Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 18. Low hanging fruit.

April 17, 2020, ©. Leeham News: We continue the summary of the series why e in ePlane should be more about environment focus than electric aircraft.

Last week we summarized the high hanging fruit technologies pursued presently, now we continue with the low hanging fruit.

Figure 1. The Gartner hype curve. Source: Wikipedia.

The low hanging fruit

We summarise our insights from the series with the highest hanging fruit last week and now continue with more attractive opportunities for environmental progress:

  • The lowest hanging fruit of all is the overdue change of our ATC systems. In non-COVID-19 times over 20,000 aircraft fly routes that are 10% longer than they necessary because ATC control is still not using ADS-B technology and what it enables in more direct routes. Air traffic controllers in Europe resist the obvious efficiency improvements of a joint EU ATC using ADS-B as it means fewer controllers can do a better job. Politicians should grasp the rudder now and get this change done. When we had a regular traffic flow, no-one dared pick a fight with the controllers as this would disturb a highly loaded airspace. This is no longer the case and will not be for years. The opportunity for change is now.
  • At the next branches, we find Biofuel where we can gradually blend in more of it in our regular jet fuel supply. Politicians and airliners should join up and get this market going, now that air traffic is down. A functioning and economically competitive Biofuel supply should be a goal as we exit this crisis.
  • The third level contains the “more electric” initiatives that are in development. Turbofans where an in-line starter generator helps with transients, hold a promise of up to a 5% reduction in fuel and thus CO2 emissions.
  • The fourth level from the ground has the more efficient propulsion systems like Open Rotor engines that can give our short-range regionals turboprop efficiency combined with jet speeds.
  • Finally, on a bit longer horizon, synthetic fuels are the key to an efficient energy store for places where the generation of energy and consumption is physically separated. We have no practical way of storing energy today. Synthetic fuels can give us this essential capability, and they make perfect jet fuels.

The above lists the areas where our attention and money should be. For several technologies, this is not the case.

Instead, we have 200 projects chasing high hanging fruit. This is also consistent with the Gartner hype curve (Figure 1), the hyped technologies attract the attention and more realistic approaches are neglected.

 

35 Comments on “Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 18. Low hanging fruit.

  1. Hi Bjorn
    Cool series, just catching up
    A couple remarks on your conclusions here :
    – “More Electric Aircraft” is also hype, for the most part. Especially the “bleedless” flavor. Yes bleed is energy-inefficient, in that fuel is burnt to produce heat which is in a large part directly dumped into the atmosphere by either the pre-coolers or the packs. However, it is a fairly simple system, with simple ducts runnig for short lengths from the engines to the anti-ice and the packs which are both located nearby in the unpressurized areas of the wing & belly fairing. In contrast, a more electric system has these large EM-armored wires that need to run all the way back into the pressurized fuselage to a dedicated power electronics bay and then back out to the anti-ice and packs. The PE components require sophisticated local cooling, and this heat then needs to be evacuated out of the fuselage. The pumps and fans related to this create noise. etc etc… In short, it’s an integration nightmare, which all adds up to a lot more complexity, weight, unreliability, costs. And ultimately, any direct energy efficiency gains of the bleed system itself are wiped out by the inefficient of the integration into the aircraft.
    Hydraulics are a much better target for replacement. They are scattered all over the place (wings, tail, center, nose, cargo doors…), work only in short bursts, in very different phases of a flight mission, contain disgusting fluids and are made of high-grade materials. Once solutions exist with sufficiently high power burst capability, replacing the hydraulic systems with electric ones should enable simplification of the overall aircraft design and indirectly improve efficiency. But that again will not make cool headlines.
    I’d suggest that the best “more electrical” architecture would be to replace hydraulics with electrics, and keep a basic bleed offtake from the engines augmented/boosted by an electrical system. This should also the electric starter/booster you mention

    • Hi Airmagnac, more electric aircraft yes, but the engine side has more promise.

    • Post COVID-19 airlines and aircraft manufacturers must look at reducing pathogen transmission through improved cabin air quality and I suspect that bleed air systems will be found less satisfactory for this.

      We can not afford the risk of such a pandemic ever again. Any recirculated air will need to be filtered to remove pathogens. The air should not “move” any great distance within the cabin through widely separated intakes and outlets.

