AIP Management buys into BW ESS’ 2.4 GWh UK battery storage portfolio

In its first investment in standalone battery energy storage systems (BESS), Copenhagen-based infrastructure investor AIP Management has acquired a 49% equity stake in a 700 MW UK portfolio from developer and asset owner BW ESS.

The transaction involves three large-scale BESS assets developed by BW ESS, including the 100MW / 331MWh Bramley project, which is already operational.

In 2024, the Bramley site set a precedent by securing the first long-term tolling agreement for a standalone BESS asset in the UK. Earlier this year, it set a record for speedy commissioning with just two weeks between grid energization and commercial operation. China’s Sungrow, which provided its PowerTitan 2.0 systems to the project, described the feat as a 72% efficiency gain, setting a record for BESS delivery in the UK and across Europe.

The other two assets in the portfolio – Hams Hall (400MW / 1,422MWh) and Berkswell (200MW / 712MWh) – are under construction.

Located in the Midlands and South-East England, the portfolio is strategically positioned near major load centres and National Grid substations, mitigating congestion risk and enhancing access to arbitrage and balancing services opportunities. In addition to tolling, the revenue profile of the assets is also underpinned by long-term capacity market contracts.

“This investment reflects our conviction in the UK energy storage market and builds on the knowledge we have developed through our existing investments in co-located BESS,” said Greg Falzon, Partner and Co-Head of Investments at AIP. 

Upon completion, the assets will be held in a newly formed AssetCo, with BW ESS retaining a 51% majority stake. BW ESS will manage construction and operations across the portfolio, drawing on its track record of more than 500 MWh of operational BESS, 3.3 GWh under construction, and a development pipeline spanning six markets. 

“We are delighted to welcome AIP as our partner in this strategically important portfolio,” said Erik Strømsø, CEO of BW ESS. “We see strong alignment in our approaches and a shared ambition to deliver storage assets at scale.

Headquartered in Oslo, BW ESS has significantly expanded its European footprint in 2025, securing a series of large-scale strategic partnerships and financing agreements. These include a 1 GW partnership with MIRAI Power and a 1.5 GW collaboration with Zelos in Germany, a 2.9 GW pipeline with ACL Energy in Italy, and a 2.2 GW agreement with Ibersun in Spain. In Sweden, the company secured a loan facility to support what is currently the country’s largest BESS portfolio.

According to the company website, BW ESS has another 1 GW of BESS project in the UK under development.