back to article Captain Piccard's planet-orbiting solar aircraft in warped drive drama

An airplane powered by nothing more than the Sun's rays has completed its 42,000-km (26,098-mile) journey around the world after landing in Abu Dhabi on Tuesday. The Solar Impulse 2, piloted by Bertrand Piccard for its final leg, made the trip in 17 legs, flying around the Northern hemisphere with stops in nine countries. Its …

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  1. Youngone Silver badge

    It's a start

    It won't replace 787's or whatever is plying the skies these days, but it's a start, and new technology has to start somewhere.

    How long did it take for planes to replace ships for long distance travel? My Dad emigrated to New Zealand from the UK on a ship in the 1950's, so at least 50 years.

    1. John Sager

      No, it's not

      It's a dead end. The air transport industry we currently have only works through a combination of the energy density of kerosene, the efficiency of jet engines at the end of a nearly 80 year development cycle, and similar improvements in the application of aerodynamic design.

      Electric aircraft have to replicate that. They will benefit from the aerodynamic advances, but we must be getting reasonably asymptotic on that. Energy will still need to be stored as we can probably only expect a factor of 2 or 3 improvement in solar cell energy conversion and we fly at night. So we need a big step in battery energy density. Plus either an incredibly fast charge process (2 nuclear power stations at Heathrow), or a quick battery swap-out process and a slower recharge (1 nuclear power station at Heathrow)

      Then how do we make an 'electric jet engine'? I guess the technique would be to replace the jet core in a high-bypass turbofan (e.g. Trent 900) with a similarly specified electric motor (about 56 MW at takeoff).

      Stick with the kero & manufacture it from CO2, H2O and nuclear energy when the oil & gas runs out.

      1. Andrew Newstead

        Re: No, it's not

        Re the electric Hi-bypass fan, Rolls-Royce are investigating just this idea in relation to an hybrid propulsion system, with Airbus. In this approach a gas turbine powered generator produces electricity which is used by the electric fans.

        Whether this actually comes about is another question.

      2. TitterYeNot

        Re: No, it's not

        "It's a dead end. The air transport industry we currently have only works through a combination of the energy density of kerosene, the efficiency of jet engines at the end of a nearly 80 year development cycle, and similar improvements in the application of aerodynamic design."

        I think a lot of commentards here are missing the point of what Mr. Piccard is saying - it's not that in 10 years time we'll all be flying merrily round the world in solar powered jet aircraft, but that in the next decade or so battery mass & efficiency will be at a point where smaller, electric propellor powered aircraft will start to become commercially viable.

        I think you're absolutely right in that the development of electronically powered jet turbine engines will take decades, as will the development of electronic storage with enough energy density and robustness to carry hundreds of people across the Atlantic, but its precisely by flying round the world in a solar powered aircraft that we learn about the technologies required e.g. how not to 'cook' the batteries as happened with the Solar Impulse 2 and which grounded it last year. Don't forget, electric microlight aircraft are already in the air, electric aircraft will just get bigger over time as electronic storage and lightweight material technology improves.

        And to change the subject completely, I'm sure I'm not the only one who hopes that at some point in the flight, Captain Piccard uttered the words "Make it so..."

        1. Alan Brown Silver badge

          Re: No, it's not

          "in the next decade or so battery mass & efficiency will be at a point where smaller, electric propellor powered aircraft will start to become commercially viable."

          You'd need a factor of 5-10 improvement in battery energy density to make this viable. That's probably more than is physically possible, even if you use flow batteries. One of the reasons airliners can fly more than a few hundred miles is because they don't have to carry their own oxygen

    2. JeffyPoooh
      Pint

      Re: It's a start

      505 days. Puh. People have 'run' around the world in 621 days.

      No. Solar-powered aircraft are not the future of airliners, due to basic physics. Solar Flux, and Scaling Laws.

      This stunt is similar to the Human-Powered Helicopter. "Someday soon, we will all get to work in our own Human-Powered Helicopter." Sigh...

      1. cray74

        Re: It's a start

        No. Solar-powered aircraft are not the future of airliners

        Orville's and Wilbur's 1903 airplane wasn't the future of airliners. Just about every engineering concept embodied in the plane was tossed out on the path to the A380 and 787. But it was an important proof of concept, just like Piccard's plane. At a minimum, it showed it could be done.

        , due to basic physics. Solar Flux, and Scaling Laws.

        Yes, that's true. But the future of high-endurance solar-powered heavier-than-air flight isn't necessarily in airliners.

