According to the latest “Monthly Energy Review” issued by the U.S. Energy Information Administration on Sept. 24, renewable energy accounted for more than 10 percent of the domestically-produced energy used in the United States in the first half of 2008.
Through June 30, the United States consumed 50.673 quadrillion Btu (quads) of energy — of which 34.162 quads were from domestic sources and 16.511 quads were imported.
Domestically-produced renewable energy (biomass/biofuels, geothermal, hydropower, solar, wind) totaled 3.606 quads — an amount equal to 10.56 percent of U.S. energy consumption that is domestically-produced. This share is only slightly less than the contribution from nuclear power (11.98 percent).
And while consumption of nuclear power dropped by 1 percent during the first half of 2008, compared to the same period for 2007 (4.091 quads, down from 4.119 quads), renewable energyÂ’s share increased by 5 percent (3.606 quads, up from 3.439 quads).
Biomass and biofuels combined presently constitute the largest source of renewable energy in the United States (1.883 quads) followed by hydropower (1.387 quads).
Wind power experienced the largest growth rate — increasing by almost 49 percent from the first half of 2007 compared to the first half of 2008 (0.244 quad, up from 0.164 quad).
Solar and geothermal contributions were at roughly the same levels in 2008 as they were in 2007. However, both are poised to greatly expand their market share in the near future.
“The significant contribution being made by renewable energy sources to the nation’s energy supply documented by the U.S. Energy Information Administration (EIA) is far greater than most Americans realize,” said Ken Bossong, executive director of the Sun Day Campaign, a non-profit research and educational organization founded in 1993 to promote sustainable energy technologies as cost-effective alternatives to nuclear power and fossil fuels.
“Repeated statements by nuclear and fossil fuel interests that renewables contribute only a tiny fraction of the nation’s energy supply are not only misleading but flatly wrong.”
Maryland Renewable Energy Violations highlight RPS compliance gaps as facilities selling renewable energy certificates, including waste-to-energy, biomass, and paper mills, face emissions and permit issues, prompting PSC and Attorney General scrutiny of environmental standards.
Key Points
Alleged RPS noncompliance by REC-eligible plants, prompting PSC review and potential decertification under Maryland law.
✅ Complaint targets waste-to-energy, biomass plants, and paper mills
✅ Facilities risk loss of REC certification for environmental violations
✅ PSC may investigate nonreporting; AG reviewing evidence
Many facilities that supply Maryland with renewable energy have exceeded pollution limits or otherwise broken environmental rules, violating a state law, according to a complaint sent by environmental groups to state energy and law enforcement officials.
Maryland law says that any company that contributes to a state renewable energy goal — half the state’s energy portfolio must come from renewable sources by 2030 — must “substantially comply” with rules on air and water quality and waste management. The complaint says more than two dozen power generators, including paper mills and trash incinerators, have records of formal or informal enforcement actions by environmental authorities.
For years, environmental groups have criticized Maryland policy that counts power plants that produce planet-warming carbon dioxide and health-threatening pollution as “renewable” energy generation, and similar tensions have emerged in California’s reliance on fossil fuels despite ambitious targets, but lawmakers concerned about protecting industrial jobs have resisted reforms. The renewable label qualifies the companies for subsidies drawn from energy bills across the state.
In a complaint filed this week, the groups asked the attorney general and Public Service Commission to step in.
“We’re subsidizing companies to produce dirty energy, but we’re also using ratepayer money to support companies that in many instances are paying environmental fines or just flouting the law,” said Timothy Whitehouse, executive director of Public Employees for Environmental Responsibility. “There’s no one to hold them to account in Maryland.”
A spokeswoman for Attorney General Brian Frosh said his office would review the complaint, which was signed by Whitehouse and Mike Ewall, executive director of the Energy Justice Network.
Public Service Commission officials said the facilities must notify them if found out of compliance with environmental rules, while at the federal level FERC action on aggregated DERs is shaping market participation, and the commission can then revoke certification under the state renewable energy program. In a statement, commission officials said they would launch an investigation if any facility had failed to notify them of any environmental violations, and encouraged anyone with evidence of such a transgression to file a complaint.
Companies named in the document accused the groups of painting an inaccurate picture.
“This complaint is based on misleading arguments designed to halt waste-to-energy practices that have clear environmental benefits recognized by the global scientific community,” said Jim Connolly, vice president of environment, health and safety for Wheelabrator, which owns a Baltimore trash incinerator.
