The heart of the Kenworth T270 hybrid truck consists of the hybrid drive unit at left, which combines a motor inverter/controller and manages power between the truck's 340 volt lithium-ion battery, right, and its 300 horsepower diesel engine. At speeds of 30 mph or lower and when idling, the truck runs on electricity.
Hybrid cars have been attracting drivers in search of greener and more economical transportation, and now it appears the hybrid vehicle is sparking some interest in Knoxville's market for large commercial trucks.
MHC Kenworth-Knoxville on Ault Road held an open house to show off a type of diesel/electric medium-duty truck it plans to stock, drawing a crowd of about 20-30 people representing several businesses and some local governments.
The 2009 Kenworth T270 truck, which combines a 300-horsepower engine with a 340-volt battery pack, is targeted to local businesses that have stop-and-go deliveries and utility companies and others that might need a vehicle to idle for considerable periods of time.
Walt Connors, new-truck sales manager for MHC Kenworth, said the selling price of the truck - $40,000-$50,000 - isn't cheap, but the 35 percent to 60 percent fuel savings it can provide will more than offset that cost to the owner. Plus, a $6,000-$12,000 federal tax credit is available for buying the hybrid vehicle, said Bud Lobetti, who will sell the trucks at MHC Kenworth.
Knox County Commissioner R. Larry Smith was among those who came out to see the vehicle.
"We were talking about this just yesterday in County Commission - trying to get hybrids in our fleet," Smith said. "We asked Bruce Wuethrich (Knox County director of engineering and public works) to look at his whole fleet and give us a report back - how many hybrids that we have and the potential for getting some more hybrids."
Gary Long, road superintendent for Anderson County, also was there. Asked his assessment of the vehicle for county use, Long said, "I don't know. With fuel costs increasing as they are, we'll just have to run the numbers and see."
He said, "Fuel affects a lot of things and if there is a savings in it we're interested."
Lobetti said the truck would not get maximum fuel savings on long-haul operations. It is designed to save fuel on short, within-town trips. During slow, stop-and-go traffic and when it is idling, the truck runs off of its battery, which is recharged through normal use of the truck's braking system.
MHC will carry two models: the T270, a class 6 truck rated for 25,000 pounds; and the T370, a class 7 truck rated for 33,000 pounds. They will be available in different configurations, such as one for hauling freight and a bucket-and-boom truck aimed at utility companies.
The T270 truck at MHC was a demonstration model making its way around the South, but Lobetti said the dealership plans to begin stocking the trucks as soon as it determines what configurations customers like best.
Though the T270s and T370s are for local use, a long-haul version is planned, said Mike Levering, Kenworth district sales manager.
"The T660 is in development right now and hopefully will be out by the end of the year," he said. "The T660 is the most aerodynamic truck that we have and that we feel is in the industry and we are going to combine it with hybrid power."
Gale Sams and Kevin Roach, fleet mechanics for Cherokee Distributing Co., looked over the T270 and asked Connors a few questions. Sams said the truck is something Cherokee Distributing would probably consider for its fleet. Fuel costs have been hitting hard, he said.
"We have probably six trucks that we don't even run on a Monday. Conserves fuel that way," Sams said.
Seattle City Light Energy Efficiency Programs help 93,000 residents cut bills with rebates, home energy audits, weatherization, conservation workshops, and sustainability tools, reducing electricity use and greenhouse gas emissions across Seattle communities.
Key Points
They are utility programs that lower electricity use and bills via rebates, energy audits, and weatherization services.
✅ Rebates for ENERGY STAR appliances and efficient HVAC upgrades
✅ Free audits with tailored recommendations and savings roadmaps
✅ Weatherization aid for low-income households and renters
In a noteworthy achievement for both residents and the environment, Seattle City Light has successfully helped more than 93,000 customers reduce their electricity bills through various energy efficiency programs. This initiative not only alleviates financial burdens for many households, amid concerns about pandemic-era shut-offs that heightened energy insecurity, but also aligns with the city’s commitment to sustainability and responsible energy use.
The Drive for Energy Efficiency
Seattle City Light, the city’s publicly owned electric utility, has been at the forefront of promoting energy efficiency among its customers. Recognizing that energy costs can strain household budgets, the utility has developed a range of programs and tracks emerging utility rate designs to help residents lower their energy consumption and, consequently, their bills.
