Tag: electricity

Dude, where’s my autonomous car? How self-driving vehicles will impact electricity

25 April 2018

Electrification

The self-driving car is a sci-fi stalwart. The blend of familiar vehicle combined with advanced-artificial intelligence makes it a perfect symbol of a not-too-distant future which is fast approaching. But what a sci-fi movie is unlikely to show is a self-driving car pulling over for half an hour to fill its tank or recharge its batteries.

As autonomous vehicles gradually inch into our everyday life, the question of how they will be powered arises, as does whether they will be capable of refuelling or recharging without a helping human hand.

With governments around the world setting ambitious targets for the phasing out of diesel and petrol car sales, it’s safe to assume the driverless vehicles of the future will be electric.

But will they be able to charge themselves? More than that, how would a large influx of these cars coming onto our roads affect our national electricity demand and emissions?

How will driverless cars charge themselves?

Development is already well underway to bring human-free charging to the auto world with a variety of approaches being trialled:

  • Robotic charging points

The most straightforward way to enable self-driving electric vehicles (EVs) to charge themselves is through updating existing infrastructure. Adding on robotic limbs to standard charge points would be one way of removing the need for human hands. Tesla previously demonstrated a porotype of a snake-like arm that plugs into its vehicle’s charge points that does exactly this. 

  • Under-car charging

Easier than flailing robotic arms is the idea of charging cars from underneath a parked car. Unsurprisingly, Tesla has patented a version of the technology, too.

While building the technology into the ground adds complications, it could potentially allow cars to be charged while moving – which is exactly what one road in Sweden is doing.

The two kilometre stretch outside Stockholm features a metal track that an arm under EVs can connect to – much like a Scalextric track. The route is divided into 50-metre sections which are electrified separately as vehicles travel over them. Sweden is now planning to roll the concept out nationally.

  • Wireless charging

A step up from under-car charging, wireless technology uses inductive charging rather than physically connecting with the car, and can be installed into parking spaces, or be set into the tarmac.

The problem with this is it’s not as fast as directly connecting with the car. However, implemented at scale, entire roads could constantly charge vehicles when they need a top up.

It would mean that rather than taking EVs home and plugging them in, the city and roads themselves would charge it. But even the idea of keeping a car at home might fade as cars become increasingly autonomous.

Rethinking vehicle ownership

As more of the world’s population move to cities and they grow increasingly congested, car ownership is declining – a trend being further fueled by ridesharing services, like Uber, Lyft and Didi Chuxing in China.

And as services such as these continue to grow in popularity, it could point to a future where rather than owning self-driving cars, they will be shared among urban populations. Lyft Strategist Raj Kapoor suggested the reduced cost of maintenance of shared EVs would make rides cheap enough for the average person to ride in every day.

This could result in fewer cars on the roads as intelligent systems allow them to coordinate sharing across the population, which in turn could lead to a reduction in demand for charging. However, the more intense computing power needed in self-driving vehicles means they will each use more electricity than a standard EV.

Powering these sufficiently will depend on technology and coordination, rather than producing significantly more electricity.

Smarter cars, smarter cities, smarter electricity

Changes in car ownership could mean the total reshaping of cities. If cars don’t need to park for long periods of times on central roadsides and in garages, vehicles could instead be stored on the outskirts of cities when demand for transport is low and make their way into towns as people begin commuting.

This vision of cars, seemingly independently rolling around cities to exactly where they’re needed, depends not on a single car reacting to a single command, but to a network of data points connected to almost every aspect of a city. More than this, there’s even potential these cars could provide power as well as use it.

Vehicle-to-gird (V2G) technology means they can essentially act as batteries and return electricity to the grid when needed. A fully connected network of autonomous cars, linked to buildings, cities and entire electricity networks could be used to help meet demand on a local or national scale, helping avoid fossil fuel usage at times of stress.

While increasing EV usage will likely contribute to an increase in electricity demand, self-driving, smarter vehicles will ensure power is used at efficiently as possible and reduce the number of cars drawing electricity from the grid.

It ultimately means global investment in the charging infrastructure that will create a more connected and economical transport system, which will make widespread EV and autonomous cars a reality.

The electric transport revolution

16 April 2018

Electrification

With rapid technological improvements and falls in battery prices, improving performance and reducing the cost, experts predict that by 2050, 90% of new-build cars will be powered by electricity.

However, it’s not only roads where transport is decarbonising; electricity may soon power more of the world’s trains, plus its planes and boats.

Taking trains forward

The electrification of the rail industry has arguably been in the making for a lot longer than EVs but there’s still progress to be made. Trains are already one of the most-efficient modes of long-distance transport, and Network Rail claims electric models’ carbon emissions are 20% to 35% lower than diesel trains. Electric trains also accelerate and brake faster than diesel-powered models, and cause less wear to tracks.