      Then there is also the issue of turbine oil from failed bearing seals entering the cabin. This is happening even in modern aircraft. Electric pressurisation can eliminate the risk. It is extremely unpleasant that can force an emergency landing and cabin crew have suffered life changing effects which I believe to be genuine. The neurotoxin TMPP is almost always present having formed from over heating of TCP & TCMP friction modification additives.

      Personally I think COVID-19 was spread through the many touch screens and keypads we are forced to use. Self check in touch screens, self scanning passport machines at airports are more guilty. Likewise for supermarkets. This whole vector of transmission needs to be eliminated by the creating of contactless purchases and check in, perhaps via cell phone apps and the NFC device.

      My wife was a high end IT saleswoman specialising in the banking industry. She was very successful. She mentioned that 15 years ago that she was trying to sell bacteriostatic plastic coatings for touch screens, pushbuttons for both customer contact and banking staff. She said that it was extremely difficult to the point of impossible because the issue of pathogen transmission was just laughed of. This is an issue that will need the creation and enforcement of Government regulation and IATA and ICAO standards.

      We are clearly at the point that centralised hydraulic systems could be eliminated through the use of EHA “Electro Hydrostatic Actuators”. The elimination of a complete system usually saves weight so EHA, electric pressurisation and electric de-icing line up.

      When one designs high reliability electrical systems one needs to know what one is are doing, too many people don’t. One needs to be concerned about how much pressure is applied to an electrical contact, the metallic coatings on the wire and terminal itself and their metallurgical interaction, vibration, insulation behaviour when fire is present or oils contact and one needs to understand how to coordinate the electrical system so that upstream over current breakers do not trip before down stream. It’s easy to get working, not easy to make reliable.

    • Agree that the 787 was the first “electric aircraft” and those systems could be designed better and lighter today. UDF’s are progressing in both speed, noice and efficiency but its 140″ fans needs a dedicated airframe that has not been designed yet. An aft body design was part of clean sky2 I think but money ran out

  2. A further remark on the short range aircraft & open rotors :
    Air transport is just one mobility solution among others. If ecology is the final goal, then we need to think about what is the most ecological way of moving from A to B, not focus on marginal reducing the footprint of each possible mean of transport.
    In this case, aircraft are most efficient when cruising at high altitude, not taxiing on the ground or climbing at high power settings. For short hops, surface transport will be ecologically better unless surface terrain is really hostile (seas, mountains). I see much more potential in applying technological research to trains rather than pursuing the decades old Open Rotor effort or the dubious all-electric regional aircraft. Improving how trains can serve the “last kilometer” through usage of autonomous tech, better connections at hubs& rail yards, and less infrastructure-heavy solutions could be a better way to go. And I say that as an airplane guy !

    • We have a large fleet of turboprops serving the world corners where there are no fast trains and the cost of establishing the infrastructure can’t be motivated. There the Open Rotor has the efficiency of the turboprop but increases the speeds to jet speeds for hops up to 1,000nm or more.

    • A modern jetliner uses about 2l per 100 passenger miles. So it is always better to fly over reasonably long distance, say 700 miles. With a modern car two people driving may come close. But if you look at a Greyhound it is not even close. Of course the plane will take about 5 hours or so door to door, the car 9 and the bus 18 or more. Plus if you drive you have a car on the other end.

      So in north America there will be a real temptation to drive over those kind of distances. A train would need to get there faster and be inexpensive enough to offset the extra cab/uber fairs needed to cover not having a car.

      • If you get stuck in traffic jams it ruins the experience,
        so maybe taking your electric car to the train station, hook it up for free charging as part of your train ticket, jump onto the train, plug in your computer, cruise in realistic speed of 100-150mph arrive and jump into a rental electric car, do your meetings, back to the train station valet parking, get onto the train, finish your report, arrive at home station, get into your fully charged car with the AC been running and cruise home. A train Pullman style wagon can easier give you more distance between travellers and a better working cubicle. Still train tracks are not that easy to build over private land and you often dig into historical artifacts getting Indiana Jones &co stopping construction work and start investigate.
        China did not have private land and did not care what Ming dynasty items they dug into…
        Just look how hard times the California high speed rail track building got themselves into.
        The US can in theory renovate its tracks and make it an electric national network with a national train control system but it will not happen unless Warren Buffet decides one morning to do it and buy the remaining large train track owners and throw money on it to bring the tracks/bridges/signal systems to Swiss standards and then start ordering electrical trains and wagons of different styles even borrow some renovated Orient Express wagons from SNCF to let the travellers experience the history and food of earlier times, might be that the train food beats out what United serves on Chicago to Omaha flights…

