Primary Control Power with C&I Energy Storage Systems
In the wake of the energy transition and the steady expansion of renewable energies, the stabilization of power grids is becoming increasingly important. Commercial & Industrial (C&I) energy storage systems have established themselves as an effective solution for providing primary control power and thus making a significant contribution to grid stability. This article examines the role of C&I energy storage systems in the context of primary control power and highlights the opportunities this offers for companies.
Basics of Primary Control Power
The frequency in the European interconnected grid must be kept constant at 50 hertz to ensure a stable power supply. An imbalance between electricity generation and consumption results in frequency deviations that must be quickly compensated. This is precisely where primary control power (PCP) comes into play, being activated within seconds and stabilizing the grid frequency.
Unlike conventional power plants, which must adjust their output mechanically, battery storage systems can react to frequency deviations almost instantaneously. They are capable of either feeding power into the grid (when the frequency drops) or withdrawing power from the grid (when the frequency rises) within milliseconds. This rapid response makes battery storage systems ideal providers of primary control power.
How C&I storage systems work for primary control power
C&I energy storage systems for primary control power operate according to a precise technical principle. If the grid frequency deviates from the target value (50 Hz), the system reacts automatically. The control range typically begins at a deviation of ±10 mHz and reaches full power output or consumption at ±200 mHz. The response is proportional to the frequency deviation according to a clearly defined characteristic curve.
To be able to continuously provide primary control power, the storage system must be maintained at an average state of charge (SoC), typically between 40% and 60%. This enables both the input and input of energy. Modern energy management systems continuously optimize this state of charge to ensure maximum availability with minimal battery aging.
Systems qualified for PRL must be able to deliver their full power for at least 15 minutes, which means the battery capacity should be at least four times the offered power. A 1 MW primary control reserve system therefore requires at least 250 kWh of usable capacity; in practice, however, larger buffers are planned, so that ratios of 1.5 to 2.0 MWh per MW of power are typically achieved.
Requirements and Prequalification
Before a C&I storage system can participate in the primary control reserve market, it must undergo an extensive prequalification process. The transmission system operators impose strict requirements on the technical performance and reliability of the systems. The process includes numerous tests that verify the dynamic behavior of the storage system under various frequency scenarios.
The most important requirements include verification of control accuracy, continuous availability of the offered power, and the possibility of remote control and monitoring by the grid operator. Furthermore, the system must guarantee a high level of reliability and be equipped with redundant systems to ensure full control power even in the event of partial outages.
After successful prequalification, the operator receives approval to participate in the weekly tender process for primary control power. The requirements are regularly reviewed and adjusted as needed to ensure consistently high quality control power.
Primary Control Power with C&I Energy Storage Systems
In the wake of the energy transition and the steady expansion of renewable energies, the stabilization of power grids is becoming increasingly important. Commercial & Industrial (C&I) energy storage systems have established themselves as an effective solution for providing primary control power and thus making a significant contribution to grid stability. This article examines the role of C&I energy storage systems in the context of primary control power and highlights the opportunities this offers for companies.
Basics of Primary Control Power
The frequency in the European interconnected grid must be kept constant at 50 Hertz to ensure a stable power supply. An imbalance between electricity generation and consumption results in frequency deviations that must be quickly compensated. This is precisely where primary control power (PCP) comes into play, being activated within seconds and stabilizing the grid frequency.
Unlike conventional power plants, which must adjust their output mechanically, battery storage systems can react to frequency deviations almost instantaneously. They are capable of either feeding power into the grid (when the frequency drops) or withdrawing power from the grid (when the frequency rises) within milliseconds. This rapid response makes battery storage systems ideal providers of primary control power.
How C&I storage systems work for primary control power
C&I energy storage systems for primary control power operate according to a precise technical principle. If the grid frequency deviates from the target value (50 Hz), the system reacts automatically. The control range typically begins at a deviation of ±10 mHz and reaches full power output or consumption at ±200 mHz. The response is proportional to the frequency deviation according to a clearly defined characteristic curve.
To continuously provide primary control power, the storage system must be maintained at a medium state of charge (SoC), typically between 40% and 60%. This enables both the feed-in and absorption of energy. Modern energy management systems continuously optimize this state of charge to ensure maximum availability with minimal battery aging.
