Grid Application & Technical Considerations for Battery Energy Storage Systems

Energy Storage – The First Class

In the quest for a resilient and efficient power grid, Battery Energy Storage Systems (BESS) have emerged as a transformative solution. This technical article explores the diverse applications of BESS within the grid, highlighting the critical technical considerations that enable these systems to enhance overall grid performance and reliability.

As we navigate the complexities of modern energy management, the integration of storage technologies has become essential in addressing challenges posed by fluctuating demand and the increasing reliance on renewable energy sources.

The article covers several key topics, starting with electric energy time-shift, where BESS enables the purchase and storage of inexpensive energy during low-cost periods for later use when prices rise. This practice not only stabilizes energy costs but also optimizes the utilization of renewable resources by storing excess energy that would otherwise be curtailed.

Additionally, we discuss the role of BESS in enhancing electric supply capacity, particularly in deferring or reducing the need for new central station generation investments. The importance of regulation as an ancillary service is also examined, emphasizing how BESS can effectively manage interchange flows and maintain grid frequency amid varying demand.

Finally, the black start capability of BESS is addressed, showcasing its potential to energize transmission lines and restore power plants after catastrophic failures.

Through these discussions, this article aims to provide a comprehensive understanding of the vital role BESS plays in modern grid applications, paving the way for a more resilient and sustainable energy future.

Table of Contents:

1. Black Start: The Key to Power System Recovery After a Blackout
2. BESS Black Start for Grid Compliance and Recovery
3. Voltage Support with Battery Energy Storage Systems (BESS)
4. Spinning, Non-Spinning, and Supplemental Reserves with Battery Energy Storage Systems (BESS)
5. Regulation with Battery Energy Storage Systems (BESS)
6. Electric Supply Capacity and the Role of Energy Storage Systems (ESS)
7. Electric Energy Time-Shift (Arbitrage) with Energy Storage Systems
8. Attachment (PDF) ✅ – Design and Operation Guide For Photovoltaic Systems

1. Black Start: The Key to Power System Recovery After a Blackout

A black start is a crucial procedure used to restore power to a grid after a complete or partial blackout. It is a carefully coordinated process designed to restart the power system without relying on external electricity sources, as the grid itself may be down.

The black start process involves multiple stages, each aimed at gradually rebuilding the grid’s generation and transmission capabilities to ensure a safe and stable recovery.

Stage #1 – Starting isolated power stations:

After a blackout, power stations that are capable of starting independently, without drawing power from the grid, are brought online first. These are usually small, strategically placed power plants equipped with black start capability, such as hydropower plants, which can start without any external energy supply.

These stations serve as the foundation for the restoration process.

Stage #2 – Reconnecting stations:

Once the initial black start units are up and running, the next step is to progressively reconnect other larger power plants and critical loads. These larger stations, which typically rely on external power to operate, are restarted using the energy generated by the black start units. As more generating units are brought online, they begin to feed energy into the grid, gradually re-establishing the power supply across wider areas.

The reconnection process must be carefully controlled to avoid overloading the system.

Stage #3 – Using auxiliary generators:

In some cases, on-site auxiliary generators, often small diesel or gas-powered units, are used to start the main generators at power stations. These auxiliary generators provide the initial power needed to bring larger generators online when the grid is down, ensuring that the larger power stations can contribute to the black start process.

Figure 1 – The Single Line Diagram of the Substation Auxiliary Supply Panel

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2. BESS Black Start for Grid Compliance and Recovery

Battery Energy Storage Systems (BESS) play a pivotal role in grid recovery through black start capabilities, providing critical energy reserves during catastrophic grid failures. In the event of a major blackout or grid collapse, BESS can deliver immediate power to re-energize transmission and distribution lines, offering a reliable and decentralized solution for restoring system stability.

By supplying station power, BESS ensures that power plants can be brought back online without requiring external electricity from the grid, thereby enabling a smoother and faster recovery process.

This capability makes BESS a key component in black start strategies for modern, renewable-heavy grids.

Key Specifications and Capabilities:

• Size Range: BESS systems designed for black start applications typically range from 5 to 50 MW, allowing them to cater to a variety of grid scales and restoration needs.
• Target Discharge Duration: These systems can deliver power for anywhere between 15 minutes to 1 hour, offering a vital window for re-energizing key grid infrastructure and initiating larger generation sources.
• Minimum Cycles/Year: BESS designed for black start applications are typically expected to cycle 10 to 20 times per year, ensuring that they remain a robust and reliable backup resource when needed.

