Nova Scotia Power Rate Regulation explains how the privately owned utility is governed by the Utility Review Board, limiting government authority, while COVID-19 relief measures include suspended disconnections, waived fees, payment plans, and emergency assistance.
Key Points
URB oversight where the board, not the province, sets power rates, with COVID-19 relief pausing disconnections and fees.
✅ Province lacks authority to order rate cuts
✅ URB regulates Nova Scotia Power rates
✅ Relief: no disconnections, waived fees, payment plans
The province can't ask Nova Scotia Power to lower its rates to ease the financial pressure on out-of-work residents because it lacks the authority to take that kind of action, even as the Nova Scotia regulator approved a 14% hike in a separate proceeding, the provincial energy minister said Thursday.
Derek Mombourquette said he is in "constant contact" with the privately owned utility.
"The conversations are ongoing with Nova Scotia Power," he said after a cabinet meeting.
When asked if the Liberal government would order the utility to lower electricity rates as households and businesses struggle with the financial fallout from the COVID-19 pandemic, Mombourquette said there was nothing he could do.
"We don't have the regulatory authority as a government to reduce the rates," he told reporters during a conference call.
"They're independent, and they are regulated through the (Nova Scotia Utility Review Board). My conversations with Nova Scotia Power essentially have been to do whatever they can to support Nova Scotians, whether it's residents or businesses in this very difficult time."
Asked if the board would take action, the minister said: "I'm not aware of that," despite the premier's appeals to regulators in separate rate cases.
However, the minister noted that the utility, owned by Emera Inc., has suspended disconnections for bill non-payment for at least 90 days, a step similar to reconnection efforts by Hydro One announced in Ontario.
It has also relaxed payment timelines and waived penalties and fees, while some jurisdictions offered lump-sum credits to help with bills.
Nova Scotia Power CEO Wayne O'Connor has also said the company is making additional donations to a fund available to help low-income individuals and families pay their energy bills.
In late March, Ontario cut electricity rates for residential consumers, farms and small businesses in response to a surge in people forced to work from home as a result of the pandemic, alongside bill support measures for ratepayers.
Premier Doug Ford said there would be a 45-day switch to off-peak rates, later moving to a recovery rate framework, which meant electricity consumers would be paying the lowest rate possible at any time of day.
The change was expected to cost the province about $162 million.
Three Mile Island Nuclear Debate spotlights subsidies, carbon pricing, wholesale power markets, grid reliability, and zero-emissions goals as Pennsylvania weighs keeping Exelon's reactor open amid natural gas competition and flat electricity demand.
Key Points
Debate over subsidies, carbon pricing, and grid reliability shaping Three Mile Island's zero-emissions future.
✅ Zero emissions credits vs market integrity
✅ Carbon pricing to value clean baseload power
✅ Closure risks jobs, tax revenue, and reliability
Three Mile Island is at the center of a new conversation about the future of nuclear energy in the United States nearly 40 years after a partial meltdown at the Central Pennsylvania plant sparked a national debate about the safety of nuclear power.
The site is slated to close in just two years, a closure plan Exelon has signaled, unless Pennsylvania or a regional power transmission operator delivers some form of financial relief, says Exelon, the Chicago-based power company that operates the plant.
That has drawn the Keystone State into a growing debate: whether to let struggling nuclear plants shut down if they cannot compete in the regional wholesale markets where energy is bought and sold, or adopt measures to keep them in the business of generating power without greenhouse gas emissions.
""The old compromise — that in order to have a reliable, affordable electric system you had to deal with a significant amount of air pollution — is a compromise our new customers today don't want to hear about."" -Joseph Dominguez, Exelon executive vice president Nuclear power plants produce about two-thirds of the country's zero-emissions electricity, a role many view as essential to net-zero emissions goals for the grid.
The debate is playing out as some regions consider putting a price on planet-warming carbon emissions produced by some power generators, which would raise their costs and make nuclear plants like Three Mile Island more viable, and developments such as Europe's nuclear losses highlight broader energy security concerns.
