Tag: Cruachan Power Station

Expanding pumped storage hydro to support the UK’s transition to Net Zero

9 April 2024

Opinion

By Steve Marshall, Drax’s Development Manager 

In July 2023, Drax received development consent from the Scottish Government to build a new 600MW underground pumped storage hydro plant at its existing Cruachan facility in Argyll, which will more than double its electricity generating capacity.

Whilst a major milestone for the Cruachan expansion project, the right support is still needed from the UK Government to facilitate its development and we’re pleased to see some positive progress has recently been made.

During a visit to Cruachan Power Station following last year’s announcement of development consent, Scotland’s First Minister, Humza Yousaf, called on the UK Government to “provide an appropriate market mechanism” for projects including Cruachan’s expansion. Mr Yousaf also wrote to the Prime Minister urging him to take action so developers can have the certainty required to build a new generation of pumped storage hydro plants.

In order to incentivise investment for new-build pumped storage hydro plants, new financial mechanisms are needed to enable investors to back capital-intensive, long-length construction projects that will save consumers and the grid millions. The current lack of these frameworks is a key reason why no new pumped storage hydro plants have been built in the UK since 1984.

Growing the UK’s pumped storage hydro capacity is crucial to integrating more wind and solar power onto the energy grid, enhancing the nation’s energy security while tackling climate change. Pumped storage plants act like giant water batteries by using reversible turbines to pump water from a lower reservoir to an upper reservoir which stores excess power from sources such as wind farms when supply outstrips demand. These same turbines are then reversed to bring the stored water back through the plant to generate power when the country needs it.

At the start of this year, the UK Government announced that it has selected a cap and floor regime as its preferred investment framework for new large-scale, long-duration electricity storage projects, which is a huge step towards making a new generation of pumped storage hydro plants a reality.

What is a ‘cap and floor’ mechanism?

A cap and floor mechanism works by setting an upper and lower revenue limit an operator participating in the mechanism can earn from a particular asset. The lower revenue limit, or ‘floor’, is the guaranteed minimum amount of revenue that a generation asset can earn. If a generation asset does not generate enough revenue from its operations, this gets topped up to reach that floor level from the system operator using an allocated budget. At the other end of the limit, the ‘cap’ is the maximum amount of revenue the operator can earn from the asset. In cases where an asset’s revenue exceeds the cap, a proportion of the funds earned above the cap threshold are paid back to the system operator and used to reduce the cost of using the system for customers.

The cap and floor mechanism enables private investors in long-duration electricity storage projects, such as Drax’s planned expansion of Cruachan, to have a better degree of confidence by alleviating a significant amount of risk and uncertainty around whether they can recover their costs. Having a predictable revenue stream makes it more likely investors and lenders will support projects with high upfront capital costs. As well as de-risking investment and providing better value for money to customers, a cap and floor mechanism also rewards availability and efficiency, as operators are still exposed to opportunities between the cap and the floor. This includes participating in a number of different markets like the ancillary services markets, where Cruachan is able to earn revenue by providing critical inertia and stability to the grid, ensuring the safe and stable operation of the electricity system. Similarly, wholesale market arbitrage allows Cruachan to respond to price signals both in times of low/high generation and peak demand. These market opportunities incentivise operators to optimise their operations to generate revenue towards the highest end of the cap thresholds, driving innovation and efficiency in the sector. This efficiency is not only beneficial for the operators but also for the overall National Grid, bolstering the stability and reliability of the UK’s electricity supply. This enables projects to benefit from competitive market opportunities and provide services in response to price changes and benefit the consumer by providing critical services that the system needs at a competitive price.

What does this mean for Drax’s Cruachan expansion project and what are the next steps?

The UK Government’s consultation on designing a policy framework to enable investment in long-duration electricity storage ran from 9 January to 5 March 2024, and is now closed.

The consultation proposal of a cap and floor is very positive news for Drax’s planned Cruachan expansion, as it will provide the project with a route to market once the mechanism is in place. Without it, the significant upfront capital expenditure and revenue uncertainty would remain a barrier to investing in the project.

One of the most immediate benefits of pumped storage hydro is that it provides extremely quick back-up during periods of peak demand. For example, when deployed alongside intermittent renewables like wind or solar power, Cruachan can step in to store excess energy and provide it back to the grid when the wind doesn’t blow and the sun doesn’t shine. This reduces the waste and cost to customers associated with renewable curtailment.

With the Government’s ambition to deliver 50GW of offshore wind by 2030 as part of its Net Zero targets, it is in the interest of both Government and the grid to ensure enough storage is available by this point to manage the inherent intermittency of this technology. Pumped storage hydro projects have long construction times, over 5 years in the case of the planned Cruachan expansion. This means that delivery of the mechanism in the near-term is critical to ensuring that it’s available to support the electricity system in the early 2030s and beyond.

What are the benefits of pumped storage hydro for the UK?

A report by Scottish Renewables and BiGGAR Economics recently found that six projects currently under development in Scotland, including the Cruachan expansion project, will:

  • More than double the UK’s pumped storage hydro capacity to 7.7GW.
  • Create almost 15,000 jobs.
  • Generate up to £5.8 billion for the UK economy by 2035.

During its construction phase, the Cruachan expansion is projected to provide up to £73m GVA and over 150 jobs in Argyll and Bute. Across Scotland this increases up to £260m GVA and over 500 jobs, which is a total possible UK benefit of over £470m GVA added to the economy and over 1,100 jobs supported amongst the wider supply chain and indirect local area support.

