Tag: national grid

How to count carbon emissions

Iain Staffell, Imperial College London

31 August 2020

Opinion

Reduced demand, boosted renewables, and the near-total abandonment of coal pushed last quarter’s carbon emissions from electricity generation below 10 million tonnes.

Emissions are at their lowest in modern times, having fallen by three-quarters compared to the same period ten years ago.  The average carbon emissions fell to a new low of 153 grams per kWh of electricity consumed over the quarter.

The carbon intensity also plummeted to a new low of just 18 g/kWh in the middle of the Spring Bank Holiday.  Clear skies with a strong breeze meant wind and solar power dominated the generation mix.

Together, nuclear and renewables produced 90% of Britain’s electricity, leaving just 2.8 GW to come from fossil fuels.

The generation mix over the Spring Bank Holiday weekend, highlighting the mix on the Sunday afternoon with the lowest carbon intensity on record

National Grid and other grid-monitoring websites reported the carbon intensity as being 46 g/kWh at that time.  That was still a record low, but very different from the Electric Insights numbers.  So why the discrepancy?

These sites report the carbon intensity of electricity generation, as opposed to consumption.  Not all the electricity we consume is generated in Britain, and not all the electricity generated in Britain is consumed here.

Should the emissions from power stations in the Netherlands ‘count’ towards our carbon footprint, if they are generating power consumed in our homes?  Earth’s atmosphere would say yes, as unlike air pollutants which affect our cities, CO2 has the same effect on global warming regardless of where it is produced.

On that Bank Holiday afternoon, Britain was importing 2 GW of electricity from France and Belgium, which are mostly powered by low-carbon nuclear.  We were exporting three-quarters of this (1.5 GW) to the Netherlands and Ireland.  While they do have sizeable shares of renewables, they also rely on coal power.

Britain’s exports prevented more fossil fuels from being burnt, whereas the imports did not as they came predominantly from clean sources.  So, the average unit of electricity we were consuming at that point in time was cleaner than the proportion of it that was generated within our borders.  We estimate that 1190 tonnes of CO2 were produced here, 165 were emitted in producing our imports, and 730 avoided through our exports.

In the long-term it does not particularly matter which of these measures gets used, as the mix of imports and exports gets averaged out.  Over the whole quarter, carbon emissions would be 153g/kWh with our measure, or 151 g/kWh with production-based accounting.  But, it does matter on the hourly timescale, consumption based accounting swings more widely.

Imports and exports helped make the electricity we consume lower carbon on the 24th, but the very next day they increased our carbon intensity from 176 to 196 g/kWh.

When renewable output is high in Britain we typically export the excess to our neighbours as they are willing to pay more for it, and this helps to clean their power systems.  When renewables are low, Britain will import if power from Ireland and the continent is lower cost, but it may well be higher carbon.

Two measures for the carbon intensity of British electricity over the Bank Holiday weekend and surrounding days

This speaks to the wider question of decarbonising the whole economy.

Should we use production or consumption based accounting?  With production (by far the most common measure), the UK is doing very well, and overall emissions are down 32% so far this century.  With consumption-based accounting it’s a very different story, and they’re only down 13%*.

This is because we import more from abroad, everything from manufactured goods to food, to data when streaming music and films online.

Either option would allow us to claim we are zero carbon through accounting conventions.  On the one hand (production-based accounting), Britain could be producing 100% clean power, but relying on dirty imports to meet its entire demand – that should not be classed as zero carbon as it’s pushing the problem elsewhere.  On the other hand (consumption-based accounting), it would be possible to get to zero carbon emissions from electricity consumed even with unabated gas power stations running.  If we got to 96% low carbon (1300 MW of gas running), we would be down at 25 g/kWh.  Then if we imported fully from France and sent it to the Netherlands and Ireland, we’d get down to 0 g/kWh.

Regardless of how you measure carbon intensity, it is important to recognise that Britain’s electricity is cleaner than ever.

The hard task ahead is to make these times the norm rather than the exception, by continuing to expand renewable generation, preparing the grid for their integration, and introducing negative emissions technologies such as BECCS (bioenergy with carbon capture and storage).

Read full Report (PDF)   |  Read full Report   |   Read press release

Front cover of Drax Electric Insights Q2 2020 report

Electric Insights Q2 2020 report [click to view/download]

The cost of staying in control

Iain Staffell, Imperial College London

Opinion
What: Industrial landscape with cables, pylons and train at sunset Where: Somerset, UK When: January 2016

The cost of keeping Britain’s power system stable has soared, and now adds 20% onto the cost of generating electricity.

The actions that National Grid takes to manage the power system have typically amounted to 5% of generation costs over the last decade, but this share has quadrupled over the last two years.  In the first half of 2020, the cost of these actions averaged £100 million per month.

Supplying electricity to our homes and workplaces needs more than just power stations generating electricity.

Supply and demand must be kept perfectly in balance, and flows of electricity around the country must be actively managed to keep all the interconnected components stable and prevent blackouts.  National Grid’s costs for taking these actions have been on the rise, as we reported over the previous two summers; but recently they have skyrocketed.

