Author: Ben Graham

Where does global electricity go next?

12 December 2018

Power generation

Since the Paris Agreement came into effect in November 2016, it’s fair to say many countries have taken up the vital challenge of decarbonisation in earnest.

However, not all are making progress at the same rate. Many are not implementing the agreement at the pace needed to mitigate climate change, and keep the average global temperature increase well below 2oC of pre-industrial levels. Certainly not enough to limit the increase to 1.5oC by 2050, which the majority of climate scientists believe is necessary for the planet is to avoid dire consequences.

Last year even saw renewable energy investment fall 7%, while the money going into fossil fuels grew for the first time since 2014. And data released by the International Energy Agency (IEA) at the beginning of this month’s UN Climate Change Conference (COP24) in Katowice, Poland, found that 2017 was also the first for five years seeing an increase in advanced economies’ carbon emissions.

Despite this, there is much positive work towards decarbonisation.

A new report, Energy Revolution: A Global Outlook, by academics from Imperial College London and E4tech, commissioned by Drax, looks into the core areas and activities required to decarbonise the global energy system – and which countries are performing them to good effect. In doing this, the report also looks at how the UK stands in comparison and what steps countries need to take to truly decarbonise.

Here are the key indicators of decarbonisation and how countries around the world are performing towards them.

Dam in Hardangervidda, Norway

Clean power

At the forefront of reducing emissions and curbing climate change is the need to decarbonise electricity generation and move towards renewable sources.

Last year the global average carbon intensity was 440 grams of carbon dioxide (CO2) per kilowatt-hour (g/kWh). Out of the 25 major countries the report tracks, 16 came in below average, with seven of these falling under the long-term 50 g/kWh goal.

Leading the rankings are Norway, France and New Zealand, which have a near-zero carbon intensity for electricity generation, thanks to extensive hydro and nuclear power capacity.

At the other end of the table, China, India, Poland and South Africa remain wedded to coal, producing up to twice the global average CO2 for electricity generation. This comes despite China having installed two and a half times more renewables than any other country – it now boasts 600 gigawatts (GW) of renewable capacity.

Per person, Germany is leading the renewablesdrive with almost 1 kW of wind and solar capacity installed per person over the last decade. Despite this, as much as 40% of its electricity still comes from coal.

Part of the challenge in moving away from coal to renewables is economic, as many countries continue to subsidise their coal industries to keep electricity affordable. Phasing out these subsidies is therefore key to switching to a low-carbon generation system. Doing this works, as demonstrated by the example of Denmark, which cut its fossil fuel subsidies by 90% over the past decade, in turn successfully cutting its coal generation by 25%.

The UK’s carbon pricing strategy, which adds £16 per tonne of CO2emitted on top of the price set by the European emissions trading system (EU ETS), has led the carbon intensity of Great Britain’s electricity to more than halve in a decade. It highlights how quickly and effectively these kinds of fees can make fossil fuels uneconomical. Since 2008 the UK has removed more than 250 g/kWh from its electricity production.

Carbon capture and storage

In many future looking climate scenarios, keeping the earth’s temperature below a 2oC increase depends on extensive deployment of carbon capture technology – capturing as much as 100 billion tonnes of CO2 per year. Storing and using carbon is clearly forecast to be a major part of any attempt to meet the Paris Agreement, but at present there are few facilities carrying it out at scale.

Around the world today there are 18 large-scale carbon capture and storage (CCS) units running across six countries with a total capacity to capture 32 million tonnes of CO2 per year (MtCO2p.a). Another five facilities are under construction in three countries to add another 7 MtCO2p.a of global capacity. In the UK, Drax Power Station is piloting a bioenergy carbon capture and storage programme that could make it the world’s first negative emissions power station.

The USA has the greatest total installed capacity at 20 MtCO2p.a., but per person it ranks behind Norway, Canada and Australia. Their smaller populations give them more than 200 kg of carbon capture capacity per person per year.

Oil platform off the coast of Australia

These figures are well below the 100 billion tonnes the IEA estimates need to be stored by 2060 to prevent temperatures reaching 2oC more. However, considering the US alone has a potential storage capacity of more than 10 trillion tonnes of CO2, the potential of storage is not expected to be a problem.

Using depleted oil or natural gas fields as storage for captured carbon is being explored in a number of regions, with the US establishing several projects with more than 1 million tonnes in capacity. In 2019, Australia will open the world’s largest CO2store with the capacity to capture between 3.4 million and 4 million tonnes a year from Chevron’s Gorgon gas facility.

Considering the storage capacity available globally, it’s a matter of deploying the necessary technology for CCS to have a significant impact on emissions and global warming. The UK is perhaps a typical example of where CCS is at present with estimated storage capacity of 70 billion tonnes, as much as half of the entire EU combined. By repurposing North Sea oil and gas fields in partnership with Norway, the UK could pool its carbon storage capacity.

Electrification

Electricity generation is one of the main targets for emissions reductions globally. As a result of the progress that’s been made in this field, many future-looking scenarios highlight the important of electrification in other sectors, such as transport, in turn making them less carbon intensive.

Transport is leading the charge globally – there are now 10 different countries where one of every 50 new vehicles sold is electric. In Norway, this ratio is almost one in two, thanks in part to generous tax exemptions as well as non-financial incentives like access to bus lanes and half-price ferries.

Perhaps surprisingly, China is the world’s largest electric vehicle (EV) market. It may still use significant amounts of coal, but its commitment to reducing urban air pollution has seen it push EVs heavily, and it now accounts for 50% of the global battery EV market on its own.

