Electric commercial flight - Page 1
Forum section: electronics / general

author: Rx7man
author_rank: Regular Contributor
timestamp: October 27, 2020, 10:21:34 pm
content: I'll put this here since I don't really know which other place to put it, I didn't see an EV specific forumDo you think long range commercial flight is possible? I know there are small flights that have been done with electric airplanes, but between take-off power requirements, flight speed, elevation, quick turn around times, and long distances, I don't see airliners becoming electric and economically viable for a very very long time (IE, when there just are no fossil fuels available at all)I saw Airbus was experimenting with the E-fan X, the closest thing to an airliner I could find, they only used 1 of 4 as an electric (2MW) engine, and the project is scrapped according to their site.. I found all sorts of fancy videos with dramatic music and wind tunnel testing of an existing airframe (really pretty pointless I'd think), but no numbers.I've got an argument going with a Green party MLA

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 28, 2020, 01:25:32 am
content: Look up the amount of energy which may be stored in one kilogram of your favorite battery technology. Compare it to the amount of energy which can be stored in a kilogram of jet fuel.They're nowhere close.My sources say Lithium-ion batteries are around 90 Wh/kg, while jet fuel is around 12000 Wh/kg. That's more than two orders of magnitude difference!It's true that efficiencies will vary, and the weight of required motors versus jet engines aren't equal, and an electric plane must carry its batteries for the entire flight, while a fuel-burning plane keeps getting lighter during flight as fuel burns. Battery technologies are improving, but jet engines are also becoming more efficient. These are all trivialities in the face of the two orders of magnitude difference.Weight is all-important in air transport. Around 45% of the takeoff weight of a modern long-haul airliner is fuel. If you want to carry the same energy in the form of lithium-ion batteries, the first approximation would say that the plane must weigh around 45 times its current weight, just to hold the batteries. But a plane that weighs 45 times as much as a current airliner will require a lot more energy in order to reach its destination.Maybe electric power will someday play a part for certain very short flights. But it will not be practical for intercontinental air transport any time soon.Note that this doesn't imply we must continue burning petroleum to fuel aviation. We could synthesize hydrocarbons using other energy sources.For fun, estimate the wattage required to refuel an airliner during a one-hour ground stop.

author: Cerebus
author_rank: Super Contributor
timestamp: October 28, 2020, 03:38:49 am
content: Any long range commercial airflight is either a very long way off, or would look very different.There are three possibilities as I see them.Air liners that operate in a very similar fashion to the ones with which we are familiar. Within this category there are two possibilities, pure electric vehicles using batteries or hybrid ones using fuel cells and still requiring energy dense fuel.To operate commercial craft in the way they are now but using batteries requires a huge improvement in specific energy density (W/kg) for reasons that have already been pointed out (based on currentbestLithium battery technology versus kerosene the improvement required is about 50 fold).The second option is fuel cell operated aircraft and that currently comes down to using hydrogen as fuel. There's no hydrogen infrastructure, and it would have to be developed worldwide, and there would be a significant acceptance barrier to it - mention 'hydrogen', 'aircraft' and the next two phrases you will hear from people are "Hindenburg disaster" and "R101 crash on maiden flight".The third possibility would involve a significant change in the way that planes operate. All the really successful battery based electric aircraft so far have been essentially powered gliders. Upscaled, these could achieve useful commercial ranges withrelativelymodest improvements in battery technology (say 20 times better specific power density)butthey would be slow compared to current aircraft, would require very different airports, would have much more restrictive weather conditions they could operate in and would have to take indirect routes while the pilots hunted for thermals during the parts of the flight where they essentially operated as gliders and consequently would have estimated flight times rather than schedules. Might be quite a nice way to fly though - quiet, unrushed, scenic. Probably still only ever practical for medium rangeover land.Any option involving batteries requires either massive or phenomenal improvements in battery technology. This will not happen within 20 years, it might not happen in 100, it might not happen at all. However, the push towards this will continue as improvements in battery technology are useful in themselves. The hydrogen fuel cell option requires worldwide coordinated changes in infrastructure, if people will accept it. Moving to powered gliders changes just about everything associated with air travel as we know it, planes, infrastructure, speed, somewhat indirect flights and still requires a massive improvement in batteries to be practical.Conclusion: It's not happening in my lifetime, it's probably not happening in my  children's lifetime. Perhaps there will be short haul (~100 nm) electric commercial flightjustwithin my lifetime.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 28, 2020, 05:51:29 am
content: Quote from: Cerebus on October 28, 2020, 03:38:49 amThere will certainly be improvements in battery technology, but they'll never come anywhere near the energy per unit mass of hydrocarbon fuels. The reason is chemistry.Batteries require an oxidation/reduction reaction, and the battery must contain both the oxidizer and the reducing agent. Burning hydrocarbons also involves an oxidation/reduction reaction, but the airplane can get the oxidizer from the air, so doesn't need to carry it along. And it dumps the products of the reaction overboard as (polluting) exhaust, so it doesn't need to carry them to the final destination. These two facts give burning hydrocarbons a huge weight advantage.The chemicals that provide the best ratio of energy to mass are the lightweight elements near the top of the periodic table, like Hydrogen and Lithium. Nobody is going to invent new elements in that part of the periodic table. There may be some new heavy radioactive elements synthesized near the bottom of the periodic chart, but those large nuclei give them terrible energy per unit mass during chemical reactions.You also mentioned fuel cells. They have the same problem as batteries that they must carry both their fuel and oxidizer. You correctly observed that hydrogen is the ideal fuel for a fuel cell as far as energy per unit weight goes (hydrogen is right up at the top of the periodic table), but hydrogen isn't nearly so spectacular if you consider the total weight required to contain it in a tank at a reasonable volume. You can store it cryogenically or compressed, but either of those options involves tankage that weighs more than the fuel. The space required for storing hydrogen at a reasonable pressure leads to a voluminous aircraft, which doesn't work out well as far as aerodynamic drag. Plus, hydrogen embrittles metal, and because the molecules are so tiny, hydrogen leaks through seemingly solid metal tanks.The easiest way to tame hydrogen for practical transportation is to combine it with heavier atoms to turn it into a relatively dense liquid. Carbon works nicely for this purpose. And that brings us back to liquid hydrocarbons, the fuel with the best ratio of energy per unit mass, when you account for both the mass of the fuel and the mass of the tanks to safely transport it.I wish it were different, because I'm very much aware of the downsides of hydrocarbon fuels. We must get away from mass emissions of CO2, or at least if we continue emitting CO2, we must capture CO2 elsewhere so that our net emissions become zero or even negative. That's why I think long-haul aviation will eventually move to using renewable energy to synthesize hydrocarbon fuels, for net zero carbon emissions.There may be other possibilities for the distant future, such as nuclear powered aircraft, or using hyperloop-style long vacuum tunnels instead of airplanes for long distance transport. Those have very serious practical engineering problems, of course, and I don't expect to see them become practical in my lifetime, but it's easier for me to imagine something drastically new like that than it is to imagine long-haul aviation being propelled by chemical batteries providing power to electric motors.

author: Rx7man
author_rank: Regular Contributor
timestamp: October 28, 2020, 07:31:51 am
content: Thanks for all the replies, I'd used most of those arguments against this guy and he's just so convinced technology will get us there, And yes, someone came up with the nuclear battery, posted a link to some magazine or something that boasted this incredible energy density, but the prototypes were in the micro to milliwatt rangeThe only reasonable battery powered air travel I can think of is a zeppelin style as the buoyancy of the aircraft doesn't require fuel, the problem then is a long haul flight will take a week!I don't think commercial air travel will continue forever, I think high speed rail will be more like it anywhere it's possible, and the cost of air travel will make a lot of non-essential travel cost prohibitive.. This is of course way in the future.. that's my 2 cents, coming from canada where we don't even have pennies anymore

author: Rx7man
author_rank: Regular Contributor
timestamp: October 28, 2020, 07:37:54 am
content: Quote from: Cerebus on October 28, 2020, 03:38:49 amI think Harbour Air is operating a modified Beaver on electric-only from Vancouver BC to Victoria, I'm not sure if it's truly commercial or for private use, it seems to me the FAA certs to do it carrying the public would be onerous to get.Electric cars already have pretty poor ranges, we can't make a cell phone that works a whole day on a charge.. I'm not hopeful we'll do trans-atlantic commercial flights on the scale we do today powered by electricity

author: Cerebus
author_rank: Super Contributor
timestamp: October 28, 2020, 02:08:04 pm
content: Quote from: AG6QR on October 28, 2020, 05:51:29 amMy only quibble with what you said is with the above. Most fuel cells in current use don't use a supply of stored oxidiser but simply use atmospheric oxygen. There's an experimental fuel cell bus trolling somewhere around London (just checked, route RV1) that's hydrogen and atmospheric oxygen powered. In fact I can't think of any hydrogen fuel cell application that used stored oxidiser that wasn't in a space vehicle.

author: Cerebus
author_rank: Super Contributor
timestamp: October 28, 2020, 02:20:12 pm
content: Quote from: Rx7man on October 28, 2020, 07:31:51 amPossibly a bit of an exaggeration. The Hindenburg took three days to travel from Frankfurt, Hesse, Germany to Lakehurst, NJ, USA, and that against strong headwinds, before it gave Herbert Morrison rather a lot to say on the radio. How the power to weight problems of doing this with batteries would slow it I don't know, but I suspect the issues are considerably less than those for heavier than air aircraft.

author: Cerebus
author_rank: Super Contributor
timestamp: October 28, 2020, 02:42:57 pm
content: Quote from: Rx7man on October 28, 2020, 07:37:54 amThat's, what, 50 miles in a straight line with a six passenger seaplane? That's a route that, were it over land, nobody would consider flying. I must confess I didn't think about island service when I set my benchmark (although it was somewhere at the back of my mind*). It does present a realistic commercial opportunity for electric flight, but it's not going to make a dent in terms of passenger miles even if every island service in the world converts to fully electric. I was thinking more along the lies of a full-sized plane on a route like London->Birmingham (UK obviously) where there flying might seem frankly a bit silly, on a route served by motorways and a main train line, but there are nevertheless scheduled flights daily.I had a search for the flights in question and it looks like this is still at the trying to get approval stage. They've got a plane, they've run test flights and I can see lots of re-hashed press releases for that, but none for having got approval.* I had the "World's shortest scheduled air flight" in mind, Westray to Papa Westray in the Orkneys - 90 seconds from take off to landing.