At the start of the decade, balancing added about £1/MWh to the cost of electricity, but last quarter it surpassed £5/MWh for the first time (see below).

Balancing prices have risen in step with the share of variable renewables.  The dashed line below shows that for every extra percent of electricity supplied by wind and solar adds 10 pence per MWh to the balancing price.  Last quarter really bucks this trend though, and balancing prices have risen 35% above the level expected from this trend.  The UK Energy Research Centre predicted that wind and solar would add up to £5/MWh to the cost of electricity due to their intermittency, and Britain has now reached this point, albeit a few years earlier than expected.

This is partly because keeping the power system stable is requiring more interventions than ever before.  With low demand and high renewable generation, National Grid is having to order more wind farms to reduce their output, at a cost of around £20 million per month.  They even had to take out a £50+ million contract to reduce the output from the Sizewell B nuclear reactor at times of system stress.

Two charts illustrating the costs of balancing Great Britain's power system

[Left] The quarterly-average cost of balancing the power system, expressed as a percentage of the cost of generation. [Right] Balancing price shown against share of variable renewables, with dots showing the average over each quarter

A second reason for the price rise is that National Grid’s costs of balancing are passed on to generators and consumers, who pay per MWh.  As demand has fallen by a sixth since the beginning of the coronavirus pandemic, the increased costs are being shared out among a smaller base.  Ofgem has stepped in to cap the balancing service charges at a maximum of £10/MWh until late October.  Their COVID support scheme will defer up to £100 million of charges until the following year.

For a quarter of a century, the electricity demand in GB ranged from 19 to 58 GW*.  Historically, demand minus the intermittent output of wind and solar farms never fell below 14 GW.  However, in each month from April to June this year, this ‘net demand’ fell below 7 GW.

Just as a McLaren sports car is happier going at 70 than 20 mph, the national grid is now being forced to operate well outside its comfort zone.

This highlights the importance of the work that National Grid must do towards their ambition to be ready for a zero-carbon system by 2025.  The fact we are hitting these limits now, rather than in a few years’ time is a direct result of COVID.  Running the system right at its limits is having a short-term financial impact, and is teaching us lessons for the long-term about how to run a leaner and highly-renewable power system.

Chart: Minimum net demand (demand minus wind and solar output) in each quarter since 1990

Minimum net demand (demand minus wind and solar output) in each quarter since 1990

Read full Report (PDF)   |  Read full Report   |   Read press release

Front cover of Drax Electric Insights Q2 2020 report

Electric Insights Q2 2020 report [click to view/download]

What is the national grid?

21 August 2020

Power generation
Electricity grid

What is the grid?

The national grid, or simply the grid, is the network of powerlines, pylons, gas lines and interconnectors that makes up Great Britain’s electricity and gas systems — and the engineers, technology and rules responsible for their seamless operation. It ensures electricity generated anywhere, by any source, can be transmitted to meet the demand for power wherever it’s needed across the country. It heats homes and businesses. It helps us to cook our food.

The national electricity grid consists of a high voltage transmission system, which connects electricity from power stations to substations and smaller local networks – called Distribution Network Operators, or DNOs – which transport electricity into homes and businesses.

Key national grid facts

How does it work?

Transporting electricity around the grid is more complicated than just connecting cables to power generators. In order to move power around the country, things like voltage and frequency of electricity must be balanced and kept uniform at all times. Without this, unstable electricity could damage equipment and ultimately lead to blackouts.

The National Grid Electricity System operator (ESO) is a separate entity from the National Grid company, and is responsible for maintaining the correct voltage, frequency and reserve power levels to ensure electricity is transmitted safely and efficiently at all times.

It does this by working with power generators and energy storage facilities to provide what are known as ‘ancillary services’ – a set of processes that keep the power system in operation, stable and balanced.

The national grid is the network of power stations, powerlines and electricity infrastructure that allows electricity to be generated, transported and used across the country.

Who controls it?

In Great Britain the National Grid company owns and operates the transmission systems which ensure electricity is delivered safely and reliably across the country.

The local distribution system is made up of 14 regional DNO companies, which deliver electricity at a lower voltage from substations to homes and businesses.

Great Britain’s grid incudes England, Scotland, Wales and several surrounding islands. Northern Ireland is part of an island-wide electricity system with the Republic of Ireland.

National grid fast facts

  • Great Britain’s grid is made up of more than 7,000 kilometres of cables, 90,000 pylons, 346 substations, and 1,500 kilometres of underground cables
  • Construction of the grid began on 14 July 1928 and was completed on 5 September 1933
  • It was originally designed to operate as 7 separate, connected grids, before a group of rebellion engineers attempted to run it as one on 29 October 1938. It has run as one grid ever since
  • A decade ago, Britain had 80 individual points of generation to manage. Today there are nearly one million
  • All electricity in Great Britain operates at a frequency of 50Hz. A deviation of just 1% above or below could cause damage

How is the grid changing?

As the sources that generate Great Britain’s electricity change to include more renewables, the grid has also changed.

