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Short guide

Batteries at Cardiff East: what they can and cannot do

A short guide for residents on the battery storage proposed at the Cardiff East Park and Ride data centre (application 26/00109/HYB).

About this guide

Written for this website from published sources. Where we make our own estimate, we say so.

Last checked 21 October 2026.

What is a battery store?

A battery energy storage system is a large bank of batteries, usually in units the size of shipping containers. It stores electricity; it does not make any. It must be charged from the grid or from a generator on site.

What does the application say?

The Design and Access Statement says the site will have ‘on-site battery storage’ and operate as a ‘local microgrid’. Neither the size nor the type of battery is given. The Environmental Statement does not assess the batteries at all.[1][2]

What batteries could do well

  • Cover short power cuts, so that the 40 diesel generators start less often. The applicant’s own assessment says the generators are likely to breach the legal limit for nitrogen dioxide if they run for more than 30 minutes.[2]
  • Charge when Welsh wind and solar power is plentiful, and run the site when the grid is under strain.[3]
  • Help keep the national grid stable. The grid operator has asked data centres to offer this kind of flexibility.[4]

What batteries cannot do

  • Replace the gas power station. Until the grid connection arrives, which the applicant expects in 2033, there is nothing to charge the batteries from except the gas turbines.[2]
  • Keep a 150 MW site running through a three-day power cut. That would take about 10,800 MWh of storage; by our calculation, many times more than the biggest battery sites in Britain.

The risks

  • Lithium batteries can catch fire and explode. A 20 MW battery fire in Liverpool in 2020 caused an explosion and released toxic gases, and firefighters were on site for about 59 hours.[5]
  • In 2025 a battery fire at South Korea’s main government data centre burned for about 22 hours and took 647 public services offline.[6]
  • Firewater from a battery fire can carry heavy metals and other pollutants. The applicant’s own report says this could reach the Rhymney and the Severn Estuary’s protected sites. The site is also in a flood zone.[7]
  • National guidance asks fire services to comment on battery stores, but they are not statutory consultees on them. The Council did consult South Wales Fire and Rescue Service on this application; its response is not on the register, and the applicant’s summary says it raised no matters needing further technical input. There is no assessment of fire or major accidents in the Environmental Statement.[8][11][2]

Why it matters for Wales

Wales generates more electricity than it uses, but most of it still comes from gas. Running all year, a 150 MW data centre would use roughly a tenth of all the electricity Wales consumes; that is our own estimate. In a national shortage, a data centre with its own generators is not normally among the sites protected from rota power cuts. It would then run its diesel generators, which the air quality assessment does not consider.[9][10]

Questions worth asking

  • How big will the batteries be, what type, and where on the site?
  • Will the batteries be used first in a power cut, so that the diesel generators start only when they must?
  • Will the site be required to cut its demand from the grid when Wales’s supply is short?
  • Where is the assessment of fire, explosion and firewater, in a flood zone beside the Rhymney?

Comments on the application close on 28 October 2026. See the case study for how to comment.

Sources for this page

  1. Design and Access Statement for 26/00109/HYB (January 2026), page 20. https://www.cardiffidoxcloud.wales/publicaccess/files/25EFB6301AC3D96738109BA577CBA7F4/pdf/26_00109_HYB-DESIGN_AND_ACCESS_STATEMENT-6331506.pdf
  2. Environmental Statement Vol. I Part 1 (February 2026), Chapters 1, 3 and 4. https://www.cardiffidoxcloud.wales/publicaccess/files/E0E64E89C93D7E1CF72DFB53E1BABE76/pdf/26_00109_HYB-ENVIRONMENTAL_STATEMENT_VOL_I_PART_1-6351362.pdf
  3. NESO and partners, Carbon Intensity API: regional forecasts, including South Wales. https://carbonintensity.org.uk/
  4. NESO, 'NESO calls on industry support to deliver flexibility' (31 October 2025), naming data centres among the large users it wants to work with. https://www.neso.energy/neso-calls-industry-support-deliver-flexibility
  5. Merseyside Fire and Rescue Service, Significant Incident Report: Carnegie Road battery storage fire, Liverpool, 15 September 2020 (as submitted to the Planning Inspectorate). https://nsip-documents.planninginspectorate.gov.uk/published-documents/EN010106-004033-DL2%20-%20Alan%20Smith%20Merseyside%20Fire%20Rescue%20service%20-%20Significant%20Incident%20Report%20-%20Final%20redacted.pdf
  6. ESS News, report of the battery fire at South Korea's National Information Resources Service data centre, Daejeon (26 to 27 September 2025). https://www.ess-news.com/?p=6778
  7. Information to inform Habitats Regulations Assessment for 26/00109/HYB (April 2026), pages 37 to 41. https://www.cardiffidoxcloud.wales/publicaccess/files/9C8F08126A61F9B8DB81386FDA998B34/pdf/26_00109_HYB-INFORMATION_TO_INFORM_HABITATS_REGULATIONS_ASSESSMENT-6375559.pdf
  8. National Fire Chiefs Council, Grid scale energy storage system planning: guidance for fire and rescue services (approved December 2025). https://nfcc.org.uk/our-services/building-safety/grid-scale-energy-storage-system-planning-guidance-for-fire-and-rescue-services/
  9. Welsh Government, Energy Generation and Use in Wales: first combined edition (version 3.2, August 2026). https://www.gov.wales/sites/default/files/publications/2026-08/energy-generation-use-wales-first-combined-edition.pdf
  10. Department for Energy Security and Net Zero, Electricity Supply Emergency Code guidance (April 2026). https://assets.publishing.service.gov.uk/media/69d7b134ad08dc1bc975fa3b/esec-guidance-april-2026.pdf
  11. Response to Consultee Comments, April 2026 (the applicant's summary of the Fire and Rescue Service's response). https://www.cardiffidoxcloud.wales/publicaccess/files/6CDF63AE516EA1726F91C995AD42D4E6/pdf/26_00109_HYB-RESPONSE_TO_CONSULTEE_COMMENTS-6375566.pdf

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