        1. Anonymous Coward
          Anonymous Coward

          Re: It's a start

          Hmmn.. the only heavier than air aircraft I can see maybe going all-electric for its propulsion is something like the Skycat, a Hybrid Air Vehicle, which gets some of its lift from helium, some from its steerable fans, and the rest from the aerofoil shape of its envelope. Cover the upper surface of a Skycat with solar panels and you might get enough power to be worthwhile with next generation solar cells and power storage.

          I still uspect the way to go in the forseeable would be with synthetic petrol/avgas made by recycling atmospheric CO2, unless some kind of system that stores as much enrgy per unit volume as petrol does and is less polluting than current batteries are is developed.

    3. Anonymous Coward
      Facepalm

      Re: It's a start

      It is not to replace a 747/787...

      It is for autonomous and continuous craft. Say mapping or camera work. A small solar powered craft that can go up, fly for an unspecified length of time, and come back down. Not taking cargo/passengers, but just images/data.

      1. John Sager

        Re: It's a start

        It is for autonomous and continuous craft.

        I'll sorta buy that. It's more likely that a uav (hence no need for pilot safety & life support stuff) could be engineered within current & <10yr future constraints. That's OK for mapping/surveillance but wifi/tv transmitters will rapidly eat into the power budget. There is still the issue of energy to manufacture solar cells (and batteries) but that's the price to pay if the business benefits outweigh that.

  2. Sebastian A

    Halve the CO2 emissions, sure, until the time comes to dispose of end-of-life solar panels.

    1. Mark 85

      Add to that for charging the batteries on the ground before take-off if for no other reason than to take-off and run into cloudy weather. Wouldn't want to do that with low battery power.

      Actually, this type of plane might well work for private aviation and small, charter firms. I can't see a scheduled airline using them until there's some advancements to make them all-weather aircraft.

      1. AMBxx Silver badge

        And all they're hoping for is to carry 50 passengers? Love to see how big the planned airport is.

    2. Chris Miller

      It's not just the disposal, Sebastian. The EROEI (energy return on energy invested) of solar cells operating at temperate latitudes (like the UK) is negative - that is, the energy generated during their working life is only ~83 % of the energy consumed during their manufacture.

      You can think of solar cells in the UK as giant batteries, charged up (most probably in China, using coal and oil) and then gradually releasing their stored energy as the sun shines. So not very good at reducing CO2 emissions, but very effective at transferring money to wealthy landowners from those in fuel poverty.

      1. Sebastian A

        Whatever happened to those paint-on solar cells that were all over the news a few years ago?

        Also, look at the hippies downvoting information. Fingers in years, "I can't hear you nyah nyah" solar will save the world. Not with current tech it won't.

    3. Alan Brown Silver badge

      "Halve the CO2 emissions, sure, until the time comes to dispose of end-of-life solar panels."

      And by not taking into account the environmental and/or CO2 costs of making the things.

      (You can reduce CO2 by polluting, as is happening in china. Cleaning up the byproducts generates even more CO2)

  3. Camilla Smythe

    Around The World in 21 Days.

    What were they faffing about with for the other 488 days?

    I'll leave someone else to explain which bit I misread.

  4. Anonymous Coward
    Anonymous Coward

    Oh come on...

    This entire project is no more than an environmental w*nk by some people with more money than sense.

    What have they proven here ? That ONE guy can fly around the world if he has a spare year and a half and 200 million USD ? Really ?

    These idiots make me so angry...

    1. thx1138v2

      Re: Oh come on...

      The key is in that last paragraph: "You may be ending your around the world flight today, but the journey to a more sustainable world is just beginning." - UN Secretary-General Ban Ki-moon

      "Sustainable development", i.e. "sustainable world", is globalist speak for destroying private property rights. That means ALL private property rights from home ownership to private enterprise. See U.N. Agenda 21. Their point of view is that only global government can provide responsible management of planet's resources so they must control everything and everyone.

      http://blog.heartland.org/2014/04/u-n-agenda-21-impacts-private-property-rights-and-freedom/

      Think that's foolish? They have organizations all the way down to the city and county governments promoting "sustainable development". If you see any of your local government leaders promoting "sustainable development", get rid of them sooner rather than later. Many times the individuals aren't from an Agenda 21 organization but use or hire "consultants" who are. Once you start looking for it, you'll find it everywhere.

      1. Florida1920

        Re: Oh come on...