author: Rx7man
author_rank: Regular Contributor
timestamp: October 28, 2020, 05:07:43 pm
content: I just pulled a number out of my arse for the flight time on a zeppelin style craft... even if it's 3 days, taking a week vacation means you only spend a day at your destination... it's hardly going to be attractive for anything other than deliberately sightseeing on the tripI also agree that short hop flights like Vancouver-Victoria isn't going to make a dent in emissions from air travel... It's only good for the politicians that have to go to victoria (BC's capital) and gain greenie points

author: ve7xen
author_rank: Super Contributor
timestamp: October 28, 2020, 09:15:04 pm
content: Quote from: Cerebus on October 28, 2020, 02:42:57 pmI don't even think they're at that stage yet. They've done some test flights, but I think it is still proof-of-concept and they need to flesh a lot of the details out before it's time to approach Transport Canada for approvals.As to the topic in general, Airbus seems to be pursuing the hydrogen option, with 3 hydrogen-powered concepts revealed just last month:https://www.airbus.com/newsroom/press-releases/en/2020/09/airbus-reveals-new-zeroemission-concept-aircraft.html. I assume (maybe naively) that they have done sufficient basic engineering that these concepts are fundamentally viable. How ready / willing the market is to trust hydrogen fuel, and build the necessary infrastructure is another question entirely...

author: nightfire
author_rank: Frequent Contributor
timestamp: October 28, 2020, 09:45:42 pm
content: The interesting idea is IMHO to explore the world of propeller-based Aircraft again. A Turboprop-based Aircraft has a better fuel efficiency than a jet-based one due to various reasons- and if you don't need the speed of the jet, in lots of scenarios a prop-plane is just fine or "good enough" for the things it has to do.This mainly involves short-distance flights and usage as a cargo hauler.So someone has to explore the idea of electric flight, and later on the best of both worlds can be combined: An electric concept with batteries enough to have maybe 30 mins of flying time, that also provide the huge energy boost needed for takeoff, and some generator/fuel cell that will provide energy in-flight for maintaining level.With this concept a plane could use hydrogen oder maybe some synthetic fuel produced with renewable energy.

author: tszaboo
author_rank: Super Contributor
timestamp: October 28, 2020, 11:09:57 pm
content: Quote from: Rx7man on October 27, 2020, 10:21:34 pmCO2 + H2O + Energy = CH4 + O2CH4 as we speek heats millions of houses everywhere around the world.There are 28 millions cars converted to it."The Boeing SUGAR Freeze airplane concept looks at many advanced technologies which combine to provide over 70% reductions in Carbon Dioxide emissions. It is an example of a partially turbo-electric architecture. This plane uses liquid natural gas instead of jet fuel, and generates electricity in flight by integrating a solid oxide fuel cell with the turbine engine. The electrical energy is then used to drive an aft propulsor at the tail of the plane in order to energize the boundary layer and reduce drag."

author: Cerebus
author_rank: Super Contributor
timestamp: October 28, 2020, 11:37:30 pm
content: I'm not quite sure what you're trying to say here."Liquid Natural Gas" is a fossil fuel. The methane used to heat millions of homes is fossil fuel. A tiny proportion is biogas from fermenters. There is no technological process for turning CO2+ H2O + energy into methane without involving good old fashioned agriculture and rather a lot of waste along the way. We're running out of land for agriculture to feed people, we certainly can't afford the land to make enough methane to keep the world's planes in the air, homes heated and so on.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 29, 2020, 01:47:37 am
content: Quote from: blueskull on October 28, 2020, 03:09:18 amAbsolutely.And to begin with, I don't know if people are really aware of the amount of thrust a conventional turbojet engine is able to generate. I'd be curious to see a similar electric engine generating as much thrust while being reasonable in terms of cost and weight.Then there is of course the point of storing energy. AG6QR gave the figures. No need to go any further. We can always dream of the better battery that is going to happen, but hey. Unless we go for fuel cells of some kind, I don't think we'll be able to increase the energy density of a battery that much more. I'll be happy to be proven wrong in the future though. And fuel cells, you guessed it, will rely on some fuel, so that's just displacing the issue.There is a current trend in thinking one alternative to batteries would be to store energy as a "carbon-free" fuel like hydrogen. Except that producing hydrogen takes electricity (back to blueskull's point), and the process is not much efficient either. But even so, I'm not sure converting hydrogen to electricity via some kind of fuel cell and use electric engines would make much sense. Wouldn't using hydrogen directly to power engines be more efficient? So, that still wouldn't be electric flight.As I see it, unless we find the miracle solution, this is a dead-end. At least for the time being.But since for that to really happen and not be useless, we would need means of producing huge amounts of electricity in a clean way, and since we are still very far from that goal, I think that is what we should focus (and invest) on. Not on building electric planes that make no sense at the moment. Because THAT is, IMO, actually the easy part.

author: ve7xen
author_rank: Super Contributor
timestamp: October 29, 2020, 02:36:35 am
content: Quote from: SiliconWizard on October 29, 2020, 01:47:37 amWe're going to need to make our electricity production systems renewable too, regardless of what we do for transportation, and this is a relatively 'solved' problem at this point, just requiring investment. It's also much easier for governments to subsidize / force progress there than the tragedy of the commons. It's a similar situation with EVs, and I don't really think this is a great argument against it. Hopefully any new production that is built to support increased EV use or hydrogen-powered aircraft would be renewable. Scale usually leads to improvements in efficiencies too. It seems like the most efficient way to transport large quantities of renewable energy at high enough density might be breaking water with it and storing the hydrogen.The Airbus initiative is based on burning hydrogen in turbines similar to existing turbofans, and using fuel cells for the plane's electrical requirements. Having an electrical propulsion system I guess is probably not feasible given the power demands and weight of the equipment required to produce that much power in a fuel cell; maybe efficiency too.QuoteWe should be tackling all these aspects of the issue simultaneously. Electrifying things makes them 'automatically renewable' once the infrastructure is in place. It's a slow process on both sides, and there's no reason at all to do it serial rather than parallel. Airbus is targeting 2035 for commercial availability, it's not like they're selling them today. As long as we continue burning jet fuel, we're doing nothing about the contribution of air travel at all. It's also probably an improvement even with fossil electricity generation, shifting the relatively dirty small-scale burning in the engines to larger, more efficient plants that can afford the weight of emissions controls, centralizing the output for carbon capture, etc. - in addition to the fact that >25% of global electricity is renewable today, and will certainly be more then.It's far from useless to pursue this avenue, if it's viable. The alternative is simply that air travel will become completely unaffordable.

author: tszaboo
author_rank: Super Contributor
timestamp: October 29, 2020, 07:47:28 am
content: Quote from: Cerebus on October 28, 2020, 11:37:30 pmOf course there is>https://www.storeandgo.info/demonstration-sites/germany/

author: sandalcandal
author_rank: Unknown
timestamp: October 29, 2020, 12:47:08 pm
content: Quote from: Cerebus on October 28, 2020, 11:37:30 pmThere has been since 1897https://en.wikipedia.org/wiki/Sabatier_reactionAlso not keen on "over population, running out of land" outdated alarmism. Definitely aware of running out of historical energy resources and ever increasing energy demand + climate change but over population and food supply (apart from instability due to climate change) is not a current issue everywhere apart from Africa. Getting off topic though.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 02:51:22 pm
content: Quote from: sandalcandal on October 29, 2020, 12:47:08 pmName a commercial plant using it, producing gas for sale (or even on-site use) at a cost equivalent from buying it from normal sources and in commercial quantities. It has to be a practicable process, not merely possible, that operates economically at the scales of current and proposed world usage. One assumed that an intelligent person would take that as read in the circumstances under discussion. And where does one find a convenient source of concentrated CO2that isn't a plant burning fossil fuel to produce energy, a cement works, a brewery or a similar primary user of either energy or biomass? One might like to examine the thermodynamics of the first listed to figure out why that isn't a runner for practical purposes.Quote"Running out of" isn't the same as "have run out of" so saying it isn't acurrentproblem doesn't solve the issue, we are discussing thefutureof aviation, not thenow. You might not be "keen on it", personally I loathe the idea, but it is unfortunately true. Just look at these two graphs (fromhere) and tell me where the land to grow fuel crops will come from.Add population growth:If those three put together is not a disturbing trend then I don't know what is. Adding more land use for mass biofuel production on top of that would be a farcical idea.Remember that all this started with someone trying to convince a "Green party MLA" that [implicitly Green] electric aviation isn't a realistic possibility at current scale for aviation, that the waving of a technological magic wand won't solve the problem. Aviation is only responsible for 2.5% of global CO2emissions but is still growing along with all the other sources. One can't look atjustfinding replacement energy sources for aviation, it won't happen in isolation. If we, say, move to massive production of biofuels for aviation won't we also have other uses for those biofuels, won't we want to produce biofuels for road vehicles, home heating and all the other uses? One has to consider the big picture before one can say that one has a realistic solution. Here, the big picture says that biofuel production for aviation isn't the solution.Further, any claims that synthetic methane production is a feasible alternative on this scale are also unrealistic. One only has to factor in the energy cost of obtaining CO2from anywhere other than existing concentrated sources that all use either energy or biomass. Any diffuse source of CO2would be energetically uneconomic. It's more "let's wave a technological magic wand and it'll all go away" thinking that the first mentioned Green party MLA is guilty of. As engineers and scientists one hopes that we are above pinning our hopes on that kind of thinking.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 03:08:28 pm
content: Quote from: NANDBlog on October 29, 2020, 07:47:28 amWhich has produced "about 192.000 kWh" in "the run time of the project" (1186 hours = 49 days 10 hours). That's the equivalent of about 16 tonnes of kerosene, 19,919 litres of Jet-A1. The fuel capacity of a Boeing 737-200 is 22,596 litres. So that plant in its lifetime hasn't even produced enough fuel to fill a 737-200once, energetically.I'll say the same thing that I said above: "It has to be a practicable process, not merely possible, that operates economically at the scales of current and proposed world usage. One assumed that an intelligent person would take that as read in the circumstances under discussion."Edited to add: The plant in question used grid electricity and the feed gas CO2was from a bioethanol facility. The overall power-to-gas efficiency was 56%, and I couldn't find a figure for the ultimate land use to produce the CO2.