Maryland launched its renewable energy program in 2004, diversifying the state’s energy portfolio with more environmentally friendly sources of power, even as regional debates over a Maine-Québec transmission line highlight cross-border impacts. Under the program, separate from the electricity they generate and sell to the grid, renewable power facilities can sell what are known as renewable energy certificates. Utilities such as Baltimore Gas and Electric Co. are required to buy a growing number of the certificates each year, essentially subsidizing the renewable energy facilities with money from ratepayer bills.
A dozen types of power generation qualify to sell the certificates: Solar, wind, geothermal and hydroelectric plants, as well as “biomass” facilities that burn wood and other organic matter, waste-to-energy plants that burn household trash and paper mills that burn a byproduct known as black liquor.
The complaint focuses on waste incinerators, biomass plants and paper mills, all of which environmental groups have cast as counter to the renewable energy program’s environmental goals, even as ACORE criticized a coal and nuclear subsidy proposal in federal proceedings.
“By subsidizing these corporations, Maryland is diverting the hard-earned income of Maryland ratepayers to wealthy corporations with poor environmental compliance records and undermining the state’s transition to clean renewable energy,” Whitehouse and Ewall wrote.
For example, they note that the Wheelabrator plant in Southwest Baltimore has been fined for exceeding mercury limits in the past. That occurred in 2011, when the plant settled with state regulators for violations in 2010 and 2009.
Connolly said there is “no question” the facility complies with Maryland’s renewable energy law.
Incinerators in Montgomery County and in Fairfax County, Virginia, that are owned by Covanta and sell the energy certificates in Maryland have been cited for accidental fires inside both facilities. The Maryland incinerator violated emissions rules in 2014, the same year that New Jersey forbade the Virginia facility from selling energy certificates into that state’s renewable energy program over concerns it wasn’t following ash testing regulations.
James Regan, a spokesman for Covanta, said both facilities “have excellent compliance records and they operate well below their permitted limits.” He said the Virginia facility is complying with ash testing requirements, and that both facilities emit far lower levels of pollutants such as particulate matter than vehicles do.
“It’s clear to us there’s a lot of misleading and wrong information in this document," Regan said.
The Environmental Protection Agency endorsed waste-to-energy facilities under former President Barack Obama because, while burning household trash emits carbon dioxide, scientists said that still had a smaller impact on global warming than sending trash to landfills, even as industry groups have backed the EPA in a legal challenge to the ACE rule as regulatory approaches shifted.
Environmentalists and community groups say the facilities still are harmful because they emit high levels of pollutants such as mercury, nitrogen oxides and lead. The concerns prompted Baltimore City Council to pass an ordinance in February that tightened emissions limits on the Wheelabrator facility, even as the new EPA pollution limits for coal and gas plants are being proposed, so dramatically that the company said it would no longer be able to operate once the rules go into effect in 2022.
The complaint does not mention the century-old Luke paper mill in Western Maryland that long faced criticism for its participation in the renewable energy program, but which owner Verso Co. closed this year.
It does say several of paper company WestRock’s mills in North Carolina and Virginia have faced both formal and informal EPA enforcement actions for violation of the Clean Water Act, including evolving EPA wastewater limits for power plants and other facilities, and the Clean Air Act. A WestRock spokesperson could not be reached for comment.
The complaint also says a large biomass facility in South Boston, Virginia, owned by the Northern Virginia Electric Cooperative has a record of noncompliance with the Clean Air Act over three years.
John Rainey, the plant’s operations director, said it “experienced some small exceedances to its permit limits,” but that it addressed the issues with Virginia environmental officials and has installed new technology.
All those plants have sold credits in Maryland.
Whitehouse said the environmental groups’ goal is to clean up Maryland’s renewable energy program. They did not file a lawsuit because he said there was no clear cause of action to take the state to court, but said he hopes the complaint nonetheless spurs action.
“It’s not acceptable in a clean energy program that we’re subsidizing some of the most dirty sources of energy,” he said. “Those sources aren’t even in compliance with the law, and no one seems to care.”
Rising Greenhouse Gas Concentrations drive climate change, with CO2, methane, and nitrous oxide surging; WMO data show higher radiative forcing, elevated pre-industrial baselines, and persistent atmospheric concentrations despite Paris Agreement emissions pledges.
Key Points
Increasing atmospheric CO2, methane, and nitrous oxide levels that raise radiative forcing and drive warming.
