This is exciting because it could reduce the capital expenditure needed for hydrogen production. The biggest reason we don't use intermittent electricity generation (wind, solar) for hydrogen production or desalination is that a significant fraction (~30%) of the total cost is capex.
The efficiency here is lower by a factor of 2 or 3 for electrical consumption (for now in the lab), but if you can get electricity at near zero cost for a few hours a day this could make economical sense.
Had to look capex up : business, finance CAPitalEXpense or CAPitalEXpenditure; A financial term for the initial costs of a business, in contrast to operational expenditure.
I think a big part of the reason we don't do it is that if negative/zero electricity prices were expected to be common in a location for many years, then it would usually be more profitable to build more transmission capacity to take that power to consumers who will buy it for more money.
The big reason for doing this is arbitrage across time. Solar generation is increasing exponentially, to the point where it makes sense to have excess generation and store it for night time. Hydrogen could be a companion technology for intermittent renewable energy sources.
The important metric for electrolysers now is not so much efficiency (although that's nice), it's capital cost. For use with intermittently available power capital cost becomes more important. This is different from the old notion of a hydrogen economy, using relatively expensive nuclear power to drive electrolysers 24/7.
It may also be nice if the electrolysers were reversible, so they could also act as fuel cells.
And in a world where meth heads are climbing under cars to steal catalytic converters we have a problem with small portable boxes full of precious metals getting up and walking away when nobody is looking.
Particularly in some rural areas which might be good for power generation.
Hydrogen can be stored in underground reservoirs, like solution mined cavities in salt domes and spent natural gas fields. The cost is as little as $1 per kWh of storage capacity. This is the great advantage of hydrogen over many other storage schemes, which have a much higher cost per unit of energy storage capacity.
There is also the per-power cost of charging and discharging equipment, but that's independent of per-energy capacity cost.
I don't believe the oxygen is kept. Even if it were, O2 is very cheap. Liquid oxygen is the second cheapest industrial liquid, after water. Maybe it would make sense to store O2 underground as compressed gas also, for use in Allam cycle turbines (which would prevent NOx formation and even recover the water of combustion for reuse.)
In fuel cell mode you're consuming oxygen, not purifying it.
What is the source on the price of liquid o2? That seems insane that it would be so cheap, don't you have to either chill the air until it condenses, or use a selective absorber to separate it from air?
My point was why waste purified o2 on the fuel cell when you could use air and then sell the o2?
Yes, you chill the air. You get to recover the "cold" from the nitrogen (by using the cold separated nitrogen to chill the incoming air via countercurrent heat exchange), so you're actually only chilling (without recovery) the oxygen.
Cryogenic air separation is done on a vast scale to get gaseous oxygen for the basic oxygen steelmaking process. LOX can be obtained by tapping off some of that rather than also using to chill the incoming air.
Liquid oxygen is definitely not the cheapest industrial liquid after water. Just the temperature required to maintain liquid oxygen makes this false on its face. Even oxygen gas isn't the cheapest gas.
Really? What’s cheaper? Oxygen is around $0.10 per kilogram in bulk. The only pure gas that’s cheaper is maybe nitrogen. I’m not sure liquid nitrogen is cheaper than oxygen, however, since the boiling point is significantly lower.
What industrial liquid other than water is cheaper than liquid oxygen? What is significantly lower than $100/tonne?
Just recently methanol was $378/ton in small amounts. In 2019 it was between $200/ton and $300/ton. I'm too lazy to do the price deflation--and I wouldn't know what deflator to use--but that seems like it would have been at least comparable.
It takes about 200kWh per tonne of oxygen separated. If it’s mostly electricity price (therefore total price is at most twice the electricity price), and your industrial electricity is 7¢/kWh (common in the US), then you’re saying the total price of liquid oxygen is no more than about $30/tonne, even lower than my $100/tonne.
Our existing natural gas pipelines can handle storing up to 10% added hydrogen gas. If we were to start ramping up biogas production from waste streams we could produce some, if not all of the methane that goes along hydrogen in natural gas. This would utilize existing infrastructure, and help with energy production at night (think heating) when solar is unavailable.
Hydrogen is only difficult to store if it is pressurized, at low pressures there are low losses due to adiabatic expansion. Embrittlement is only a concern when you're holding back high pressures, and isn't a big concern for pipelines which can conceivably hold a large amount of reserve fuel.