author: sandalcandal
author_rank: Unknown
timestamp: October 29, 2020, 03:13:17 pm
content: Quote from: Cerebus on October 29, 2020, 02:51:22 pmThe point was a counter to the claim:Quote from: Cerebus on October 28, 2020, 11:37:30 pmYou might say you meant it differently but anyone reading it could take that to mean it just doesn't exist not it doesn'tpracticallyexist.You can go start a new thread somewhere else if you really want to discuss population and land use.Edit: I mostly saw that one point above that was patently false, I don't have much to comment on otherwise for the main subject.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 03:37:34 pm
content: Quote from: sandalcandal on October 29, 2020, 03:13:17 pmReally? The context is evident from the discussion. One shouldn't need to spoon feed people every obvious qualification and exception. This is just a discussion, not a formal presentation for the public, one can hopefully presume a certain degree of 'smarts' and willingness to debate honestly from one's audience, one shouldn't have to be wary of wilful misinterpretation.QuoteNo thank you, I don't want to have a general discussion about those, but one can't ignore them and develop a magic strategy for "greening" aviation in glorious isolation. I don't really believe that you are incapable of seeing that or realising that one has to be discussing solutions that are both practicable and practical at scale rather than theoretic solutions here, but perhaps I overestimate you.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 29, 2020, 03:45:55 pm
content: Quote from: ve7xen on October 29, 2020, 02:36:35 amIs it? Really?

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 03:59:02 pm
content: Quote from: SiliconWizard on October 29, 2020, 03:45:55 pmSolved? No. But as doubly qualified as "relatively 'solved'", in context, possibly. C'mon lets admit some subtlety on his behalf here.

author: sandalcandal
author_rank: Unknown
timestamp: October 29, 2020, 04:19:55 pm
content: CerebusI don't disagree entirely. "Practical" electricity->fuel is problem that has not been solved and will need to be solved if hydrogen, methane or "renewably powered" aircraft are to be feasible. I'm not aware of any "practical" electric aircraft systems currently realised. However, there are options with potential merit that could be developed into. There are challenges with H20+CO2->methane systems which you've partially pointed out correctly but saying there are none then leaping back to saying there are some but they aren't practical is the point of brining up the actual existing solutions and developments. Even if they aren't 100% efficient does not mean that they do not have a net benefit.Again, I don't agree that land availability is a problem. The problem is is sustainable and efficient land use. On the same site you've linked data from there's strong data showing the improving efficiency of land use:https://ourworldindata.org/crop-yields#the-trade-off-between-higher-yields-and-land-useHonestly, I hope this isn't you but the only people I see peddling "Not enough land! We're all full!" are xenophobes trying to use sustainability as an excuse for their cultural intolerance which is why it drew my attention.Edit:How do I scale the image? lolEdit2: used [img width=700]

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 29, 2020, 04:34:09 pm
content: Quote from: Cerebus on October 29, 2020, 03:59:02 pmI dunno, maybe. But in the context talked about here, which is generally speaking, drawing ever more electrical power than we currently do, then it's definitely unsolved.And I personally still do not agree with the fact working on all fronts at the same time makes sense. Even basic project management principles are supposed to teach you that. Handling the hard tasks first is usually what's most efficient in the long run, and focusing on smaller tasks is only going to take away precious time and money.Some of the "green-minded" people who advocate electrifying everything are still aware of that, and are mostly pushing electrification projects (such as electric vehicles in general) as a way to push the world to massively invest in clean electricity production. I admit that's not a completely bogus approach. But it's, at the very least, overly optimistic. As we need more electricity, we're likely to cover the new needs on the short term with old and proven solutions rather than invest more in clean solutions for long-term results. This is what is already currently happening, as we may be constantly talking about green electricity all over the place, but we are still building more coal-based power plants all over the world.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 04:50:40 pm
content: @scandalscandal - to avoid indulging in mega-quoting.The problem there is that improved agricultural efficiency has come with costs, both energetic and environmental. I don't propose to go and dig out figures, but the production of fertilizer comes with energetic and environmental costs, the mechanisation of agriculture ditto, there's biodiversity costs (which could decimate agriculture itself if it leads to collapse in populations of pollinators), intensive agriculture leads to pollution and so on.Pointing at figures that show increased agricultural production per unit areafor cereals(and there's no doubt that has happened) as if that's the solution implies that is sustainable. It is not. There is obviously a ceiling that can't be broken through - there's a physical density of crops versus available light and water that has to be reached at some point - moreover at some point the plants won't have physical room to grow. (Edited to add:) In the news at the moment is the seed of a war, as Ethiopia and Egypt start arguing over access to water from the Nile for both power and agriculture.What this all runs up against is the old phrase "limits to growth". We keep on using more and more resources. As we run into availability problems in one area (CO2sink capacity of the atmosphere, fossil fuel reserves to name some) we pursue technological solutions that press resources in some other area (water, land, mineral reserves to name some). What no one wants to accept is that the only overall sustainable solution is "use less". For air travel that means less air travel for pleasure (take a boat instead), less air freight (wait a few weeks for your package from wherever, don't eat out of season fruits and vegetables flown from Peru to England). We can wait hopefully for some unrealistic technological miracle or we can do something practical and realistic now - "use less".

author: sandalcandal
author_rank: Unknown
timestamp: October 29, 2020, 05:47:27 pm
content: Quote from: Cerebus on October 29, 2020, 04:50:40 pmThen we agree the core problem is not fundamentally land availability but rather increasing efficiency, controlling wasteful demand and developing sustainable practices? Biofuel sources that have been presented are based on harvesting from existing activities, they don't use more land, they capture more output from it. (Corn for ethanol is an entirely different matter)The apparent problem you raised of food security as a function land availability is a fallacy, food production is clearly not driven by land use. Hyper efficient indoor factory farms are definitely a thing that seeks to solve the problems you mention with ability to use vertical space and reducing the distance of production->consumption. The overriding factor in increasing food production is greater efficiency through improved practices. The greatest threat to food production is climate change as you have provided an example of with water availability along the Nile.https://theconversation.com/in-the-future-there-will-be-more-rain-but-less-water-in-the-nile-basin-129360As much as there are "limits to growth" in our ability to better exploit land there are also "limits to growth" in human population and that can be clearly seen in the human population graph you posted with the precipitous drop in population growth rate and levelling of the world population.

author: Rx7man
author_rank: Regular Contributor
timestamp: October 29, 2020, 07:06:08 pm
content: I cannot fathom how growing indoors is going to be more efficient, you need light, and where is the power for that light going to come from? Solar panels? Why not plant the crops outside and skip the losses? It might work alright for leafy greens, but there isn't a snowflakes chance in hell you'll actually feed people that waySame argument can be used for electric flight that's powered by dirty energy sourcesdI don't think the electric motors needed for flying a big aircraft is an insurmountable problem.. powering them is

author: sandalcandal
author_rank: Unknown
timestamp: October 29, 2020, 07:27:48 pm
content: Quote from: Rx7man on October 29, 2020, 07:06:08 pmhttps://www.eevblog.com/forum/renewable-energy/vertical-farming-and-other-high-tech-agriculture/new/#new

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 07:40:09 pm
content: Quote from: sandalcandal on October 29, 2020, 05:47:27 pmHow apposite that you use the word "fallacy" while claiming by implication that land use is not driven by food production by saying the exact converse. No of course "food production is clearly not driven by land use" it's the other way around. This is getting a bit silly.Meantime relying on vertical farms for food production is almost literally building castles in the air, especially if your vision for them apparently uses no extra land. Presumably they hover somewhere over the sea. Where do all the materials and energy for building and vertical farms come from? Resources of course, and we're back to those being limited. Vertical farms are fine for garnish, for salad crops, but ruddy useless for subsistence crops or crops suitable for biofuel production.C'mon do you think we were all born yesterday and can't spot argument for argument's sake? I find it hard to believe that anybody with a sincere interest in the outcome would drag the argument down this alley.

author: ve7xen
author_rank: Super Contributor
timestamp: October 29, 2020, 07:44:10 pm
content: Quote from: SiliconWizard on October 29, 2020, 04:34:09 pmIt is solved in the sense that we have the technology to generate the electrical energy required without ongoing CO2 emissions. There are many solutions to this - hydroelectric, wind, PV, geothermal, nuclear... I'm not sure why you're arguing this. The problem here isn't a technical one, it's one of inertia, investment, and to some extent social (particularly with hydro that displaces people / ruins agricultural land, and nuclear that has lots of FUD surrounding it). From media reports at least it seems that we're near an inflection point where renewables are becoming cheaper too, at least in the developed world, though I haven't looked into that in depth enough to really trust it.QuoteThe tasks themselves are orthogonal and not significantly tied. Only their impact on global CO2 emissions is somewhat related. The engineers at Airbus have next-to-no influence on pushing authorities to deploy renewable energy production more widely. If anything, it would help accelerate those efforts to tie the greening of aviation to the greening of electricity production. There is no advantage to delaying the development of electricity->fuel systems for powering aircraft until the whole world is powered by renewable energy, yet it would certainly slow down the greening of that industry to wait before you're happy with the proportion of renewables in the energy supply (what is your threshold for this being worthwhile, anyway?) before starting the 30+ year project of developing and certifying new aviation technologies such as these.QuoteWe are still building more coal plants around the world, yet the proportion of renewables continues to increase year over year.Since you seem to need more convincing, I also don't think anyone expects this tech to replace traditional aviation overnight - the Airbus concepts are fairly short range. The proportion of renewables is fairly regional, and many jurisdictions have commitments to reach 100% renewables by 2050 or sooner, so by 2035 when these things are optimistically expected to be available, they better be well on their way. So they buy them, and places where coal is still the primary source don't.You could also 'just' have governments force airlines to buy clean power / equivalent offsets, which would help drive investment.

