing reactive power. In local grids, they can also serve as a black start capability to restart the grid after a blackout. a capability that is becoming increasingly important with the decline of conventional power plants.
Economic Aspects of Frequency Stabilization
The provision of system services, especially primary control power, represents an attractive business case for operators of C&I storage systems. Remuneration rates vary depending on the market situation and regulatory environment, but typically range between €100,000 and €200,000 per year per megawatt for primary control power.
In fact, participation in the control power market was one of the first economically viable business models for large-scale battery storage systems, before other applications such as peak shaving or self-consumption optimization became commercially viable. Today, many operators rely on multi-use concepts in which the storage is used for both frequency stabilization and other applications, which significantly improves economic efficiency.
The investment costs for C&I storage systems have fallen significantly in recent years. While prices of over 1,000 euros per kilowatt hour were common in 2015, they now range from 400-700 euros per kilowatt hour for turnkey systems. At the same time, the technical requirements for control power providers have increased, requiring high-quality and precise systems.
Technical components of a frequency-stabilizing storage system
A C&I storage system for frequency stabilization consists of several core components. The core of the system is the battery modules, usually based on lithium-ion technology. These are monitored by a battery management system (BMS), which ensures safe operation and optimal use of the individual cells.
The power electronics, consisting of inverters and DC/DC converters, enable energy exchange with the grid and precise control of power flows. High-precision measuring devices that continuously record the grid frequency are particularly important for frequency regulation. These are often designed redundantly to ensure maximum availability.
The higher-level energy management system (EMS) coordinates all components and communicates with the grid operator or the control power market. It implements the control strategies and ensures compliance with technical requirements. Many modern systems also use predictive algorithms to optimally manage the battery's charge level and thus maximize the availability of control power.
Practical Example: Industrial Battery Storage for Frequency Regulation
A typical example of a frequency regulation project is a 10 MW/10 MWh battery storage system installed at an industrial site. The system consists of 40 battery containers, each with a capacity of 250 kW, and is connected to the medium-voltage grid via its own substation.
The system's main source of income is the provision of primary control power with a continuous availability of 99.5%. By combining it with local applications such as peak load management for industrial operations, the system's economic efficiency has been significantly increased. The investment of approximately €7 million will pay for itself within seven years.
The system's high precision is particularly remarkable: It reacts to frequency deviations within 200 milliseconds and reaches full power in less than one second. This significantly exceeds the requirements of grid operators and effectively contributes to grid stabilization.
Primary Control Reserve and Other System Services
Primary control reserve (PRL), also known as frequency containment reserve (FCR), is the most important frequency regulation service for battery storage systems. It is activated automatically and must be fully available within 30 seconds. Payment is based on the capacity retained, typically in euros per megawatt per hour.
In addition to primary control reserve, C&I storage systems can also provide other system services. Secondary control reserve (SRL) or automatic frequency restoration reserve (aFRR) is activated after primary control reserve and is intended to replace it. The minute reserve (MRL) or manual frequency restoration reserve (mFRR) ultimately follows the secondary control power and serves to restore the system's balance in the long term.
In addition, high-performance battery storage systems can also contribute to voltage stability by providing reactive power. In local grids, they can also serve as a black start capability to restart the grid after a blackout. a capability that is becoming increasingly important with the decline of conventional power plants.
Economic Aspects of Frequency Stabilization
The provision of system services, especially primary control power, represents an attractive business case for operators of C&I storage systems. Remuneration rates vary depending on the market situation and regulatory environment, but are typically between €100,000 and €200,000 per year per megawatt for primary control power.
In fact, participation in the control power market was one of the first economically viable business models for large-scale battery storage, before other applications such as peak shaving or Self-consumption optimization became economically viable. Today, many operators rely on multi-use concepts in which the storage is used for both frequency stabilization and other applications, which significantly improves economic efficiency.
