SUGAR Volt: Boeing puts vision to work in hybrid electric aircraft

Dec 30, 2012 by Nancy Owano report

(Phys.org)—Boeing has been working on a project that signifies the future of commercial air transportation. As the story goes, about five years ago at a conference on advanced aircraft technologies, posing questions on what the future of aircraft would look like, somebody stood up and said, "What about an electric airplane?" Almost everyone laughed. Boeing personnel did not laugh. Can we make an airplane that has batteries that actually works? They took it as a challenge, in designing a commercial plane capable of low-emission flights. Marty Bradley, technical fellow with Boeing Research & Technology, and part of its SUGAR (Subsonic Ultra Green Aircraft Research) project, has been talking about the company's hybrid electric design, the SUGAR Volt, ever since.

This is designed as a plane that will combine electric power with traditional fuel. Boeing sees it as an energy-efficient model for future commercial flying. The Volt concept is a hybrid propulsion system, using both jet fuel and batteries, a greater wingspan and open-rotor engines. It plugs in at the airport, charges its batteries up, and flies its mission. To enable portions of flight with low or zero emissions, electricity is used as a supplement or replacement. Dual-turbine engines would be powered by traditional jet fuel, and at cruising altitude, the system could turn over to electrical power. Adding energy-plus points, the SUGAR Volt's longer wings allow for greater lift and the wings can fold when landed to accommodate airport gate space.

Boeing noted that the fuel burn reduction and the 'greening' of the electrical power grid can produce large reductions in emissions of life cycle CO2 and nitrous oxide. propulsion also has the potential to reduce noise.

In the SUGAR study, the team reported that hybrid electric engine technology was a "game-changing technology" and a "clear winner" because it met NASA's goals to reduce fuel burn, greenhouse gases, nitrous oxide emissions, noise and field length. Bradley recently said that Boeing is looking at a 2030 to 2050 time frame for the SUGAR Volt.

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Earlier this year, Bradley said that "There is a lot of uncertainty as to how good batteries will be in 2030 to 2050. But we are quite encouraged to see battery companies starting to show real products with much higher performance."

On the larger scale, Boeing's SUGAR team is working to identify future commercial transport concepts for NASA. The team is looking at various concepts and technology options for future years. These include hybrid battery-gas turbine propulsion, fuel cells, fuel cell–gas turbine hybrid propulsion systems, cryogenic fuels, cryogenically cooled engines and associated technologies, advanced batteries and open rotor/turboprop technologies.

The SUGAR Volt, one of the concepts, shows potential to meet NASA's environmental goals, as the SUGAR Volt will emit less carbon dioxide and less nitrogen oxide than aircraft in operation today.

Hybrid is a concept making frequent news in aviation on other fronts. According to reports in November last year, Israel's El Al Airlines planned to outfit 20 of their 737s with electric drive units that will provide power for the planes to taxi while on the ground. Several other companies were exploring similar ideas.

Bloomberg this year reported that airlines continue studying new technologies and one study area, similarly, is taxiing. Equipment makers such as Honeywell are devising electric motors that can move jets, which would allow pilots to taxi without having to depend on main engines or diesel tractors.

The first new with electric-taxi technology may be in production in as few as three years, according to Bloomberg Businessweek.

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Lurker2358
1.7 / 5 (12) Dec 30, 2012
There's better options, if only our culture was more interested in being slightly more efficient, rather that slightly more "convenient".

Clearly, this technology is a trade-off between pleasing the passenger, who wants to get somewhere immediately, and cutting fuel costs.

No mention of any kind of solar panel technology to help re-charge the batteries, but at this scale for winged aircraft, it might not be worth the extra weight.

On the one-manned "Solar One" aircraft experiment, the panels were able to charge the battery more than the amount of charge consumed during 26 hours of continuous flight, so that they landed with a higher charge than they started.

If you can charge batteries through solar power half as quickly as you are using them, you actually double max range for daytime flights, or at the very least reduce ground charge time by half.

infinite series:

2 = 1 0.5 0.25 ... ... (1/2^n)

antialias_physorg
4.4 / 5 (13) Dec 30, 2012
No mention of any kind of solar panel technology to help re-charge the batteries

Because it's dumb? Do the math: Solar constant times surface area times efficiency of solar panels - the additional energy you'd get would be pitiful compared to the energy requirements of a plane (this is also the reason why you don't see solar panels on cars).
If you plastered the entire plane you could probably run the air conditioning. That's about the size of it.