author: hendorog
author_rank: Super Contributor
timestamp: October 29, 2020, 07:56:27 pm
content: Quote from: AG6QR on October 28, 2020, 01:25:32 amMetal air batteries have theoretical energy storage much higher than lithium ion.Still very much theoretical, but in the ballpark.Someone will bring up that Thunderbolt did a debunking if metal air. Frankly that video was unconvincing click bait.Of course it may never be practical/cost effective when compared to the alternative. But it may be possible. Open minds required here. Recharging for example might be done quickly chemically or with a battery swap.The net effect of air travel on climate change is apparently about 3.5% of the total human causes, so I'm not sure that justifies the massive change required.

author: sandalcandal
author_rank: Unknown
timestamp: October 29, 2020, 08:40:00 pm
content: Quote from: Cerebus on October 29, 2020, 07:40:09 pmDon't start trying to BS formal logic. The exact converse of "food security is a function land availability" is " land availability is a function food security" where as "food production is clearly not driven by land use" and "food production" being equivalent to "food security" is used to imply that "food security is a not a function of land availability". There's no converse statement, it is an assertion of the negation. What I should have said is "food security is a function land availability is a false statement because the negation is true (food security is a not a function of land availability)".The point of bringing up vertical farms is that even "at some point the plants won't have physical room to grow" and "out of season fruits and vegetables flown from Peru to England" aren't absolutes. I never said we should rely on them because I doubt we will ever will due to themassive waste presentand many other areas for potential improvements.Quote from: Cerebus on October 29, 2020, 07:40:09 pmYou want to spin it like that?I had two beefsQuote from: Cerebus on October 28, 2020, 11:37:30 pmandQuote from: Cerebus on October 28, 2020, 11:37:30 pmWhen have I strayed away from trying to demonstrate those points? I see two erroneous claims that are demonstrably false and I've put up evidence and information to disprove them while you try to drag it on with anecdotes and idle speculation.Are you sure you're not just trying to have the last word when you have nothing more to say? I has hoping to find consensus with you but it's clear to me now you don't have good will.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 09:02:22 pm
content: Quote from: sandalcandal on October 29, 2020, 08:40:00 pmNo, I'm quite happy to let you have the last say and make whatever claims you like about what I've said. It's on the record, people can read it and judge for themselves what is fallacious and what is not, I feel no need to add another datum, riposte or argument.

author: tszaboo
author_rank: Super Contributor
timestamp: October 29, 2020, 10:32:37 pm
content: Quote from: Cerebus on October 29, 2020, 03:37:34 pmThis is a demonstration site. First I wanted to link a 40 Million EUR P2G facility that is being built in Germany.But now I realize, it doesnt matter what I would've linked, you are just here to pick fights, and I'm not interested in that.This shit is not just a fad that is picked up because it is trendy. There is nothing trendy about big industrial chemical plants, that's why nobody is talking about it. But the technology can be used to reverse global warming, just by using CO2 from the air to run the process.

author: PlainName
author_rank: Super Contributor
timestamp: October 29, 2020, 10:35:23 pm
content: QuoteI thought you two were having a discussion. Didn't realise you were actually playing to the gallery.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 10:38:29 pm
content: Quote from: dunkemhigh on October 29, 2020, 10:35:23 pmI wasn't, but one is always conscious that it's a public discussion.

author: sandalcandal
author_rank: Unknown
timestamp: October 29, 2020, 10:41:20 pm
content: Quote from: dunkemhigh on October 29, 2020, 10:35:23 pmAh yes, nothing quite as addictive as validation from random internet strangers...

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 29, 2020, 10:56:17 pm
content: Quote from: blueskull on October 28, 2020, 03:09:18 amNever heard of jet engines being that efficient, last I checked they were in the 40-50% range.Quote from: Cerebus on October 29, 2020, 02:51:22 pmLook at all the yards doing nothing useful. (Some are used to grow food but I'd imagine that's likely single digit percentages in terms of area.) Biofuel crops can grow in a lot of places, even where the soil is too polluted for growing food.That said, biofuels from ocean algae would probably be easier to scale up.QuoteGoes to show how inefficient factory farming really is and why we should be replacing it with sustainable farming. Factory farming also makes near ideal conditions for bacteria and viruses to multiply and potentially become particularly dangerous ones (for example, MRSA and other antibiotic resistant bacteria), but that's for another discussion.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 11:42:16 pm
content: Oh for *** sake NANDBLog, let me fix that that quoting for you so it makes some sort of sense.Quote from: NANDBlog on October 28, 2020, 11:09:57 pmQuote from: Cerebus on October 29, 2020, 03:08:28 pmQuote from: NANDBlog on October 29, 2020, 10:32:37 pmNow *that* is in order and makes sense:My frustration is with you just handwaving and effectively saying that some technological process for producing methane will solve the problem, and not saying it very clearly at that. You start out with an unbalanced chemical equation for reforming methane and say that methane is used for heating millions of homes and that there are 28 million cars converted to use it. As if getting from the formula to heating all those houses and fuelling all those cars on reformed methane is trivial. There's a bit more to it than that.Then we have a pilot plant, running at 56% energy efficiency using grid power. That's fine, its experimental, who cares where the power comes from for the experiment. But it uses a potted source of concentrated CO2that's derived as 'waste' from a bioethanol plant. The energy costs (and other costs) of that CO2stream aren't factored into 56%. Even if it was, this process that will require a net supply of 1.8 times as much energy as we're currently using in methane form a solution at all? Doesn't increasing power generation capacity at all sound more like a problem than a solution? They're claiming a likely efficiency of 69% for a scaled up 5MW plant, so that figure will fall to a mere input energy multiplier of 1.45, still not a figure that makes one feel sanguine is it? And the costs of acquiring CO2feedstock are still not factored in.What is so difficult in understanding that while these pilot plans are all very interesting, they aren'tthepractical solution in the short term, and may not be in the long term?Quote from: NANDBlog on October 29, 2020, 10:32:37 pmYou can't "just" use CO2from the atmosphere without incurring massive energy costs. CO2is around 400ppm of the atmosphere, 0.04% - converting that into a concentrated 100% CO2feedstock isn't trivial. Whatever way you do it will incur a huge energy cost, concentration with zeolite type concentrators, compressing air to the point where you can extract liquid CO2, or some other method. If you know of a technology for cheap, low energy CO2concentration from atmospheric air, please do tell.These plants won't reverse global warming. I wish they would, but they won't. The energy budget for doing it from atmospheric CO2is huge. There's the biological capture and then fermentation routeen routeto producing a fuel. But that uses energy, and land. Where do you get them?The solutions are not technological. Technology will not save us this time. It might make fixing the problems easier, perhaps less painful, but it won't fix things on its own. You sound as if you think it's all fixed, and we just have to wait for the research projects to finish and the full scale plants to be built and then it's "problem solved".If you think that it's about point scoring or picking a fight you're wrong. It's about the complacency that so may engineers exhibit that "Don't worry, technology will fix it". Keep believing that and it's what they'll have to write on mankind's, or at least civilisation's, gravestone. Engineers ought to be the people capable of seeing the flaws in the technological "quick fixes", capable of realising that it's a massive systems problem, not just producing the next generation of products (or whatever metaphor you prefer for looking at parts of the puzzle, but not the whole problem). And don't get me started on the so called 'engineers' who can't, or rather refuse to, even see that there's a fundamental problem of global warming staring us in the face here.

author: Cerebus
author_rank: Super Contributor
timestamp: October 29, 2020, 11:49:20 pm
content: Quote from: NiHaoMike on October 29, 2020, 10:56:17 pmThat's the kind of thing that really scares me. "Look, OK, we've messed up the ecosystem by messing with the atmosphere, let's fix it by fiddling with the Oceans".We've messed up big time by not understanding what we were doing to the atmosphere, and that was pretty much accidental. Are we really so knowledgable about the effects of messing with the Oceans that it's a safe thing to contemplate deliberately doing? I think not somehow. Every time I hear someone mention "ocean seeding" as a method of carbon capture I start to acquire a nervous tick.

author: tszaboo
author_rank: Super Contributor
timestamp: October 30, 2020, 09:34:53 am
content: Quote from: Cerebus on October 29, 2020, 11:42:16 pmOn some high level thinking, it doesn't matter, what is the efficiency of these plants. If the power->CH4-> power cycle is only 60% so be it. It only means that we need to install more solar panels. It's the total investment cost that matters.And that the technology gives reason for all parties to invest in this technology.I'm sure that fir the first decade or so, we could just carbon capture the CO2 outputs of existing power plants. Since power plants could sell CO2, they will have a reason to capture this, instead of releasing into the atmosphere. Also it reduces their cost with carbon credits.There are already times, when solar panels generate more electricity than needed. Solar inverters actually shut down in these cases, because the voltage on the network increases and they are not supposed to work when the output voltage is too high. The price of electricity in these times is actually negative, so any industrial process you do, will generate income for you. These times will be more and more frequent.There is always market for methane. It can be stored cheaply, with existing technologies, in bulk. There are countries that store months of their methane needs. This is a technology that we can actually build up for scale, unlike all the other proposals. Like seriously, are we going to place several powerwalls in every house, and everyone change to an electric car? We could convert half the existing car fleet to use LNG or CNG, and make it CO2 neutral. And it costs 1000-2000 EUR/car, unlike buying an electric car for about 40000.It is the perfect middle-ground solution for the next 20-30 years. You have to understand that any solution that we want to do has to be financially acceptable for everyone. We cant ask countries like China to scale back, they are just not going to do it. But if you start buying CO2 from them, they are going to do carbon capture.

