Battery Energy Storage Systems

Full scope of transformers for Battery Energy Storage Systems

We design, manufacture and supply the full scope of transformers needed for Battery Energy Storage Systems (BESS), including large MV distribution transformers, power grid transformers and bespoke auxiliary and earthing transformers. Supplying over 7.4GW/13GWh of BESS projects, we have worked with key battery manufacturers such as Tesla, BYD and CATL to supply transformers that enable the delivery of landmark projects in the UK and Europe. 

We offer the full range of transformers required for BESS projects, including power transformers up to 300MVA and 400kV, MV distribution transformers that connect to battery packs or inverters, and auxiliary and earthing transformers.

Advancements in battery technology have significantly improved the life cycle of battery storage systems, providing greater energy density, faster response and enhanced flexibility compared to traditional methods. Often called "the key to unlocking renewables," the modern growth of Battery Energy Storage Systems (BESS) is driven by two primary trends: the expansion of renewable energy to accelerate the transition away from fossil fuels, supported by government targets of adding a minimum of 8GW onshore wind and 22GW solar capacity by 2030, and the rising electricity demand spurred by the electrification of transport and heat. As of the end of 2024, there was 4.5GW of connected BESS in Great Britain and by 2030, GB needs 23-27GW of BESS to meet the demands of a clean power system.

key components

In addition to the battery packs, BESS contains three crucial hardware components: inverters, switchgear and transformers which are essential for efficient and safe operation. These components work in unison to ensure energy storage and distribution meet the demands of modern energy systems.

1. Batteries:
   There are multiple DC battery technologies in the market, some more mature than others in terms of commercial availability and technical properties. Different battery pack solutions offer several charge and discharge durations with one, two, four and six hours being the most common.

2. Inverters:
   Batteries store energy as direct current (DC) but to benefit from this stored energy, it needs to be converted to alternating current (AC), making it usable for the grid or end-users. Inverters are critical for bidirectional charge (converting AC to DC) and discharge (converting DC to AC) to enable seamless integration with power grids and renewable energy sources.

3. Switchgear:
   Switchgear serves as the protective shield for the BESS, safeguarding the system and the connected grid against electrical faults or abnormal operating conditions. It isolates faults, ensures safe disconnection, and protects equipment from damage due to overloads, short circuits, or other hazards. Modern switchgear also incorporates monitoring and control systems, enabling quick responses to anomalies and enhancing overall system reliability.

4. Transformers:
   Transformers adjust the voltage levels to ensure compatibility between the BESS and the grid. During energy discharge, transformers step up the voltage to match grid requirements, while during charging, they step down the voltage to the appropriate levels for the batteries. This voltage transform is vital for minimising energy loss, ensuring efficiency, and maintaining the stability of the electrical network. Depending on the design and battery capacity, medium voltage (MV) transformers (or large distribution transformers) connect one or more battery packs. MV transformers then connect to a power transformer (or grid transformer) which is further connected to a Distribution Network Operator (DNO) grid at 132kV and below, or to a transmission network (National Grid) at 275kV or 400kV. BESS sites often require a higher-than-usual impedance level. Transformers can also provide earthing or auxiliary solutions to the site.