Naked Science Forum
Life Sciences => The Environment => Topic started by: Lewis Thomson on 11/01/2022 10:00:23
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Eddy has sent The Naked Scientists a question all the way from the other side of the world.
"Here in Australia there is a great debate about the pros and cons of hydrogen as a fuel source (fuel cells etc) versus electricity as a fuel source (batteries etc). I'd love to hear a detailed explanation and critique of hydrogen as a fuel source.."
What do you think? Let's discuss the impact of hydrogen as a fuel source in the comments below.
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Hydrogen has 3 times the energy density of diesel fuel (roughly 150: 50 MJ/kg) and is the ideal liquid fuel in theory. It is rapidly becoming a practicable fuel in small quantities (for road vehicles and aircraft) thanks to the development of large scale applications in rocketry.
The best lithium batteries can only manage 1 MJ/kg.
Thanks to Carnot, you can only turn about half the energy of a combustible fuel into useful work, so the ratio of available energy per unit mass in, say, a car, is closer to 75:25:1, but you have to generate the electricity to charge your lithium battery and most of that still comes from a combustible fuel.
The best solution seems to be a hydrogen fuel cell driving electric motors, with an intermediate battery providing rapid acceleration and regenerative braking.
The engineering problem with aircraft is that hydrogen storage in the wings is inefficient as a wing has a large surface/volume ratio (= significant heat input) so you have to rethink the configuration with the fuel tanks in the fuselage and flat fuel cells in the wings (for dispersal of waste heat) feeding multiple electric motor/propellors. A hydrogen-fuelled jet engine may well be feasible but doesn't seem to have hit the headlines just yet.
Domestic and industrial fuel was "town gas" (50% hydrogen) for about 100 years, so no problem using it for static power, which accounts for more than half of our energy consumption.
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It's pretty good but exessivley volumous. Liquid fuels of some sort are the easiest to handle. At present methane butane etc has always been a great fuel because of its cleanliness and ease of mixing but storage has always been a problem.
The engineering problem with aircraft is that hydrogen storage in the wings is inefficient as a wing has a large surface/volume ratio (= significant heat input) so you have to rethink the configuration with the fuel tanks in the fuselage and flat fuel cells in the wings (for dispersal of waste heat) feeding multiple electric motor/propellors. A hydrogen-fuelled jet engine may well be feasible but doesn't seem to have hit the headlines just yet.
Nothing about heavy duty cylinders or cryogenic refrigeration and deadweight batteries is particularly aerospace. Petrol on the other hand sounds fantastic, your plane just burns that weight away as it progresses.
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it's energetically and financially expensive to make, financially expensive to store, it burns reasonably efficiently, so it's got that going for it, which is nice. Or you can put it through expensive hydrogen fuel cells, which are very efficient, but expensive. Did I mention that it's expensive?
Oh yeah, and it can explode, it's got the widest explosive and flammable range of any fuel.
What's not to love.
Oh yeah, then there's blue hydrogen. You take methane, chemically hack off the carbon and turn it into carbon dioxide, a greenhouse gas, and then sell the hydrogen and release the carbon dioxide into the atmosphere. The fossil fuel industry want you to use this. It's like methane, which at the moment has quadrupled in price, but even more expensive.
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It's pretty good but exessivley volumous.
Thanks to its high energy density, the fuel tank volume for hydrogen is only about twice that for diesel or JETA1., and the weight is about a third. So we'll need to change the shape of aircraft a bit but they will be lighter at takeoff and therefore have a bigger payload.
Nothing about heavy duty cylinders or cryogenic refrigeration and deadweight batteries is particularly aerospace.
Apparently NASA and ROSCOSMOS don't know that. Amateurs.
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it's energetically and financially expensive to make,
Like electric cars, hydrogen vehicles will be powered by free wind-generated electricity. The difference is that
(a) the power/weight ratio of a hydrogen vehicle is vastly superior to a battery-driven one
(b) the on-board energy store is a lot simpler and cheaper
(c) refuelling rate is of the order of 150 MW compared with 40 MW for diesel and 0.5 MW for battery-electric, so total journey times will be shorter
(d) the interim demand can be met by modifying existing internal combustion engines without scrapping them
My only reservation is the longevity of fuel cells. There are plenty in current road vehicle use so we will have good data soon. Reliability certainly hasn't been a problem in space vehicles, but they aren't particularly cost-sensitive. That said, the entire Apollo moon program cost less than one third of the new London-Birmingham railway track, so cost is obviously not a major problem.
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Hydrogen has 3 times the energy density of diesel fuel (roughly 150: 50 MJ/kg) and is the ideal liquid fuel in theory.
Hydrogen has 3 times the energy per mass as diesel fuel, but if you're actually talking about density, even compressed to 10,000PSI, hydrogen has about 1 quarter the energy per volume. So, to get comparable range to what cars and light trucks now get with gasoline or diesel, you'd need a 200 liter tank. And that tank will have to be cylindrical with semispherical ends, or spherical over all. Think 55 gallon oil drum sized. No fitting this in a flat space under the trunk or seats.
It's also basically a bomb if the vehicle is involved in a serious accident. That 200 liters of hydrogen really wants to occupy 140,000 liters of space. Lose structural integrity of the tank, and it will first blow apart through explosive decompression of the fuel, and then, more than likely, explode into a fireball.
I'm not saying those challenges can't be solved, but saying hydrogen is better than batteries for vehicles because "energy density" is both misleading, and leaving out some real challenges.
"Here in Australia there is a great debate about the pros and cons of hydrogen as a fuel source (fuel cells etc) versus electricity as a fuel source (batteries etc). I'd love to hear a detailed explanation and critique of hydrogen as a fuel source.."
You don't want to think of hydrogen as an energy source. There simply isn't any source of hydrogen in it's reduced form accessible to us. Hydrogen is an energy transmission and storage medium. It fits between the source of energy, and it's end-use.
There are basically two energy sources that can be used to generate hydrogen that matter to the discussion. You can create hydrogen by breaking down methane, using more methane as the heat source. But that does nothing to decarbonize our energy system, and just creates a harder to manage fuel (hydrogen) out of an easier to manage one (methane). It's a dead end.
Or, you can generate hydrogen through electrolysis, with the electrical energy coming from renewable sources like wind or solar, or from other carbon-free sources like nuclear. This is what most advocates of a hydrogen economy are imagining - basically, you still build all the renewable or carbon neutral electric generation capability we're talking about for the renewable future, but instead of moving the energy around in electric fields (wires) and storing it in batteries or other reverse generation technologies, you move it around in the form of compressed hydrogen gas, and store it as compressed hydrogen gas or liquid hydrogen. Big parts of the fossil fuel infrastructure industry will advocate for this approach. It keeps them busy building and operating wells (hydrogen plants), pipelines, and tanks. It keeps transportation tied to roadside refueling (gas stations, literally this time around). It feels like v.next of things they understand. But it has little advantage to the electric infrastructure industry. They may get to sell lots of electricity at commodity wholesale rates to the gas/liquid fuel industry, but it doesn't electrify the economy.
It doesn't benefit consumers particularly either. Hydrogen won't be cheaper than electricity, since for all practical purposes, it is electricity transformed into chemical energy, before being transformed into heat or kinetic energy. It won't re-use much of the infrastructure they own, since hydrogen cannot be efficiently utilized by their natural gas plumbing. They will lose the advantage of being decoupled from roadside refueling for most of their transportation energy needs (electric personal cars and trucks will be fueled largely in their own garages, after all). They get to keep rapid, roadside refueling, but more than a few will notice that the cost of that is that they are riding with a bomb the size of a 55 gallon oil drum in their trunk.
Nations need to answer the hydrogen economy question from a systems point of view - is the storage and delivery technology you get with hydrogen enough better than what you can get with batteries, at all scales, to justify the additional complexity? It could be. One can imagine Australia generating hydrogen in the 350 days of sun a year outback, and piping it to the populated areas, upgrading their infrastructure, and making all that work. Personally, I doubt it. I think there are better utility-scale energy storage options that hydrogen, electricity is a better distribution method, and batteries are good enough - and easier to get to - for transportation.