author: sandalcandal
author_rank: Unknown
timestamp: October 30, 2020, 11:36:02 am
content: Quote from: NANDBlog on October 30, 2020, 09:34:53 amI want to support and add to that. Solar for energy capture doesn't need to be 24/7. Solar can be installed in non-arable land. Solar PV is more efficient than photosynthesis in terms of energy production.QuoteXin-Guang Zhu, Stephen P Long, Donald R Ort,What is the maximum efficiency with which photosynthesis can convert solar energy into biomass?,Current Opinion in Biotechnology, Volume 19, Issue 2, 2008, Pages 153-159, (http://www.sciencedirect.com/science/article/pii/S0958166908000165)Most sources quote practical efficiency closer to 1%Edit:"solar energy conversion efficiencies for crop plants in both temperate and tropical zones typically do not exceed 1%"Blankenship, Robert E.; Tiede, David M.; Barber, James; Brudvig, Gary W.; Fleming, Graham; Ghirardi, Maria; Gunner, M. R.; Junge, Wolfgang; Kramer, David M. (2011-05-13).Comparing Photosynthetic and Photovoltaic Efficiencies and Recognizing the Potential for Improvement. Science. 332 (6031): 805–809. doi:10.1126/science.1200165This has turned into (or probably always has been) a discussion on solar to fuel conversion.A 2017 overview of Solar to Hydrogen here:https://link.springer.com/article/10.1007/s40243-017-0088-2Very recent (Sept 2020) paper on Solar to Hydrocarbon.A.C. Lourenço, A.S. Reis-Machado, E. Fortunato, R. Martins, M.J. Mendes,Sunlight-driven CO2-to-fuel conversion: Exploring thermal and electrical coupling between photovoltaic and electrochemical systems for optimum solar-methane production,Materials Today Energy, Volume 17, 2020, 100425 (http://www.sciencedirect.com/science/article/pii/S2468606920300447)In response to some people suggesting biological solar to fuel generation methods, I'd say such processes appear to be immensely inefficient.

author: Cerebus
author_rank: Super Contributor
timestamp: October 30, 2020, 01:27:59 pm
content: Quote from: NANDBlog on October 30, 2020, 09:34:53 amThere you go again: "Itonlymeans that we need to install more solar". There is a cost in resources, materials and energy to make those solar panels. That has to come from somewhere. It's no good examining this stuff in isolation - one must think about the costs as part of a whole system.QuoteMethane reformation as a battery during times of solar overproduction? OK, that actuallymaybemakes sense as an energy storage medium. As long as you understand that there has to bemore than three timesas much energy available to to do the reformation as the plant produces for consumption (pesky thermodynamics, reformation is hoped to be 67% efficient at scale, natural gas generating plants are 45% efficient, coal 32% [Source: EIA]). And obviously as soon as that stored energy is released, its CO2is back in the atmosphere.The questions to ask on that are: Does it use less or more resources than making batteries to do the same job? Does it result in a net CO2reduction overall or just flatten the growth curve a bit, remembering that fossil fuel is still being burned, moving carbon from the ground to the atmosphere? Is there enough 'green' electricity overproduction to practically support it? If it does produce enough gas to produce a net CO2reduction is there a practical way to store that gas?To use a metaphor it's clearly a temporary dressing, not a cure. Is it a big enough temporary dressing for the size of wound, or is it a band aid on a gushing chest wound? Just looking at that 3x energy multiplier for reformation without adding any of the other resource costs, I suspect that it's a non-runner.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 31, 2020, 01:12:13 pm
content: Quote from: AG6QR on October 28, 2020, 01:25:32 amWhy would you compare these? I mean, these are secondary, or internal parameters. Raw materials that don't get you anywhere. There iscorrelation, but the matter is greatly oversimplified.The simplest flaw in your comparison is ignoring efficiency completely. Instead of comparing:E_density_jetfuelvs.E_density_batteryyou would need to compare:Eff_jet_engine * E_density_jetfuelvs.Eff_electric_enginer * E_density_battery.OK, getting better. Better as in, closer to the truth instead of an agenda.Then again, why would you only count the weight of the fuel? While some parts of the aviation system are (mostly) energy source independent (like wings, flight surfaces, etc.), some parts exist solely for that particular fuel system. So instead of comparing:weight of fuelvs.weight of batteriesas a denominator in energy density, you should use:weight of fuel + weight of jet engines + weight of complete fuel systemvs.weight of batteries + weight of electric engines + weight of complete power delivery and management system.and NOW we are gettingsomewhere.The result is likely the same, with electric not being viable especially in longer routes for quite some time, but the storymightget more interesting for very short hauls, which are relevant in Europe. Might, as in, it does in my quick&dirty napkin calculations. Do the math for yourself and see. For some weird reason, Europeans routinely travel some 500 kilometers using flights instead of building a system of cheap, fast and reliable train network like seen in China or Japan.QuoteYou have some interesting sources. I mean, this number would beliterallyfrom very early 1990's, with the very first commercial li-ion cells and packs by Sony.Even as an individual, you can easily buy cells easily exceeding 250Wh/kg and I'm sure 300 Wh/kg is available to those inside the industry. The error here is already almost half an order of magnitude.Your "two orders of magnitude" becomes approximately one order of magnitude after correcting for the trivial shortcomings. Which is still a lot, but the difference might not be even an order of magnitude when looking at very short hauls, where different aspects get a much higher coefficient of interest, for example:* taxiing consumption* engine and fuel system weight you have to carry around all the time (the exact same argument that you have to carry around batteries!)You can make any point with the numbers, and your conclusion will be likely correct anyway, but try to be mentally honest.

author: Clear as mud
author_rank: Regular Contributor
timestamp: October 31, 2020, 01:30:57 pm
content: I happened to see this in a recent issue ofDiscovermagazine:The Other Solar Power: How Scientists Are Making Fuel From Sunlight and Air.It mentions a couple of other demonstration plants that start with the same basic reaction being discussed, take CO2 and H2O, add energy, get methane; which then can be converted to other hydrocarbons through the addition of more energy. The difference here is these projects are getting the energy from the sun directly, instead of the power grid. I realize it may be impracticable to scale these up to anything truly useful.

author: Rx7man
author_rank: Regular Contributor
timestamp: October 31, 2020, 06:34:33 pm
content: true, an entire system analysis really needs to be done to get the whole picture, I'm not sure how the weight of the power control systems, motors, etc will compare for electric, but delivering 10MW isn't going to happen with 10ga wire.. and if google steered me wrong when I searched for energy density on them, I'm sorry.. However, a conventional aircraft still gets lighter and thus more efficient as it flies, and this isn't insignificantI think for short hops it will be become viable to use electric, I really doubt it for trans-atlantic and similar long haul flightsAlso Europe does have a pretty darned good electric rail system, especially compared to north america.. I know you can get pretty much anywhere in Switzerland quickly and efficiently on rail, Japan seems to be really good as well.. North america is essentially in the 3rd world on this

author: Siwastaja
author_rank: Super Contributor
timestamp: October 31, 2020, 06:57:11 pm
content: Quote from: Rx7man on October 31, 2020, 06:34:33 pmItispretty good AFAIK, but looking at the horrificresultof everybody flying so much, it's evidentsomething'snot right. I don't know what and it's beyond the scope of this thread.You know, with all that security theatre at the airports, flying short hauls isn't that quick or fun, the average speed (accounting for travel-to-airport, security theatre, board the plane, taxi, takeoff...) remainswellbelow that of Asian bullet trains of 1980's.But theremustbe a reason why people fly the short hops over the continental Europe. And this could be rectified.But, electric aviation is one interesting option if the root cause for having to fly such stupid short hops over the continent can't be avoided. Once you can design the plane for a range of some 1500 km max, (some 1000km actual + 500km safety for holding and going to alternative airports), the numbers for actual energy density are quite different than those calculated for 5000km

author: Rx7man
author_rank: Regular Contributor
timestamp: October 31, 2020, 08:37:48 pm
content: Just a thought, but perhaps it's partly because of booking systems.. If you're going to fly anyhow might as well fly all the way.When I was a service tech that went around north america, I actually preferred booking to the small airports close to where i had to be, not to save driving, but because the security theater on small airports that only had one or two flights per hour was much easier to deal with.. if you were there 1 hour before your flight you were fine, unlike big airports where you HAD to be at least 2 hours early

author: tszaboo
author_rank: Super Contributor
timestamp: October 31, 2020, 10:19:57 pm
content: Quote from: Rx7man on October 31, 2020, 06:34:33 pmVisiting my parents would be 22 hours by train or 2 hours by plane. With a plane I can literally spend a weekend with them, 4 country away, leave friday from work, take the early monday plane. Well, I mean normally, not in 2020. Also if you have to go anywhere by train, it is going to cost you an arm and a leg, or you have to fiddle around when you are travelling, or buy like 5 tickets with separate passes for different countries. And DB being DB.I really think regional turboprops are going to kill long distance trains completely.

author: PlainName
author_rank: Super Contributor
timestamp: October 31, 2020, 10:37:07 pm
content: QuoteTrains are massively overpriced. For Xmas dinner with an acquaintance (not this year obvs) we would travel around 50 miles into Central London. Worked out that the petrol cost plus congestion charge plus rip-off NCP parking around Piccadilly Circus was cheaper than the train fare, and I got to go and leave when I wanted, door to door. And that was for one - there are actually two of us so the train fare would be twice as expensive as being more expensive. Plus the rip-off car park price at the rail station...I can't imagine anyone in their right mind using a train unless... well, can't think of an overriding reason. They'd have to not just pay me to do it by pay me a lot.

author: Rx7man
author_rank: Regular Contributor
timestamp: November 01, 2020, 02:23:38 am
content: Quote from: dunkemhigh on October 31, 2020, 10:37:07 pmbut could you fly there instead?I don't know exact costs, but i think at least in switzerland you can get a go-anywhere pass with unlimited usage.. same with japan

author: PlainName
author_rank: Super Contributor
timestamp: November 01, 2020, 02:52:34 am
content: If I could fly I'd pay double, and not care about the security timewastingA daily pass wouldn't help - it's a single (OK, two, since it's a return) train journey. Plus things like daily passes don't cover outside of London. There are season passes but we are talking a huge amount of money for one trip, so that's hardly appropriate.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 01, 2020, 06:48:46 am
content: Quote from: Rx7man on October 28, 2020, 07:37:54 amElectric cars have improved a lot, but, I agree, aren't quite there yet."Dumb phones" can last several days---- it is all the "smartphone" overheads that both use up power & require larger screens, limiting battery size that limit the latter.I have a PC & an iPad, it seems silly to buy a phone which duplicates their capabilities at the expense of compromising the core function of a phone.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 01, 2020, 06:58:48 am
content: Quote from: Rx7man on October 28, 2020, 05:07:43 pmIn some countries (like mine) in 2020, you better count on 14 days quarantine at your destination------maybe they'd let you off with 11, if you "quarantine" on the "Zeppelin!"

