Tag: energy storage

Winter on the Hollow Mountain

15 January 2020

Power generation
Winter snow scene around the Hydro electric Dam on Ben Cruachan,above Loch Awe, Argyll, Scotland

Scotland’s landscape is defined by its weather. The millennia of wind, rain and snow has battered the country, ebbing away at its rivers, mountains, valleys and deep lochs forged by ice ages and volcanos. Weather also plays an important role in the country’s power generation. The country has more than 9 gigawatts (GW) of installed wind power – enough to sometimes meet double Scotland’s electricity demand – as well as having a long history of hydropower.

But while it is an intrinsic part of the country, Scotland’s weather can be anything but pleasant. Rain can be persistent and when the temperature drops in winter, it turns to snow – a lot of it. Scotland gets more snow than any other part of the UK.

Scottish poet Robert Burns described the harshness of the winter months in his 1781 poem Winter A Dirge:

“The wintry west extends his blast,

And hail and rain does blaw;

Or the stormy north sends driving forth

The blinding sleet and snaw:”

Sleet and ‘snaw’ (snow) fall occurs on average for 38 days a year in Scotland, compared to an average of 23 days across the rest of the United Kingdom, and can remain covering mountaintops long into spring.

Ben Cruachan Mountain

Ben Cruachan

The peak of Ben Cruachan in the Western Highlands is no exception. Cruachan Power Station, on the slopes of the mountain, however, must be ready to either generate or absorb electricity through all forms of weather – even the most severe.

“On a few occasions the snowfall has been so extreme that we’ve been unable to access the dam for a few weeks at a time,” says Gordon Pirie, a Civil Engineer at Cruachan. “Thankfully, we have enough controls in place where we are still able to monitor and operate things remotely.”

Mountain road from Cruachan Power Station to its dam blocked due to snow

Mountain road from Cruachan Power Station to its dam blocked due to snow

This mountainside location and winter weather can make for tough working conditions, but Cruachan is designed to handle it. In fact, in some cases it benefits from it.

Taking advantage of wet weather

Cruachan is built around the geography and climate of the Highlands. It stores water in an upper reservoir 400 meters (1,312 feet) up Ben Cruachan and uses its elevation to run it down the mountain, spin a turbine and generate power.

And when there is excess electricity being generated nationally, the same turbines reverse and use the excess electricity to pump water from Loch Awe up to the reservoir, helping to balance the grid. This acts as a form of energy storage by essentially stockpiling the excess electricity in the form of water held in the top reservoir.

For the most part the water used to generate electricity comes exclusively from Loch Awe and is passed up and down the mountain. However, 10% of it comes for ‘free’, as it’s collected from natural rainfall and surface water that makes its way to the upper reservoir through Cruachan’s aqueducts. This system of 14 kilometres of interconnected concrete pipes covers a 23 square kilometre radius around the reservoir and is designed to bring in water from 75 intakes dotted around the top of the mountain.

A North of Scotland Hydro-Electric Board diagram from c.1960s showing the aqueducts feeding Cruachan’s dam; click to view/download.

A North of Scotland Hydro-Electric Board diagram from c.1960s showing the aqueducts feeding Cruachan’s dam; click to view/download.

Some of these intakes are as small as street drains, while others are large enough to drive a Land Rover into. It’s part of Pirie’s job to keep them in good working order so they continue to deliver water to the reservoir. As the intakes are scattered around the mountaintop, they must be able to deal with whatever the Scottish winter throws at them.

Gordon Pirie, Civil Engineer and Cruachan Power Station dam

Gordon Pirie, Civil Engineer and Cruachan Power Station dam

“Even in freezing conditions the water will still flow through the aqueduct system, the intakes have a built-in feature which allows the water to flow into them even if the surface is frozen solid,” explains Pirie. “Any snow or frost on the ground eventually thaws and makes its way to the reservoir.”

As spring arrives and snow begins to thaw across the Highlands, greater volumes of water will run off into the reservoir and the power station’s engineers work to manage the water level.

Keeping water pressure under control

Cruachan Dam

Thawing snow can bring greater volumes of water into the reservoir.

The power station must be able to pump water and absorb excess electricity from the grid at a moment’s notice. This ability to turn excess electricity into stored energy makes Cruachan hugely useful in controlling the grid’s voltage, frequency and in keeping it stable. However, there must be enough space available in the reservoir for the water being pumped up the mountainside to enter – even when excessive rainfall or melting snow begins to naturally fill it up.

The power station can control the reservoir levels through a number of means. This includes the ability to close off an aqueduct, or to run the turbines without generating electricity so the team can move water from the reservoir into Loch Awe below.

If the water level and pressure on the dam reaches dangerous levels a ‘dispenser valve’ can be opened in an emergency, sending a jet of water flying out the dam to cascade safely down the mountainside. However, outside of testing, this has never been necessary to do. 

And while the weather might be the most persistent natural force the power station must deal with, it’s not the only one. “Recently we had an issue with a bat roosting within one of the tunnels in which we were carrying out stabilisation works,” recalls Pirie. “It was looking for a suitable location to hibernate for the winter and the tunnel provided the ideal environment. We had to stop works to have a bat survey undertaken and apply for a bat license.”

Cruachan’s location makes for stunning views of the Highlands, but occasionally brutally cold and perilously wet conditions come with the territory. For the power station team, working with the sometimes-despairing weather is all part of what allows the Hollow Mountain to operate as it has done for more than half a century.

The Highlands around Ben Cruachan are rich with wildlife. Educational information on area’s flora and fauna can be explored at the Cruachan Power Station visitor centre.

The Highlands around Ben Cruachan are rich with wildlife. Educational information on area’s flora and fauna can be explored at the Cruachan Power Station visitor centre.

Visit Cruachan — The Hollow Mountain to take the power station tour.

The men who built a power station inside a mountain

12 November 2019

Power generation
Cruachan tunnel tigers

Travelling through the Highlands towards the West Coast of Scotland, you pass the mighty Ben Cruachan – its 1,126 metre peak towers over the winding Loch Awe beneath. It is the natural world on a huge scale, but within its granite core sits a manmade engineering wonder: Cruachan Power Station.