Systems qualified for primary control power must be able to deliver their full power for at least 15 minutes, which means that the battery capacity should be at least four times the available power. A 1 MW primary control reserve system therefore requires at least 250 kWh of usable capacity; in practice, however, larger buffers are planned, so that ratios of 1.5 to 2.0 MWh per MW of power are typically achieved.
Requirements and Prequalification
Before a C&I storage system can participate in the primary control reserve market, it must undergo an extensive prequalification process. The transmission system operators impose strict requirements on the technical performance and reliability of the systems. The process includes numerous tests that verify the dynamic behavior of the storage system under various frequency scenarios.
The most important requirements include verification of control accuracy, continuous availability of the offered power, and the possibility of remote control and monitoring by the grid operator. Furthermore, the system must guarantee a high level of reliability and be equipped with redundant systems to ensure full control power even in the event of partial outages.
After successful prequalification, the operator receives approval to participate in the weekly tender process for primary control power. The requirements are regularly reviewed and adjusted as needed to ensure consistently high quality control power.
Economic Aspects of Primary Control Reserve
The provision of primary control reserve opens up an attractive source of income for operators of C&I storage systems. Unlike other types of control reserve, primary control reserve remunerates only the provision of power, not the energy actually delivered. This means that only the willingness to provide the power when needed is paid for – regardless of whether and how often the storage facility is actually activated.
The remuneration is determined through tenders, which usually take place weekly. Suppliers submit bids stating the price at which they are willing to maintain a certain level of power. Prices are subject to market fluctuations and have fluctuated between €1,000 and €3,500 per MW per week in recent years. For a 1 MW system, this corresponds to annual revenues of between €52,000 and €182,000.
For the profitability calculation, both revenue and costs must be considered. These include the investment costs for the storage system, ongoing operating costs, maintenance costs, and the costs of battery aging due to cyclical load. Battery aging is particularly relevant here, as the continuous charging and discharging processes can lead to a faster loss of capacity than in other applications.
To optimize economic efficiency, many operators rely on multiple uses of the storage system. In addition to primary control power, the system can be used for other applications such as self-consumption optimization, peak shaving, or emergency power supply, provided that availability for the primary control power supply is guaranteed. This combination of different applications, also known as "multi-use" or "stacking of values," significantly improves overall profitability.
Technical Specifications of C&I Storage Systems for PRL
C&I storage systems designed for primary control power differ from conventional energy storage systems in several aspects. They are characterized by particularly fast response times, high cycle stability, and precise control technology. The systems typically consist of several main components: battery modules, power electronics, battery management system, cooling system, and higher-level control system.
Lithium-ion batteries are predominantly used for primary control power, with lithium iron phosphate (LFP) and lithium nickel manganese cobalt (NMC) cells being particularly common. LFP batteries offer advantages in terms of service life and safety, while NMC cells have a higher energy density. The selection of the optimal cell chemistry depends on the specific requirements and the planned operating strategy.
An efficient cooling infrastructure is essential to keep the batteries' operating temperature within an optimal range and prevent premature aging. Depending on the ambient conditions and performance requirements, air cooling, liquid cooling, or even air-conditioned rooms are used.
The heart of the system is the controller, which handles frequency measurement, calculation of the required power change, and control of the power electronics. Modern systems use predictive algorithms to optimize storage behavior and maximize service life. Communication with the grid operator takes place via redundant, encrypted data lines to ensure maximum availability and security.
Advantages of Battery Storage for Primary Control Power
Battery storage systems offer significant advantages over conventional providers of primary control power, such as coal- or gas-fired power plants. Perhaps the most significant advantage is their almost instantaneous response time. While conventional power plants require several seconds to adjust their output, battery storage systems react within milliseconds. This rapid response contributes to more precise frequency control and increases the stability of the power grid.
Another advantage is their high flexibility. Battery storage systems can provide both positive and negative control power, i.e., feed energy into or absorb energy from the grid. Conventional power plants, on the other hand, can often only provide positive control power by reducing their output. This makes battery storage particularly valuable in grids with a high proportion of renewable energy, where both overproduction and underproduction must be compensated.