Electrified trains are already commonplace in many parts of the world – Japan’s famously fast and reliable Shinkansen railways are electric. Meanwhile in the UK, less than 50% of the rail network is electrified, with Transport Secretary Chris Grayling’s recent ‘pause’ on development casting doubts on previous ambitious plans to electrify 850-miles of track.

Nevertheless, advancements are still being made to enable the sector to utilise solar energy as an alternative to the national power grid. The concept would prove cost effective and reduce the carbon footprint of trains even further.

According to a report by climate change charity 10:10 and researchers at Imperial College’s Energy Futures Lab, rail companies could cut their annual running costs by millions of pounds through installing their own trackside solar panels to power electric trains directly. With companies spending around £500 million a year on power, the savings on self-generation would enable them to cut fares for passengers, as well as emissions.

Take off for electric planes

Of all transport modes, air travel has made the least progress in electrification but there’s hope yet. Airbus, Rolls-Royce and Siemens recently teamed up to develop the technology needed to create electrically-powered aircraft. The companies plan to fly a demonstrator aircraft with one of its existing jet engines replaced by an electric unit in 2020.

Paul Stein, chief technology officer at Rolls-Royce, said: “Aviation is the last frontier of the electrification of transport. It could lead to a step change in the way we fly with greater efficiency and less noise.”

These proposed hybrid-electric aircraft are not powered by on-board batteries like EVs but with a gas turbine that generates electricity to drive the propellers. This could reduce fuel consumption by up to 10%, predicted Mark Cousin, head of flight demonstration at Airbus.

Moving to electric aircraft would also help the aviation industry meet EU targets of a 60% reduction in emissions of carbon dioxide (CO2) by 2020, as well as 90% less nitrogen oxides and a noise reduction of around 75%.

UK-based airline EasyJet also announced it could be flying electric planes within a decade and is teaming up with US firm Wright Electric to build battery-powered aircraft.

According to EasyJet, the move would enable battery-powered aeroplanes to travel short-haul routes such as London to Paris and Amsterdam, and Edinburgh to Bristol. Wright Electric is aiming for an aircraft range of 335 miles, which would cover the journeys of about a fifth of EasyJet passengers. The challenge comes in making lithium-ion batteries light and safe enough for the air.

The airline said this was the next step in making air travel less harmful for the environment, after cutting carbon emissions per passenger kilometre by 31% between 2000 and 2016. Wright Electric claims that electric planes will save up to 15% in fuel burn and CO2 emissions, be 50% quieter and 10% cheaper for airlines to buy and operate, with the cost saving potentially passed on to passengers.

Testing new waters

There’s a lot of buzz coming out of the maritime industry too. Every year marine transport emits 1,000 million tonnes of CO2, which is why the International Maritime Organization (IMO) has agreed that a reduction of 50% should come by 2050 compared with 2008 levels. Although the deal fell short of more ambitious targets preferred by those ranging from the European Union to environmental NGOs, the IMO did also commit to pursue efforts toward phasing out CO2 emissions entirely.

As Paris Agreement goals to cut carbon dioxide emissions loom, businesses around the world are innovating.

 

Small fleets of battery-powered boats designed for fjords and inland waterways in Norway, Belgium and the Netherlands are preparing to set sail, including some able to run autonomously without a crew.

Dutch company Port-Liner is also gearing up to launch the first fully-electric, emission-free barges in Europe. Dubbed ‘Tesla’ ships, Port-Liner Chief Executive Officer Ton van Meegen claims these barges would be the first in the world to sail on carbon-neutral batteries. The first six barges alone are expected to remove 23,000 trucks from the roads annually in the Netherlands, replacing them with zero-emission methods of transport.

China also recently launched an electric cargo ship to haul coal which, whilst not doing much for its ambitions to cut pollution, will at least eliminate shipping emissions from diesel engines. Electric ships may not yet be the norm globally but progress is underway to cut the 2.5% of global greenhouse emissions that result from the maritime transport industry.

Once a far-flung fantasy in some areas, electrified transport is fast becoming a reality. EVs and rail are leading the way, but it’s clear the electric transport revolution has a long way to travel.

Why does electricity have a sound?

11 April 2018

Electrification

On cold, misty mornings, the powerlines, pylons and transformers that make up Great Britain’s electricity system sometimes sound a little different. Stand in a field under a powerline and, in the right conditions, the usual sounds of the countryside might be interrupted by the crackling of electricity.

This buzzing crackle, which can be referred to as a corona discharge, occurs when there’s a change from the normal conditions of a power line’s insulators enabling the electric current to partially conduct along it or through the surrounding air to earth. This can come as a result of weather conditions or deterioration of the insulators.

It’s just one of the instances where electricity changes from an unseen force powering our lights and devices to something we can hear, see and even smell.

Why can we hear electricity?