Opened by The Queen in 1965, it is one of only four pumped-hydro stations in the UK and today remains just as impressive an engineering feat as when it was first opened.

Cruachan is operated safely and hasn’t had a lost time injury in 15 years. The robust health and safety policies and practices employed at the power station were not in place all those decades ago.

It took six years to construct, enlisting a 4,000-strong workforce who drilled, blasted and cleared the rocks from the inside of the mountain, eventually removing some 220,000 cubic metres of rubble. The work was physically exhausting – the environment dark and dangerous.

Nicknamed the ‘Tunnel Tigers’, the men that carried the work out came from far and wide, attracted to its ambition as well as a generous pay packet reflective of the danger and difficulty of the work. But few of them were fully prepared for the extent of the challenge.

One labourer, who started at Cruachan just after his 18th birthday, recalls: “I was in for a shock when I went down there. The heat, the smoke – you couldn’t see your hands in front of you.”

Inside the mountain

The work of hollowing out Ben Cruachan was realised by hand-drilling two-to-three metre deep holes into the granite rockface. An explosive known as gelignite, which can be moulded by hand, was packed into the drilled holes and detonated. The blasted rocks were removed by bulldozers, trucks and shovels, before drilling began on the fresh section of exposed granite. In total, 20km of tunnels and chambers were excavated this way, including the kilometre-long entrance tunnel and the 91-metre-long, 36-metre-high machine hall.

Wilson Scott was just 18 when he got a job working as a labourer at Cruachan while the machine hall was being cleared out.

“The gelignite, it had a smell. Right away I was told not to put it near your face,” he says, “It’ll give you a splitting headache and your eyes will close with the fumes that come off it. It was scary stuff.”

This process allowed for rapid expansion through the mountain. With three or four blasts each 12-hour shift, some 20 metres of rock could be cleared in the course of a day. Activity was constant, and to save the men having to make the journey back up to the surface, refreshments came to them.

“There was a bus that went down the tunnel at 11 o’clock with a huge urn of terrible tea,” says Scott. “Most of the windows were out of the bus because the pressure of the blasting had blown them in.”

The tea did little to make the environment hospitable, however. From the water dripping through the porous rocks making floors slippery and exposed electrics vulnerable, to the massive machinery rushing through the dense dust and smoke, danger was ever-present. Loose rocks as large as cars would often fall from exposed walls and ceilings while the regular blasting gave the impression the entire mountain was shaking.

“I’ll tell you something: going into that tunnel the first time,” Scott says. “It was a fascinating place, but quite a scary place too.

Above them, on top of the mountain, a similarly intrepid team tackled a different challenge: building the 316-metre-long dam. They may have escaped the hot and humid conditions at the centre of Cruachan, but their task was no less daunting.

Cruachan dam construction, early 1960s

Cruachan dam construction, early 1960s

On top of the dam

Out in the open, 400 metres above Loch Awe, the team were exposed to the harsh Scottish elements. John William Ross came to Cruachan at the age of 35 to work as a driver and spent time working in the open air of the dam. “You’d get oil skins and welly boots, and that was it. We didn’t have gloves, if your hands froze – well that’s tough luck isn’t it.” Mr Ross sadly passed away recently.

Charlie Campbell, a 19-year-old shutter joiner who worked on the dam found an innovative way around the cold. “You’d put on your socks, and then you’d get women’s tights and you’d put them over the top of the socks, and then you’d put your wellies on and that’d keep your feet a wee bit warmer. We thought it did anyway. Maybe it was just the thought of the women’s stockings.”

Pouring the concrete of the dam – almost 50 metres high at its tallest point – was precarious work, especially given the challenges of working with materials like concrete and bentonite (a slurry-like liquid used in construction).

“It was horrible stuff. It was like diarrhoea, that’s the only way of explaining it,” says Campbell. “There was a boy – Toastie – I can’t remember his real name. He fell into it. They had quite a job getting him out, they thought he was drowned, but he was alright.”

Many others were not alright. The danger of the work and conditions both inside and on top of the mountain meant there was a significant human cost for the project. During construction, 15 people tragically lost their lives.

Today a carved wooden mural hangs on the wall of the machine hall to capture and commemorate the myth of the mountain and the men who sadly died – a constant reminder of the bravery and sacrifice they made.

The men that made the mountain

The Cruachan ‘Tunnel Tigers’

The Tunnel Tigers were united in their efforts, but came from a range of backgrounds and cultures. Polish and Irish labourers worked alongside Scots, as well as displaced Europeans, prisoners of the second world war and even workers from as far as Asia. The men would work 12, sometimes 18-hour shifts, seven days a week. Campbell adds that some men opted to continue earning rather than rest by doing a ‘ghoster’, which saw them working a solid 36 hours.

Many men would make treble the salary of their previous jobs, with some receiving as much as £100 a week, at a time when the average pay in Scotland was £12. Some teams’ payslips were stamped with the words ‘danger money’ – illustrative of the men’s motivation to endure such life-threatening work.

While it was a dangerous and demanding job, many of the Tigers look back with fond memories of their time on the site and many stayed in the area for years after. “It was an experience I’m glad I had,” says Scott. “It puts you in good stead for the rest of your days.”

As for Cruachan Power Station, its four turbines are still relied on today by Great Britain to balance everyday energy supply. As the electricity system continues to change, the pumped hydro station’s dual ability to deliver 440 megawatts (MW) of electricity in just 30 seconds, or absorb excess power from the grid by pumping water from Loch Awe to its upper reservoir, is even more important than when it opened.

Standing at the foot of a mountain more than 50 years ago, the men about to build a power station inside a lump of granite may have found it unlikely their work would endure into the next millennium. They may have found it unlikely it was possible to build it at all. But they did and today it remains an engineering marvel, a testament to the effort and expertise of all those who made it.

Visit Cruachan – The Hollow Mountain

How will 5G revolutionise the world of energy and communications?

30 August 2019

Electrification
Smart cellular network antenna base station on the telecommunication mast on the roof of a building.