The grid was built to work with large power stations that operate huge spinning turbines. With decarbonisation it’s evolved to include a greater variety of intermittent weather dependent sources such as wind, solar and decentralised power sources that serve individual buildings or communities.

This makes managing the grid’s stability more complicated, and requires the use of more ancillary services, usually delivered by flexible generators such as thermal power stations.

Go deeper

What are ancillary services?

Power generation
Ancillary services

What are ancillary services?

Ancillary services are a set of processes that enable the transportation of electricity around the grid while keeping the power system operating in a stable, efficient and safe way.

Why do we need ancillary services? 

When electricity makes its way through the country, it needs to be managed so that the power generation and electricity useage levels are equal.

The regulating of elements such as frequency and voltage has to be carefully managed, so that the massive amounts of electricity moving – or transmitted – are able to be used safely in homes,  businesses, schools and hospitals around the country.

Ancillary services enable the power system to operate in a stable, efficient and safe way.

 What do ancillary services offer?

Ancillary services include a wide variety of electrical efficiency and safety nets, all focussed on ensuring the power system delivers enough output to meet demand yet remains stable:

Frequency: The UK’s power system runs at a frequency of 50 hertz – to stay balanced, it has to remain at that frequency. Turbines and generators adjust the speed at which they spin automatically to increase or decrease power in line with demand and ensure that the system is kept stable.

Voltage: Different parts of the UK’s transmission system use voltages of either 400, 275 or 132 kilovolts. To ensure that voltage remains within 5% of those figures at all times, to be safe for domestic electricity use, power stations can produce or re-absorb excess energy as reactive power, keeping the overall system reliable.

Inertia: Turbine use is important in keeping the system operating in its current state, even with disruptions and sudden changes. The electricity system uses the weight of heavy spinning turbines to create stability, acting as dampeners and smoothing out unexpected changes in frequency across the network.

Reserve: An important part of ancillary servicing is making sure that there are no surprises – so holding back powerto release if something unexpected happens means that the network can function confidently, knowing that there are generators and other power providers such as pumped hydro storage waiting ready to back it up.

Key facts about ancillary services

Who manages ancillary services?

In the UK the grid’s stability is managed by National Grid Electricity System Operator (ESO) – a  separate company of National Grid Electricity Transmission (ET). The ESO works with ancillary service providers to either sign long-term contracts or make short term requests for a service.

These partners are often power stations, such as Drax Power Station, which have large spinning turbines capable of controlling voltage, frequency, providing inertia and serving as a source of reserve power. 

What is the future of ancillary services, as we move to a more renewable system?

As the UK’s electricity system continues to change, so to do its requirements for different ancillary services. The switch from a few very large power stations to a greater variety of different electricity sources, some of which may be dependent on the weather, as well as changes in how the country uses electricity, means there is a greater need for ancillary services to keep the grid stable.

These services have historically been delivered by thermal power stations, but new innovations are enabling wind turbines to provide inertial response and overcome changes in frequency, and batteries to store reserve power that can then be supplied to the power system to ensure balance.

Ancillary Services

Ancillary services fast facts  

  • Batteries can in some cases be cheaper ancillary alternatives to conventional sources of energy. The Hornsdale Power Reserve, which runs on a Tesla battery in South Australia, lowered the price of frequency ancillary services by 90% after just four months of use.
  • Ancillary services usually work from habit; knowing when to slow electricity production, or increase supply based around the general public’s standard working hours, dinner time and the early morning rush.
  • But during the COVID-19 lockdown, electricity consumption on weekdays fell by 13% and so National Grid ESO had to intervene with ancillary services to keep the lights on.
  • Every year, the ESO’s ancillary services move 300 terawatt hours (TWh) of electricity, which is equal to 4 trillion kettles boiling at once.

With recent innovations around renewable energies, there are a wider variety of ways for ancillary services to generate power.

Go deeper

Button: What is decarbonisation?

The ideas and tricks inside Great Britain’s plugs

15 July 2020

Electrification
Rewiring a UK 13 amp domestic electric plug

It may be bulkier than its foreign cousins and its flat back might make it the perfect household booby trap, but the UK plug is a modern-day design marvel.

The UK’s ‘G Type’ (or BS 1363) plug is a product of the post-war age. But it has endured for the better part of a century, ensuring homes, business and sockets around the UK have access to safe, usable electricity. Even as the devices they power have changed, become smarter and more connected, the three-prong G Type remains unchanged.

But to understand how it came into being, it’s worth first understanding what makes it such a unique and clever bit of design – including its role in achieving the ambitions of one of Great Britain’s pioneering female engineers, and its money-saving abilities.

What makes Great Britain’s plugs special

The modern plug used across Great Britain (as well as Ireland, Cyprus, Hong Kong and Malaysia) is a smarter and more advanced item than many of its contemporaries. This is thanks to a number of key, but often overlooked, features.

The UK plug is a

A collection of international power point illustrations

The first is its earth prong. Connecting the plug to the earth means if a wire comes loose in, say, a toaster and touches a metal part, the device will short circuit as the electricity runs through to make contact with the earth, rather than the entire item becoming electrified and dangerous.