    • In regards to trains. They are limited solution, some more rail can be built but I fear an economic tragedy waiting to happen of rail is hyped to politician. High speed rail only works in a set of very specific circumstances:
      1 Two very large population centres that are not too far apart.
      2 The two population centres must be of well above average wealth and prosperity in order to be afford the ticket prices and the associated costs. High Speed rail is very nice but simply extremely expensive.
      When the above criteria are not adhered to trillions of dollars can be wasted. All the effort, subsidies represent greenhouse gases as well.

      I highly recommend Visual Politiks recap of the Juan de Mariana Institute study on Spanish High Speed Rail, by far the biggest network in Europe.
      https://www.youtube.com/watch?v=MYWYhPVwJBY&t=127s

      Takeouts are that the network can not pay of the capital costs, can not cover interest costs, can not even cover maintenance and operating cost. The Japanese do not build Shinkansen’s to small regional cities in the hope that it will stimulate them to prosperity. Theirs is a sensible network that runs the spine of Japan and into which lower speed networks feed.

      There may be some breakthroughs. Rail works very well for shipping freight and great gains can be made by facilitating a shift from road to rail unfortunately the speed seems to be 120km/h rather than 400km. Perhaps there will be breakthroughs in rail tunnels, which is what is needed. I rather think that driverless cars and buses that coordinate through traffic without ever stopping at lights may promise a new form of public transport enabled by the smartphone.

      • Rail is expensive because the rail companies need to pay for the rail. The roads are build free for all to use.

        • The small 12m section of road in front of a house or business is paid for by the property taxes of the owner. If the road is a arterial route it is paid for by fuel taxes as well as registration fees paid by vehicle owners. Fees paid by commercial vehicles such as trucks, taxis and limousines can be very high since they are expected to pay for such things as taxi drop of bays, reinforced roads etc. Major motorways are often paid for by tolls especially if tunnels. To seal a compacted road with 4cm of aggregate and 1.5cm of tar is an average of $0.33/square meter per year to install and maintain. If 4cm thick hot mix is used it is about $0.90/sqm/year. Rail can not compete with this except in the case of very heavy axle loads. I suspect the development self driving cars that coordinate with traffic signals will lead to a doubling in road capacity. We need to move to smaller electric cars I admit. I am not against rail, I am against subsidies. It is not a technology that works except in narrow set of circumstances. Complex, labour and maintenance intensive, sensitive to faults it needs a duplication of lines or repeated down time, capital intensive etc.

  3. “Finally, on a bit longer horizon, synthetic fuels are the key to an efficient energy store for places where the generation of energy and consumption is physically separated. We have no practical way of storing energy today. Synthetic fuels can give us this essential capability, and they make perfect jet fuels.”

    We certainly do have the capability, the renewable energy sources in sufficient quantity and the infrastructure to store and transport one synthetic fuel – ammonia.

    It’s not a perfect jet fuel but its better than batteries. See Ammonia Economy on Google.

    Where do you see fuel cells – high or low hanging fruit?

  4. I don’t believe biofuels are the way to go, if food crops like corn are used for conversion to biofuel. The resources used in growing such plants, such as fertilizer and water add to the carbon foot print, not to mention the fact that food needed for a hungry world is being diverted from the poor to make fuel for the rich to travel. The only way biofuel becomes useful is if non-food type plants grown in arid regions are utilized. Biofuels do push the peak oil scenario further into the future and most importantly decrease the wasteful use of hydrocarbons in natural petroleum by burning them away instead of converting them into numerous other worthy products.

    • Agreed with these points. Another issue is the change in the world’s albedo due to land use change when growing in arid regions.

      I also question why now would be the time to ramp up on biofuels? Jet fuel prices are extremely low, air lines have financial worries, and politicians have far more pressing issues.

