Corre Energy – Written evidence (LES0030)


Corre Energy, a developer of long-duration energy storage (LDES) projects in Europe and North America, is grateful for the opportunity to provide evidence to the House of Lords Technology and Science Committee’s inquiry into LDES as part of a net zero grid. The bulk of available evidence demonstrates that it is highly unlikely that the UK will meet its decarbonisation goals without policies that incentivise the deployment and growth of LDES. Therefore, we submit the following testimony in an attempt to answer the majority of the points raised by the House of Lords Science and Technology Committee’s inquiry.


We note that the UK has an ambitious goal of decarbonising its electricity system fully by 2035 and reaching net zero by 2050. To manage the transition successfully, it must also maintain a reliable and affordable energy supply. Although the UK has increased the proportion of its electricity generated by renewable energy markedly within the last decade, the bulk of its energy needs are still met by fossil fuels. To rectify this situation, the government has set a target of achieving 50 GW of offshore wind generation by 2030 and 70 GW of solar generation by 2035.[1]


As we move towards an energy system that is powered by renewables and simultaneously retire central power plants that are powered by fossil fuels, power plants’ role in providing a stable flow of electricity as a result of their ability to store fuels will disappear. This poses new requirements to the energy system, given that disparities often exist between the intermittent nature of renewable energy generation and periods of demand. Therefore, flexible types of generation (such as LDES), which can be scheduled to meet electricity needs during periods characterised by a lack of wind and sunlight and high demand will become paramount for meeting the UK’s decarbonisation goals in an affordable and secure way.


  1. How much medium- and long-duration energy storage will be needed to reach the Government’s goal of a fully decarbonised power grid by 2035 and net zero by 2050, and by when will it need to be ready?

Our view that LDES will become paramount for meeting the UK’s decarbonisation goals in an affordable and secure way is supported by the National Grid Energy Scenario 2023, which signals a need for LDES, recognising that not only does the UK need to move away from relying on gas to produce and store energy, but also that other forms of energy storage such as batteries will be inadequate as a source of storage during periods of stress and over the longer-term. Furthermore, the scenario estimates that there is a need for 30 GW of storage to reach net zero by 2050[2], and over 50 GW if the UK is to be a leader in the field. Currently there is less than 10 GW energy storage installed capacity[3]. A briefing prepared by the Parliamentary Office of Science and Technology (POST), also supports the National Grid Energy Scenario 2023 claim that there is a substantial shortfall in LDES – a gap that needs to be addressed immediately, given the lengthy permitting, stakeholder consultation and construction timelines that are a characteristic of renewable energy projects. Nor do current permitting processses take into account the uniqueness of utility-scale energy storage projects, which heightens complexity and extend lengthy permitting timelines even further. The need for infrastructure to be able to store electricity generated by renewable sources for use in periods of high demand and low supply is also heightened by the fact that electricity demand is projected to double by 2035 as a result of electification of the transport and building sectors[4]. Therefore, there exists a clear need to increase the amounts of LDES present in the UK.


  1. How sensitive is the amount of storage needed to assumptions about the future balance of supply and demand on the grid?

As presented above, governmental actors highlight the need for LDES in reaching a secure and decarbonised energy system, as do private actors such as McKinsey and supranational actors such as the European Union, regardless of other energy technologies mentioned in the call for evidence. Firstly, fossil fuel generation is incompatible with the UK’s net zero goals and additional generation from nuclear power or gas coupled with carbon capture and storage (CCUS) is extremely costly. While grid interconnectors can play a role in addressing the imbalance between supply and demand, they will only do so if they establish a connection to a market that with a highly secure energy supply. Furthermore, it remains unclear whether there is a desire on behalf of the UK’s neighbours to establish further grid connectors, as evidenced by the denial of the Norwegian government refusal to issue a license for the proposed grid interconnector between the Norwegian and Scottish electricity networks in March this year. Therefore, the UK’s security of supply should not be based around imports, as underscored by the Powering up Britain report,[5] which makes it clear that the ambition is to supply the UK through affordable, home-grown clean energy.


Finally, while the full impact of climate change remains yet to be seen, demand for cooling is projected to triple by 2050. Unless this demand is met sustainably, a vicious cycle will be created, where demand for cooling increases greenhouse gas emissions and temperatures, thereby necessitating even more demand for cooling[6]. This increased demand for cooling, which will also be felt in the UK again points to the need to expand LDES.