The longer earth prong also plays the role of ‘gatekeeper’ for the entire plug. When a plug enters a socket the longer earth prong enters before any others, pushing back plastic shutters that sit over the live and neutral entrances. This means when there is no plug in a socket the live and neutral ports, which actually carry electric current to devices, are covered over making it very difficult for a child to push anything dangerous into the socket.

Infographic: What makes the UK plug special?

What makes the UK plug special? [click to download]

Another clever feature inside the Great British plug comes in the form of a fuse connected to the live wire. If there’s an unexpected electrical surge the fuse will blow and cut off the connected device, preventing fires and electrocutions.

All packaged together, the G Type plug is far from the most compact version – yet it is hugely effective. However, these ideas didn’t come together at the flick of a switch.

Pre-war plugs

Going back to end of the 19th Century, the idea of owning devices you could move around your house and connect to the electricity circuit from different rooms was novel.

Electricity’s main role in homes was for lighting and was fixed into walls and ceilings, with their cables hidden. It wasn’t until the rise of new electrical appliances in the 20th century that the need for an easy way to plug electrical items into circuits arose.

A series of two-pronged plugs first emerged in 1883, but there was no standardisation of design which would allow any appliance to be plugged into any socket. That began to change in 1904, when US inventor Harvey Hubbell developed a plug that allowed non-bulb electrical devices to be connected into an existing light socket, eliminating the need for the installation of new sockets.

By 1911, a design for a three-pronged plug with an earth connection had emerged, with manufacturer AP Lundberg bringing the first of this kind of plug to Britain.

By 1934, regulations appeared requiring plugs and sockets to include an earthing prong, which eventually gave birth to a three, cylindrical-pronged plug: the BS 546.

BS 546 plugs

The BS 546 was different from the modern G-Type as they didn’t contain a fuse and were available in five different sizes depending on the needs of the appliance, from small 2 ampere plugs for low-power appliances to a larger 30 ampere version for industrial machinery. The different sizes and spacing of the prongs prevented low-power devices accidentally being plugged into high-power outlets.

Any chance of globally standardising plugs was doomed from the beginning, as different companies in different countries all began developing their own plugs for their products as electricity rapidly gained uptake.

Some attempts were made by the International Electrotechnical Commission (IEC) to standardise plugs globally but the Second World War put a stop to any progress.   

Electricity for the people

Great Britain emerged from the Second World War with its national grid standing strong. The challenge now was to make electricity not just the power source of factories and wealthy people’s homes, but something available for everyone in the wave of new post-war construction.

Other countries, not seeing as much damage to their housing stock as the UK, did not have the same opportunity to rethink domestic electricity to such an extent. Therefore, the Institution of Electrical Engineers (IEE) assembled a 20-person committee to consider the electrical requirements of the country’s new homes.

Caroline Haslett

Breaking new ground: Caroline Haslett

The sole woman on the committee, Caroline Haslett, had been breaking new ground for female engineers since before World War One. In her career she worked with turbine inventor Charles Parsons and his wife (an engineer in her own right) and in 1932 became the first woman selected to join the IEE. Her passion for electricity went so far as for her will to request she be cremated via electricity.

She had long believed in the potential for domestic electricity to improve women’s lives by freeing them from the drudgery of pre-electric domestic chores, from handwashing clothes to cooking on coal-fuelled stoves. This included ensuring electricity was safe for the people using electricity around the home which in the 1940s was primarily women, who also did the vast majority of childcare.

Haslett’s drive to make electricity safe in the home was pivotal in shaping many of the IEE’s safety requirements for post-war domestic electricity, including what have become the country’s standard plugs and sockets.

There was another factor aside from safety at play. The material cost of the war meant copper, the main material used in electrical wiring, was in short supply, so the IEE came up with a new way of wiring homes that would in turn shape our plugs.

Shifting fuses to save copper

Before the war, British sockets were all separately wired back to a central fuse box. It made sense, because if something went wrong only the fuse connected to that socket would blow rather than the whole house.

However, to cut the amount of copper used the IEE instead proposed a clever workaround where the home’s electrical sockets are looped up in one Ring Circuit, with the fuses moved to the plugs themselves. So, if something went wrong in an appliance the fault would stop at the plug, where the fuse could easily be accessed and replaced. Lighting fixtures remained wired in a separate circuit from sockets as they require less current to operate.

Copper Wiring

Copper was short in supply during World War Two.

This hidden fuse, is a big differentiator from other plug types and adds to the G Type’s safety credentials. However, the IEE had to ensure people did not mistakenly insert older three-prong BS 546 plug styles without fuses into the sockets.

The answer was as simple as switching the socket holes from round to rectangle. It means the older round cylinder prongs wouldn’t fit into the slot designed for the rectangles found on plugs today.

The G Type plug might seem cumbersome compared to the European or US models, but in the 70-plus years since its introduction its three prongs and in-built fuse, has proved an enduring design that can power new devices and smart technology, while remaining one of the safest plugs in the world.