        Agenda 21 is a non-binding, voluntarily implemented action plan of the United Nations with regard to sustainable development. It is a product of the Earth Summit (UN Conference on Environment and Development) held in Rio de Janeiro, Brazil, in 1992.

        https://en.wikipedia.org/wiki/Agenda_21#United_States

        The Republicans oppose it, so it must be dangerous!

        Meanwhile: https://www.youtube.com/watch?v=wFNO2sSW-mU

        1. Ilmarinen

          Re: Oh come on...

          Quite - but I don't expect it will be "voluntary" for the plebs upon who it is "voluntarily" inflicted by the great and the good.

          cf. Blighty's Climate Change Act - voluntarily voted in by MPs, with the consequent costs inflicted on the poor (but with nice subsidies to the rich).

  5. Pascal Monett Silver badge

    "I'm sure that within 10 years we'll see electric airplanes transporting 50 passengers"

    No we won't.

    This experiment requires a 2.3-ton plane with the wingspan of an Airbus A380 to transport 2 guys and 633 kilos of lithium batteries at a speed of max 90km/h. During the night it goes slower to save on energy.

    Add 50 passengers with their luggage, stewardesses and in-flight entertainment, not to mention active radar, ILS and autopilot (with the assorted computers and black boxes) and you'll need a football stadium-sized wing to just keep it in the air, to say nothing about taking off.

    I salute the accomplishment. It demonstrates improvements in solar cells and is certainly a feat of engineering. But let's not get carried away, this toy is not the future.

    1. DropBear
      Facepalm

      Re: "I'm sure that within 10 years we'll see electric airplanes transporting 50 passengers"

      These sort of predictions tend to extrapolate revolutionary advances in the next <insert convenient timespan> based on the Moore's law-like rapid advance we can plainly see today in aerodynamics, electric turbines, solar cells and battery technology. Commencing any second now, honest, guv. Any second...

      1. John Brown (no body) Silver badge
        Coat

        Re: "I'm sure that within 10 years we'll see electric airplanes transporting 50 passengers"

        "Commencing any second now, honest, guv. Any second.."

        You forget to mention commercial fusion. I believe it''s still only 50 years away.

    2. MattPi

      Re: "I'm sure that within 10 years we'll see electric airplanes transporting 50 passengers"

      "This experiment requires a 2.3-ton plane with the wingspan of an Airbus A380 to transport 2 guys and 633 kilos of lithium batteries at a speed of max 90km/h. During the night it goes slower to save on energy."

      Luckily, not all flights require flying non-stop from Japan to Hawaii (4300 miles). Maybe, just maybe, they could swap some of those batteries for cargo/people and still do the 200 miles DC-NYC or London-Paris non-stop.

  6. James 51

    I can't remember if I read this in Accidental Empires or Where Wizards Stay Up Late but the author was telling a story about the creation of postscript. He was working with one of the men responsible for creating it. The short version is that the author kept trying to tell the other person that postscript was too complex and resource hungry to work with their computers and printers. It was only years later that he understood the other man's point that there would soon come a time when that was not the case but he had lacked the vision required to lay the foundations for that time.

    1. Chris Miller

      Nice story, but solar cells are not about to follow some version of Moore's Law. Even if you could capture 100% of the solar energy falling on the surface area of an aircraft, you could hardly keep a small Cessna in the air, let alone anything like a 737.

    2. Gotno iShit Wantno iShit

      @James 51

      I see your point about vision but I just can't accept that this technology will be ready in 25 years, certainly not in 10.

      The first flight of a jet pack was claimed in the 1950s and certainly happened (tethered) in 1960. Some claimed we'd all be using them in the future but we aren't. The technology works but only at the bleeding edge. There have been small incremental improvements over the decades but a step change in fuel energy per unit mass is still needed to make it remotely practical.

      Solar powered flight is the same, it works but every component is at the bleeding edge. Incremental improvements are not going to change that. If someone invents solar cells that can harvest 10x the energy for a given area and battery technology with 10x the energy storage for a given mass then it's game on. Incremental improvements every few years are not going to deliver 50 passenger aircraft in 10 years.

      1. James 51

        Re: @James 51

        I agree there is going to be a long lead time but if we don't lay the ground work for replacement technologies we'll never see the improvements which are required. Even if we don't jump straight to all solar planes, they might inform the design of the next generation of planes.

        1. Goldmember

          Re: @James 51

          "Even if we don't jump straight to all solar planes, they might inform the design of the next generation of planes."