(There is a third way: you could crack methane with heat from nuclear reactors, to make hydrogen. But you'd still be freeing fossil carbon, although not necessarily into the atmosphere - it could be a solid phase carbon with enough chemical engineering magic. But you'd have to overcome your country's nuclear jitters.)
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(a) the power/weight ratio of a hydrogen vehicle is vastly superior to a battery-driven one
Have you considered the weight and cost of the container?
also, structural battery is being developed, which will increase overall power/weight ratio of a battery vehicle.
(b) the on-board energy store is a lot simpler and cheaper
If you consider the necessary preventive countermeasures to the hazards, it would be a lot complicated and expensive.
refuelling rate is of the order of 150 MW compared with 40 MW for diesel and 0.5 MW for battery-electric, so total journey times will be shorter
It's possible to increase charging rate of battery electric vehicle. The technology hasn't met its theoretical limit yet.
In principle, the BEV can be charged wirelessly. So, it's possible to install wireless charger along a highway or toll road, which makes the battery increase its stored energy during the journey. That's impossible with hydrogen.
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Hydrogen has 3 times the energy per mass as diesel fuel, but if you're actually talking about density, even compressed to 10,000PSI, hydrogen has about 1 quarter the energy per volume.
Liquid hydrogen has about one tenth of the density of diesel, so you need about 3.5 times the fuel tank capacity for a given range. This requires some variation of vehicle design but is by no means as restrictive as a battery. On the other hand if folk are happy with the 200 mile range of a practical electric car, there's no significant redesign at all.
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Have you considered the weight and cost of the container?
Every liquid-fuelled rocket designer has.
https://www.riversimple.com/service/#therasa shows a hydrogen gas powered city car with 300 mile range and 5 minute refuelling.
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It's possible to increase charging rate of battery electric vehicle.
Let's increase the charging rate to 40 MW and assume that 1000 people in the UK want to recharge their cars at the same time. You need an entire new national grid and its generating capacity to meet the demand. Assuming, of course, that you have a radical new battery and radiator design that can dissipate 500 kW of heat, or not generate it in the first place, whilst charging.
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So, it's possible to install wireless charger along a highway or toll road,
Aha! The electric railway! Brilliant idea. No need for personal ownership or driving test: just rent a seat for the trip you want to take.
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Liquid hydrogen has about one tenth of the density of diesel, so you need about 3.5 times the fuel tank capacity for a given range.
Honestly, it never occurred to me that someone might imagine using liquid hydrogen for automobile fuel. It's completely impractical. Every liquid hydrogen storage facility must be continuously maintained at cryogenic (20oK or thereabouts) temperatures. That takes expensive equipment, and that equipment has to keep running all the time. If it fails, you have to vent the hydrogen safely into the open atmosphere as it boils off, to avoid turning your garage into a bomb. So every car or pickup truck fueled by liquid hydrogen: 1) would continuously use fuel in order to maintain it's cryogenic state; 2) would have to be parked in a location with facilities for venting hydrogen in the case of a failure. Not practical at national scale.
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So, it's possible to install wireless charger along a highway or toll road,
Aha! The electric railway! Brilliant idea. No need for personal ownership or driving test: just rent a seat for the trip you want to take.
You seem to miss the wireless part. Also where your car can go in with low batt and go out fully charged.
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This requires some variation of vehicle design but is by no means as restrictive as a battery.
Are you referring to hydrogen intrrnal combustion engine, or hydrogen fuel cell?
How many hydrogen cars were delivered last year? How is it compared to battery cars?
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You need an entire new national grid and its generating capacity to meet the demand.
Not necessarily if the charging stations are equipped with their own batteries or super capacitors.
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Is hydrogen a better fuel source for the environment?
Only if we find a hydrogen mine.
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You need an entire new national grid and its generating capacity to meet the demand.
Not necessarily if the charging stations are equipped with their own batteries or super capacitors.
And they are charged by what magic? A typical filling station on an A road may have 10 or more pumps, each delivering 40 MW at roughly 20% duty cycle (a minute to deliver 50 liters, 3 minutes to pay, 1 minute to bring up the next car) so you need 80 MW average and 400 MW peak input to meet normal demand.
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You seem to miss the wireless part.
For a very good reason.You want to bury charging inductors all along every major road. Suppose each vehicle is consuming 30 kW and the inductors are one vehicle length apart. Then every inductor must be capable of supplying 30 kW to the receiver which is at least 15 cm away. Possibly just feasible. But not if the car is made of steel, which will look like a short-circuit. My cooker has 2 kW induction plates that heat a steel pan to cooking temperature in about 10 seconds. Not a pleasant experience for the passengers.
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Is hydrogen a better fuel source for the environment?
Only if we find a hydrogen mine.
Gas companies owned several "hydrogen mines" in the past, but electrolysis of sea water is the only feasible source since Mrs Thatcher closed them. It's good enough for all the buses, council vehicles and airport ground power in Kirkwall.
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Have you considered the weight and cost of the container?
Every liquid-fuelled rocket designer has.
Actually, the low density of liquid hydrogen fuel is a huge problem even for rocketry. It's only practical if it's used with dense liquid oxygen which raises the average propellant density. But some designs such as beamed power rockets would ideally use only hydrogen fuel (due to its low molecular mass, which gives a high exhaust velocity). But in practice that works badly because the tankage is so heavy relative to the contents.
In a car, the tankage weight is not such an issue, because the rest of the car is so heavy, but it's completely impractical; everything would have to be thermos flasked. Also production of liquid hydrogen is incredibly energy intensive far more so than simply electrolysis of hydrogen. The heat capacity of hydrogen is MASSIVE (multiple times that of H20 which is huge to start with), so the liquefaction gets ridiculous, and there's other complications relating to spin isomers as well.
In rocketry the downsides of liquid hydrogen make it a slight loss during take off compared to hydrocarbon fuels, but the higher exhaust velocity and lower overall stage weight pays off at higher speeds, so it's seen more use for upper stages. Ideally for a launch vehicle you would use a tripropellant design. That's how the space shuttle worked pretty much, it took off mostly on dense fuel solid rocket boosters, and then transitioned to liqhtweight liquid hydrogen fuel as the speed grew.
But even in rocketry, hydrogen is far from an ideal fuel, and it's even worse in vehicles like cars, and it would be an expensive fuel for aircraft.
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And they are charged by what magic? A typical filling station on an A road may have 10 or more pumps, each delivering 40 MW at roughly 20% duty cycle (a minute to deliver 50 liters, 3 minutes to pay, 1 minute to bring up the next car) so you need 80 MW average and 400 MW peak input to meet normal demand.
Sufficiently advanced technology is indistinguishable from magic. We can build solar panels or wind turbines with various design, which we will need anyway even if we go with green hydrogen.
The batteries at the charging stations are only used to reduce charging duration.
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Gas companies owned several "hydrogen mines"
Yes, but what we need are real hydrogen mines without the "quote marks".
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The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.
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We can build solar panels or wind turbines
UK average solar input is 100 W/sq m so to recharge one electric car at a time at anything like a sensible rate, you need at least 1000 square meters of garage roof space, plus sufficient battery storage to cope with the cars that arrive at night (up to 20 hours in the north of Scotland) or when the wind isn't blowing.
The real fun begins when there is a queue of battery cars at a single "pump". If each takes 40 minutes to refuel, it's probably quicker to walk. Fights will break out. The electric car is the beginning of the end of civilisation.
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The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.
Sea water is not hydrogen; it doesn't burn with a characteristic squeaky pop.
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The real fun begins when there is a queue of battery cars at a single "pump". If each takes 40 minutes to refuel, it's probably quicker to walk. Fights will break out. The electric car is the beginning of the end of civilisation.
Or you can do it in your own garage over night. With 300 miles range, daily urban commute can last for a week. That's what the hydrogen car company claims in its website. But you are unlikely to refuel hydrogen car in your own garage.
Public charging stations are mostly needed for long journey only.
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The real fun begins when there is a queue of battery cars at a single "pump". If each takes 40 minutes to refuel, it's probably quicker to walk. Fights will break out. The electric car is the beginning of the end of civilisation.
