Although wind farms provide clean, green power – they do pose one problem for utilities: harmonic oscillations.
Since wind farms are generally located far away from load centers, power flow is increased using series capacitors to compensate for transmission line reactance. Unfortunately series capacitors can interact with the wind system, creating undamped sub-harmonic current oscillations that can cause serious damage to wind turbine controllers and also to conventional generators.
The wind turbine's own mechanical system interactions tower-to-blade can also generate sub-harmonics, which are detrimental to induction generators, transformers, and may cause resonance at the point of common coupling in the electrical grid. By isolating the healthy grid from sub-harmonic generation sources, damage to the electrical interconnection can be prevented.
ERLPhase Power Technologies recently announced the S-PRO Sub-Harmonic Protection Relay is proving itself to help control harmonic oscillations at a Minnesota wind farm.
“The S-PRO was installed at a wind farm substation in Trimont, Minnesota to detect subharmonic oscillations occurring at adjacent wind farms connected to the series compensated line,” said Pratap Mysore, Consulting Engineer at Xcel Energy. “In tests so far, the unit has performed well and the relay has been designed well to detect and protect against sustained harmonics from the wind turbines.”
The S-PRO 4000 relay provides real-time processing of voltage and current signals with sub-harmonic monitoring at 1 Hz intervals between 5 and 25 Hz 5 Hz, 6 Hz, 7 HzÂ… 23 Hz, 24 Hz and 25 Hz. It protects the grid from sub-harmonic oscillations at the point-of-common-coupling every 1 second, with additional user-configurable delays.
“Our sub-harmonic protection relay S-PRO is the first advanced microprocessor-based relay with 10 second high speed recording capability. It can also be used for detecting Sub Synchronous Resonance SSR frequencies,” commented Krish Narendra, Vice President of Technology and Quality at ERLPhase.
ERLPhase has a history of pioneering innovative protection and monitoring solutions including transformer loss-of-life monitoring in the T-PRO Transformer Protection Relay, dynamic swing recording in the L-PRO Transmission Line Protection Relay, the use of low impedance current inputs in the B-PRO Bus Protection Relay, and dynamic swing record capture with cross triggering in the TESLA Power System Recorder. All these innovations now find wide spread industry application.
Grid Transformer Waste Heat Recovery turns substations into neighborhood boilers, supplying district heating via heat networks, helping National Grid and SSE cut emissions, boost energy efficiency, and advance low carbon, net zero decarbonization.
Key Points
Grid Transformer Waste Heat Recovery captures substation heat for district heating, cutting emissions and gas use.
✅ Captures waste heat from National Grid transformers
✅ Feeds SSE district heat networks for nearby homes
✅ Cuts carbon, improves efficiency, aligns with net zero
Thousands of homes could soon be warmed by the heat from giant electricity grid transformers for the first time as part of new plans to harness “waste heat” and cut carbon emissions from home heating.
Trials are due to begin on how to capture the heat generated by transmission network transformers, owned by National Grid, to provide home heating for households connected to district heating networks operated by SSE.
Currently, hot air is vented from the giant substations to help cool the transformers that help to control the electricity running through National Grid’s high-voltage transmission lines.
However, if the trial succeeds, about 1,300 National Grid substations could soon act as neighbourhood “boilers”, piping water heated by the substations into nearby heating networks, and on into the thousands of homes that use SSE’s services.
“Electric power transformers generate huge amounts of heat as a byproduct when electricity flows through them. At the moment, this heat is just vented directly into the atmosphere and wasted,” said Nathan Sanders, the managing director of SSE Energy Solutions.
“This groundbreaking project aims to capture that waste heat and effectively turn transformers into community ‘boilers’ that serve local heat networks with a low- or even zero-carbon alternative to fossil-fuel-powered heat sources such as gas boilers, a shift akin to a gas-for-electricity swap in heating markets,” Sanders added.
Alexander Yanushkevich, National Grid’s innovation manager, said the scheme was “essential to achieve net zero” and a “great example of how, taking a whole-system approach, including power-to-gas in Europe precedents, the UK can lead the way in helping accelerate decarbonisation”.
The energy companies believe the scheme could initially reduce heat network carbon emissions by more than 40% compared with fossil gas systems. Once the UK’s electricity system is zero carbon, and with recent milestones where wind was the main source of UK electricity on the grid, the heating solution could play a big role in helping the UK meet its climate targets.