author: PlainName
author_rank: Super Contributor
timestamp: November 01, 2020, 07:06:49 am
content: QuoteFor the iPad maybe, but I ain't lugging a PC around with me just so I can use a dumb phoneActually, before the iPhone that's pretty much what people wanted to do - have a PC in the pocket. Hence WinCE and all that followed, which was essentially a Windows desktop in a pocket. The iPhone showed that it wasn't the PC we wanted but the potential provided by a PC - the ability to do 'smart' things on the go, as opposed to taking a desktop simulacrum.You might find that most people use their phones mostly for non-voice call things, and some have simply replaced the PC with a phone. Phones aren't really phones now - they are mobile computers which can make calls too. And, in fact, with a lot of IoT stuff you simply cannot use your computer with them - the phone is the only way to control or access them.As such, I don't think the phone is duplicating much if you look at the detail rather than the superficial birds-eye view.

author: mzzj
author_rank: Super Contributor
timestamp: November 01, 2020, 08:10:15 am
content: Quote from: blueskull on October 28, 2020, 03:09:18 am80+ efficiency is the "propeller" efficiency alone. Multiplied with the thermal cycle efficiency of the motor (around 50% for current jet engines) you have about 40% overall efficiency.Electric motor could have 80%*95% = 76% overall efficiencyhttps://en.wikipedia.org/wiki/Propulsive_efficiencyThis lists GE90 turbofan efficiency at 36%https://web.archive.org/web/20161124123017/http://adg.stanford.edu/aa241/propulsion/sfc.htmlStill doesn't change the fact that batteries are the weak link with electric flight.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 01, 2020, 10:00:56 am
content: Now the question is, whatwouldbe acceptable battery energy density for viable air travel?I'll just throw two numbers from the top of my head:Short hauls (continental Europe & similar, 1000km range): 500 Wh/kgLong hauls (5000km range): 1000 Wh/kgCurrent li-ion state-of-the-art is at 300Wh/kg and advancing at about 30%-40% per 10 years. If there is absolutely no breakthroughs but the current slow but non-meaningless progress keeps on, we are there in 2040 for short hauls and 2060 for long hauls.I remember hearing from sources I don't offhand remember that li-ion would top at around 400 Wh/kg, after which something else is needed. The current technology is approaching this. OTOH, the transistors still keep shrinking by (approximately) Moore's law, despite everyone, experts included, saying that it can't go on for much longer, for many decades now, so as a result, I take expert opinions about approaching hard limits "soon" with a grain of salt.For long-range above-the-clouds flying, a sudden breakthrough in solar paler efficiency could enable extending the battery range by utilizing solar charging, but I guess this would also require a technological breakthrough which isn't in horizon. But it's an interesting thing to speculate.

author: Cerebus
author_rank: Super Contributor
timestamp: November 01, 2020, 11:18:32 am
content: It's probably easier, and safer, to make predictions about the chemistry of batteries than it is to make predictions about the peculiar (in both senses) physics of very, very, very small transistors.

author: sandalcandal
author_rank: Unknown
timestamp: November 01, 2020, 11:55:46 am
content: Quote from: Siwastaja on November 01, 2020, 10:00:56 amWhat are you basing this on? Not that you're far off. Quick research on this subject puts the required breakeven starting at 400kWh/kg for smaller personal aircraft, 750Wh/kg for regional jetsSource:Venkat Viswanathan: Batteries: The Missing Piece for Sustainable Transportation and AviationMarch 2018, College of Engineering, Carnegie Mellon UniversityThe above seems to be partially based on this very good NASA study on electric aircraft and their challenges."This issue has been somewhat discussed in the prior portions of this paper, with the projection that a 400 Whr/kg battery specific energy density is sufficient to enable meaningful electric and hybrid-electric aircraft."Mark D. Moore and Bill FredericksMisconceptions of Electric Propulsion Aircraft and Their Emergent Aviation MarketsJanuary 2014, NASA Langley Research Center Hampton, VA, United Stateshttps://ntrs.nasa.gov/citations/20140011913Key points made in the conference paper are:The Design of Electric Aircraft is Different than Existing AircraftElectric and Conventional Propulsion ShouldNOTbe Compared on an Isolated Propulsion System Basis to Achieve Fair ComparisonsElectric Aircraft Make Financial Sense more sense than Electric Cars [in 2014]Electric Storage Energy Density is not THE Issue, or Insufficient for Meaningful RangeElectric Aircraft Research ShouldNOTFocus on Large Commercial Transports with a Market Introduction 20 Years from NowNote: the paper writes statements of the above in a different but equivalent form as negations of misconceptionsI'm working on some first hand back of the envelope calculations to see for myself but I'm no aerospace engineer. I'll post whatever working and results I get when I'm done.I'm not going to be able to do any better modelsEdit: From Oct 2019 report on battery technology developments by the Rock Mountain Institute.Tyson, Madeline, Charlie Bloch.Breakthrough Batteries: Powering the Eraof Clean Electrification. Rocky Mountain Institute, 2019.https://rmi.org/wp-content/uploads/2019/10/rmi_breakthrough_batteries.pdf

author: mzzj
author_rank: Super Contributor
timestamp: November 01, 2020, 12:39:13 pm
content: Quote from: Siwastaja on November 01, 2020, 10:00:56 amMid sized jet like 737 burns abts 2500kg jet fuel per hour. Lets say 4000kg for 1000km flight? 12kWh/kg, 50% efficiency = 24000kWh battery needed as replacement. With current li-ion tech that is 72000kg battery.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 01, 2020, 12:48:52 pm
content: Quote from: Cerebus on November 01, 2020, 11:18:32 amLikely, yes.One reason the transistor predictions failed is because the chip design experts, even transistor experts, had no deep understanding and vision about photolithography processes and probably thought that the wavelength of visible light is the "hard limit".Battery chemistry predictions could fail due to a similar reason: having even a single false assumption.But the observed rate of progress is much slower for li-ion energy density (approx 30-40% per10 yearsas I said) than it has been for number of integrated transistors (some 40% peryear).But we'll see. It's a fact that a lot more money is going in battery R&D than ever before, and it's likely sooner or later we see some minor or major breakthrough. But it's best not to hold your breath while waiting, let alone believe each press release.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 01, 2020, 12:57:51 pm
content: Quote from: sandalcandal on November 01, 2020, 11:55:46 amMy 500 Wh/kg and 1000Wh/kg numbers? Well, just intuition. Have done some literature research about it; have given it a thought or two; have done some quick napkin calculations just for fun. Napkins are in waste bin. Doing aproperscientifically valid, even remotely so, analysis with sources would be work forat least 100 hours. I like doing such quick&dirty "expert intuition" things even on subjects where I really am not an expert (but which might coincide with expertise I have, such as li-ion battery technology and electric motor drives).Where I base "currently 300 Wh/kg" and 30-40%/decade numbers? Observations of actual market of cellsI can buy.45-gram 3.65V 3.5-3.6Ah 18650 cells are currently available from Samsung, LG and Panasonic; have been for a few years now, this is 290 Wh/kg for 2018 off-the-shelf. I'massumingeven more modern cells such as ones developed by Tesla now easily hit 300Wh/kg.30-40% increase per decade can be observed if you look at past products. My observations are some 160 Wh/kg in 2000, 230 Wh/kg in 2010, and 300 Wh/kg in 2020. This is not very precise, though, because COTS cell launch dates are difficult to find, especially retrospectively.QuoteSounds like something I could agree with.

author: PlainName
author_rank: Super Contributor
timestamp: November 01, 2020, 03:56:20 pm
content: The mistake y'all are making is trying to have batteriesemulateoil-fueled systems. That's like trying to have a computer emulate pen and paper instead of having it's own paradigm.So, back to the drawing board, and the problem is you only have enough energy density for shortpoweredflight. Ergo, the answer is to have much moreun-poweredflight. BFO railgun at the start, sub-orbital mid-flight and you can use your Amazon powerbank to go around in case your first landing glide fails. The real breakthrough is going to be in acceleration couches (and maybe in-flight waste disposal).

author: sandalcandal
author_rank: Unknown
timestamp: November 01, 2020, 04:31:36 pm
content: Quote from: dunkemhigh on November 01, 2020, 03:56:20 pmYou're either trolling or going really off the rails there.

author: PlainName
author_rank: Super Contributor
timestamp: November 01, 2020, 05:48:21 pm
content: https://en.wikipedia.org/wiki/HumourA bit of fun can often be a bit of fun. Trolling is malicious.

author: sandalcandal
author_rank: Unknown
timestamp: November 01, 2020, 06:24:24 pm
content: My bad I thought you might have been serious.

author: tszaboo
author_rank: Super Contributor
timestamp: November 01, 2020, 10:35:56 pm
content: Quote from: mzzj on November 01, 2020, 12:39:13 pmYou can also calculate with about 2.5L kerosene/seat/100km. For regional flights on the more modern 319neo and similar planes. But if you compare this to a car, it uses less than a car with a 1-2 passengers. And planes dont have the issue like cars, that they have to be small and have to handle well.But then the plane lands. And you need to charge it up. Planes dont make money on the ground, so better do it fast. There are 500.000 Airplanes / year on Frankfurt airport. That's more than 1000 / day, or 62/hour. Counting with 65/ hour, that is 1500MW continuous charging. That's about 2-3 nuclear reactors operated next to the airport.And you need to have the same charging facilities at remote locations, or they cannot accept electric planes. How are you going to convince the companies, that are hanging by a thread, with minimal margins defaulting in 2020 to install all this infrastructure? Who is going to do it first?

author: mzzj
author_rank: Super Contributor
timestamp: November 02, 2020, 03:48:07 am
content: Quote from: NANDBlog on November 01, 2020, 10:35:56 pmNo need to go that far with the speculation. 737 with 72000kg battery is not able to get off the ground. 80000kg maximum take-off weight, possible battery weight could be something like 20000kg. Still would need about 4x improvement even for short flights.Slow the planes down and make them more like gliders would help but then it is not any faster than train.