What should be made of the 5G gap? It’s the difference between what some commentators are expecting to happen thanks to this new technology and what others perhaps more realistically believe is possible in the near future.

What we call 5G is the fifth generation of mobile communications, (following 4G, 3G, etc.). It promises vastly increased data download and upload speeds, much improved coverage, along with better connectivity. This will bring with it lower latency – potentially as low as one millisecond, a 90 per cent reduction on the equivalent time for 4G – and great news for traders and gamers, along with lower unit costs.

Trading desk at Haven Power, Ipswich

The latest estimates predict that 5G will have an economic impact of $12 trillion by 2035 as mobile technology changes away from connecting people to other people and information, and towards connecting us to everything.

Some experts believe the effects of 5G will be enormous and almost instantaneous, transforming the way we live. It will have a huge effect on the internet of things, for instance, making it possible for us to live in a more instant, much more connected world with more interactions with ‘smart objects’ every day. Driverless cars that ‘talk’ to the road and virtual and augmented reality to help us as we go could become part of our everyday lives.

Others see 5G as a revolution that will begin almost immediately, but which could take many years to materialise. The principal reason for this is the sheer level of investment required.

The frequencies being used to carry the signal from the proposed 5G devices can provide an enormous amount of bandwidth, and carry unimaginable amounts of data at incredible speeds. But they cannot carry it very far. And the volume of devices connected to this network will be enormous. The BBC estimates that between 50 and 100 billion devices will be connected to the internet by 2020 – more than 12 for every single person on Earth.

So in order to support the huge increase in connectivity that is anticipated a reality, there will be a need for a comparably large increase in the number of base stations – with as many as 500,000 more estimated to be needed in the UK alone. That’s around three times as many base stations as required for 4G.

To carry the amount of data anticipated without catastrophic losses in signal quality will require the stations to be no more than 500m apart. While that may be technically possible in cities, it will only happen as a result of huge amounts of investment. And what will happen in the countryside, with its lower population density? It seems doubtful in the extreme that any corporation will regard it as a potentially profitable business decision to build a network of base stations half a kilometre apart in areas where few of their customers live. And that’s without taking into account the town and country planning system or the views of residents, who may not welcome new base stations near their homes.

Until this year, the only two workable examples of functional 5G networks are one built by Samsung in Seoul, South Korea, and another by Huawei in Moscow in advance of the 2020 Football World Cup. Although the first UK mobile networks have now begun to offer the new communications standard, 5G is still clearly a long way from being able to deliver on its potential.

What will 5G mean for the world of energy?

A report from Accenture contains a number of predictions about how 5G may change the energy world by helping to increase energy efficiency overall and accelerating the development of the Smart Grid.

  1. 5G uses less power than previous generations of wireless technology

This means that less energy will be used for each individual connection, which will take less time to complete than with 4G devices, thereby saving energy and ultimately money too. It is important to remember that even though such savings will be significant, they will need to be offset against the huge global increase in communications through 5G-connected devices.

  1. Accelerating the Smart Grid to improve forecasting

5G has the potential to help us manage energy generation and transmission more efficiently, and therefore more cost-effectively.

The report’s authors anticipate that “By allowing many unconnected energy-consuming devices to be integrated into the grid through low-cost 5G connections, 5G enables these devices to be more accurately monitored to support better forecasting of energy needs.

  1. Improve demand side management and reduce costs

 “By connecting these energy-consuming devices using a smart grid, demand-side management will be further enhanced to support load balancing, helping reduce electricity peaks and ultimately energy costs.”

  1. Manage energy infrastructure more efficiently and reduce downtime

By sharing data about energy use through 5G connections, the new technology can help ensure that spending on energy infrastructure is managed more efficiently, based on data, in order to reduce the amount of downtime.

And in the event of any failure, smart grid technology connected by 5G will be able to provide an instant diagnosis – right to the level of which pylon or transmitter is the cause of an outage – making it easier to remedy the situation and get the grid up and running again.

5G could even help turn street lighting off at times when there are no pedestrians or vehicles in the area, again reducing energy use, carbon emissions, and costs. Accenture estimate that in the US alone, this technology has the potential to save as much as $1 billion every year.

More data, more power

Although 5G devices themselves may demand less power than the telecoms technology it they will eventually replace, that doesn’t tell the whole story.

More connected devices with more data flowing between them relies on more data centres. This has led some data centres to sign Power Purchase Agreements to both reduce the cost of their insatiable desire for electricity and also ensure its provenance.

Data centre

As well as data centres, the more numerous base stations needed for 5G will consume a lot of power. One global mobile network provider says just to operate its existing base stations leads to a £650m electricity bill annually, accounting for 65% of its overall power consumption.

Base station tower

Contrary to the findings of the Accenture report, a recent estimate has put the power requirement of an individual 5G base station at three times that of a 4G. Keeping in mind that three of these are needed for every existing base station, the analysis by Zhengmao Li of China Mobile, suggests a nine-fold increase in electricity consumption just for that key part of a 5G network.

With the Great Britain power system decarbonising at a rapid pace, the additional power required to electrify the economy with new technologies shouldn’t have a negative environmental impact – at least when it comes to energy generation.

However, as we use ever-more powerful and numerous devices, we need to ensure our power system has the flexibility to deliver electricity whatever the weather conditions. This means a smarter grid with more backup power in the form of spinning turbines and storage.

In energy storage timing is everything

21 August 2019

Power generation
Cruachan Power Station

Electricity is unlike any other resource. The amount being generated must exactly match demand for it, around the clock.

Managing this delicate balancing act is the job of the National Grid Electricity System Operator (ESO), which works constantly to ensure supply meets demand and the grid remains balanced. One of the ways it does this is by storing energy when there is too much and deploying it when there is too little.

Although there are many different ways of storing energy at a small scale, at grid level it becomes more difficult. One of the few ways it is currently possible is through pumped hydro storage. Cruachan Power Station in the Highlands of Scotland is one of four pumped storage facilities in Great Britain. It uses electrically-driven turbines to pump water up a mountain into a reservoir when there is excess electricity on the grid, and then releases the water stored in the reservoir back down, to spin the same turbines to generate power when it’s needed quickly.