The first trials have begun at National Grid’s specially designed testing site at Deeside in Wales to establish how the waste heat could be used in district heating networks. Once complete, the intellectual property will be shared with smaller regional electricity network owners, which may choose to roll out schemes in their areas.
Tim O’Reilly, the head of strategy at National Grid, said: “We have 1,300 transmission transformers, but there’s no reason why you couldn’t apply this technology to smaller electricity network transformers, too, echoing moves to use more electricity for heat in colder regions.”
Once the trials are complete, National Grid and SSE will have a better idea of how many homes could be warmed using the heat generated by electricity network substations, O’Reilly said, and how the heat can be used in ways that complement virtual power plants for grid resilience.
“The heavier the [electricity] load, which typically reaches a peak at around teatime, the more heat energy the transformer will be able to produce, aligning with times when wind leads the power mix nationally. So it fits quite nicely to when people require heat in the evenings,” he added.
Other projects designed to capture waste heat to use in district heating schemes include trapping the heat generated on the Northern line of London’s tube network to warm homes in Islington, and harnessing the geothermal heat from disused mines for district heating networks in Durham.
Only between 2% and 3% of the UK is connected to a district heating network, but more networks are expected to emerge in the years ahead as the UK tries to reduce the carbon emissions from homes, alongside its nuclear power plans in the wider energy strategy.
Bruce Power Capacity Uprate boosts nuclear output through generator stator upgrades, turbine and transformer enhancements, and cooling pump improvements at Bruce A and B, unlocking megawatts and efficiency gains from legacy heavy water design capacity.
Key Points
Upgrades that raise Bruce Power capacity via stator, turbine, transformer, and cooling enhancements.
Bruce Power’s Unit 3 nuclear reactor will squeeze out an extra 22 megawatts of electricity, thanks to upgrades during its recent planned outage for refurbishment.
Similar gains are anticipated at its three sister reactors at Bruce A generating station, which presents the opportunity for the biggest efficiency gains and broader economic benefits for Ontario, due to a design difference over Bruce B’s four reactors, Bruce Power spokesman John Peevers said.
Bruce A reactor efficiency gains stem mainly from the fact Bruce A’s non-nuclear side, including turbines and the generator, was sized at 88 per cent of the nuclear capacity, Peevers said, while early Bruce C exploration work advances.
This allowed 12 per cent of the energy, in the form of steam, to be used for heavy water production, which was discontinued at the plant years ago. Heavy water, or deuterium, is used to moderate the reactors.
That design difference left a potential excess capacity that Bruce Power is making use of through various non-nuclear enhancements. But the nuclear operator, which also made major PPE donations during the pandemic, will be looking at enhancements at Bruce B as well, Peevers said.
Bruce Power’s efficiency gain came from “technology advancements,” including a “generator-stator improvement project that was integral to the uprate,” and contributed to an operating record at the site, a Bruce Power news release said July 11.
Peevers said the stationary coils and the associated iron cores inside the generator are referred to as the stator. The stator acts as a conductor for the main generator current, while the turbine provides the mechanical torque on the shaft of the generator.
“Some of the other things we’re working on are transformer replacement and cooling pump enhancements, backed by recent manufacturing contracts, which also help efficiency and contribute to greater megawatt output,” Peevers said.
The added efficiency improvements raised the nuclear operator’s peak generating capacity to 6,430 MW, as projects like Pickering life extensions continue across Ontario.
US Summer Energy Bills Crisis is driven by record heatwaves, soaring electricity prices, AC cooling demand, energy poverty risks, and LIHEAP relief, straining low-income households, vulnerable seniors, and budgets amid volatile utilities and peak demand.
Key Points
Rising household energy costs from extreme heat, higher electricity prices, and AC demand, straining vulnerable families.
✅ Record heatwaves drive peak electricity and cooling loads
✅ Tiered rates and volatile markets inflate utility bills
✅ LIHEAP aid and cooling centers offer short-term relief
As the sweltering heat of summer continues to grip much of the United States, American households are grappling with a staggering rise in energy bills. The combination of record-breaking temperatures and rising electricity prices is placing an unprecedented financial strain on families, raising concerns about the long-term impact on household budgets and overall well-being.