The source of electricity’s sound is also determined by one of its inherent properties: frequency. Frequency is the measurement of multiple occurrences from events, such as sound waves from vibrations, over a period of time. Any equipment that has a frequency causing mechanical parts to undergo repeated change can be audible.

For example, if we hit a cymbal with a drumstick we can hear a crash because of the frequency of the vibrations the mechanical part (in this case the cymbal) makes. We hear a guitar because its strings are plucked and pulled to create vibration at different frequencies. And we can hear an audible hum in a transformer because electric currents affect its internal structure and cause vibrations.

The buzzy tone this creates can be referred to as ‘mains hum’ and is ever present, although not always perceptible to the human ear. It becomes audible, however, when electricity (specifically alternating current – AC) is applied to a transformer.

Transformers are made of lengths of copper or aluminium, which are wound around a steel laminated core. When AC is applied it magnetises the core and causes steel laminations in the transformer to expand and contract in a process known as magnetostriction. Although only small physical changes, these movements are enough to cause vibration, which in turn creates an audible hum.

The crackling overhead

With more than 7,200 km of overhead powerlines humming away constantly around the country, corona discharges are inevitable and common.

This happens when part of the insulators on a high-voltage line begins to deteriorate, is exposed to weather conditions, is damaged or contaminated, allowing electricity to partially flow along it. The surrounding air becomes electrically charged through a process known as ionisation and causes molecules to become charged and collide.

It’s these collisions in the air that make the corona audible. It can also be visible and gives off a distinct smell of ozone, the gas produced when air is ionised.

Although not dangerous to someone on the ground below, if the insulator on the powerline is left to deteriorate further it can fail completely, leading to earth faults that trip power systems.

Making use of electric hums

The sounds electricity creates may seem like a nuisance but they can also have important uses. One of the most innovative applications is in forensic analysis.

A technique called Electric Network Frequency (ENF) enables forensic scientists to validate audio recording by observing the frequency of the mains hum picked up by audio recordings, which is not audible to humans.

By comparing the frequency of the hum in a recording to a database of the country’s frequencies at given times, it’s possible to verify when and in which country the recording took place and detect any editing.

It highlights not only an innovative use of electricity, but just how pervasive and consistent a presence it is. So, while the ebb and flow of electricity through our lives often goes on without thought, it is always there, humming away while it powers modern life in Great Britain.

 

The shape of electricity use in 2018

31 January 2018

Power generation

In homes and offices, on streets and in shops, there are more electronic devices than ever. However, for all the phones, washing machines and TVs British consumers are plugging in, our electricity consumption has been on a downward tick – and has been since the middle of the last decade.

At the same time, an increasing percentage of our demand is being met by renewable and low-carbon energy sources. By 2016, greenhouse gas emissions from electricity had dropped to 62% below 1990 levels, helping the UK get close to meeting its third carbon budget target.

It’s the power sector that has seen the biggest reductions through the decline of coal, the greater use of gas and the rise of renewables. There are still big strides to make in the economy as a whole – particularly in sectors such as heat, transport and buildings. But there are positive signs of transformation that could help the country reach its fifth carbon budget goal of lowering emissions by 57% between 1990 and 2030.

Will 2018 prove to be another milestone year for Great Britain’s electricity system? And could the electrification of the economy help other sectors step-up their own decarbonisation?

The efficiency transformation

Reduced demand for electricity comes, in part, as a result of the decline in energy-intensive, manufacturing and heavy industry. However, in the domestic sector the decline has been equally significant. Since 2002, energy consumption in the home has fallen 19% from 52,229 ktoe (Kilotonne of Oil Equivalent) to 42,486 ktoe. As well as electricity, this includes gas, solid fuels such as coal and more.

This drop comes despite a growing population, economic growth, an increase in the number of households and a rising number of consumer devices and appliances. So, what exactly is bringing down energy consumption?

One cause is the increased efficiency of electronics and appliances. The phasing out of incandescent lightbulbs – which had hardly changed since Edison’s day – in favour of energy-saving models such as LEDs has reduced electricity used to light homes by a third since 1997. As well as the improved efficiency of large appliances, like fridge freezers, there is also a greater consumer awareness of electricity saving habits, such as washing clothes at lower temperatures.

The increase in small, battery-powered devices, such as smartphones, tablets and laptops on the other hand, means we’re spending less time using higher-powered equipment that constantly pulls from the grid, such as TVs and hi-fis.

What this can lead to, however, is a change in the shape of electricity demand (the ‘shape’ of power demand can be explored in Electric Insights). For example, overnight when many people choose to charge those battery-powered appliances. Such changes in demand present a challenge to forecasters at in National Grid’s control room, who predict ahead when, where and how much power will be needed from the country’s electricity grid.

Shifting demand spikes

Today’s peak electricity demand times remain relatively unchanged from the 20th century. People still come home and turn on lights, kettles and washing machines at around 5pm and 6pm.