The dual capabilities of these turbines are unique to pumped hydro storage and contribute to the overall grid’s stability. However, what dictates when Cruachan’s turbines switch from pump to generate and vice versa is all a matter of what the grid needs – and when.

The switch from pump to generate

While the machine hall of Cruachan Power Station is an awe-inspiring place for its size and location 396 metres beneath Ben Cruachan, it generates electricity much like any other hydropower station: harnessing the flow of water to rotate any number of its four 100+ megawatt (MW) turbines.

This mode – simply called ‘generate mode’ – is usually employed during periods of peak power demand such as mornings and evenings, during a major national televised event, or when wind and solar energy output drops below forecast. As a result, starting up and generating millions of watts of electricity has to be fast.

“It takes just two minutes for a turbine to run up from rest to generate mode,” says Martin McGhie, Operations and Maintenance Manager at the power station. “It takes slightly longer for the turbines to run down from generate to rest, but whatever function the turbines are performing, they can reach it within a matter of minutes.”

The reverse of generate mode is pump mode, which changes the direction of travel for the water, this time using electricity from the grid to pump water from the vast Loch Awe at the foot of Ben Cruachan to the upper reservoir, where it waits ready to be released.

In contrast to generate mode, pump mode typically comes into play at times when demand is low and there is too much power on the system, such as during nights or at weekends, when there is excessive wind generation. However, the grid has evolved since Cruachan first began generating in 1965 and this has changed when it and how it operates.

“In the early days, Cruachan was used in a rather predictable way: pumping overnight to absorb excess generation from coal and nuclear plants and generating during daytime peak periods,” says Martin. “The move to more renewable energy sources, like wind, mean overall power generation is more unpredictable.”

He continues: “There has also been a move from Cruachan being primarily an energy storage plant to one which can also offer a range of ancillary services to the grid system operator.”

The benefits of Spin mode

In between pumping water and generating power, Cruachan’s turbines can also spin in air while connected to the grid, neither pumping not generating. This is essentially a ‘standby mode’ where the turbines are ready to either quickly switch into generation or pumping at a moment’s notice (they spin one way for ‘spin pump’; the other for ‘spin generate’). These spin modes are requested by the ESO to ensure reserve energy is available to respond rapidly to changes on the grid system.

In spin generate mode, the generator is connected up to the grid but the water is ejected from the space around the turbine by injecting compressed air. The turbine does not generate power but is kept spinning, allowing it to quickly start up again. As soon as the grid has an urgent need for power, the air is released and the water from the upper reservoir flows into the turbine to begin generation in under 30 seconds.

Spin pump works on the same basis as spin generate, but with the turbine rotating in the opposite direction, ready to pump at short notice. This allows Cruachan to absorb excess generation and balance the system as soon as the ESO needs it.

“The use of spin mode by the ESO is highly variable and dependant on a number of factors e.g. weather conditions or the state of the grid system at the time” says Martin. This unpredictability of the increasingly intermittent electricity system makes the flexibility of Cruachan’s multiple turbines all the more important.

Ready for the future grid

It’s not only the types of electricity generation around the system that are changing how Cruachan operates. Martin suggests that the way energy traders and the ESO use Cruachan will continue to evolve as the market requirements and opportunities change.

Technology is also changing the market and Martin predicts this could affect what Cruachan does. “In the future we will face competition from alternative storage technologies, such as batteries, electric vehicles, as well as competition for the other ancillary services we offer.”

However, Cruachan’s flexibility to generate, absorb or spin in readiness means it is prepared to adjust to any future changes.

“Cruachan is always ready to modify or upgrade to meet requirements, as we have done in the past,” says Martin. “The priority is always to be able to deliver the services required by the grid system operator – in characteristic quick time.”

Visit Cruachan — The Hollow Mountain to take the power station tour.

Read our series on the lesser-known electricity markets within the areas of balancing services, system support services and ancillary services. Read more about black start, system inertia, frequency response, reactive power and reserve power. View a summary at The great balancing act: what it takes to keep the power grid stable and find out what lies ahead by reading Balancing for the renewable future.

What is a fuel cell and how will they help power the future?

27 June 2019

Carbon capture
A model fuel cell car

NASA Museum, Houston, Texas

How do you get a drink in space? That was one of the challenges for NASA in the 1960s and 70s when its Gemini and Apollo programmes were first preparing to take humans into space.

The answer, it turned out, surprisingly lay in the electricity source of the capsules’ control modules. Primitive by today’s standard, these panels were powered by what are known as fuel cells, which combined hydrogen and oxygen to generate electricity. The by-product of this reaction is heat but also water – pure enough for astronauts to drink.

Fuel cells offered NASA a much better option than the clunky batteries and inefficient solar arrays of the 1960s, and today they still remain on the forefront of energy technology, presenting the opportunity to clean up roads, power buildings and even help to reduce and carbon dioxide (CO2) emissions from power stations.

Power through reaction

At its most basic, a fuel cell is a device that uses a fuel source to generate electricity through a series of chemical reactions.

All fuel cells consist of three segments, two catalytic electrodes – a negatively charged anode on one side and a positively charged cathode on the other, and an electrolyte separating them. In a simple fuel cell, hydrogen, the most abundant element in the universe, is pumped to one electrode and oxygen to the other. Two different reactions then occur at the interfaces between the segments which generates electricity and water.

What allows this reaction to generate electricity is the electrolyte, which selectively transports charged particles from one electrode to the other. These charged molecules link the two reactions at the cathode and anode together and allow the overall reaction to occur. When the chemicals fed into the cell react at the electrodes, it creates an electrical current that can be harnessed as a power source.

Many different kinds of chemicals can be used in a fuel cell, such as natural gas or propane instead of hydrogen. A fuel cell is usually named based on the electrolyte used. Different electrolytes selectively transport different molecules across. The catalysts at either side are specialised to ensure that the correct reactions can occur at a fast enough rate.