I think the purified oxygen is an overlooked resource, as it can be used at, or near, the electrolizer as a method of producing pure syngas from waste organic matter using gasification. Normally woodgas or producer gas isn't desirable because it is made from atmospheric air as the oxidizer which contains a large amount of inert nitrogen which takes up space and produces nitric oxides at high temperatures. By using pure oxygen one can produce higher temperatures in the gasification reactor, and a purer syngas. This could be stored, and then used along with the hydrogen to produce heat and electricity in existing natural gas turbines when it is needed.
The use I would think of for the oxygen would be burning fuels in Allam cycle turbines. These use supercritical CO2 and burn fuels with oxygen in the CO2 (oxygen is needed so nitrogen doesn't build up in the CO2). The products of combustion are water and CO2. Water condenses and can be reused (an Allam cycle turbine burning natural gas would be a net producer of liquid water); CO2 from burning natural gas would be tapped off in pure form at zero marginal cost (unlike other CO2 capture methods.)
Allam cycle turbines burning hydrogen would not make CO2, of course, but they'd avoid the need for NOx reduction stage after the turbine. One could also imagine a system where CO2 is captured and stored, then used to make methane from hydrogen, that is also then stored. You'd need three kinds of storage reservoirs (methane, CO2, and oxygen) but perhaps this could be easier than storing hydrogen.
I'm curious if this could be utilized with less pure fuels such as organic wastes rich with oils and waxes. Supercritical CO2 is often used to remove oils and waxes from organic matter and clothing. The high temperatures and pressures might even be sufficient for pyrolysis of the organic matter, allowing for further removal of combustable materials. Of course organic materials are highly variable and full of other volatiles that may harm the turbines (i.e. sulfur, fatty acids, etc.). Sadly the purity of the exhaust gases would likely be effected as Nitrogen from proteins, along with other elements are going to end up in the exhaust stream. These could all be distilled out, or scrubbed, but with higher energy costs.
Still there are lots of exciting developments that can be made to cogeneration power production using organic waste streams.
Agricultural waste seems like a better use case, but that's just my sensibilities. A fluidized bed of 700C supercritical CO2 would be able to thermally crack woody biomass quite effectively. The remaining biochar could be used for carbon sequestration (reverse mining) by adding it to soil as an amendment to improve it's nutrient holding capabilities, ion exchange and friability.
They are decreasing by a factor of 200, which means 1/200 of the starting amount.
English is not my native language so I was a bit confused by "200 times less", which I (wrongly) imagined to mean starting amount (x) minus 200x, getting to -199x, which didn't make sense. Math in speech is a tricky thing.
The trick is in the word "times". In english every kid learns the "times table" ie "3 times 5 is 15; 6 times 7 is 42" so in this case "200 times less" means x/200. Live and learn, especially in a second language :)
I am a native English speaker and this annoys me as well. 200 times less sounds more impressive than 99.5% less even if it's kind of ambiguous. Same with saying it only needs 1/200th the amount. They want big numbers in the headline and people will figure out what they meant.
You're adding a 200% of speed, which is twice the nominal speed (the 100%). Given the nominal speed is 1x and you're adding 2x, you end with triple the magnitude of the original nominal speed.
It would be nice if this were the universal meaning of this phrasing but people do use it to mean both "twice as fast" (2x) and "faster by double the original speed" (3x).
People will rail about them using it wrong but it's pretty useless when you have to basically guess whether people subscribe to your definition of "right" before you can understand something.
After some clever engineering, it now runs 50% faster. Its speed is now 100% (baseline) + 50% (improvement) = 150% of 1 m/s (original speed) = 1.5 * 1 m/s = 1.5 m/s
The budget option runs 20% slower than the original model. Its speed is 100% (baseline) - 20% (derating) = 80% * 1 m/s (original speed) = 0.8 m/s.
The only reason to have “per cent” (%) as a concept is because decimal fractions weren’t invented yet when per cent was first used; until the past few centuries arithmetic was almost exclusively done in terms of integers or ratios (or various mixed units depending on the material being measured). Using 1/100 as a generic unit was a work-around to make numbers less than one easier to compare and recognize by turning them into 2-digit whole numbers instead of needing to do a careful computation to judge between say 5/13 vs. 3/8.
