To combat climate change, all developed economies have set the goal of carbon-neutrality by 2050. This means securing more energy from renewable sources. Achieving a high proportion of renewable energy production in the UK and other developed countries is only possible with suitable energy storage infrastructure, to bridge periods of low or no power generation from wind or solar energy. Here, Professor Robert Dryfe, explores how Long Duration Energy Storage technologies, like batteries, could solve the challenge and makes recommendations to support their rollout.
- We need affordable, safer and longer-lasting energy storage methods to store the increasing amount of energy produced from renewable sources.
- Research at The University of Manchester is developing new types of redox-flow battery, offering a future-proof solution to renewable energy storage.
- To accelerate provision of battery storage, policymakers must incentivise investment in new technologies and support take up of Local Area Energy Plans.
What are LDES technologies?
Long Duration Energy Storage (LDES) technologies are storage systems that can operate for periods exceeding 10 hours. The UK developed a number of such systems in the mid 20th century, based on “pumped-storage”, where excess electricity is used to pump water uphill into dams, for use at times of the day where electricity is in short supply. Population density, and flat geography, means that such approaches are impossible in England. Advances in battery technology mean that large-scale electrochemical systems have become feasible, at least in the technical sense.
Lithium-ion batteries
The current market leader in most grid-level or domestic energy storage solutions is the Lithium-ion battery (LIB). LIBs have revolutionised personal devices and are the driving force behind electric cars. However, for energy storage on a larger scale, LIBs have certain limitations that need to be addressed to enable the transition to a fully renewable energy-based economy/society:
- Cost: LIBs are expensive as they use scarce minerals, such as cobalt and nickel, with prices of approximately £1M per MWh installed. With present-day technology and economics, LIBs can only store up to 6 hours of energy before they become too costly.
- Fire Risk: LIBs use a flammable electrolyte, limiting their use in certain applications, e.g. at ports or airports: witness the deadly fire at a Korean battery plant in June 2024.
Redox flow batteries
Redox flow batteries (RFBs) could be a less resource-intensive and cheaper solution to this problem, capable of storing energy for 10+ hours. RFBs have existed for decades and are easily scalable: normally consisting of two “tanks”, where the charged electrolytes are stored, this means the power and capacity (energy) stored in the battery can be separated. A large tank, with a small cell (or a small number of cells in the “stack”) gives a lot of energy, but less power; the converse can be obtained with smaller tanks, but a larger “stack”. Large RFBs are being built, for example the recently completed 100 megawatt (power)/400 megawatt hour (energy) system built at Dalian in north-east China. This system, like most of the commercial RFBs to date, is based on vanadium as the “active” metal; vanadium is costly, and rather scarce. These factors have limited the wider penetration to date of RFBs as mass-market energy storage devices.
Our research at The University of Manchester, offers a way to develop lower cost redox-flow batteries. We are developing systems that avoid the need for use of relatively rare materials, such as vanadium. Our work developing “post-vanadium” technology also has the advantage of low flammability and being non-corrosive.
Another key, and expensive, component of current RFBs is the membrane, which separates the two “halves” of the electrochemical cell. Our research, which is at an early stage, is also looking to circumvent the need for the membrane – which will reduce the cost and increase the lifetime of flow batteries. Currently, the capital cost (per megawatt hour) of RFB-based storage is on the order of £250,000-350,000 per megawatt hour: the aim with our technology is to reduce this cost towards £100,000 per megawatt hour.
Commitment to reaching net-zero
The UK’s commitment to reaching net-zero emissions by 2050, and more stringent target of 2035 for decarbonising the electricity system, will require significant changes in domestic and industrial power supplies as these sectors represent a large percentage of overall energy use. A transition to renewables must be accompanied by a transition of technology to large scale battery storage. Consequently, the UK Government should combine its laudable move to renewable electricity with a similar transition to the storage needed to ‘stock’ this renewable energy.
Incentivising investment in new technologies
In the UK, the National Grid has announced a plan to add a further 10 gigawatts of battery storage, across 19 different sites. One of the largest sites already approved is in Greater Manchester, a 1000 megawatt/2000 megawatt hour storage facility, planned for the “Trafford Low Carbon Energy Park”. The battery storage aspect of this facility is relatively short-term (1 hour duration) and based on LIB technology. One issue with large scale LIB storage is the flammability of the components, restricting the scale of cell that can be deployed close to roads or residential areas.
To accelerate the scale and decrease the cost of battery storage, the UK needs to encourage investment in technologies that are capable of longer-duration storage, which in the battery context means developing new types of RFBs that break the current reliance on critical materials such as vanadium. Carbon-based electrode materials, and chemistry based on more common metals is accessible, although further research is needed to optimise these devices. The deployment of smaller scale RFBs should also be considered, capable of supplying both stored power and back-up power to industrial sites, and other important facilities such as hospitals.
A recent consultation by the Department for Energy Security and Net Zero, committed to implementing a framework that would create the environment for investment in long duration energy storage. It included the UK Government’s proposal to introduce a cap and floor scheme for LDES and seeks views on several elements of the approach, including the eligibility criteria, the design considerations, and proposed options for delivering the Powering up Britain Plan. Should the Government progress with these plans it is expected that the consultation will provide revenue certainty for investors by guaranteeing revenue if returns from operating assets drop below the agreed floor. This also offers consumer protection by providing a cap on the revenue that operators can earn, with some or all of the revenue earned over the agreed cap returned to the consumer. To succeed in meeting our storage and net zero targets the government must implement the finalised framework at its earliest convenience, to provide certainty across political cycles. Delays or uncertainty could redirect investment to other countries like Germany, where certainty and opportunity is more readily defined.
Local Area Energy Plans
‘Local Area Energy Plans’ (LAEPs) detail exactly where clean energy generation such as PV and energy storage can be installed to maximise decarbonisation of homes, businesses and industry. Currently around 100 local councils have LAEPs, with Greater Manchester Combined Authority trailblazing, having developed plans for all of its ten boroughs, and being the first at this scale. Participation in LAEPs has not been made a statutory requirement by the central government, though a similar scheme in Scotland has been. There is also no standardised framework for LAEPs, impeding comparisons between plans and benchmarking of progress against net zero targets across a wider geographic scale. By working with local authorities and integrating LDES technology into LAEPs, effective solutions to strategic decarbonisation challenges (e.g. decarbonising domestic/industrial heating) are made possible. Policymakers should therefore consider making LAEPs mandatory and work with stakeholders to develop a funded framework.