For the Apollo missions, for example, NASA used alkaline fuel cells with potassium hydroxide electrolytes, but other types such as phosphoric acids, molten carbonates, or even solid ceramic electrolytes also exist.

The by-products to come out of a fuel cell all depend on what goes into it, however, their ability to generate electricity while creating few emissions, means they could have a key role to play in decarbonisation.

Fuel cells as a battery alternative

Fuel cells, like batteries, can store potential energy (in the form of chemicals), and then quickly produce an electrical current when needed. Their key difference, however, is that while batteries will eventually run out of power and need to be recharged, fuel cells will continue to function and produce electricity so long as there is fuel being fed in.

One of the most promising uses for fuel cells as an alternative to batteries is in electric vehicles.

Rachel Grima, a Research and Innovation Engineer at Drax, explains:

“Because it’s so light, hydrogen has a lot of potential when it comes to larger vehicles, like trucks and boats. Whereas battery-powered trucks are more difficult to design because they’re so heavy.”

These vehicles can pull in oxygen from the surrounding air to react with the stored hydrogen, producing only heat and water vapour as waste products. Which – coupled with an expanding network of hydrogen fuelling stations around the UK, Europe and US – makes them a transport fuel with a potentially big future.

Fuel cells, in conjunction with electrolysers, can also operate as large-scale storage option. Electrolysers operate in reverse to fuel cells, using excess electricity from the grid to produce hydrogen from water and storing it until it’s needed. When there is demand for electricity, the hydrogen is released and electricity generation begins in the fuel cell.

A project on the islands of Orkney is using the excess electricity generated by local, community-owned wind turbines to power a electrolyser and store hydrogen, that can be transported to fuel cells around the archipelago.

Fuel cells’ ability to take chemicals and generate electricity is also leading to experiments at Drax for one of the most important areas in energy today: carbon capture.

Turning CO2 to power

Drax is already piloting bioenergy carbon capture and storage technologies, but fuel cells offer the unique ability to capture and use carbon while also adding another form of electricity generation to Drax Power Station.

“We’re looking at using a molten carbonate fuel cell that operates on natural gas, oxygen and CO2,” says Grima. “It’s basic chemistry that we can exploit to do carbon capture.”

The molten carbonate, a 600 degrees Celsius liquid made up of either lithium potassium or lithiumsodium carbonate sits in a ceramic matrix and functions as the electrolyte in the fuel cell. Natural gas and steam enter on one side and pass through a reformer that converts them into hydrogen and CO2.

On the other side, flue gas – the emissions (including biogenic CO2) which normally enter the atmosphere from Drax’s biomass units – is captured and fed into the cell alongside air from the atmosphere. The CO2and oxygen (O2) pass over the electrode where they form carbonate (CO32-) which is transported across the electrolyte to then react with the hydrogen (H2), creating an electrical charge.

“It’s like combining an open cycle gas turbine (OCGT) with carbon capture,” says Grima. “It has the electrical efficiency of an OCGT. But the difference is it captures CO2 from our biomass units as well as its own CO2.”

Along with capturing and using CO2, the fuel cell also reduces nitrogen oxides (NOx) emissions from the flue gas, some of which are destroyed when the O2and CO2 react at the electrode.

From the side of the cell where flue gas enters a CO2-depleted gas is released. On the other side of the cell the by-products are water and CO2.

During a government-supported front end engineering and design (FEED) study starting this spring, this CO2 will also be captured, then fed through a pipeline running from Drax Power Station into the greenhouse of a nearby salad grower. Here it will act to accelerate the growth of tomatoes.

The partnership between Drax, FuelCell Energy, P3P Partners and the Department of Business, Energy and Industrial Strategy could provide an additional opportunity for the UK’s biggest renewable power generator to deploy bioenergy carbon capture usage and storage (BECCUS) at scale in the mid 2020s.

From powering space ships in the 70s to offering greenhouse-gas free transport, fuel cells continue to advance. As low-carbon electricity sources become more important they’re set to play a bigger role yet.

Learn more about carbon capture, usage and storage in our series:

What makes a mountain right for energy storage

22 May 2019

Power generation
Cruachan pylons

Electricity generation is often tied to a country’s geography, climate and geology. As an island Great Britain’s long coastline makes off-shore wind a key part of its renewable electricity, while Iceland can rely on its geothermal activity as a source of power and heat.

One of the most geographically-influenced sources of electricity is hydropower. A site needs a great enough volume of water flowing through it and the right kind of terrain to construct a dam to harness it. Even more dependent on the landscape is pumped hydro storage.

Pumped storage works by pumping water from one source up a mountain to a higher reservoir and storing it. When the water is released it rushes down the same shafts it was pumped up, spinning a turbine to generate electricity. The advantage of this is being able to store the potential energy of the water and rapidly deliver electricity to plug any gaps in generation, for example when the wind suddenly dropsor when Great Britain instantly requires a lot more power.

This specific type of electricity generation can only function in a specific type of landscape and the Scottish Highlands offers a location that ticks all the boxes.

The perfect spot for pumped storage

Cruachan Power Station, a pumped hydro facility capable of providing 440 megawatts (MW) of electricity, sits on the banks of Loch Awe in the Highlands, ready to deliver power in just 30 seconds.

“Here there is a minimum distance between the two water sources with a maximum drop,” says Gordon Pirie, Civil Engineer at Cruachan Power Station, “It is an ideal site for pumped storage.”

The challenge in constructing pumped storage is finding a location where two bodies of water are in close proximity but at severely different altitudes.

From the Lochside, the landscape rises at a dramatic angle, to reach 1,126 metres (3,694 feet) above sea level at the summit of Ben Cruachan, the highest peak in the Argyll. The crest of Cruachan Dam sits 400.8 metres (1,315 feet) up the slopes, creating a reservoir in a rocky corrie between ridges. The four  100+ MW turbines, which also act as pumps, lie a kilometre inside the mountain’s rock.

“The horizontal distance and the vertical distance between water sources is what’s called the pipe-to-length ratio,” explains Pirie. “It’s what determines whether or not the site is economically viable for pumped storage.”