There’s not really any particular advantage to saying 0.005 of the amount (or 1 – 0.995 of the amount) vs. 200 times less. Personally I find it significantly less clear (though not really any more or less “impressive”), because doing mental decimal arithmetic takes some extra effort and leaves more room for confusion. That is, it is easier to reason about multiplying or dividing some quantity by 200 vs. multiplying or dividing by (1 – 0.995).
But the two numbers are reciprocals; this is grade-school rational arithmetic, not some kind of trick.
I am a native English speaker, but I also despise this phrase. Exactly because it's so awkward that it's hard to truly know what the speaker means. This pattern is unfortunately common. In my experience when used, they mean "reduced by a factor of 200" but they say "200 times less" as...shorthand?
Latin: Cubum autem in duos cubos, aut quadratoquadratum in duos quadratoquadratos & generaliter nullam in infinitum ultra quadratum potestatem in duos eiusdem nominis fas est dividere cuius rei demonstrationem mirabilem sane detexi. Hanc marginis exiguitas non caperet.
Translation: It is impossible to separate a cube into two cubes, or a fourth power into two fourth powers, or in general, any power higher than the second, into two like powers. I have discovered a truly marvelous proof of this, which this margin is too narrow to contain.
Fermat's Little Theorem (much more useful in practice):
French:Tout nombre premier mesure infailliblement une des puissances − 1 de quelque progression que ce soit, et l'exposant de la dite puissance est sous-multiple du nombre premier donné − 1; et, après qu'on a trouvé la première puissance qui satisfait à la question, toutes celles dont les exposants sont multiples de l'exposant de la première satisfont tout de même à la question.
Translation: Every prime number [p] divides necessarily one of the powers minus one of any [geometric] progression [x, x², x³, ... ] [that is, there exists a such that p divides xª – 1], and the exponent of this power [a] divides the given prime minus one [divides p – 1]. After one has found the first power [a] that satisfies the question, all those whose exponents are multiples of the exponent of the first one satisfy similarly the question [that is, all multiples of the first a have the same property].
I'd guess Netwons Principia would be a good example, given it basically became the founding work of a mathematical approach to physics, gravity, newton's laws of motion etc.
The book is written in Latin and contains diagrams and text to describe each lemma and law. Geometric proof seems to feature heavily!
This is a horrible language hack perpetrated and perpetuated by people who think a form like "a/one two-hundredth" is some kind of fancy-pants pointy-haired intellectual nonsense that will lose their target audience of the mathematically and grammatically illiterate. Oh well.
So... this is a fuel-cell-adjacent technology, and as such you need to read announcements like this with a somewhat cynical eye. I have no reason to doubt the science here. It probably works, or certainly is no less likely to fail than any other new technology.
But here's the thing: PEM electrolysis promises to reach hydrogen production efficiencies of... 80% or so, using exotic materials and entirely new chemistries. Regular DC electrical electrolysis (literally the "stick a wire in water to make bubbles" experiment we all did as kids) is starting out around the 65-70% mark. This just isn't that much better.
And doubly so when you realize that the most efficient reconversion of that hydrogen to electricity is going to lose another 20%.
This is better, but it's only incrementally better. 30% cheaper hydrogen would be nice, I guess, but it's not going to change any fundamentals of the energy economy.
> "And doubly so when you realize that the most efficient reconversion of that hydrogen to electricity is going to lose another 20%."
I think the real value of water-sourced hydrogen is going to be in three fields: synthesis of ammonia (atmospheric N2 + H2 -> NH3), direct reduction of iron ore to sponge iron (FeO + H2 -> Fe), and synthesis of methane and jet fuel (Sabatier and Fischer-Tropsch processes, respectively).
Yes. But you don't plan on an entirely new organization of the energy economy on the basis of that. To pick other examples: VLSI scaling happened first, then the software industry explosion. Lithium batteries arrived first, then people started developing mobile devices (and eventually cars).
Planning on this great new "hydrogen economy" thing when even the best-case theoretical technologies represent only a mild improvement over what we have isn't responsible punditry, it's just playing "What if George Jetson had a Jetpack?" games.
Hydrogen doesn't suddenly appear to create a new kind of market, like sudden availability of jetpacks would.
Burning remainders of dinosaurs is on the decline. It is frowned upon by many due to CO2, it is not always readily available (see current war), and finally supply is limited. This leads to a decrease of availability, and at continuing demand an increase in price. Unavoidable.
Prduction of electrical power from renewables is the cheapest form available already today. Also, it can scale without any practical limit. Power just isn't always available when needed, with surplus production at other times. Any improvement in storage cost (mainly device cost, much less efficiency) decreases the price of power from storage.