Record Heat and Energy Consumption
This summer has witnessed some of the hottest temperatures on record across the country. With many regions experiencing prolonged heatwaves, the demand for air conditioning and cooling systems has surged amid unprecedented electricity demand across parts of the U.S. The increased use of these energy-intensive appliances has led to a sharp rise in electricity consumption, which, combined with elevated energy prices, has pushed household energy bills to new heights.
The situation is particularly dire for households that are already struggling financially. Many families are facing energy bills that are not only higher than usual but are reaching levels that are unsustainable, underscoring electricity struggles for thousands of families across the country. This has prompted concerns about the potential for energy poverty, where individuals are forced to make difficult choices between paying for essential services and covering other necessary expenses.
Impact on Low-Income and Vulnerable Households
Low-income households and vulnerable populations are disproportionately affected by these soaring energy costs. For many, the financial burden of high energy bills is compounded by energy insecurity during the pandemic and other economic pressures, such as rising food prices and stagnant wages. The strain of paying for electricity during extreme heat can lead to tough decisions, including cutting back on other essential needs like healthcare or education.
Moreover, the heat itself poses a serious health risk, particularly for the elderly, children, and individuals with pre-existing health conditions. High temperatures can exacerbate conditions such as cardiovascular and respiratory illnesses, making the need for reliable cooling even more critical. For those struggling to afford adequate cooling, the risk of heat-related illnesses and fatalities increases significantly.
Utilities and Energy Pricing
The sharp rise in energy bills can be attributed to several factors, including higher costs of electricity production and distribution. The ongoing transition to cleaner energy sources, while necessary for long-term environmental sustainability, has introduced short-term volatility in energy markets. Additionally, power-company supply chain crises and increased demand during peak summer months have contributed to higher prices.
Utilities are often criticized for their pricing structures, which can be complex and opaque. Some regions, including areas where California electricity bills soar under scrutiny, use tiered pricing models that charge higher rates as energy consumption increases. This can disproportionately impact households that need to use more energy during extreme heat, further exacerbating financial strain.
Government and Community Response
In response to the crisis, various government and community initiatives are being rolled out to provide relief. Federal and state programs aimed at assisting low-income households with energy costs are being expanded. These programs, such as the Low-Income Home Energy Assistance Program (LIHEAP), offer financial assistance to help with utility bills, but demand often outstrips available resources.
Local community organizations are also stepping in to offer support. Initiatives include distributing fans and portable air conditioners, providing temporary cooling centers, and offering financial assistance to help cover energy costs. These efforts are crucial in helping to mitigate the immediate impact of high energy bills on vulnerable households.
Long-Term Solutions and Sustainability
The current crisis highlights the need for long-term solutions to address both the causes and consequences of high energy costs. Investing in energy efficiency and renewable energy technologies can help reduce the overall demand for electricity and lower long-term costs. Improvements in building insulation, the adoption of energy-efficient appliances, and advancements in smart grid technologies to prevent summer power outages are all essential components of a sustainable energy future.
Furthermore, addressing income inequality and supporting economic stability are critical to ensuring that all households can manage their energy needs without facing financial hardship. Policymakers will need to consider a range of strategies, including financial support programs, regulatory reforms, and infrastructure investments, to create a more equitable and resilient energy system.
Conclusion
As American households endure the double burden of extreme summer heat and skyrocketing energy bills, the need for immediate relief and long-term solutions has never been clearer. The current crisis serves as a reminder of the broader challenges facing the nation’s energy system and the importance of addressing both short-term needs and long-term sustainability. By investing in efficient technologies, supporting vulnerable populations, and developing resilient infrastructure, the U.S. can work towards a future where energy costs are manageable, and everyone has access to the resources they need to stay safe and comfortable.
Proton Conducting Fuel Cells enable reversible hydrogen energy storage, coupling electrolyzers and fuel cells with ceramic catalysts and proton-conducting membranes to convert wind and solar electricity into fuel and back to reliable grid power.
Key Points
Proton conducting fuel cells store renewable power as hydrogen and generate electricity using reversible catalysts.
✅ Reversible electrolysis and fuel-cell operation in one device
✅ Ceramic air electrodes hit up to 98% splitting efficiency
✅ Scalable path to low-cost grid energy storage with hydrogen
If we want a shot at transitioning to renewable energy, we’ll need one crucial thing: technologies that can convert electricity from wind, sun, and even electricity from raindrops into a chemical fuel for storage and vice versa. Commercial devices that do this exist, but most are costly and perform only half of the equation. Now, researchers have created lab-scale gadgets that do both jobs. If larger versions work as well, they would help make it possible—or at least more affordable—to run the world on renewables.