✅ WMO data show CO2 at 407.8 ppm in 2018, above decade average
✅ Methane and nitrous oxide surged, elevating total radiative forcing
✅ Concentrations differ from emissions; sinks absorb about half
The World Meteorological Organization (WMO) says the increase in CO2 was just above the average rise recorded over the last decade.
Levels of other warming gases, such as methane and nitrous oxide, have also surged by above average amounts.
Since 1990 there's been an increase of 43% in the warming effect on the climate of long lived greenhouse gases.
The WMO report looks at concentrations of warming gases in the atmosphere rather than just emissions.
The difference between the two is that emissions refer to the amount of gases that go up into the atmosphere from the use of fossil fuels, such as burning coal for coal-fired electricity generation and from deforestation.
Concentrations are what's left in the air after a complex series of interactions between the atmosphere, the oceans, the forests and the land. About a quarter of all carbon emissions are absorbed by the seas, and a similar amount by land and trees, while technologies like carbon capture are being explored to remove CO2.
Using data from monitoring stations in the Arctic and all over the world, researchers say that in 2018 concentrations of CO2 reached 407.8 parts per million (ppm), up from 405.5ppm a year previously.
This increase was above the average for the last 10 years and is 147% of the "pre-industrial" level in 1750.
The WMO also records concentrations of other warming gases, including methane and nitrous oxide, and some countries have reported declines in certain potent gases, as noted in US greenhouse gas controls reports, though global levels remain elevated. About 40% of the methane emitted into the air comes from natural sources, such as wetlands, with 60% from human activities, including cattle farming, rice cultivation and landfill dumps.
Methane is now at 259% of the pre-industrial level and the increase seen over the past year was higher than both the previous annual rate and the average over the past 10 years.
Nitrous oxide is emitted from natural and human sources, including from the oceans and from fertiliser-use in farming. According to the WMO, it is now at 123% of the levels that existed in 1750.
Last year's increase in concentrations of the gas, which can also harm the ozone layer, was bigger than the previous 12 months and higher than the average of the past decade.
What concerns scientists is the overall warming impact of all these increasing concentrations. Known as total radiative forcing, this effect has increased by 43% since 1990, and is not showing any indication of stopping.
There is no sign of a slowdown, let alone a decline, in greenhouse gases concentration in the atmosphere despite all the commitments under the Paris agreement on climate change and the ongoing global energy transition efforts," said WMO Secretary-General Petteri Taalas.
"We need to translate the commitments into action and increase the level of ambition for the sake of the future welfare of mankind," he added.
"It is worth recalling that the last time the Earth experienced a comparable concentration of CO2 was three to five million years ago. Back then, the temperature was 2-3C warmer, sea level was 10-20m higher than now," said Mr Taalas.
The UN Environment Programme will report shortly on the gap between what actions countries are taking to cut carbon, for example where Australia's emissions rose 2% recently, and what needs to be done to keep under the temperature targets agreed in the Paris climate pact.
Preliminary findings from this study, published during the UN Secretary General's special climate summit last September, indicated that emissions continued to rise during 2018, although global emissions flatlined in 2019 according to the IEA.
Both reports will help inform delegates from almost 200 countries who will meet in Madrid next week for COP25, following COP24 in Katowice the previous year, the annual round of international climate talks.
Asia Electricity Consumption 2025 highlights an IEA forecast of surging global power demand led by China, lagging access in Africa, rising renewables and nuclear output, stable emissions, and weather-dependent grids needing flexibility and electrification.
Key Points
An IEA forecast that Asia will use half of global power by 2025, led by China, as renewables and nuclear drive supply.
✅ Asia to use half of global electricity; China leads growth
✅ Africa just 3% consumption despite rapid population growth
✅ Renewables, nuclear expand; grids must boost flexibility
Asia will for the first time use half of the world’s electricity by 2025, even as global power demand keeps rising and Africa continues to consume far less than its share of the global population, according to a new forecast released Wednesday by the International Energy Agency.
Much of Asia’s electricity use will be in China, a nation of 1.4 billion people whose China's electricity sector is seeing shifts as its share of global consumption will rise from a quarter in 2015 to a third by the middle of this decade, the Paris-based body said.
“China will be consuming more electricity than the European Union, United States and India combined,” said Keisuke Sadamori, the IEA’s director of energy markets and security.
By contrast, Africa — home to almost a fifth of world’s nearly 8 billion inhabitants — will account for just 3% of global electricity consumption in 2025.