Pumped storage hydro can also provide a number of extra balancing and ancillary services outside of energy storage and generation, across multiple different markets. These markets play a critical role in ensuring the safe and stable operation of the electricity system by providing grid inertia, voltage control frequency response and restoration services, alongside quick flexible response to price signals both in times of low and peak demand. Being able to support wider services in this manner means pumped storage hydro offers better value for money to both investors and consumers, with an Imperial College study finding that it could help to reduce total system costs like these by between £44m and £316m per annum by 2050.

We look forward to working constructively with the UK Government and other stakeholders to help deliver a policy environment which secures investment, strengthens our energy security, and delivers for consumers. We’re ready to move mountains to tackle climate change.

Find out more about Cruachan’s plans for expansion here: drax.com/cruachan2

The next PM must move fast to unlock investment in long duration energy storage

2 August 2022

Opinion

For many years energy security was an issue resolved by complex, continent-wide gas pipelines which stretched from Russia into the heart of Europe.

We now know this reliance on Russian gas didn’t strengthen Europe’s energy security – in fact it weakened it.

The UK is less reliant on foreign gas than many countries in Europe in part due to the renewables revolution which has transformed our energy system over the last decade.

The rollout of biomass, wind and solar power has enabled the UK to decarbonise its power grid at a faster rate than any other major economy. And in order to reduce energy bills in the years ahead we need to have more clean, green, renewable power, which is generated in the UK for the UK.

Getting more green energy onto the grid can only be achieved through partnerships between government and private companies. For businesses like Drax, that means having the right policies now, to make large-scale investment decisions for the future, in vital green energy technologies like pumped storage hydro and bioenergy with carbon capture and storage (BECCS).

Drax has submitted planning applications for two major infrastructure projects designed to deliver both of these vital technologies in the 2020s. They form part of a £3bn investment strategy which Drax stands ready to implement this decade, underlining the company’s significant role as a growing, global business at the heart of the green energy transition.

Alongside strengthening the UK’s long-term energy security, these projects will support thousands of jobs and provide a real opportunity for economic growth.

Engineers at Cruachan Power Station

We aim to double the capacity of our Cruachan pumped hydro storage facility in Scotland, supporting energy security and further decarbonisation of the grid, at lower costs.

Over the last two years, due to bottlenecks on the transmission system and a lack of energy storage capacity, enough wind power to supply 800,000 homes each year with renewable electricity, went to waste.

As household bills and global temperatures continue to rise, we can’t afford to let renewable power go to waste like this. We need more storage to harness the wind power available now, as well as the increased capacity being developed the coming years.

The only proven grid scale technology that can store vast quantities of energy for long durations is pumped storage hydro. Sites like Cruachan act like giant water batteries, using excess power from the grid to pump water to an upper reservoir where it is stored, before re-releasing it to generate electricity.

While the UK’s policy and market support mechanisms have evolved to support new build renewables, the current framework isn’t suitable for pumped storage projects that can have a lifespan of many decades.

Drax’s plans would enable more homegrown renewable power to come online to strengthen the UK’s energy security and lower carbon emissions. This additional capacity could be available within eight years.

To secure private investment in these projects, get shovels in the ground and work underway, developers need to know the policy environment they will be operating in.

Abandoning or delaying net zero will not save the country money, it will increase our reliance on foreign gas, leaving households at the mercy of international markets which no UK government can control.

Find out more about Cruachan 2 here.

In Scotland alone there is more than 4.3 GW of storage projects in planning or awaiting construction – this is enough capacity to power around three million homes.

Drax, alongside the developers of some of these other projects, has put forward plans for policies which would create the certainty needed to incentivise investment and kick start work to build the storage capacity this country needs for energy security.

These include introducing a cap and floor regime – the same support mechanism which was instrumental in the successful roll-out of interconnectors in Britain.

I urge the new Conservative Party leader to make the government’s response to these proposals a priority, as part of the package of measures needed to bolster the UK’s long term energy security and to bring the longer-term cost of energy down.

With the right policies to unlock investment, the UK can lead the world in energy storage technologies which are urgently needed to keep the lights on, cut carbon emissions and keep us on track to reach net zero.

This article was first published by Business Green. 

Getting Britain ready for the next generation of energy projects

15 July 2022

Power generation

Key takeaways:

  • As the UK continues to expand its renewable capacity the cost of curtailing wind generation at times of low demand is increasing, adding £806 million to bills over the last two years.
  • Curtailment costs arise from the grid paying to turn down generation due to energy balancing or system balancing issues.
  • Long-duration storage, such as pumped storage hydro, offers a way to absorb excess wind power, reducing the cost of keeping the system balanced.
  • Drax’s plans to expand Cruachan Power Station would increase the amount of excess power it can absorb from 400 MW to over one gigawatt, and rapidly deliver the same amount back to the grid when needed.
  • New financial mechanisms, such as a cap and floor regime, are needed to enable investors to back capital-intensive, long-term projects that will save consumers and the grid millions.

Meeting big ambitions takes big actions. And there’re few ambitions as big, or as urgent, as achieving a net zero power sector by 2035.

This energy transition must mean more low carbon power sources and fewer fossil fuels. But delivering that future requires new ways of managing power, balancing the grid and a new generation of technologies, innovation, and thinking to make big projects a reality.

As the system evolves and more renewables, particularly wind, come online, the UK is forecast to need 10 times more energy storage to deliver power when wind-levels drop, as well as absorb excess electricity when supply outstrips demand, and to maintain grid stability. Pumped hydro storage offers a tried and tested solution, but with no new long-duration storage projects built for almost 40 years in the UK, the challenges of bringing long-term projects to fruition are less engineering than they are financial.

Drax’s plan to expand Cruachan Power Station to add as much as 600 megawatts (MW) of additional capacity will help support a renewable, more affordable, net zero electricity system. But government action is needed to unlock a new generation of projects that deliver electricity storage at scale.