The investment costs for C&I storage systems have fallen significantly in recent years. While prices of over €1,000 per kilowatt hour were common in 2015, they now range between €400 and €700 per kilowatt hour for turnkey systems. At the same time, the technical requirements for control power providers have increased, requiring high-quality and precise systems.
Technical components of a frequency-stabilizing storage system
A C&I storage system for frequency stabilization consists of several core components. The heart of the system is the battery modules, usually based on lithium-ion technology. These are monitored by a battery management system (BMS), which ensures safe operation and optimal use of the individual cells.
The power electronics, consisting of inverters and DC/DC converters, enable energy exchange with the grid and precise control of power flows. High-precision measuring devices that continuously measure the grid frequency are particularly important for frequency regulation. These are often designed redundantly to ensure maximum availability.
The higher-level energy management system (EMS) coordinates all components and communicates with the grid operator or the control power market. It implements the control strategies and ensures compliance with technical requirements. Many modern systems also use predictive algorithms to optimally manage the battery state of charge and thus maximize the availability of control power.
Practical example: Industrial battery storage for frequency regulation
A typical example of a frequency regulation project is a 10 MW / 10 MWh battery storage system installed at an industrial site. The system consists of 40 battery containers, each with a capacity of 250 kW, and is connected to the medium-voltage grid via its own substation.
The system's main source of income is the provision of primary control power with a continuous availability of 99.5%. By combining it with local applications such as peak load management for industrial operations, the system's economic efficiency has been significantly increased. The investment of approximately €7 million will pay for itself within seven years.
The system's high precision is particularly remarkable: In the event of frequency deviations, it reacts within 200 milliseconds and reaches full power in less than one second. This significantly exceeds the requirements of the grid operators and effectively contributes to grid stabilization.
Challenges and Development Prospects
Despite the many advantages, C&I storage systems for frequency stabilization face several challenges. One of these is the increasing market saturation and the associated price pressure on control power products. With more suppliers, prices are falling, which can affect the economic viability of individual projects. At the same time, technical requirements are continually becoming more stringent, requiring greater investment in measurement and control technology.
A further challenge lies in battery aging due to the frequent charging and discharging cycles during frequency regulation. While modern battery chemistries and intelligent operating strategies can minimize this aging, a certain degree of degradation remains unavoidable. Advanced energy management systems therefore attempt to optimize battery load by avoiding particularly deep charge and discharge cycles.
Several promising developments are emerging for the future. Hybrid systems that combine different storage technologies are increasingly being used – for example, lithium-ion batteries for fast response times with redox flow batteries for longer discharge times. Combining them with flywheel energy storage or supercapacitors can also improve system performance.
Regulatory Framework and Market Development
The regulatory framework for frequency stabilization services is constantly evolving. In Europe, the market for primary control power has become increasingly harmonized and internationalized in recent years. Since 2019, there has been a common market for FCR in several European countries, which has increased liquidity and stabilized market prices.
At the same time, tender periods have been shortened – from weekly to daily, and in some markets even to hourly auctions. This allows for more flexible marketing and better integration with other applications. The products themselves have also been diversified, with different quality levels and response times.
Further refinement of market products is expected in the future, with possible separate rewards for particularly fast responses or other quality characteristics. The role of aggregators, which combine many smaller storage units into a virtual power plant, will also increase.
Significance for the Energy Transition
Frequency stabilization through C&I energy storage systems plays a crucial role in the success of the energy transition. With the continued expansion of fluctuating renewable energies and the decline of conventional power plants, the need for flexible, rapidly responding control power providers will continue to grow.
Battery storage systems can effectively fill this gap and help ensure a stable grid with a high proportion of renewable energies. They not only replace the lost control power of conventional power plants, but their faster response even improves the quality of frequency regulation. This contributes to safer and more stable grid operation and ultimately enables a higher share of renewable energy.
In the long term, C&I storage systems, together with other flexible resources such as demand response and power-to-X technologies, could enable a fully renewable energy system that does not require fossil backup power plants. This would make a decisive contribution to the decarbonization of the energy sector.