“This and the rapidly growing population mean there is still a massive need for increased electrification in Africa,” said Sadamori.
The IEA’s annual report predicts that low-emissions sources will account for much of the growth in global electricity supply over the coming three years, including nuclear power and renewables such as wind and solar. This will prevent a significant rise in greenhouse gas emissions from the power sector, it said.
Scientists say sharp cuts in all sources of emissions are needed as soon as possible to keep average global temperatures from rising 1.5 degrees Celsius (2.7 Fahrenheit) above pre-industrial levels. That target, laid down in the 2015 Paris climate accord, appears increasingly doubtful as temperatures have already increased by more than 1.1 C since the reference period.
One hope for meeting the goal is a wholesale shift away from fossil fuels such as coal, gas and oil toward low-carbon sources of energy. But while some regions are reducing their use of coal and gas for electricity production, in others, soaring electricity and coal use are increasing, the IEA said.
The 134-page also report warned that surging electricity demand and supply are becoming increasingly weather dependent, a problem it urged policymakers to address.
“In addition to drought in Europe, there were heat waves in India (last year),” said Sadamori. “Similarly, central and eastern China were hit by heatwaves and drought. The United States, where electricity sales projections continue to fall, also saw severe winter storms in December, and all those events put massive strain on the power systems of these regions.”
“As the clean energy transition gathers pace, the impact of weather events on electricity demand will intensify due to the increased electrification of heating, while the share of weather-dependent renewables poised to eclipse coal will continue to grow in the generation mix,” the IEA said. “In such a world, increasing the flexibility of power systems while ensuring security of supply and resilience of networks will be crucial.”
OPG-TVA SMR Partnership advances advanced nuclear technology and small modular reactors for 24/7 carbon-free baseload power, enabling net-zero goals, cross-border licensing, and deployment within a North American clean energy hub.
Key Points
A cross-border effort by OPG and TVA to develop, license, and deploy SMRs for reliable, carbon-free baseload power.
✅ Coordinates design, licensing, construction, and operations
✅ Supports 24/7 baseload, net-zero targets, and energy security
✅ Leverages Darlington and Clinch River early site permits
Two of North America's leading nuclear utilities unveiled a pioneering partnership to develop advanced nuclear technology as an integral part of a clean energy future and creating a North American energy hub. Ontario Power Generation, whose OPG's SMR commitment is well established, and the Tennessee Valley Authority will jointly work to help develop small modular reactors as an effective long-term source of 24/7 carbon-free energy in both Canada and the U.S.
The agreement allows the companies to coordinate their explorations into the design, licensing, construction and operation of small modular reactors.
"As leaders in our industry and nations, OPG and TVA share a common goal to decarbonize energy generation while maintaining reliability and low-cost service, which our customers expect and deserve," said Jeff Lyash, TVA President and CEO. "Advanced nuclear technology will not only help us meet our net-zero carbon targets but will also advance North American energy security."
"Nuclear energy has long been key to Ontario's clean electricity grid, and is a crucial part of our net-zero future," said Ken Hartwick, OPG President and CEO. "Working together, OPG and TVA will find efficiencies and share best practices for the long-term supply of the economical, carbon-free, reliable electricity our jurisdictions need, supported by ongoing Pickering life extensions across Ontario's fleet."
OPG and TVA have similar histories and missions. Both are based on public power models that developed from renewable hydroelectric generation before adding nuclear to their generation mixes. Today, nuclear generation accounts for significant portions of their carbon-free energy portfolios, with Ontario advancing the Pickering B refurbishment to sustain capacity.
Both are also actively exploring SMR technologies. OPG is moving forward with plans to deploy an SMR at its Darlington nuclear facility in Clarington, ON, as part of broader Darlington SMR plans now underway. The Darlington site is the only location in Canada licensed for new nuclear with a completed and accepted Environmental Assessment. TVA currently holds the only Nuclear Regulatory Commission Early Site Permit in the U.S. for small modular reactor deployment at its Clinch River site near Oak Ridge, TN.
No exchange of funding is involved. However, the collaboration agreement will help OPG and TVA reduce the financial risk that comes from development of innovative technology, as well as future deployment costs.
"TVA has the most recent experience completing a new nuclear plant in North America at Watts Bar and that knowledge is invaluable to us as we work toward the first SMR groundbreaking at Darlington," said Hartwick. "Likewise, because we are a little further along in our construction timing, TVA will gain the advantage of our experience before they start work at Clinch River."