Reigning in excess wind power

Wind is the keystone power source in the UK’s renewable ambitions. Wind capacity increased from 5.4 GW in 2010 to 25.7 GW in 2021 – enough to provide renewable power for almost 20 million homes – and the government aims to increase this to 50 GW by 2030.

However, wind comes with challenges: the volume of electricity being generated must always match the level of demand. If there is a spike in electricity demand when there are low wind-levels, other technologies, such as electricity storage or carbon-emitting gas power, are required to make up the shortfall.

Conversely, if there is too much wind power being generated and not enough demand for electricity the grid often has to pay windfarms to stop generating. This is known as wind curtailment and it’s becoming more expensive, growing from £300 million during 2020 to more than £500 million in 2021.

An independent report by Lane Clark & Peacock (LCP), by Drax, found that over the last two years curtailing wind power added £806 million to energy bills in Britain.

There can also be a carbon cost to curtailing wind power. As more intermittent renewables come onto the system the grid can become more unstable and difficult to balance. In such an event the National Grid is required to turn to fossil fuel plants, like gas generation, that can deliver balancing and ancillary services like inertia, voltage control and reserve power that wind and solar can’t provide.

“It’s lose-lose for everyone,” says Richard Gow, Senior Government Policy Manager at Drax. “Consumers are paying money to turn off wind and to turn up gas generation because there’re not enough sources of ancillary services on the system or renewable power can’t be delivered to where it’s needed.”

“Curtailment costs have spiked this year because of gas prices, and while they might dip in the next two or three years, curtailment costs are only ever going to increase. If there’s wind power on the system without an increase in storage, the cost of managing the system is only going to go up and up.”

Source: the LCP’s ‘Renewable curtailment and the role of long duration storage’ report, click to view/download here.

The proposed Cruachan 2 expansion would help the grid avoid paying to turn off wind farms by increasing the amount it would be able to absorb from 400 MW to over 1,000 MW, and rapidly deliver the same amount of zero carbon power back to the grid should wind levels suddenly drop or the grid need urgent balancing.

Adding this kind of capability is a huge engineering project, involving huge new underground caverns, tunnels and waterways carved out of the rock below Ben Cruachan. However, the challenge in such a project lies less with the scale of the engineering than with its financeability.

From blueprints to real change

The original Cruachan Power Station’s six-year construction period began in 1959. The work of digging into the mountainside was carried out by a team of 1,300 men, known affectionately as the Tunnel Tigers, armed with hand drills and gelignite explosives in an era before modern health and safety practices.

Engineer working at Cruachan Power Station

Expanding Cruachan in the 21st century will be quite a different, and safer process, and one that’s practically, straightforward.

“There is no reason why we physically couldn’t build Cruachan 2,” says Gow. “Detailed engineering work has indicated that this is a very feasible project. There’s no technological reason or physical constraint that would prevent us. It has a large upfront cost, and requires drilling into a mountain, but the challenge is much more on the financial, particularly securing the investment, side of the project.”

Pumped storage hydro facilities today generate their revenues from three different markets: the capacity market, where they receive a flat rate per kilowatt they deliver to the grid; the wholesale and balancing market, where they buy power to store when it’s abundant and cheap and sell it back to the grid when it’s needed, more valuable and used to support the Electricity System Operator in matching supply and demand on a second-by-second basis; and through ancillary services contracts, dedicated to specific stability services.

These available markets present challenges for ambitious, capital-intensive projects designed to operate at scale. With the exception of the capacity market, revenues from these markets are often volatile and difficult to forecast, with no long-term contracts available.

Sourcing the investment needed to build projects on the scale of Cruachan 2 requires mechanisms to attract investors comfortable with long project development lead times that offer stable, low risk, rates of return in the long-term.

Cap and floor

An approach that can provide sufficient certainty to investors that income will cover the cost of debt and unlock finance for new projects is known as a ‘cap and floor’ regime.

With cap and floor, a facility’s revenues are subject to minimum and maximum levels. If revenues are below the ‘floor’ consumers would top-up revenues, while earnings above the ‘cap’ would be returned to consumers. This means investors can secure upfront funding safe in the knowledge of revenue certainty in the long term, whilst also offering protection to consumers.

Such an approach won’t attract investors looking to make a fast buck, but the vital role that it could play in the ongoing future of the UK energy system offers a long-term, stable return. At the same time, the system would save both the grid and energy consumers hundreds of millions of pounds.

The cap and floor system is also not unique, with a similar approach currently used for interconnectors, the sub-marine cables that physically connect the UK’s energy system to nearby countries allowing the UK to trade electricity with them. This means investors are already familiar with cap and floor structures, how they operate and what kind of returns they can expect.

“It’s not just pumped storage hydro that this could apply to,” explains Gow. “There are other, different large-scale, long-duration storage technologies that this could also apply to.”

“It would give us revenue certainty so that we can invest to support the system and reduce the cost of curtailment while ensuring consumers get value for their money.”

The Turbine Hall inside Cruachan Power Station

Cruachan was originally only made possible through the advocacy and actions of MP and wartime Secretary of State for Scotland Tom Johnston. Then it was needed to help absorb excess generation from the country’s new fleet of nuclear power stations and release this to meet short term spikes in demand. Today it’s renewable wind the system must adapt to.

For the UK to continue to meet an ever-changing energy system the government must be prepared to act and enable projects at scale, that bring long-term transformation for a net zero future.

Cruachan Power Station: Protecting biodiversity while generating power

1 April 2022

Sustainable business

Key points:

  • The Scottish Highlands are home to a wide variety of landscapes, with a wealth of biodiversity that must be preserved.
  • Cruachan pumped storage hydro station sits within Ben Cruachan and has operated for nearly 60-years without damaging wildlife.
  • Regular surveys and reporting allow Drax to understand the health of different fauna and species over time.
  • It’s promising that even species of bird and insects that are declining in other parts of the UK are regularly spotted around Cruachan.
  • The expansion of the power station has required and will continue to need careful assessment of the area’s biodiversity to minimise any impact the project could cause.