One of the main aspects of this initiative is the emphasis on education and awareness. By providing customers with tools and resources to understand their energy usage, City Light empowers residents to make informed choices that can lead to substantial savings and prepare for power outage events as well.
Key Programs and Services
Seattle City Light offers a variety of programs aimed at reducing energy consumption. Among the most popular are:
Energy Efficiency Rebates: Customers can receive rebates for purchasing energy-efficient appliances, such as refrigerators, washing machines, and HVAC systems. These appliances are designed to consume less electricity than traditional models, resulting in lower energy bills over time.
Home Energy Audits: Free energy audits are available for residential customers. During these audits, trained professionals assess homes for energy efficiency and provide recommendations on improvements. This personalized service allows homeowners to understand specific changes that can lead to savings.
Weatherization Assistance: This program is particularly beneficial for low-income households. By improving insulation, sealing air leaks, and enhancing overall energy efficiency, residents can maintain comfortable indoor temperatures without over-relying on heating and cooling systems.
Community Workshops: Seattle City Light conducts workshops that educate residents about energy conservation strategies. These sessions cover topics such as smart energy use, seasonal tips for reducing consumption, and the benefits of renewable energy sources, highlighting examples of clean energy engagement in other cities.
The Impact on Households
The impact of these initiatives is profound. By assisting over 93,000 customers in lowering their electricity bills, Seattle City Light not only provides immediate financial relief but also encourages a long-term commitment to energy conservation. This collective effort has resulted in significant reductions in overall energy consumption, contributing to a decrease in greenhouse gas emissions—a critical step in the fight against climate change.
Additionally, the programs have been particularly beneficial for low-income households. By targeting these communities, Seattle City Light ensures that the benefits of energy efficiency reach those who need them the most, promoting equity-focused regulation and access to essential resources.
Looking Ahead: Challenges and Opportunities
While the success of these initiatives is commendable, challenges remain. Fluctuating energy prices can still pose difficulties for many households, especially those on fixed incomes, as some utilities explore minimum charges for low-usage customers in their rate structures. Seattle City Light recognizes the need for ongoing support and resources to help residents navigate these financial challenges.
The utility is committed to expanding its programs to reach even more customers in the future. This includes enhancing outreach efforts to ensure that residents are aware of the available resources, even as debates like utility revenue in a free-electricity future shape planning, and potentially forming partnerships with local organizations to broaden the impact of its initiatives.
Ontario EV Battery Storage ROI leverages V2B, V2G, two-way charging, demand response, and second-life batteries to monetize peak pricing, cut GHG emissions, and unlock up to $38,000 in lifetime value for commuters and buildings.
Key Points
The economic return from V2B/V2G two-way charging and second-life storage using EV batteries within Ontario's grid.
✅ Monetize peak pricing via workplace V2B discharging
✅ Earn up to $8,400 per EV over vehicle life
✅ Reduce gas generation and GHGs with demand response
The payback that usually comes to mind when people buy an electric vehicle is to drive an emissions-free, low-maintenance, better-performing mode of transportation.
On top of that, you can now add $38,000.
That, according to a new report from Ontario electric vehicle education and advocacy nonprofit, Plug‘n Drive, is the potential lifetime return for an electric car driven as a commuter vehicle while also being used as an electricity storage option amid an energy storage crunch in Ontario’s electricity system.
“EVs contain large batteries that store electric energy,” says the report. “Besides driving the car, [those] batteries have two other potentially useful applications: mobile storage via vehicle-to-grid while they are installed in the vehicle, and second-life storage after the vehicle batteries are retired.”
Pricing and demand differentials
The study, prepared by the research firm Strategic Policy Economics, modeled a two-stage scenario calculating the total benefits from both mobile and second-life storage when taking advantage of differences in daytime and nighttime electricity pricing and demand.
If done systematically and at scale, the combined benefits to EV owners, building operators and the electricity system in Ontario could reach $129 million per year by 2035, according to the report. Along with the financial gains, the province would also cut GHG emissions by up to 67.2 kilotons annually.
The math might sound complicated, but the concepts are simple. All it requires is for drivers to charge their batteries with low-cost electricity overnight at home, then plug them into two-way EV charging stations at work and discharge their stored electricity for use by the building by day when buying power from the grid is more expensive.
“Workplace buildings could avoid high daytime prices by purchasing electricity from EVs parked onsite and enjoy savings as a result,” says the report.
Based on average commuting distances, EVs in this scenario could make half their storage capacity available for discharge. Drivers would be paid out of the building’s savings, effectively selling electricity back to the grid and earning up to $8,400 over the life of their vehicle.