Figure 1 – The PV-BESS as black-start power to start auxiliaries of thermal power station

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3. Voltage Support with Battery Energy Storage Systems (BESS)

Voltage support is a critical function in maintaining grid stability, typically achieved by generating reactive power (measured in VAr) to counteract reactance within the electrical network. Traditionally, designated power plants or synchronous generators have been responsible for generating reactive power to maintain voltage levels across the grid.

However, with the growing adoption of Battery Energy Storage Systems (BESS), this task can be effectively handled by strategically placed storage systems, offering a more flexible and distributed solution.

How BESS Provides Voltage Support?

Instead of relying solely on large, centralized power plants for reactive power, BESS can be installed at key locations across the grid, or distributed near large load centers. This distributed approach allows for a more localized response to voltage fluctuations, improving grid reliability and reducing transmission losses.

By placing energy storage systems where they are most needed, grid operators can ensure more efficient voltage regulation, especially in areas with high load density or regions far from traditional generation sources.

This flexibility enables the BESS to quickly respond to dynamic changes in grid conditions, sourcing or sinking reactive power to stabilize voltage without affecting the overall active power supply.

Key Specifications and Capabilities:

• Storage System Size Range: Voltage support applications typically utilize BESS systems ranging from 1 to 10 MVAr, depending on the scale of the grid and the specific voltage regulation needs.
• Target Discharge Duration: Unlike energy-focused applications, voltage support does not have a specific discharge duration as it depends on the instantaneous need for reactive power. Instead, BESS continuously adjusts its output to maintain voltage levels within acceptable ranges.
• Minimum Cycles/Year: Similarly, the number of cycles for voltage support is not predetermined since the system is in continuous use, adjusting its reactive power output as grid conditions demand.

Advantages of BESS for Voltage Support:

BESS offers several advantages over traditional methods of voltage support:

• Decentralized Control: With BESS, voltage support can be distributed across the grid, reducing dependency on large power plants. This allows for faster response times and more precise voltage control in local areas.
• Improved Efficiency: By strategically placing storage systems near large loads, BESS reduces the need for long-distance transmission of reactive power, which often leads to energy losses.
• Scalability: BESS can be scaled based on grid requirements, whether through centralized installations or smaller units placed throughout the grid. This scalability allows utilities to adapt as the grid evolves with increasing renewable integration.
• Flexibility: BESS systems can operate in various modes, including both active and reactive power generation. This makes them versatile tools for both voltage support and overall grid management.
  Battery Energy Storage Systems, when equipped with advanced Power Conversion Systems, can provide essential voltage support to the grid. By offering a decentralized, scalable, and flexible solution, BESS not only enhances voltage stability but also supports the broader goal of transitioning to renewable energy and reducing the reliance on traditional power plants for grid support functions.

Figure 3 – BESS units along with 33kV/480V auxiliary transformers

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4. Spinning, Non-Spinning, and Supplemental Reserves with Battery Energy Storage Systems (BESS)

The stability and reliability of an electric grid depend on having adequate reserve capacity that can be activated when a portion of the regular electric supply unexpectedly goes offline. This reserve capacity ensures that the grid can continue operating without interruption in case of a generation shortfall or a sudden loss of power supply from a large generator.

Reserves are typically sized to match the capacity of the largest generation unit on the grid, ensuring that any outage affecting the largest generator can be compensated for by immediately available power. The reserve capacity generally ranges between 15% and 20% of the total normal electric supply.

Battery Energy Storage Systems (BESS) can be utilized to provide three types of reserves: spinning, non-spinning, and supplemental reserves.

Spinning Reserves:

Spinning reserves refer to the reserve power that is already online and synchronized with the grid. It is the first line of defense during a grid disturbance and can be dispatched almost instantaneously. Traditionally, this role has been filled by thermal power plants or hydroelectric generators that are running below full capacity but are ready to ramp up quickly in case of a shortfall.

BESS can now provide spinning reserves by maintaining a charge that can be released instantaneously when needed, without the delay associated with ramping up mechanical generators. This makes BESS a faster and more efficient option for providing spinning reserves, especially as it requires no fuel and can respond within milliseconds.

Watch video – Spinning reserve in power generation

Non-Spinning Reserves:

Non-spinning reserves are offline but can be brought online and synchronized with the grid within a short period, typically 10 minutes or less. BESS can fulfill this requirement by being on standby and ready to deliver power as soon as it’s needed. Since battery storage systems do not have the mechanical constraints of traditional generators, they can provide non-spinning reserves more quickly and with greater precision.

Supplemental Reserves:

Supplemental reserves are typically the last to be called upon during a power supply shortfall. They are not required to respond as quickly as spinning or non-spinning reserves but must still be able to contribute to grid stability within a defined period, often 30 minutes to an hour.