I find it interesting how little imagination folks have of how profoundly electric cars change the whole notion of refueling. Personal vehicles are almost universally garaged or parked for 12 or more hours every day at the owner's residence. Fleet vehicles used for trades, construction, farming, delivery and the like likewise at the owner's business. They will be charged there, and leave "home" nearly every day fully charged. They are only rarely driven more than 250 miles in a day. Most will go months on end without needing to be recharged at a "station."
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The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.
Sea water is not hydrogen; it doesn't burn with a characteristic squeaky pop.
Neither is ferric oxide the same as iron. AFAIK the only substances that are mined as elements rather than compounds, are helium, carbon, and gold. It is a sin to burn carbon and the others don't oxidise readily. Every other element (including hydrogen) is extracted from its stable natural compounds when we need it.
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Personal vehicles are almost universally garaged or parked for 12 or more hours every day at the owner's residence.
Apart from most of them, which are parked on the public road. You must have an idyllic suburban life in Walnut Close!
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The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.
Sea water is not hydrogen; it doesn't burn with a characteristic squeaky pop.
Neither is ferric oxide the same as iron. AFAIK the only substances that are mined as elements rather than compounds, are helium, carbon, and gold. It is a sin to burn carbon and the others don't oxidise readily. Every other element (including hydrogen) is extracted from its stable natural compounds when we need it.
If diesel oil was an element, you would have a point.
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You still have to refine, extract and blend it from the gunge that comes out of an oil well.
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You still have to refine, extract and blend it from the gunge that comes out of an oil well.
Fundamentally; oil burns but water doesn't.
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Apart from most of them, which are parked on the public road. You must have an idyllic suburban life in Walnut Close!
I do have an idyllic life, but not in the suburbs. Walnut Close is a farm.
But your "most" argument is wrong. Two thirds of American households have covered, on site parking for their autos. Another fraction beyond that 2/3 are able to park on their own property. All of these households can, with modest upgrades to their infrastructure, overnite charge an electric vehicle.
But in truth, these sort of arguments - energy density of hydrogen, at home charging - are not where the real discussion is needed. Both electric and hydrogen are viable means of energy transmission and short term and mobile storage, and thus are viable fuels for transportation and heating (the only other area where people directly consume energy that is not already effectively electrified). They present different engineering challenges, and different trade-offs to the consumer, but either can be made to work.
The real question is a system question - which is the better option (from a cost, efficiency, complexity and risk point of view) overall for source-to-consumption energy transmission and storage? My sense is that hydrogen (compressed gaseous hydrogen that is) has only a relatively small role to play from that point of view. Liquid hydrogen is too expensive (energy-wise) and complex to be useful for anything other than very specialized applications.
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A possible way Hydrogen can replace Lithium in a battery is as moving ion inside the battery. H+ has almost 7 times charge per mass ratio compared to Li+. But here we can't call Hydrogen as the fuel source, as we don't say Lithium as fuel source in Lithium ion battery.
(https://www.researchgate.net/profile/Saeed-Sepasi/publication/280886489/figure/fig2/AS:669007095033870@1536515129588/Chemical-reaction-of-a-LiFePO4-cell-21.ppm)
We still need to choose/invent suitable materials for anode, cathode, electrolyte, and the separator, which comprise most weight of a battery cell, apart from the container.
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Two thirds of American households have covered, on site parking for their autos.
Aha! A serious cultural difference. Probably 80% of UK private cars sleep at the roadside. We have a higher outer-city population density (rows of terraced houses lining the sidewalk and maisonette apartments above shops) and level of car ownership among city-dwellers, than you would find in the USA. Highest-density apartment blocks were generally not built with on-site parking for the present number of cars.
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My sense is that hydrogen (compressed gaseous hydrogen that is) has only a relatively small role to play from that point of view.
Again a cultural (and possibly generational) difference. The UK has an extensive gas grid, currently delivering methane (most of which is used for generating electricity!) to almost every home and factory. 60 years ago it carried "town gas", which was 50% hydrogen. The changeover was prompted by concerns of toxicity (most of the rest was carbon monoxide) and the availability of cheap methane from the North Sea, and was pretty well complete in 5 years. No problem in principle to convert to pure hydrogen.
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No problem in principle to convert to pure hydrogen.
Other than if you're transporting like for like quantities of energy, you'll need to upgrade most of your lines to either bigger diameter or higher pressure pipes. Hydrogen has roughly 1/4 the energy density of methane per unit volume at any given pressure. (Not saying that as an objection - it's "just" a big civil engineering project).
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But given the original mixture was 50% hydrogen the additional pressure requirement will be small. In any case the main feed pressure is a lot higher than the regulated delivered flow to domestic gas taps - about 20 millibar. This happily delivers 50 kW to a commercial cooker through a 20 mm hose, so no problem recharging a car at a few megawatts from an adequately manageable 40 mm hose and a 500 mB pump - as they already do in several places in the UK.
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https://en.m.wikipedia.org/wiki/Hydrogen_vehicle
Most companies that had been testing hydrogen cars have switched to battery electric cars; Volkswagen has expressed that the technology has no future in the automotive space, mainly because a fuel cell electric vehicle consumes about three times more energy than a battery electric car for each mile driven. As of December 2020, there were 31,225 passenger FCEVs powered with hydrogen on the world's roads.[4]
As of 2019, 98% of hydrogen is produced by steam methane reforming, which emits carbon monoxide.[5]
If you think that you know better than those companies, it's an opportunity for you to create a start up in producing better hydrogen vehicles.
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Here are some problems facing hydrogen fuel cell.
https://www.inverse.com/innovation/review-2021-toyota-mirai
Of course, there's a catch. Actually, several.
First, hydrogen fuel cells are expensive. They use lots of platinum, titanium, and carbon fiber between the fuel cell and hydrogen storage. Toyota sells this Mirai for $66,000 before government tax incentives knock more than $10,000 off the price.
And Toyota is probably losing money on every single one it sells.
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If you think that you know better than those companies, it's an opportunity for you to create a start up in producing better hydrogen vehicles.
No need. There are plenty of investment opportunities in companies that are already manufacturing them.
They use lots of platinum, titanium, and carbon fiber
Titanium and platinum are recyclable. Carbon fiber is cheap. Lithium battery technology has had the advantage of mobile phone development to offset the R&D costs but hydrogen cell technology hasn't yet had a mass market.
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Possibly if/when it did, that would change things. It almost certainly won't anytime in the next ten years or so.
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No need. There are plenty of investment opportunities in companies that are already manufacturing them.
You can file a patent for your advanced hydrogen technology, which is presumably much better than Lithium battery. It's up to you if you want to collect royalty, or give it for free as your contribution for humanity in fighting climate change.
Titanium and platinum are recyclable.
You can't recycle them while being used. More fuel cells being used requires more platinum and titanium.
Lithium is also recyclable, cheaper, and more abundant than platinum.
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You can file a patent for your advanced hydrogen technology,
No need. It's already well patented and in production. It has been to the moon a few times and is now running around the streets of Britain.
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LOL! That won't get you very far. After decades, there's still only 14 hydrogen fuel pumps in the whole of the UK! And they're not exactly being installed at an enormous rate.
Meanwhile, every grid-connected 13 amp socket in the whole of the UK is capable of charging an electric car, and there's over 18000 charge points, 555 were added in the last month alone.
https://www.zap-map.com/statistics/#points
Hydrogen fueled cars are ABSOLUTELY a con-job that the fossil fuel and car industry are promoting to try to prevent more electric cars being built.
Just wait for the hydrogen car! You'll be able to refuel in seconds they say! And they've been saying it for decades! Meanwhile there's virtually no hydrogen cars, there's virtually nowhere to refuel them, and even if you could the fuel costs is multiple times that of electricity or even fossil fuels. Just a dead-duck technology.
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https://www.orkney.com/life/energy/hydrogen
https://www.nextgreencar.com/review/toyota/mirai/82099
might give you a different view of the future - and indeed the present.
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No, not at all. This guy has ranked uses for hydrogen between unavoidable and uncompetitive, and it all seems pretty reasonable. You'll note that passenger FC cars are at the uncompetitive end of the range.
https://twitter.com/MLiebreich/status/1426900737313984514?s=20
(https://pbs.twimg.com/media/E81ebz1X0AU7h9z?format=jpg)
(https://pbs.twimg.com/media/E0w-5WgXEAENPZX?format=jpg&name=large)
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Reminiscent of the US Academy of Science telling the Wright Brothers "There is no conceivable military use for the airplane".
passenger FC cars are at the uncompetitive end of the range.