The higher water is stored, the more potential energy it holds that can be converted into electricity. However, if the distance between the water sources is too great the amount of electricity consumed pumping water up the mountain becomes too great and too expensive.

The distance between the reservoir and the turbines is also reduced by Cruachan Power Station’s defining feature: the turbine hall cavern one kilometre inside the mountain…

Carving a power station out of rock

The access tunnel, cavern and the networks of passageways and chambers that make up the power station were all blasted and drilled by a workforce of 1,300 men in the late 1950s to early 1960s, affectionately known as the Tunnel Tigers.

This was dangerous work, however the rock type of the mountainside was another geographic advantage of the region. “It’s the diorite and phyllite rock, essentially granite, so it’s a hard rock, but it’s actually a softer type of granite, and that’s also why Cruachan was chosen as the location,” says Pirie.

The right landscape and geology was essential for establishing a pumped storage station at Cruachan, however, the West Highlands also offer another essential factor for hydropower: an abundance of water.

Turning water to power

The West Highlands are one of the wettest parts of Europe, with some areas seeing average annual rain fall of 3,500 millimetres (compared to 500 millimetres in some of the driest parts of the UK). This abundance of water from rainfall, as well as lochs and rivers also contributes to making Cruachan so well-suited to pumped storage.

The Cruachan reservoir can contain more than 10 million cubic metres of water. Most of this is pumped up from Loch Awe, which at 38.5 square kilometres is the third largest fresh-water loch in Scotland. Loch Awe is so big that if Cruachan reservoir was fully released into the loch it would only increase the water level by 20 centimetres.

However, the reservoir also makes use of the aqueduct system made up of 19 kilometres of tunnels and pipes that covers 23 square kilometres of the surrounding landscape, diverting rainwater and streams into the reservoir. Calculating quite how much of the reservoir’s water comes from the surrounding area is difficult but estimates put it at around a quarter.

“There are 75 concrete intakes dotted around the hills to gather water and carry it through the aqueducts to the reservoir,” says Pirie. “The smallest intake is about the size of a street drain in the corner of a field and the largest one is about the size of a three-bedroom house.”

Pumped storage stations offer the electricity system a source of extra power quickly but it takes the right combination of geographical features to make it work. Ben Cruachan just so happens to be one of the spots where the landscape makes it possible.

Is there such a thing as energy ‘terroir’?

16 April 2019

Power generation

‘Terroir’ comes from the French word ‘terre’, meaning land, earth or soil. In the French wine industry, it refers to the land from which grapes are grown. It is believed the terroir gives the grapes a unique quality specific to that particular growing site.

Terroir dictates the type of wine that comes from a region – it’s the reason we call one bottle a Bordeaux, and another a Côtes Du Rhone.

But could the idea of terroir hold relevance beyond just wine? What if we looked at electricity in the same way?

Certain environments are better placed to produce certain types of electricity.

These are some of the regions making the most of their unique location and landscape to produce electricity that makes sense for them.

La Rance tidal barrage

Brittany, France

Brittany boasts one third of mainland France’s coasts, and has long been a top destination for surfers, with waves as high as 7.6 metres in some places. With such tempestuous waters, it’s the perfect location for La Rance Tidal Power Station –the world’s first station of its kind. Opened in 1966, the site was chosen because it has the highest tidal range in France.

Tidal barrages like La Rance harness the potential energy in the difference in height between low and high tides.

The barrage creates an artificial reservoir to enable different water levels, which then drives turbines and generators to produce electricity.

While the station has been operating for close to 50 years, old tidal mills are still dotted around the Rance river, some dating back to the 15th century – proof that tidal power has deep roots in this region.

Xinjiang, China  

Whilst China may have some of the world’s most polluted cities, it is also the world’s biggest producer of renewable energy – including wind power. With one of the largest land masses on the planet, one in every three of the world’s wind turbines is in China, with the government installing one per hour in 2016.

In places like Xinjiang, China’s most westerly province, the windy weather used to be a nuisance, with overturned lorries and de-railed trains being a regular sight. This is caused by mountain ranges between Dabancheng and Ürümqi which form a natural wind tunnel, increasing the wind speed as air passes through. These days the region is harnessing this same wind to produce incredible amounts of electricity – with 27.8 terwatt hours (TWh) of electricity coming from the region in the first nine months of 2018.

Onshore wind farm in Xinjiang

Xinjiang local Wu Gang founded Goldwind to build China’s first windfarm here in the 1980s. Today it’s the world’s second largest turbine maker. The turbines work on a simple premise: wind turns the turbine blades which are connected to a rotor, causing it to spin. This in turn is connected to a generator, which takes the wind’s kinetic energy to produce electricity.

Hengill, Iceland

Iceland sits where the North American and Eurasian tectonic plates meet, meaning that magma rises close to the surface, bringing with it a lot of energy potential. One example of how the Icelandic people are harnessing this power is The Hellisheiði, the second largest geothermal power station in the world.

Here, high-pressure geothermal steam is extracted from 30 wells, ranging from 2,000 to 3,000 metres deep, and is used to turn turbines and generate electricity. This renewable plant has a capacity of 303 megawatts (MW) of electricity, which is used to power the capital city of Reykjavik.

The site was chosen due to its location in the Hengill volcanic area in the south of Iceland, one of the most active geothermal areas on the planet. Here, a giant magma chamber sits underground, with thousands of hot springs above. According to Iceland’s National Energy Authority, geothermal power from sites like this accounts for 25% of the country’s electricity production and 66% of primary energy usage.

But Icelanders aren’t only using the geothermal landscape for energy production – chefs here can cook food simply by burying it in the ground, producing delicacies like rúgbrauð, which translates as ‘hot spring bread’.

Ouarzazate, Morocco

From Iceland’s below-zero temperatures to Morocco, a popular holiday destination for sun-seekers, with 330 days of sunshine a year. Morocco lays claim to a chunk of the Sahara Desert, famously known as one of the hottest climates in the world. Where better, then, to situate the world’s largest solar thermal power plant?