BESS can serve as supplemental reserves by offering flexible and scalable power that can be deployed in stages based on the severity and duration of the supply shortfall. The rapid deployment capabilities of BESS allow it to efficiently handle various reserve functions, ensuring the grid remains stable even during prolonged power shortages.

Key Specifications and Capabilities

• Storage System Size Range: 10–100 MW, depending on the size of the grid and the specific reserve requirements.
• Target Discharge Duration: 15 minutes to 1 hour, providing flexibility for short-term and slightly longer-term reserve needs.
• Minimum Cycles/Year: 20–50 cycles per year, indicating that the BESS system should be ready to deploy multiple times annually in response to grid events.

Advantages of BESS for Reserve Functions

1. Instantaneous Response: BESS can provide spinning reserves with near-instantaneous response times, improving grid reliability during sudden disturbances.
2. Fuel-Free Operation: Unlike traditional generators, BESS does not require fuel, making it more environmentally friendly and less costly to operate.
3. Scalability: BESS can be scaled to meet the reserve needs of any grid, from small microgrids to large national grids.
4. Flexibility: The same BESS system can provide multiple reserve services, including spinning, non-spinning, and supplemental reserves, without requiring additional equipment or infrastructure.

Figure 4 – Use of spinning reserve to maintain system frequency

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5. Regulation with Battery Energy Storage Systems (BESS)

Regulation is a critical ancillary service that ensures the stability and reliability of a power grid by balancing supply and demand in real-time. Its primary goal is to maintain grid frequency within the prescribed limits, ensuring smooth operation of the power system and preventing disruptions caused by frequency imbalances.

Battery Energy Storage Systems (BESS) are particularly well-suited for providing regulation services due to their rapid response capabilities and operational flexibility.

What is Regulation?

Regulation involves controlling interchange flows between different control areas of the grid and managing momentary fluctuations in electricity demand within a specific area. These fluctuations can arise due to small changes in demand, such as sudden variations in the load profile of a region. To ensure the grid’s frequency remains stable (typically around 50 or 60 Hz), power generation and demand must always be closely matched.

In traditional power systems, regulation is typically handled by generators adjusting their output to accommodate demand variations. However, with the growing integration of renewable energy sources, which are inherently variable, traditional regulation methods are becoming less effective.

This is where BESS excels, providing a much faster and more accurate response to frequency deviations.

The Role of BESS in Regulation

BESS can rapidly inject or absorb power into the grid to correct frequency imbalances. When the grid frequency drops (due to demand exceeding supply), BESS discharges energy to help bring the frequency back to normal levels. Conversely, when the frequency rises (due to excess supply), BESS can absorb the surplus energy, helping to maintain balance.

One of the key advantages of BESS in regulation is its ability to perform these adjustments almost instantaneously, far faster than traditional mechanical generators. This rapid response is essential for maintaining grid stability, especially in grids with high penetration of renewable energy sources like wind and solar.

Key Specifications for BESS in Regulation:

• Storage System Size Range: Typically between 10–40 MW, depending on the grid’s size and regulation needs.
• Target Discharge Duration: BESS can discharge for periods ranging from 15 minutes to 1 hour, providing flexibility for different regulation scenarios.
• Minimum Cycles/Year: The regulation function requires frequent cycling, with BESS systems typically cycling 250 to 10,000 times per year. This high cycling capability is essential for continuous regulation.

Benefits of BESS for Regulation:

1. Rapid Response: BESS responds to frequency deviations in milliseconds, making it far more effective for regulation compared to traditional generation sources.
2. Precision: BESS offers precise control over power output, enabling fine-tuned adjustments to maintain frequency stability.
3. Reduced Wear and Tear: Unlike traditional generators that experience wear and tear due to constant cycling, BESS can handle frequent cycling with minimal degradation, enhancing system longevity.
4. Grid Integration: BESS helps accommodate renewable energy sources by smoothing out the variability in supply, allowing for more renewables to be integrated into the grid without compromising frequency stability.

Watch Video – 1MWH BESS Containerized Energy Storage System

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6. Electric Supply Capacity and the Role of Energy Storage Systems (ESS)

Energy storage systems (ESS) are playing an increasingly vital role in modernizing electric supply systems. They offer utilities and grid operators the flexibility to manage peak demand and provide a more reliable electricity supply. One of the key benefits of ESS is its ability to defer or reduce the need for new central station generation capacity or purchasing additional capacity from the wholesale electricity market, especially during times of peak demand.