Furthermore, battery storage systems have a significantly better environmental footprint. They do not cause direct CO2 emissions during operation and thus contribute to climate protection. In comparison, conventional power plants often have to operate at partial load to provide control power, which leads to increased emissions and lower efficiency.
From a business perspective, battery storage systems offer the advantage of lower operating costs. They require no fuel and require less maintenance than rotating machinery. In addition, they can be designed modularly and expanded as needed, increasing investment security and enabling more flexible adaptation to market developments.
Economic Aspects of Primary Control Reserve
The provision of primary control reserve opens up an attractive source of income for operators of C&I storage systems. Unlike other types of control reserve, primary control reserve remunerates only the provision of power, not the energy actually delivered. This means that only the willingness to provide the power when needed is paid for – regardless of whether and how often the storage facility is actually activated.
The remuneration is determined through tenders, which usually take place weekly. Suppliers submit bids stating the price at which they are willing to maintain a certain level of power. Prices are subject to market fluctuations and have fluctuated between €1,000 and €3,500 per MW per week in recent years. For a 1 MW system, this corresponds to annual revenues of between €52,000 and €182,000.
For the profitability calculation, both revenue and costs must be considered. These include the investment costs for the storage system, ongoing operating costs, maintenance costs, and the costs of battery aging due to cyclical load. Battery aging is particularly relevant here, as the continuous charging and discharging processes can lead to a faster loss of capacity than in other applications.
To optimize economic efficiency, many operators rely on multiple uses of the storage system. In addition to primary control power, the system can be used for other applications such as self-consumption optimization, peak shaving, or emergency power supply, provided that availability for the primary reserve is guaranteed. This combination of different applications, also known as "multi-use" or "stacking of values," significantly improves overall profitability.
Technical Specifications of C&I Storage Systems for PRL
C&I storage systems designed for primary control power differ from conventional energy storage systems in several aspects. They are characterized by particularly fast response times, high cycle stability, and precise control technology. The systems typically consist of several main components: battery modules, power electronics, battery management system, cooling system, and higher-level control system.
Lithium-ion batteries are predominantly used for primary control power, with lithium iron phosphate (LFP) and lithium nickel manganese cobalt (NMC) cells being particularly common. LFP batteries offer advantages in terms of service life and safety, while NMC cells have a higher energy density. The selection of the optimal cell chemistry depends on the specific requirements and the planned operating strategy.
A powerful cooling infrastructure is essential to keep the battery operating temperature within an optimal range and prevent premature aging. Depending on the ambient conditions and performance requirements, air cooling, liquid cooling, or even air-conditioned rooms are used.
The heart of the system is the controller, which handles frequency measurement, calculating the required power change, and controlling the power electronics. Modern systems use predictive algorithms to optimize storage behavior and maximize service life. Communication with the grid operator takes place via redundant, encrypted data lines to ensure maximum availability and security.
Advantages of battery storage for primary control power
Battery storage systems offer significant advantages over conventional providers of primary control power, such as coal- or gas-fired power plants. Perhaps the most significant advantage is their almost instantaneous response time. While conventional power plants require several seconds to adjust their output, battery storage systems respond within milliseconds. This rapid response contributes to more precise frequency control and increases the stability of the power grid.
Another advantage is their high flexibility. Battery storage systems can provide both positive and negative control power, i.e., feed energy into or absorb energy from the grid. Conventional power plants, on the other hand, can often only provide positive control power by reducing their output. This makes battery storage systems particularly valuable in grids with a high proportion of renewable energy, where both over- and underproduction must be balanced.
Furthermore, battery storage systems have a significantly better environmental footprint. They do not cause any direct CO2 emissions during operation and thus contribute to climate protection. In comparison, conventional power plants often have to operate at partial load to provide control power, which leads to increased emissions and lower efficiency.
From a business perspective, battery storage systems offer the advantage of lower operating costs. They require no fuel and require less maintenance than rotating machinery. Furthermore, they can be modularly designed and expanded as needed, which increases investment security and enables more flexible adaptation to market developments.
