Tag: flexibility and stability and power system security

Result of General Meeting

RNS Number : 2803L
Drax Group PLC
No.Brief DescriptionVotes For%Votes Against%Votes TotalVotes Withheld
1. To approve the acquisition of the entire issued share capital of ScottishPower Generation Limited268,580,49485.7544,619,02714.25313,199,52121,841

The resolution was carried. Completion of the acquisition is expected to occur on 31 December 2018.

The number of shares in issue is 407,193,168 (of which 12,867,349 are held in treasury. Treasury shares don’t carry voting rights).

Votes withheld are not a vote in law and have not been counted in the calculation of the votes for and against the resolution, the total votes validly cast or the calculation of the proportion of issued share capital voted.

A copy of the resolution is available for inspection in the Circular, which was previously submitted to the UK Listing Authority’s Document Viewing Facility, via the National Storage Mechanism at www.morningstar.co.uk/uk/NSM.

The Circular and the voting results are also available on the Company’s website at www.drax.com.

Enquiries

Drax Investor Relations

Mark Strafford
+44 (0) 1757 612 491
+44 (0) 7730 763 949

Media, Drax External Communications

Matt Willey
+44 (0) 7711 376 087

Website: www.drax.com

END

Balancing for the renewable future

It’s not news to say Great Britain’s electricity system is changing. Low carbon electricity sources are on course to go from 22% of national generation in 2010 to 58% by 2020 as installation of wind and solar systems continue to grow.

But while there has been much change in the sources fuelling electricity generation, the system itself is still adapting to this transformation.

When the national grid was first established in the 1920s, it was designed with coal and big spinning turbines in mind. It meant that just about every megawatt coming onto the system was generated by thermal power plants. As a result, the mechanisms keeping the entire system stable – from the way frequency and voltage is managed to how to start up the country after a mass black out – relied on the same technology. These ‘ancillary services’ – those that stabilise the system – are crucial to maintaining a balanced electricity system.

“Ancillary services are needed to make sure demand is met by generation, and that generation gets from one place to the next with no interruptions,” explains Ian Foy, Head of Ancillary Services at Drax. “Because what’s important is that all demand must be met instantaneously.”

In today’s power system, however, weather dependent technology like offshore wind and home solar panels are increasingly making up the country’s electricity generation. Their intermittency or variability is, in turn, impacting both the stability of the grid and how ancillary services are provided.

Running a large power system with as much as 85% intermittent generation – for example on a very windy, clear, sunny day – is thought to be achievable. It isn’t a scenario anticipated for the large island of Great Britain. But to deal with the fast-pace of change on its power system which recently managed to briefly achieve  47% wind in its fuel mix, there is a need to develop new techniques, technologies and ways of working to change how the country’s grid is balanced.

New storage tech takes on balancing services

One of the technologies that’s expected to provide an increasing amount of balancing services is grid-scale batteries. One stabilisation function offered by batteries (and other electricity storage options) is to provide reserve  at times when demand peaks or troughs. This matches electricity demand and generation.

Combined with their ability to respond quickly to changes in frequency, batteries can be a significant source of frequency response.

Batteries can also absorb and generate reactive power, which can then be deployed to push voltage up or down when it starts to creep too far from the 400kV or 275kV target (depending on the powerlines the electricity is travelling along) needed to safely move electricity around the grid.

The challenge with batteries is that the quantity of megawatt hours (MWh) required to compensate for intermittency is very large. The difference between the peak and trough on any day may be more than 20 GW for several hours (see for yourself at Electric Insights).

The significant price reductions in battery storage apply to technologies with short duration (or low volume MWhs). These are the technologies which have been developed at scale recently but will probably struggle to make up in any large quantity any shortfalls in generation resulting from prolonged periods of low intermittent generation.

A challenge currently being addressed relates to maintenance of battery state of charge. This is a consequence of battery storage having a cycle efficiency of less than 100%. This means that losses from continuous charging and recharging will have to be replenished from the available generation to avoid batteries going empty and being unavailable for grid services.

Ultra-low carbon advances

Rather than relying on batteries to provide ancillary services to support intermittent generation, technical advancements are allowing the wind and solar facilities – which are generating more and more of the country’s electricity – to do so themselves.

The traditional photovoltaic (PV) inverters found on solar arrays were initially designed to push out as much active, or real, power as possible. However, new smart PV inverters are capable of providing or absorbing reactive power when it is needed to help control voltage, as well as continuing to provide active power.

The major advantage of smart inverters is the limited equipment update required to existing solar farms to allow them to offer reactive power control. The challenge here is that PV is embedded in distribution systems and therefore reactive services they provide may not cure all the problems on the transmission system.

Similarly, existing wind installations have traditionally focused on getting the greatest amount of megawatts from the available resources, but with fewer thermal power stations on the grid, ways of balancing the system with wind turbines are also being developed.