The Toyota Mirai is price-competitive with the nearest Tesla, and a better build quality. It doesn't have the same mindboggling acceleration (yet - the present boost battery is very small) but has twice the range and a tenth of the refuelling time.
Not that either is a serious competitor to the horse, of course. The future is full of dangerous unknowns, and best ignored.
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The Mirai is not really very competitive in fact, not being able to refuel at home is a complete show stopper for most people shopping for a green car:
(https://pbs.twimg.com/media/E81iEUpWQAMjLYU?format=jpg)
The Mirai is selling very badly.
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Reminiscent of the US Academy of Science telling the Wright Brothers "There is no conceivable military use for the airplane".
Alternatively, someone in the past might have said that Zeppelin has no future. Time will tell which analogy has more resemblance with hydrogen cars.
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Really the market's already spoken. Nobody is buying these cars that are significantly worse in almost every way and more expensive compared to plug in electric cars.
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Nobody bought petrol cars in 1890. You can refuel a horse in your back garden.
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I can refuel an electric car in my garden.
I can refuel a petrol or diesel car in my garden, as long as I don't mind walking up the road with a jerry can.
Odd as it may seem, I don't have 700 bar hydrogen on tap and I'm quite happy about it.
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Yup, around1890 you could simply buy petroleum products at any local chemist and pour it into your car, and off you go. So until you can get kilograms of hydrogen at your local Boots, or any other large scale distribution center, then hydrogen cars are non goers.
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Until 1966 I could get 50% hydrogen from a tap in my kitchen. The grid still exists and currently delivers methane but
https://eandt.theiet.org/content/articles/2022/01/britain-s-gas-grid-preparing-to-accept-20-per-cent-hydrogen-mix-by-2023
suggests that it will eventually deliver 100% hydrogen at the 100GW required for heating and transport.
85% of UK homes already have a grid gas supply, as do most industrial parks and business developments, so unlike electricity, the additional infrastructure requirement will be negligible.
We still have to generate the electricity somehow, but let's ignore the weight of that elephant for the time being. At least gas gives us the option of cheap bulk storage, using technology developed 150 years ago.
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The engineering problem with aircraft is that hydrogen storage in the wings is inefficient as a wing has a large surface/volume ratio (= significant heat input) so you have to rethink the configuration with the fuel tanks in the fuselage and flat fuel cells in the wings (for dispersal of waste heat) feeding multiple electric motor/propellors. A hydrogen-fuelled jet engine may well be feasible but doesn't seem to have hit the headlines just yet.
A concise summary of the challenges associated with hydrogen and aviation: https://www.canarymedia.com/articles/air-travel/hydrogen-powered-planes-could-handle-a-third-of-passenger-air-travel-study-finds (https://www.canarymedia.com/articles/air-travel/hydrogen-powered-planes-could-handle-a-third-of-passenger-air-travel-study-finds)
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Rolls-Royce are also investigating hydrogen as an aviation fuel. There are a number of "blended wing" bizjet designs on the drawing boards right now, and at least one functional prototype with the right format for conversion to hydrogen power.
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Until 1966 I could get 50% hydrogen from a tap in my kitchen. The grid still exists and currently delivers methane but
https://eandt.theiet.org/content/articles/2022/01/britain-s-gas-grid-preparing-to-accept-20-per-cent-hydrogen-mix-by-2023
suggests that it will eventually deliver 100% hydrogen at the 100GW required for heating and transport.
'Eventually' is doing a lot of work in that sentence.
That was nearly 50 years ago. NONE of the grid is suitable for 100% hydrogen right now. Maybe if they inspected and modified every appliance, and checked every inch of the pipework, it might be suitable for hydrogen once again. Bit of a big job. It would take years, and in the meantime electric cars will be selling ever more quickly.
They're talking about maybe putting 20 percent of hydrogen in the grid; and even that is seriously challenging not only for distribution, but also production and cost.
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Maybe if they inspected and modified every appliance,
That's exactly what happened between 1966 and 1969. But the gas supply was nationalised at the time so people were able to think about safety and longterm costs rather than tomorrow's share price.
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Sure, but the safety works one way, the natural gas molecule is bigger than hydrogen, so replacing hydrogen with natural gas is easy you just change the jets, but the other way is hard because the hydrogen molecule is tiny and so leaks extremely easily, it's odorless, and is highly explosive, and burns with an invisible flame.
The easiest way to test for a hydrogen fire is to wave a broomstick around in front of you. If it bursts into flames, there's a hydrogen fire, try not to walk into it because spoiler: that's bad.
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Going back a few posts, I note that hydrogen has been declared by an expert consensus uneconomic and unfeasible for domestic heating and urban transport. Precisely the uses for which it was put in every city 200 years ago, and currently in Orkney, respectively.
I caught a short TV clip a couple of days ago, discussing high speed trains. It seems that one very promising bit of British technology was abandoned after a brief demonstration of feasibility. The vehicle had an aircushion suspension over an inverted T concrete track. I think it might be time to resuscitate the idea.
Now that we have to put concrete and steel barriers along the middle of motorways, why not raise the barrier height and run a concrete monorail along the road, with an aircushioned or maglev hydrogen-powered train floating over it? Fixed distance between termini means that you can start with just one or two refueling points, say London and Birmingham, with minimal environmental impact and speeds of 200+ mph. Hydrogen power offers a compromise between the fuel weight of a diesel generator and the cost and engineering limitations of overhead power lines.
At 200 mph, the train becomes time-competitive with air travel between all UK cities.
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Going back a few posts, I note that hydrogen has been declared by an expert consensus uneconomic and unfeasible for domestic heating and urban transport. Precisely the uses for which it was put in every city 200 years ago, and currently in Orkney, respectively.
The right economic comparison is between making heat by burning hydrogen generated by electrolysis using carbon-free electricity, and using the electricity directly to make heat. From a systems cost point of view, hydrogen loses in this comparison. First, electrolysis is at best about 75% efficient in capturing the energy content of electricity. So you need a lot more green electricity sources to make up for that loss. Second, you need an essentially duplicative energy distribution grid to get the hydrogen to where the heat is needed. The cost of that network raises again the cost of hydrogen relative to electricity. Finally, hydrogen is substantially less efficient as a source of heat in a home or building. A hydrogen fueled furnace is at best about 95% efficient in delivering the energy content of its fuel as heat; in all but the coldest climates, an electrically driven air-source heat pump can easily deliver 300% annualized efficiency (and in climates where there is any demand for summer cooling, the equipment for heating and cooling are essentially the same, so there is additional advantage there).
Over all, hydrogen from electrolysis loses the economic equation horribly as a domestic heat source.
Fixed distance between termini means that you can start with just one or two refueling points, say London and Birmingham, with minimal environmental impact and speeds of 200+ mph. Hydrogen power offers a compromise between the fuel weight of a diesel generator and the cost and engineering limitations of overhead power lines.
I agree on the value of high speed intercity trains. Far superior to air travel for most, and maybe all travel on the island of Britain and in most of Europe. When you figure in the ability of trains to move people city-center to city-center, I think the advantage is there for distances well over 200 miles. I have no opinion on air-levitated trains, although the idea makes sense. But trains, of all forms of transportation, most readily lend themselves to battery-electricity power. Refueling is a matter of switching discharged battery trucks off the train, and full charged ones on, or for that matter, if you're building an air levitated system, building induction recharging coils into select track runs. (In other words, I think the need for friction-contact overhead electrical lines is soon to pass). The mass disadvantage of batteries for transport that you've assiduously plugged here simply are not present in "rail" based transport options.
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The problem with nearly all green electricity is its unreliability. Given that the energy is free, it makes sense to find some means of storing it. Hence batteries (0.8 MJ/kg) or liquid fuel (43 MJ/kg) or hydrogen (120 MJ/kg).