  1. Which technologies can scale up to play a major role in storage?

While several storage technologies exist that can play a part in accelerating the path to net zero, we would like to highlight the significant role that compressed air energy storage (CAES) can play in the scale up of storage in the UK.


The basic principle of CAES is to compress air and store it underground in aquifers, depleted fields, or salt caverns, which can be released later to generate electricity. During times of low energy demand, excess electricity from the grid is used to power compressors that compress air and store it beneath the subsurface. When electricity demand is high, the compressed air is released and passed through a turbine, which generates electricity.


The only proven technology that is available at commercial scale in Europe (with the exception of pumped hydro), CAES possesses significant advantages. Firstly, CAES can be applied in a wider range of geographical settings, in the sense that it doesn’t require mountaneous terrain to be viable as hydro does. There is also a sufficient supply of salt deposits suitable for CAES. Secondly, CAES also stores energy for longer periods than lithium-ion batteries, which are only able to store energy for around four hours before the cost becomes prohibitive. Compared to other storage technologies, CAES has the lowest cost on an annualised kWh basis[7]. Finally, it is a proven technology, having previously been tested in large-scale applications, using natural gas in Germany and the US.


These points are supported by Imperial College London’s research, which highlights CAES as one of five key technologies that would be low in cost and environmental impact by 2030 for balancing intermittent renewables on a grid scale. It also emphasises that CAES (as well as pumped hydro) is a key technology for scoring large quantities of energy. Furthermore, their research indicates that a 300 MW CAES facility deployed by 2035 in the UK would provide a system value of £1.35 billion per year[8].


As a specific example of how CAES functions in practice is the Green Hydrogen Hub in Denmark, which is one of the projects Corre Energy is currently developing. Set to commence operations in 2028, the Green Hydrogen Hub will be the world’s first facility to combine large-scale renewable hydrogen production with underground hydrogen storage and compressed air energy storage (CAES).


This is achieved through the construction of an electrolyser facility that is co-located with wind and solar farms. The electrolyser produces large quantities of green hydrogen and and renewable energy is stored in the form of hydrogen and compressed air in two separate underground caverns. The renewable energy can be reused when there is a deficit of green energy, or as a green fuel.


While existing CAES plants use natural gas as fuel during generation, the Green Hydrogen Hub provides a significant innovation to CAES technology, as it will use renewable hydrogen to provide up to 100 pro cent of the fuel required, thereby providing a carbon-neutral CAES solution. The technology is also capable of using any mixture of hydrogen and methane, including green methane. This capability will ensure that a CAES facility can continue to operate at full capacity, even in the event of a temporary shortage of renewable hydrogen.


While an open cycle gas turbine uses 2/3 of its fuel for air compression, CAES uses electricity for air compression. This separation of compression and expansion/ generation functions allows CAES to operate with low fuel consumption and at a very low minimum generation level as required, so it can provide large amounts of energy within seconds at low cost relative to conventional thermal generation plants.


The geography of the UK means it is highly suitable for projects similar to the Green Hydrogen Hub. Research published in the journal of Applied Sciences[9] reveals that significant energy storage capacity exists in the major bedded halite deposits of the UK onshore. In addition, constructing CAES facilities is less contentious than constructing other types of storage, and is accompanied by fewer environmental challenges.


Therefore, we assert that grid-scale LDES projects that consist of hydrogen-fuelled compressed air and hydrogen storage in salt caverns such as the Green Hydrogen Hub represent an affordable way to store large amounts of renewable energy and discharge it quickly back onto the grid when required. They represent a key tool the UK can deploy to meet its decarbonisation goals in a timely and affordable manner without jeopardising its security of supply or relying on imports.


  1. What policy support is currently in place to support deployment of storage technologies? Is it sufficient to support deployment at scale?

There is a substantial lack of policy support for LDES in the UK, which makes it difficult to assess the risk associated with LDES projects and the predictability of revenues. This hampers the ability to develop a solid, investment case for LDES projects. Currently, storage facilities that can provide short duration, rapid discharge, such as lithium-ion batteries, are predominantly rewarded in the UK’s policy framework for energy storage. For example, short duration storage can earn money by providing a frequency response service, which helps to balance the electricity system on a second-by-second basis[10]. However, there are no such provisions for grid-scale LDES facilities that can provide similar services. In addition, National Grid tenders are also of a short-term nature. Therefore, the House of Lords committee could consider whether to incentivise LDES through specific tenders for LDES or in combination with renewable generation.


