UK’s largest solar farm to power London Transport in green energy deal

The UK’s largest solar farm is to power some of London’s transport network after Transport for London (TfL) signed a 15-year supply agreement.

The Longfield Solar Farm is being built just outside northeast Chelmsford in Essex, and when completed, it could contribute approximately 400 GWh per year to the national grid by the end of the decade. It’s being constructed on land considered to have poor to moderate quality for farming, so the loss of arable land would have a negligible impact on food supply. An onsite battery energy storage system (BESS) will also ensure that when too much energy is being generated, it can be imported off the grid and released when there is demand, thus helping to maintain grid balance and resilience.

The new solar farm will provide approximately 20% of its output to TfL, which is about 80 Gigawatt hours (GWh) of electricity per year, and represents approximately 5% of the 1.6TWh that TfL uses annually.

With the solar farm near Chelmsford, they won’t be running electricity cables from Essex to London, but will use a “sleeved PPA” agreement. That’s where electricity from the solar farm is sent into the National Grid, but is credited to TfL instead of being treated as generic grid electricity. TfL then draws its supply from the National Grid as usual, but through accounting and billing, it’s as if they’re using the solar energy.

Rollo Maschietto, Interim Head of Power at the REA (Renewable Energy Association), said: “This is exactly the kind of leadership we need from major public bodies to unlock investment in clean energy infrastructure. TfL is helping to bring forward large-scale UK solar – the cheapest and quickest form of new electricity generation. The more solar we deploy, the lower bills will be and the less exposed we’ll be to volatile fossil fuel markets. This is a blueprint for how the public sector can get behind the energy transition while supporting green jobs and strengthening our energy security.”

TfL’s long-term Energy Purchasing Strategy is to purchase up to 70% of the total electricity it needs through PPAs, with the remainder mainly through a flexible green tariff. This will contribute to the wider ambition to use 100% renewable source electricity across TfL’s operations by 2030.

TfL signed this 15-year Power Purchase Agreement (PPA) with EDF Renewables, which ensures TfL has a fixed cost for the electricity and guarantees the same for EDF.