The Scottish Highlands are home to some of the UK’s most stunning natural wonders. From dramatic plunging lochs to the craggy, ice capped Munros, the varied landscape holds some of the most biodiverse areas in the UK. The region’s fauna ranges from red deer to golden eagles, while its flora includes the ancient oak and moss-covered forests that make up the ‘temperate rainforest’ of the Atlantic coast.

Preserving these landscapes and the life that thrives in them is crucial to both the environment and economy of the region. It’s the job of Roddy Davies, Health, Safety, and Environmental Advisor at Drax’s Cruachan Power Station to ensure operations at the site do not damage the natural environment.

“This is a very biodiverse, rich environment. There are a lot of different species, a large variety of natural habitats and plant life,” says Davies. “It’s good that we can say we’ve operated here for nearly 60 years, and all of that is still there. It’s testament that we don’t have a demonstrable negative effect on the wildlife that lives around us.”

Source: Blue Leaf Nature

Energy storage inside a mountain

The pumped storage hydro station sits a kilometre inside Ben Cruachan, a Munro peak in the Western Highland region of Argyll and Bute. It’s not an area you would normally associate with power generation, but it’s perfect for pumped storage hydro. The site has two bodies of water at differing elevations, Loch Awe at the bottom and a reservoir at the top allowing Cruachan to generate power when it’s needed, as well as absorb electricity when there is an excess on the grid by pumping water back up the mountain. Storing it until power is needed and helping to keep the grid balanced.

The subterranean nature of the power station means the massive machinery, including the four reversible turbines, and the heat and noise they generate, is hidden underground.

Features on the surface are limited to a few buildings by the entrance tunnel at the banks of Loch Awe, and the dam which contains the upper reservoir on the slopes of Ben Cruachan, as well as several pylons and cables transporting electricity. Even the 316-metre buttress dam takes the landscape into account.

“When Cruachan was built in the ’50s and ’60s, the visual impact of it was very much in the minds of the people who built it and the authorities who approved it. The dam is almost impossible to see from a public place,” explains Davies. “Our presence on the surface is very limited. All the busy goings-on are underground. There’s lots of noise underground, but it doesn’t travel outside.”

Ensuring that the area surrounding Drax’s operation continues to function without damaging the surrounding environment is an ongoing process. Davies deploys annual biodiversity surveys and reporting that gives Drax over a decade of information and analysis to help identify trends.

The wildlife of Ben Cruachan

The Cruachan Power Station Biodiversity Survey for 2021 is the 11th completed by Blue Leaf Nature, a biodiversity service provider. The comprehensive report highlights the incredible diversity of fauna surrounding Cruachan, some of which are declining in other parts of the country.

While the majestic red stags found in other parts of the Highlands are extremely uncommon around Cruachan, 2021 was a particularly exciting year for other types of large mammals. Pine martens – a cat-sized relative of the weasel – are relatively common, appearing alongside red squirrels, red foxes, and otters. Badgers were also added to the site’s list of species for the first time.

Source: Blue Leaf Nature

Mammals, however, are exceeded by the range of birds found around Cruachan, with 53 different species spotted in 2021. Of these, 17 species appear on the Birds of Conservation Concern Five’s red list, the highest threat status to the UK’s bird population, including the Ring Ouzel, Yellowhammer and Tree Pipet. A further 27 appear on the Regional International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. Additionally, six of the spotted species are considered endangered (including Herring Gull and Northern Wheatear) and 11 vulnerable by the IUCN.

Sightings of these threatened species around Cruachan come despite particularly unfavourable weather in 2021. One of the driest Aprils on record followed by an exceptionally wet May disrupted the bird breeding season. This in turn resulted in a difficult nesting season, exacerbated by food shortages due to the weather’s effect on insect life.

In the report’s survey of invertebrates, 150 different species were recorded in 2021, down from 170 in 2018. However, it’s promising that among Cruachan’s creepy-crawlies are many that are in decline elsewhere in the UK, with the numbers of some important insect types are increasing. Dragonfly and damselfly species, for example, increased from five in the previous survey to nine in 2021.

Moths and butterflies are particularly important to monitor, as Davies explains: “they’re a very strong indicator species for the health and quality of an ecosystem. They’re also very sensitive to climatic changes and  react quickly to temperature change.”

Source: Blue Leaf Nature

In 2021, 78 moth species were recorded around Cruachan, including one of Butterfly Conservation’s noted priority species (Yellow-ringed carpet), as well as six species that feature on IUCN’s red or amber lists. There were 11 butterfly species recorded in 2021, including four priority species, as well as two newly spotted species: the Small Copper and the Chequered Skipper.

That species in decline around the country are increasingly thriving at Cruachan is further testament to the power station’s lack of disruption to the environment. And as the UK’s electricity system continues to evolve, and Cruachan power station with it, closely observing the surrounding environment and its inhabitants will become even more important.

Expanding Cruachan while preserving nature

While Cruachan first started generating and storing power in the 1960s, its capabilities are becoming ever more critical as the national grid decarbonises and power generation becomes increasingly decentralised. This is why Drax is undertaking an ambitious project to expand Cruachan.

Cruachan 2 would add a further 600 MW of generation capacity to the plant for a total of 1.04 GW of power. By providing stability services to the grid, the expansion could enable an additional 300-gigawatt hours of renewable power to come online.

