Harmony Energy switches on 70 MWh Skeeby BESS in UK

UK-based utility-scale battery storage developer Harmony Energy has energized its 35 MW / 70 MWh Skeeby battery energy storage system (BESS) near Richmond, North Yorkshire, England. 

The project commenced work in early 2026, with a roughly seven-month turnaround from shovel to energization. The project uses unspecified Tesla Megapacks, and with the new asset now energized, it is preparing to enter commercial operations, according to Harmony Energy. The site is a standalone BESS, located directly next to the 55 MW Skeeby Solar Farm, a former Harmony Energy site that it sold in 2023, though it retained the battery project.  

ESS News understands the project utilizes Tesla Megapack 2XL models, which Harmony has used at other projects, including its Bumpers and Little Raith projects. There are a clear 10 bays of batteries, and Wilson Power Solutions said on its website that it supplied ten 4.2MVA 33kV/480-480V Wilson T2 Ecotrans large distribution transformers and one 100kVA 33kV/433V Wilson auxiliary distribution transformer.

It also dug into some of the electrical specifics, saying: “Our Wilson T2 MV Transformers are custom-engineered to Tier 2 loss levels to interface directly with the site’s Tesla Megapack battery units via a dual 480-480V LV winding configuration. Each unit has twin 480V secondary windings in a Dyn11yn5 configuration, feeding two Megapack groups from a single transformer.” It also added details of fire-safety improvements.

Swiss-ownership

Skeeby is part of Harmony Energy’s strategy to build longer-duration storage assets, and it is the company’s first site to go live since July’s announcement that Swiss electricity producer Alpiq had acquired a 90 percent stake in Harmony Energy. The acquisition added approximately 400 MW of assets under construction to Alpiq’s existing BESS portfolio in Europe. 

Despite the acquisition, Harmony Energy will continue to operate independently, while CEO and co-founder Peter Kavanagh retains a stake in Harmony Energy. Alpiq’s head of BESS, Christoph Bellin, has joined Harmony Energy’s executive management team, while continuing in his role at Alpiq. 

“Skeeby is an exciting milestone for Harmony Energy, not only because it brings another important battery storage project online, but because it is the first site to be energized since our strategic investment from Alpiq,” Kavanagh said. 

“That investment gives us additional backing to accelerate the delivery of projects like this across the U.K. and Europe, while continuing to operate with the same team, brand and development expertise that have underpinned Harmony Energy’s growth to date.”

In 2025, Harmony Energy commissioned its 100 MW / 200 MWh Chevire BESS at the port of Nantes–Saint‑Nazaire in France.