It is true that a battery-powered train could be overall more energy-efficient than one powered by electrolytic hydrogen, but only before it moves. To deliver 8 MW for 3 hours (i.e to run a reasonable train from London to Aberdeen at 200 mph) a battery would have to weigh over 100 tonnes - about the weight of four carriages, not including the weight of the truck itself. Accelerating the battery truck to running speed will consume 30% of the train's power, so you will probably need to add another 20 tonnes or so. And you will need two battery trucks per train, one at each end of the track. This doesn't compare well with less than a tonne of hydrogen for the same trip. The only question is whether it should be oxidised in a fuel cell or a gas turbine to maximise power/weight ratio.
The huge advantage of airplanes is the absence of any infrastructure. As they say, a mile of road will take you nowhere: a mile of runway will take you anywhere. The hydrogen airlev train requires less infrastucture than a road but overhead wires are hugely expensive and require a lot of maintenance, and a track-powered maglev is even more complicated and capital-intensive. A battery maglev seems a bit like a low-flying elephant.
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The problem with nearly all green electricity is its unreliability. Given that the energy is free, it makes sense to find some means of storing it.
Yes, that is true for wind and solar. Not for geothermal or nuclear, both of which ought to be components of a carbon-neutral energy grid. With a well-considered mix of low-variability sources like those, and high variability sources like wind and solar combined with short and mid-term storage, you get a resilient, stable energy system.
But yes, you need storage. Hydrogen for storage is going to be a tough sell, though. It has the advantage of density, but the disadvantage of horrible efficiency. You lose 20% or more in making hydrogen from electricity, another 20% or so in reconverting to electricity, and a fair bit in managing it (if you liquify it to store it, you have another 30% loss; if you merely compress it, you've got at best another 10%). And a lot of equipment, since each stage requires completely different technology. I predict with high confidence that no one will build substantial electrical energy storage systems in the form of electricity to hydrogen to electricity full cycle. But I would also say that it's a question that is easily left to the market to decide. Grids will build hydrogen storage if it is cost effective for the volumes and cycles they need.
The hydrogen airlev train requires less infrastucture than a road but overhead wires are hugely expensive and require a lot of maintenance, and a track-powered maglev is even more complicated and capital-intensive. A battery maglev seems a bit like a low-flying elephant.
Not sure what you're on about here, since I said nothing at all about maglev. I was making the point that if you've got an air-levitated train, then you can probably power it electrically with relatively modest batteries that are recharged in-motion through induction coils in the train bed. An air-levitated train by design solves the problem of running the mass of the train along a fixed path with tightly controled, close approximation to the bed, so inductive power transfer to the train is a straightforward engineering challenge.
Accelerating the battery truck to running speed will consume 30% of the train's power
I think you're overly pessimistic here. Much of the energy used to bring the train up to speed goes into the kinetic energy of the train itself, and that can be efficiently recaptured back into the battery through regenerative braking.
Overall, levitated high-speed trains are almost the perfect platform for pure electric operation: tightly controlled, predictable paths that enable efficient energy use, coupling and recapture.
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Geothermal has very limited applicability. High temperature GT systems work in geologically active areas like Greenland but low temperature systems as in Marchwood, UK, have very low power output because they rely on thermal diffusion from the core, not frictional generation from tectonic plates.
Nuclear had its day when oil was cheap - it takes about 5 - 10 years to extract more energy from a nuke than you used to build it, so it made strategic sense as a bulwark against inevitable oil price rises, but civil nukes are probably uneconomic nowadays.
If you are going to recharge the airlev train by induction coils along the track, you might as well turn the track into a linear motor which gives you maglev and forward motion with no moving parts on the train. Huge infrastructure cost but very fast.
Adding 100 tonnes of batteries to the weight of the train means you need bigger motors to drive it, adding more weight, hence more batteries....it's the rocket problem. It is solvable, but rocketeers long ago decided that liquid fuel was the only practical solution. Kinetic energy recovery is significant at low speeds, so it enhances the performance of a 70 mph stop-start car, but at 200 mph or more continuous travel you are more concerned with aerodynamic drag - airplane speed increases with the square root of power - so there's not a lot to be gained by regenerative braking at the end of a 300 mile journey.
Where the resource is free, we tend not to worry about efficiency as long as the waste is nonpolluting. We throw away 90% of wheat plants to eat a tiny bit of sunshine. The energy loss in electrolysis can be used as domestic or industrial heat, and we reduce helium loss problem in MRI machines with a recirculating pump - hydrogen is a lot easier to reliquefy. The gas distribution grid is well established in the UK at least, and can be upgraded with 18th century technology.
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Kinetic energy recovery is significant at low speeds, so it enhances the performance of a 70 mph stop-start car, but at 200 mph or more continuous travel you are more concerned with aerodynamic drag - airplane speed increases with the square root of power - so there's not a lot to be gained by regenerative braking at the end of a 300 mile journey.
How do you get to that conclusion? Additional mass from battery doesn't significantly add air friction.
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Drag force = ½ρCDAV2 where ρ is air density, CD is the drag coefficient, A the effective area of the moving body and V its speed. Thus terminal speed ≈ k√(power) at subsonic speeds. Nothing to do with the mass of the battery, just the size and shape of the train.
Unlike cars, planes and trains can accelerate and decelerate fairly slowly but spend most of the journey in a constant-speed cruise at about 75% of full power, so the kinetic energy available for regeneration is a small fraction of the energy expended in cruise. Regen braking is used in all modern trains because it's more efficient and reliable than friction brakes but it doesn't have much impact on the energy required for a long trip.
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The problem with nearly all green electricity is its unreliability. Given that the energy is free, it makes sense to find some means of storing it.
Yes, that is true for wind and solar. Not for geothermal or nuclear, both of which ought to be components of a carbon-neutral energy grid. With a well-considered mix of low-variability sources like those, and high variability sources like wind and solar combined with short and mid-term storage, you get a resilient, stable energy system.
Nuclear and geothermal both only really work if propped up by renewables (especially hydroelectricity). If you haven't got a lot of hydroelectricity, you can never really have very high levels of nuclear power. It's not mostly a technical issue, it's primarily economic. (Although there are reasonably severe technical constraints on ramp times and power cycling in nuclear reactors).
Even if you have a lot of (non pumped) hydroelectricity, the key issue is seasonal variability of demand.
That's why France isn't 100% nuclear power. It only has nuclear baseload, and France is pretty much the global geographical best case for nuclear power. The UK SUCKS for nuclear because it has almost no non pumped hydroelectricity.
So the 'reliability' of nuclear doesn't do you a lot of good in the end. You still need backup from something else. Wind and solar just need pumped hydroelectric storage. It's quite a lot of storage, but it is as nothing compared to the amount of storage nuclear power would need.
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Drag force = ½ρCDAV2 where ρ is air density, CD is the drag coefficient, A the effective area of the moving body and V its speed. Thus terminal speed ≈ k√(power) at subsonic speeds. Nothing to do with the mass of the battery, just the size and shape of the train.
Then why did you say this?
It is true that a battery-powered train could be overall more energy-efficient than one powered by electrolytic hydrogen, but only before it moves. To deliver 8 MW for 3 hours (i.e to run a reasonable train from London to Aberdeen at 200 mph) a battery would have to weigh over 100 tonnes - about the weight of four carriages, not including the weight of the truck itself. Accelerating the battery truck to running speed will consume 30% of the train's power, so you will probably need to add another 20 tonnes or so. And you will need two battery trucks per train, one at each end of the track. This doesn't compare well with less than a tonne of hydrogen for the same trip. The only question is whether it should be oxidised in a fuel cell or a gas turbine to maximise power/weight ratio.
Adding 100 tonnes of batteries to the weight of the train means you need bigger motors to drive it, adding more weight, hence more batteries....it's the rocket problem. It is solvable, but rocketeers long ago decided that liquid fuel was the only practical solution. Kinetic energy recovery is significant at low speeds, so it enhances the performance of a 70 mph stop-start car, but at 200 mph or more continuous travel you are more concerned with aerodynamic drag - airplane speed increases with the square root of power - so there's not a lot to be gained by regenerative braking at the end of a 300 mile journey.
Tesla Semi prototype has been demonstrated to work well. Several Semis connected head to tail would resemble a train. At least it can be used as proof of concept.