author: mzzj
author_rank: Super Contributor
timestamp: November 02, 2020, 12:00:42 pm
content: Further "back of the envelope" numbers: Li-ion batteries cost at the moment around 200 usd/kWh.737 24 MWh battery pack would cost 4.8 million USD with a maybe 500 flights per battery pack. (you can currently forget about Tesla-like battery lifetime in a airplane where battery weight is extremely critical and every discharge is going to be nearly 100% capacity)Battery cost 48 usd per passenger per 1000km flight. Jet fuel at current prices would be 20 kg per passenger and 7 usd.Costs (and big part of natural resource use) are obviously somewhere else than jet fuel.

author: sandalcandal
author_rank: Unknown
timestamp: November 02, 2020, 12:22:58 pm
content: Those seem like bad assumptions.Quote from: mzzj on November 02, 2020, 12:00:42 pmI can't imagine planes literally being completely flat as they land, a significant safety margin is clearly required. The lifetime-cost is also greatly improved for moderate penalties to energy density which is something anyone seriously considering such a system would take. I'd see a penalty to specific energy of 30% as reasonable but assuming 100% DoD is completely out.Quote from: mzzj on November 02, 2020, 03:48:07 amAlso the comparison of fuel vs. battery weight alone is way off due to the complete lack of accounting for the differences in efficiency and weight of other power train components. The previously linked NASA paper cites 3-4x efficiency and 6x motor power to weight compared to state-of-the-art engines. I suggest at least reading that paper to clear major counter intuitive misconceptions before attempting an analysis.https://ntrs.nasa.gov/citations/20140011913

author: mzzj
author_rank: Super Contributor
timestamp: November 02, 2020, 04:14:54 pm
content: Quote from: sandalcandal on November 02, 2020, 12:22:58 pmNASA paper is written from small 4-person recreational aircraft point of view and we were lately talking about medium sized 737 commercial passenger jets on "short" 1000km distances. Small aircraft with piston engines and stoneage design just purely suck.Cirrus SR-22 is apples to oranges..potatoes comparison in this regard.10x cheaper fuel source? Sure if you compare to 100 octane low lead avgas. Jet fuel is 6 times cheaper than 100LL. And engines are roughly twice as efficient.6x Engine power to weight ratio ?Emrax 268 brushless AC motor has amazing (for electric motor) 11.56 kW/kg power to weight ratio and I'm not sure how well this would scale to larger units.https://www.nextbigfuture.com/2015/04/siemens-and-emrax-claim-best-power-to.htmlJet engines are bit tricky to calculate but Pratt & Whitney PW150 turboprop: 4.76 kW/kg

author: sandalcandal
author_rank: Unknown
timestamp: November 02, 2020, 05:37:20 pm
content: Quote from: mzzj on November 02, 2020, 04:14:54 pmFair enough, the paper was primarily about smaller aircraft rather than commercial passenger jets like the 737. The model used to get 400 Wh/kg is 200 mile (321 km) range. The paper did quote "SOA" engines so I'm don't think "Small aircraft with piston engines and stoneage design" is fair so say but I can see large jet engines achieving much better efficiencies.Since you've bothered to read sources and add info and calculations I'll try calculations of my own for 1000km rangeCessena Grand Caravan EX 14 seater turboprophttps://cessna.txtav.com/en/turboprop/grand-caravan-exRange 1689km, Cruising speed 343km/h, Usable fuel weight 1019kg, full fuel payload 583kg, Engine power 647k W,dry engine weight 175kgFull range fuel energy = 1019*12 = 12 000kWhElectric full range energy = 12 200/4 = 3000kWh (Also full range flight time = 1689/343=4.9h, full range energy = 4.9*647=3170kWh)Electric Range-Energy Efficiency = 1689/3000 = 0.563km/kWhEnergy for 1000km = 1000/0.563=1800 kWhMinimum engine weight = 647/11.56= 56kgEngine weight saving = 175-56 =119kgAvailable weight = 1019+119=1138kgMinimum specific energy for 1000km range = 1800/1138 =1600Wh/kgMaximum energy with 400Wh/kg = 1138*0.4=455kWhMaximum range with 400Wh/kg = 256kmEdit2: Didn't add reserve margins for electric but should roughly scale through with built in fuel margins.It would seem the 400kWh/kg minimum target really is a minimum for viable electric aircraft. I'm not sure how the 750Wh/kg then comes about. However, these calculations as based off an existing turboprop airframe and as also discussed in the NASA paper, electric enable fundamentally different design paradigms which could greatly reduce required power overall not just engine inefficiency."NASA’s aeronautical innovators hope to validate the idea that distributing electric power across a number of motors integrated with an aircraft in this way will result in afive-time reduction in the energy requiredfor a private plane to cruise at 175 mph [281km/h]."https://www.nasa.gov/image-feature/nasas-x-57-electric-research-planeEven halving energy would be immense let alone 5 times reduction.Edit: Even in very recent news NASA is still sticking to that "goal of a 500 percent increase in high-speed cruise efficiency" 2 Nov 2020https://www.nasa.gov/aeroresearch/all-electric-x-57-propeller-designs-undergo-wind-tunnel-tests

author: Rx7man
author_rank: Regular Contributor
timestamp: November 02, 2020, 06:40:25 pm
content: Another "gotcha" in battery systems is that often there are tradeoffs between recharge cycles, capacity, and current draw, as well as diminishing efficiency when you demand more current from them.. If they are getting charged and discharged a couple times a day (which would be needed in order to be viable options), their lifespan might be quite short.I can't speak as to how each of those details are going to play with each other, but it would certainly be something engineers think about

author: Siwastaja
author_rank: Super Contributor
timestamp: November 03, 2020, 09:15:49 am
content: Quote from: sandalcandal on November 02, 2020, 12:22:58 pmThey won't be flat, but adding the marginon bottomdoesn't help with battery cycle life that much; most of the cycling damage is done charging near top, especially at high charge rates. Tohavethat safety margin, the cells would have to be charged near 100%; and given the hectic schedules, at significant charge rate. Basically it would need to be some 35% - 95% cycles in one hour which works out some 0.6C average. You are not really stress-quick-charging, but not doing easy cycles either, quite close to "standard" conditions actually which result in some 500-1000 cycles.So while 500 cycles might not be the exact limit, 1000 might be achievable with the current tech, mzzj is mostly correct in this point. You can't derate the cells much to increase the cycle life. You can't slow down charging already at 80% like Tesla does.But I do question the assumption of the nearly-50% jet engine efficiency used by mzzj. I suspect this number is at highly optimum conditions. Designed to provide good overall efficiency for long flights, jet engines are likely a lot more inefficient during taxiing, takeoff, climb, and again, when running (near-)idle during descent. Electric shines in providing good efficiency at large dynamic range, important at short trips.In order to make reliable calculations, I think we shouldn't try to back-calculate flight energy usage from the fuel consumption times assumed efficiency, but instead go more directly at the source and use actual mechanical energy requirements, mostly regarding aerodynamics. But sadly I can't contribute with actual numbers here. I know it's so easy just to take the well-known fuel consumption numbers for existing passenger jets then work from there, but there are quite some many hidden assumptions.In any case, I don't think we can twist the reality to make this viable with thecurrentbattery technology, not even close, but OTOH, it's hard to predict what happens with battery technology.

author: sandalcandal
author_rank: Unknown
timestamp: November 03, 2020, 09:34:14 am
content: Far more so than with cars, swappable batteries would make a lot of sense and be much more practical for commercial flight operations. A need for high up time, the ability to reduce recharging stress on cells, having depot facilities and trained technicians available, the cost vs. benefits would likely weigh out far better for electric aviation than it did for electric cars. I think it's highly likely we'll see serious implementation of battery swapping for "practical" commercial electric aviation as it comes out.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 03, 2020, 09:52:57 am
content: I don't believe in viability of swappable batteries, that's always a complex mechanical disaster which adds weight and cost. Even Tesla failed at it (deliberately, of course; it was just a publicity stunt for dumb people who think swappable batteries are a good idea and Tesla "should" do it.)There is no reason, because there is no need for 15-minute quick charge cycles. There is plenty of time for normal charge. Currently, fueling, loading cargo and passengers, and doing all necessary checks, shutting down andstartingjet engines take somewhere around an hour, or more. Note that charging power is easy to supply from multitude of points at the airport. It's like the "ground power" currently is, just a thicker cable and heavier connectors.

author: Rx7man
author_rank: Regular Contributor
timestamp: November 03, 2020, 05:53:07 pm
content: Quote from: Siwastaja on November 03, 2020, 09:52:57 amI'll bring your attention to this post if you missed it.. That charging power is NOT easy to supplyQuote from: NANDBlog on November 01, 2020, 10:35:56 pm