Chinese electric car charging stations

Of course, adoption of EVs requires the supporting infrastructure to be truly successful. In conjunction with its high sales, Norway leads the way in charging points per capita, with one for every 500 people. This compares to one charger for every 5,000 people in the UK and one for every 10,000 people in China.

Electrification also affects the energy intensity of country’s transport systems and while it may be the largest EV market, China’s rise in private vehicles has been largely driven by petrol and diesel models. The result is the largest increases in transport energy intensity and emissions has taken place in China, Indonesia and India, respectively.

Domestic energy intensity is also rising in China, Indonesia and South Africa, as greater numbers of people gain access to appliances and home comforts. Conversely in Europe, Portugal, Germany and the Netherlands have all seen their domestic energy intensity drop in the last decade. However, this may be the lingering effect of the 2008 recession rather than long-term efficiency improvements.

The efficiency of industrial processes is also an important barometer in decarbonisation. Activities like mining and manufacturing require heavy-duty diesel-powered machinery and often coal-powered generators, especially in BRIC nations. The exception is China, where plans to get the 1,000 most energy-intensive companies to reduce their energy consumption per unit of GDP produced by 20% over the last five years, has proved fruitful.

Norway’s heavily-electrified industries, however, are still energy intensive and its level of carbon intensity is vulnerable to fluctuations in power generation prices.

Electrification and reduced emissions require government policies to put in motion behavioural changes that can lead to lasting decarbonisation. “Robust carbon pricing is one of the most effective tools to enabling a zero carbon, lower cost energy future,” Drax Group CEO Will Gardiner commented recently.

Welcoming a November report by the Energy Transitions Commission, Gardiner said:

“The cost of inaction far outweighs the cost of doing something now.”

Explore the full report: Energy Revolution: A Global Outlook.

I. Staffell, M. Jansen, A. Chase, E. Cotton and C. Lewis (2018). Energy Revolution: Global Outlook. Drax: Selby.

Drax commissioned independent researchers from Imperial College London and E4tech to write Energy Revolution: A Global Outlook, which looks into the core areas and activities required to achieve decarbonisation – and which countries are performing them to good effect. In doing this it also looks at how the UK stands in comparison and what steps countries need to take to truly decarbonise.

The inside of a cooling tower looks like no place on earth

29 November 2018

Power generation

The silhouette of cooling towers on the horizon is one of the most recognisable symbols of electricity generation around the world. But inside these massive structures is an environment unlike any other.

When cooling towers are in operation, torrents of warm water cascade down to a huge pond at its base, the air cooling it as it falls. Plumes of water vapour rise through the structure and into the air.

But when shut down – for maintenance, for example – the inside of a cooling tower is a very different place. The vast emptiness of the space can be eerily silent. Even the smallest noise echoes around its concrete shell.

Standing at over 114 metres high, each of Drax’s 12 cooling towers are 86 metres in diameter at their base, 53 metres at their summit, and could comfortably fit the Statue of Liberty inside. Everything about them is huge, but they are not the unsophisticated masses of concrete they appear from afar.

“Look at a cooling tower and you might think it’s a substantial, thick structure. It’s not,” explains Nick Smith, a civil engineer at Drax. “It’s basically like an egg shell. It is the shape that gives it its strength.” For the majority of their height, a typical cooling tower is between just 178 and 180 mm – or 7 inches – thick.

It’s a testament to the original design and construction that they require such limited maintenance more than half a century after plans were first drawn up. Especially considering they are in daily use.

What does a cooling tower do?

Water is an essential part of thermal electricity generation. It is turned into high-pressure steam in the extreme temperatures of a boiler before being used to spin turbines and generate electricity. Water within the boiler is ‘de-mineralised’ and purified to prevent damage to the turbine blades and infrastructure.

Once it leaves the turbine, the steam is cooled to pure water again in the condenser so it can be reused in the boiler. To do this the steam is passed over pipes containing cold water from the cooling towers, which cools and condenses the steam while also heating up the cold water to roughly 40 degrees Celsius, the temperature it is at when it enters the cooling tower.

Inside the towers the warm water is poured over what’s known as the cooling tower pack, a series of stacks of corrugated plastic that sit roughly 30 metres up the tower. The heat and the tower’s height create a natural draught. This pulls air in from the cavities at the base of the tower – called the throat – which cools the water to around 20°C as it cascades down the stack into a pond below. It is then returned to the condenser where the cooling cycle starts all over again.

Only around 2% of the water escapes through the top of the cooling towers as water vapour – which is what can be seen exiting the top of the towers – with a further 1% returned to the River Ouse to control water levels. These small losses are replenished with water taken from the Ouse. It highlights the genius of the towers’ design that their shape alone can cool water so efficiently on an industrial scale with minimal environmental impact. 

A lasting design

A cooling tower’s iconic shape is known as a hyperboloid, referring to its inward curve. This makes them very stable, but to make them strong enough to last as long as they have, Drax’s cooling towers have the added assistance of reinforced concrete.

“Concrete is very strong in compression, but it has hardly any tensile strength,” says Smith. “Therefore our cooling towers have both vertical and horizontal hoop reinforcement to take any tensile forces generated. It is the concrete and steel working together that gives the reinforced concrete its strength.”

The level of design and engineering of Drax’s cooling towers are all the more impressive considering their age. “The construction of our first tower was completed in 1970 and designed in the mid 1960s,” says Smith, pointing out, “they were designed at a time where there wasn’t huge computing processing power, so they would likely have been designed by hand.”

“They were constructed to a very high degree of accuracy even when a lot of the equipment used would have been manual,” he adds.

Designing and building a cooling tower today, he adds, would require significant computing power and sophisticated setting-out equipment to ensure the accuracy of the construction. However, the underlying principles of the towers’ shape and how well they have continued to perform since their construction would give little reason to deviate from the current design.