But as artificial intelligence makes its way into more and more home appliances, these spikes are likely to level out across the day. Connected devices will aim to predict peak times and, where such tariffs are provided by energy suppliers, only run when overall demand costs are lower.

At the same time, lifestyles have changed, affecting electricity demand even further. In the past some of the biggest surges in UK electrical history came in the immediate aftermath of big TV moments, when people across the country switched on kettles, opened fridges and went to the toilet.


Now the proliferation of on-demand and online TV has reduced the need for National Grid to keep power stations on standby during major televised moments, as people choose to watch at their leisure rather than when they are broadcast.

Sports, however, remains one of the things that still attracts large numbers of live viewers. This June’s football World Cup means the National Grid will be braced for any surges in post-penalty shootout tea breaks.

Combined with a Royal Wedding – the last of which caused a significant spike – summer 2018 could see a few rare moments when mass TV viewing shunts electricity demand enough for it to be noticeable.

Cleaner power

But while 2018 may see some instances where demand surges, it’s likely power generation will continue to grow cleaner. The Department for Business, Energy and Industrial Strategy (BEIS) has released projections suggesting installed renewable electricity capacity could reach 36 gigawatts (GW) by 2030 – building on a 900% increase between 2007 and 2017.

It is, of course, important we continue to use electricity more efficiently. In 15 years from now, it’s predicted that power generation could begin to rise significantly and so decarbonising the production of power is arguably just as important as saving it.

This year will see another, flexible 600+ megawatt (MW) coal unit converted to sustainable biomass at Drax Power Station in Yorkshire and the first of 84 offshore wind turbines turned on as part of the 588MW Beatrice project in the Outer Moray Firth. These developments will quicken the pace of decarbonisation in Great Britain’s electricity network, meaning that positive trend that will continue.

This is the second story in a series on electricity demand through the ages, the first of which looked at the 1970s.

How did we use electricity in the 70s?

8 December 2017

Electrification

Great Britain’s energy mix is arguably in the best place it’s been in modern times. During the second quarter of 2017, 56% of our power came from lower-carbon energy sources. This includes renewable, nuclear and much of the power imported from France. By 2035, it’s projected that the amount of electricity generated by ‘major power producers’ from renewable sources like wind, solar and biomass could more than double from just over 80 terawatt hours (TWh) in 2016 to almost 180 TWh.

There is still a way to go, but the progress we’ve made is remarkable. Great Britain is now ranked seventh among large economies for electricity decarbonisation. It’s even more impressive when you consider where we’ve come from. Just five years ago, 38% of the UK’s electricity was generated from coal. Between April and August 2017, that share slipped to just 1.9%, and in April 2017 Britain went a full 24 hours without using any coal to generate its electricity – the first time this has happened since the Industrial Revolution.

If you look even further back, however, the difference is even more impressive.

Electricity in the 70s

Welcome to 1970s Britain. Striking workers in the power industry have prompted Edward Heath’s Conservative government to put in place the three-day week, limiting commercial use of electricity and putting curfews on television broadcasting. Since then a lot has changed, and this has had a marked effect on how we use electricity.

For one, the UK’s population has grown by nearly 10 million. More than that, the average number of electronic appliances per household has risen from 21 to 50.

In 1970 the average household had 16 lighting appliances, one cold (e.g. fridges and freezers), one wet (e.g. washing machines and dishwashers), one cooking appliance and two consumer electronic devices (e.g. a TV and a power supply unit). In comparison, the average today is 27 lighting, two cold, two wet, 13 consumer electronics, three cooking devices and an additional three home computing devices. The UK household today is far more reliant on electricity and electrical devices – unsurprisingly, this means how much electricity we use has changed.

Total household electricity consumption in 1970 was 2,995 ktoe (thousand tonnes of oil equivalent). In 2015, Britain used nearly double – 6,869 ktoe. And while this is a steep rise, our electricity use is currently on a downward trajectory.

Since peaking in 2007 at more than 8,000 ktoe, domestic electricity use has shrunk thanks to more efficient appliances. For example, an LED light bulb can use as much as 80% less electricity than a traditional incandescent one – and can last 25 times longer.

Our overall energy use (i.e. the sources beyond electricity that we use to fuel things like heating and transport) has also decreased since 1970. Households are using 12% less, while the relative decline of heavy industry and manufacturing in the UK means industry now uses 60% less energy than it did in 1970.

These gains are slightly offset by our growing love of mobility. In 1970, there were around 10 million cars on UK roads. Now there are around 26 million and we also take a lot more flights, which means the transport sector today uses roughly 50% more energy than in 1970.

Cleaning things up

Electricity consumption has changed since the 1970s. That’s no surprise, but what’s more important is the electricity we use is cleaner than it’s ever been. In 1970, we used 57 million tonnes of coal in power generation every year. By 2012 we were using just three million tonnes, and during the last four years coal output has fallen 82%. Instead, our electricity is increasingly coming from natural gas plus renewable and low carbon sources, a trend set to continue.