Leveraging ESS to Optimize Electric Supply Capacity

The demand for electricity can fluctuate significantly throughout the day, with peak periods often placing a strain on generation resources. Traditionally, utilities would invest in building new power plants or purchasing extra capacity to meet this peak demand. However, this approach is not always the most cost-effective or environmentally sustainable solution.

Energy storage systems, by contrast, provide a way to store excess energy during periods of low demand and discharge it when demand spikes, helping to flatten the demand curve and reduce the need for additional generation capacity.

How ESS Contributes to Capacity Optimization?

Energy storage systems can be strategically deployed in electric grids to handle peak loads and provide backup power during system emergencies. By discharging stored energy during peak times, ESS helps utilities avoid overloading existing generation infrastructure and reduces the likelihood of grid failures.

Moreover, ESS allows for greater utilization of renewable energy, as excess energy from sources like wind and solar can be stored and used later when the supply from these sources is limited.

Key Specifications for Energy Storage in Capacity Applications:

• Storage System Size Range: ESS for capacity applications can range from 1 MW to 500 MW, depending on the specific needs of the electric supply system.
• Target Discharge Duration: Typically, ESS in this role is designed to provide power for 2 to 6 hours, covering peak demand periods or supply shortfalls.
• Minimum Cycles/Year: Systems involved in electric supply capacity generally operate with 5 to 100 cycles per year, depending on the frequency and duration of peak demand events.

Benefits of ESS in Electric Supply Capacity:

1. Cost Savings: By reducing the need for new generation capacity or expensive capacity purchases, ESS helps utilities save on infrastructure investments and operational costs.
2. Peak Load Management: ESS can smooth out demand spikes, lowering the strain on generation facilities and the overall grid.
3. Grid Reliability: During periods of high demand or system stress, ESS can provide reserve power to enhance grid stability.
4. Support for Renewable Integration: ESS enables better use of renewable energy by storing excess generation for later use, reducing the need for backup fossil fuel-based generation.

Watch Video – Tour our 1MWh Battery 20ft Containerized Energy Storage System

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7. Electric Energy Time-Shift (Arbitrage) with Energy Storage Systems

Electric energy time-shift, also known as arbitrage, is an essential application of energy storage systems (ESS) that capitalizes on price fluctuations in the electricity market. This strategy involves purchasing or storing electricity during periods when prices are low and then discharging or selling that stored energy during periods of high demand when prices are elevated.

This not only maximizes the financial returns from energy trading but also enhances grid efficiency by aligning supply with demand more effectively.

The Mechanism of Energy Time-Shift

Energy time-shift works by charging an energy storage system when electricity is cheap—typically during off-peak hours when demand is low and renewable energy sources like wind and solar are producing more energy than can be immediately consumed. Instead of curtailing this excess energy, it is stored in ESS.

Later, during peak demand periods when electricity prices rise, the stored energy can be discharged to meet the higher demand or sold back to the grid at a premium, generating profits for utilities or grid operators.

Watch Video – What is the Time Shift of Energy?

Time-Shift with Renewable Energy Integration

In addition to market arbitrage, ESS can also perform energy time-shift by storing surplus energy from renewable sources such as wind or solar, which may produce more energy than the grid can absorb in real-time. This prevents curtailment, ensuring that renewable energy is not wasted.

Later, the stored renewable energy can be utilized when generation drops, allowing for a more consistent and stable renewable energy contribution to the grid.

Key Specifications for Energy Time-Shift Applications:

• Storage System Size Range: Energy storage systems designed for arbitrage can range from 1 MW to 500 MW, depending on the grid size and market dynamics.
• Target Discharge Duration: Typically, the discharge duration for arbitrage is less than 1 hour, as energy is quickly released during high-demand periods.
• Minimum Cycles/Year: Energy time-shift systems typically perform 250 or more cycles per year, frequently charging and discharging to take advantage of fluctuating energy prices.

Benefits of Energy Time-Shift with ESS:

1. Financial Optimization: By buying energy when it’s cheap and selling it when prices are high, ESS helps utilities and grid operators maximize revenue.
2. Increased Renewable Utilization: Time-shift enables greater use of renewable energy, as excess generation can be stored rather than curtailed, leading to more efficient grid operation.
3. Grid Flexibility: ESS provides greater flexibility in matching energy supply with demand, ensuring smoother operation during peak load periods.
4. Reduction of Curtailment: By storing excess renewable energy instead of wasting it, ESS helps avoid the curtailment of valuable clean energy resources.

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8. Attachment (PDF)

Download (PDF): Design and Operation Guide For Photovoltaic Systems (for premium members only):