States that allow nuclear facilities to close need to think carefully because once a reactor is powered down, there's no turning back, said Jake Smeltz, chief of staff for Pennsylvania State Sen. Ryan Aument, who chairs the state's Nuclear Energy Caucus.
"If we wave goodbye to a nuclear station, it's a permanent goodbye because we don't mothball them. We decommission them," he told CNBC.
Three Mile Island's closure would eliminate more than 800 megawatts of electricity output. That's roughly 10 percent of Pennsylvania's zero-emissions energy generation, by Exelon's calculation. Replacing that with fossil fuel-fired power would be like putting roughly 10 million cars on the road, it estimates.
A closure would also shed about 650 well-paying jobs, putting the just transition challenge in focus for local workers and communities, tied to about $60 million in wages per year. Dauphin County and Londonderry Township, a rural area on the Susquehanna River where the plant is based, stand to lose $1 million in annual tax revenue that funds schools and municipalities. The 1,000 to 1,500 workers who pack local hotels, stores and restaurants every two years for plant maintenance would stop visiting.
Pennsylvanians and lawmakers must now decide whether these considerations warrant throwing Exelon a lifeline. It's a tough sell in the nation's second-largest natural gas-producing state, which already generates more energy than it uses. And time is running out to reach a short-term solution.
"What's meaningful to us is something where we could see the results before we turn in the keys, and we turn in the keys the third quarter of '19," said Joseph Dominguez, Exelon's executive vice president for governmental and regulatory affairs and public policy.
The end of the nuclear age?
The problem for Three Mile Island is the same one facing many of the nation's 60 nuclear plants: They are too expensive to operate.
Financial pressure on these facilities is mounting as power demand remains stagnant due to improved energy efficiency, prices remain low for natural gas-fired generation and costs continue to fall for wind and solar power.
Three Mile Island is something of a special case: The 1979 incident left only one of its two reactors operational, but it still employs about as many people as a plant with two reactors, making it less efficient. In the last three regional auctions, when power generators lock in buyers for their future energy generation, no one bought power from Three Mile Island.
But even dual-reactor plants are facing existential threats. FirstEnergy Corp's Beaver Valley will sell or close its nuclear plant near the Pennsylvania-Ohio border next year as it exits the competitive power-generation business, and facilities like Ohio's Davis-Besse illustrate what's at stake for the region.
Five nuclear power plants have shuttered across the country since 2013. Another six have plans to shut down, and four of those would close well ahead of schedule. An analysis by energy research firm Bloomberg New Energy Finance found that more than half the nation's nuclear plants are facing some form of financial stress.
Today's regional energy markets, engineered to produce energy at the lowest cost to consumers, do not take into account that nuclear power generates so much zero-emission electricity. But Dominguez, the Exelon vice president, said that's out of step with a world increasingly concerned about climate change.
"What we see is increasingly our customers are interested in getting electricity from zero air pollution sources," Dominguez said. "The old compromise — that in order to have a reliable, affordable electric system you had to deal with a significant amount of air pollution — is a compromise our new customers today don't want to hear about."
Strange bedfellows
Faced with the prospect of nuclear plant closures, Chicago and New York have both allowed nuclear reactors to qualify for subsidies called zero emissions credits. Exelon lobbied for the credits, which will benefit some of its nuclear plants in those states.
Even though the plants produce nuclear waste, some environmental groups like the Natural Resources Defense Council supported these plans. That's because they were part of broader packages that promote wind and solar power, and the credits for nuclear are not open-ended. They essentially provide a bridge that keeps zero-emissions power from nuclear reactors on the grid as renewable energy becomes more viable.
Lawmakers in Pennsylvania, Ohio and Connecticut are currently exploring similar options. Jake Smeltz, chief of staff to state Sen. Aument, said legislation could surface in Pennsylvania as soon as this fall. The challenge is to get people to consider the attributes of the sources of their electricity beyond just cost, according to Smeltz.
"Are the plants worth essentially saving? That's a social choice. Do they provide us with something that has benefits beyond the electrons they make? That's the debate that's been happening in other states, and those states say yes," he said.