Source: Blue Leaf Nature

The project is epic in scale. New underground tunnels and subterranean caverns will house the reversible pump-turbines and will be carved out of the mountain, vastly increasing the size of the power station. But as with any activity in such a landscape, careful planning is essential. Detailed surveys and assessments of the area are a key requirement for planning approval.

“We need to acknowledge what’s here and show that we understand what surveys have found,” says Davies. “Then we have to present our proposals for how we will protect them and mitigate any potential disturbance.”

An advantage of pumped storage hydro is that much of the intensive excavating and construction work will take place underground, with little disturbance on the surface. Cruachan 2 has the added benefit of utilising Cruachan’s existing infrastructure. For example, it would not require flooding a valley to create a new upper reservoir.

Ultimately, Cruachan’s half century-plus of operation has not damaged or degraded the biodiversity of the Western Highlands landscape. And Davies is keen to ensure that legacy is preserved: “As a company, it’s not just something we have to do; we have a moral responsibility to be a responsible operator and look after what’s around us.”

View the Cruachan Power Station Biodiversity Survey 2021 here and find out more about Green Tourism at Cruachan here. 

Storage solutions: 3 ways energy storage can get the grid to net zero

28 February 2022

Electrification

Key points:

  • Energy storage plays a crucial role in the UK electricity system by not only providing reserve power for when demand is high but also absorbing excess power when demand is low.
  • The UK’s electricity system’s growing dependency on intermittent renewables means the amount of energy storage needed will increase to as much as 30 GW by 2050.
  • There are three different durations of energy storage needed to help balance the grid: short-term, day-to-day and long term.
  • It will take a range of technologies including batteries, pumped storage hydro and new approaches to meet the storage demands of a net zero grid.

When you turn on a lightbulb – in 10, 20, or 30 years – the same thing will happen. Electricity will light up the room. But where that electricity comes from will be different. As the country moves toward net zero emissions, low carbon and renewable power sources will become the norm. However, it’s not as simple as swapping in renewables for the fossil fuels the grid was built around.

Weather dependant sources, like wind and solar, are intermittent – meaning other sources are needed at times when there’s little wind or no sunshine to meet the country’s electricity demand. Equally as challenging to manage, however, is what to do when there’s an excess of power being generated at times of low demand.

Energy storage offers a low carbon means of delivering power at times of low supply, as well as absorbing any excess of generated power when demand is low, helping to balance and stabilise the grid. As the electricity system transforms through a range of low-carbon and renewable technologies, the amount of energy storage on the UK grid will need to expand from 3 GW of today to over 30 GW in the coming decades.

The storage solution

Even as the UK’s electricity system transforms, from fossil fuels to renewables, the way the grid operates remains primarily the same. Central to that is the principle that the supply of electricity being generated must always match the demand on a second-by-second basis.

Too little or too much power on the system can cause power outages and damage equipment. National Grid needs to be able to call on reserve power sources to meet demand when supply is low or pay to curtail renewable sources’ output when demand drops. During the summer of 2020, for example, lower demand due to Covid-19 coupled with high renewable output resulted in balancing costs 40% above expectations.

“There is a lot of offshore wind coming online in Scotland, as much as 11 GW by 2030 and a further 25 GW planned,” explains Steve Marshall, a Development Manager at Drax.

Offshore wind farm along the coast of Scotland

“It’s great because it increases the amount of renewable power on the system, but the transmission lines between Scotland and England can become saturated as much as 30-40% of the time because there is too much power.”

Electricity storage can provide a source of reserve power, as well as absorb excess electricity. These capabilities are crucial for balancing the grid and ensuring that frequency remains within a stable operating range of 50 Hertz, as well as providing other ancillary services.

Whether it’s absorbing power or delivering electricity needed to keep the grid stable, in energy storage, timing is everything.

There are three main time periods electricity storage needs to operate over:

  1. Fast-acting, short term electricity

Because electricity supply must always match demand, sudden changes mean the grid needs to respond immediately to ensure frequency and voltage remain stable, and electricity safe to use.

Batteries are considered the fastest technology for responding to a sudden spike in demand or an abrupt loss of supply.

Battery technology has evolved rapidly in recent decades as innovations like lithium-ion batteries, such as those used in electric cars, and emerging solid-state batteries become more affordable and more commonplace. This makes it more feasible to deploy large-scale installations that can absorb and store excess power from the grid.

“Batteries are good for near-instantaneous responses. It can be a matter of milliseconds for a battery to deploy power,” says Marshall. “If there’s a sudden problem with frequency or voltage, batteries can respond – it’s something that’s quite unique to them.”

The speed at which batteries can deploy and absorb electricity makes them useful grid assets. However, even very large battery setups can only discharge power for around two hours. If, for example, the wind dropped off for a long period the grid needs a longer-duration supply of stored power.

  1. Powering day-to-day changes in supply, demand, and the grid

When it comes to managing the daily variations of supply and demand the grid needs to be able to call on reserves of power for when there are unexpected changes in the weather or electricity demand from users. Pumped storage hydro power offers a low carbon way to provide huge amounts of electricity, quickly and for periods that can last as long as eight or even 24 hours.

The technology works by moving water between two reservoirs of water at different elevations. When there is demand for electricity water is released from the upper reservoir, which rushes down a series of pipes, spinning water turbines, generating electricity. However, when there is an excess of power on the electricity system the same turbines can reverse and absorb electricity to pump water from the lower to the upper reservoir, storing it there as a massive ‘water battery’.

Pumped storage hydro is a long-established technology, having been developed since the 1890s in Italy and Switzerland. In the UK today there are four pumped storage hydro power stations in Scotland and Wales, with a total capacity of 2.8 GW.

Among those is the Drax-owned Cruachan Power Station in the Scottish Highlands. The plant is made up of four generating/pumping turbines located inside Ben Cruachan between Loch Awe and an upper reservoir holding 10 million cubic metres of water.

