As the demand for sustainable energy solutions increases, battery energy storage systems (BESS) have become a crucial component in the UK’s energy transition. These systems enable the storage of electricity, which can be used later to balance grid demand or support renewable energy generation. However, before a battery storage system can be connected to the electricity grid in England, it must meet specific G99 certification and regulatory standards to ensure safety, reliability, and grid compatibility.
One of the most important certifications for battery storage systems is G99 compliance, a regulation that governs the connection of generation equipment to the UK electricity distribution network.
In this article, we will explore what G99 certification means for battery energy storage systems, why it’s important, and the key steps involved in achieving compliance.
What is G99 Certification?
G99 is a set of technical requirements outlined by the Electricity Networks Association (ENA). It applies to the connection of generation equipment (such as solar PV or battery storage systems) to the UK electricity grid. Specifically, G99 ensures that battery storage systems do not cause issues such as voltage fluctuations, power quality disturbances, or grid instability.
Whether you’re a developer, installer, or project manager, understanding and achieving G99 compliance is essential for integrating a battery energy storage system into the UK’s electrical infrastructure.
Why is G99 Certification Compliance Important for Battery Storage Systems?
The UK grid is complex and must maintain stable operation to avoid disruptions. Battery energy storage systems (BESS) are a dynamic component that can introduce fluctuations when exporting energy back to the grid. G99 compliance ensures that these systems meet strict technical criteria, safeguarding both the battery energy storage system and the grid.
Key reasons for G99 certification include:
1. Ensures Grid Stability
- Prevents Instability: G99 ensures that energy storage and generation systems do not cause voltage fluctuations or frequency instability that could disrupt the stability of the grid.
- Response to Grid Events: G99-compliant systems must be able to respond to changes in grid frequency (such as sudden demand spikes or supply drops) and adjust voltage levels to keep the grid stable. This is particularly important as the UK grid integrates more intermittent renewable energy sources like wind and solar.
2. Enhances Safety
- Protection Against Faults: G99 certification mandates that energy systems include protective measures to prevent damage to both the equipment and the grid in case of faults. This includes automatic disconnection during faults such as overcurrent, under-voltage, or electrical surges, ensuring that the system does not cause harm to the broader electrical network.
- Safe Operation: It ensures that the equipment behaves safely under different operational conditions, protecting both people and property from electrical hazards.
3. Guarantees Power Quality
- Meets Power Quality Standards: G99-compliant systems must maintain high-quality power output to prevent disruptions or damage to other equipment connected to the grid. The regulation ensures that battery storage systems (and other generators) do not introduce harmonics or other forms of electrical noise that could compromise the quality of the power being delivered.
- Stable Voltage and Frequency: It helps in maintaining consistent voltage levels and frequency regulation, which is critical for the operation of sensitive equipment connected to the grid.
4. Promotes Seamless Grid Integration
- Facilitates Connection to the National Grid: Achieving G99 compliance allows energy storage systems and generators to seamlessly integrate with the UK’s national and local distribution networks. It ensures that the system is compatible with the standards set by the Distribution Network Operators (DNOs).
- Standards Consistency: G99 helps ensure that various types of generation technologies (solar, wind, batteries) follow a consistent set of technical requirements, making grid integration smoother and more predictable.
5. Supports Renewable Energy Growth
- Enables Renewable Energy Storage: G99 certification is especially important for battery energy storage systems, which help to store energy from renewable sources (e.g., solar and wind) for later use. Compliance with G99 allows energy storage systems to export stored power back to the grid safely, contributing to the UK’s renewable energy goals.
- Improves Grid Flexibility: By ensuring that battery storage systems meet G99 standards, these systems can provide valuable grid services such as frequency response and demand-side management, allowing for a more flexible and resilient energy grid.
6. Legal and Regulatory Compliance
- Required by Law: For any generation system (including battery storage) intending to connect to the grid, G99 compliance is required by UK regulatory authorities. Failure to meet these standards could result in delays in grid connection or penalties.
- Licensing and Permits: G99 certification is often necessary to obtain necessary permits from Distribution Network Operators (DNOs), which are responsible for managing local grid connections.
7. Future-Proofing
- Adapting to Changing Grid Requirements: As the UK energy grid evolves and more decentralized and renewable generation systems come online, G99 certification ensures that systems are capable of adapting to future grid requirements. It helps ensure that energy storage and generation technologies can integrate with smart grid technologies and advanced grid management systems.
- Long-Term Reliability: Systems that are G99 certified are more likely to meet ongoing grid stability and power quality needs in the long term, especially as energy mix transitions towards cleaner sources.
8. Improves Market Access
- Grid Connection Assurance: Compliance with G99 makes it easier for battery storage systems and other generation units to access the UK energy market. By meeting these technical requirements, developers and operators increase the likelihood of their projects being approved for grid connection.
- Investor Confidence: Achieving G99 certification demonstrates that the system meets high standards of quality and reliability, which can enhance confidence from investors and stakeholders in energy projects.