Challenges and Solutions
Despite the many advantages, operators of C&I storage systems for primary control power face several challenges. A key challenge is the continuous optimization of the state of charge. Since the grid frequency is statistically just as often above and below the target value, the energy fed in and drawn in should theoretically balance each other out. In practice, however, longer phases with frequency deviations in one direction can occur, pushing the storage system to its capacity limits.
To address this problem, grid operators allow what is known as "state of charge management." This allows the storage system to draw energy from or feed it into the grid to a limited extent in order to maintain its state of charge within an optimal range. However, these energy flows must be controlled in such a way that they do not counteract the current control direction and thus do not impair frequency stabilization.
Battery aging presents a further challenge. Due to the continuous charging and discharging processes, the batteries are subject to increased cyclic loading, which can lead to faster capacity loss. Modern battery management systems address this challenge with intelligent operating strategies that limit the depth of cycles and avoid extreme charge states. Furthermore, aging is minimized through precise temperature control.
The regulatory framework also presents a challenge, as it is constantly evolving and adapting to the changing market situation. Operators must regularly adapt their systems to new requirements and renew their prequalification. To respond flexibly to these changes, modern systems rely on modular, software-based control architectures that can be easily updated.
Market Development and Future Prospects
The market for primary control power has changed significantly in recent years. While conventional power plants previously primarily provided this system service, battery storage systems have now captured a significant market share. In some European countries, they already provide more than 50% of total primary control power, and the trend is rising.
This development has led to increased competition and falling prices. While remuneration of over €4,000 per MW per week could be achieved a few years ago, prices have now stabilized at a lower level. Nevertheless, primary control power remains an important source of income for storage operators, especially in combination with other applications.
Several trends are emerging for the future. Firstly, technical requirements are expected to continue to increase, particularly with regard to response speed and precision. This could further strengthen the competitive advantage of battery storage systems over conventional providers. On the other hand, the European harmonization of the control power market is progressing, which will lead to larger markets and increased cross-border competition.
Technologically, we are facing exciting developments. New battery technologies such as solid-state batteries or redox flow systems could further improve service life and economic efficiency. At the same time, control algorithms are continuously evolving and increasingly using artificial intelligence methods to optimize operational management and maximize service life.
Practical Example: PRL-Capable C&I Storage System
A typical practical example of a PRL-capable C&I storage system can be found in an industrial park in southern Germany. A 2 MW/2.5 MWh lithium-ion storage system was installed there, primarily designed to provide primary control power, but also serves to optimize self-consumption and as an emergency power supply.
The system consists of 20 battery containers, each with a capacity of 125 kWh, redundant inverters, and a central control system. The installed lithium iron phosphate batteries were specially designed for high-cycle operation and offer a guaranteed service life of 10 years or 7,000 full cycles. A liquid cooling system keeps the batteries constantly in the optimal temperature range between 20 and 25 degrees Celsius.
The investment costs amounted to approximately 2.2 million euros, with approximately 60% for the batteries, 25% for the power electronics, and 15% for planning, installation, and grid connection. Annual operating costs are approximately 50,000 euros, including maintenance, insurance, and energy consumption for air conditioning.
The system continuously participates in the weekly PRL tenders, generating average revenues of 1,800 euros per MW per week, corresponding to annual revenues of approximately 187,000 euros. In addition, the optimization of self-consumption results in electricity savings of around €40,000. Taking into account investment and operating costs, as well as the projected service life, this results in a payback period of approximately seven years.
Conclusion
C&I energy storage systems have established themselves as an ideal technology for providing primary control power. Their rapid response, high flexibility, and low emissions make them a valuable component for stabilizing power grids in the age of renewable energies. Although the market is subject to increasing competitive pressure, primary control power continues to offer attractive revenue opportunities, especially in combination with other applications.
For companies that own or plan to install C&I storage systems, it is worthwhile to explore the possibility of participating in the primary control power market. With the right dimensioning and operating strategy, the provision of primary control power can make a significant contribution to the economic viability of storage while also making an important contribution to the energy transition and grid stability.
In a world with increasingly decentralized and renewable power generation, storage systems and their ability to stabilize the grid are becoming increasingly important. C&I storage systems for primary control power are at the forefront and make a significant contribution to meeting the challenges of the energy system of the future.