          This is the best point about all of this. Large, fully solar-powered planes are way, way off, maybe even an impossibility. But hybrid planes are a more realistic concept. Current planes spend much of their time above the cloud layer and have a large amount of real estate available on which to place solar panels. I can certainly see a future where jet-powered planes take off and reach cruising altitude, where they begin to harvest solar energy. They could then use it to boost engine performance and power the in-flight entertainment systems etc.

          1. Anonymous Coward
            Anonymous Coward

            Re: @James 51

            That may be the key. Keep the entire in flight entertainment etc running of solar and a small battery system. Could it keep weight down? Or is the petroleum equivalent just so much higher density in power storage that it negates any savings in "recharging" mid flight?

            The time the craft spend taxing etc is also one to consider.

  7. alain williams Silver badge

    Was I the only one ...

    to read the headline, pick out 'Piccard' and 'warp drive' and assume that it was a story about Star Trek' ?

    1. Updraft102

      Re: Was I the only one ...

      I think the headline writer meant us all to get it.

  8. Faux Science Slayer

    "Green Prince of Darkness" at FauxScienceSlayer

    Photovoltaic is a crude, one time molecular erosion parlor trick that never recovers 10% of it's initial investment energy. PV produces 1.5 watts per sq-ft at 1.5 volts DC, great for pocket calculator, useless for grid.

    One horsepower is 757 watts, or 600 sq-ft of collector. One horse power is also 550 ft-pounds, the work necessary to lift one cubic foot of dirt, four feet high. Tons of material is mined, refined, shipped, melted for the Silicon, Boron, Phosphorous to make a few solar cells.

    There is NO Carbon forcing, NO 'sustainable' energy and NO 'peak' oil.

    1. James 51

      Re: "Green Prince of Darkness" at FauxScienceSlayer

      NO 'sustainable' energy

      So how long have we got till it's back to the stone age?

      1. Vladimir Plouzhnikov

        Re: "Green Prince of Darkness" at FauxScienceSlayer

        Well, no matter how reluctant I am to agree with FSS but he is right - there is no sustainable energy in the world, in principle. All energy is depleted and turns into entropy. That's why eventually there will be the Heat Death of the Universe.

    2. Richard Hector

      Re: "Green Prince of Darkness" at FauxScienceSlayer

      If you want to fight false science, which is a worthy cause, it helps to understand the basics yourself.

      Horsepower and watts are units of power, not work/energy. "the work necessary to lift one cubic foot of dirt four feet high" is, as you say, work. I guess foot-pounds is a valid way to express that, though joules is less confusable with torque. What you probably meant to say is that one horsepower is 550 foot-pounds per second.

  9. jb99

    Can someone calculate

    Can someone calculate the power output of the engines on a typical 747

    And compare it with the power generated by covering it with solar cells.

    That should give some idea of the energy requirements and how far away they are.

    That ignores the battery problem of course.

    1. TRT Silver badge

      Re: Can someone calculate

      Yeah, but hybrid... every little helps.

    2. Chris Miller

      Re: Can someone calculate

      RR Trent engines >50MW, so a 747 is >200MW max power. Solar cells produce ~200W/m2, so you'd need a square km to power a 747. If you could achieve 100% efficiency at the equator, there's 1300W/m2 of sunlight available compared to just over 500m2 wing area on a 747 and you're still over two orders of magnitude short. Now, about these trans-polar routes ...

      PS Hybrids work in cars, where the additional weight of the battery isn't too crucial to performance - add 20% to the weight of a car and it will still drive (possibly a bit more slowly). On an aircraft every kilo of extra weight is vital - add 20% to the weight of an airliner and it could never leave the ground. Even so, very few pure hybrids achieve better fuel efficiency than an equivalent-sized diesel powered vehicle.

      1. Alan Brown Silver badge

        Re: Can someone calculate

        "very few pure hybrids achieve better fuel efficiency than an equivalent-sized diesel powered vehicle."

        In open road cruising that's true and unarguable.

        For urban warrior work, it's a completely different story.

        The issue with car engines (diesel or petrol) is that they only work efficiently at full load and even than that's only ~35% maximum and only when at operating temperature.

        The average petrol engine runs around 2-4% efficiency most of the time and 0% when idling in traffic.

        Stop/start engine technology has made quite a difference for dense urban traffic fuel consumption but in the suburbs where most runs are less than 2 miles in light traffic you can expect your 50mpg diesel to be making more like 25-28mpg (real world figures) - and BOTH these areas are where hybrids win.