Inertia is the force that comes from heavy spinning generators and acts as a damper on the system to limit the rate of change of frequency fluctuations. While wind turbines have massive rotating equipment, they are not connected to the grid in a way that they automatically provide inertia, however, research is exploring what’s known as ‘inertial response emulation’ that may allow wind turbines to offer faster frequency response.

This works through an algorithm that measures grid frequency and controls the power output of a wind turbine or whole farm to compensate for frequency deviations or quickly provide increases or decreases in power on the system. Inertial response emulation cannot be a complete substitute for inertia but can reduce the minimum required inertia on the system.

Even in a future where the majority of the country’s electricity comes from renewable sources, thermal generators may still be able to provide benefits to the system by running in ‘synchronous compensation’ mode i.e. producing or consuming reactive power without real power.

However, what is vitally important for the future of balancing services in Great Britain is a healthy, transparent and investable market for generators, demand side response and storage, whether connected on the transmission or distribution networks.

A market for the future grid

One of the primary needs of balancing service providers is greater transparency into how National Grid procures and pays for services. Currently, National Grid does not pay for inertia. With it becoming more important to grid stability, incentive is needed to encourage generators with the capability to provide it. Those technologies that can’t provide inertia, could be encouraged to research and develop ways they could do so in the future.

Standardising the services needed will help ensure providers deliver balancing products to the same level needed to support the grid. It would also benefit from fixed requirements and timings for such services. Bundling related products, such as reserve and frequency control, and active power and voltage management, will also offer operational and cost efficiencies to the providers.

Driving investment in balancing services for the future, ultimately, requires the availability of longer-term contracts to offer financial certainty for the providers and their investors.

 

Bridge to the future

The energy mix -- table showing services which can be provided by different power technologies

Click to view larger graphic.

For the challenges of decarbonisation to be met in a socially responsible way, Great Britain’s power system must be operated at as low a cost as possible to consumers.

With new technologies, almost anything could be possible. But operating them has to be affordable. In many cases, it may take time for costs of long duration batteries to come down – as it has with the most recent offshore wind projects to take Contracts for Difference (CfDs) and Drax’s Unit 4 coal-to-biomass conversion under the Renewables Obligation (RO) scheme.

Thermal power technologies such as gas that has proven capabilities in ancillary services markets can at least be used in a transitional period over the coming decades until a low carbon solution is developed.

Biomass will continue to be an important source of flexible power. This summer, at Drax, biomass units are helping to balance the system. It is the only low carbon option which can displace the services provided by coal or gas entirely.


Drax Power Station’s control room. Viewing on a computer? Click above and drag. On a phone or tablet – just move your device.

In the past the race to decarbonisation was largely based around building as great a renewable capacity as possible. This approach has succeeded in significantly scaling up carbon-free electricity’s role on Great Britain’s electricity network. However, for the grid to remain stable in the wake of this influx, all parties must adapt to provide the balancing services needed.

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

The night shift

Draw power station at night

Things are different at night. As darkness falls the familiar sights and sounds that make up daily life retreat, creating a strange yet familiar world. There’s less activity, but that doesn’t mean there is no activity.

While Great Britain sleeps, phones charge and fridges hum. Electricity is a 24-hour need, and so the stations generating it must be 24-hour operations. But the life of a power station by night is very different to that by day.

“Walking around the power station at night can almost feel like the Mary Celeste,” says Simon Acaster, Drax Power Station’s Generation Manager. “There may be as few as 50 to 60 people on site, which isn’t a lot when you consider the size of the plant and compare it to the day, when there are some 650 people around.”

Drax Power Station by day is a hive of activity. Alongside generation there are maintenance, engineering, trading and contract support. At night, this is all stripped back.

“Work is focused on the core production issues: looking after the asset and maintaining power generation output to meet our contract position, keeping the teams safe and making sure we stay environmentally compliant,” says Mark Rhodes, Shift Manager at Drax.

“It’s a quieter place,” he adds.

Keeping power flowing

The nightshift at Drax Power Station

Typically, teams at Drax swap over at 8pm and 8am on a cycle of day and night shifts. During the summer months, when one or more of the station’s six, 600+ megawatt (MW) units can be on outage and maintenance is carried out across the station, work often continues around the clock right through the night.

But during a period of normal operation, the night workforce is reduced to basic operations and maintenance teams, material handling teams receiving biomass deliveries – which continue through the night – and security staff.

Demand for electricity typically falls overnight, so Drax shuts down unneeded generation units around 10pm. As morning approaches teams prep them to restart in time for when people wake up and turn on kettles.

“Even when we shut the units down, the turbine is still turning throughout the night,” says Acaster. “All the hydraulic pumps and lube oil systems are still functioning. A lot of plant is in service even when the units are shut down.”

This means there’s still the potential, as during the day, for something to need maintenance or attention at any moment requiring the teams to jump into action.

“We aim to sort any short-term issues through the night,” says Rhodes. “But for any technical issues that can wait, we tackle them when the day team returns and we’re fully staffed. At night it’s more about safely managing the asset.”