Turbine Hall at Cruachan Power Station

Pumped hydro storage facilities can rapidly begin generating large volumes of power in as little as 30 seconds or less. The ability to switch their turbines between different modes – pump, generate, and spin mode to provide inertia to the gird without producing power – make pumped storage hydro plants versatile assets for the gird.

“How Cruachan operates depends on weather,” says Marshall. “We make as many 1000 mode changes a month, that’s how frequently Cruachan is called on by National Grid.”

As the electricity system transforms there will be a greater need for flexible energy storage like pumped storage hydro, this is why Drax is kickstarting plans to expand Cruachan Power Station, however, the specific conditions needed for such facilities can make new projects difficult and expensive.

Cruachan 2, to the east of the original power station, will add up to 600 MW in generating capacity, more than doubling the site’s total capacity to more than 1GW. By increasing the number of turbines operating at the facility it increases the range of services that the grid can call upon from the site.

  1. Long-term electricity solutions

However, storage technologies as they exist today cannot alone offer all the solutions the UK will need to achieve its net zero targets. While technologies like pumped storage can generate for the better part of a day, longer periods of unfavourable conditions for renewables will need new approaches.

In March 2021, for example, the UK experienced its longest cold and calm spell in more than a decade, with wind farms operating at just 11% of their capacity for 11 days straight, according to Electric Insights.

The shortfall in the country’s primary source of renewable power was made up for by gas power stations. But in a net zero future, such responses will only be feasible if they’re part of carbon capture and storage systems or replaced by other carbon neutral or energy storage solutions.

Generating enough power to supply an electrified future, as well as being able to take pressure off the grid and provide balancing services will require a range of technologies working in tandem over extended periods.

Interconnectors with neighbouring countries, for example, can work alongside storage solutions to shed excess power to where there is greater demand. Similarly, rather than curtailing wind or solar power, extra electricity could be used for electrolysis to produce hydrogen. Other functions may include demand side response where heavy power users are incentivised to reduce their electricity usage during peak periods helping to reduce demand.

To achieve stable, reliable, net zero electricity systems the UK needs to act now to not only replace fossil fuels with renewables but put the essential energy storage and balancing solutions in place, that means electricity is there when you turn on a lightbulb.

Expanding Cruachan: An epic energy storage project to help unlock a renewable future

12 January 2022

Power generation
Loch Awe from Cruachan

At the beginning of March 2021, Britain experienced its longest ‘wind drought’ in a decade. For eleven days, wind output averaged just 11% of the UK electricity mix – less than a quarter of the average output in the month before and the month after. The power system was able to cope as gas power stations made up most of the shortfall.

But keeping the lights on will become increasingly challenging as electricity generation shifts from carbon-intensive coal and gas towards weather-dependent wind and solar technologies, where supply is variable and intermittent. One solution to maintain a stable, resilient power supply as the electricity system decarbonises is increasing the amount of long-duration energy storage that can plug gaps and balance the gird.

Pumped hydro storage – a tried and tested solution

The largest-capacity form of electricity storage by far, pumped storage hydro plays a key role in the energy mix and stabilising the grid. Which is why, following a feasibility study, Drax has kickstarted plans to extend our pumped hydro storage power station at Cruachan in the Scottish Highlands.

By drilling a second cavern inside Ben Cruachan, Cruachan 2, to the east of the original power station, will add up to 600 MW in generating capacity, more than doubling the site’s total capacity to more than 1GW. It’s an epic project and one that could provide power for around a million homes.

The original Cruachan facility has been supplying and absorbing excess power to the grid since 1965. Acting as a ‘green battery’, it stores low-carbon energy when there is over supply and releases it when demand is high.

Designed at a time when the grid was powered by nuclear or coal-fired plants that could only adjust output slowly, Cruachan’s technology is still cutting edge and has proved equally successful at balancing more volatile supply and demand as power generation has shifted towards renewables and low-carbon sources.

“Cruachan plays a critical role in the UK energy system today because it provides a unique range of services for a single asset – it can both generate electricity at 440 MW but it can also pump which means it takes that power off the system so in effect you can deploy greater renewable resources. And if there’s too much wind in the system, rather than curtail wind farms you can pump to take 482 MW off the system,” says Steve Marshall, Development Manager at Cruachan 2.

Cruachan Power Station

Pumped Storage Hydro (PSH) at Cruachan Power Station [click to view/download]

Enabling more renewables on the system

As Marshall points out, too much wind can be as problematic as too little. With the government’s ambition to quadruple offshore wind capacity by 2030 to 40 gigawatts (GW), the grid will have to manage significantly more wind-generated power, and consequently much greater fluctuations in supply.

Currently, the demand left to be met by renewable generation ranges from 10 GW to 30 GW throughout the year. But modelling by Imperial College London suggests that with 40 GW of offshore wind this range could expand, from 30 GW right down to minus 30 GW, in other words, renewables would produce significantly more than national demand. Without long-term storage capacity, this energy will be wasted, forcing the grid to pay wind farms to stop generating.

“There’s a lot of offshore wind coming online in Scotland that has to be transported through the transmission system to England where the demand is,” says Marshall. “The transmission system in 2030 could become saturated more than 20-30% of the time because there’s too much renewable power. You have a choice: either build more transmission lines or more energy storage that can take that power off the system.”

Turbine Hall at Cruachan Power Station

Plugging the inertia gap

As well integrating more renewables into the electricity mix, the Cruachan expansion may also help meet the inertia shortfall. Inertia – stored kinetic energy – acts as a ‘shock absorber’ in the system, smoothing out sudden changes in power supply and demand and ensuring that frequency remains stable at 50 Hz. This is a critical, as just 1% variation above or below this standard can damage equipment and infrastructure.