With the maturation of renewables, the increasing prevalence of smarter technologies and smarter, more efficient electricity grids, our energy system is set to remain in a state of positive change. A lot of progress has been made over the last 40 years – and it’s likely to continue over the next 40.

This is the first in a series on electricity demand through the ages, the second story of which looks at 2018. 

Every electricity storage technology you need to know about

24 November 2017

Power generation

The world is generating and using more renewable electricity than ever before, but in many cases it is being generated by intermittent – weather dependent – sources like solar and wind.

While these are imperative to a decarbonised future, they can’t generate power all the time, and this can cause gaps in electricity supply. One possible solution is storage. If we can store renewable electricity from intermittent sources when they are able to generate, it could then be utilised at times when they’re not.

However, the problem is the technology capable of storing electricity at a scale large enough to power a city doesn’t exist…yet.

The race to develop it is well under way, and several companies are working on building ever bigger, more efficient electricity storage methods. From pumping water up mountains to turning air into liquid, here are the emerging storage technologies (and some incumbent ones) shaping the storage landscape:

  1. Pumped hydropower

What if we could power cities with something as simple as gravity? And a mountain.

Pumped hydropower storage uses excess electricity to pump water from a lower reservoir up to a higher one (for example up a mountain or hill) where it is stored. When electricity is needed, the water is released from the higher reservoir and runs down the natural incline, passing through a typical hydro-power turbine to generate electricity.

Pumped hydro is one of the largest-capacity forms of grid power storage and currently accounts for 99% of all bulk storage globally. The Bath County Pumped Storage Station in Virginia, USA is often referred to as the ‘world’s biggest battery’, and boasts a generation capacity of more than 3 gigawatts (GW), which is almost as much as the power output of Drax Power Station or Hinkley Point C.

So what’s the catch? While pumped-hydro storage is efficient and capable of holding huge capacity, its major drawback is it requires a suitable mountain or hill to be converted into a giant battery. Unsurprisingly, not every landscape offers one. Great Britain has limited potential – but has a number of pumped storage facilities including the impressive Dinorwig in the Snowdonia region of Wales, known as the Electric Mountain which, like Drax, doubles up as a tourist attraction.

In December 2018, Drax bought Cruachan Power Station, the second biggest pumped-hydro storage power station in Great Britain. Visit Cruachan — The Hollow Mountain.

  1. Flywheels and supercapacitors

Some of the most-rapidly responding forms of energy storage, flywheel and supercapacitor storage can both discharge and recharge faster than most conventional forms of batteries.

The first works by spinning a rotor (or flywheel) to very high speeds using electrical energy. This process creates kinetic energy which is effectively stored within the spinning rotor until it’s required, at which point the kinetic energy is converted back into electricity.

Supercapacitors take a similar approach but store power electrically. With the combined properties of a battery and a capacitor, they store energy as a static charge, but unlike conventional batteries there is no chemical reaction during charging or discharging.

  1. Lithium-ion batteries

Lithium-ion batteries are already the go-to power source for most home electronics thanks to their high-energy density and low self-discharge rates. But companies are looking to extend their usage by rapidly advancing the technology to take on bigger and better uses, most notably electric vehicles (EVs) and providing security of supply to national and regional electricity networks.

In South Australia, Tesla has just finished installing the world’s biggest lithium-ion battery facility. At 100 megawatts (MW), it will be able to supply 30,000 homes for an hour, such as when the wind drops and the turbines of the wind farm it is connected to are not producing much power.

Lithium-ion batteries are now the most widely used in EVs, but manufacturers are still facing the challenge of lowering the cost of their manufacture to a point at which to make EVs widely accessible.

Tesla has made achieving this a priority, establishing its massive ‘gigafactory’ in Nevada to help ramp up production and drop the batteries’ price. A true breakthrough on this point is yet to be reached, however.

  1. Solid state batteries

The primary complaint for most domestic batteries today, be they in smartphones or EVs, is they just don’t last long enough. This is where solid-state batteries have a serious advantage.

Using solid electrodes and electrolytes rather than liquid electrolytes (used in most commercial batteries), solid-state models are smaller, cheaper and have a greater energy density than lithium-ion batteries. They can also be recharged much faster and emit less heat.

In an EV, this can lead to better efficiency, lower costs and safer operation. The only trouble is the technology isn’t quite viable at scale yet. Dyson and Toyota, are both putting serious money behind the technology and believe it will be on the market in 2020.

  1. Hydrogen fuel cells

Hydrogen is one of the most-abundant elements on earth, so it’s an attractive fuel for any power-generation technology. The latest to emerge is hydrogen fuel cells, which are quickly growing in popularity in the automotive space.

The fuel cells work similarly to batteries with two electrodes separated by an electrolyte. However, rather than running down and needing recharging, hydrogen fuel cells can continue to produce electricity so long as a constant supply of hydrogen and an oxidizer are pumped through it.