Conclusion
C&I energy storage systems have established themselves as a valuable tool for frequency stabilization. Their ability to respond to frequency changes in milliseconds makes them ideal providers of primary control power and other system services. Due to the falling costs of battery technology and the increasing need for flexible control power in the wake of the energy transition, their importance will continue to grow.
The greatest advantages of C&I storage systems for frequency stabilization are their fast response time, bidirectional performance, and high precision. Multi-use concepts, in which frequency regulation is combined with other applications such as peak load management or self-consumption optimization, can also significantly improve the economic efficiency of the systems.
In the future, battery storage systems are expected to play a central role in grid stabilization. With advancing technological development, falling costs, and improved regulatory frameworks, they will become an indispensable component of a stable, renewable energy system.
Challenges and Development Prospects
Despite the many advantages, C&I storage systems for frequency stabilization face several challenges. One of these is the increasing market saturation and the associated price pressure on control power products. With more suppliers, prices fall, which can affect the economic viability of individual projects. At the same time, technical requirements are continually becoming more stringent, requiring greater investment in measurement and control technology.
A further challenge lies in battery aging due to the frequent charging and discharging cycles during frequency regulation. While modern battery chemistries and intelligent operating strategies can minimize this aging, a certain degree of degradation remains unavoidable. Advanced energy management systems therefore attempt to optimize battery load by avoiding particularly deep charge and discharge cycles.
Several promising developments are emerging for the future. Hybrid systems that combine different storage technologies are increasingly being used – for example, lithium-ion batteries for fast response times with redox flow batteries for longer discharge times. Combining them with flywheel energy storage or supercapacitors can also improve system performance.
Regulatory Framework and Market Development
The regulatory framework for frequency stabilization services is constantly evolving. In Europe, the market for primary control power has become increasingly harmonized and internationalized in recent years. Since 2019, there has been a common market for FCR in several European countries, which has increased liquidity and stabilized market prices.
At the same time, tender periods have been shortened – from weekly to daily, and in some markets even to hourly auctions. This allows for more flexible marketing and better integration with other applications. The products themselves have also been diversified, with different quality levels and response times.
Further refinement of market products is expected in the future, with possible separate rewards for particularly fast responses or other quality characteristics. The role of aggregators, which combine many smaller storage units into a virtual power plant, will also increase.
Importance for the Energy Transition
Frequency stabilization through C&I energy storage systems plays a crucial role in the success of the energy transition. With the further expansion of fluctuating renewable energies and the decline of conventional power plants, the need for flexible, rapidly responding control power providers will continue to grow.
Battery storage systems can effectively fill this gap and help ensure a stable grid with a high proportion of renewable energies. They not only replace the lost control power of conventional power plants, but their faster response even improves the quality of frequency regulation. This contributes to safer and more stable grid operation and ultimately enables a higher share of renewable energy.
In the long term, C&I storage systems, together with other flexible resources such as demand response and power-to-X technologies, could enable a fully renewable energy system that does not require fossil backup power plants. This would make a decisive contribution to the decarbonization of the energy sector.
Conclusion
C&I energy storage systems have established themselves as a valuable tool for frequency stabilization. Their ability to respond to frequency changes in milliseconds makes them ideal providers of primary control power and other system services. Due to the falling costs of battery technology and the increasing need for flexible control power in the wake of the energy transition, their importance will continue to grow.
The greatest advantages of C&I storage systems for frequency stabilization are their fast response time, bidirectional performance, and high precision. Multi-use concepts, in which frequency regulation is combined with other applications such as peak load management or self-consumption optimization, can also significantly improve the economic efficiency of the systems.
In the future, battery storage systems are expected to play a central role in grid stabilization. With advancing technological development, falling costs, and improved regulatory frameworks, they will become an indispensable component of a stable, renewable energy system.