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Then why did you say this?
I didn't say that battery mass affected air friction! I pointed out that, like a plane and unlike a car, most of the energy expended by a high speed train is lost in friction and drag during the long cruise phase and is therefore unrecoverable. A commuter train is different: like a car, it starts and stops frequently and rarely exceeds 50 mph, so regeneration can recover a significant amount of kinetic energy that would otherwise be lost by friction braking. Regen is indeed used for high speed trains but primarily as a means of slowing the vehicle, not for overall energy efficiency.
Having estimated the battery mass required to move a 4- or 8-car train 300 miles at 200 mph, we can calculate the total mass of the train and the fraction of that mass attributable to the battery. This then determines the power required to accelerate the whole assembly to its cruising speed in a reasonable time (say 0.1g acceleration), which determines the size of the motors and cooling system. For comparison, a Shinkasen car weighs about 4.5 tonnes and delivers about 1 MW. A 100 tonne 8 MW battery is a burden, not an asset!
Tesla Semi prototype has been demonstrated to work well.
Hardly a surprise - people have been using battery-powered goods vehicles for at least 100 years. But there's a huge difference in speed and payload ratio between road and passenger rail transport. The high-speed train is competing with airplanes, not trucks.
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So the 'reliability' of nuclear doesn't do you a lot of good in the end. You still need backup from something else. Wind and solar just need pumped hydroelectric storage. It's quite a lot of storage, but it is as nothing compared to the amount of storage nuclear power would need.
UK baseload is currently 20 GW and will probably double with the advent of electric road transport. At present we only have about 5 GW of nuclear availability, so it would make sense, at least in power terms, to build a lot more nukes. Indeed if we could settle on a single, known effective design, it might even make economic sense.
Daily demand fluctuation is another 0 - 20 GW on top of baseload. To meet this with renewables., assuming an all-nuclear baseload, we would have to install another 200 GW of generating capacity and 2,400 GWh of storage. That's a very big battery, but an entirely feasible hydrogen grid. Multiply by 3 if you don't build the nukes.
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If only we could take the battery off the train and connect it to the engine via the rails or wires or something...
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I pointed out that, like a plane and unlike a car, most of the energy expended by a high speed train is lost in friction and drag during the long cruise phase and is therefore unrecoverable.
Why cars are different? Which one has the bigger drag coefficient? SUV or bullet train?
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If only we could take the battery off the train and connect it to the engine via the rails or wires or something...
Of course we could. I took the train almost regularly a few years ago.
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A 100 tonne 8 MW battery is a burden, not an asset!
Hydrogen system is a bigger burden overall.
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If only we could take the battery off the train and connect it to the engine via the rails or wires or something...
Which is why the capital and maintenance costs of high speed trains require public subsidy. HS2 costs £1,000,000 per meter to build and god knows how much to maintain the track and wiring.
Why cars are different? Which one has the bigger drag coefficient? SUV or bullet train?
Cars start and stop frequently and don't exceed 70 mph. HS trains run for hours at a constant 200 mph. Drag depends on the square of speed, so even if a car and a train were the same size and shape, the train would dissipate 8 times as much unrecoverable power when cruising.
Hydrogen system is a bigger burden overall.
My London-Aberdeen example would burn 1 tonne of hydrogen. Fuel cell delivers about 2 MW/tonne, so add one power car to a Shinkasen 8-car set and get rid of the overhead wires and all that outdoor maintenance in the middle of nowhere.
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Which is why the capital and maintenance costs of high speed trains require public subsidy. HS2 costs £1,000,000 per meter to build .
I doubt that the wires are a big part of that.
I think the cost is pretty clearly not related to the actual physical track, but is essentially politics.
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If only we could take the battery off the train and connect it to the engine via the rails or wires or something...
Which is why the capital and maintenance costs of high speed trains require public subsidy. HS2 costs £1,000,000 per meter to build and god knows how much to maintain the track and wiring.
It does not cost £1m a metre, it is totaling £1m a metre due to many thechnical kickbacks in the same guise as the ppe covid contracts, exorbitant property purchaces and compensations and technical consultations that are exessive, overcharged and needless.
Cars start and stop frequently and don't exceed 70 mph. HS trains run for hours at a constant 200 mph. Drag depends on the square of speed, so even if a car and a train were the same size and shape, the train would dissipate 8 times as much unrecoverable power when cruising.
Cars will soon be computer driven meaning better flow and safety at higher speed. You will soom be able to get in a car and go to sleep, whilst the car does a steady 150mph to Scotland, rendering it faster than hs3 as that has a scheduled completion date to Glasgow of 2365ad.
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However it happens, that is the cost to the UK taxpayer, even before subsidising the purchase and running of the trains.
Clearly the simpler the track system, the fewer opportunities there would be for corruption in the contracting, hence a concrete inverted T track with airlev may be the only acceptable technology, followed by a maglev track with aluminum panels. Using the central reservation of a motorway eliminates the corruption of land purchase and access wayleaves. Nobody cares about the disruption of motorway traffic nowadays.
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You will soon be able to get in a car and go to sleep, whilst the car does a steady 150mph to Scotland,
That's 30 mph faster (and 20 minutes shorter) than steam trains 90 years ago, assuming that there are no roadworks on the M6 (never in living memory).
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You will soon be able to get in a car and go to sleep, whilst the car does a steady 150mph to Scotland,
That's 30 mph faster (and 20 minutes shorter) than steam trains 90 years ago, assuming that there are no roadworks on the M6 (never in living memory).
Yep but they will be able to travel faster through any problems any breaking will be managed throughout the traffic column, lanes can be switched direction. Admittedly it will slow the cars but a move able central reservation. Cars also have the advantage that they can negotiate corners where as hs2 seems only to be able to go through MPs Oxfordshire mansions and very expensive to traverse flat fields.
Construction of the 815-kilometer, $13.5 billion Zhengzhou East-Wangzhou line was completed in less than five years.
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I pointed out that, like a plane and unlike a car, most of the energy expended by a high speed train is lost in friction and drag during the long cruise phase and is therefore unrecoverable.
Why cars are different?
They aren't different. Above about 55 mph air drag dominates in cars. But even below that it's second only to rolling friction and similar loses of friction (brakes). Down around 30 mph it's mostly rolling friction.
It's quite a lot of storage, but it is as nothing compared to the amount of storage nuclear power would need.
UK baseload is currently 20 GW and will probably double with the advent of electric road transport. At present we only have about 5 GW of nuclear availability, so it would make sense, at least in power terms, to build a lot more nukes. Indeed if we could settle on a single, known effective design, it might even make economic sense.
Really no, Nuclear is more expensive than both wind and solar. Electric vehicles have enormous flexibility about when they charge and discharge. You do know that base load is supposed to be cheap? Any idiot can make expensive electricity.
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Electric vehicles have enormous flexibility about when they charge and discharge.
But does the driver have the same flexibility? Some people have wristwatches that tell them when to stand up and when to go to sleep. Clearly the sort of people who will stop driving and recharge their car when the wind blows and the car fancies a top-up. Time was that you couldn't get to France or America if the wind dropped: pretty soon you won't even be able to get to Tesco on a calm day.
You do know that base load is supposed to be cheap?
25% of your electricity bill is a tax to subsidise renewables (including compensation for not generating electricity when there is a surplus). 5% is just a tax. Half of the rest is profit to be distributed between shareholders and managers of the three companies who generate, transmit and meter it. Base load is indeed cheap (Economy 7 tariff is roughly halved at night - at least while electric cars are in the minority), but somebody has to pay for the unreliable stuff and the cost of privatisation.
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Yep but they will be able to travel faster through any problems
Including the 50 mph stretches of roadworks, 30 mph sections of "smart" motorways, and the 20-mile tailbacks caused by accidents and breakdowns? If you don't use theM1, M4, M6, M8 or M25 regularly, just listen to Radio 2 from time to time and ask yourself how a driverless car will magically tunnel through all the stationary traffic at 150 mph.
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Yep but they will be able to travel faster through any problems
Including the 50 mph stretches of roadworks, 30 mph sections of "smart" motorways, and the 20-mile tailbacks caused by accidents and breakdowns? If you don't use theM1, M4, M6, M8 or M25 regularly, just listen to Radio 2 from time to time and ask yourself how a driverless car will magically tunnel through all the stationary traffic at 150 mph.