Unfortunately, current market arrangements limit the potential revenue companies can secure from providing flexibility services over longer durations at the larger grid scale. While storage assets are eligible to participate in the Capacity Market, the current structure of the market does not reward the low-carbon LDES needed to meet demand during periods of low renewable energy generation.


Given that LDES projects have high CAPEX and DEVEX costs, with uncertain revenue streams, the committee could consider how to implement remuneration mechanisms that help establish a solid revenue stream and therefore a secure business case to attract potential investors to fund LDES projects beyond the initial development phase. This would aid greatly in accelerating the deployment of LDES and thereby the fulfilment of the UK’s decarbonisation goals.


Finally, there is an acute need to define storage in the UK energy policy framework, including targets for storage and a definition of storage in the Electricity Act and the Electricity License framework. This would include assessing the current design of the electricity market, so that storage is defined as an independent entity and thereby avoids being subject to energy consumption and production charges (i.e. double charges). Doing so would assist in securing investor confidence and provide guidance for both developers and investors alike on where to deploy storage and concentrate research activities.


  1. How well developed is the UK industry across different storage technologies, such as hydrogen or redox flow batteries? How does the UK compare to global competitors in these industries?

The UK is competitive on a global scale in terms of battery storage. Therefore, we suggest that efforts are made to analyse whether some of the market mechanisms and incentives that have been deployed in the UK to spur the development of battery storage, such as its Energy Storage Demonstration Programme[11] could also be applied to increase the roll-out of LDES.


  1. Beyond the cost of deploying long-duration energy storage, what major barriers exist to its successful scale up (e.g. the availability of a skilled workforce, the ability to construct the necessary infrastructure on time, or safety concerns around new technologies)?

The lack of policy support for LDES as mentioned above is a key barrier to its growth. In addition, as mentioned previously, unfamiliarity with LDES projects as a new asset class means that current permitting processses fail to take into account the uniqueness of utility-scale energy storage projects. This heightens the complexity associated with developing utility-scale energy projects and extends lengthy permitting timelines even further. Efforts to build institutional capacity would be welcomed, including measures to shorten permitting times and establishing clearly defined roles and responsibilities between the different governmental agencies that deal with permitting for LDES and renewable energy projects.


The committee could also consider whether to designate certain areas as strategically important for renewable energy development, and therefore subject to accelerated and streamlined permitting timelines.


In addition, clearly defined processes in regards to local stakeholder consultation and community funding would also reduce uncertainty – both for developers and local residents – and reduce disparities between benefits for local communities, depending on the individual project.


  1. What steps should the Government take now to ensure this storage can come online later in the current decade?

Given the lengthy development and construction timelines for LDES projects, the government needs to act now to incentivise the deployment of LDES. This would include measures listed previously, such as a supportive policy framework, including storage targets and incentives such as remuneration mechanisms that provide predictability of revenues for developers of LDES that they can use to secure financing.


Efforts to simplify permitting processes and build capacity at the institutional level so that LDES projects are not subject to lengthy delays are also a necessary step, as are clearly defined guidelines and processes for local stakeholder involvement and the provision of community benefits.


The committe could also consider some of the recommendations provided by the European Commission’s Recommendation on Energy Storage[12], including the accompanying staff document for inspiration on best practices and ways to facilitate the deployment of LDES.


11 September 2023

[1] Longer duration energy storage (

[2] download (, p. 180

[3] Ibid, p. 146

[4] Net zero and the UK electricity sector | McKinsey

[5] Powering Up Britain - Joint Overview (

[6] The Future of Cooling – Analysis - IEA

[7] United States Department of Energy: Energy Storage Technology and Cost Characterization, July 2019

[8] Grantham Institute, Imperial College London: Which energy storage technology can meet my needs?, 2016

[9] Evans, D.; Parkes, D.; Dooner, M.; Williamson, P.; Williams, J.; Busby, J.; He, W.; Wang, J.; Garvey, S. Salt Cavern Exergy Storage Capacity Potential of UK Massively Bedded Halites, Using Compressed Air Energy Storage (CAES). Appl. Sci. 2021, 11, 4728.

[10] Longer duration energy storage (

[11] Longer duration energy storage (, p.3

[12] EUR-Lex - 32023H0320(01) - EN - EUR-Lex (