The market for such technologies has grown along with renewables: In 2007, solar and wind provided just 0.8% of all power in the United States; in 2017, that number was 8%, according to the U.S. Energy Information Administration. But the demand for electricity often doesn’t match the supply from solar and wind, a key reason why the U.S. grid isn't 100% renewable today. In sunny California, for example, solar panels regularly produce more power than needed in the middle of the day, but none at night, after most workers and students return home.
Some utilities are beginning to install massive banks of cheaper solar batteries in hopes of storing excess energy and evening out the balance sheet. But batteries are costly and store only enough energy to back up the grid for a few hours at most. Another option is to store the energy by converting it into hydrogen fuel. Devices called electrolyzers do this by using electricity—ideally from solar and wind power—to split water into oxygen and hydrogen gas, a carbon-free fuel. A second set of devices called fuel cells can then convert that hydrogen back to electricity to power cars, trucks, and buses, or to feed it to the grid.
But commercial electrolyzers and fuel cells use different catalysts to speed up the two reactions, meaning a single device can’t do both jobs. To get around this, researchers have been experimenting with a newer type of fuel cell, called a proton conducting fuel cell (PCFC), which can make fuel or convert it back into electricity using just one set of catalysts.
PCFCs consist of two electrodes separated by a membrane that allows protons across. At the first electrode, known as the air electrode, steam and electricity are fed into a ceramic catalyst, which splits the steam’s water molecules into positively charged hydrogen ions (protons), electrons, and oxygen molecules. The electrons travel through an external wire to the second electrode—the fuel electrode—where they meet up with the protons that crossed through the membrane. There, a nickel-based catalyst stitches them together to make hydrogen gas (H2). In previous PCFCs, the nickel catalysts performed well, but the ceramic catalysts were inefficient, using less than 70% of the electricity to split the water molecules. Much of the energy was lost as heat.
Now, two research teams have made key strides in improving this efficiency, and a new fuel cell concept brings biological design ideas into the mix. They both focused on making improvements to the air electrode, because the nickel-based fuel electrode did a good enough job. In January, researchers led by chemist Sossina Haile at Northwestern University in Evanston, Illinois, reported in Energy & Environmental Science that they came up with a fuel electrode made from a ceramic alloy containing six elements that harnessed 76% of its electricity to split water molecules. And in today’s issue of Nature Energy, Ryan O’Hayre, a chemist at the Colorado School of Mines in Golden, reports that his team has done one better. Their ceramic alloy electrode, made up of five elements, harnesses as much as 98% of the energy it’s fed to split water.
When both teams run their setups in reverse, the fuel electrode splits H2 molecules into protons and electrons. The electrons travel through an external wire to the air electrode—providing electricity to power devices. When they reach the electrode, they combine with oxygen from the air and protons that crossed back over the membrane to produce water.
The O’Hayre group’s latest work is “impressive,” Haile says. “The electricity you are putting in is making H2 and not heating up your system. They did a really good job with that.” Still, she cautions, both her new device and the one from the O’Hayre lab are small laboratory demonstrations. For the technology to have a societal impact, researchers will need to scale up the button-size devices, a process that typically reduces performance. If engineers can make that happen, the cost of storing renewable energy could drop precipitously, thereby moving us closer to cheap abundant electricity at scale, helping utilities do away with their dependence on fossil fuels.
Nation Rise Wind Farm Ruling overturns Ontario cancellation, as Superior Court finds the minister's decision unreasonable; EDP Renewables restarts 100-megawatt project near Cornwall, citing jobs, clean energy, and procedural fairness over bat habitat concerns.
✅ EDP Renewables to restart construction near Cornwall
✅ 100 MW, 29 turbines; costs awarded, appeal considered
Construction of a wind farm in eastern Ontario, as wind power makes gains nationwide, will move ahead after a court quashed a provincial government decision to cancel the project.
In a ruling released Wednesday, a panel of Ontario Superior Court judges said the province's decision to scrap the Nation Rise Wind Farm in December 2019 did not meet the proper requirements.
At the time, Environment Minister Jeff Yurek revoked the approvals of the project near Cornwall, Ont., citing the risk to three bat species.