According to the report, Ontario could have as many as 18,555 vehicles participating in mobile storage by 2030. At this level, the daily electricity demand would be reduced by 565 MWh. This, in turn, would reduce demand for natural gas-fired electricity generation, a fossil-fuel electricity source, avoiding the expense of gas purchases while reducing GHG emissions.
The second-life storage opportunity begins when the vehicle lifespan ends. “EV batteries will still have over 80% of their storage capacity after being driven for 13 years and providing mobile storage,” the report states. “Those-second life batteries could provide a low-cost energy storage solution for the electricity grid and enhance grid stability over time.”
Some of the savings could be shared with EV owners in the form of a rebate worth up to 20 per cent of the batteries’ initial cost.
Call to action
The report concludes with a call to action for EV advocates to press policy makers and other stakeholders to take actions on building codes, the federal Clean Fuel Standard and other business models in order to maximize the benefits of using EV batteries for the electricity system in this way, even as growing adoption could challenge power grids in some regions.
“EVs are often approached as an environmental solution to climate change,” says Cara Clairman, Plug’n Drive president and CEO. “While this is true, there are significant economic opportunities that are often overlooked.”
Bitcoin Energy Consumption drives debate on blockchain mining, proof-of-work, carbon footprint, and emissions, with CCAF estimates in terawatt hours highlighting electricity demand, fossil fuel reliance, and sustainability concerns for data centers and cryptocurrency networks.
Key Points
Electricity used by Bitcoin proof-of-work mining, often fossil-fueled, estimated by CCAF in terawatt hours.
✅ CCAF: 40-445 TWh, central estimate ~130 TWh
✅ ~66% of mining electricity sourced from fossil fuels
✅ Proof-of-work increases hash rate, energy, and emissions
The University of Cambridge Centre for Alternative Finance (CCAF) studies the burgeoning business of cryptocurrencies.
It calculates that Bitcoin's total energy consumption is somewhere between 40 and 445 annualised terawatt hours (TWh), with a central estimate of about 130 terawatt hours.
The UK's electricity consumption is a little over 300 TWh a year, while Argentina uses around the same amount of power as the CCAF's best guess for Bitcoin, as countries like New Zealand's electricity future are debated to balance demand.
And the electricity the Bitcoin miners use overwhelmingly comes from polluting sources, with the U.S. grid not 100% renewable underscoring broader energy mix challenges worldwide.
The CCAF team surveys the people who manage the Bitcoin network around the world on their energy use and found that about two-thirds of it is from fossil fuels, and some regions are weighing curbs like Russia's proposed mining ban amid electricity deficits.
Huge computing power - and therefore energy use - is built into the way the blockchain technology that underpins the cryptocurrency has been designed.
It relies on a vast decentralised network of computers.
These are the so-called Bitcoin "miners" who enable new Bitcoins to be created, but also independently verify and record every transaction made in the currency.
In fact, the Bitcoins are the reward miners get for maintaining this record accurately.
It works like a lottery that runs every 10 minutes, explains Gina Pieters, an economics professor at the University of Chicago and a research fellow with the CCAF team.
Data processing centres around the world, including hotspots such as Iceland's mining strain, race to compile and submit this record of transactions in a way that is acceptable to the system.
They also have to guess a random number.
The first to submit the record and the correct number wins the prize - this becomes the next block in the blockchain.
Estimates for bitcoin's electricity consumption At the moment, they are rewarded with six-and-a-quarter Bitcoins, valued at about $50,000 each.
As soon as one lottery is over, a new number is generated, and the whole process starts again.
The higher the price, says Prof Pieters, the more miners want to get into the game, and utilities like BC Hydro suspending new crypto connections highlight grid pressures.
"They want to get that revenue," she tells me, "and that's what's going to encourage them to introduce more and more powerful machines in order to guess this random number, and therefore you will see an increase in energy consumption," she says.
And there is another factor that drives Bitcoin's increasing energy consumption.
The software ensures it always takes 10 minutes for the puzzle to be solved, so if the number of miners is increasing, the puzzle gets harder and the more computing power needs to be thrown at it.
Bitcoin is therefore actually designed to encourage increased computing effort.
The idea is that the more computers that compete to maintain the blockchain, the safer it becomes, because anyone who might want to try and undermine the currency must control and operate at least as much computing power as the rest of the miners put together.