The UK needs negative emissions from BECCS to reach net zero – here’s why

7 April 2020

Carbon capture
Early morning sunrise at Drax Power Station

Reaching the UK’s target of net zero greenhouse gas emissions by 2050 means every aspect of the economy, from shops to super computers, must reduce its carbon footprint – all the way down their supply chains – as close to zero as possible.

But as the country transforms, one thing is certain: demand for electricity will remain. In fact, with increased electrification of heating and transport, there will be a greater demand for power from renewable, carbon dioxide (CO2)-free sources. Bioenergy is one way of providing this power without reliance on the weather and can offer essential grid-stability services, as provided by Drax Power Station in North Yorkshire.

Close up of electricity pylon tower

Close up of electricity pylon tower

Beyond just power generation, more and more reports highlight the important role the next evolution of bioenergy has to play in a net zero UK. And that is bioenergy with carbon capture and storage or BECCS.

A carbon negative source of power, abating emissions from other industries

The Committee on Climate Change (CCC) says negative emissions are essential for the UK to offset difficult-to-decarbonise sectors of the economy and meet its net zero target. This may include direct air capture (DAC) and other negative emissions technologies, as well as BECCS.

BECCS power generation uses biomass grown in sustainably managed forests as fuel to generate electricity. As these forests absorb CO2 from the atmosphere while growing, they offset the amount of CO2 released by the fuel when used, making the whole power production process carbon neutral. Adding carbon capture and storage to this process results in removing more CO2 from the atmosphere than is emitted, making it carbon negative.

Pine trees grown for planting in the forests of the US South where more carbon is stored and more wood inventory is grown each year than fibre is extracted for wood products such as biomass pellets

Pine trees grown for planting in the forests of the US South where more carbon is stored and more wood inventory is grown each year than fibre is extracted for wood products such as biomass pellets

This means BECCS can be used to abate, or offset, emissions from other parts of the economy that might remain even as it decarbonises. A report by The Energy Systems Catapult, modelling different approaches for the UK to reach net zero by or before 2050, suggests carbon-intensive industries such as aviation and agriculture will always produce residual emissions.

The need to counteract the remaining emissions of industries such as these make negative emissions an essential part of reaching net zero. While the report suggests that direct air carbon capture and storage (DACCS) will also play an important role in bringing CO2 levels down, it will take time for the technology to be developed and deployed at the scale needed.

Meanwhile, carbon capture use and storage (CCUS) technology is already deployed at scale in Norway, the US, Australia and Canada. These processes for capturing and storing carbon are applicable to biomass power generation, such as at Drax Power Station, which means BECCS is ready to deploy at scale from a technology perspective today.

As well as counteracting remaining emissions, however, BECCS can also help to decarbonise other industries by enabling the growth of a different low carbon fuel: hydrogen.

Enabling a hydrogen economy

The CCC’s ‘Hydrogen in a low-carbon economy report’ highlights the needs for carbon zero alternatives to fossil fuels – in particular, hydrogen or H2.

Hydrogen produced in a test tube

Hydrogen produced in a test tube

When combusted, hydrogen only produces heat and water vapour, while the ability to store it for long periods makes it a cleaner replacement to the natural gas used in heating today. Hydrogen can also be stored as a liquid, which, coupled with its high energy density makes it a carbon zero alternative to petrol and diesel in heavy transport.

There are various ways BECCS can assist the creation of a hydrogen economy. Most promising is the use of biomass to produce hydrogen through a method known as gasification. In this process solid organic material is heated to more than 700°C but prevented from combusting. This causes the material to break down into gases: hydrogen and carbon monoxide (CO). The CO then reacts with water to form CO2 and more H2.

While CO2 is also produced as part of the process, biomass material absorbs CO2 while it grows, making the overall process carbon neutral. However, by deploying carbon capture here, the hydrogen production can also be made carbon negative.

BECCS can more indirectly become an enabler of hydrogen production. The Zero Carbon Humber partnership envisages Drax Power Station as the anchor project for CCUS infrastructure in the region, allowing for the production of ‘blue’ hydrogen. Blue hydrogen is produced using natural gas, a fossil fuel. However, the resulting carbon emissions could be captured. The CO2 would then be transported and stored using the same system of pipelines and a natural aquifer under the North Sea as used by BECCS facilities at Drax.

This way of clustering BECCS power and hydrogen production would also allow other industries such as manufactures, steel mills and refineries, to decarbonise.

Lowering the cost of flexible electricity

One of the challenges in transforming the energy system and wider economy to net zero is accounting for the cost of the transition.

The Energy Systems Catapult’s analysis found that it could be kept as low as 1-2% of GDP, while a report by the National Infrastructure Commission (NIC) projects that deploying BECCS would have little impact on the total cost of the power system if deployed for its negative emissions potential.

The NIC’s modelling found, when taking into consideration the costs and generation capacity of different sources, BECCS would likely be run as a baseload source of power in a net zero future. This would maximise its negative emissions potential.

This means BECCS units would run frequently and for long periods, uninterrupted by changes in the weather, rather than jumping into action to account for peaks in demand. This, coupled with its ability to abate emissions, means BECCS – alongside intermittent renewables such as wind and solar – could provide the UK with zero carbon electricity at a significantly lower cost than that of constructing a new fleet of nuclear power stations.