That decision came despite a ruling from the province's Environmental Review Tribunal that determined the risk the project posed to the bat population was negligible.
The judges said the minister's decision was "unreasonable" and "procedurally unfair."
"The decision does not meet requirements of transparency, justification, and intelligibility, as the Minister has failed to adequately explain his decision," the judges wrote in their decision.
The company behind the project, EDP Renewables, said the 29-turbine wind farm was almost complete when its approval was revoked in December, even as Alberta saw TransAlta scrap a wind farm in a separate development.
The company said Thursday it plans to restart construction on the 100-megawatt wind farm.
"EDPR is eager to recommence construction of the Nation Rise Wind Farm, which will bring much-needed jobs and investment to the community," the company said in a statement. "This delay has resulted in unnecessary expenditures to-date, at a time when governments and businesses should be focused on reducing costs and restarting the economy."
A spokesman for Yurek said the government is disappointed with the outcome of the case but did not comment on a possible appeal.
"At this time, we are reviewing the decision and are carefully considering our next steps," Andrew Buttigieg said in a statement.
NDP climate change critic Peter Tabuns said the court decision is an embarrassment for the minister and the government. He urged the government not to pursue an appeal.
Yurek "was found to have ignored the evidence and the facts," he said. "They didn't just lose, their case collapsed. They had nothing to stand on. Taking this to appeal would be a complete and total waste of money."
Green party Leader Mike Schreiner said the ruling proves the government was acting based on ideology over evidence when it revoked the project's approval.
"As we shift towards a post-COVID recovery, we need the Ford government to give up the irrational crusade against affordable and reliable clean energy," Schreiner said in a statement.
Last year, the NDP revealed the province had spent $231 million to cancel more than 750 renewable energy contracts, a move Ford said he was proud of, shortly after winning the 2018 election.
The Progressive Conservatives have blamed the previous Liberal government, as leadership candidates debate how to fix power, for signing the bad energy deals while the province had an oversupply of electricity.
The Ford government, amid a new stance on wind power, has also said that by cancelling the contracts it would ultimately save ratepayers $790 million -- a figure industry officials have disputed.
At the time of the wind farm cancellation, the government also said it would introduce legislation that would protect consumers from any costs incurred, though a developer warned cancellations could exceed $100M at the time.
It has since acknowledged it will have to pay some companies to cancel the deals and set aside $231 million to reach agreements with those firms, and more recently has moved to reintroduce renewable projects in some cases.
On Wednesday, the judges awarded Nation Rise $126,500 in costs, which the government will have to pay.
Boeing 787 More-Electric Architecture replaces pneumatics with bleedless pressurization, VFSG starter-generators, electric brakes, and heated wing anti-ice, leveraging APU, RAT, batteries, and airport ground power for efficient, redundant electrical power distribution.
Key Points
An integrated, bleedless electrical system powering start, pressurization, brakes, and anti-ice via VFSGs, APU and RAT.
✅ VFSGs start engines, then generate 235Vac variable-frequency power
✅ Bleedless pressurization, electric anti-ice improve fuel efficiency
✅ Electric brakes cut hydraulic weight and simplify maintenance
The 787 Dreamliner is different to most commercial aircraft flying the skies today. On the surface it may seem pretty similar to the likes of the 777 and A350, but get under the skin and it’s a whole different aircraft.
When Boeing designed the 787, in order to make it as fuel efficient as possible, it had to completely shake up the way some of the normal aircraft systems operated. Traditionally, systems such as the pressurization, engine start and wing anti-ice were powered by pneumatics. The wheel brakes were powered by the hydraulics. These essential systems required a lot of physical architecture and with that comes weight and maintenance. This got engineers thinking.
What if the brakes didn’t need the hydraulics? What if the engines could be started without the pneumatic system? What if the pressurisation system didn’t need bleed air from the engines? Imagine if all these systems could be powered electrically… so that’s what they did.
Power sources
The 787 uses a lot of electricity. Therefore, to keep up with the demand, it has a number of sources of power, much as grid operators track supply on the GB energy dashboard to balance loads. Depending on whether the aircraft is on the ground with its engines off or in the air with both engines running, different combinations of the power sources are used.
Engine starter/generators
The main source of power comes from four 235Vac variable frequency engine starter/generators (VFSGs). There are two of these in each engine. These function as electrically powered starter motors for the engine start, and once the engine is running, then act as engine driven generators.