What this means is that, as Bitcoin gets more valuable, the computing effort expended on creating and maintaining it - and therefore the energy consumed - inevitably increases.
We can track how much effort miners are making to create the currency.
They are currently reckoned to be making 160 quintillion calculations every second - that's 160,000,000,000,000,000,000, in case you were wondering.
And this vast computational effort is the cryptocurrency's Achilles heel, says Alex de Vries, the founder of the Digiconomist website and an expert on Bitcoin.
All the millions of trillions of calculations it takes to keep the system running aren't really doing any useful work.
"They're computations that serve no other purpose," says de Vries, "they're just immediately discarded again. Right now we're using a whole lot of energy to produce those calculations, but also the majority of that is sourced from fossil energy, and clean energy's 'dirty secret' complicates substitution."
The vast effort it requires also makes Bitcoin inherently difficult to scale, he argues.
"If Bitcoin were to be adopted as a global reserve currency," he speculates, "the Bitcoin price will probably be in the millions, and those miners will have more money than the entire [US] Federal budget to spend on electricity."
"We'd have to double our global energy production," he says with a laugh, even as some argue cheap abundant electricity is getting closer to reality today. "For Bitcoin."
He says it also limits the number of transactions the system can process to about five per second.
This doesn't make for a useful currency, he argues.
Rising price of bitcoin graphic And that view is echoed by many eminent figures in finance and economics.
The two essential features of a successful currency are that it is an effective form of exchange and a stable store of value, says Ken Rogoff, a professor of economics at Harvard University in Cambridge, Massachusetts, and a former chief economist at the International Monetary Fund (IMF).
He says Bitcoin is neither.
"The fact is, it's not really used much in the legal economy now. Yes, one rich person sells it to another, but that's not a final use. And without that it really doesn't have a long-term future."
What he is saying is that Bitcoin exists almost exclusively as a vehicle for speculation.
Ontario IESO COVID-19 Control Room Measures detail how essential operators safeguard the electricity grid with split shifts, backup control centres, real-time balancing, deep cleaning, social distancing, and shelter-in-place readiness to maintain reliable power.
Key Points
Measures that protect essential grid operators with split shifts, backup sites, and hygiene to keep power reliable.
✅ Split teams across primary and backup control centres
✅ 12-hour shifts with remote handoffs and deep cleaning
✅ Real-time grid modeling to balance demand and supply
A group of personnel key to keeping Ontario's electricity system functioning may end up locked down in their control centres due to the COVID-19 crisis, according to the head of the province's power operator.
But that has so far proven unnecessary with a change-up in routine, Independent Electricity System Operator CEO Peter Gregg said.
While about 90 per cent of staff were sent to work from home on March 13, another 48 control-room operators deemed essential are still going into work, Gregg said in an interview.
"We identified a smaller cohort of critical operations room staff that need to go in to operate the system out of our control centres," Gregg said. "My biggest concern is to maintain their health, their safety as we rely on them to do this critical work."
Some of the operators manage power demand and supply in real time as Ontario electricity demand shifts, by calling for more or less generation and keeping an eye on the distribution grid, which also allows power to flow to and from Ontario's neighbours. Others do scenario planning and modelling to prepare for changes.
The essential operators have been split into eight teams of six each working 12-hour shifts. The day crew works out of a control centre near Toronto and the night shift out of a backup centre in the city's west end, Gregg said.
"That means that we're not having physical hand-off between control room operators on shift change -- we can do it remotely -- and it also allows us to do deep cleansing," Gregg said. "We're fortunate that the way the room is set up allows us to practice good social distancing."
Should it become necessary, he said, bed, food and other on-site arrangements have been made to allow the operators to stay at their workplaces as a similar agency in New York has done.
"If we do need to shelter these critical employees in place, we've got the ability to do so."
IESO is responsible for ensuring a balance between supply and demand for electricity across the province. Because power cannot be stored, the IESO ensures generators produce enough power to meet peak demand while making sure they don't produce too much.
"You're seeing, obviously, commercial demand drop, some industrial demand drop," Gregg said. "But you're also seeing a shift in the demand curve as well, where normally you have people heading off to work and so residential demand would go down. But obviously with them staying home, you're seeing an increase in residential electricity use across the province."
Some utilities have indicated no cuts to peak rates for self-isolating customers, with Hydro One peak pricing remaining in place for now.