Stationary traffic believe it or not is just a hairs breadth from peak flow volume. Swarm technology can enable cars to flow at far higher densities than human drivers can manage and at far higher speeds.
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Until one breaks down or needs to change lanes when the others aren't expecting it. And you'd have to ban any speed-limited vehicle from overtaking, and prevent any non-compatible vehicles from using the road. The problem is that cars are there to serve humans, not the other way around. On the other hand if you want to move 1000 people from A to B at 200 mph or more, a train will do the job nicely.
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Until one breaks down or needs to change lanes when the others aren't expecting it.
Nope, swarm technology copes as well with such situations, the point of a hive mind controller is that they do expect it.
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the point of a hive mind controller is that they do expect it.
Not when they break down. That's the ****ing point!
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No amount of software can make a car travelling at 150 mph pass though a truck doing 50 as it overtakes another doing 49 mph on a 2-lane road. Nor can it repair potholes, dig up the road to turn the emergency hard shoulder into a suicide lane without closing ten miles of track either side of the works, persuade a life member of the Conservative party to accelerate as she enters the motorway and weaves her inebriated way across the lanes to collide with a fire engine, or stop the idiot in font of you from trying to pay a toll with his blind person's bus pass. Will BMW drivers buy a machine that obeys the Highway Code?
As BC points out, it's just one more thing to go wrong.
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No amount of software can make a car travelling at 150 mph pass though a truck doing 50 as it overtakes another doing 49 mph on a 2-lane road. Nor can it repair potholes,
Hs2 will be a concrete pavement bed, concrete has a substantially a greater lifespan on UK motorways, it is very noisy which is why they covered them over. They don't suffer from subsidence, potholing etc. Replacement pavement sections can be slotted into place.
Cars can negotiate gradients, go round bends, bypass mansions, avoid faberge eggs. They can also seperate themselves from the traffic stream and go to many locations less than 50km from your door, all without a miltibillion pound station.
The hive technology manages the traffic congestion problems you list. It knows a problem and applies brakes and measures before the human driver can react.
www.thesun.co.uk/motors/17486363/radim-passer-259mph-bugatti-autobahn/amp/
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It's just after midnight on a clear winter night, and the M6 reports 10 points of congestion and broken-down vehicles, and 30 speed restrictions due to roadworks. Just right for a trip to Scotland at a constant 150 mph, eh?
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It's just after midnight on a clear winter night, and the M6 reports 10 points of congestion and broken-down vehicles, and 30 speed restrictions due to roadworks. Just right for a trip to Scotland at a constant 150 mph, eh?
Read this
https://en.m.wikipedia.org/wiki/Swarm_intelligence
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It's interesting to calculate the actual time taken for a journey. Consider London - Glasgow, say 350 miles.
According to the manufacturer, on a warm day you could drive a Tesla 350 miles at 50 mph, on a single 100 kWh charge, and take 7 hours. You'd be a few miles short if you used the aircon or heater, so dress for the weather. Let's generously assume that half the energy was expended on rolling friction, motor heat, etc. This means that we have expended 50 kWh on aerodynamic drag at 50 mph.
Now let's make the trip with Hamdani at 150 mph, in the same car.
We can calculate the drag loss at 150 mph, using the standard formula F = ½ρACDv2, as 50 x (150/50)2 = 450 kWh. Add the original 50 kWh for friction losses and we now need 500 kWh for the same journey. So we need to recharge the battery four times en route. As the battery will be hot, maximum charge rate will be about 40 kW, so the charge time will be 10 hours and the whole journey will take 12.3 hours.
For comparison, a comfortable 2 liter diesel "repmobile" (Skoda Octavia, Ford Mondeo, X-type Jaguar....there are plenty to choose from) will complete the journey at 70 mph with just over half a tank of fuel, in 5 hours.
Here's an interesting exam question: at what speed must the Tesla travel in order to make the journey in less time than the Skoda? Partial recharging (and a 30 minute pee break) is permitted.
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Read this
https://en.m.wikipedia.org/wiki/Swarm_intelligence
The defining quality of a swarm is that all its members are sufficiently similar to be able to conform to swarm behavior. So do we all drive 45 ton trucks, or should we transport cranes and tanks by motorbike?
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Read this
https://en.m.wikipedia.org/wiki/Swarm_intelligence
The defining quality of a swarm is that all its members are sufficiently similar to be able to conform to swarm behavior. So do we all drive 45 ton trucks, or should we transport cranes and tanks by motorbike?
How do you define sufficiently similar? Ants come in different shapes and sizes in a colony. Some of them can even fly.
I don't think that the differences create much of a problem if they are adequately covered by the software.
Also, the swarm members still have to interact with non-members. Even with inanimate objects.
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How do you define sufficiently similar? Ants come in different shapes and sizes in a colony. Some of them can even fly.
The ones that can't fly, don't swarm with the ones that can. And every swarm has a common purpose and destination.
Fact is that when you have lots of different vehicles travelling along a road, the system works pretty well if each vehicle is controlled by software that aims to get it to its own destination as quickly as possible without hitting another vehicle. Training that software takes a few hours during which it learns to cope with various road and weather conditions, interpret signage, anticipate the movement of pedestrians, and a whole load of other stuff. The software is incorporated in a bit of autonomous hardware that can also refuel the vehicle, diagnose faults, and even repair it. Best of all, said hardware is also the principal payload for many vehicles, and where it isn't the principal payload it can seek out and manage payloads, including distributing them to various destinations.
But I digress. We still have the problem that, regardless of software, an electric car at 150 mph takes more than twice as long to get to Glasgow than a diesel car at 70 mph.
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https://cleantechnica.com/2022/02/11/porsche-explodes-the-evs-arent-good-for-long-distance-traveling-myth/
Porsche Explodes The “EVs Aren’t Good For Long Distance Traveling” Myth
A Porsche Taycan recently completed a coast to coast journey, during which it spent a mere 2 hours, 26 minutes, and 48 seconds plugged in to a charger. By doing so, it exploded the myth that electric cars are no good for long distance driving.
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https://cleantechnica.com/2022/02/11/porsche-explodes-the-evs-arent-good-for-long-distance-traveling-myth/
Porsche Explodes The “EVs Aren’t Good For Long Distance Traveling” Myth
A Porsche Taycan recently completed a coast to coast journey, during which it spent a mere 2 hours, 26 minutes, and 48 seconds plugged in to a charger. By doing so, it exploded the myth that electric cars are no good for long distance driving.
The 300 million car loving Americans charge points is a problem. Plus the 200,000 dollar price of a porsche and the hideous efficiency of turning shale gas into electric car mileage, 0.45 powerstation x0.8transmission x0. 85 fast charger x0. 9 car efficiency, plus the carbon invested in the car itself. At present electric vehicles are causing an increace in c02 emmissions. And will be until we can supply 100 percent electricity from renewables etc. Read this
https://en.m.wikipedia.org/wiki/Swarm_intelligence
The defining quality of a swarm is that all its members are sufficiently similar to be able to conform to swarm behavior. So do we all drive 45 ton trucks, or should we transport cranes and tanks by motorbike?
This must be a wind up.
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https://cleantechnica.com/2022/02/11/porsche-explodes-the-evs-arent-good-for-long-distance-traveling-myth/
Porsche Explodes The “EVs Aren’t Good For Long Distance Traveling” Myth
A Porsche Taycan recently completed a coast to coast journey, during which it spent a mere 2 hours, 26 minutes, and 48 seconds plugged in to a charger. By doing so, it exploded the myth that electric cars are no good for long distance driving.
Fine. 0.32 kWh per mile is pretty much par for driving at 50 mph, so no big deal. Since US speed limits are mostly 70 or 75 mph it is doubtful whether the trip averaged more than 60 on the road.
Driving across the USA in a coal-, oil-, nuclear- and gas-powered car* is no big deal either, though diesel actually produces less CO2 per mile, is more thermally efficient, and doesn't require any new infrastructure.