In fact, that consistent performance means that even as the nature of generating electricity develops to include new fuels and technologies, cooling towers remain an integral part of the process. Drax’s Repower project– which could see the conversion of the plant’s remaining coal units to gas and the installation of a giant battery facility – is a significant step forward in the evolution of power generation, yet the design and purpose of the cooling towers would remain the same.

The structures that will shape the landscape of the future of electricity generation may include wind turbines, biomass domes and solar panels. But the enduring functionality of natural draught concrete cooling towers means they will still play a role in producing the country’s electricity – even as generation diversifies.

Watch Inside a cooling tower

The great balancing act: what it takes to keep the power grid stable

8 June 2018

Power generation

What does it mean to say Great Britain’s electricity network needs to be balanced? It doesn’t refer to the structural stability of pylons. Rather, balancing the power system is about ensuring electricity supply meets demand second by second.

From the side of a consumer, the power system serves one purpose: to deliver electricity to homes and businesses so that it powers our lives. But from a generator and a system operator perspective, there is much more at play.

Electricity must be transported the length of the country, levels of generation must be managed so they are exactly equal to levels being used, and properties like voltage and frequency must be minutely regulated across the whole network to ensure power generated at scale in industrial power stations can be used by domestic appliances plugged into wall sockets.

Ensuring all this happens smoothly relies on the system operator – National Grid – working with power generators to provide ‘ancillary services’ – a set of processes that keep the power system in operation, stable and balanced.

Here we look at some of the most important ancillary services at play in Great Britain.

Frequency response

One of the foundations of Great Britain’s power system stability is frequency. The entire power network operates at a frequency of 50 Hz, which is determined by the number of directional changes alternating current (AC) electricity makes every second. However, just a 1% deviation from this begins to damage equipment and infrastructure, so it is imperative it remains consistent.

This is done by National Grid instructing flexible generators (such as thermal, steam-powered turbines like those at Drax Power Station or our planned battery facility) to either increase or decrease generation so electricity supply is matched exactly to demand. If this is unbalanced it affects the network’s frequency and lead to instability and equipment damage. Generators are set up to respond automatically to these request, correcting frequency deviations in seconds.

UK power gridReactive power and voltage management

The electricity that turns on light bulbs and charges phones is what’s known as ‘active power’. However, getting that active power around the transmission system efficiently, economically and safely requires something called ‘reactive power’.

Reactive power is generated the same way as active power and assists with “pushing” the real power around the system but unlike active power it’s does not travel very far. The influence of Reactive power is local and the balance in any particular area is very important to maintain power flows and a stable system.

This means National Grid must work with generators to either generate more reactive power when there is not enough, or absorb it when there is an excess, which can happen when lines are ‘lightly loaded’ (meaning they have a low level of power running through them).

Drax’s ability to absorb reactive power is also vital in controlling the grid’s voltage. Great Britain’s system runs at a voltage of 400 kilovolts (kV) and 275 kV (Scotland also uses 132kV), before it is stepped down by transformers to 230 volts for homes or 11 kV for heavy industrial users. Voltage must stay within 5% of 400 kV before it begins to damage equipment.

By producing reactive power a generator increases the voltage on a system, but by switching to absorbing reactive power it can help lower the voltage, keeping the grid’s electricity safe and efficient.  

System inertia

As well as being able to automatically adjust to keep the country on the right frequency, Drax’s massive turbines, spinning at 3,000 rpm, also have the advantage of adding inertia to the grid.

Inertia is an object’s natural tendency to keep doing what it is currently doing.

This system inertia of the spinning plant is effectively ‘stored’ energy. This can be used to act as a damper on the whole system to slow down and smooth out sudden changes in system frequency across the network – much like a car’s suspension it helps maintain stability.

Reserve power 

Humans are creatures of habit. This means the whole country tends to load dishwashers, turn on TVs and boil kettles at roughly the same time each day, making the rise and fall in electricity demand easy enough for National Grid to predict.

However, if something unexpected happens – a sudden cold snap or a power station breaking down – the grid must be ready. For this, National Grid keeps reserve power on the system to jump into action and fill any sudden gaps in demand and fluctuations in voltage and frequency it could cause.

Ancillary services in an evolving system

As with how electricity is generated across the country, balancing services are undergoing major change. As more intermittent renewables, such as wind and solar, come onto the system to provide low carbon power necessary for Great Britain to decarbonise, that same system becomes more volatile and more difficult to balance.

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More than that, the ancillary services needed to stabilise a more volatile grid can’t be generated by every generation source. Many depend on a turbine rotating at 3,000 rpm, generating electricity at a steady frequency of 50Hz, as is found in thermal generators such as Drax. Intermittent, also known as variable sources of power, are weather dependent. They are often unable to provide the same services as biomass and gas power stations.

While attempts to supply some of these ancillary services by co-locating wind or solar facilities with giant batteries are underway, thermal power stations that can quickly and reliably  balance the system at scale still play an essential role in making the transmission network safe, efficient, economic and stable.

This story is part of a series on the lesser-known electricity markets within the areas of balancing services, system support services and ancillary services. Read more about system inertia, frequency response, reactive power and reserve power.  Find out what lies ahead by reading Balancing for the renewable future and Maintaining electricity grid stability during rapid decarbonisation.

The power system’s super subs

5 February 2018

Power generation

Every day we flick on lights, load dishwashers and boil kettles but few of us pause and think of the stress this can cause for the electricity system. We certainly don’t call National Grid in advance to let them know when we plan to do laundry.

But when any number of the 25.8 million households in Great Britain turn on a washing machine, the grid needs to be ready for it. Fortunately, these spikes in demand are often predictable.

