OptiSolar, Inc. headquartered in Hayward, Calif. is taking advantage of the $20 million incentive offered by the County of Sacramento to located its 600,000 square foot solar plant in McClellan Park which is an industrial party once home to an Air Force Base.
The photo-voltaic panel plant will generated $26 million in taxes according to a report in the Sacramento Bee. The deal, lasting 25 years, rebates the company 50% of its electricity user tax and 80% of future property tax increases.
ABO Wind Tunisia 10MW Solar Project will build a photovoltaic park in Gabes with a STEG PPA, fixed tariff, 2,500 m grid connection, producing 18 million kWh annually, targeted for 2020 commissioning with local partners.
Key Points
A 10MW photovoltaic park in Gabes with a 20-year STEG PPA and fixed tariff, slated for 2020 commissioning.
✅ 18 million kWh/year; 2,500 m grid tie, 20-year fixed tariff
✅ Electricity supplied to STEG under PPA; 2020 commissioning
✅ Located in Gabes; built with local partners, 10MW capacity
ABO Wind has received a permit and a tariff for a 10MW photovoltaic project in Tunisia, amid global activity such as Spain's 90MW wind project now underway, which it plans to build and commission in 2020.
The solar park, in the governorate of Gabes, is 400km south of the country’s capital Tunis and aligns with renewable funding initiatives seen across developing markets.
The developer said it plans to build the project next year in close cooperation with local partners, as regional markets from North Africa to the Gulf expand, with Saudi Arabia boosting wind capacity as well.
ABO Wind department head Nicolas Konig said: “The solar park will produce more than 18 million kilowatt hours of electricity per year and will feed it into the grid at a distance of 2500 metres.”
The developer will conclude an electricity supply contract with the state-owned energy supplier (Societe tunisienne de l’electricite et du gaz (STEG), which will provide a fixed remuneration over 20 years, a model echoed by Germany's wind-solar tender for the electricity fed into the grid.
Earlier this year, ABO Wind had already secured a tariff for a wind farm with a capacity of 30MW in a tender, 35km south-east of Tunis, underscoring Tunisia's wind investments under its long-term plan.
The company is working on half a dozen Tunisian wind and solar projects, as institutions like the World Bank support wind growth in developing countries.
“We are making good progress on our way to assemble a portfolio of several ready-to-build wind and solar projects attractive to investors, as Saudi clean energy targets continue to expand globally,” said ABO Wind general manager responsible for international business development Patrik Fischer.
Hydro-Québec Northeast Clean Energy Transmission delivers surplus hydropower via HVDC interconnections to New York and New England, leveraging long-term contracts and projects like CHPE and NECEC to support carbon-free goals, GHG cuts, and grid reliability.
Key Points
An initiative to expand HVDC links for Quebec hydropower exports, aiding New York and New England decarbonization.
✅ Targets NY and NE via CHPE, NECEC, and upgraded interfaces
✅ Backed by long-term PPAs to reduce merchant transmission risk
With roughly 37,000 MW of installed hydro power capacity, Quebec has ample spare capacity that it would like to deliver into Northeastern US markets where ambitious clean energy goals have been announced, but expanding transmission infrastructure is challenging.
Register Now New York recently announced a goal of receiving 100% carbon-free energy by 2040 and the New England states all have ambitious greenhouse gas reduction goals, including a Massachusetts law requiring GHG emissions be 80% below 1990 levels by 2050.
The province-owned company, Hydro Quebec, supplies power to the provinces of Quebec, Ontario and New Brunswick in particular, as well as sending electricity directly into New York and New England. The power transmission interconnections between New York and New England have reached capacity and in order to increase export volumes into the US, "we need to build more transmission infrastructure," Gary Sutherland, relationship manager in business development, recently said during a presentation to reporters in Montreal.
TRANSMISSION OPTIONS
Hydro Quebec is working with US transmission developers, electric distribution companies, independent system operators and state government agencies to expand that transmission capacity in order to delivery more power from its hydro system to the US, as the province has closed the door on nuclear power and continues to prioritize hydropower, Sutherland said.