Subsidies face opposition from anti-nuclear energy groups like Three Mile Island Alert, as well as natural gas trade groups and power producers who compete against Exelon by operating coal and natural gas plants.
"Where we disagree is to have an out-of-market subsidy for one specific company, for a technology that is now proven and mature in our view, at the expense of consumers and the integrity of competitive markets," NRG Energy Mauricio Gutierrez told analysts during a conference call this month.
Smeltz notes that power producers like NRG would fill in the void left by nuclear plants as they continue to shut down.
"The question that I think folks need to answer is are these programs a bailout or is the opposition to the program a payout? Because at the end of the day someone is going to make money. The question is who and how much?" Smeltz said.
Changing the market
Another critic is PJM Interconnection, the regional transmission organization that operates the grid for 13 states, including Pennsylvania, and Washington, D.C.
The subsidies distort price formation and inject uncertainty into the markets, says Stu Bresler, senior vice president in charge of operations and markets at PJM.
The danger PJM sees is that each new subsidy creates a precedent for government intervention. The uncertainty makes it harder for investors to determine what sort of power generation is a sound investment in the region, Bresler explained. Those investors could simply decide to put their capital to work in other energy markets where the regulatory outlook is more stable, ultimately leading to underinvestment in places where government intervenes, he added.
Three Mile Island nuclear power plant, Londonderry Township, Pennsylvania PJM believes longer-term, regional approaches are more appropriate. It has produced research that outlines how coal plants and nuclear energy, which provide the type of stable energy that is still necessary for reliable power supply, could play a larger role in setting prices. It is also preparing to release a report on how to put a price on carbon emissions in all or parts of the regional grid.
"If carbon emissions are the concern and that is the public policy issue with which policymakers are concerned, the simple be-all answer from a market perspective is putting a price on carbon," Bresler said.
Three Mile Island could be viable if natural gas prices rose from below $3 per million British thermal units to about $5 per mmBtu and if a "reasonable" price were applied to carbon, according to Exelon's Dominguez. He is encouraged by the fact that conversations around new pricing models and carbon pricing are gaining traction.
"The great part about this is everybody understands we have a major problem. We're losing some of the lowest-cost, cleanest and most reliable resources in America," Dominguez said.
Ontario Ultra-Low Overnight Electricity Rate lets eligible customers opt in to 2.4 cents per kWh time-of-use pricing, set by the Ontario Energy Board, as utilities roll out the plan between May 1 and Nov. 1.
Key Points
An OEB-set overnight TOU price of 2.4 cents per kWh for eligible Ontarians, rolling out in phases via local utilities.
✅ 8 of 61 utilities offering rate at May 1 launch
✅ About 20% of 5M customers eligible at rollout
✅ Enova Power delays amid merger integration work
A million households can opt into a new ultra-low overnight electricity rate offered by the Ministry of Energy, as province-wide rate changes begin, but that's just a fraction of customers in Ontario.
Only eight of the 61 provincial power utilities will offer the new rate on the May 1 launch date, following the earlier fixed COVID-19 hydro rate period. The rest have up to six months to get on board.
That means it will be available to 20 percent of the province's five million electricity consumers, the Ministry of Energy confirmed to CBC News.
The Ford government's new overnight pricing was pitched as a money saver for Ontarians, amid the earlier COVID-19 recovery rate that could raise bills, undercutting its existing overnight rate from 7.4 to 2.4 cents per kilowatt hour. Both rates are set by the Ontario Energy Board (OEB).
"We wanted to roll it out to as many people as possible," Kitchener-Conestoga PC MPP Mike Harris Jr. told CBC News. "These companies were ready to go, and we're going to continue to work with our local providers to make sure that everybody can meet that Nov. 1 deadline."
Enova Power — which serves Kitchener, Waterloo, Woolwich, Wellesley and Wilmot — won't offer the reduced overnight rate until the fall, after typical bills rose when fixed pricing ended province-wide.