“We are creatures of habit,” says Ian Foy, Drax Head of Ancillary Services.

“We all tend to come home from work at the same time and turn on similar appliances, and this keeps the shape of daily electricity demand much the same.”

National Grid, the operator of Great Britain’s high voltage power transmission system, uses this consistent demand to plan when and how much electricity will be needed for the coming days, and agrees contracts with generators to meet it.

However, there are times when the unexpected can happen – an unseasonable cold spell or a power station breakdown – causing sudden imbalances in supply and demand. To plan for this, the grid carries ‘reserve power’, which is used to fill these short-term gaps.

Delivering this doesn’t just mean keeping additional power stations running to deliver last minute electricity. Instead, it involves a range of services coming from different types of providers, technologies and timescales.

In Great Britain, there are four primary ways this is delivered.

  1. Frequency response

The fastest form of reserve is frequency response. It is an automatic change in either electricity generation or demand in response to the system frequency deviating from the target 50Hz.

Generation and demand must be kept balanced within tight limits, second by second. Failure to do so could lead to the whole system becoming unstable, leading to the risk of blackouts. This is why, every second of the day, National Grid has power generators operating in Frequency Response mode. These power stations effectively connect their steam governor or fuel valves to a frequency signal. If frequency falls, generation increases. If frequency rises, generation is reduced.

An issue which has arisen over the past few years is a reduction in system inertia. The inertial forces in a spinning generator help slow the rate of frequency change, acting like dampers on car suspension. Some small power generation technologies, along with some demand, are sensitive to the rate of change of frequency – too high a rate can cause it to disconnect from the system and this unplanned activity can lead to system instability.

Some forms of generation such as wind and solar along with high voltage, direct current (HVDC) interconnectors between Great Britain and the rest of Europe do not provide inertia. As these electricity sources grow on the system, the system operator must find ways to accommodate them. Reducing the size of the largest credible loss, e.g. reducing interconnector load, buying faster frequency response or running conventional generation out of merit are the usual approaches.

  1. Spinning reserve

The next quickest and most common reserve source, spinning reserve, can jump into action and start delivering electricity in just two minutes. This reserve, both positive and negative, is carried on multiple generating units often running at a part load position (for example, if Drax’s biomass Unit 3 is running at 350 MW of a possible 645 MW). Typical delivery rates are 10 to 20 MW per minute.

This type of reserve responds to unexpected short-term changes in power demand or changes in power generation either in size or timing. For example, during a major TV event or if a generator changes output unexpectedly.

During television ad breaks, the millions of people watching may switch on kettles or flick on lights, sending demand soaring. If a programme or sporting event does not end at the scheduled time, National Grid has to quickly change the generation schedule by sending an electronic dispatch to a generator who responds by quickly ramping up or down.

Thermal power stations such as Drax along with hydro and pumped storage, which can increase or decrease output on demand, are the most common providers of this form of reserve, but  newer technologies such as batteries will also be able to offer the speed required.

  1. Short term operating reserve (STOR)

A slightly slower cousin to spinning reserve, STOR is contracted months in advance by National Grid. It is designed to be available within 20 minutes’ notice.

Around 2 gigawatts (GW) of capacity can provide reserves against exceptionally large losses or demand spikes. STOR capacity tends to be plant which cannot make a living in the energy market because it has a high marginal cost. Traditionally STOR has been supplied by low efficiency aeroderivative turbines or diesel engines but a wider variety of technologies from batteries to demand reduction are increasingly being contracted.

  1. Demand turn up

Managing reserve power isn’t just about finding extra generation to meet demand. Sometimes it’s about quickly addressing too much generation.

High levels of generation coming onto the grid without an equally high demand can overload power lines and networks, causing instability and frequency imbalances, which can lead to blackouts. This might happen in the summer months, when the weather allows for lots of intermittent renewable generation (such as wind and solar), but low levels of demand due to factors like warmer weather and longer daylight hours.

To restore balance, the grid is beginning to ask intensive commercial or industrial electricity users to increase consumption or turn off any of their own generation in favour of grid-provided power. In the case of generating units at Drax Power Station, the response starts less than a second from the initial frequency deviation to help slow the rate of frequency change and minimises large frequency swings.

Reserve in a changing energy system

Planning for the unexpected has long been a staple of the electricity system, but as the shape of that system changes, reserve and response delivery is having to change too.

“Carrying reserve is easier on conventional plants because you know what the plant is capable of generating,” says Foy.

“Wind and solar are subject to the weather, which changes over time. The certainty you get with conventional generation you don’t necessarily get with the intermittency of weather-dependant renewables.”

Add to that the way we use electricity, everything from high efficiency lighting, electric vehicles through to smart appliances and we can see the challenges will grow.

As more variable renewables hits the system, storage technologies will become more important in providing a fast-acting source of short term reserve and response. Smart appliance technology too will play a bigger role in spreading demand across the day and reducing the size of demand peaks and troughs which require rapid changes in generation.

Industry has a role to play too. Some of the biggest users of electricity are expected to play an increasingly important role in support of the system operator. National Grid told members of Parliament in 2016, that ‘it is our ambition to have 30-50% of our balancing capacity supplied by demand side measures by 2020.’

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

Until these technologies and market mechanisms are widespread and implemented at scale across the grid, however, it will fall to thermal power stations such as biomass, gas turbines such as the planned Progress Power in Suffolk and, on occasion, coal to ensure there is the required reserve power available.

This short story is adapted from a 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, and reactive 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 and Maintaining electricity grid stability during rapid decarbonisation.

How electricity is made

25 January 2018

Power generation

Every morning we take electricity as a given. We switch on lights, charge phones and boil kettles without thinking about where this power comes from.