The generators in the left engine are designated as L1 and L2, the two in the right engine are R1 and R2. They are connected to their respective engine gearbox to generate electrical power directly proportional to the engine speed. With the engines running, the generators provide electrical power to all the aircraft systems.
APU starter/generators
In the tail of most commercial aircraft sits a small engine, the Auxiliary Power Unit (APU). While this does not provide any power for aircraft propulsion, it does provide electrics for when the engines are not running.
The APU of the 787 has the same generators as each of the engines — two 235Vac VFSGs, designated L and R. They act as starter motors to get the APU going and once running, then act as generators. The power generated is once again directly proportional to the APU speed.
The APU not only provides power to the aircraft on the ground when the engines are switched off, but it can also provide power in flight should there be a problem with one of the engine generators.
Battery power
The aircraft has one main battery and one APU battery. The latter is quite basic, providing power to start the APU and for some of the external aircraft lighting.
The main battery is there to power the aircraft up when everything has been switched off and also in cases of extreme electrical failure in flight, and in the grid context, alternatives such as gravity power storage are being explored for long-duration resilience. It provides power to start the APU, acts as a back-up for the brakes and also feeds the captain’s flight instruments until the Ram Air Turbine deploys.
Ram air turbine (RAT) generator
When you need this, you’re really not having a great day. The RAT is a small propeller which automatically drops out of the underside of the aircraft in the event of a double engine failure (or when all three hydraulics system pressures are low). It can also be deployed manually by pressing a switch in the flight deck.
Once deployed into the airflow, the RAT spins up and turns the RAT generator. This provides enough electrical power to operate the captain’s flight instruments and other essentials items for communication, navigation and flight controls.
External power
Using the APU on the ground for electrics is fine, but they do tend to be quite noisy. Not great for airports wishing to keep their noise footprint down. To enable aircraft to be powered without the APU, most big airports will have a ground power system drawing from national grids, including output from facilities such as Barakah Unit 1 as part of the mix. Large cables from the airport power supply connect 115Vac to the aircraft and allow pilots to shut down the APU. This not only keeps the noise down but also saves on the fuel which the APU would use.
The 787 has three external power inputs — two at the front and one at the rear. The forward system is used to power systems required for ground operations such as lighting, cargo door operation and some cabin systems. If only one forward power source is connected, only very limited functions will be available.
The aft external power is only used when the ground power is required for engine start.
Circuit breakers
Most flight decks you visit will have the back wall covered in circuit breakers — CBs. If there is a problem with a system, the circuit breaker may “pop” to preserve the aircraft electrical system. If a particular system is not working, part of the engineers procedure may require them to pull and “collar” a CB — placing a small ring around the CB to stop it from being pushed back in. However, on the 787 there are no physical circuit breakers. You’ve guessed it, they’re electric.
Within the Multi Function Display screen is the Circuit Breaker Indication and Control (CBIC). From here, engineers and pilots are able to access all the “CBs” which would normally be on the back wall of the flight deck. If an operational procedure requires it, engineers are able to electrically pull and collar a CB giving the same result as a conventional CB.
Not only does this mean that the there are no physical CBs which may need replacing, it also creates space behind the flight deck which can be utilised for the galley area and cabin.
A normal flight
While it’s useful to have all these systems, they are never all used at the same time, and, as the power sector’s COVID-19 mitigation strategies showed, resilience planning matters across operations. Depending on the stage of the flight, different power sources will be used, sometimes in conjunction with others, to supply the required power.
On the ground
When we arrive at the aircraft, more often than not the aircraft is plugged into the external power with the APU off. Electricity is the blood of the 787 and it doesn’t like to be without a good supply constantly pumping through its system, and, as seen in NYC electric rhythms during COVID-19, demand patterns can shift quickly. Ground staff will connect two forward external power sources, as this enables us to operate the maximum number of systems as we prepare the aircraft for departure.
Whilst connected to the external source, there is not enough power to run the air conditioning system. As a result, whilst the APU is off, air conditioning is provided by Preconditioned Air (PCA) units on the ground. These connect to the aircraft by a pipe and pump cool air into the cabin to keep the temperature at a comfortable level.
APU start
As we near departure time, we need to start making some changes to the configuration of the electrical system. Before we can push back , the external power needs to be disconnected — the airports don’t take too kindly to us taking their cables with us — and since that supply ultimately comes from the grid, projects like the Bruce Power upgrade increase available capacity during peaks, but we need to generate our own power before we start the engines so to do this, we use the APU.
