The UK’s journey to net zero emissions hinges on a fundamental shift in our energy landscape. In fact, projections show that the electrification of heating, transport and industry is expected to result in a rapid increase in demand, which means that by 2050, we could be using twice as much electricity as we do today.
This is a huge undertaking. In this shift towards an electrified energy system, greater amounts of renewable sources, like wind and solar, must be plugged into the grid. Alongside this, the UK will need to build five times more electricity transmission infrastructure over the next seven years than has been constructed over the past three decades, to meet rising demands.
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However, with grid infrastructure often taking five to fifteen years to plan and permit, in comparison to one to five years for new renewables projects, the current speed of grid build-out is nowhere near fast enough to manage an effective energy transition.
We certainly still need new poles and wires but transmission-connected batteries can be part of the solution, offering a game-changing solution for grid stability and decarbonisation.
Transmission-connected batteries are large-scale energy storage systems directly linked to the high-voltage transmission network. Unlike behind-the-meter batteries serving individual buildings, these powerhouses operate at a national level, providing crucial balancing services to the entire grid.
Energy Superhub Oxford: the first transmission-connected battery project
An innovative model, with a transmission-connected battery at the heart, is Energy Superhub Oxford (ESO) – a project that provides an example for cities looking to expand green transportation, energy, and heating simultaneously, without overburdening the grid.
Spearheaded by EDF Renewables UK, ESO installed the UK’s first transmission-connected battery, coupled with one of Europe’s most powerful EV charging networks – supporting Oxford’s ambition to reach net zero by 2040.
ESO’s battery is a unique asset in several ways: it was the first battery in the UK to be connected to the National Grid transmission network and it is the first hybrid battery of its type anywhere in the world, with both a lithium-ion and vanadium flow battery playing a part in the project.
The 52MW hybrid transmission-connected battery provides balancing services such as frequency response to National Grid, enabling improved flexibility and ultimately greater amounts of distributed renewable generation on the grid of the future.
ESO has also become a key piece of the puzzle in scaling up green transport in Oxford, with a 7km private cable network offering 10MW of power directly from the UK’s overhead electrical network. This has allowed companies like Oxford Bus Company to bring a brand-new fleet of 104 electric buses to the city– a major win for air quality for Oxford residents.
This is groundbreaking territory for the battery storage industry, opening up the transmission network to other battery storage developers, who have since been applying to National Grid for similar connections.
Their role in the market
At the outset of ESO, it was expected that the transmission-connected battery would spend most of its time trading in the energy markets, and this would deliver most of the revenues, with a smaller contribution from ancillary services like Firm Frequency Response (FFR).
In reality, however, frequency response services have provided the majority of the project’s revenues. This was primarily due to the introduction of new services, particularly dynamic containment (DC), that resulted in a new market for these batteries.
Additionally, since ESO’s inception, the energy crisis has resulted in very high prices for the provision of non-battery assets, as well as high price volatility. In this environment, the battery has provided both back up in significant grid stress events, and reactive power.
In recent years, concern has been raised by the industry that BESS was being consistently overlooked in the Balancing Mechanism (BM), with skip rates for large-scale batteries at 80% on average between November 2022 and May 2023. Since the Electricity System Operator launched the Bulk Dispatch tool in January of this year, there has been significant improvement in weekly dispatch volume for batteries in the BM. Though Bulk Dispatch has certainly improved things for batteries, the Electricity System Operator has some way to go, with the introduction of the 30-minute dispatch rule in the BM and Fast Dispatch set to further improve battery uptake in the BM.
Change is needed to achieve targets
The future of a decarbonised UK demands a smarter and more flexible grid. Transmission-connected batteries are not just a supporting act – they are a vital technology that can help accelerate the UK to a net zero future.
However, the UK cannot fully realise its net zero potential without action from the top. ESO highlighted that in order to ensure successful integration of transmission-connected batteries, we must create an agile and responsive market structure. This demands a regulatory environment that fosters innovation and empowers stakeholders to adapt to the evolving needs of the electricity system – paving the way for more efficient and effective grid management.
Transmission capacity needs to be vastly expanded, and Ofgem empowered to enable anticipatory grid investment. With delays in getting projects online becoming longer, National Grid and DNOs need to be held to promised timelines.
The connections queue now stands at 701GW with estimates this could rise to 800GW by the end of 2024. We welcome the work that is currently underway to reform the transmission connections process (with implications for both transmission and distribution connected projects), with the aim of reducing the existing queue and reforming the process for new applicants.
However, a great deal of uncertainty remains surrounding the infrastructure needed to deliver connections and the specifics of the reformed connections process currently under development and its implications for developers of BESS.
Only with a regulatory environment that supports the growth of renewables can we deliver a smarter and greener grid.