Noor solar thermal plant

The Moroccan city of Ouarzazate, nicknamed the ‘door of the desert’ plays host to the huge Noor Complex, which is still under construction and is being implemented in four parts. The latest piece of the puzzle is Noor III, which was hooked up to Morocco’s electricity grid last year. Here, 7,400 mirrors reflect sun rays onto Noor III’s tower, the highest solar-thermal tower in the world, concentrating at the top of the building to create around 500ºC of heat. This heats up the molten salts inside the tower, which travel through a series of pipes, creating high pressure steam. This steam then moves a turbine to generate electricity.

Molten salts are used at Noor III because they can operate at high temperatures and store heat effectively, so that the site can continue to produce energy for up to 7.5 hours when there’s no sun. Once up and running, the plant will generate enough energy to power 120,000 homes with no atmospheric emissions of carbon dioxide (CO2). Along with the other projects at the Noor Complex, Noor III is helping Morocco to achieve its goal of obtaining 42% of its power from renewable sources by 2020.

Ben Cruachan, Scotland

The sun rays that shine on the Noor Complex are few and far between in the Highlands, but there are mountains a-plenty – Ben Cruachan being one of them. Ben Cruachan is the highest point in the Argyll and Bute area of Scotland and is right next to the picturesque Loch Awe. This provides the backdrop for the world’s first high head reversible pumped-storage hydro scheme, built by British engineer Edward McColl over 50 years ago.

Cruachan Power Station’s reservoir and Loch Awe, viewed from the top of Ben Cruachan

With the help of a 4,000-strong army of workers nicknamed the Tunnel Tigers, McColl turned the slopes of Ben Cruachan into a geological battery which Great Britain still relies on today.

It works by using excess electricity on the national grid to pump water from Loch Awe at the foot of the mountain up to the Cruachan Reservoir 300 metres above. During times of heightened demand – like when everyone puts the kettle on during a Coronation Street ad break or when the wind speed suddenly drops around breakfast time – this water is released back down the mountain to turn the turbines that live inside the hollowed mountain.

In this way, Cruachan Power Station can meet the nation’s energy needs within seconds, whereas gas or nuclear stations would take many tens of minutes or hours to reach such capacity.

While Ben Cruachan lends itself perfectly to this pumped-storage hydro facility, it is only one of four such sites in the UK. The challenge in installing more is that there are only a few sites which are mountainous with suitably large bodies of water nearby – things that are inherently necessary for pumped-storage hydroelectricity.

The growing importance of ‘terroir’

All of these places embrace the land around them to produce energy in inventive ways, and as levels of decarbonisation grow around the world, there are an increasing number of places using what’s available close to home for energy solutions.

Take Barbados, a country that has traditionally relied on imported fossil fuels for 96% of its electricity. But with short driving distances and 220 days of pure sunlight every year, the government has seen the potential for electric vehicles run by solar power. With modular solar carports now a regular sight in Barbados, the island has become one of the world’s top users of EVs – preserving the picturesque landscape and reducing its dependence on imported petrol.

Solar panels above an office car park in Barbados

Meanwhile Palau, a small Pacific island nation, is building the world’s largest microgrid, consisting of 35 MW of solar panels and 45 MWh of energy storage. For a nation threatened by rising sea levels, making use of its geographic features allows it to work towards its 70% renewable energy target by 2050 and reduce its reliance on imports.

As more countries continue to move away from fossil fuels, taking advantage of their unique ‘terroir’ will increasingly enable them to produce electricity that works with their landscape.

When would you need a battery the size of a mountain?

11 March 2019

Power generation
Turbine hall, Cruachan Power Station

What’s the biggest battery you can think of? A car battery? A grid-scale lithium-ion array? What about a battery the size of a mountain?

That’s what you’ll find on the banks of Loch Awe in Argyll, Scotland. Cruachan Power Station is a pumped hydro storage facility comprised of nearly 20 km of tunnels and chambers cutting through the mountain of Ben Cruachan.

Built in the 1960s, the site, known as ‘The Hollow Mountain’ entails a subterranean power station, a reservoir, a dam, and the loch itself. These components all work together to store a huge amount of energy, or enough to power more than 880,000 homes, at a moment’s notice.

This probably doesn’t fit your image of what a battery looks like. But the principle is the same. The purpose of any battery, from the AAs in your remote control to the one in your phone that you charge every night, is to store power for future use.

In an AA battery, that storage takes the form of chemicals within the battery which release electricity under the right conditions. In pumped hydro, the purpose is the same, but instead of being stored in chemicals, that energy is stored in the gravitational potential energy of 10 million cubic meters of water, sitting poised to spin Cruachan’s turbines and generate 440 megawatts (MW) of electricity.

Such a huge amount of water is the equivalent of around seven gigawatt-hours (GWh) of energy. If the reservoir is full, the Hollow Mountain can power a city for more than 15 hours.

How pumped hydro works

Cruachan Power Station is one of only four such storage facilities in the UK. Inside the mountain, 396 metres beneath the surface, is a chamber about the size of a football pitch, and the height of a seven-storey building. Here sit four electricity-generating turbines, each weighing around 650 tonnes.

A series of tunnels and channels connect these turbines to two enormous bodies of a water: Loch Awe at the base and the Ben Cruachan reservoir further up the mountain.

The turbines can function both as pumps and as generators. When there is an excess of power on the grid, and electricity is cheap, the turbines consume electricity and work to pump water up from the loch below to the reservoir 300 metres above.

Then, when electricity demand rises, the turbines reverse direction. Now the water flows down from the reservoir and through the turbines, which switch to generating electricity and supply it to the grid.

This is an extremely quick process. Unlike coal or nuclear stations, which can take hours to get up to full capacity, Cruachan can go from standstill to generating within two minutes – perfect for reacting to variance in grid demand at short notice.

Often National Grid ESO (electricity system operator) keeps one or more of Cruachan’s four units spinning in air. Compressed air is used to evacuate water from around a turbine to allow it to spin. When necessary, it can go from zero megawatts to 100 MW or more in less than 30 seconds.

In any given day, the system operator may call on Cruachan Power Station multiple times as the requirements to manage the grid constantly change.