At some point, the price of power from storage will drop below the price of power from fossil fuels. No magic step will be needed, simply increasing/decreasing prices will meet at some point.
> The one change everybody is waiting for is excess renewables capacity at peak times
That's already the case in the northern parts of Germany. On windy days feeding excessive electricity to all neighbors, and still shutting down some wind turbines. The local energy company is planning 320 MW hydrogen production [0].
> Yes. But you don't plan on an entirely new organization of the energy economy on the basis of that.
These kind of breakthroughs change the economics and composition of the new energy economy. They are not a challenge to the fact that harmful, limited, fossil energy is a very cheap and simple way to run an economy for a century or so.
80% isn't amazing, it's not ideal for an electric car, but it's not terrible either. IMO, to switch to 100% renewables, we're going to need grid-scale batteries, but it might also help if we had a mechanism to achieve seasonal energy storage.
I know hydrogen is hard to store, so I think it would be best if we could somehow use electricity to produce ethanol directly from CO2 and water (is that feasible with reasonable efficiency?). But just imagine if we could, in the summer, we could turn excess solar power into ethanol and stockpile it for the winter. We could also use that fuel to power jet airplanes and cargo ships without using any fossil fuels.
CO2 to hydrocarbon fuels (not ethanol, but methane and potentially liquid hydrocarbons as well) is exactly what Terraform Industries is planning to do.
I’ve always worried about the energy density of batteries. They’re explosive enough as it is, imagine if it was 10x worse. I’ve always hoped that we’d transition to synthetic fuel - fuel like diesel is surprisingly stable and safe.
Fuel infrastructure burns all the time, though. It's like every month there's a video of some tanker overturned on the highway, or a refinery fire, or a gas explosion. I don't have statistics in front of me but I'm all but certain that lithium batteries as deployed today are safer by pretty much any metric you want to pick.
the batteries explode because of the materials in them, not because of the stored electrical energy. An full lithium battery wouldn't explode much more violently than an empty one.
I fly FPV so I deal with exploding batteries from time to time. Fully charged batteries explode much more violently than discharged batteries which tend to smolder instead. I suspect the additional electric discharge is adding ‘fuel to the fire.’
Interestingly, a discharged lithium ion battery still has electric potential in it, it's just that we stop discharging it after it hits a cutoff voltage to protect the battery's lifespan.
I wonder if a truly 100% discharged battery (down to zero volts) would actually be basically inert, and not even smolder if you poked it.
Lithium Ion batteries do burn much more readily when fully charged than when discharged -- this is because they self-discharge rapidly at elevated temperatures, which provokes an even greater reaction of the materials inside of them. Specifically, if the cathode of NMC/NCA batteries gets hot enough, it will decompose into oxygen and really kick off the graphite + electrolye burning.
Discharged batteries are tougher to get to burn since it's harder to heat the cathode to that point externally so oxygen has to come from the environment.
This is not correct and is against basic thermodynamics and conservation of energy. Store a whole bunch of potential energy somewhere and you have an explosive. The more stored energy of any form, the bigger the boom.
I’m no expert on this but it certainly seems conceivable that a 30% cost reduction can be the difference between “not profitable” and “profitable”.
In regards to the efficiency argument against hydrogen: Sometimes that is an issue but sometimes it’s just not an issue at all. Fossil fuel efficiency is abominable but they’re still used.
If hydrogen would only halve the amount of usable energy, it would already offset the difference in a perfectly sunny location and one that's often cloudy. The case for wind energy is probably similar.
Only if you have something nearby that needs low-grade heat, like warming buildings. Waste heat is a diffuse source of energy that's not worth the infrastructure cost of transporting more than a few miles.
Green hydrogen in theory is valid and a very worthy target of research.
In practice it remains a FUD/policy distraction by petroleum interests to develop an energy ecosystem that is reliant on fossil fuels for the foreseeable (and profitable) future.
This is research that falls into the former category, but it's presence and other "green hydrogen" headlines in the news feed is due to the influence of the latter.
The economics of solar/wind/battery are and will be the driver of primary carbon reduction for the next decade, likely two decades.
Practical hydrogen has the same issue new nuclear has: what price target? LCOE and many other measures of solar/wind/battery have fallen at 10 percent or more per year for the last decade, and while "who knows" when that exponential curve tails off, looking at the scale of what's needed, forthcoming techs like perovskites and forthcoming production of sodium ion / LFP / LMFP and the prototypes of Lithium Sulfur / Solid State in batteries, there is likely another decade of improvement at those rates.