        Using a smaller, lighter engine with more tightly defined operational parameters means you can cut the emissions control weight and complexity too, so there are engine/battery tradeoffs you can exploit for a win-win situation, but don't expect to see many hybrid longhaul trucking rigs. (On the other hand hybrid trucks are ideal for drayage work)

        The further advantage in dense urban environment is that you can switch the engine off entirely and roll on electric power during pollution blackouts, but it's worth noting that London's NOX levels are now only 40-45% caused by vehicle emissions and have been like this for a while (predating Euro5 cars), so you get a law of diminishing returns unless you go after the largest pollution sources.

        offtopic: The largest source of NOX in London is old-school gas and oil-fired boilers and for the most part they're also the largest source of HC and particulate emissions. Modern condensing ones are almost zero emission, which is one of the unstated reasons councils trend to mandate the things but their complexity is the very thing which causes owners of older massively polluting installations to refuse to update (until they get CO poisoning and the system is condemned, as happened to some friends of mine).

        That said - London NOX (and other pollution levels) are only problematic inside the inner london ring road and virtually non-existant outside the North/South circular roads. A lot of automotive pollution control technology is being produced and sold with efficiency and cost penalties everywhere, to nail issues that only occur in small areas when there are probably better ways of tackling the issues, such as adaptive technology which restricts emissions when actually needed or simply mandating zero emission vehicles in zone 1.

    3. JeffyPoooh
      Pint

      Re: Can someone calculate

      "...how far away they are."

      Infinitely far away.

      Electric Aircraft can still scale up.

      Solar powered aircraft are a dead end.

      1. TRT Silver badge

        Re: Can someone calculate

        No seriously. If they can get weight-for-weight equivalent solar cells to aircraft skin, why not make use of them? There's lots of electrics on board a modern aircraft, and there's always the possibility of adding energy into the mix from an alternative source... the turbines on a 787 are started electrically using one of the twin generator sets per engine rather than by a traditional ground based pneumatic system. They're developing electrical alternatives to some of the engine components all the time. So why not do it? It might happen, it might not; that's not to say you shouldn't try.

        1. Alan Brown Silver badge

          Re: Can someone calculate

          " If they can get weight-for-weight equivalent solar cells to aircraft skin, why not make use of them?"

          Complexity, fragility, extra wiring mass and charge control complexity, certification for about as much extra energy as is consumed by the inflight entertainment gear of a half-dozen seats.

          It's much more profitable to reduce seat mass, the weight and power consumption of the IFE kit (which is what's being done) as well as the mass and complexity of aircraft wiring (which is why some busbars and wiring are being run in Aluminium or F/O instead of copper, despite the increased fragility of the former and the extra transceivers for the latter and why switched networks/control busses are proliferating instead of hundreds of miles of individual control/power wires.)

          Seriously. Just the extra wiring for solar panel skins means they'd need to weigh 1/10 of existing skins to be worth replacing on a like-for-like bases.

  10. Phil Parker

    Don't try anything new!

    How dare anyone try something new? We only want tried and tested solutions, none of this new fangled science stuff!

    Unless I'm missing something, this project hasn't cost any of us any money so what's the problem. Maybe something useful will come out of it, maybe it won't. Who cares. At least people are still trying.

    1. Chris Miller

      Re: Don't try anything new!

      I don't think many people are saying that it shouldn't be tried. Like the Gossamer Albatross, it's an impressive piece of technology. It's all the idiots (including many journos) saying "in 20/50/100 years time all passenger aircraft will fly on solar power" in utter defiance of the laws of arithmetic, never mind physics, that are annoying.

    2. JeffyPoooh
      Pint

      Re: Don't try anything new!

      "At least people are still trying."

      Such hyped-up stunts only encourage 'Airhead Environmentalism', an issue vastly worse than the loony 'climate deniers'.

      1. Anonymous Coward
        Anonymous Coward

        Re: Don't try anything new!

        Upvote there on the electricity. We already have them. Electric hobby craft and drones/quadcopters.

        However none of these are solar powered just yet...

        ... with the exception of biofuel, as that is grown via the sunshine! :D

        1. Solmyr ibn Wali Barad

          Re: sunshine

          Moonshine is also produced from converted sunshine.

          /Is it Friday already? Grrr./

        2. JeffyPoooh
          Pint

          Re: Don't try anything new!

          "...none of these are solar powered just yet..."

          You were doing good, right up until the words 'just yet'.

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