Cruachan is a net generator of power across the year thanks to the large amount of water flowing into its reservoir from a system of aqueducts. However, pumped hydro is primarily about storing energy – not actively producing it in the way wind, solar, gas, biomass or conventional hydropower facilities might.

In fact, the UK’s four pumped hydro power stations are a combined net consumer of electricity. But this is the case with regular batteries as well, when construction is factored in.

Nevertheless, pumped hydro storage is still efficient – around 70% to 80% of the electricity used in pumping is recovered in generation. Sometimes, the convenience of getting access to power when it’s needed is more valuable than how much power is conserved.

The need for storage

But why store so much energy in such an improbable location to begin with?

There are two key reasons: The first is that the grid doesn’t operate under the same conditions all the time. Great Britain will use more or less electricity owing to its needs. For example, overnight there is a lower demand than at 5pm on a weekday evening. This means sometimes the grid is demanding more electricity than is being supplied, and sometimes vice versa.

Secondly, there’s the increasing level of intermittent energy sources, like wind and solar, supplying low carbon electricity. These sources are highly dependent on the weather and can’t be easily turned up or down in response to grid conditions.

Batteries can address these two issues. In times of higher electricity supply than demand, storage systems can absorb and store electricity from the grid, which helps balance frequency and prevent surges; and in times of high demand, then can quickly deliver electricity where it’s needed.

Pumped hydro is an important part of this equation – in fact, while other types of grid-scale batteries are receiving significant investment, they are still in their infancy. Pumped storage, by contrast, already accounts for 95% of all installed storage capacity in the world, around 130 GW.

What does the future hold for pumped hydro?

One of the challenges in installing more pumped hydro storage is finding suitable geography – places which are both mountainous, with nearby suitably large bodies of water.

However, there have been experiments into river and tidal-based pumped hydro storage projects. Senator Wash Dam on the Colorado River uses pumping to store water upstream from the Imperial Hydropower Dam so it can be released when needed, while the Rance Tidal Power Station in France pumps sea water behind the barrage to allow it to start up faster.

Storage solutions will become more important as electricity systems increasingly move towards renewable and low carbon sources. Pumped storage helps to meet peak-time demand and provide grid stability by making use of the landscape and gravity to deliver electricity when it’s needed.

Guided tours of Cruachan: The Hollow Mountain are available via VisitCruachan.co.uk

The small devices that use lots of power and the big buildings that don’t

23 January 2019

Electrification

When Texas Instruments set about attempting to create the world’s first handheld calculator in the early sixties, it estimated that such a complicated device might require a battery as big and powerful as a car’s.

With some innovative thinking, the team were eventually able to power the device with just a five-volt battery, turning the calculator into a truly handheld device and kickstarting an electronics efficiency revolution. Continuous advances in the space mean that today’s super-powered smartphones run on more efficient, powerful – and smaller – sources than ever before.

But as more of our devices become ‘smart’ and grow in usage, their electricity demand is also increasing. On the other hand, many bigger objects that traditionally have used a lot of power are becoming more efficient and consuming less electricity than before.

The small devices eating up electricity

Think of the most electricity-intensive appliance in a home. Something constantly running like a fridge-freezer might come to mind – or something intensive that operates in short blasts like a hairdryer or kettle.

However, a surprising drain of electricity in homes is TV set-top boxes and consoles, which as recently as 2016 were reported to account for as much as half of all electricity usage by domestic electronics. This is because of how often they are left in standby mode, which means they are constantly using a small amount of electricity.

In 1999 the International Energy Agency (IEA) introduced the One Watt Initiative, which led to the electricity consumption of many devices on standby falling from around five watts to below one watt. And while this has helped reduce standby or ‘vampire power’, multiplied across the country – the electricity consumption becomes significant (in the UK there are an estimated 27 million TVs).

This is not just a TV-specific problem, however, it is symptomatic of many of the modern devices increasingly found in our homes, from smart lightbulbs to Amazon’s Alexa. These are constantly using small amounts of electricity, listening and connecting to the cloud even when not being directly used.

In 2014 the IEA estimated that by 2020 these networked-devices could result in $120 billion in wasted electricity. Adding to this is the increasing demand of the cloud and data storage, which has been estimated could account for 20% of the world’s electricity consumption by 2025.

Previous alarm bells surrounding the bitcoin network’s electricity usage highlights that it’s not just physical, connected objects that will put increasing pressure on electricity supply, but also entirely digital products.

Yet even as little things become smarter and require more electricity, some big things that have previously consumed huge amounts of electricity are becoming more efficient.

The big things becoming more efficient   

Buildings are a big source of electricity demand globally. Office blocks full of lights and blasting heating and air-conditioning units are among the main offenders, but poorly insulated homes that leak heat also have a significant impact.

Efforts are constantly being undertaken to reduce this via technological means such as companies generating their own electricity onsite from installed renewables. But cutting interstitial demand to a minimum doesn’t always have to be hi-tech.

The Bullitt Centre in Seattle is a 50,000 ft2office aiming to be ‘the greenest commercial building  in the world’. This is achieved in part through a rooftop solar array that allows the building to generate more electricity than it consumes, but is complimented by more straightforward steps such as maximising natural light and ventilation, collecting rainwater, and the use of geothermal heat pumps. On average the building consumes 230,000 kilowatt-hours (KWh)/year compared to the average of 1,077,000 KWh/year for Seattle offices.

Retrofitting can also make notable reductions to energy usage and New York art-deco icon, the Empire State Building, has been updated to consume 40% less electricity. This is largely thanks to straightforward renovations such as ensuring windows open properly and temperatures can be easily controlled.

Energy efficiency is even extending beyond the confines of the planet. The International Space station only consumes about 90 kW to run, which comes from a solar array stretching more than 2,400m2. When its solar panels are operational about 60% of their generation is used to refill batteries for when the station is in the Earth’s shadow.

The Mars Desert Research Station (MDRS) in Utah

Technology like this will be essential if humans are going to put buildings on other planets where we will not have vast electricity generation and transmission systems we enjoy on earth. And if that is the ambition, continuously striving for ever more efficient devices on a smarter power grid is only going to help progress us further.