Enova merger stalls adoption
The power company is the product of the recently merged Kitchener-Wilmot Hydro and Waterloo North Hydro.
The Sept. 1 merger is a major reason Enova Power isn't offering the ultra-low rate alongside the first wave of power companies, said Jeff Quint, innovation and communications manager.
"With mergers, a lot of work goes into them. We have to evaluate, merge and integrate several systems and processes," said Quint.
"We believe that we probably would have been able to make the May 1 timeline otherwise."
The ministry said retroactive pricing wouldn't be available, unlike the off-peak price freeze earlier in the pandemic, and Harris said he doesn't expect the province will issue any rebates to customers of companies that introduce the rates later than May 1.
"These organizations were able to look at rolling things out sooner. But, obviously — if you look at Toronto Hydro, London, Centre Wellington, Hearst, Renfrew — there's a dynamic range of large and smaller-scale providers there. I'm very hopeful the Region of Waterloo folks will be able to work to try and get this done as soon as we can," Harris said.
Alberta Power Grid Level 2 Alert signals AESO reserve power usage, load management, supply shortage from generator outages, low wind, and limited imports, urging peak demand conservation to avoid blackouts and preserve grid reliability.
Key Points
An AESO status where reserves power the grid and load management is used during supply constraints to prevent blackouts.
✅ Triggered by outages, low wind, and reduced import capacity
✅ Peak hours 4 to 7 pm saw conservation requests
✅ Several hundred MW margin from Level 3 load shedding
Alberta's energy grid ran on reserves Wednesday, after multiple factors led to a supply shortage, a scenario explored in U.S. grid COVID response discussions as operators plan for contingencies.
At 3:52 p.m. Wednesday, the Alberta Electric System Operator issued a Level 2 alert, meaning that reserves were being used to supply energy requirements and that load management procedures had been implemented, while operators elsewhere adopted Ontario power staffing lockdown measures during COVID-19 for continuity. The alert ended at 6:06 p.m.
"This is due to unplanned generator outages, low wind and a reduction of import capability," the agency said in a post to social media. "Supply is tight but still meeting demand."
AESO spokesperson Mike Deising said the intertie with Saskatchewan had tripped off, and an issue on the British Columbia side of the border, as seen during BC Hydro storm response events, meant the province couldn't import power.
"There are no blackouts … this just means we're using our reserve power, and that's a standard procedure we'll deploy," he said.
AESO had asked that people reduce their energy consumption between 4 and 7 p.m., similar to Cal ISO conservation calls during grid strain, which is typically when peak use occurs.
Deising said the system was several hundred MWs away from needing to move to an alert Level 3, with utilities such as FortisAlberta precautions in place to support continuity, which is when power is cut off to some customers in order to keep the system operating. Deising said Level 2 alerts are fairly rare and occur every few years. The last Level 3 alert was in 2013.
According to the supply and demand report on AESO's website, the load on the grid at 5 p.m. was 10,643 MW.
That's down significantly from last week, when a heat wave pushed demand to record highs on the grid, with loads in the 11,700 MW range, contrasting with Ontario demand drop during COVID when many stayed home.
A heat warning was issued Wednesday for Edmonton and surrounding areas shortly before 4 p.m., with temperatures above 29 C expected over the next three days, with many households seeing residential electricity use up during such periods.
Hong Kong Typhoon Mangkhut Power Outages strain households with blackouts, electricity disruption, and humid heat, impacting Tin Ping Estate in Sheung Shui and outlying islands; contractor-led restoration faces fines for delays and infrastructure repairs.
Key Points
They are blackout events after Typhoon Mangkhut, bringing heat stress, food spoilage, and delayed power restoration.
✅ 16 floors in Tin Ping Estate lost power after meter room blast.
✅ Contractor faces HK$100,000 daily fines for late restoration.
✅ Kat O and Ap Chau families remain off-grid in humid heat.
Nearly 600 Hong Kong families are still sweltering under the summer heat and facing dark nights without electricity after Typhoon Mangkhut cut off power supply to areas, echoing mass power outages seen elsewhere.