The electronic devices and appliances that make up our daily routines are not particularly energy intensive. Boiling a kettle only uses 93 watts, toasting for three minutes only requires 60 watts, while cooking in a microwave for five minutes takes 100 watts.

However, when people are waking up and making breakfast in almost 30 million households around the UK, those small amounts soon create a significant demand for electricity. On a typical winter’s morning, this combined demand spikes to more than 45 gigawatts (GW).

So this is what it takes to power your breakfast – from the everyday toaster in your kitchen backwards through thousands of miles of cables to the hundreds of thousands of tonnes of machinery in wind farms, hydro-electric dams and at power stations such as Drax where electricity generation begins.

The grid 

The journey starts in the home where all our electricity usage is tracked by meters. These are becoming increasingly ‘smart’, displaying near real-time information on energy consumption in financial terms and allowing more accurate billing. There are already 7.7 million smart meters installed around the UK, but that number is set to triple this year, paving the way for a smarter grid overall.

What brings electricity into homes is perhaps the most visible part of the energy system on the UK’s landscape. The transmission system is made up of almost 4,500 miles of overhead electricity lines, nearly 90,000 pylons and 342 substations, all bringing electricity from power stations into our homes.

Making sure all this happens safely and as efficiently as possible falls to the UK’s nine regional electricity networks and National Grid. Regional networks ensure all the equipment is in place and properly maintained to bring electricity safely across the country, while National Grid is tasked with making sure demand for electricity is met and that the entire grid remains balanced.

The station cools down

One of the most distinctive symbols of power generation, cooling towers carry out an important task on a massive scale.

Water plays a crucial role in electricity generation, but before it can be safely returned to the environment it must be cooled. Water enters cooling towers at around 40 degrees Celsius, and is cooled by air naturally pulled into the structure by its unique shape.

This means those plumes exiting from the top of the towers are, rather than any form of pollution, only water vapour. And this accounts for just 2% of the water pumped into the towers.

Drax counts 12 cooling towers, each 114 metres tall – enough to hold the Statue of Liberty with room to spare. Once the water is cooled it is safe to re-enter the nearby River Ouse.

The station’s bird’s-eye view

The control room is the nerve centre of Drax Power Station. From here technicians have a view into every stage of the power generation process.  The entire system controls roughly 100,000 signals from across the power station’s six generating units, water cooling, air compressors and more.

While once this area was made up of analogue dials and controls, it has recently been updated and modernised to include digital interfaces, display screens and workstations specially designed by Drax to enable operators to monitor and adjust activity around the plant.

The heart of power generation 

At the epicentre of electricity generation is Drax’s six turbines. These heavy-duty pieces of equipment do the major work involved in generating electricity.

High-pressure steam drive the blades which rotates the turbine at 3,000 revolutions per minute (rpm). This in turn spins the generator where energy is converted into the electricity that will eventually make it into our homes.

These are rugged pieces of kit operating in extreme conditions of 165 bar of pressure and temperatures of 565 degrees Celsius. Each of the six turbine shaft lines weighs 300 tonnes and is capable of exporting over 600 megawatts (MW) into the grid.

One of the most important parts of the entire process, turbines are carefully maintained to ensure maximum efficiency. Even a slight percentage increase in performance can translate into millions of pounds in savings.

Turning fuel to fire

To create the steam needed to spin turbines at 3,000 rpm, Drax needs to heat up vast amounts of water quickly and this takes a lot of heat.

The power station’s furnaces swirl with clouds of the burning fuel to heat the boiler. Biomass is injected into the furnace in the form of a finely ground powder. This gives the solid fuel the properties of a gas, enabling it to ignite quickly. Additional air is pumped into the boiler to drive further combustion and optimise the fuel’s performance.

Pulveriser

How do you turn hundreds of tonnes of biomass pellets into a powder every day? That’s the task the pulveriser take on. In each of the power plant’s 60 mills, 10 steel and nickel balls, each weighing 1.2 tonnes, operate in extreme conditions to crush, crunch and pulverise fuel.

These metal balls rotate 37 times a minute at roughly 3 mph, exerting 80 tonnes of pressure, crushing all fuel in their path. Air is then blasted in at 190 degrees Celsius to dry the crushed fuel and blow it into the boiler at a rate of 40 tonnes per hour.

The journey begins: biomass arrives

Biomass arrives at Drax by the train-load. Roughly 14 arrive every day at the power station, delivering up to 20,000 tonnes ready to be used as fuel.

These trains arrive from ports in Liverpool, Tyne, Immingham and Hull and are specially designed to maximise the efficiency of the entire delivery process, allowing a full train to unload in 40 minutes without stopping.

The biomass is then taken to be stored inside Drax’s four huge storage domes. Each capable of fitting the Albert Hall inside, the domes can hold 300,000 tonnes of compressed wood pellets between them.

Here the biomass waits until it’s needed, at which point it makes its way along a conveyor belt to the pulveriser and the process of generating the electricity that powers your breakfast begins.

Refurbishing a 300-tonne generator core within the heart of a power station

6 December 2017

Power generation
Electricity generator

At the centre of Drax Power Station, in a corner of the cavernous turbine hall, is a white box. The inside of this box is spotlessly clean. Not only are its white walls free of dirt, they are free of even dust. But there is one outlier inside this sterile environment: a 300-tonne chunk of industrial equipment.

This equipment is a generator core – the central component for converting the mechanical energy to electrical power.

Electricity generator core

The core is driven by the steam turbine. Ninety tonnes of generator rotor spinning at 3,000 rpm with just millimetres of clearance from the core produce 660 megawatts (MW) of electricity. That’s enough – 645 MW when exported from Drax into the National Grid – to power a city the size of Sheffield.