IESO also runs and settles the wholesale electricity markets. Market prices are set based on accepted offers to supply electricity, while programs supporting stable electricity pricing for industrial and commercial users can affect costs against forecast demand.
With the pandemic forcing many businesses to close and people to stay home, and provincial electricity relief for families and small businesses in place, typical power needs fallen about seven per cent at a time of year that would normally see demand soften anyway. It remains to be seen whether, and how much, power needs shift further amid stringent isolation measures and the ongoing economic impact of the outbreak.
Gregg said the operator is constantly modeling different possibilities.
"What we do normally is prepare for all of these sort of emergency scenarios, as reflected in the U.S. grid response coverage, and test and drill for these," he said. "What we're experiencing over the last few weeks is that those drills come in handy because they help us prepare for when the real-time situation actually happens."
U.S. Majority Renewables by 2030 targets over half of electricity from wind, solar, hydropower, and energy storage, enabling a resilient, efficient grid, deep carbon reductions, fair market rules, and job growth across regions.
Key Points
A joint industry pledge for over 50% U.S. power from wind, solar, hydropower, and storage by 2030.
✅ Joint pledge by AWEA, SEIA, NHA, and ESA for a cleaner grid
✅ Focus on resilience, efficiency, affordability, and fair competition
✅ Storage enables flexibility to integrate variable renewables
Within a decade, more than half of the electricity generated in the U.S. will come from clean, renewable resources, with analyses indicating that wind and solar could meet 80% of U.S. electricity demand, supported by energy storage, according to a joint commitment today from the American wind, solar, hydropower, and energy storage industries. The American Wind Energy Association (AWEA), Solar Energy Industries Association (SEIA), National Hydropower Association (NHA), and Energy Storage Association (ESA) have agreed to actively collaborate across their industry segments to achieve this target.
The four industries have released a set of joint advocacy principles that will enable them to realize this bold vision of a majority renewables grid. Along with increased collaboration, these shared principles include building a more resilient, efficient, sustainable, and affordable grid; achieving carbon reductions; and advancing greater competition through electricity market reforms and fair market rules. Each of these areas is critical to attaining the shared vision for 2030.
The leaders of the four industry associations gathered to announce the shared vision, aligned with a broader 100% renewables pathway pursued nationwide, during the first CLEANPOWER annual conference for businesses across the renewable and clean energy spectrum.
American Wind Energy Association
"This collaborative promise sets the stage to deliver on the American electric grid of the future powered by wind, solar, hydropower, and storage," said Tom Kiernan, CEO of the American Wind Energy Association. "Market opportunities for projects that include a mix of technologies have opened up that didn't exist even a few years ago. And demand is growing for integrated renewable energy options. Individually and cooperatively, these sectors will continue growing to meet that demand and create hundreds of thousands of new jobs to strengthen economies from coast to coast, building a better, cleaner tomorrow. In the face of significant challenges the country is currently facing across pandemic response, economic, climate and social injustice problems, we are prepared to help lead toward a healthier and more equitable future."
Solar Energy Industries Association
"These principles are just another step toward realizing our vision for a Solar+ Decade," said Abigail Ross Hopper, president and CEO of the Solar Energy Industries Association. "In the face of this dreadful pandemic, our nation must chart a path forward that puts a premium on innovation, jobs recovery and a smarter approach to energy generation, reflecting expected solar and storage growth across the market. The right policies will make a growing American economy fueled by clean energy a reality for all Americans."
National Hydropower Association
"The path towards an affordable, reliable, carbon-free electricity grid, supported by an ongoing grid overhaul for renewables, starts by harnessing the immense potential of hydropower, wind, solar and storage to work together," said Malcolm Woolf, President and CEO of the National Hydropower Association. "Today, hydropower and pumped storage are force multipliers that provide the grid with the flexibility needed to integrate other renewables onto the grid. By adding new generation onto existing non-powered dams and developing 15 GW of new pumped storage hydropower capacity, we can help accelerate the development of a clean energy electricity grid."
Energy Storage Association
"We are pleased to join forces with our clean energy friends to substantially reduce carbon emissions by 2030, guided by practical decarbonization strategies, building a more resilient, efficient, sustainable, and affordable grid for generations to come," said ESA CEO Kelly Speakes-Backman. "A majority of generation supplied by renewable energy represents a significant change in the way we operate the grid, and the storage industry is a fundamental asset to provide the flexibility that a more modern, decarbonized grid will require. We look forward to actively collaborating with our colleagues to make this vision a reality by 2030."
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.