This means a regular supply of hydrogen needs to be fed in to continue to generate power – prompting the rise of fuelling stations where hydrogen-powered cars can be ‘filled up’ with hydrogen when their batteries have run dry.

Beyond powering cars, hydrogen fuel cells have also been used to power buildings and NASA satellites.

  1. Vehicle-to-grid systems

But what if beyond simply using electricity, EVs could themselves act as energy storage systems?

Between journeys, all cars spend long periods of time stationary. Vehicle-to-grid (V2G) systems can take advantage of this and give EVs the ability to discharge their stored electricity for distribution across the grid, helping meet demand during peak times. In effect, cars can become mini power plants.

Nissan and Italian energy provider Enel have already advanced plans for this sort of system and  aim to install around one hundred ‘car-to-grid’ charging points across the UK. EVs plugged into these sites will be able to both charge their batteries and feed stored energy back to the National Grid when necessary. Drax, too, is involved in this space, funding research into V2G systems at Sheffield University.

Smart charging systems will help to automate this give-and-take of electricity further and allow EVs to further help reduce overall carbon emissions.

  1. Compressed air energy

 Compressed air energy storage works similarly to pumped hydropower, but instead of pushing water uphill, excess electricity is used to compress and store energy underground. When electricity is needed, the pressurised air is heated (which causes it to expand) and released, driving a turbine.

Behind pumped hydro-energy, compressed air is the second-largest form of energy storage, and is continuously being developed to become more efficient and less dependent on fossil fuels to heat air.

And similarly to pumped hydro, it’s a site-specific means of storage. Compressed air is normally best stored in existing geological formations, such as disused hard rock or old salt mines.

  1. Lead-acid batteries

Their technology might be a century and a half old, but lead-acid batteries are still used today for the simple reason that they still work.

Many decades of development mean lead-acid batteries are cheap to produce and highly reliable compared to new innovations in the space. Today, they are most commonly used as car batteries, but they have also long served as off-grid storage for solar arrays.

Their drawbacks include the toxic nature of the chemicals involved and the short lifespan of 300 to 500 cycles. However, recycling programmes around these lead-acid batteries have been so effective that 99% of the batteries in the US were recycled between 2009 and 2013.

While more-efficient, longer lasting, faster charging and lighter batteries are in development, lead-acid models remain the cheap, tried-and-tested, standard for small-scale storage.

  1. Redox flow batteries

Specifically focusing on renewable energy storage, flow batteries are significantly cheaper than lithium-ion grid-scale storage, and offer a longer lifecycle.

Flow batteries consist of two tanks of liquids that are pumped into a reactor where they generate a charge. The capacity of the storage facility is therefore determined by the size of the tanks holding their respective liquids, which can mean they are bulky and space intensive.

Compared to other grid-scale storage systems, however, flow batteries are more economical, suffer lower vulnerabilities, and could hold potential to store large amounts of energy for long periods of time – one of the reasons why Drax is funding a PhD in the area. 

Liquid oxygen plant, tanks and heat exchange coils, the background a factory

  1. Liquefied air

What more abundant resource to use for energy storage than the air around us? By cooling air down to -196oC it is turned into a compressed liquid, which can be stored. When ambient air is exposed to this liquid it re-gasifies and expands in volume rapidly, rotating a turbine in the process.

One of the main advantages of this form of storage is its potentially high capacity – an impressive 700 litres of ambient air can be reduced to just one litre of liquid air. More than this, there is potential for it to become even more efficient by using waste heat and cold from industrial process such as thermal generation plants, steel milling, or the creation of liquefied natural gas (LNG).

UK company Highview Power Storage is currently trialling the technology at the Piliswoth landfill gas generation facility where it will provide energy storage as well as convert low-grade waste heat to power.

Want to find out more? Keep an eye on the Drax Repower project, which includes plans for up to 200 MW of storage. And Imperial College London’s Grantham Institute on Climate Change and the Environment produced this detailed infographic comparing the benefits and challenges faced by energy storage technologies.

The silent force that moves electricity

31 August 2017

Power generation

In the early evening of 14th August 2003, New York City, in the midst of a heatwave, lost its power. Offices, stores, transport networks, Wall Street and the UN building all found their lights and phones cut off. Gridlocked streets and a stalled subway system forced millions to commute home on foot while those unable to make it back to the suburbs set up camp around the city.

It wasn’t just the Big Apple facing blackout – what had started with several power lines in Northern Ohio brushing against an overgrown tree had spread in eight minutes to affect eight US states and two Canadian provinces. In total, more than 50 million people were impacted, $6 billion was lost in damages and 12 deaths were reported.

While a software glitch and the outdated nature of the power system contributed to the disaster, the spread from a few high-voltage power lines to the entire North West was caused by a lack of reactive power.