The company is looking to sign long-term power supply contracts that could help alleviate some of the investment risk associated with these large infrastructure projects.
"It`s interesting to recall that in the 1980s, two decade-long contracts paved the way for construction of Phase II of the multi-terminal direct-current system (MTDCS), a cross-border line that delivers up to 2,000 MW from northern Quebec to New England," Hydro Quebec spokeswoman Lynn St-Laurent said in an email.
Long-term prices have been persistently low since 2012, following the shale gas boom and the economic decline in 2008-2009, St-Laurent said. "As such, investment risks are too high for merchant transmission projects," she said.
Northeast power market fundamentals "remain strong for long-term contracts," on transmission projects or equipment upgrades that can deliver clean power from Quebec and "help our neighbors reach their ambitious clean energy goals," St-Laurent said.
NEW ENGLAND
In March 2017 an HQ proposal was selected by Massachusetts regulators to supply 9.45 TWh of firm energy to be delivered for 20 years. HQ`s proposal consisted of hydro power supply and possible transmission scenarios developed in conjunction with US partners.
The two leading options include a route through New Hampshire called Northern Pass and New England Clean Energy Connect through Maine.
The New Hampshire Site Evaluation Committee in March 2018 voted unanimously to deny approval of the $1.6 billion Northern Pass Transmission project, which is a joint venture between HQ and Eversource Energy`s transmission business. Eversource has been fighting the decision, with the New Hampshire Supreme Court accepting the company`s appeal of the NHSEC decision in October.
Briefs are being filed and oral arguments are likely to begin late spring or early summer, spokesman William Hinkle said in an email Tuesday.
After the Northern Pass permitting delay, Massachusetts chose the New England Clean Energy Connect project, which is a projected 1,200 MW transmission line, with 1,090 MW contracted to Massachusetts, leaving 110 MW for use on a merchant basis, according to St-Laurent.
NECEC is a joint venture between HQ and Central Maine Power, which is a subsidiary of Avangrid, a company affiliated with Spain`s Iberdrola. The NECEC project has received opposition from some environmental groups and still needs several state and federal permits.
NEW YORK
"The 5% of New York`s load that we furnish year in and year out ... is mostly going into the north of the state, it`s not coming down here," Sutherland said during a discussion at Pace University in New York City in 2017.
One potential project moving through the permitting phase, is the $2.2 billion, 1,000-MW Champlain Hudson Power Express transmission line being pursued by Transmission Developers -- a Blackstone portfolio company -- that would transport power from Quebec to Queens, New York.
Under New York`s proposed Climate Leadership Act which calls for the 100% carbon-free energy goal, renewable generation eligibility would be determined by the Public Service Commission. The PSC did not respond to a question about whether hydro power from Quebec is being considered as a potential option for meeting the state`s clean energy goal.
Ontario Electricity Capacity Gap threatens reliability as IESO forecasts shortfalls from the Pickering shutdown and rapid electrification, requiring new low-emission nuclear generation to meet net-zero targets, maintain baseload, and stabilize the grid.
Key Points
Expected 2030 shortfalls from Pickering closure and electrification, requiring new low-emission nuclear to meet net-zero.
✅ New low-emission nuclear needed to meet net-zero targets
Ontario faces an electricity supply shortage and reliability risks in the next four to eight years and will not meet net-zero objectives without building new low-emission, nuclear generation starting as soon as possible, according to a report released yesterday by the Power Workers' Union (PWU). The capacity needed to fill the expected supply gap will be equivalent to doubling the province's planned nuclear fleet in eight years.
The planned closure of the Pickering nuclear power plant in 2025 and the increase in demand from electrification of the economy are the drivers behind a capacity gap in 2030 of at least 3.6 GW which could widen to as much as 9.5 GW, Electrification Pathways for Ontario to Reduce Emissions, finds. Ontario's Independent Electricity System Operator (IESO) has since 2013 been forecasting a significant gap in the province's electricity supply due the closure of Pickering, but has been underestimating the impact of electrification, the report says.
