The 99 MW/198 MWh capacity Bumpers Battery Energy Storage System (BESS) project in Buckinghamshire, U.K., has been energized by Harmony Energy Income Trust plc (HEIT) and is now the joint largest BESS (by MWh) in Europe.

With the startup of the Bumpers project — developed by Harmony Energy Limited — HEIT now owns two of the three largest operating BESS sites in Europe (by MWh), following the energization of its 98 MW/96 MWh Pillswood BESS project in Yorkshire in November 2022. Activation of these two systems increases HEIT’s total operational capacity to 277.5 MW/555 MWh across five projects.

These BESS additions will deliver critical balancing services to the U.K. electricity grid network and support the replacement of fossil fuels with renewable energy. An increased number of BESS projects reduces the need for National Grid to curtail wind farm operations during periods when renewable generation exceeds demand. BESS stores that excess power and discharges it back onto the network when the wind has lessened, resulting in a more efficient and reliable renewable energy grid.

These two-hour duration BESS deploy Tesla’s Megapack 2XL rechargeable lithium-ion battery systems and can store enough energy to power about 450,000 homes for two hours.

HEIT’s 49.5 MW/99 MWh Little Raith BESS, located in Scotland, was also energized in October 2023.