In February, the Department of Business, Energy and Industrial Strategy (BEIS) unveiled nearly £7 million in funding for a vast range of longer-duration energy storage projects.
The funding falls into two categories within the Longer Duration Energy Storage Demonstration Programme; Stream One includes projects for technologies that are close to demonstration, and Stream Two which is designed for “first-of-a-kind” prototype projects.
Robin Lane, commercial director at Stream One winner Gravitricity, said the funding was “extremely significant”.
“The application process was highly competitive and the due diligence process rigorous, so it’s a vote of confidence in us and underpins what we are saying – that gravity energy storage has a part to play in our future energy grid.”
There are five projects which were awarded funding in Stream One, including a membrane free green hydrogen electrolyser, gravity-based energy storage, vanadium redox flow battery, advanced compressed air energy storage (A-CAES) and a bundled solution of pressurised seawater and compressed air.
A report from Aurora Energy Research in February suggest up to 24GW of LDES – defined as that with a duration of four hours or above – could be needed to effectively manage the intermittency of renewable generation in line with goals of operating a net zero electricity system by 2035. The technologies supported within the two streams of BEIS’s competition could be leading contenders to fill this emerging sector.
Current±, took a look at a few of the winning Stream One technologies being explored as potential LDES solutions.
Avoiding curtailment with green hydrogen and salt caverns
Northern Irish company B9 Storage’s Ballylumford Power-to-X green hydrogen project was one of the Longer Duration Energy Storage Demonstration Programme winners. It is looking to use electrolyers to provide controllable electrical load, which can help balance wind farms, avoiding curtailment.
The project will see a 20MWe membrane free electrolyser deployed inside a repurposed building at Ballylumford in Larne, Northern Ireland.
“The hydrogen will be distributed in a dedicated transmission pipeline and stored underground in a local salt cavern system for later use as carbon free fuel in both the transport and power generation sectors,” B9 Storage’s managing director David Surplus explained to Current±.
“The latter application will involve firing trials of a relocated 20MWe Open Cycle Gas Turbine (OCGT) typically used for electricity generation on oil and gas platforms. We expect to see successful fuel switching reach >70vol% H2 blend in natural gas.”
Additional OCGT firing trials will be carried out with oxygen being added to the combustion air, to tap into the benefits of Oxygen Enhanced Combustion for fuel efficiency, he added.
The results from the project will then be used to inform future electrolyser deployment, as well as providing curtailment free connection of offshore wind farms at Ballylumford.
“We are continuing to grow our team at B9 with a focus on investing time and money into developing the supply chain solutions that we will be needing to support the 1GWe installed capacity by 2030 target in Northern Ireland,” added Surplus.
The potential of green hydrogen for both curtailment avoidance and LDES has drawn increasing attention recently, with other companies such as Octopus Energy, bp, ScottishPower and Macquarie amongst others in the UK investigating the potential of the technology.
Vanadium flow: a ‘radically different’ battery
Chemical storage is also commanding an increasing amount of attention, as the UK’s share of renewables continues to grow. Invinity’s vanadium flow battery (VFB) technology is one of the technologies that could potentially step up to help balance surging intermittent generation.
“To be included as one of the leading participants in a programme whose explicit purpose is to underline the important role longer duration energy storage technologies will play in our increasingly low-carbon energy system is a great honour,” said Matt Harper, CCO at Invinity.
“This is the second project we are working on with Pivot Power, part of EDF renewables, having delivered a 5 MWh VFB to their Energy Superhub Oxford project last year.”
Its Vanadium Flow Battery Longer Duration Energy Asset Demonstrator project will see a 40MWh installation developed, which will be used to show how VFBs can improve the operation and economics of grid-constrained solar generation sites.
VFBs are “radically different” from lithium-ion batteries, said Harper, as they were always designed to seve the electric grid, as opposed to emobility or telecommunications.
“By storing energy in a liquid electrolyte containing the element vanadium, VFBs are able to cycle continuously without degrading, giving them the ability to deliver high-throughput service to the electric grid over hours per day for decades of use,” he added.
“That makes VFBs ideally suited for filling in the “missing hours” where renewable generation – and in particular, wind and solar power – falls short. In addition to making solar and wind power available on demand, VFBs are also capable of fast response times to provide high-throughput grid services such as dynamic regulation.”
Additional benefits of the technology include being non-flammable, not suffering from thermal runaway, and operating best at higher temperatures, reducing the need for additional cooling.
There a number of benefits to running at a higher temperature like this, the company said, including mitigating the kind of cooling system failure seen at US-based energy storage facility Moss Landing, which kept it offline for a number of months following a sprinkler system releasing water onto battery racks.
“As the energy transition progresses, we are seeing market needs evolving,” finished Harper. “With intermittent wind and solar power providing a proportion of our total energy mix, technologies that can deliver multiple hours of energy to support the grid, every single day, 365 days a year clearly have tremendous and increasing value. This is beginning to generate tremendous market demand for solutions based on emerging technologies such as flow batteries.”
Putting gravity to work
Along with VFBs and hydrogen storage, one potential solution to the longer duration storage challenge is gravity energy storage. Scottish company Gravitricity has been developing such a system for a number of years now, and in 2021 completed a 250kW demonstrator, which operated in Edinburgh throughout the summer.
Winning funding through BEIS’s Duration Energy Storage Demonstration Programme will allow the company to continue to configure the technology, focusing on a single weight and height power system in the short-term.
“A major challenge for early-stage technology, particularly hardware technology (as opposed to software), is always financing – ie the first project will be tens of millions of euros, and financiers are understandably wary of funding projects before the technology has been proven,” Gravitricity’s Lane told Current±.
“We believe the long-term market for energy storage will be absolutely massive and investors need to buy into this long-term view. Our technology has relatively high upfront costs but then very low operating costs and a lifetime of hundreds of thousands of cycles / many decades. Longevity really matters for energy storage assets which will become a key component of a country’s grid infrastructure.”
The technology works by raising weights located in a deep shaft when there is abundant green energy on the electricity system, and then releasing them when energy is required. The weights and the depth of the shaft vary the capacity of the system, for the demonstrator for example, the company ran a series of tests that involved raising and lowering two 25-tonne weights.
Given the success of this demonstrator, Gravitricity secured new project support led by the European Investment Bank for a full scale 4-8MW project in a former mine shaft, although the final site is yet to be chosen.
The two key benefits to the company’s solution are longevity and speed of response, it said. While pumped hydro – another solution that utilises gravity – provide bulk storage, the response with which it can react is slow, and its application limited by geographical storage, the company added.
Similarly, while lithium-ion and other batteries offer fast responses and good efficiency, they do not have the cycle life to work as grid infrastructure.
“For longevity/durability and locational flex Gravitricity is great,” continued Lane. “Our mission is to produce a technology that is durable and robust enough to cope with hundreds of thousands of cycles in all environments – because the challenge of energy storage is just as significant in Africa/Asia as it is in Europe or North America, and many different forms of energy storage will be required.”
Going forwards, the company is also looking to use its purpose-built shafts to store hydrogen and seasonal heat storage, further improving its business case.