On the one-manned "Solar One" aircraft experiment...

Solar One is a glider. For most of its flight time it doesn't use any power at all. It did not recharge more than it started with (because it always started with full batteries charged on the ground)

Also wikipedia notes:
"the aircraft had insufficient solar cells for sustained flight"
philw1776
5 / 5 (4) Dec 30, 2012
Why do otherwise numerate folks lose the ability to calculate when discussing "green" tech? The fantasy desire for unicorn faerie tech over rides common sense. The hyperbole sets expectations that demeans serious efforts to utilize solar, etc. in appropriate applications.
antialias_physorg
5 / 5 (5) Dec 30, 2012
Why do otherwise numerate folks lose the ability to calculate when discussing "green" tech?

Amen, though I would not only apply this criticism to clean tech. It seems that as soon as any kind of science is discussed in these comment sections people just switch of their brains and start spouting techno-babble without any attempt at looking at whether it makes even the remotest numerical sense.

Solar is great. It has a bright future ahead of it in all kinds of settings (from powerplants to autonomous homes to space exploartion to ... ). But autonomous, solar powered personal mobility (or mass transit) system isn't one of them
Lurker2358
1.7 / 5 (6) Dec 30, 2012
It did not recharge more than it started with (because it always started with full batteries charged on the ground)


BS.

I actually watched a documentary on it, with live action videos from when they were doing the test run.

The started with less than half charge in the batteries and ended with more charge than they started.
Newbeak
not rated yet Dec 30, 2012
What I am unclear about is how the batteries of the SUGAR VOLT would power the aircraft.Would it spin the turbines with electric motors? If so,it would take a hell of a lot of juice to give enough thrust for cruising.
antialias_physorg
5 / 5 (2) Dec 30, 2012
Cruising thrust needed is significantly smaller than takeoff thrust (From the figures for an Airbus 380 the it's about a quarter toa fifth). So a combined system where the convetional engines delievr the takeoff power and the electrics provide cruising speed might be effective (for relatively short flights. I don't see where a plane with significant payload could carry enough juice for intercontinental ones given current battery power and weight figures)
nkalanaga
not rated yet Dec 30, 2012
Antialias: As you said, it takes a lot more power to takeoff than to cruise. The plane is designed to be recharged at the airport, so it's also possible that it would have smaller combustion engines. They could be designed to provide cruising power, with the electrics giving the added boost need for takeoff. That would reduce the fuel requirements, noise, and exhaust at the ground, where it's most likely to bother people. That way, the range would only be limited by the fuel capacity, as with present planes, and the same amount of fuel should go further.
Newbeak
not rated yet Dec 30, 2012
The plane is designed to be recharged at the airport, so it's also possible that it would have smaller combustion engines.

Rereading the article,it says the concept uses dual-turbine engines,so I assume one turbine would be spun by an electric motor,and the other by combustion gases? Sounds like a flying Prius.
ab3a
not rated yet Dec 30, 2012
Also, let us not forget to keep reserve power available for emergencies --such as a supposedly clear runway that isn't.

The notion of using electricity for a transmission medium is interesting, but ultimately foolish. If it is going to be used in the same manner as the turbo-fan engines, then we're not going to see much improvement. On the other hand, if we consider making a more efficient aircraft through the use of differently ducted fans, that COULD do quite a bit.
HTK
not rated yet Dec 30, 2012
'Can we make an airplane that has batteries that actually works?'

The batteries actually works but the airplane....

Aynway, higher survival stats without explosion during emergency landing or crash landing... and should be way cheaper right? With much less maintenance.
baudrunner
1 / 5 (1) Dec 30, 2012
There are better ways to implement a hybrid system that do not require carrying heavy batteries. If the idea is to cut fuel costs, then why add to those costs by increasing the payload? Why not just use less fuel?
Newbeak
not rated yet Dec 30, 2012

Aynway, higher survival stats without explosion during emergency landing or crash landing...