The report also goes on to say that a fleet of hydrogen-fuelled power stations could also be used to generate flexible back-up electricity, which therefore could be substantially cheaper than relying on a fleet of new baseload nuclear plants.

However, for this to work effectively, decisions need to be made sooner rather than later as to what approach the UK takes to shape the energy system before 2050.

The time to act is now

What is consistent across many different reports is that BECCS will be essential for any version of the future where the UK reaches net zero by 2050. But, it will not happen organically.

Sunset and evening clouds over the River Humber near Sunk Island, East Riding of Yorkshire

Sunset and evening clouds over the River Humber near Sunk Island, East Riding of Yorkshire

A joint Royal Society and Royal Academy of Engineering Greenhouse Gas Removal report, includes research into BECCS, DACCS and other forms of negative emissions in its list of key actions for the UK to reach net zero. It also calls for the UK to capitalise on its access to natural aquifers and former oil and gas wells for CO2 storage in locations such as the North Sea, as well as its engineering expertise, to establish the infrastructure needed for CO2 transport and storage.

However, this will require policies and funding structures that make it economical. A report by Vivid Economics for the Department for Business, Energy and Industrial Strategy (BEIS) highlights that – just as incentives have made wind and solar viable and integral parts of the UK’s energy mix – BECCS and other technologies, need the same clear, long-term strategy to enable companies to make secure investments and innovate.

However, for policies to make the impact needed to ramp BECCS up to the levels necessary to bring the UK to net zero, action is needed now. The report outlines policies that could be implemented immediately, such as contracts for difference, or negative emissions obligations for residual emitters. For BECCS deployment to expand significantly in the 2030s, a suitable policy framework will need to be put in place in the 2020s.

Beyond just decarbonising the UK, a report by the Intergovernmental Panel on Climate Change (IPCC) highlights that BECCS could be of even more importance globally. Differing scales of BECCS deployment are illustrated in its scenarios where global warming is kept to within 1.5oC levels of pre-industrial levels, as per the Paris Climate agreement.

BECCS has the potential to play a vital role in power generation, creating a hydrogen economy and offsetting other emissions. As it continues to progress, it is becoming increasingly effective and cost efficient, offering a key component of a net zero UK.

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

Breaking circuits to keep electricity safe

6 March 2020

Power generation
Electric relay with sparks jumping between the contacts doe to breaking a heavy inductive load.

Electricity networks around the world differ many ways, from the frequency they run at to the fuels they’re powered by, to the infrastructure they run on. But they all share at least one core component: circuits.

A circuit allows an electrical current to flow from one point to another, moving it around the grid to seamlessly power street lights, domestic devices and heavy industry. Without them electricity would have nowhere to flow and no means of reaching the things it needs to power.

But electricity can be volatile, and when something goes wrong it’s often on circuits that problems first manifest. That’s where circuit breakers come in. These devices can jump into action and break a circuit, cutting off electricity flow to the faulty circuit and preventing catastrophe in homes and at grid scale. “All this must be done in milliseconds,” says Drax Electrical Engineer Jamie Beardsall.

But to fully understand exactly how circuit breakers save the day, it’s important to understand how and why circuits works.

Circuits within circuits 

Circuits work thanks to the natural properties of electricity, which always wants to flow from a high voltage to a lower one. In the case of a battery or mains plug this means there are always two sides: a negative side with a voltage of zero and a positive side with a higher voltage.

In a simple circuit electricity flows in a current along a conductive path from the positive side, where there is a voltage, to the negative side, where there is a lower or no voltage. The amount of current flowing depends on both the voltage applied, and the size of the load within the circuit.

We’re able to make use of this flow of electricity by adding electrical devices – for example a lightbulb – to the circuit. When the electricity moves through the circuit it also passes through the device, in turn powering it. 

A row of switched on household electrical circuit breakers on a wall panel

A row of switched on household electrical circuit breakers on a wall panel

The national grid, your regional power distributor, our homes, businesses and more are all composed of multiple circuits that enable the flow of electricity. This means that if one circuit fails (for example if a tree branch falls on a transmission cable), only that circuit is affected, rather than the entire nation’s electricity connection. At a smaller scale, if one light bulb in a house blows it will only affect that circuit, not the entire building.

And while the cause of failures on circuits may vary from fallen tree branches, to serious wiring faults to too many high-voltage appliances plugged into a single circuit, causing currents to shoot up and overload circuits, the solution to preventing them is almost always the same. 

Fuses and circuit breakers

In homes, circuits are often protected from dangerously high currents by fuses, which in Great Britain are normally found in standard three-pin plugs and fuse boxes. In a three pin plug each fuse contains a small wire – or element.

One electrical fuse on electronic circuit background

An electrical fuse

When electricity passes through the circuit (and fuse), it heats up the wire. But if the current running through the circuit gets too high the wire overheats and disintegrates, breaking the circuit and preventing the wires and devices attached to it from being damaged. When a fuse like this breaks in a plug or a fuse box it must be replaced. A circuit breaker, however, can carry out this task again and again.