"It's a win-win agreement that benefits all of those served by both OPG and TVA, as well as our nations," said Lyash. "Moving this technology forward is not only a significant step in advancing a clean energy future and Canada's climate goals, but also in creating a North American energy hub."
"With the demand for clean electricity on the rise around the world, Ontario's momentum is growing. The world is watching Ontario as we advance our work to fully unleash our nuclear advantage, alongside a premiers' SMR initiative that underscores provincial collaboration. I congratulate OPG and TVA – two great industry leaders – for working together to deploy SMRs and showcase and apply Canada's nuclear expertise that will deliver economic, health and environmental benefits for all of us to enjoy," said Todd Smith,Ontario Minister of Energy.
"The changing climate is a global crisis that requires global solutions. The partnership between the Tennessee Valley Authority and Ontario Power Generation to develop and deploy advanced nuclear technology is exactly the kind of innovative collaboration that is needed to quickly bring the next generation of nuclear carbon-free generation to market. I applaud the leadership that both companies are demonstrating to further strengthen our cross-border relationships," said Maria Korsnick, President and CEO, Nuclear Energy Institute.
UK Electricity Interconnectors secure capacity market subsidies, supporting winter reliability with seabed cables to France and Belgium via the Channel Tunnel, lowering consumer costs, squeezing coal, and challenging new gas plants through cross-border energy trading.
Key Points
High-voltage cables linking Britain to Europe, securing backup capacity, cutting costs and boosting winter reliability.
✅ Won capacity market contracts at record-low prices
✅ Cables to France and Belgium via Channel Tunnel, seabed routes
✅ Squeezes coal, challenges new gas; renewables may join market
New electricity cables across the Channel to France and Belgium will be a key part of keeping Britain’s lights on during winter amid record electricity prices across Europe in the early 2020s, after their owners won backup power subsidies in a government auction this week.
For the first time, interconnector operators successfully bid for a slice of hundreds of millions’ worth of contracts in the capacity market. That will help cut costs for consumers, given how electricity is priced in Europe today, and squeeze out old coal power plants.
Three new interconnectors are currently being built to Europe, almost doubling existing capacity, with one along the Channel Tunnel and two on the seabed: one between Kent and Zeebrugge and one from Hampshire to Normandy.
The interconnectors were success stories in this week’s capacity auction, which saw power firms bid to provide backup electricity in the winter of 2021/22. Prices for the four-year contracts hit a record low of £8.40 per kilowatt per year, which analysts described as a shock and well below expectations.
One industry source said the figure was “miles away” from what is needed to encourage companies to build big new gas power stations, which some argue are necessary to fill the gap when the UK’s ageing nuclear reactors close as Europe loses nuclear power across the region over the next decade.
While bad news for those firms, the low price is good for consumers. The subsidies will add about £525m to energy bills, or £5.68 for the average household, compared with £11 for the year before, according to analysts Cornwall Insight.
Existing gas power stations scooped up most of the contracts, but new gas ones lost out, as did several coal plants. Battery storage plants, a standout success in the last auction, fared comparatively poorly after changes to the rules.
Experts at Bernstein bank said the the misses by coal meant that around half the UK’s remaining coal power capacity could close from October 2019, when existing capacity market contracts run out. Chaitanya Kumar, policy adviser at thinktank Green Alliance, said: “Coal’s exit from the UK’s energy system just moved a step closer as coal contracts fell by half compared with last year.”
Tom Edwards, an analyst at Cornwall Insight, said that more interconnectors were likely to bid into future rounds of the capacity market, such as the cable being laid between Norway and the UK. Relying on foreign power supplies was fine, he said, provided Brexit did not make energy trading more difficult and the interconnectors delivered at times of need, where events like Irish grid price spikes illustrate the stress points.
However, one industry source, who wants to see new gas plants built in the UK, said the results showed that the system was not working, amid UK peak power prices that have climbed in recent trading. “That self-sufficiency doesn’t seem to be a priority at a time when we’re breaking away from Europe is a bit weird,” they said.
But the prospects for new gas plants in future rounds of the capacity market look bleak. They will very likely face a new source of competition next year, if energy regulator Ofgem approves a proposal to allow renewables to compete too.
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.
Whether you would prefer Live Online or In-Person
instruction, our electrical training courses can be
tailored to meet your company's specific requirements
and delivered to your employees in one location or at
various locations.
