Last reviewed 12 July 2016

The imminent closure of all coal-fired power stations and most of the country’s ageing nuclear plant, combined with an expected doubling of electricity demand by 2050, will leave the UK facing a 40–55% electricity supply gap, according to a report from the Institute of Mechanical Engineers (IMechE). Could energy storage help fill the gap? John Barwise investigates.

IMechE report

The IMechE report, titled Engineering the UK Electricity Gap, claims the trend towards more electric heating, electric vehicles and further electrification of railways, coupled with a rise in population, means demand for electricity will continue to rise at a time when the UK power generation sector is in decline.

The report, which is highly critical of government energy policy, argues that there is little focus on reducing electricity demand, following cuts in energy efficiency grants and further cuts in renewable energy subsidies, and that “the UK was on course to produce even less electricity than it does at the moment”. The report’s lead author, Jenifer Baxter, IMechE, added: “Under current policy, it is almost impossible for UK electricity demand to be met by 2025.”

Among the report’s far-reaching recommendations is a call for the UK’s National Infrastructure Commission to “urgently implement the changes necessary across the industry and supply chain to deliver security of electricity supply”, and to invest in “renewables, energy storage, combined heat and power and innovation in power station design and build”.

Balancing act

The UK’s electricity system will need to undergo significant changes in the coming years to fill the energy gap and to ensure electricity supply is available, secure, affordable and low carbon. The Government has introduced a number of measures such as the Capacity Market (CM), covered in last month’s article, Capacity markets — can they fill the energy gap? which allows for additional payments to suppliers for extra sources of electricity at peak demand.

The National Grid, which manages CM, has also introduced a number of “balancing services” such as Demand-side Balancing Reserve (DSBR) which includes payments to large energy users to reduce demand or switch to back-up generation during peak times. Peter Bingham, Senior Manager at the National Grid describes these measures as a “balancing act”.

“The decline in available power means tighter margins, particularly mid-decade, between the ability to generate power and demand at peak times, making our role in matching supply and demand more challenging,” he said.

The latest National Grid initiative, designed to meet that challenge, is Energy Storage which, according to a Technology Innovation Needs Assessment (TINA) from Low Carbon Innovation Co-ordination Group will be vital in the coming decades.

Current storage scenarios do not include storage beyond a limited build of hydro schemes such as the Dinorwig pumped hydropower station in Wales. Known as “TV pickup”, pumped hydro plants provide a fast response to short-term rapid changes in power demand, such as the recent television schedule of England v Wales EUFA cup match when, at half time, the kettle goes on creating a power surge of around 1100 megawatts (MW).

EN&S technologies

The potential benefits of a more comprehensive energy storage programme go much further. Findings from the TINA report indicate that electricity network and storage (EN&S) technologies could play an important role in future energy scenarios, “supporting the deployment of renewable electricity generation, renewable heat, electric vehicles (EVs), and other low carbon technologies”. The report goes on to say that innovation in EN&S technologies could deliver an estimated 7–59 Gigawatts (GW) of grid-connected electricity storage capacity by 2050 and save the UK £4–19 billion in deployment costs. The report also argues that energy storage could help create UK-based business opportunities worth an estimated £6–34 billion to GDP to 2050. “Significant private sector investment in innovation, catalysed by public sector support to overcome barriers and market failures, can deliver the bulk of these benefits while demonstrating strong value for money,” the report concludes.

Battery storage

The National Grid sees energy storage as an essential response mechanism for meeting future electricity demand, given the demise of traditional baseload supplies, such as coal-fired power. Charlotte Grant, Technical Project Manager for the Grid’s SMART Frequency Control programme says battery storage is central to the mix of frequency response services: “A battery storage system can store the energy produced by solar, wind or hydro systems. And previous studies have shown it can play a key role in ensuring system reliability,” she said.

In a deal agreed with the National Grid, energy firm Renewable Energy Systems (RES), has launched one of the UK’s first battery energy storage systems designed to help balance the country’s electricity supply. Adam Sims, Senior Account Manager at the National Grid, said the battery storage system will provide fast-acting frequency response service to the national transmission network. “This innovative technology will enable us to respond to frequency issues in under a second, helping to maintain the integrity of the grid,” he said.


Renewables’ share of electricity generation increased from 19.1% in 2014 to a record 24.7% in 2015 due, in part, to an increase in solar and wind capacity. However, the problem with solar and wind generators is their intermittency, which means they cannot be relied upon to deliver electricity at peak demand. The Renewable Energy Association, which has recently set up its own Energy Storage group sees energy storage as “a key missing piece for the UK’s energy policy”, that can help solve the intermittency problems.

A report from Imperial College London and Carbon Trust says the flexibility of energy storage would help. Funded jointly by Decc, Scottish Government and three major utilities, E.ON, SSE and Scottish Power, the report says: “Storage can be used for ‘capacity firming’ to mitigate fluctuations in output experienced with intermittent renewable energy, particularly solar and wind, thus maintaining the committed level of capacity.” The report also points out that as heating and transport systems are electrified in the coming decades, peak demand will rise sharply, leading to “a significant degradation of generation infrastructure and electricity network assets”, which in turn could increase the cost of system integration; energy storage has the potential to reduce these costs.

The problem for the UK Government is that the share and continued growth in renewables adds yet more volatility to the grid. A study undertaken by Dr Konstantinos Chalvatzis of Norwich Business School, argues that it is now time to start subsidising storage. “We need sufficient storage and more investment in storage systems in order for renewable energy to reach its full potential. Subsidies would encourage investment, which in turn would enable further integration of renewables into the energy sector,” he said.

In a speech to the UK’s Electricity Storage Network earlier this year, Energy Secretary, Amber Rudd, described energy storage as “the most flexible” tools for balancing the UK’s electricity networks. Rudd went on to highlight 24 energy storage projects it is supporting, covering a wide range of electrical energy storage technologies, most of which are led by UK SMEs.

Looking ahead

The research goes on. One of the UK’s largest battery-based energy storage facilities is now connected to the grid as part of new research led by the University of Sheffield. The £4 million facility launched in partnership with E.ON and Uniper will test the possibilities for large-scale energy storage and how to overcome the challenges associated with connecting such technologies to the grid. This is one of three of the largest batteries currently operational in the UK — and the first to use an innovative lithium titanate battery, which is fast to charge and has a long lifetime. One of the facility’s unique capabilities is being able to respond to import or export electricity at short notice — at 4/10ths of a second, it is the fastest of any battery energy storage system in the UK.

Energy storage, as a flexible component of the UK’s electricity supply and demand system, is gathering momentum. However, there are concerns that the current regulatory system for storage is slowing progress. A report on Low Carbon Network Infrastructures published in June by the Energy and Climate Change Committee, claims there are at least two regulatory barriers to storage deployment. “First, storage is classified and licensed as generation: this limits network companies to operating no more than 100MW of storage. Second, storage is liable for BSUoS charges, for which they are charged twice — once for ‘consuming’ the electricity they store, then for supplying it back to the grid — costing UK storage approximately £14.9 million annually.” They are also double-charged the Climate Change Levy (CCL), the report says.

In its summary, the Committee report concludes that “the current regulatory conditions for storage are hindering its development” and has therefore asked the Government to proceed with its storage consultations “with a sense of urgency,” while also “exempting storage installations from balancing charges, and from all double-charging of network charges”.

The case for energy storage as a flexible, low carbon source of electricity that can help to balance the UK’s sometimes erratic supply and demand curve, is overwhelming. The opportunities for energy cost saving and potential job prospects are also convincing. Improving the regulatory framework to stimulate further investment in energy storage in the grid, remains a challenge.