At Sheung Shui’s Tin Ping Estate in the New Territories, 384 families were still without power, a situation similar to the LA-area blackout that left many without service. They were told on Tuesday that a contractor would rectify the situation by Friday, or be fined HK$100,000 for each day of delay.
In remote areas such as outlying islets Kat O and Ap Chau, there were some 200 families still without electricity, similar to Tennessee storm outages affecting rural communities.
The power outage at Tin Ping Estate affected 16 floors – from the 11th to 26th – in Tin Cheung House after a blast from the meter room on the 15th floor was heard at about 5pm on Sunday, and authorities urged residents to follow storm electrical safety tips during repairs.
“I was sitting on the sofa when I heard a loud bang,” said Lee Sau-king, 61, whose flat was next to the meter room. “I was so scared that my hands kept trembling.”
While the block’s common areas and lifts were not affected, flats on the 16 floors encountered blackouts.
As her fridge was out of power, Lee had to throw away all the food she had stocked up for the typhoon. With the freezer not functioning, her stored dried seafood became soaked and she had to dry them outside the window when the storm passed.
Daily maximum temperatures rose back to 30 degrees Celsius after the typhoon, and nights became unbearably humid, as utilities worldwide pursue utility climate adaptation to maintain reliability. “It’s too hot here. I can’t sleep at all,” Lee said.
U.S. Wind Generation surpassed hydroelectric output in 2019, EIA data shows, becoming the top renewable electricity source, driven by PTC incentives, expanded capacity, and utility-scale projects across states, boosting the national electricity mix.
Key Points
U.S. Wind Generation is the nation's top renewable, surpassing hydro as EIA-tracked capacity grows under PTC incentives.
✅ EIA: wind topped hydro in 2019, over 300M MWh generated
✅ PTC credits spurred growth in utility-scale wind projects
✅ 103 GW installed; 77% added in the last decade
Last year saw wind power surging in the U.S. to overtake hydroelectric generation for the first time, according to data from the U.S. Energy Information Administration (EIA).
Released Wednesday, the figures from the EIA’s “Electric Power Monthly” report show that yearly wind generation hit a little over 300 million megawatt hours (MWh) in 2019. This was roughly 26 million MWh more than hydroelectric production.
Wind now represents the “most-used renewable electricity generation source” in the U.S., the EIA said, and renewables hit a 28% monthly record in April in later data.
Overall, total renewable electricity generation — which includes sources such as solar's 4.7% share in 2022 as one example, geothermal and landfill gas — at utility scale facilities hit more than 720 million MWh in 2019, compared to just under 707 million MWh in 2018. To put things in perspective, generation from coal came to more than 966 million MWh in 2019, while renewables surpassed coal in 2022 nationally according to later analyses.
According to the EIA’s “Today in Energy” briefing, which was also published Wednesday, generation from wind power has grown “steadily” across the last decade, and by 2020, renewables became the second-most prevalent source in the U.S. power mix.
This, it added, was partly down to the extension of the Production Tax Credit, or PTC, amid favorable government plans supporting solar and wind growth. According to the EIA, the PTC is a system which gives operators a tax credit per kilowatt hour of renewable electricity production. It applies for the first 10 years of a facility’s operation.
At the end of 2019, the country was home to 103 gigawatts (GW) of wind capacity, with 77% of this being installed in the last decade, and wind capacity surpassed hydro in 2016 according to industry data. The U.S. is home 80 GW of hydroelectric capacity, according to the EIA.
“The past decade saw a steady increase in wind capacity across the country and we capped the decade with a monumental achievement for the industry in reaching more than 100 GW,” Tom Kiernan, the American Wind Energy Association’s CEO, said in a statement issued Thursday.
“And more wind energy is coming, as the industry is well into investing $62 billion in new projects over the next few years that put us on the path to achieving 20 percent of the nation’s electricity mix in 2030,” Kiernan went on to state.
“As a result, wind is positioned to remain the largest renewable energy generator in the country for the foreseeable future.”
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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