The pump powering electricity

Electricity that turns on light bulbs and charges phones is what’s known as ‘active power’ — usually measured in Watts (W), kilowatts (kW), megawatts (MW) or in even higher units. However, getting that active power around the energy system efficiently, economically and safely requires something called ‘reactive power’, which is used to pump active power around the grid. Reactive power is measured in mega volt amps reactive (MVAr).

It’s generated in the same way as active power by large power stations, but is fed into the system in a slightly different manner, which leads to limitations on how far it can travel. Reactive power can only be effective locally/regionally – it does not travel far. So, across the country there are regional reactive power distributors servicing each local area (imagine a long hose pipe that needs individual pumps at certain points along the way to provide the thrust necessary to transport water).

But power stations aren’t the only source of reactive power. Some electronic devices like laptops and TVs actually produce and feed small amounts of reactive power back into the grid. In large numbers, this increases the amount of reactive power on the grid, and when this happens power stations must absorb the excess.

This is because, although it’s essential to have reactive power on the grid, it is more important to have the right amount. Too much and power lines can become overloaded, which creates volatility on the network (such as in the New York blackout). Too little and efficiency decreases. Think, once again, of the long hose pipe – if the pressure is too great, the hose is at risk of bursting. If the pressure is too low, water won’t travel through it properly.

This process of managing reactive power is, at its heart, one of ensuring active power is delivered to the places it needs to be. But it is also one of voltage control – a delicate balancing act that, if not closely monitored, can lead to serious problems.

Keeping volatility at bay

Across Britain, all electricity on the national grid must run at the same voltage (either 400kV or 275kV – it is ‘stepped down’ from 132kV to 230V when delivered to homes by regional distribution networks). A deviation as small as 5% above or below can lead to equipment being damaged or large scale blackouts. National Grid monitors and manages the nationwide voltage level to ensure it remains within the safe limit, and doing this relies on managing reactive power.

Ian Foy, Head of Ancillary Services at Drax explains: “When cables are ‘lightly loaded’ [with a low level of power running through them], such as overnight when electricity demand is lower, they start emitting reactive power, causing the voltage to rise.”

To counter this, generators such as Drax Power Station, under instruction from National Grid, can change the conditions in their transformers from exporting to absorbing reactive power in just two minutes.

This relies on 24-hour coordination across the national grid, but as our power system continues to evolve, so do our reactive power requirements. And this is partly down to the economy’s move from heavy industry to business and consumer services.

The changing needs for reactive power

“Large industrial power loads, such as those required for big motors, mills or coal mines, bring voltage down and create a demand for more reactive power,” explains Foy. “Now, with more consumer product usage, the demand for active power is falling and the voltage is rising.”

The result is that Drax and other power stations now spend more time absorbing reactive power rather than exporting it to keep voltage levels down. In the past, by contrast, Foy says the power plant would export reactive energy during the day and absorb it at night.

As Britain’s energy system decarbonises, the load on powerlines also becomes lighter as more and more decentralised power sources such as wind and solar are used to meet local demand, rather than large power plants supplying wider areas.

This falling load on the power system increases the voltage and creates a greater need for generators to absorb reactive power from the system. It highlights that while Drax’s role in balancing reactive power has changed, it remains an essential service.

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 reserve power. View a summary at The great balancing act: what it takes to keep the power grid stable and find out what lies ahead by reading Balancing for the renewable future and Maintaining electricity grid stability during rapid decarbonisation.

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.

Why we need the whole country on the same frequency

23 June 2017

Power generation
Electricity frequency

The modern world sits on a volatile, fizzing web of electricity. In 2015 the UK consumed roughly 303 terawatt hours (TWh) of electricity, according to government statistics. That’s an awful lot of power humming around and, in this country, we take it for granted that electricity is controlled. This means the power supply coming into your home or place of work is reliable and won’t trip your fuse box. In short, it means your mobile phone will keep on charging and your washing machine will keep on spinning.

But generating and circulating electricity at safe, usable levels is not an easy task. One of the most overlooked aspects of doing this is electrical frequency – and how it’s regulated.

What is electrical frequency?

To understand the importance of frequency, we need to understand a couple of important things about power generation. Generators work by converting the kinetic energy of a spinning turbine into electrical energy. In a steam-driven generator (like those at Drax Power Station), high pressure steam turns a turbine, which turns a rotor mounted inside a stator. Copper wire is wound around the rotor energised with electricity, this turns it into an electromagnet with a north and south pole.

The stator is made up of large, heavy duty copper bars which enclose the rotor. As the rotor turns, its magnetic field passes through the copper bars and induces an electric current which is sent out onto the transmission system.

As the magnetic field has a north and south pole, the copper bars experience a change in direction of the magnetic field each time the rotor turns. This makes the electric current change direction twice per revolution and is called an alternating current (AC). There are in fact three sets of copper bars in the stator, producing three electrical outputs or phases termed red, yellow and blue.