In addition, the electrification of buildings, transport and industry sectors that will be needed to achieve goals of net-zero emissions by 2050 that being set by the federal government and civil society will see the province's electricity demand increase by at least 130% over current planning forecasts, and potentially by over 190%. Leveraging electricity, natural gas and hydrogen synergies can reduce supply needs, but 55 GW of new electricity capacity, including new large-scale nuclear plants, will still be needed by 2050 - four times Ontario's current nuclear and hydro assets - the report finds.
These findings underscore the urgent need for a paradigm shift in Ontario's electricity planning and procurement process, the authors say, adding that immediate action is needed both to mitigate the system reliability risks and enable the significant societal benefits needed to pursue net-zero objectives. Planning for procurement to replace Pickering's capacity, or to pursue life extension options, must begin as soon as possible.
"Policymakers around the world realise climate change can't be tackled without nuclear. Ontario's nuclear fleet has delivered emissions reductions for over 50 years," PWU President Jeff Parnell said. "In fact, without building new nuclear units, Ontario will miss its emission reduction targets and carbon emissions from electricity generation will rise dramatically, as explored in why Ontario's power could get dirtier today."
"This report clearly shows that Ontario cannot sustain the low-carbon status of its hydro and nuclear-based electricity system, decarbonise its economy and meet its carbon reduction targets without new nuclear or continued operation at Pickering in the near term. Most disturbing is the fact that we are already well behind and needed to start planning for this capacity yesterday," he said.
The six operating Candu reactors at Ontario Power Generation's Pickering plant have been kept in operation to provide baseload electricity during the refurbishment of units at the Darlington and Bruce plants. Currently, the company plans to shut down Pickering units 1 and 4 in 2024 and units 5 to 8 in 2025, even as Ontario moves to refurbish Pickering B to extend life.
U.S. Natural Gas Power Demand is surging for electricity generation amid summer heat, with ERCOT, Texas grid reserves tight, EIA reporting coal and nuclear retirements, renewables intermittency, and pipeline expansions supporting combined-cycle capacity and prices.
Key Points
It is rising use of natural gas for power, driven by summer heat, plant retirements, and new combined-cycle capacity.
✅ ERCOT reserve margin 9%, below 14% target in Texas
✅ Gas share of U.S. power near 40-43% this summer
✅ Coal and nuclear retirements shift capacity to combined cycle
As the hot months linger, it will be natural gas that is leaned on most to supply the electricity that we need to run our air conditioning loads on the grid and keep us cool.
And this is surely a great and important thing: "Heat causes most weather-related deaths, National Weather Service says."
Generally, U.S. gas demand for power in summer is 35-40% higher than what it was five years ago, with so much more coming (see Figure).
The good news is regions across the country are expected to have plenty of reserves to keep up with power demand.
The only exception is ERCOT, covering 90% of the electric load in Texas, where a 9% reserve margin is expected, below the desired 14%.
Last summer, however, ERCOT’s reserve margin also was below the desired level, yet the grid operator maintained system reliability with no load curtailments.
Simply put, other states are very lucky that Texas has been able to maintain gas at 50% of its generation, despite being more than justified to drastically increase that.
At about 1,600 Bcf per year, the flatness of gas for power demand in Texas since 2000 has been truly remarkable, especially since Lone Star State production is up 50% since then.
Increasingly, other U.S. states (and even countries) are wanting to import huge amounts of gas from Texas, a state that yields over 25% of all U.S. output.
Yet if Texas justifiably ever wants to utilize more of its own gas, others would be significantly impacted.
At ~480 TWh per year, if Texas was a country, it would be 9th globally for power use, even ahead of Brazil, a fast growing economy with 212 million people, and France, a developed economy with 68 million people.
In the near-term, this explains why a sweltering prolonged heat wave in July in Texas, with a hot Houston summer setting new electricity records, is the critical factor that could push up still very low gas prices.
But for California, our second highest gas using state, above-average snowpack should provide a stronger hydropower for this summer season relative to 2018.