    • Some cities are starting vertical greenhouses where they grow mainly fresh salads in robotized racks with LED lights. No pestecides and controlled filtered city air get converted into oxygen by the zillions of plants growing. The cost is not on par with free land growing+pesticides+transportation but if it will be issued regulations on supermarkets locally grow some % the vegetables they sell using heated ventilation air out of the supermarkey it will boost city growing.

    • Maize alcohol has a energy gain factor of about 1.2 to 1.8 depending on who you listen too, I tend to believe the lower estimates. The major energy input is not fertiliser and tillage but energy for distillation which in the US comes from natural gas. There is hope that distillation will be replaced with microfiltration, at least to 30% concentration. I have no problem with subsidising European or American farmers a little. It keeps them on the land and keeps excess crop production up. This ensures food security and that is essential. Food waste is insurance, not really waste. We never thought we would experience COVID-19 because we have no living memory of the Spanish Flu epidemic of 1918-20, we also have no experience of famine for 70 years. Famine could still happen. Sugar Cane has an energy gain factor of 5-10 since the bagasse (stalks) can be burned for generation of electricity. Sugar Beet has an energy gain factor of over 2 to 2.5. It is worth growing sugar beat as rotating crop to prevent parasitic rhizomes establishing in the soil from other crops.

      Probably the best energy crop however is biogas. I was stunned at how much there is. Its potential is almost 1 cubic meter of methane per person per day. About equal to 1L of Jet Fuel.

      It is made mainly from waste. Waste is where biofuels shine and do not compete with food crops and nature reserve. Manure, silage from cereals, substandard crop, the stalks of wheat, sugar beet tops and can use factory food waste, milk, whey, grass, pumpkins that weren’t ready for harvest, carcases etc. Anything with starch, sugar, fat protein. If you had a slice of stale bread with 85 food calories (360kJ or 0.1kW.Hr) about 60% of it could be converted to biogas in a digestor. That Scandinavian proposal to convert biogas into FT jet fuel makes a lot of sense. There is a huge amount of domestic and restaurant food waste that goes to land fill rather than a digestor where its potential of biogas is at best 30% utilised. I suspect it would be better for the Americans to put their excess maize corn through a biogas digestor from an energy point of view however ethanol is a superb pollution reducing fuel additive.

      Some other hopes, the development of 3rd generation biofuels that can ferment lignin and cellulose. I think Toyota may have focused on fuel cell vehicles in part because of relative ease of production of hydrogen from biomass.

  5. Bjorn, from what you’ve seen, how many of the 200 projects are designing for something other than Urban Air Mobility? This series has been focused on airliners, but I haven’t seen many electric aircraft projects meant for more demanding missions (>10 PAX, >500 nmi, >200 kt).

    • I would say about 1/4 is aiming at airliners, starting with 12 or 19 seaters, then advancing to regionals and ultimately to single aisles. The UAM market is facing other issues where safety while flying over populated areas will be the major one.

  6. Where you do rank blended wing body and other non-tube-and-wing aircraft forms on the high or low hanging fruit scale?

    • “The third branch from the top holds the different aerodynamic wonders that electric technologies shall enable. We proved they are better realized with existing technologies, present for decades. Yet we have no implementations. Could it be because they don’t work?”-Part 17
      https://leehamnews.com/2020/04/10/33117/
      It was a bit more directed at electric propulsion possible changes but still applies to what you infer.

      • Actually I was wondering about just a “vanilla” blended wing body, with 2 to 4 current-technology turbofans attached above the back of the vehicle, and no additional electric technologies involved. But I guess that would still be considered high hanging fruit, if aircraft with open rotor engines (which could’ve/should’ve entered service 25 years ago) is not even thought of as the lowest of the low fruit.

    • I’ve noticed that Airbus has had a few flying wing to aircraft (as test bed models) in the news lately.

      I think the following is going on:
      Centralised electrical generation by turboshaft and distribution to multiple fans doesn’t really work except, maybe, if one adds a downstream closed cycle Brayton turbine to recover heat energy in the exhaust. That should get efficiency from 40% to 60%. Such systems have been analysed as giving a fuel burn reduction of a few percent in consideration of the increased bulk, drag, weight, lost jet thrust of the system. I suspect the flying wing improves this by allowing more of the bulk inside of the body/wing.