So like "new nuclear", sure, keep up the research, and if price competitive applications can compete with sodium ion batteries (which I think will be a killer app in grid storage based on the materials and gravimetric densities), sure, but I think these techs will be kind of like magnetic RAM vs DRAM: it simply missed the boat of the economies of scale rampup, and now has to wait for that curve to stabilize before anything competitive can crop up.
For hydrogen to be practical in any green form in large scale requires a huge development in generation (which this is), storage, transport, and infrastructure. Fundamentally that hydrogen creation/transport/storage/delivery infrastructure, which is 99.99999% unbuilt, competes with the existing power grid, which likely has TRILLIONS of dollars in accumulated investment and will receive likely another trillion or two globally over the next two years to adapt to dirt cheap solar and wind, to say nothing of what will be invested in home / commercial distributed solar generation and battery storage which hydrogen is not applicable.
Big Oil had a chance when the Bush Administration was talking about hydrogen circa 2003. But the fat cats sat on their hats, and Tesla and solar/wind left them in their dust. The only ones really pushing hydrogen are those and Toyota, who perplexingly missed the EV boat despite releasing hybrids in 1997 and should have been providing an entire product line of PHEVs by 2005 that pushed the entire industry towards PHEVs for all consumer transport by 2015. We'd be immune to OPEC and russia if that had happened, and 70-80% of daily miles would be electric with no range anxiety.
Electrolysis at scale has to happen for green hydrogen to replace coking coal in iron smelting/steelmaking (~9% of global carbon emissions)[1] and to replace steam reformation of fossil methane for making ammonia, for fertilizer (~1%).
Those applications don't require an elaborate transport infrastructure; just that the plants be located near large PV farms or vice versa.
Why write "trillions" in capital letters? Is it supposed to be impressive? A trillion dollars is one percent of global GDP. Oil, fossil gas, and coal extraction cost 5 TRILLION dollars a year, and the infrastructure for their use (vehicles, boilers, etc.) cost TRILLIONS more. And that's just to offset depreciation.
1. An alternative to using hydrogen for iron smelting is direct electrolysis of molten iron ore, but that is at early research stages. It can't be rolled out globally in the next four decades; development will take longer than that.
Presumably the electricity network can often be used to transport the power, so only the hydrogen electrolysis plant needs to be near the industrial consumer.
The possibility is very dependent on the network constraints to the load: there is often excess network capacity on many links or excess capacity at certain times of day, because the network is built to handle peak loads. There is also availability of capacity on network secondary-links that have reserved backup capacity (to handle failover from network primary-link failure).
One major constraint for green power is locating it near a network node that can accept the power.
Yes, although siting the electrolyzer at the PV farm uses DC from the modules directly, avoiding DC-AC inversion losses, transmission losses and AC-DC rectification losses. Having the smelter there too avoids hydrogen transport and storage costs.
All that, of course, has to be balanced against ore transport and slag disposal costs.
Network and conversion losses are often surprisingly small. For example a 600km DC link in NZ[1] has total losses of 1.42% on the first 323MW and 3.30% on the next 753MW[2] (age of rectification & inverter equipment varies). There is AC to DC conversion at both ends, so that is equivalent. DC transmission losses are less than an AC segment would be (220kV AC to 350kV DC with 40km underwater).
Because current investment in hydrogen infrastructure is likely ONE MILLIONTH of that ... or more. As in it is so far behind that there is no feasible way to catch up.
But mostly ecause numbers with lots of zeros are important to keep in mind.
If it's growing at tenfold per year, that's only six years' growth.
I don't know what the actual growth rate is, but I don't think there's cause for concern, except to coal miners.
Edit: there aren't any material limitations. The current hotness is proton-exchange membrane technology; the coming thing is solid oxide electrolysis (promises lower cost); the century-old technology (that has been ignored for most of that time, so hasn't been properly cost-optimised) is alkaline electrolysis using caustic potash or caustic soda.
Alkaline is slightly higher cost, but as I said no significant effort has been put into it for a while.
Yes, which is why CATL's sodium ion 160 wh/kg mass production in 2023 battery is such a big deal.