Combined, Texas and California consume about 25% of U.S. gas, with Texas' use double that of California.
Across the U.S., gas could supply a record 40-43% of U.S. electricity this summer even as the EIA expects solar and wind to be larger sources of generation across the mix
Our gas used for power has increased 35-40% over the past five years, and January power generation also jumped on the year, highlighting broad momentum.
Our gas used for power has increased 35-40% over the past five years. DATA SOURCE: EIA; JTC
Indeed, U.S. natural gas for electricity has continued to soar, even as overall electricity consumption has trended lower in some years, at nearly 10,700 Bcf last year, a 16% rise from 2017 and easily the highest ever.
Capacity wise, gas is sure to continue to surge its share 45% share of the U.S. power system.
"More than 60% of electric generating capacity installed in 2018 was fueled by natural gas."
We know that natural gas will continue to be the go-to power source: coal and nuclear plants are retiring, and while growing, wind and solar are too intermittent, geography limited, and transmission short to compensate like natural gas can.
"U.S. coal power capacity has fallen by a third since 2010," and last year "16 gigawatts (16,000 MW) of U.S. coal-fired power plants retired."
This year, some 2,000 MW of coal was retired in February alone, with 7,420 MW expected to be closed in 2019.
Ditto for nuclear.
Nuclear retirements this year include Pilgrim, Massachusetts’s only nuclear plant, and Three Mile Island in Pennsylvania.
This will take a combined ~1,600 MW of nuclear capacity offline.
Another 2,500 MW and 4,300 MW of nuclear are expected to be leaving the U.S. power system in 2020 and 2021, respectively.
As more nuclear plants close, EIA projects that net electricity generation from U.S. nuclear power reactors will fall by 17% by 2025.
From 2019-2025 alone, EIA expects U.S. coal capacity to plummet nearly 25% to 176,000 MW, with nuclear falling 15% to 83,000 MW.
In contrast, new combined cycle gas plants will grow capacity almost 30% to around 310,000 MW.
Lower and lower projected commodity prices for gas encourage this immense gas build-out, not to mention non-stop increases in efficiency for gas-based units.
Remember that these are official U.S. Department of Energy estimates, not coming from the industry itself.
In other words, our Department of Energy concludes that gas is the future.
Our hotter and hotter summers are therefore more and more becoming: "summers for natural gas"
Ultimately, this shows why the anti-pipeline movement is so dangerous.
"Affordable Energy Coalition Highlights Ripple Effect of Natural Gas Moratorium."
In April, President Trump signed two executive orders to promote energy infrastructure by directing federal agencies to remove bottlenecks for gas transport into the Northeast in particular, where New England oil-fired generation has spiked, and to streamline federal reviews of border-crossing pipelines and other infrastructure.
Builders, however, are not relying on outside help: all they know is that more U.S. gas demand is a constant, so more infrastructure is mandatory.
They are moving forward diligently: for example, there are now some 27 pipelines worth $33 billion already in the works in Appalachia.
California Nuclear Renewable Bill AB 2898 seeks to add nuclear to the Renewables Portfolio Standard, impacting Diablo Canyon, PG&E compliance, carbon-free targets, and potential license extensions while addressing climate goals and natural gas reliance.
Key Points
A bill to add nuclear to California's RPS, influencing Diablo Canyon, PG&E planning, and carbon-free climate targets.
✅ Reclassifies nuclear as renewable in California's RPS.
✅ Could influence Diablo Canyon license extension and ownership.
✅ Targets carbon-free goals while limiting natural gas reliance.
Although he admits it's a long shot, a member of the California Legislature from the district that includes the Diablo Canyon nuclear plant has introduced a bill that would add nuclear power to the state's list of renewable energy sources.
"I think that nuclear power is an important component of generating large-scale electricity that's good for the environment," said Jordan Cunningham, R-San Luis Obispo. "Without nuclear as part of the renewable portfolio, we're going to have tremendous difficulty meeting the state's climate goals without a significant cost increase on electricity ratepayers."