Instead of a piece of wire, circuit breakers use an electromagnetic switch. When the circuit breaker is on, the current flows through two points of contact. When the current is at a normal level the adjacent electromagnet is not strong enough to separate the contact points. However, if the current increases to a dangerous level the electromagnet is triggered to kick into action and pulls one contact point away, breaking the circuit and opening the circuit breaker.

Another approach to fuses is using a strip made of two different types of metals. As current increases and temperatures rise, one metal expands faster than the other, causing the strip to bend and break the circuit. Once the connection is broken the strip cools, allowing the circuit breaker to be reset.

This approach means the problem on the circuit can be identified and solved, for example by unplugging a high-voltage appliance from the circuit before flipping the switch back on and reconnecting the circuit.

Protecting generators at grid scale 

Power circuit breakers for a high-voltage network

Circuit breakers are important in residential circuits, but at grid level they become even more crucial in preventing wide-scale damage to the transmission system and electricity generators.

If part of a transmission circuit is damaged, for example by high winds blowing over a power line, the current flow within that circuit can be disrupted and can flow to earth rather than to its intended load or destination. This is what is known as a short circuit.

Much like in the home, a short circuit can result in dangerous increases in current with the potential to damage equipment in the circuit or nearby. Equipment used in transmission circuits can cost millions of pounds to replace, so it is important this current flow is stopped as quickly as possible.

“Circuit breakers are the light switches of the transmission system,” says Beardsall.

“They must operate within milliseconds of an abnormal condition being detected. However, In terms of similarities with the home, this is where it ends.”

Current levels in the home are small – usually below 13 amps (A or ampere) for an individual circuit, with the total current coming into a home rarely exceeding 80A.

In a transmission system, current levels are much higher. Beardsall explains: “A single transmission circuit can have current flows in excess of 2,000A and voltages up to 400,000 Volts. Because the current flowing through the transmission system is much greater than that around a home, breaking the circuit and stopping the current flow becomes much harder.”

A small air gap is enough to break a circuit at a domestic level, but at grid-scale voltage is so high it can arc over air gaps, creating a visible plasma bridge. To suppress this the contact points of the circuit breakers used in transmission systems are often contained in housings filled with insulating gases or within a vacuum, which are not conductive and help to break the circuit.

A 400kV circuit breaker on the Drax Power Station site

A 400kV circuit breaker on the Drax Power Station site

In addition, there will often be several contact points within a single circuit breaker to help break the high current and voltage levels. Older circuit breakers used oil or high-pressure air for breaking current, although these are now largely obsolete.

In a transmission system, circuit breakers will usually be triggered by relays – devices which measure the current flowing through the circuit and trigger a command to open the circuit breaker if the current exceeds a pre-determined value. “The whole process,” says Beardsall, “from the abnormal current being detected to the circuit breaker being opened can occur in under 100 milliseconds.”

Circuit breakers are not only used for emergencies though, they can also be activated to shut off parts of the grid or equipment for maintenance, or to direct power flows to different areas.

A single circuit breaker used within the home would typically be small enough to fit in your hand.  A single circuit breaker used within the transmission system may well be bigger than your home.

Circuit breakers are a key piece of equipment in use at Drax Power Station, just as they are within your home. Largely un-noticed, the largest power station in the UK has hundreds of circuit breakers installed all around the site.

A 3300 Volt circuit breaker at Drax Power Station

A 3300 Volt circuit breaker at Drax Power Station

“They provide protection for everything from individual circuits powering pumps, fans and fuel conveyors, right through to protecting the main 660 megawatt (MW) generators, allowing either individual items of plant to be disconnected or enabling full generating units to be disconnected from the National Grid,” explains Beardsall.

The circuit breakers used at Drax in North Yorkshire vary significantly. Operating at voltages from 415 Volts right up to 400,000 Volts, they vary in size from something like a washing machine to something taller than a double decker bus.

Although the size, capacity and scale of the circuit breakers varies dramatically, all perform the same function – allowing different parts of electrical circuits to be switched on and off and ensuring electrical system faults are isolated as quickly as possible to keep damage and danger to people to a minimum.

While the voltages and amount of current is much larger at a power station than in any home, the approach to quickly breaking a circuit remains the same. While circuits are integral parts of any power system, they would mean nothing without a failsafe way of breaking them.

Why spin a turbine without generating power?

12 February 2020

Power generation
Turbine at Cruachan Power Station

Massive spinning machinery is a big part of electricity generation whether it’s a wind turbine, hydro plant or biomass generator.

But big spinning turbines don’t just pump electricity out onto the grid. They also play a crucial role in keeping the electricity system stable, safe and efficient. This is because big, heavy spinning turbines add something else to the grid: inertia.

This is defined as an object’s resistance to change but in the context of electricity it helps the grid remain at the right frequency and voltage level. In short, they help the grid remain stable.

However, as electricity systems in Great Britain and other parts of the world move away from coal and gas to renewables, such as wind turbines, solar panels and interconnectors, the level of inertia on the system is falling.