Hydrogen can grow 10x from where it is now because it is paltry in size, but then, no way. But as you yourself point out, hydrogen is all research and prototypes, but EV / Solar / Batteries / Wind is production or near-production.
At this point the planet needs what works now.
But will hydrogen extraction/electrolysis ever be cheaper than grabbing it from methane? I doubt it. That's one of the big big big issues with hydrogen, the "green hydrogen" supply chain can be exposed to fraudulently sourced hydrogen. Don't assume regulatory controls will be in place everywhere, companies will simply arbitrage the lowest common denominator regulation or under the table it. It happens to this day with petroleum from Iran and Russia.
Its always been my impression that the only practical use of hydrogen is as a pseudo battery to buffer energy from renewable sources. No need for expensive/dangerous transmission or fueling infrastructure if the hydrogen is stored in the same place it was generated, and then passed through a fuel cell to turn it back into juice when demand increases.
Your thinking ignores that there are many other uses for hydrogen. There is this chart [1] that clearly states where we should go for clean hydrogen production first and where it may not be worthwhile. And what I am noticing, that is more or less where the industry here in europe is going: some experiments in different areas but focus is the chemical industry and soon steel. Everything else will (mostly) come later.
Too expensive, too easily degraded by minor impurities in the fuel, not improving nearly as fast as batteries (their main competition). Using rare materials more efficiently would definitely help with the cost problem.
I'd guess the one important application of fuel cell tech that people often appear to forget is going to be long haul trucks where it'll replace the diesel power train.
It's a big chunk of overall land transport that IMO in the long-term won't have other technologically/economically viable options besides the fuel cell.
Rail doesn't serve the last few miles to the destination.
Electric trucks are viable for short distances.
Trucking dozens of tons of cargo over distances > 500 miles isn't going to roll well with carrying another 3-5 tons of battery. And having to recharge that at 2 MW every now and then would require a very reliable/available and ubiquitous high power charging infrastructure.
I think about 2 ton battery is closer to truth for a truck that has about 400-500 mile range. Less, if you consider all the heavy diesel engine and transmission parts an electric truck is not going to need.
Charging at the starting point while loading, at (mandatory) breaks and at the destination should be enough; a BEV truck done right shouldn't require extra waiting time.
> I think about 2 ton battery is closer to truth for a truck that has about 400-500 mile range.
A Tesla Model 3 has a ~ 500 kg battery and weighs ~ 2 tons. With the drag coefficient of a truck being significantly greater and its gross weight amounting to ~ 15-20 times that of the Model 3, I'd say your 2 tons are way off. Sure, the truck will go slower than the Model 3, but still.
Also electric motors do weigh a few kg's as well, so I'd guess the less heavy drive train of the electric vehicle isn't going to save all that much weight.
> Charging at the starting point while loading, at (mandatory) breaks and at the destination should be enough; a BEV truck done right shouldn't require extra waiting time.
I think this needs to be compared to the procedure with a diesel truck. The diesel truck needs a few minutes at the gas station to refill and get some Ad Blue or what. Then it's all flexible to go anywhere for a few hundred miles.
Compared to that, your BEV truck is going to need careful planning ahead of charging and any small deviation from the plan is going to be a lot more of a hassle than for the diesel truck.
Point being. Nope, there aren't many H2 gas stations either as of now. But once there are, the refuelling of a FCEV will be much more similar to that of a diesel/gasoline vehicle than that of a BEV, aka more convenient/resilient.
"A Tesla Model 3 has a ~ 500 kg battery and weighs ~ 2 tons. With the drag coefficient of a truck being significantly greater and its gross weight amounting to ~ 15-20 times that of the Model 3, I'd say your 2 tons are way off. Sure, the truck will go slower than the Model 3, but still."
A truck should consume about 5x than what a Model 3 LR does. 5x 445 kg (actual M3LR battery weight) is 2225 kg.
A shipping container measures w x h: 2.438 x 2.591 m
The total height of the truck will be > 3 m so we're talking about 2.438 m x 3 m projected area. That's ~ 7.3 m2
A Tesla S apparently has 0.562 m2 drag area so let's assume 0.6 m2 for the Model 3. [1]
This amounts to a factor of Semi to Model 3 of:
7.3 m2 * 0.36 / (0.6 m2 * 0.23) = 19
So at the same speed the aerodynamic drag of a truck will be almost 20 times that of a Model 3. Yes, a truck typically drives slower and speed goes into calculation of engine power at a power of 3. But the truck would have to go slower than the Model 3 by a factor of 19^(1/3) ~ 2.7 to have roughly the same drag.