The APU, like any engine, takes a little time to start up, around 90 seconds or so. If you remember from before, the external power only supplies 115Vac whereas the two VFSGs in the APU each provide 235Vac. As a result, as soon as the APU is running, it automatically takes over the running of the electrical systems. The ground staff are then clear to disconnect the ground power.
If you read my article on how the 787 is pressurised, you’ll know that it’s powered by the electrical system. As soon as the APU is supplying the electricity, there is enough power to run the aircraft air conditioning. The PCA can then be removed.
Engine start
Once all doors and hatches are closed, external cables and pipes have been removed and the APU is running, we’re ready to push back from the gate and start our engines. Both engines are normally started at the same time, unless the outside air temperature is below 5°C.
On other aircraft types, the engines require high pressure air from the APU to turn the starter in the engine. This requires a lot of power from the APU and is also quite noisy. On the 787, the engine start is entirely electrical.
Power is drawn from the APU and feeds the VFSGs in the engines. If you remember from earlier, these fist act as starter motors. The starter motor starts the turn the turbines in the middle of the engine. These in turn start to turn the forward stages of the engine. Once there is enough airflow through the engine, and the fuel is igniting, there is enough energy to continue running itself.
After start
Once the engine is running, the VFSGs stop acting as starter motors and revert to acting as generators. As these generators are the preferred power source, they automatically take over the running of the electrical systems from the APU, which can then be switched off. The aircraft is now in the desired configuration for flight, with the 4 VFSGs in both engines providing all the power the aircraft needs.
As the aircraft moves away towards the runway, another electrically powered system is used — the brakes. On other aircraft types, the brakes are powered by the hydraulics system. This requires extra pipe work and the associated weight that goes with that. Hydraulically powered brake units can also be time consuming to replace.
By having electric brakes, the 787 is able to reduce the weight of the hydraulics system and it also makes it easier to change brake units. “Plug in and play” brakes are far quicker to change, keeping maintenance costs down and reducing flight delays.
In-flight
Another system which is powered electrically on the 787 is the anti-ice system. As aircraft fly though clouds in cold temperatures, ice can build up along the leading edge of the wing. As this reduces the efficiency of the the wing, we need to get rid of this.
Other aircraft types use hot air from the engines to melt it. On the 787, we have electrically powered pads along the leading edge which heat up to melt the ice.
Not only does this keep more power in the engines, but it also reduces the drag created as the hot air leaves the structure of the wing. A double win for fuel savings.
Once on the ground at the destination, it’s time to start thinking about the electrical configuration again. As we make our way to the gate, we start the APU in preparation for the engine shut down. However, because the engine generators have a high priority than the APU generators, the APU does not automatically take over. Instead, an indication on the EICAS shows APU RUNNING, to inform us that the APU is ready to take the electrical load.
Shutdown
With the park brake set, it’s time to shut the engines down. A final check that the APU is indeed running is made before moving the engine control switches to shut off. Plunging the cabin into darkness isn’t a smooth move. As the engines are shut down, the APU automatically takes over the power supply for the aircraft. Once the ground staff have connected the external power, we then have the option to also shut down the APU.
However, before doing this, we consider the cabin environment. If there is no PCA available and it’s hot outside, without the APU the cabin temperature will rise pretty quickly. In situations like this we’ll wait until all the passengers are off the aircraft until we shut down the APU.
Once on external power, the full flight cycle is complete. The aircraft can now be cleaned and catered, ready for the next crew to take over.
Bottom line
Electricity is a fundamental part of operating the 787. Even when there are no passengers on board, some power is required to keep the systems running, ready for the arrival of the next crew. As we prepare the aircraft for departure and start the engines, various methods of powering the aircraft are used.
The aircraft has six electrical generators, of which only four are used in normal flights. Should one fail, there are back-ups available. Should these back-ups fail, there are back-ups for the back-ups in the form of the battery. Should this back-up fail, there is yet another layer of contingency in the form of the RAT. A highly unlikely event.
The 787 was built around improving efficiency and lowering carbon emissions whilst ensuring unrivalled levels safety, and, in the wider energy landscape, perspectives like nuclear beyond electricity highlight complementary paths to decarbonization — a mission it’s able to achieve on hundreds of flights every single day.
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