“We need the inertia, we don’t need the megawatts,” explains Julian Leslie, Head of Networks at the National Grid Electricity System Operator (ESO). “But in today’s market we have to supply the megawatts and receive the inertia as a consequence.”

Turbine at Drax Power Station

Engineer inspecting turbine blades at Drax Power Station

The National Grid ESO is taking a new approach to this aspect of grid stability by using what are called synchronous condensers. These complicated-sounding pieces of machinery are actually quite straightforward in their concept: they provide inertia to the grid without generating unnecessary power.

These come in the form of:

  • Existing generators that remain connected to the grid but refrain from producing electricity.
  • Purpose built machines whose only function is to act as synchronous condensers, never generating real power. These may be fitted with flywheels to increase their mass and, in consequence, their inertia.

This means that spinning without generating is about to become a very important part of Great Britain’s electricity system.

Around and around

Electricity generators that spin at 3,000 rpm are described as synchronous generators because they are in sync with the grid’s frequency of 50Hz. These include coal, gas, hydro, biomass turbines and nuclear units. Most spin at 3000 rpm, some machines much less (e.g. 750 rpm). Thanks to the way they are designed, they are all synchronised together at the same, higher speed.

Then there are wind turbines where the generated power is not synchronised to the grid system. Termed asynchronous generators, these machines do not have readily accessible stored energy (inertia) and do not contribute to the stability of the system. Interconnectors and solar panels are also asynchronous.

It’s important that Great Britain’s whole grid is kept within 1% of the 50Hz frequency, otherwise the voltage of electricity starts to fluctuate, damaging equipment, becoming less efficient, even dangerous, or resulting in blackouts.

Say a power station or a wind farm were to drop offline, as occurred in August 2019, this would cause the amount of power on the grid to suddenly fall. But it is not just the power that changes – the frequency and voltage also fluctuate dramatically which can cause equipment damage and ultimately, towns, cities or widespread areas to lose power.

Running machines that have inertia act like the suspension on a car – they dampen those fluctuations, so they are not as drastic. The big spinning machines keep spinning, buying valuable milliseconds for the grid to react, often automatically, before the damage becomes widespread.

However, as a consequence of decarbonisation, more solar panels and wind turbines are now on the system and there are fewer spinning turbines, leading to lower levels of inertia on the grid.

“There are periods when renewable generation and flow from interconnectors are so great that it displaces all conventional, rotational power plants,” says Leslie. “Today, bringing more inertia onto the grid may mean switching off renewables or interconnectors, and then replacing them with rotating plants and the megawatts associated with that.”

Creating a market for inertia and synchronous condensers offers a new way forward – providing inertia without unneeded megawatts or emissions from fossil fuels.

A new spin on grid stability

At the start of 2020, The National Grid ESO began contracting parties, including Drax’s Cruachan pumped-hydro power station, to operate synchronous condensers and provide inertia to the grid when needed.

The plans mark a departure from the previous system where inertia and voltage control from electricity generators was taken for granted.

Cruachan Power Station is already capable of running its units in synchronous condenser mode (one of its units, opened up for maintenance, is pictured at the top of this article). This involves an alternator acting as a motor, offering inertia to the grid without generating unneeded electricity. Other service providers will repurpose existing turbines, construct new machines or develop new technologies that can electronically respond to the grid’s need for stability.

Synchronous condensers, or the idea of spinning a turbine freely without generating power, are not new concepts; power stations in the second half of the 20th century could shut down certain generating units but keep them spinning online for voltage control.

In the 1960s and 70s, some substations – where the voltage of electricity is stepped up and down from the transmission system – also deployed stand-alone synchronous condensers. These were also used to provided inertia as well as voltage control but are long since decommissioned.

Synchronous condenser installation at Templestowe substation, Melbourne Victoria, Australia. By Mriya via Wikimedia.

“Synchronous condensers are a proven technology that have been used in the past,” says Leslie. “And there are many new technologies we are now exploring that can deliver a similar service.”

Cheaper, cleaner, more stable

Commercial UK wind turbines

The National Grid ESO estimates the technology will save electricity consumers up to £128 million over the next six years. Savings, which come from negating the need for the grid to call upon fossil fuels for inertia as coal, oil and gas, become increasingly uneconomical across the globe as carbon taxes grow.

The fact that synchronous condensers do not produce electricity also saves money the grid may have had to pay out to renewable generators to stop them producing electricity or to storage systems to absorb excess power.

“It means the market can deliver the renewable flow without the grid having to pay to restrain it or to pay for gas to stabilise the system,” says Leslie. “Not only does this allow more renewable generation, but it also reduces the cost to the consumer.”

In a future energy system, where there is an abundance of renewable electricity generations, synchronous condensers will be crucial in keeping the grid stable. The National Grid ESO’s investment in the technology further highlights the importance of new ideas and innovation to balance the grid through this energy transition.

Synchronous generation provides benefits to system stability beyond the provision of inertia. In a subsequent article we’ll also explore how synchronous condensers can assist with voltage stability and help regional electricity networks and customers to remain connected to the national system during and after faults.

Read about the past, present and future of the country’s electricity system in Could Great Britain go off grid?