Yes,crash fires make survivable crashes fatal.Too bad they can't carry fuel in drop tanks on the wings,but that would no doubt cut into efficiency.
antialias_physorg
5 / 5 (1) Dec 30, 2012
Too bad they can't carry fuel in drop tanks on the wings

In the case of an emergency landing it's standard procedure to vent (almost) all remaining fuel before touchdown. so the danger would only really be lessened in a plane that was all electric (but I think explosion/fire is a very insignificant contributor to the number of airplane deaths - so that's a pretty academic discussion in any case)
Lurker2358
1 / 5 (1) Dec 30, 2012
The video concept says it will run the turbofans on battery power.

The reason this works is because batteries are far more efficient than generators, therefore they are much cleaner as long as the electricity for the charge is coming from a clean source.

If the electricity for the charge is coming from a coal fired power plant, then this is probably still cleaner than jet fuel, but just barely; probably not enough to matter.
antialias_physorg
5 / 5 (2) Dec 30, 2012
If the electricity for the charge is coming from a coal fired power plant, then this is probably still cleaner than jet fuel, but just barely; probably not enough to matter.

Even if it were the same then it would matter - because dispersing water vapor and greenhouse gases way up in the atmosphere is a lot more damaging than closer to the ground (and powerplants can have exhaust treatment facilities which planes don't habitually lug around).

A quick google shows that coal powerplants and airplane turbines have about the same power conversion efficiency (40%).
(for coal power plants the projected efficiency potential for the next 10 years tops out at 55%. I couldn't readily find any figures for the jet engines as the term 'efficiency' seems to have any number of definitions there)

Newbeak
not rated yet Dec 30, 2012

Even if it were the same then it would matter - because dispersing water vapor and greenhouse gases way up in the atmosphere is a lot more damaging than closer to the ground (and powerplants can have exhaust treatment facilities which planes don't habitually lug around).


I never heard of exhaust scrubbers for jet engines.Electric powered cruising therefore becomes much more important for the environment.
Lurker2358
1 / 5 (1) Dec 30, 2012
Even if it were the same then it would matter - because dispersing water vapor and greenhouse gases way up in the atmosphere is a lot more damaging than closer to the ground (and powerplants can have exhaust treatment facilities which planes don't habitually lug around).

A quick google shows that coal powerplants and airplane turbines have about the same power conversion efficiency (40%).
(for coal power plants the projected efficiency potential for the next 10 years tops out at 55%. I couldn't readily find any figures for the jet engines as the term 'efficiency' seems to have any number of definitions there)


Batteries aren't 100% efficient though.

I doubt they get coal fired power plants to 55% Carnot efficiency.

Maybe that's co-generation efficiency?

The most efficient diesel engines are on super tankers, and those are only 50% efficient.
antialias_physorg
3.7 / 5 (3) Dec 30, 2012
Batteries aren't 100% efficient though.

Figures for Li-ion batteries vary between 80-90% (depending on make and how fast you draw the juice out)
Electric motors (especially the more powerful ones) are around 90% efficient.

However the energy/mass ratio for batteries is significantly smaller than for fuels (which has to be factored in because it means we'd either need more flights or larger planes - both of which means more hydrocarbon fuel needed due to more takeoffs or takeoffs of planes with larger mass). But I'm guessing the Boeing guys have figured that in.

The video mentions that the (hydrocarbon) generators would run at optimal speed to charge the batteries - so no need to store all the energy you need on the flight in the batteries (i.e. less batteries needed)

In summary: I think it's an interesting proposal and certainly a first step worth taking until we figure out how to go either fully electric or hydrogen for planes.
Newbeak
not rated yet Dec 30, 2012

The video mentions that the (hydrocarbon) generators would run at optimal speed to charge the batteries - so no need to store all the energy you need on the flight in the batteries (i.e. less batteries needed)

I wonder if other battery technologies would be better than Lithium Ion,such as zinc air: http://en.wikiped..._battery
antialias_physorg
5 / 5 (1) Dec 30, 2012
Zinc-air batteries are interesting for the weight issue (and also for the availability of zinc which is much greater than that of lithium).

However, the current types do not allow frequent recharging. This means once they wear out they have to be rendered down (in essence: molten), the metal separated and then rebuilt which takes an enormous amount of energy.

(Current) lithium ion batteries cab be recharged roughly an order of magnitude more often than (current) zinc air batteries.