Many renewable technologies, such as wind turbines and solar PV panels, aren’t built around spinning turbines that synchronise with the grid and so lack inherent inertia. Cruachan’s turbines, on the other hand, spin at 500/600rpm and produce electricity at the grid frequency of 50 Hz providing inertia that helps the grid remain stable. Indeed in 2020, National Grid ESO contracted a unit at Cruachan to provide inertia 24/7 as part of a 6 year contract

“The grid calls on Cruachan three to four hundred times a month, with generation mode changes ranging from hours to very short bursts,” explains Marshall. Increasing the number of turbines would allow Cruachan to respond to a greater range of the grid’s needs.

“With more units you have more flexibility,” says Marshall. “If you start to change the generating unit sizes to 150 MW or 200MW machines you get different levels of inertia that offers more options to the grid.”

Building on Cruachan’s legacy

While automated drilling processes mean that the rock will no longer need to be excavated by ‘Tunnel Tigers’, the crews that hand-drilled, blasted, and excavated granite from the mountainside, Cruachan 2 will still create an estimated 300 jobs during peak construction and support around 900 jobs across the country. And by bringing around 300 GW a year of renewable energy to the grid, and reducing requirement for further transmission lines the expansion has the potential to save consumers more than £350 million in energy costs by 2050.

“With the increased deployment of renewables there is a need for more assets like Cruachan,” says Marshall. The ambition is to have Cruachan 2 operational by 2030 and work could start as early as 2024.

But progress is dependent on the government providing support through a revenue stabilisation mechanism for such a long-term, large-scale energy storage project. A study by KPMG found that a Cap and Floor regime, similar to what has unlocked a wave of investment in cross-border inter-connectors, could be the best mechanism for long-duration storage. If this is forthcoming, the expansion could play a vital role in stabilising the grid and smoothing the UK’s transition to a net zero power system.

Pumped storage hydro: why it’s key to a renewable future

Will Gardiner, Chief Executive Officer, Drax Group

3 July 2021

Opinion

In brief 

  • Pumped storage hydro (PSH) can provide the large-scale power storage that a grid increasingly dominated by wind and solar needs. 
  • This expansion project – called Cruachan 2 – would help enable greater deployment of renewables to the grid (approximately 300 GWh a year), deliver cumulative savings of more than £350 million for consumers, and support 900 green jobs.
  • Our community consultation for Cruachan 2 is open until 23 July. Please share your view.
  • Cruachan 2 could be operational by 2030, but for it to materialise we need the UK Government to commit to creating a route to market for this technology as well as continued support from the Scottish Government.

Great Britain has made incredible advances in wind and solar over the last decade. In fact, the Prime Minister has laid out ambitious plans to power every UK home by offshore wind by 2030. This is a bold and necessary step, but we must be cognisant of the nature of the power that wind and solar bring to the grid.

Unlike the fossil fuels on which the grid was built, intermittent power sources – such as wind or solar – only generate electricity when the wind is blowing or the sun is shining and turning them off  when they are generating too much power is wasteful. A grid overly reliant on these sources can fall victim to unfavourable weather conditions, leading to too little power generation and the risk of blackouts.

Before sunrise solar power plants

Grid scale flexibility and long duration energy storage technologies can address this, as they are able to preserve excess power when generation is peaking, and then release it back on to the grid when demand rises. The problem is, how do you create storage large enough to operate at grid scale? And how do you deploy that at a speed quick enough to meet sudden changes in demand?

We believe pumped storage hydro (PSH) is an essential component of a decarbonised, reliable electricity grid. The country is at a point where it needs more PSH to take the next step forward in its journey to a net zero economy – at Drax we are poised to help deliver it.

We now need the support and stability of technologies like pumped storage hydro to ensure our grid is not only greener, but stable, affordable and flexible.

Looking at Scotland specifically, its emissions reduction targets, its 2045 commitment for net zero and the challenges facing the Scottish Government today are very different to those it faced just a decade ago.

We entered a new era for climate action in Scotland at the beginning of the 2020s. The challenge for the next decade is to accelerate the decarbonisation of other sectors of the economy, much of it via electrification and to increase flexibility in the power system to help meet the challenge of operating large amounts of intermittent renewable power.

The power of pumped storage hydro

PSH works like this: in times of surplus electricity supply (for example, when weather allows for high volumes of wind and solar) it uses excess grid electricity to pump water up into high altitude reservoirs. Then, in times of high demand but low generation, that water is released back downhill, powering turbines that generate electricity as it goes.

Cruachan Power Station

Pumped Storage Hydro (PSH) at Cruachan Power Station

At Ben Cruachan in Argyll, Scotland, Drax already operates one of the largest PSH facilities in the UK. Built in the mid 1960s, Cruachan Power Station has a capacity of 440 megawatts (MW) and is able to power a city for 16 hours.

How do you create energy storage large enough to operate at grid scale? And how do you deploy it at a speed quick enough to meet sudden changes in demand?

For more than 55 years it has been an integral part of supporting the country’s grid, but it could do more. That’s why we’re planning an expansion, which we call Cruachan 2 – a project that would add another 600 MW of pumping and generation capacity to the plant for a total of 1.04 GW of power.

Engineer within Cruachan Power Station

Engineer within Cruachan Power Station

This would not only support the UK’s renewable strategy but enable more wind and solar onto the grid and deliver cumulative savings of more than £350 million to consumers as the network continues to decarbonise.

And on top of storage provision, the construction and operation of Cruachan 2 would directly create 300 jobs over the five-to-six-year construction period and support a total of nearly 900 jobs across the region – not to mention provide a range of ancillary grid services such as inertia that help will keep the network stable.