The hardest part of a running the power station overnight, however, is not a technical one, it’s a human one.

“There’s no doubt about it, working nights is tiring,” says Acaster. “The biggest challenge is keeping everybody focused and aware of what’s happening.”

He continues: “Unit controllers regularly talk to their plant operators, checking in every hour so we know they’re safe. Supervisors need to be out on plant engaging and talking to employees, checking on what they’re doing and keeping them active and alert.”

The shifting of the night shift

The decarbonisation of Great Britain’s electricity system has changed the way Drax operates during the day, and the same is true of the night.

“Historically, we had six units and they would be baseload, generating 645 MW each,” says Rhodes. “They would operate continuously day and night.” But with the demand profile changing, lower power prices, and other methods of generation coming onto the system, that model is changing.

“Overnight is normally the time of least demand and when the price of power becomes most depressed,” Rhodes continues. “So we take units off and prepare them for the morning, returning when there is value.”

Regularly shutting down and starting the units takes a tougher toll on the equipment than running them continuously, which increases the need for maintenance teams on night shifts. There’s also a need for teams to be on standby to ramp up or down generation.

The increased volatility of the country’s power network, brought on in part by increasing levels of intermittent renewables, means National Grid can often ask Drax to increase or decrease generation at short notice to provide balancing services like inertia, frequency response or reserve power.

“Our units can come down to 300 MW and stay at that level,” says Acaster. “Across three units that gives National Grid 900 MW of spare capacity that can be turned up. It’s like a sleeping giant awaiting start up at any time.”

But unlike other sleeping giants this one is never truly at rest. The demands of the network keep it, and the men and women operating it, humming through the night, 24-hours a day. The power station at night is a quieter place, but it is never a silent one.

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

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.

Click to view/download

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 black startsystem inertiafrequency responsereactive power and reserve power.  Find out what lies ahead by reading Balancing for the renewable future and Maintaining electricity grid stability during rapid decarbonisation.

Securing reliable and flexible energy this winter

Preparing for winter is one of the UK power system’s biggest challenges. Shorter days and falling temperatures ramp up demand for electricity and gas to power lights and heating across the country. This can put strain on the grid, even leading to blackouts if not carefully managed.

In anticipation of potentially difficult times, National Grid assesses Britain’s winter energy system to determine how much power we’re going to need, and more importantly, to ensure generators can produce enough to meet demand.

In its most recent report looking at winter 2017/18, National Grid’s take is a positive one: there will be enough power to meet demand. More than that, it has the potential to be cleaner than ever before.

What to expect from electricity this winter

In the report, National Grid forecasts a surplus power margin (how much generation capacity will exceed estimated demand) of 10.3% – a significant increase from last year’s 5.7% margin.

What does this mean in real terms? The report predicts a peak electricity demand of nearly 51 GW during the darkest, coldest days of mid-December. By contrast, the total possible capacity of the UK’s energy system during winter is 101.2 GW, not including interconnectors importing power from abroad.

It is important to note, however, that 101.2 GW is more a theoretical number than an expected one. Considering normal occurrences such as planned outages, breakdowns, or other operational issues that prevent power stations generating their usual output, a more accurate estimate is 66.1 GW.

But electricity isn’t the only resource put under strain in the winter months – gas is also in high demand for heating and for electricity generation. In the report, National Grid predicts this winter to have a lower gas demand than last year, owing largely to a decrease in gas-fuelled electricity generation. However, where gas-fired electricity is likely to remain integral is in plugging the gaps in electricity supply left by intermittent renewables.

The system under stress

Weather plays a huge part in both the consumption and generation of power. During the winter, when days are shorter and darker, and the wind calmer, solar and wind cannot generate and feed into the power grid as they normally would.

This means when there are sudden spikes in demand (such as in a cold snap), National Grid must secure other sources to avoid disruption, which can sometimes include carbon-intensive coal, diesel generators, or importing power from Europe.

This growing pressure on the system requires flexible and reliable sources of energy that can quickly react to these sudden surges.

“Biomass is a reliable, flexible renewable and available at scale. It’s able to provide the full range of support services the grid needs to retain stable supplies – whatever the weather,” says Drax Power CEO, Andy Koss.

Drax Power Station’s south cooling towers recycle water and feed it back into the boilers, where 17% of the UK’s renewable electricity is generated

Low-carbon winter energy

The ability to secure sufficient, reliable and lower-carbon power over the winter months is key to the ongoing decarbonisation of the UK. Biomass and gas will play an important role in allowing the country to operate with less dependence on fossil fuels.

We’ve already made significant headway in this field. Last year, Christmas Day was powered by more renewable electricity than ever before, while each quarter of 2017 has seen new clean energy records broken.

As we move into another winter, it’s imperative generators and operators focus on the security of supply. That the stability of our power system will be secured by lower carbon sources is an added – and much needed – bonus.