Challenges and Solutions
Despite the many advantages, operators of C&I storage systems for primary control power face several challenges. A key challenge is the continuous optimization of the state of charge. Since the grid frequency is statistically just as often above and below the target value, the energy fed in and drawn in should theoretically balance each other out. In practice, however, longer phases with frequency deviations in one direction can occur, pushing the storage system to its capacity limits.
To address this problem, grid operators allow what is known as "state of charge management." This allows the storage system to draw energy from or feed it into the grid to a limited extent in order to maintain its state of charge within an optimal range. However, these energy flows must be controlled in such a way that they do not counteract the current control direction and thus do not impair frequency stabilization.
Battery aging presents a further challenge. Due to the continuous charging and discharging processes, the batteries are subject to increased cyclic loading, which can lead to faster capacity loss. Modern battery management systems address this challenge with intelligent operating strategies that limit the depth of cycles and avoid extreme charge states. Furthermore, aging is minimized through precise temperature control.
The regulatory framework also presents a challenge, as it is constantly evolving and adapting to the changing market situation. Operators must regularly adapt their systems to new requirements and renew their prequalification. To respond flexibly to these changes, modern systems rely on modular, software-based control architectures that can be easily updated.
Market Development and Future Prospects
The market for primary control power has changed significantly in recent years. While conventional power plants previously primarily provided this system service, battery storage systems have now captured a significant market share. In some European countries, they already provide more than 50% of total primary control power, and the trend is rising.
This development has led to increased competition and falling prices. While remuneration of over €4,000 per MW per week could be achieved a few years ago, prices have now stabilized at a lower level. Nevertheless, primary control power remains an important source of income for storage operators, especially in combination with other applications.
Several trends are emerging for the future. Firstly, technical requirements are expected to continue to increase, particularly with regard to response speed and precision. This could further strengthen the competitive advantage of battery storage systems over conventional providers. On the other hand, the European harmonization of the control power market is progressing, which will lead to larger markets and increased cross-border competition.
Technologically, we are facing exciting developments. New battery technologies such as solid-state batteries or redox flow systems could further improve service life and economic efficiency. At the same time, control algorithms are continuously evolving and increasingly using artificial intelligence methods to optimize operational management and maximize service life.
Practical Example: PRL-Capable C&I Storage System
A typical practical example of a PRL-capable C&I storage system can be found in an industrial park in southern Germany. A 2 MW/2.5 MWh lithium-ion storage system was installed there, primarily designed to provide primary control power, but also serves to optimize self-consumption and as an emergency power supply.
The system consists of 20 battery containers, each with a capacity of 125 kWh, redundant inverters, and a central control system. The installed lithium iron phosphate batteries were specifically designed for high-cycle operation and offer a guaranteed service life of 10 years or 7,000 full cycles. Liquid cooling keeps the batteries constantly in the optimal temperature range between 20 and 25 degrees Celsius.
The investment costs amounted to approximately 2.2 million euros, with approximately 60% for the batteries, 25% for the power electronics, and 15% for planning, installation, and grid connection. Annual operating costs are approximately €50,000, including maintenance, insurance, and energy consumption for air conditioning.
The system continuously participates in the weekly PRL tenders, generating average revenues of €1,800 per MW per week, corresponding to annual revenues of approximately €187,000. In addition, the optimization of self-consumption saves approximately €40,000 in electricity costs. Taking into account the investment and operating costs as well as the projected service life, this results in a payback period of approximately 7 years.
Conclusion
C&I energy storage systems have established themselves as an ideal technology for providing primary control power. Their rapid response, high flexibility, and low emissions make them a valuable component for stabilizing power grids in the age of renewable energies. Although the market is subject to increasing competitive pressure, primary control power continues to offer attractive revenue opportunities, especially in combination with other applications.
For companies that own or plan to install C&I storage systems, it is worthwhile to explore the possibility of participating in the primary control power market. With the right dimensioning and operating strategy, the provision of primary control power can make a significant contribution to the economic viability of storage while also making an important contribution to the energy transition and grid stability.
In a world with increasingly decentralized and renewable power generation, storage systems and their ability to stabilize the grid are becoming increasingly important. C&I storage systems for primary control power are at the forefront and make a significant contribution to meeting the challenges of the energy system of the future.