We’re progressing plans to have Cruachan 2 operational by 2030, but success will rely on the right policies and commitments from Government to instil investor confidence by reducing risk.

The policy needed to support pumped storage hydro

As highlighted in a recent report by the Renewable Energy Association, energy market mechanisms that were introduced to support low carbon and renewable generation (such as Contracts for Difference and the Capacity Market) are not able to support projects like Cruachan 2, which come with significant up-front costs and long build times.

However, if the Government were to investigate the possibility of introducing alternative mechanisms to support long-duration, large-scale energy storage technologies (similar to those used to enable interconnectors), it could pave the way for PSH to play a powerful supporting role in creating a greener, cleaner UK, where climate and economic sustainability go hand in hand.

Renewables are essential to the UK reaching net zero, and the work that has been done to increase their capacity on the country’s grid is testament to the Government’s ambition. But we now need the support and stability of technologies like PSH to ensure our grid is not only greener, but stable, affordable and flexible.

Go deeper

Find out more about Cruachan 2 and take part in our community consultation.

What is pumped storage hydro?

22 June 2021

Power generation

What is pumped storage hydro?

Pumped storage hydro (PSH) is a large-scale method of storing energy that can be converted into hydroelectric power. The long-duration storage technology has been used for more than half a century to balance demand on Great Britain’s electricity grid and accounts for more than 99% of bulk energy storage capacity worldwide.

How does it work?

The principle is simple. Pumped storage facilities have two water reservoirs at different elevations on a steep slope. When there is excess power on the grid and demand for electricity is low, the power is used to pump water from the lower to the upper reservoir using reversible turbines. When demand is high, the water is released downhill into the lower reservoir, driving the turbines the other direction to generate electricity.

Pumped storage hydro plants can also provide ancillary services to help balance the power system, such as inertia from spinning turbines, which ensures the system runs at the right frequency and reduces the risk of power cuts.

Why is pumped storage hydro important for energy transition?

Governments around the world are shifting from fossil fuels to renewable energy sources to meet their climate goals. But critically important power technologies such as wind and solar pose challenges for power grid operators.

Being weather-dependent, the supply from these renewables is intermittent. For example, wind farms accounted for almost a quarter of the UK’s total electricity generation in 2020, but on some days, less than 10% of the country’s electricity needs were met by wind. Changing weather patterns and extreme weather events with prolonged periods of little wind or reduced daylight are a further the threat to grid stability.

When output from renewables falls, grid operators mostly turn to gas-fired power stations to plug the gap. But relying on fossil fuels such as natural gas in the long term to balance the grid will compromise efforts to reach net zero emissions by 2050.

Pumped storage hydro facilities act as vast ‘water batteries’. They are a flexible way of storing excess energy generated by renewables, cost-effectively and at scale.

How can pumped storage hydro capacity be increased?

As old thermal power plants are decommissioned and renewables provide an increasing share of the electricity supply, storage capacity will need to grow if climate goals are to be met. Over the next two to three decades, Great Britain’s energy storage capacity alone will need to increase tenfold, from 3 gigawatts (GW) to around 30 GW.

Pumped storage hydro power stations require very specific sites, with substantial bodies of water between different elevations. There are hundreds, if not thousands, of potential sites around the UK, including disused mines, quarries and underground caverns, but the cost of developing entirely new facilities is huge. A more cost-effective way to increase storage capacity is by expanding existing plants, such as the Cruachan Power Station in Scotland.

Pumped Storage Hydro fast facts

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Capacity Market Agreements

11 March 2021

Investors
Cruachan pylons

Drax Group plc
(“Drax” or the “Group”; Symbol:DRX)
RNS Number : 8747R

T-4 auction – provisional results for existing pumped storage and hydro assets

Drax confirms that it has provisionally secured agreements to provide a total of 617MW of capacity (de-rated 582MW) principally from its pumped storage and hydro assets(1). The agreements are for the delivery period October 2024 to September 2025, at a price of £18/kW(2) and are worth around £10 million in that period. These are in addition to existing agreements which extend to September 2024.

T-4 auction – provisional results for new build system support assets

Drax confirms that it has provisionally secured 15-year agreements for three new 299MW (de-rated 284MW) Open Cycle Gas Turbine (OCGT) projects at sites in England and Wales(3). The agreements are for the delivery period October 2024 to September 2039, at a price of £18/kW(2) and are worth around £230 million in that period.

Artist’s impression of a Drax rapid-response gas power station (OCGT)

Artist’s impression of a rapid-response gas power station (OCGT)

These assets are intended to operate for short periods of time to meet specific system support needs. As the UK transitions towards a net zero economy, it will become increasingly dependent on wind generation and as such, fast response system support technologies such as these OCGTs are increasingly important to the energy system as a means to enable more wind to run more often and more securely.

The total capital cost of these projects is approximately £80-90 million each, with a build time of around two years.

A further OCGT project participated in the auction but exited above the clearing price and did not accept an agreement.

Drax will now evaluate options for all four OCGT projects including their potential sale.

Continued focus on biomass strategy and the development of negative emissions

In December 2019 Drax announced an ambition to become a carbon negative company by 2030 using Bioenergy Carbon Capture and Storage (BECCS) and the Group remains focused on its biomass strategy. In January 2021 Drax completed the sale of its Combined Cycle Gas Generation (CCGT) assets and in March 2021 ends commercial coal generation. Drax believes that its remaining portfolio of sustainable biomass, pumped storage and hydro will be amongst the lowest carbon generation portfolios in Europe.

Enquiries

Drax Investor Relations: Mark Strafford

+44 (0) 7730 763 949

Media

Drax External Communications: Ali Lewis

+44 (0) 7712 670 888

Website: www.drax.com/uk