Established in 2002, California's Renewables Portfolio Standard spells out the power sources eligible to count toward the state's goals to wean itself of fossil fuels. The list includes solar, wind, biomass, geothermal, small hydroelectric facilities and even tidal currents. The standard has been updated, currently calling for 60 percent of California's electricity to come from renewables by 2030 and 100 percent from carbon-free sources by 2045, even as some analyses argue net-zero emissions may be difficult to achieve without nuclear power.
Nuclear power is not part of the portfolio standard and Diablo Canyon — the only remaining nuclear plant in California — is scheduled to stop producing electricity by 2025, even as some Southern California plant closures face postponement to maintain grid reliability.
Pacific Gas & Electric, the operators of Diablo Canyon, announced in 2016 an agreement with a collection of environmental and labor groups to shut down the plant, often framed as part of a just transition for workers and communities. PG&E said Diablo will become uneconomical to run due to changes in California's power grid — such as growth of renewable energy sources, increased energy efficiency measures and the migration of customers from traditional utilities to community choice energy programs.
But Cunningham thinks the passage of Assembly Bill 2898, which he introduced last week, — as innovators like Bill Gates' mini-reactor venture tout new designs — could give the plant literally a new lease on life.
"If PG&E were able to count the power produced (at Diablo) toward its renewable goals, it might — I'm not saying it will or would, but it might — cause them to reconsider applying to extend the operating license at Diablo," Cunningham said.
Passing the bill, supporters say, could also make Diablo Canyon attractive to an outside investor to purchase and then apply to the Nuclear Regulatory Commission for a license extension.
But nuclear power has long generated opposition in California and AB 2898 will face long odds in Sacramento, and similar efforts elsewhere have drawn opposition from power producers as well. The Legislature is dominated by Democrats, who have expressed more interest in further developing wind and solar energy projects than offering a lifeline to nuclear.
And if the bill managed to generate momentum, anti-nuclear groups will certainly be quick to mobilize, reflecting a national energy debate over Three Mile Island and whether to save struggling plants.
When told of Cunningham's bill, David Weisman, outreach coordinator for the Alliance for Nuclear Responsibility, said flatly, "Diablo Canyon has become a burdensome, costly nuclear white elephant."
Critics say nuclear power by definition cannot be considered renewable because it leaves behind waste in the form of spent nuclear fuel that then has to be stored, while supporters point to next-gen nuclear designs that aim to improve safety and costs. The federal government has not found a site to deposit the waste that has built up over decades from commercial nuclear power plants.
Even though Diablo Canyon is the only nuclear plant left in the Golden State, it accounts for 9 percent of California's power mix. Cunningham says if the plant closes, the state's reliance on natural gas — a fossil fuel — will increase, pointing to what happened when the San Onofre Nuclear Generating Station closed.
In 2011, the final full year operations for San Onofre, nuclear accounted for 18.2 percent of in-state generation and natural gas made up 45.4 percent. The following year, nuclear dropped to 9.3 percent and gas shot up to 61.1 percent of in-state generation.
"If we're going to get serious about being a national leader as California has been on dealing with climate change, I think nuclear is part of the answer," Cunningham said.
But judging from the response to an email from the Union-Tribune, PG&E isn't exactly embracing Cunningham's bill.
"We remain focused on safely and reliably operating Diablo Canyon Power Plant until the end of its current operating licenses and planning for a successful decommissioning," said Suzanne Hosn, a PG&E senior manager at Diablo Canyon. "The Assemblyman's proposal does not change any of PG&E's plans for the plant."
Cunningham concedes AB 2898 is "a Hail Mary pass" but said "it's an important conversation that needs to be had."
The second-term assemblyman introduced a similar measure late last year that sought to have the Legislature bring the question before voters as an amendment to the state constitution. But the legislation, which would require a two-thirds majority vote in the Assembly and the Senate, is still waiting for a committee assignment.
AB 2898, on the other hand, requires a simple majority to move through the Legislature. Cunningham said he hopes the bill will receive a committee assignment by the end of next month.
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.