The generator is a serious piece of industrial machinery. And despite the pristine conditions, this white box is the site of serious engineering.

A process normally done by large-scale manufacturers in dedicated factories, ‘rewinding’ a generator core – as the process is called – is a major operation.

No other UK facility is capable of doing this complex job. So it’s here, in a white box, in the middle of an operational power station in North Yorkshire, that a team of engineers is undertaking work that will secure the generator’s use for decades. This is the Drax rewinding facility.

Turbine structure

How a generator works

A generator consists of two main components, a spinning rotor and a stationary stator. The rotor, which is directly connected to the main turbine and spins 50 times every second, sits inside the stator. Both the stator and the rotor contain a large number of copper coils known as windings. These windings are what carry the electrical current.

The rotor acts like a very strong electromagnet, which, when a voltage is applied, produces a strong magnetic field. Because the rotor sits inside the stator, this magnetic field intersects the copper windings of the stator and induces a voltage in these windings, allowing current to flow.  This voltage is then brought out of the stator and passed through a step-up transformer, where it is increased to a level suitable for transmission through the National Grid.

The stator core is made from many elements with hundreds of thousands of laminations, 84 water-cooled insulated copper bars, each 11 metres long and weighing 200kg forming the windings, various insulating materials, blocks, packing, wedges and condition monitoring equipment.

Generator stators can operate for decades without fault.

DIY at Drax

In 2016, a team of engineers at Drax embarked on a project to construct a facility to rewind the stator on site. This required cross-company collaborative working to design and construct this huge purpose built facility.

Contamination can cause operational problems, so the team built a sterile, white room within the turbine hall – one of just two places within the power station with foundations strong enough to support the incredible 450 tonnes required for the rewind facility. Designed to hold the stator core and the conductor bars, air is forced out of the room to limit the possibility of contamination to the core during the rewind.

“When the unit is in service it becomes magnetic, so any metallic particles left in the space will be attracted to the core,” explains Drax electrical engineer Thomas Walker. “Once magnetised, any metal particles could be drawn in, burrowing into the insulation and core lamination.”

This is the kind of event that an electricity generator wants to avoid – but when it happens, be prepared to fix it.

Roll with it

When Drax’s stators were manufactured in the 1980s, completing their construction relied on manual handling techniques. Modern day facilities, however, rotate the core to minimise human contact.

It took just six months for a partnership involving Drax, Siemens and ENSER to manufacture what could be the largest stator rollers in the world and within that time, ship them from the US to North Yorkshire.

With the rollers installed, the next step was to move in the core. Two of the turbine hall’s cranes, each capable of lifting 150 tonnes, were combined to lift it, hoisting the core onto the mechanical ‘roller’ within the rewind facility.

Once in place, the roller rotates the core, allowing for the copper conductor bars to be safely removed and inserted. Despite this mechanical help, the removing and replacing of each one is still at its heart a human job.

“We still need 10 men to physically move the conductor bars with lifting aids, which makes it not an easy process,” says Walker. Using this method, the bars weighing 200kg each can be safely and precisely fitted into the core.

Electricity turbine generator at Drax

Opting for in-house

Rewinding a stator is a complex process. However, when the time, logistics and costs of shipping the core to Siemens – the German-based manufacturers – was factored in, the decision to do the work at Drax Power Station was an easy one.

“A 300-tonne core is not easy to transport and the Highways Agency do not like things like that on the roads. They’d want us to use waterways” says Drax lead engineer Mark Rowbottom. “Logistically it just wasn’t worth it. It’s too much money to move and ship that weight to Germany. So, we looked at what we could do onsite.”

More than just an economical and logistical decision and with the UK’s diminishing manufacturing facilities, Drax is now equipped to support generator rewinds for many years to come. Building and operating the rewind facility was a project that leveraged the engineering abilities of Drax employees. They are increasingly doing engineering traditionally outsourced to equipment manufacturers.

“The experience we have gained and the close working relationship we have established with Siemens enables us to support the generator for the remaining life of the station,” says Rowbottom.

“To see the core in that many pieces and stripped down to this level is very rare,” says Walker, who began working at the plant as an apprentice. Of the 84 conductor bars, half have been fitted, and the team is scheduled to complete the stator rewind in early 2018. “I never thought I’d do anything like this but am proud to say that I’ve done it.”

How Drax is boosting jobs and the economy throughout the UK

17 October 2017

Sustainable business

Whether powering homes across Britain or helping stabilise the national grid, Drax Power Station’s impact to our electricity network is far reaching. But it doesn’t stop at generating and supplying power.

A new report by Oxford Economics, commissioned by Drax, has found that in addition to its important role powering Britain, Drax Group also provides an economic boost to areas across the country.

Here are three ways Drax Group contributed to the UK economy in 2016. 

£1.67 billion added to UK GDP

Drax Group contributed an estimated £1.67 billion to UK gross domestic product (GDP) in 2016, an increase from £1.24 billion in 2015. Of that figure, £301 million was added directly – as a result of the group’s own activities such as the generating and selling of power.

And while this is an impressive 6.1% increase on 2015, the numbers are even more significant when looking at the benefit beyond the group’s core activities.

In 2016, Drax Group’s spending with external suppliers such as rail freight wagon manufacturer WH Davis and IMServ, which supplies Automated Meter Reading technology to Opus Energy, reached £872 million. A further £36m was spent by these suppliers across their own supply chain to help them provide their services to Drax.

There is an even greater impact when considering how this money filters through employees and suppliers into local retail, leisure and service economies. Something which is especially important when the number of jobs Drax supports is taken into account.