      The above also doesn’t seem compelling however the Solid Oxide Fuel Cell (SOFC) promises 60% efficiency with up to 85% possible if turbo compounded to take advantage of the hot, pressurised exhaust. Furthermore is promises to eliminate nitrous oxide and particulate emissions. If we imagine a 70%-75% efficiency as realisable and accept that although the bulk of fuel cells makes them no better than piston engines in terms of power to weight ratio the use cryogenic hydrogen the system does begin to look compelling due to the reduced volume of LH needed.

      Beyond that there is the possibility of combusting or reacting unusual fuels such as nano metals perhaps with liquid oxygen carried on the flight.

  7. I would like to address synthetic carbon neutral hydrocarbon fuels that would be drop in replacements for existing fuels. Such synthetic hydrocarbon would be vastly superior fuels reducing particular emissions by 86% and NOX by up to 10%.

    I think it is important to start developing this industry by blending in a fraction to existing jet fuels. A 2% addition would add maybe 4.5% to fuel costs and would work synergistically with fuel from biogas. It would not require any further carbon offsetting.

    These start of with both hydrogen and carbon dioxide either captured directly from air or from a concentrated source such as a cement calcination plant or fermentation CO2 (of eg a biogas plant).

    Most folks conceive of the hydrogen production as coming from electricity (wind power) via electrolysis. This unfortunately worsens the tunnel vision trans fixation on “charging the electric car” type solution. There has long been two other sources: thermochemical production and photochemical production.

    Thermochemical hydrogen production originates from nuclear research but lends itself to concentrated solar. Efficiencies at converting concentrated sunlight to hydrogen would be in the range of 25% to 40%, perhaps more since the core process is over 60% efficient. This process bypasses the inefficiencies and capital costs associated with conversion to electricity first. Furthermore it works very well to mix water and CO2 within the thermochemical process to directly produce syngas for conversion into Fischer-Tropsch Jet fuel.

    There production of these electro-fuels completely bypasses the storage and transport problem associated with using sunlight and wind being converted to electricity first. Cheap wind power nearly quadruples in price when the costs associated with transmission, grid stabilisation and utilisation factors are added.

    There are interesting developments. Co-electrolysis of steam and CO2 can directly and efficiently produce syngas. The process is being applied to Nordic Blue Crude’s electro-fuel plant in Norway.

    Amines are one practical route to absorption of CO2 from the atmosphere but they require 2.5kWHr per Kg of CO2 of low grade heat at 90C to regenerate. This is fortunately available from waste heat or heat pumps (COP 3.8 for a 20C->100C increase in temperature)

    Voskian & Hatton at MIT developed a process for extraction CO2 from atmosphere at only 0.277KW.Hr per KG.

    Once this industry gets started the chemical engineering will start to optimise and improve it out of all expectation.

    CO2 can be extracted from air but also sea water (developed by the NRL for the US Navy for jet fuel production aboard aircraft carriers). The technology could open up ‘renewable’ resources hear to unexploitable due to distance such as tidal, ocean current, dessert sun.

    Finally I mention my pet topic. Had we have progressed down the nuclear route the production of synthetic fuels for aviation and hydrogen for decarbonisation of iron smelting etc would already be economically viable.

    The development of a synthetic fuels industry should be encourage with quotas of use by airlines.

    • I agree with the synthesis of liquid fuels approach. Liquid fuels from electricity could be used today’s aircraft without modifying the airframe, the fuel system or the engine – a drop-in replacement, and significantly will enable the existing fleet to become carbon neutral.

      Lazards LCOE https://www.lazard.com/perspective/lcoe2019 shows Wind energy cost at $28-$54/MWh. Jetfuel has a specific energy of 9.6 kWh/L . If conversion of electricity to liquid fuels was 50% energy efficient then the energy cost is $1.04 – $0.54 c / liter. Of course there are other costs, but as mentioned chemical engineers, new catalysts and thermal methods will resolve this.

      I do not agree with the nuclear path however due to the high cost of nuclear electricity – $115-$195 / MWh. Nuclear also has other issues which are off topic.