Electrical frequency is the measure of the rate of that oscillation and is measured in the number of changes per second – also called hertz (Hz). A generator running at 3,000 rpm, with two magnetic poles, produces electricity at a frequency of 50Hz.

Turbine Hall at Drax Power Station

Why is this important? 

Maintaining a consistent electrical frequency is important because multiple frequencies cannot operate alongside each other without damaging equipment. This has serious implications when providing electricity at a national scale.

The exact figure is less important than the need to keep frequency stable across all connected systems. In Great Britain, the grid frequency is 50Hz. In the US, it’s 60Hz. In Japan, the western half of the country runs at 60Hz, and the eastern half of the country runs at 50Hz – a string of power stations across the middle of the country steps up and down the frequency of the electricity as it flows between the two grids.

Sticking to one national frequency is a team effort. Every generator in England, Scotland and Wales connected to the high voltage transmission system is synchronised to every other generator.

When the output of any of the three phases – the red, yellow or blue – is at a peak, the output from all other phases of the same colour on every other generating unit in Great Britain is also at a peak. They are all locked together – synchronised – to form a single homogenous supply which provides stability and guaranteed quality.

How is frequency managed?

The problem is, frequency can be difficult to control – if the exact amount of electricity being used is not matched by generation it can affect the frequency of the electricity on the grid.

For example, if there’s more demand for electricity than there is supply, frequency will fall. If there is too much supply, frequency will rise. To make matters more delicate, there’s a very slim margin of error. In Great Britain, anything just 1% above or below the standard 50Hz risks damaging equipment and infrastructure. (See how far the country’s frequency is currently deviating from 50 Hz.)

Managing electrical frequency falls to a country’s high voltage transmission system operator (the National Grid in the UK). The Grid can instruct power generators like Drax to make their generating units automatically respond to changes in frequency. If the frequency rises, the turbine reduces its steam flow. If it falls it will increase, changing the electrical output – a change that needs to happen in seconds.

In the case of generating units at Drax Power Station, the response starts less than a second from the initial frequency deviation. The inertial forces in a spinning generator help slow the rate of frequency change, acting like dampers on car suspension, which minimises large frequency swings.

Frequency on a fast-changing system

Not all power generation technologies are suited for providing high quality frequency response roles and as the UK transitions to a lower-carbon economy, ancillary services such as stabilisation of frequency are becoming more important.

Neither solar nor wind can be as easily controlled. It’s possible to regulate wind output down or hold back wind turbines to enable upward frequency response when there is sufficient wind.

Similarly, solar panels can be switched on and off to simulate frequency response. As solar farms are so widely dispersed and tend to be embedded – meaning they operate outside of the national system, it is not as easy for National Grid to instruct and monitor them. Both wind and solar have no inertia so the all-important damping effect is missing too. Using these intermittent or weather-dependent power generation technologies to help manage frequency can be expensive compared to thermal power stations.

Nor are the current fleet of nuclear reactors flexible – nuclear reactors in Great Britain were designed to run continuously at high loads (known as a baseload power). Although they cannot deliver frequency response services, the country’s nuclear power stations do provide inertia.

UK plug on blue wall

Twenty times faster

Thermal power generation technologies such as renewable biomass or fossil fuels such as coal and gas are ideal for frequency response services at scale, because they can be easily dialled up or down. As both the fuel supply to their boilers and steam within their turbines can be regulated, the 645 MW thermal power units at Drax have the capability to respond to the grid’s needs in as little as half a second or less, complete their change in output in under one second and maintain their response for many minutes or even hours.

Before the introduction of high volumes of wind and solar generation almost all generators (excluding nuclear) running on the system could provide frequency response. As these generators are increasingly replaced by intermittent technologies, the system operator must look for new services to maintain system stability.

An example is National Grid’s recent Enhanced Frequency Response tender, which asked for a solution that can deliver frequency stabilisation in under a second – 20 times faster than the Primary Response provided by existing thermal power stations. Drax was the only participating thermal power station, however all contracts were all won by battery storage projects.

Frequency future

Given the decline in fossil fuel generation and uncertainty around our power makeup in future decades, National Grid is consulting on how best to source services such as frequency response. The ideal scenario for National Grid is one where services can be increasingly sourced from reliable, flexible and affordable forms of low carbon generation or demand response.

The next generation of nuclear power stations, as with some already operating in France, can provide frequency response services. However the first of the new crop, Hinkley C, is around a decade away from being operational. Likewise, solar or wind coupled with battery, molten salt or flywheel storage will provide an increasing level of flexibility in the decades ahead as storage costs come down.

Thanks to power generation at Drax with compressed wood pellets, a form of sustainable biomass, Britain has already begun moving into an era where lower carbon frequency response can begin to form the foundation of a more reliable and cleaner system.

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 black start, system inertia, reserve power 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.