Grid Integration of Industrial Battery Energy Storage Systems (BESS) in Poland – Key Considerations
Applications and Role of Large Energy Storage Systems
Industrial energy storage systems are finding increasingly broad applications in the energy sector, bringing a range of benefits to both grid operators and investors. The development of BESS is crucial for stabilizing power grids, supporting data centers, and enhancing the country’s energy security. Today, energy storage not only supports renewable energy sources but is also one of the pillars of energy transformation. Below are the main functions and capabilities offered by large BESS:
Balancing Renewable Energy Sources: Storage systems allow for accumulating surplus energy from RES (e.g., windy nights or sunny afternoons) and feeding it back into the grid during periods of shortage, thereby stabilizing supplies. This effectively mitigates the instability typical of wind and photovoltaic farms.
Grid Stabilization and System Services: Large BESS can rapidly respond to frequency and voltage fluctuations, performing regulatory functions (e.g., primary frequency regulation, spinning reserve) for the system operator. This significantly increases grid stability and reliability as well as the level of energy security.
Peak Shaving: During peak hours, an energy storage system can supply additional power, relieving stress on the grid during critical moments and reducing the demand for expensive reserve power sources. For industrial consumers, BESS means reduced power consumption from the grid during peak times, leading to lower distribution fees.
Emergency Power Supply and Power Quality Improvement: An energy storage system can act as a backup during power outages, ensuring continuous operation for facilities like data centers, hospitals, and industrial plants. Furthermore, its fast response time improves power quality (maintaining voltage parameters, eliminating short-term fluctuations and sags).
Cost Optimization and Energy Arbitrage: BESS creates the opportunity to purchase energy from the grid when it’s cheap (e.g., at night or during RES overproduction) and then use it or sell it back to the grid during periods of highest prices. Such price arbitrage can be an additional source of income. It’s worth noting that work is underway on legislative changes that will also enable entities other than prosumers to feed energy from storage into the grid and profit from it, which will significantly broaden the scope of profitable applications for energy storage.
Challenges in Integrating Industrial BESS
Installing and connecting a large energy storage system comes with a range of technical and organizational challenges. First and foremost, a thorough analysis of local grid conditions is essential. You need to determine if the surrounding grid has sufficient capacity and stability to accept the additional power discharged from the storage and enable its charging. This is particularly crucial at the medium-voltage distribution network level. It’s necessary to ensure that the voltage profiles, transformer loading capacity, and lines at the planned connection point can handle the bidirectional power flows generated by BESS (consumption during charging and discharge during discharging). Sometimes, modernizing the grid infrastructure – such as increasing line cross-sections, replacing transformers, or installing additional compensation devices – may be necessary to safely integrate the energy storage.
Another challenge involves safety issues and the storage infrastructure itself. Large battery energy storage systems require an appropriate cooling and temperature control system, fire protection, and fire detection and suppression systems (due to the risk of thermal runaway of the batteries). A well-thought-out placement of battery containers is also essential – they should be on stable ground, adhering to requirements for distances from buildings and property boundaries (and, for example, forested areas, in accordance with local regulations). Furthermore, the project must consider acoustic aspects (the operation of battery air conditioning/ventilation generates noise) – sometimes, the use of acoustic screens or maintaining appropriate protective zones is required.
System integration is another crucial aspect. It’s necessary to implement an intelligent energy management system (EMS) that will control the storage’s operation – deciding when to charge and discharge, maintaining set power levels, and communicating with the grid operator or with the connected RES source (if the storage operates with a PV/wind farm). Such an EMS must ensure that the storage fulfills all dispatch commands and operates within the power ranges designated by the operator. Advanced control algorithms are key to maximizing the benefits of BESS and avoiding negative impacts on the grid (e.g., preventing simultaneous charging of multiple storage units during a nighttime valley, which could cause excessive load). Equally important is ensuring continuous monitoring and service – the storage operator should have an online monitoring system that diagnoses battery status, inverter efficiency, and communicates any malfunctions. Regular inspections and maintenance (including replacing worn-out battery modules after a certain number of cycles) contribute to the long-term reliability and safety of the installation.
Challenges also arise in terms of formal and regulatory procedures, although the requirements associated with them are closely linked to technical aspects. For larger energy storage systems, an environmental impact assessment (environmental decision) may be required, especially if the installation capacity exceeds certain thresholds or the investment occupies a large area. Also, construction law may impose the obligation to obtain a building permit – especially when the storage is to be permanently installed (a containerized storage system with a capacity above 20 kW, positioned for longer than 180 days and permanently connected to the ground, is treated as a building object requiring a permit). Such formalities should be included in the project schedule, as well as the time needed to obtain connection conditions and any energy concession (discussed later).
Technical Requirements and BESS Grid Connection Procedure
Connecting an industrial energy storage system (BESS) to the power grid generally follows a similar process to connecting a power generation source (power plant). In practice, this means meeting a series of requirements set by the system operator – both the Distribution System Operator (DSO) when the storage is connected to the medium voltage grid, and the Transmission System Operator (PSE) if we are talking about a storage system connected directly to the high voltage grid (110 kV and above).