      It will be a lot easier to develop new processes on the ground than to make a new process, and then make it safe to fly as well – the main thrust of Bjorns argument against flying batteries. Compression and transport of hydrogen comprises a significant part of the end to end efficiency losses and is the reason that hydrogen powered cars will not beat battery cars. The other main obstacle to using hydrogen as a jet fuel are the development costs to make a light and safe leak proof hydrogen tank that can fly and has a 20+ year life without suffering embrittlement.

      • Thanks, I’ve read that Lazard link. It’s good information. However I wish to explain what the “load levelized cost of production” of electrical figures on page 1 mean because they can be very misleading if not understood.

        This also links into how much it will cost to produce electro fuels from these sources.

        The load levelized cost of production is simply the average cost of producing electricity including capital costs, construction costs, maintenance, operating costs and decommissioning including interest rates and inflation. It is usually done with an NPV “Nett Present Value” analysis.

        However it is very misleading number. This is because the dominant costs in getting electricity to the consumer is now the network. In the case of renewables the network is probably 3 times more expensive. Turbines have spinning reserve from the inertia of the rotor, energy in the magnetic field of the generator, steam reserve and the ability to dispatch 50MW/sec into a fault until it clears, compensate instantly for collapse of a transmission line or generator or power factor issues. In the absence of this enormous sums are spent in upgrading networks. Renewables are also ‘surgy’ and only use the transmission intermittently (less than 50% in the case of solar). Page 5 of the document gives the cost of electricity if it were battery backed, you need to add that to solar or wind. And you will also likely still need peaking plant. This is why countries with ultra cheap wind power also now have ultra expensive electricity.

        Im my view wind farms and solar farms should not be connected to the grind unless they can provide 1 hour of battery backed full power generation. In Ireland despite 12% of their energy coming from wind their CO2 emissions went down only 3% due to the inefficiency of starting peaking plants. Warm up issues, problems with rotor bowing etc.

        If you build a 10 million PtL power to liquids plant say capable of absorbing 12 MW of power and generating 1 ton of fuel per hour the solar power plant will likely only be used to 40% of its capacity due the diurnal cycle. The nuclear plant will not suffer from expensive and long transmission lines and it will allow the plant to be 100% utilised. Nuclear in the USA is 50% more expensive due to legal costs and delays and a lack of standardisation of designs.

        Giant offshore windfarms seem to have capacity factors of 63% however and floating wind farms maybe more. So this may be quite a promising avenue to have giant floating wind farms generating Jet Fuel, OME, Diesel etc.

        I’ve done a crude analysis which shows that had we not have installed wind turbines with peaking power turbines and instead combined cycle power plants that there would now be both cheaper electricity and less CO2 emissions. GE and Siemens turbine business is in trouble and I fear we will not see a new generation of gas turbine with 70% efficiency.

        In terms of the fuel cell car. The fuel cell car and the battery car are complimentary. The fuel cell car is already cheaper than the battery car to make (MIRAI). I suspect a network of fuelling stations will be set up based around electrolysers with compressors. These will absorb cheap power when it is most available. I suspect some will have a fuel cell to feed power back into the grid and be able to earn money by acting as ‘peaking plant’. However making hydrogen in say the Australian dessert and transporting it cryogenically can power a fuel cell car. When the LH achieved ambient it will be at 70MPa so no compression losses. Hydrogen can also be made efficiently from biomass.

        The idea of charging a battery car over night from a central battery storing energy is another expense as is the reality that outside of Norway electric cars are still mostly powered by gas turbines at this point. BEV need to be plugged in all day during the day to be efficient.

        • Key point to the topic at hand is that synthetic liquid fuels produced from carbon neutral electricity were not discussed during the series, or they were, and I missed it. My limited understanding is that these synthetic fuels may be an ideal match with existing gas turbines and, if supply were available, could be integrated quickly at 100% rather than blended. I am curious to hear if this has been tried / tested.

          Many decades of engineering research has gone into gas turbines, they are well optimised at the limits of materials and engineering. Gas turbines solved the reliability issues of reciprocating engines – but they don’t scale down very well so piston engines are still used in cars. This means cars are both inefficient, complex and unreliable making them low hanging fruit to convert to electric. Bjorn has explained the engineering challenges with converting aircraft to electric motors – its not impossible but there are better ways to spend money that will have a greater positive impact.

          Fully appreciate the cost of running a grid is more expensive that the cost of generation. The cost of wholesale power is a fraction of the cost of integration and supply to a house or business.