Maximum recharge rate for lithium batteries is very temperature-dependent. Driving at a consistent 60 mph will heat the battery, so you can't fast-recharge as soon as you stop . Not a problem as few people would relish driving more than 350 miles in a day, so you stop, maybe overnight or for a good meal and crew change, and don't recharge at 350 kW until the car has cooled down to max-recharge limits. Your 20-minute recharge has turned into a minimum 3-hour stop, thanks to chemistry and physics.
Now calculate how long it would take at 150 mph, and how many fast-charge stations you would need to visit en route.
Go electric: more haste, less speed!
*about 20% of US installed electricity generating capacity is wind, maybe 10% solar, but unlike Europe, most of that is off-grid, supplying specific rural enterprises and not available to the fast-charge network.
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Now let's make the trip with Hamdani at 150 mph, in the same car.
We can calculate the drag loss at 150 mph, using the standard formula F = ½ρACDv2, as 50 x (150/50)2 = 450 kWh.
Add the original 50 kWh for friction losses and we now need 500 kWh for the same journey.
No. Really, that would be the same as you assuming that the friction losses have gone up quadratically as well, and then added them on again for no apparent reason. That's not in any way correct, the drag losses were lower to start with, and the rolling friction losses should have gone up linearly.
It's not that hard to do this properly, the Cd factor and frontal cross sections for Tesla cars are available.
But let's take that 450 kWh even though it is a gross overestimate, knowing full well that it's too high.
So we need to recharge the battery four times en route. As the battery will be hot, maximum charge rate will be about 40 kW, so the charge time will be 10 hours and the whole journey will take 12.3 hours.
Uhhhh no.
Your numbers are just garbage.
I thought you were an electrical engineer. You do know how batteries work???
They charge and discharge at the same maximum rate.
How is it that you think a car can output a particular high power for hours but then when it comes to charging, suddenly they have to charge four times slower than they were discharging minutes before????
These battery packs are ACTIVELY COOLED, even when charging. ESPECIALLY when charging.
The fastest Tesla chargers are 250 kW. Given that a 100 kWh Tesla will start fully charged it needs 350 kWh of charge. 350/250 = 1.4 hours. So the trip will take nearer 3.5 hours, an average of just under a hundred miles per hour.
Note that you would stop multiple times and do partial charges. Electric cars charge fast initially at low battery state of charge and then slow down, so it's fastest to partially charge the battery each time and do more stops. The exact time will depend on how far apart the super fast chargers are. But even so, your 12.3 hours is utter bollocks. You clearly know nothing about electric cars.
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I was being generous by not scaling the friction losses. But since you insist, let's take the published 0.32 kWh/mile at 50 mph and scale the whole lot quadratically to 150 mph, to get 2.9 kWh/mile. Now the coast-to-coast trip of 2800 miles or so at 150 mph requires 8120 kWh, or 82 charges of the 100 kWh battery. At 350 kW (max available from a superfast charger) that takes 23.2 hours.
So by going at 150 mph between charges we spend 42 hours on the road compared with 45 hours at 60 mph, assuming no cooling time or other charge rate limit.
I am quite familiar with the limitations of lithium batteries as I have an interest in electric aircraft. Pretty much the same as 150 mph cars, the recharge time with best present technology is at least as long as the flight time and can be more than doubled if the temperature is outside the optimum range of 5 - 45 °C (which it often is with airplanes). This makes a battery-powered selflaunching glider moderately attractive, or a trainer that returns to base for a battery swap after each sortie, but cross-country at 150 mph needs a lot of careful thought.
Sadly, active cooling requires power that would otherwise be available for motion, so there's another square-law effect to consider. Not a problem with IC engines that run at 100 °C or more, as heat transfer to a 20 °C ambient is very efficient (the problem with small aircooled planes is keeping the engine hot when the ambient is -40°C !) but to maintain a battery at say 30 °C is quite hard work.
When the charging grid matures, and we have discovered some way to power it, I'll be happy to drive an electric car at a sedate 50 - 70 mph, but the present technology doesn't lend itself to high speed transit.
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PS I work with a number of technicians who get called from home to unscheduled site visits. They have been issued with electric cars which delight them as they can claim for recharging time on long trips!
Apropos partial fast-charge times, I note that the "catalogue" number is always the recharge time from around 10 to 80%, so the 100 kWh battery actually only delivers 70 kWh for optimum overall performance (on a warm day).
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We can calculate the drag loss at 150 mph, using the standard formula F = ½ρACDv2, as 50 x (150/50)2 = 450 kWh
What is this formula, is it specific to something you know as velocity is rarely listed in mph or kph as they do not tally with joules etc. It's usually in metres a second.
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The formula F = ½ρACDv2 is in every aerodynamics textbook. v2 = v x v, whatever the units.
The numbers I used (0.32 kWh/mile at 50 mph) are culled from electric car manufacturers' websites - but what do they know about miles per hour, eh?
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The formula F = ½ρACDv2 is in every aerodynamics textbook. v2 = v x v, whatever the units.
The numbers I used (0.32 kWh/mile at 50 mph) are culled from electric car manufacturers' websites - but what do they know about miles per hour, eh?
Oh, a simple scaling operation giving 3 kwh for 3 miles (3 times the speed therefore 3 times the distance?)
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Energy = force x distance
3 times the speed => 9 times the force (v x v) so 3 miles at 150 mph requires 3 x 0.32 x 9 = 8.64 kWh.
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Except it's not because rolling friction is usually the biggest factor up to about 50 mph; and simple friction doesn't go up by a factor of 9 it is in fact linear, and the total energy needed to overcome it is independent of speed it's just distance. So at 50 mph, about half would aerodynamic drag. Your calculation assumes it's all aerodynamic drag and you've multiplied it by 9.
So 0.5 * 50 + 0.5*50*9 = 250 kWh. And you normally would have already would have fully charged to 100 kWh before you left. So 150 kWh left that you need to charge on route. That's 150/250 = 36 minutes (minimum) charging, and even the standard 150 kW chargers can do it in about an hour. You said: ten hours.
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So at 50 mph, about half would aerodynamic drag..
Which is what I said originally. I estimated the frictional loss as half of the claimed power expended at 50 mph, just as you said.
According to the manufacturer, on a warm day you could drive a Tesla 350 miles at 50 mph, on a single 100 kWh charge......Let's generously assume that half the energy was expended on rolling friction, motor heat, etc. This means that we have expended 50 kWh on aerodynamic drag at 50 mph.
then I used the standard formula to calculate the energy expended in aerodynamic drag to travel the same distance at 150 mph.
Energy = force x distance.
Drag force is proportional to (speed)2.
So drag energy is proportional to (speed)2 to cover a given distance at any speed.
It's a common enough calculation in aerodynamics - "Student Pilot 101" level, in fact.
And then I added the 50 kWh you allowed for frictional losses, to give 500 kWh required to travel 350 miles at 150 mph.
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Only HALF the initial 50 kWh would be rolling friction. You didn't subtract that off first before multiplying it by the drag equation. The drag equation only applies to aerodynamic drag, NOT rolling friction.
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Energy = force x distance
3 times the speed => 9 times the force (v x v) so 3 miles at 150 mph requires 3 x 0.32 x 9 = 8.64 kWh.
That is 3 times the drag for the same distance at 3 times the speed, that is very convenient.
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Only HALF the initial 50 kWh would be rolling friction. You didn't subtract that off first before multiplying it by the drag equation. The drag equation only applies to aerodynamic drag, NOT rolling friction.
Let's start again.
The manufacturer says 100 kWh will take you 350 miles at 50 mph.
You say friction accounts for half the retarding force at 50 mph, and the friction force isn't speed-dependent.
So 50 kWh is lost to friction over 350 miles at any speed
And 50 kWh is lost to aerodynamic drag over 350 miles at 50 mph.
This is your arithmetic so far.
Now I calculate the energy dissipated by drag over 350 miles at 150 mph by multiplying 50 kWh by the square of the speed ratio. 50 x (150/50)2 = 450 kWh.
And then I add your 50 kWh friction loss to get a total of 500 kWh.
How would you calculate it, still using your data, please?
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That is 3 times the drag for the same distance at 3 times the speed, that is very convenient.
No, it is 9 times the drag force, over the same distance. Energy = force x distance.