A data centre in east Cardiff that may have to make its own power for five years is now waiting on Welsh ministers. The Welsh government has issued a holding direction on the application by developer Curtis Hall for the Cardiff East Park and Ride site near Llanrumney, the BBC reported on 16 October. The direction stops Cardiff Council from granting permission while ministers decide whether to take the decision themselves. The council says the application is still under consideration and will go to a planning meeting at a later date.
Waiting for 150 MW
The data centre needs a 150 MW grid connection, which may not come before 2030 to 2034. To bridge the gap, the plans include a temporary ancillary energy centre of up to 49.9 MW: five gas turbines, a steam generator and two standby gas turbines, running from July 2028 for about five years. Once the grid arrives, around 40 diesel generators would provide backup.
The figure of 49.9 MW has drawn attention because energy plants of 50 MW and above need Welsh government consent. The developer denies the limit was chosen to avoid that. It calls the gas turbines a worst case used to set the upper bound of emissions and noise in the assessment, says the technology is not fixed and mentions fuel cells as an option, and says the energy centre would not be needed at all if the connection came on time.
Generator Testing Became the Argument
Much of the opposition is about the diesel sets rather than the turbines. Herald.Wales reported last month that the first air quality assessment, from December 2025, warned that running the backup generators for more than 30 minutes would probably breach the short-term NO2 objective. A revised assessment in April changed the testing regime so that each generator is tested on its own every week, and found the result acceptable. Two Plaid Cymru Members of the Senedd say the revised model still shows up to three breaches a year at nearby homes and a primary school. The developer says the scheme meets national standards, and that it modelled a 72-hour grid outage it puts at about once in ten years.
Objections have come from almost all local Members of the Senedd, a Welsh government minister, the local MP, a Cardiff Council cabinet member and Friends of the Earth Cymru. The Welsh government plans to publish a policy on data centres before the end of 2026.
Where Sites Like This Get Stuck
Two things in this case are turning up across Europe. Grid dates now run so far out that developers plan years of on-site generation first, and that puts a power plant into what began as a building application. And once a council's air quality officers look closely, the routine test schedule of the backup generators becomes a planning condition, not a maintenance detail left to the operator.
A test regime that has to change during planning means the commissioning plan and the maintenance contract change with it. Better to write it with the operations team before the air quality model is run, and to check that the exhaust treatment and stack positions the model assumes are the ones that will actually be built.
Sources: BBC (via Yahoo News), Herald.Wales