18,500 jobs supported across the country

Drax Group directly employed more than 2,000 people in 2016, but across the country it supports far more – 18,500, a significant increase from the 14,150 of 2015.

These jobs are primarily in high-skilled manufacturing, engineering, construction, IT, professional business services and transport. While 3,650 of these were in Drax Power Station’s native Yorkshire and Humber area, this year saw the group’s overall impact extend much further. 

Opus Energy employees holding meeting in Northampton, 2019

 An impact beyond the ‘Northern Powerhouse’

Roughly a quarter (£419 million) of Drax’s total contribution to UK GDP was generated in the Yorkshire and the Humber region. When the North West and North East were included, the company impacted the northern economy to the tune of £577m and supported over 6,000 jobs.

Yorkshire and the Humber was closely followed by the East of England, the home of Haven Power, which saw the second highest impact – registering more than £200 million contributed in GVA – and London and the East Midlands.

This is thanks in part to the growing activities of Drax Group companies. Both Haven Power and Opus Energy (which became a part of Drax Group in February 2017), are helping the UK move towards a low carbon future by supplying an increasing amount of British companies with renewable power. With offices in Ipswich, Oxford, Northampton and Cardiff, Haven Power and Opus Energy highlight how Drax Group businesses are direct drivers for local GDP and employment. Opus Energy supported 1,600 jobs and £130 million in GVA in Wales, while Haven Power contributed £232 million to the East of England.

These numbers are noteworthy, but what makes them all the more significant is how this translates into tax revenue. Operations at Drax Group generated an estimated £327 million for the UK’s public purse – equivalent to the salaries of almost 14,000 nurses or 11,900 teachers.

As the group continues to grow – adding new power generation assets to the national electricity transmission system and helping more businesses use renewable power – Drax can increase its positive impact on the UK’s economy and help to make the country’s low-carbon future a reality more quickly.

To find out more about how Drax has benefited the UK’s economy, visit draximpact.co.uk. The full 2016 report can be downloaded here. Interested in a career at Drax Group? Please visit Careers to find out more.

How a small Yorkshire village became home to Britain’s air power innovation

12 October 2017

Power generation

Picture an airship. Massive and slow moving, it makes its way across skies. It’s a far cry from what we’ve come to expect from the speed and innovation of today’s air transport.

But go back a century and airships were not only the height of technology, they were also a key part of Britain’s aerial war effort.

Part of this innovation can be traced back to the Yorkshire village of Barlow, which was the site of a factory that built the vessels during the First World War. Three riged-structure airships where constructed and took flight during the factory’s history and this October marks the centenary of the first airship flight at the site in 1917.

This is the story of how a stretch of land by the small Yorkshire village near Selby became the frontline for innovation in British military aviation.

The Admiralty marches in

During the First World War, the German zeppelin fleet posed a very real threat to the people of Britain. More reliable than the aeroplanes of the time, hydrogen-filled airships’ ability to hold heavy loads and remain airborne for periods of 20-plus hours allowed them to carry out strategic bombing campaigns.

While the actual effectiveness of these raids on the UK mainland remains questionable, the psychological impact of the zeppelins’ abilities to attack UK cities pushed the military to respond. In early 1916, at the request of the Admiralty, the Armstrong-Whitworth Airship Department was formed to build zeppelin-style aircraft.

To set about constructing the airship, Armstrong-Whitworth acquired a large area of ground in Barlow village. Within six months of the initial Admiralty instructions, the airship shed was completed. It was the start of a century of industrial innovation in the area.

Changing the area

Up until the beginning of the 20th century, Barlow was almost exclusively agricultural, but the construction of the Selby-Goole railway line changed that. It suddenly connected the area as never before and enabled Armstrong-Whitworth to establish the 880-acre airship facility.

Along with a 700-foot shed, the site also included workshops, offices, living quarters for the workers and managers, and eight huge mooring blocks for the airships. It was an immediate change to the landscape, but it had a greater impact than just its physical footprint. Between 1911 and 1951 Barlow saw a 36% population increase – thought to be a result of the new military presence.

The First World War also began to change the demographics of the area. With more than 2 million men conscripted into the army during the conflict, women began to take up the traditionally male-held industrial jobs. When the war ended in November 1918, Armstrong-Whitworth employed 1,500 people – over 1,000 of those were women.

The airships take flight

Four airships were constructed over Barlow’s lifetime as a military facility, three of which made it to the air:

  • 25r

The 25r first took flight on 14 October 1917, but it encountered problems from the start. In the same manner as its predecessor the 23r, the craft did not have enough lift in trials. Subsequently, dynamos, bomb gear and furniture where stripped out to reduce the weight enabling the ship to make its first flight.

Despite later stability issues, the 25r served between December 1917 and September 1919, clocking up more than 221 hours of flight time and covering almost 9,500 kilometres.

  • R29

Armstrong-Whitworth’s next aircraft would prove to be one of Britain’s most successful riged-framed airships. Commissioned on 20 June 1918, the R29 flew for 335 hours and covered more than 13,000 kilometres in its five-month operational career.

During this time the R29 encountered German U-boats on three occasions. While the first escaped, the second struck a mine when pursued by the airship. The R29 attacked and destroyed a third U-boat off the coast of Northumberland in September 1918, dropping two 100 kilogram bombs on the UB115 submarine and recording the only success of any British wartime riged airship.

  • R33 

Designs for the R33 were well underway by September 1916, when the German L33 zeppelin was brought down in Essex while on a London-bombing raid. Despite the crew’s efforts to destroy the airship, it fell into British hands virtually intact, offering a trove of potential secrets.

Adapted with the information learned from the downed L33, the R33 was eventually completed after the November 1918 armistice, but nevertheless went on to operate for 10 years – longer than any other British riged airship.