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 03, 2020, 06:43:59 pm
content: If you go on Flightaware or similar site and realize how many planes are in the air at any given time it's mind boggling. Even if we switch all passenger cars to electric, that is a drop in the bucket compared to planes. So we do need to figure out a way to move towards electric, or at least clean fuel planes. Ships are another big one too. A single container ship puts out more pollution in one day than a million cars in a year. (or something like that, I forget the stat) Current battery tech is not good enough, perhaps we need to look at hydrogen, but I don't know if that is high density enough either. But something needs to be figured out if we want to stop climate change. It is already getting bad enough where it is affecting quality of life and it's only going to get worse, we've hit a point where the effects are exponential now. Our ski and skidoo season here is much shorter now days. Up north where they rely on ice roads, they have issues keeping those frozen as well. This affects shipments. In the tundra regions, it is starting to melt, and causing issues with structures. Lots of other effects can be felt around the world. Climate change is real and something needs to be done.China and India are the two biggest polluters though, so even if we DO manage to switch to EVs - planes, ships, cars and all, it's STILL going to be a drop in the bucket if China and India continue to pollute at their current rates.Also let's just assume here that if we do switch to electric planes, it means high scale energy storage has been figured out, so it would be safe to say the entire power grid would be all renewable too. The idea of switching everything to electric still relies on the power grid using green energy. Producing green energy is the easy part, we've been doing it for 100's of years. It's storing it that is harder.At the end of the day, I think we are royally screwed honestly.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2020, 06:59:16 pm
content: Electric airliners are a non-starter, it's just never going to be practical without some kind of massive leap in battery technology. State of the art batteries are nowhere close to the energy density of hydrocarbon fuels and aircraft already struggle to carry enough of that fuel for long trips, fuel makes up a substantial fraction of the overall weight of the aircraft. I'm sure it has been mentioned already but a major advantage of liquid fuel is that the aircraft gets steadily lighter as fuel is consumed, something that does not happen with electric power. Passenger cars, trucks, buses, boats, ships, these are all reasonable candidates for electric power, large passenger aircraft are not. Various alternative fuels for aircraft could be practical, unlike passenger cars, planes flying between major airports don't need to be able to refuel at thousands of different locations dotted across the landscape so there is not the big infrastructure needed for personal cars. I don't think we'll be seeing anything meaningfully displacing kerosene as the fuel of choice to power large passenger planes any time soon though.Regarding the efficiency of jet engines, they are most efficient near full rated power, and at high altitude, conditions that rarely exist at the same time for passenger aircraft. Turboprops are substantially more efficient, around 25% over turbofan engines, the disadvantage being they are slower. Even the old radial piston engines from the WWII era compare favorably to modern jets in terms of fuel efficiency however they are nowhere close in mechanical reliability or TBO. They sure do win in style and cool factor though IMHO, I'll take a seat on something like a Constellation or DC-6 over a 737 any day.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2020, 07:13:33 pm
content: Quote from: Rx7man on October 28, 2020, 07:31:51 amIt sounds like you're engaged in a religious argument, in which case it is futile. He earnestly *believes* that he is correct and that it will happen, so no amount of facts, data or logic will convince him otherwise. One need not look further than the various threads on solar roadways, EVs, over-unity and other things or anywhere that allows political discussions to observe this phenomenon. You cannot win an argument with logic if your opponent's view is not built upon logic in the first place. You are arguing against their belief and you will never win, even when anyone who looks at it objectively will have to conclude that you are correct.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2020, 07:47:03 pm
content: Quote from: dunkemhigh on November 01, 2020, 07:06:49 amThat is certainly true for me. The ability to make voice calls is a secondary feature of my phone. Most of the time I use it for text messages, as a still camera, as a camcorder, as a GPS navigator, as a portable music player, to check the weather, to check my email, to view my home security cameras, etc. It's not as good at any one of these tasks as a dedicated device but it's good enough and I always have it with me. Back in the pre-smartphone days I missed a lot of good photos for example because I didn't bring a camera with me. I got lost a few times and wished I had my GPS that I'd left at home. A smartphone is the Swiss army knife of technology, if I'm only going to carry one device with me that's the one I'm going to take. I still have more specialized dedicated devices that I can use when I know what I'm setting out to do.

author: Rx7man
author_rank: Regular Contributor
timestamp: November 04, 2020, 01:15:16 am
content: Yup, i think concentrating on electric ships would be a far better testbed for major electric transport, container ships in particular.. they can just take however many containers worth of batteries, all the infrastructure to load and unload is already there, you'd only need to change the drive systems and have a controller.. Sure, weight is an issue on ships too, but it's not a dealbreaker like on an aircraftNorth america could certainly electrify a lot of the rail grid.. I mean Russia only did it something like 50 years ago

author: mzzj
author_rank: Super Contributor
timestamp: November 04, 2020, 06:38:43 am
content: Quote from: Rx7man on November 04, 2020, 01:15:16 amLets start with big ships as they are most efficient: Maersk Triple-E classhttps://en.wikipedia.org/wiki/Triple_E-class_container_ship35km/h, Shanghai-Los Angeles 12 000km =342h ( there is also lot longer shipping routes like china-europe past Cape Town but you have more potential locations to recharge)2x 29 680kW engines = 10150560 kWh spent on Shanghai- Los Angeles.10150 MWh Li-ion battery weights around 50 000 metric tons, about 25% of total DWT so kind of acceptable.BUT: It would be 50% of Tesla Gigafactory 1 yearly production.. not to mention cost.OK, big ships are obviously not the best use for batteries...Maybe short distance car ferries and cargo ships then.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 04, 2020, 12:54:09 pm
content: The first ships were wind powered. Why not make modern ships that are primarily wind powered with something like biofuel as a backup?

author: sandalcandal
author_rank: Unknown
timestamp: November 04, 2020, 01:01:32 pm
content: Quote from: NiHaoMike on November 04, 2020, 12:54:09 pmJust a concept it seems but something that is being considered.https://www.oceanbirdwallenius.com/

author: tszaboo
author_rank: Super Contributor
timestamp: November 04, 2020, 03:34:16 pm
content: Quote from: NiHaoMike on November 04, 2020, 12:54:09 pmTheir payload was also tiny, took them months to cross an ocean, and required a large number of sailors to maintain the ship. There are some experiments with the Magnus effect (witchcraft if you ask me) sailing ships. It might reduce the usage of a ship.For cargo, WIG effect looks very interesting. It is a hybrid between hovercraft and aircraft, with small wings. If they can operate from shipyards, go a lot faster than ships, take more cargo than aircraft, and you dont need to build channels, because it works above solid ground just as well as water. Maybe if would be possible to operate these from batteries. But it is hard to say, as most of these WIG aircrafts were experimental. I dont think it would replace conventional ships, more like a cheaper alternative to cargo planes.

author: james_s
author_rank: Super Contributor
timestamp: November 04, 2020, 06:13:53 pm
content: Well for big ships there is also the nuclear option, as far as I know it has only been done once for a civilian ship and was reasonably successful. A large number of military vessels are nuclear powered.

author: Rx7man
author_rank: Regular Contributor
timestamp: November 04, 2020, 10:03:25 pm
content: Quote from: NiHaoMike on November 04, 2020, 12:54:09 pmWell, for one, it takes a BIG crew to run those ships, in those times, there was no such things as OSHA, super dangerous job..Here's an incredible video of a big sail ship going around Cape hornhttps://youtu.be/9tuTKhqWZso

author: james_s
author_rank: Super Contributor
timestamp: November 05, 2020, 01:18:47 am
content: I don't think anyone is suggesting using replicas of 17th century sailing ships to carry cargo in modern times. I'm not sure how practical it would be, but I have little doubt that modern technology and materials could enable a large scale sailing ship that could be safely operated by a crew comparable to that on an oil powered ship. It's not unheard of for people to sail around in oceans solo on 30-60 foot sailboats, and hundreds of years ago any practical ocean going vessel would have required a substantial crew. Modern rigging and the availability of power assist for things like steering and winches, and electronic navigation equipment greatly reduce the need for large crews to handle the manual labor.

author: Rx7man
author_rank: Regular Contributor
timestamp: November 05, 2020, 03:57:04 am
content: yes, but a big ship way back when (like the one I posted a link to in my last comment) was 8000 tons loaded, and was the biggest ship of its time (if you haven't, watch the vid, it's a treat!)The Maersk ships are 55,000 tonnes EMPTY, fuel, cargo, crew, etc can add 210,000 more tonnes, so we're up to 265,000 tonnes fully loaded... there's a reason they're that size, because it's economical!

author: PlainName
author_rank: Super Contributor
timestamp: November 05, 2020, 04:39:33 am
content: I doubt it this one needs as many sailors to work - AIUI the sails are automatic.

author: james_s
author_rank: Super Contributor
timestamp: November 05, 2020, 06:04:53 am
content: The bigger the ship, the bigger the sails, the more force the wind exerts on them. The much greater weight is not really an issue, it's correspondingly larger. A 747 flies by the same physics as a Cessna. Again it may not be practical or cost effective, it's going to be much slower than a conventional ship but I see no technological reason why it couldn't be done.

author: Rx7man
author_rank: Regular Contributor
timestamp: November 05, 2020, 10:14:47 am
content: that's the whole point, it has to be viableNo doubt we could build a plane 4x bigger than an A380 and make it fly, but few airports could take it and thus isn't viable.I don't think the investment, crew requirements and capital costs of adding sails to a ship is going to be economical.. Would be more reasonable to have nuclear power, but that's not without problems either of course

author: Clear as mud
author_rank: Regular Contributor
timestamp: November 05, 2020, 01:43:57 pm
content: That first link someone posted to a modern cargo ship with sails, the Wallenius Oceanbird, says the ship takes 12 days to cross the Atlantic Ocean. That seems to be comparable to a conventional cargo ship.

author: Rx7man
author_rank: Regular Contributor
timestamp: November 06, 2020, 08:08:51 am
content: Is that the typical crossing time or the a pie in the sky figure if conditions are just great? Also, it looks very difficult to load seeing it doesn't look like it takes containers, which is going to be a serious issue

author: JohnG
author_rank: Frequent Contributor
timestamp: November 07, 2020, 10:30:39 pm
content: Unless I missed something in this thread, I don't see a lot of discussion on hybrid-electric turbofans.I know that there has been a great deal of work on this from the engine side. The benefits are analogous to those for hybrid electric cars, except amplified because turbofans have a much smaller window of high efficiency in a relative sense compared to ICEs, and because you have a lot longer to recoup your investment versus automobiles. I have been out of the loop on this for the past few years, so I'm not sure what's happening these days.John

author: Rx7man
author_rank: Regular Contributor
timestamp: January 06, 2021, 09:04:39 am
content: Thunderfoot just made a video on Elon Musks supersonic jet ideahttps://youtu.be/dMmaG_3NnGs

author: james_s
author_rank: Super Contributor
timestamp: January 10, 2021, 12:45:44 am
content: Quote from: JohnG on November 07, 2020, 10:30:39 pmSounds like an interesting concept, although I'd be curious to see how the efficiency actually pans out. Perhaps having inboard turbine engines driving integrated alternators with residual thrust used to propel the plane and the electricity output used to power electric ducted fans. In theory the turbines could be run at full power where they are most efficient, and a battery bank could provide the extra power needed for takeoff and climbout.I'd like to see more turboprops and unducted fans, turboprops are slower than jets but substantially more efficient, I think they look a lot cooler too but that isn't something most people care about. Propellers may be old fashioned but so are wheels and we still use those.

author: agtrbt
author_rank: Contributor
timestamp: February 10, 2021, 03:35:05 am
content: may be design a new hydrogen Hindenburg with mechanism and route that can well survive the fire. e.g. jettison the bladder with parachute and deploy comfortable ocean float bags etc