The first step is to obtain connection conditions. An investor planning to install an energy storage system must submit an application to the relevant operator for the issuance of grid connection conditions, analogous to connecting a new power plant. Such an application includes, among other things, basic technical data of the planned BESS and connection parameters, as well as a series of technical attachments (site maps, electrical schematic of the installation, equipment data, etc.). The grid operator, after analyzing the connection possibilities (checking fault capacity, line throughput, impact on voltage profile, etc.), issues the connection conditions – a document specifying the point and method of connecting the storage and the technical requirements that must be met. The connection conditions include: the permissible connection capacity of the storage, voltage and grid configuration, required metering system type, protection requirements (e.g., overcurrent, short-circuit protection, anti-islanding systems), and power quality parameters (harmonic emission limits, reactive power regulation requirements, etc.). This document forms the basis for further design work – it specifies what technically needs to be ensured for the storage to function safely within the system.
After receiving the conditions, the investor accepts them and signs a connection agreement with the operator. This agreement regulates the division of responsibilities – who carries out individual connection elements (lines, transformer stations), the amount of the connection fee, connection execution deadlines, etc. Usually, the construction of the connection (cable lines to the MV station, transformer, disconnectors, metering system) is the responsibility of the storage investor, although this can be determined individually. At the implementation stage, it is crucial to execute the technical design in accordance with the conditions – for example, selecting the appropriate transformer and protections, ensuring ATS (Automatic Transfer Switch) automation, or communication with the DSO’s supervisory system. The culmination of the process is the technical acceptance – after installing the storage and completing the connection, tests required by the operator must be performed (e.g., checking the effectiveness of protections, correct operation of automation, power quality). After successful acceptance, the storage is commissioned and appropriate operating agreements are signed with the operator (e.g., an agreement for the provision of distribution services, an update to the energy sales agreement, etc.).
In the context of technical requirements, it is worth highlighting several key issues:
Certified Devices and Compliance with Grid Codes: All components of the BESS must meet current grid standards. This primarily applies to power electronic converters (bidirectional inverters) – they should have a certificate confirming compliance with the requirements of the NC RfG (Network Code Requirements for Generators) and Polish general application requirements resulting from this code. In practice, this means that inverters must, among other things, be capable of operating at specified voltage and frequency parameters, react to frequency deviations (participation in regulation), have automatic islanding prevention functions (anti-islanding), and generate power of a quality within standards (e.g., limited harmonic content). A list of certified devices is maintained by PTPiREE – using equipment from this list simplifies the connection process. If the storage is connected at a higher level (e.g., directly to a 110 kV or 220/400 kV grid), it must additionally meet the requirements of the Network Operation and Maintenance Instructions of the relevant operator – for PSE, this is IRiESP (for transmission), and for DSO, IRiESD (for distribution). For example, PGE’s enormous 400 MW storage project received connection conditions based on full compliance with IRiESP and EU energy market regulations.
Bidirectional Metering System and Measurement: An energy storage system simultaneously draws and supplies energy, so the operator requires the installation of a bidirectional meter of appropriate accuracy class (billing for consumption and supply of energy are separate). Telemetric data from the storage must also be provided to the operator – larger installations must be integrated into a remote telemechanics system so that the operator can monitor current operation (power, state of charge) and, if necessary, remotely limit power in accordance with the connection conditions.
Coordination with Existing Sources (if applicable): Energy storage systems are often added to existing RES installations (e.g., to a photovoltaic farm to increase self-consumption and stabilize grid injection). In such a situation, attention must be paid to the total power injected into the grid. If the storage is to operate behind the meter together with a power plant (at a common connection point), and its power causes the previously agreed connection capacity to be exceeded – it will be necessary to apply for a change or update of the connection conditions. For smaller installations, the DSO sometimes allows a simpler procedure – submitting an update notification, provided that the total installed capacity (RES + BESS) does not exceed the existing connection capacity and 50 kW. However, if the storage exceeds these limits, new connection conditions for the entire system must be obtained. Another solution can be limiting exported power – the storage can charge with RES surpluses but not increase the maximum outflow to the grid beyond an established limit (this is achieved through appropriate control). In any case, when integrating BESS with an existing farm, it’s worth involving the operator at an early stage to determine the permissible connection method (to avoid grid overload).
Energy Generation Concession (in specific cases): Energy storage itself is not yet a separate licensed activity under Polish law, but when the storage functions similarly to a power plant – i.e., it injects energy into the grid and sells it – it may be treated as a generation source for regulatory purposes. According to the Energy Law, energy storage systems with a capacity exceeding 50 kW no longer fall within the definition of a micro-installation. Therefore, for larger BESS installations planned for selling energy to the grid, it may be necessary to obtain a preliminary concession from the Energy Regulatory Office (URE) for electricity generation. Simply put, the investor must apply to the Energy Regulatory Office for the appropriate permit before commercially introducing energy from the storage into the market. In practice, this primarily concerns large, commercial storage systems (e.g., stand-alone BESS for capacity market needs or arbitrage). It’s worth considering the waiting time for such a preliminary concession, although it can often be applied for concurrently with the connection construction process