- Grid Stability: Ensures that BESS systems operate without causing power surges, frequency instability, or voltage variations.
- Protection: Includes safety standards to prevent faults, such as over-current or under-voltage conditions.
- Seamless Integration: Verifies that BESS systems are compatible with local Distribution Network Operators (DNOs) and can safely export electricity to the grid.
Key Requirements of G99 for Battery Energy Storage Systems
The G99 standard outlines specific technical requirements for battery storage systems intending to connect to the grid. Here are the key criteria:
1. Generation Capacity
The generation capacity cap for G99 certification is generally as follows:
1. Minimum Size:
- G99 applies to generation systems with a minimum capacity of 16 A per phase (which roughly translates to about 3.68 kW for single-phase systems).
- This means if your system is larger than this threshold, you will need to comply with G99 standards to connect it to the grid.
2. Maximum Size:
- G99 applies to generation systems of all sizes above the minimum threshold, with no upper limit specified by the G99 standard itself.
- This includes everything from small-scale systems (e.g., residential solar with battery storage) to larger systems like industrial-scale solar farms, wind turbines, and battery energy storage facilities.
- However, larger generation systems (e.g., those above 5 MW) typically require additional considerations and may also need to comply with other regulations and standards, such as G59 (which is used for larger generation units connected to the grid).
Threshold for G99 vs. G59:
- G99: Typically applies to generation systems up to 5 MW.
- G59: For larger systems, especially those over 5 MW, and can apply to grid-connected generation up to 50 MW or more. G59 governs the technical requirements for these larger systems to ensure their safe integration with the grid.
2. Grid Code Compliance – G99 Certification
Battery storage systems must comply with grid codes to ensure proper interaction with the distribution network. G99 covers important aspects like:
- Frequency Response: Battery systems must respond to frequency changes, helping maintain grid stability.
- Voltage Regulation: Battery systems should help manage and control voltage levels, preventing fluctuations that could damage sensitive equipment.
- Power Quality: Batteries must not degrade the quality of electricity, ensuring clean and stable power delivery to the grid.
3. Protection Mechanisms
Battery energy storage systems must include protection features such as automatic disconnection in the event of faults. These mechanisms ensure the safety of both the storage system and the grid. For example:
- Under-voltage and Over-voltage Protection
- Fault Detection and Disconnection Procedures
4. Testing and Certification
To achieve G99 compliance, battery systems must undergo rigorous testing to verify that they meet all safety and performance standards. These tests assess the system’s ability to function within the network parameters and ensure it won’t cause grid instability or operational issues.
The Connection Process for G99 Compliance
Before connecting a battery storage system to the grid, developers and installers must go through the following steps to ensure G99 compliance:
1. Submit a Connection Application
The first step is submitting a connection application to the local Distribution Network Operator (DNO). The application details the technical characteristics of the proposed battery storage system and includes a request to connect to the grid.
2. Evaluation by the DNO
The DNO will assess the technical requirements outlined in the G99 standard and determine if the proposed system meets the necessary criteria. If the system does not meet the requirements, adjustments may be needed.
3. System Testing
Once the battery storage system passes the initial evaluation, it may be subjected to additional performance testing to ensure full compliance with G99. This may include tests for frequency response, voltage control, and other operational factors.
4. Connection Agreement
Once the system has been approved for G99 compliance, the DNO will issue a connection agreement, allowing the battery storage system to be safely connected to the grid.
Additional Standards and Certifications for Battery Storage Systems
While G99 compliance is essential for connecting to the grid, there are other important certifications and standards that battery energy storage systems must adhere to. These include:
- IEC 62109: Safety of power converters for use in photovoltaic power systems.
- IEC 62619: Safety requirements for secondary lithium cells and batteries.
- BS EN 61439: Low-voltage switchgear and control gear assemblies.
- UKCA Marking: Certification for product safety and compliance within the UK market.
These standards help ensure that battery storage systems are both safe and efficient, supporting their integration into the broader energy network.
Conclusion: Why G99 Compliance is Crucial for Battery Energy Storage Systems
As battery energy storage systems play an increasingly pivotal role in the UK’s energy landscape, achieving G99 compliance is essential for ensuring grid stability and safety. The rigorous technical requirements of G99 ensure that BESS systems integrate smoothly with the national grid without causing disruptions or power quality issues.
For developers and installers, understanding and adhering to the G99 standard is key to a successful battery storage system installation. It guarantees that systems can operate safely, provide grid services, and contribute to the UK’s renewable energy goals.
By following the G99 guidelines and completing the necessary certification process, battery storage systems will be ready to meet the challenges of tomorrow’s energy grid.
Hybrid On and Off Grid BESS
- MEG 50kW x 75kWh
- MEG 100kW x 150kWh
- MEG 150kW x 225kWh
- MEG 200kW x 300kWh
- MEG 300kW x 645kWh
- MEG 500kW x 1075kWh
On Grid Only BESS
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