There's a number of ideas to alleviate that. E.g. using gels instead of liquid electrolyteslike here:
http://www.scient...T.72.305
but those are still just lab prototypes. Whether that will work in industrial/real worls (and weather) setting isn't out yet.
vpn3000
1 / 5 (1) Dec 30, 2012
Cleary, Boeing stronly feels the threat from electricity-driven high speed train. China's new operational bullet train travels over 2000kms in 8 hours. Experimental models in lab can move over 1000km/hour, which is as fast as the plane. So, in only a few years, do we still need planes?
nkalanaga
not rated yet Dec 30, 2012
Yes, we'll still need the planes. Trains can only go where there are tracks, and much of the cost of high speed trains is the track and other right of way. A plane can go anywhere there's a runway long enough to land it. If the train runs from A to B, and one wants to go to C, one needs new tracks. To fly A-C instead of A-B all one needs is a runway. Trains are great where there's enough traffic to support them, which is the case in parts of Europe and Asia, with high population densities. In much of the Americas and Africa the towns are too spread out.
Bubba
1 / 5 (1) Dec 30, 2012
Ok so instead of the conventional takeoff / landing approach to flying - leave several of these solar powered wings in the air and then "sky hook" cargo from point a to point b. Later you can do the same for people...

Technical challenges exist but are they insurmountable? What part of the American culture lead to the creation of "professional naysayers?"

I've learned in my short life to "never say never" because things are happening now that I never thought were possible...

On the other hand things are happing now that should never have happened - like the national debt of the USA. but that's another story.

"never say never" - virtually everything is possible...

Even the so called "laws" of physics aren't laws. They are our current understanding of physics. Those might change in the future. Will they? I don't know but I'll never say that they never will...
vpn3000
1 / 5 (1) Dec 30, 2012
Yes, we'll still need the planes. Trains can only go where there are tracks, and much of the cost of high speed trains is the track and other right of way. A plane can go anywhere there's a runway long enough to land it. If the train runs from A to B, and one wants to go to C, one needs new tracks. To fly A-C instead of A-B all one needs is a runway.


Cars can only go where there are roads. How did people manage to build so many roads? It's a matter of what benefits the oil industry, when the country is controlled by oil companies. Building airports are not as simpe as building run ways. Plus the huge amount of oil consumption, tracks are much cheaper.

As soon as you build tracks, people will move to live where there are tracks. That was how cities came into being.

Whydening Gyre
1 / 5 (3) Dec 31, 2012
...That was how cities came into being.


Not true. It just made them grow faster. But I'm only quibbling.

n regards to improving efficiency of CO2 producing engines (improving ANYthing, actually);
A percent here, 2.3 percent there and half a percent over there... it all adds up. In the aggregate, it's ALL worth something...
quit nit-picking ideas and efforts others have made - at least they are doing something about a problem.
nappy
1 / 5 (1) Dec 31, 2012
THis is pure balderdash. And, if one will take a moment and check where the money for this boondogle came from, you will find the federal government wasting the tax dollars of kids that aren't even born yet. A first year physics student with a $10 calculator can blow this idea up in 5 minutes. What criminal insanity!
nkalanaga
not rated yet Dec 31, 2012
No, roads existed long before cars were thought of. All we did there was invent all-weather surfaces for them. A basic road is much cheaper than a railroad, and can be built where a decent railroad is impractical. Plus, roads are more flexible, especially where you don't have a trainload of people wanting to travel between two points at the same time. If passenger trains worked that well for local travel in the US we'd still have them. Until autos became reliable that WAS the main method of long distance travel. Rails are great for bulk freight, and can compete with airlines between major hubs, but neither are flexible enough for a low-density, high-mobility culture.
Steve123
5 / 5 (1) Jan 19, 2013
Serial Hybrid electric drive technology is old news. one hundred years old. Our current technology is making it commercially viable.

Pure electric aircraft, outside of RC models, are not viable for people. This is not the "Phoenix".

Serial hybrid drive using turbine co-generators to drive electric high efficiency turbofans or prop planes are VERY VIABLE.

Siemens already did it in 2011. Increased efficiency and lowered cost of operation will win. Follow the money.

Aircraft companies will develop and produce what they can sell. If it is more efficient,and serial-hybrid and some parallel or mixed systems are, then it is coming. Bank on it.

Batteries are purely a minor power backup, if included for drive power at all, NOT a primary drive source.