If the Model 3 drives at 150 kph and the Semi at 100 kph, the Semi still has more than 5 times the aerodynamic drag.
And you'll have to add friction to that and losses for accelerating the greater mass. (I doubt regenerative braking will scale well with increased vehicle mass)
Your drag area figure for Tesla Semi is absurdly high.
Note that drag area is cross-sectional area times drag coefficient. If your numbers are otherwise correct, Semi's "drag area" should be 0.36 * 7.3 m^2 = 2.62800 m^2.
2.62800 m^2 (Semi) / 0.562 m^2 (Model S) is approximately 4.68. So I think 5x energy consumption is completely feasible.
> I doubt regenerative braking will scale well with increased vehicle mass
Why would that be an issue? 500 kWh magnitude battery can absorb about 7x power compared to a Model 3 LR AWD battery. Regenerative braking is probably only ever issue when the battery is somewhere above 95% full.
> Your drag area figure for Tesla Semi is absurdly high.
Don't think so. But I made a different error. See further down.
Drag equation [1]:
> FD = 1/2 * rho * u² * cD * A
> The reference area A is typically defined as the area of the orthographic projection of the object on a plane perpendicular to the direction of motion.
So A in the case of a truck carrying a standard container cannot be smaller than the section of the container. And because the container cannot hover millimetres above the ground but must rather be carried at a height of at least half a metre you'll have A > greater than the cross section of the container.
Which is what I calculated above.
I did make an error though by multiplying the drag area of the Model S by the drag coefficient, since the 0.562 m² already takes the coefficient into account.
So you're right, the factor Semi/Model S is ~ 4.68 based on the numbers I assumed.
It does look more feasible indeed based on this number.
Yet I'm still sceptic a battery 5 times larger will suffice because of higher friction and because I doubt regenerative braking will recover the same proportional amount of energy for the Semi as for the Model S.
Let's see. Decelerating the 20,000 kg Semi going at 100 kph at mild 0.10 g requires a force of 0.1 * 9.81 m/s² * 20,000 kg = 19,620 N.
At a velocity of 100 kph that equals (not taking drag and other friction into account) an initial (lossless) braking power of 545 kW that could be regained by regenerative braking. Okay, could be feasible as well, if charging can be ramped up to this rate within the fraction of a second.
If you brake at 0.5 g though, you'd have to suddenly feed in the ball park of 2 MW into the battery. Not sure that's possible.
> If you brake at 0.5 g though, you'd have to suddenly feed in the ball park of 2 MW into the battery. Not sure that's possible.
MCS [0] charging standard goes up to 3.75 MW. I don't think Semi can charge at that power, but 2 MW — why not.
Of course, the catch is that the higher the battery state of charge (SoC), the lower the charging current can be. 2 MW might not be possible, say, somewhere above 50-80% SoC.
That ignores all the existing infra (or lack thereof).
Fossil fuels are very energy dense, and we still have tons of truck stops everywhere - and need them!
Last mile, most dropoffs are not going to have power infra to allow MW+ Charging of every truck that shows up, at least not without a lot of time to upgrade. And many won’t want to even try, as they’re paying the logistics companies so they don’t need to deal with stuff like that.
Even distribution centers would struggle (capex wise), as we’d be talking 100s of megawatts at least of extra load, possibly giggawatts.
There has been no more meaningful progressive in batteries in over a decade. The energy density of batteries today (~265 Wh/kg) is marginally better than where it was in 2012 (~250 Wh/kg). It's been entirely a function of cost reduction. If this continues, people will need to stop talking about "rapid advances" in batteries and instead talk about stagnation.
The report is wrong. It doesn't even make sense since there is clearly a dot above 200 Wh/kg in 2012. Meaning the graph is only claiming a 40-50% improvement in the last decade.
But regardless, the report is wrong because we most definitely had reached 250 Wh/kg by 2010. Panasonic mass produced a cell with those specs start in 2009: https://news.panasonic.com/global/press/en091218-2
Furthermore, there is no way of buying that 300 Wh/kg cell shown on the chart. No seems to have ever found one available as a commercial product. Meaning it is likely an experimental cell that never made it to production.
The efficiency here is lower by a factor of 2 or 3 for electrical consumption (for now in the lab), but if you can get electricity at near zero cost for a few hours a day this could make economical sense.