          You mention this in your reply, but choosing a non-integrated power price was intentional because I believe that synthetic fuels will be created from renewable electricity generation not integrated with the grid, agree that this may be supplemented with overflow when there is a power surplus. Producing hydrogen from water can be done with variable output, as can other parts of the process. Capacity factors do vary widely, but this doesn’t need baseload power, just power to make fuels that can then be used in jet aircraft – as you described a “drop in replacement”.

          This is not to under-estimate the challenges associated with this. It is important to seek the low-hanging fruit on all different trees; replacing EOL fossil fuel plant with alternatives that are more efficient and have a lower carbon footprint will likely have more significant benefits that taking a highly efficient gas turbine and fueling it with carbon neutral fuel!!!

          We have limited resources and need to get the best return on the investments made – this might not be replacing fuels in aircraft, but replacing coal power plant and car engines.

          • Vastas have had a number of floating 8.5MW wind turbines of the Portuguese Coast for several years now. If they achieve a capacity factor of 60% for an average output of 5.1MW we could expect over 333 Litres of fuel at a modest 60% efficiency per hour. This works out at 8000L/day. The fuel capacity of a basic A321neo is about 24,000L so one would expect to need to install 3-6 such wind turbines to keep an A321 flying. The wind turbines would still be cheaper to purchase and install than the aircraft, less than $15 million each I suspect so the economics will stack up. The biggest wind turbines conceived may be 100MW hurricane proof units, they would produced about 5000L/hour or 120,000L/day. Enough to fuel an A350/B787. I’m assuming the fuel is produced on board the wind turbine but it could be transmitted to shore using the HVDC.

  8. Sticking my neck out I think the next big step using ‘fruit’ that can be picked will be by Boeing.
    They will need a gov’t bail out.They will not be allowed to use it to buy Embraer.( probably don’t want to anyway now).
    The MAX remains in awful trouble as the grounding passes the key 1 year mark – the cancellations are coming in thick and fast and won’t stop.
    Some have even questioned the commercial viability of the 777x project.
    If they are to stay in the game they have to develop a 737 replacement starting in perhaps a year or so.
    One aircraft has repeatedly come to the surface from the origonal SUGAR programme with NASA.Indeed it has recently had a new improved variant shown.This is the high wing TTBW.
    https://www.boeing.com/features/2019/01/spreading-our-wings-01-19.page.
    It’s massive aspect ratio with a think laminar flow wing offers up to 15% increase in efficiency with body/ materials improvements.
    They are also actively involved with GE/Safran/MTU on the UHBP engine for which a demonstrator is due soon ( note Airbus has also expressed interest in this engine in preference to the OR version) it too offers up to 15% improvements.
    Together it will offer a 20-25% improvement over the best of today. With an equal reduction in emissions.Perhaps the final word in a fossil fuelled ( or synthetic) aircraft.
    Imho Boeing will do this.It will render the A320 obsolete along with the two new Russian and Chinese aircraft.
    It’s a huge throw of the dice but it’s perhaps that moment.

    • I also like the Boeing SUGAR, still it needs its $bn’s to go from preliminary design and working with FAA/EASA for the new systems needed (fly-by-wire flutter control?) with test rigs, production automation development and new engines. The US goverment could enforce Boeing to do it if it wants goverment money as it don’t seem to have the guts to bet the company on a radical new aircraft as in the old days.

  9. Bjorn, I was wondering about your thoughts on active winglets as a method to improve airliner efficiency? I’ve seen some trials on a CJ-Citation that allow extended wings with fewer losses. The active winglets are supposed to help optimally tune the wing loading.

    • Active winglets is a good idea, especially for retrofit to already made designs (as it doesn’t increase the structural stresses above the original stresses).

      If you make a clean sheet design you have to weigh the gains of the active winglets against their increased complexity (they have active parts like actuators that require maintenance). There a raked wingtip or normal winglet might be a better solution, it requires a detailed analysis for each case.

      • That makes sense. The active incremental benefit is offset by the added complexity over a passive design.

        I saw the technology is being marketed to the military as a retrofit for cargo planes, for economy and range extension, but also to relieve wing stress and fatigue.

        Thanks Bjorn!

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