Used with the kind permission of the Airship Heritage Trust

Taking flight for the first time on 6 March 1919, the R33 was initially used to promote ‘Victory Bonds’ around the country before being demilitarised.

Famously, the R33 was torn from its mast at Pulham in a gale and blown out over the North Sea. It took a partial crew 28 hours to eventually steer the damaged airship back to Pulham.

From military camp to nature reserve

Following the First World War, the land around Barlow was sold off to civilian firms until 1938 when the then-named ‘War Department’ took over the area to set up an army ordnance and command supply depot.

By the 60s, however, the UK’s need for military manufacturing had reduced. Instead, with increasing demand for power and rich coal seams found there, Barlow and the surrounding area became the site of what would become the UK’s biggest power station: Drax. Construction of Drax Power Station began exactly 50 years after the first Barlow airship took flight – and half a century ago from the present day.

Barlow Mound, which held the airship construction facility, is now a unique nature reserve under which Drax Power Station can safely store the ash created from generating power.

And while airships may seem like relics of a long-gone era of British skies, the vessels could be on the verge of a resurgence. The British-built Airlander 10 – an airship-aeroplane hybrid – is the longest aircraft in the world and recently received the green light from the European Aviation Safety Agency to start carrying out customer trials and demonstrations.

It can now fly at an elevation of 2,136m, up to 50 knots and 75 nautical miles away from its Bedfordshire airfield (which is located around eight miles from the proposed site of Millbrook Power, a Drax rapid response gas project). Perhaps a new golden era is on the horizon for British airships.

What hot weather means for electricity

29 August 2017

Power generation
Power boost, Fan pics

During the penultimate week of June 2017, temperatures of thirty degrees Celsius or more were recorded across the UK for five days straight. It was the hottest continuous spell of weather in the country since the 70s. And while this may sound like a minor headline, it’s evidence of an important fact: the world is getting warmer.

According to the Met Office, experiencing a ‘very hot’ summer is now likely to occur every five years rather than every 50. By the 2040s, more extreme heatwaves could become commonplace, and this could have serious consequences.

The extreme heatwave that hit Europe in 2003 led to a death toll in the tens of thousands and placed extreme strain on the continent – not only on its people, but on its infrastructure, too. If this weather is set to continue, what does it mean for our electricity network?

Electricity in extreme weather

In hot countries, electricity use soars in times of extreme weather due to increased use of cooling devices like air conditioning. One US study predicted an extreme temperature upswing could drive as much as an 7.2% increase in US peak demand.

In Northern Europe including the UK, where air conditioning is less prevalent, the effects of heat aren’t as pronounced, but that could change. In France, hot weather is estimated to have contributed to a 2 GW increase in demand this June.

The UK, which has traditionally only seen demand swings due to cold weather, is also beginning to feel the effects of extreme heat. According to Dr Iain Staffell of Imperial College London, for every degree rise in temperature during June 2017, electricity demand rose by 0.9% (300 MW). For example, on 19th June, when temperature averaged 21.9 degrees Celsius demand reached 32 GW. On the 25th, when temperatures dropped to an average of 15.9 degrees, demand shrank to 26.6 GW.

In the very hottest days of summer this can mean the grid needs to deliver an additional 1.5 GW of power – equivalent to the output of five rapid-response gas power stations or two-and-a-half biomass units at Drax Power Station.

And while heat’s effect on demand is considerable, it’s not the only one it has on electricity.

The problem of cooling water in hot weather

Generating power doesn’t just need fuel, it’s also a water-intensive process. Power stations consume water for two main reasons: to turn into steam to drive generation turbines, and to cool down machinery.

Both rely on raising the temperature of the water. However, this water can’t simply be released back into a river or lake after use – even if nothing has been added to it – as warm water can negatively affect wildlife living in these habitats. First, it has to be cooled – normally via cooling towers – but in hot weather this takes longer and, as a result, power production becomes less efficient and in some cases, plant output must be dialled back.

This had serious consequences for France’s nuclear power plants during the 2003 heatwave. These plants – which provide roughly 75% of the country’s electricity – draw water from nearby rivers to cool their reactors. During the heatwave, however, these rivers were both too hot and too low to safely provide water for the cooling process, which in turn led to the power stations having to either close or drastically reduce capacity.

Coupled with increased demand, France was left on the verge of a large-scale black out. Situations like this are even more critical when considering heat’s effects on electricity’s motorway: the national grid.

How the hot weather impacts electricity

When materials get hot, they expand – this includes those electricity grids are made from. For example, overhead power transmission cables are often clad in aluminium, which is particularly susceptible to expansion in heat. When it expands, overhead lines can slacken and sag, which increases electrical resistance in the cables, leading to a drop in efficiency.

Transformers, which step up and down voltage across grids, are also susceptible. They give off heat as a by-product of their operations. But to keep them within a safe level of operation, they have what’s known as a power rating – the highest temperature at which they can safely function.

When ambient temperatures rise, this ceiling gets lower and their efficiency drops – about 1% for every one degree Celsius gain in temperature. At scale, this can have a significant effect: overall, grids can lose about 1% in efficiency for every three degrees hotter it gets.

As global temperatures continue to rise, these challenges could grow more acute. At UK power stations, such as Drax, important upgrade and maintenance work takes place during the quieter summer months. If this period becomes one in which there is a higher demand for power at peak times, it could lead to new challenges.

Investing in infrastructure and building a power generation landscape that includes a mix of technologies and meets a variety of grid needs is one way in which we can counter the challenges of climate change. This will mean we can not only move towards a lower carbon economy and contribute towards slowing global warming, but respond to climate change by adapting essential national infrastructure to deal with its effects.