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Look at volume instead of weight. Hydrogen is only 8 MJ/L in liquid form vs 38MJ/L for Diesel. Think of the space needed in the vehicle. Next creating liquid h

Look at volume instead of weight. Hydrogen is only 8 MJ/L in liquid form vs 38MJ/L for Diesel. Think of the space needed in the vehicle. Next creating liquid hydrogen is a very energy intensive process compared to refining diesel. Next energy in lithium batteries is converted to mechanical energy with +90% efficiency in a modern electrical motor. Fuel cells just like combustion engines are only 40-60%.

throwaway0a5e 5y ago
Most commercial trucks are lacking for weight, not for volume. They wouldn't use all those axles and tires if they didn't need to. Weight and charging time are the current major roadblocks to adopting batteries. Hydrogen theoretically solves those but introduces a lot of technical complexity along the way and needs a supply chain that currently doesn't exist.
- SigmundA 5y ago
  I don't see a lot of extra room on a truck for safe liquid hydrogen tanks 5 times the size of diesel tanks.
  - darksaints 5y ago
    That would be true for cars, not so much for trucks. Most trucks hit their mass limits long before they hit their volume limits. Most box trucks, for example, are transporting more air by volume than cargo.
    - SigmundA 5y ago
      Trucks have length limits and more constrained in Europe which is why you still see many cab overs there. The US loosened length limits in the 70's allowing for long nose trucks which help with aero dynamics and safety.
      - darksaints 5y ago
        So you don't store it on the tractor itself, you store it with the trailer. That's how your god Elon is proposing to do it with batteries.
        SigmundA 5y ago
        Yes with 10,000 psi hydrogen lines from trailer to tractor and expensive tanks on the trailer. AFAIK the Tesla semi has all batteries in the tractor. He is most certainly not my god.
        darksaints 5y ago
        The Tesla semi, without batteries on the trailer, is limited to about 500kWh of batteries...maybe 1000kWh if you have some extremely clever engineering. You can't really do much more than that without moving to a monocoque carbon frame to offset the weight, because the batteries are too dense. Commercial trucks have total weight limits, but they also have per-axle weight limits. If you are too heavy on a single axle, you're illegal. And while 500kWh batteries, are awesome and the perfect use case for local delivery, they won't cut it for OTR trucking. You need 700 mi of range at an absolute minimum for singles, ~2000mi for doubles. The weight of a 700 mile battery is a non-starter. Tesla's largest battery pack that they're even considering selling has a 500 mi range. There is a reason Tesla quotes kWh/mile, and not kWh/lb-mi (cargo, not GVW). They aren't competitive, and they likely never will be. And adding more batteries just makes the economics less competitive. There's a saying in the aircraft industry: it takes a lot of fuel to fly a lot of fuel. The same goes for batteries: it takes a lot of battery to move a lot of battery. Batteries, no matter what technical advances can be made, have limitations posed by the laws of physics, and none of them will ever have the energy density to make sense for long haul trucking. Which is why actual trucking companies that have actually beat His Lord and Savior Elon Musk to market with electric trucks (i.e. Volvo) are still looking to better alternatives in the long run.
        SigmundA 5y ago
        So now how much does a hydrogen fuel cell semi weigh whats its range? How much does it cost? Where do you fill it up? Current hydrogen fuel cell vehicles weight more than an equivalent battery powered car not not even looking at cost and power and refueling infrastructure. I agree that diesel is most viable for long haul and probably will be for some time and still has room to improve see Frieghtliners SuperTruck.
  - maxerickson 5y ago
    Split trucks have lots of room. https://m.youtube.com/watch?v=4Bk7-L7ffiY https://m.youtube.com/watch?v=4Bk7-L7ffiY
    - SigmundA 5y ago
      Long wheelbase sleepers are very difficult to maneuver, they are pretty specialized and you won't see them in Europe do to length restrictions.
      - maxerickson 5y ago
        Sure, but it's an absurd example of space not being a particularly critical factor. That thing is a huge factor bigger than the volume of the fuel tanks.
        SigmundA 5y ago
        Not sure why you say that, its very critical in Europe and still a concern in the US.
- marcosdumay 5y ago
  The problem with all those calculations is that storing hydrogen requires a lot of weight. If hydrogen were such a great idea, trucks would be already migrating to the in-between solution that is natural gas.
  - thehappypm 5y ago
    Trucks maybe aren't, but city buses certainly are, all over the country. That's likely because of the infrastructure. You don't need to dot the entire country with LNG stops for your city buses, just a few fuel-up points here and there around town.
    - marcosdumay 5y ago
      Yes, buses and taxis are big adopters of it. Maybe there is something there and if we cut the cost of hydrogen enough (you know, all that extra solar power must go somewhere), it will be interesting for them too.
  - albrewer 5y ago
    I second this insight. I'm a pressure vessel designer by trade. I got my numbers for all of this here[0] Liquefied hydrogen either needs to be stored cryogenically as a liquid, or at a very high pressure as a gas (65 MPa). I'm ignoring adsorption methods here. Given that we can't continuously maintain -253 °C all the time, this method is impractical for mobile usage. That leaves gaseous storage. To match the current range of diesel tractor-trailers, you'd need at least 4x the volume in hydrogen to come close to the standard of 600 miles between refills. I'm going to assume we need to store 1500 L of hydrogen to match the range. Other assumptions: The tank has a max overall length of roughly 2.5 meters. Inner and outer corrosion / gouge allowance of 6mm Design temperature of 200 °C (in case of fire). Material of construction is A-387 5 2 (5% Cr, 2% Mo steel) lined with something that prevents diffusion into and hydrogen embrittlement of the base metal. Vessel consists of a cylinder with spherical head on either end. Given: Inner diameter is 890mm, shell length is 1830mm, allowable stress is 178 MPa at the design temperature, we can use equation 4.3.1 from the ASME BPVC Section VIII Division 2 to determine the minimum thickness required for the given pressure. D is the corroded inner diameter of the vessel, P is the design pressure, S is the allowable stress, and E is the weld joint efficiency (assumed 1). D / 2 * (exp[P / (S * E)] - 1) + Corrosion 902 / 2 * (exp[65 / (178 * 1)] - 1) + 12 = 211mm wall thickness The weight of just the cylinder at that thickness with a length of 1.83m (without the spherical heads) is 11,000 kg. At that weight, batteries are pretty competitive. [0]: https://www.energy.gov/eere/fuelcells/hydrogen-storage-basics-0 https://www.energy.gov/eere/fuelcells/hydrogen-storage-basic...
darksaints 5y ago
SOHCs are approaching 100% conversion efficiency, and SOFCs have 60% baseline efficiency, and with practical heat conversion technologies, have closer to 75% efficiency. And they can use hydrocarbon fuels which can open up fuel options to synthetic fuels that have more reasonable mass/volume tradeoffs.
- SigmundA 5y ago
  Heat conversion is going to mean more equipment (heat recovery turbine?). SOHCS run at what 1000c? Don't see that being practical for vehicle use any time soon.
  - darksaints 5y ago
    Heat recovery turbines are awesome. A single moving part, that's it. And those temperatures are not a problem at all. Standard off-the-shelf calcium silicate insulation will work fine.
    - SigmundA 5y ago
      Single moving part and generator and power control. None of that is free in terms of complexity, weight and cost. This is on top of whats needed for the fuel cell, plus you will probably need a buffer battery to fully utilize. Makes more sense to look at heat recovery turbines for a diesel engine which is exactly what Freightliner is doing with their Supertruck bringing its thermal efficiency up around 60%.
      - darksaints 5y ago
        It makes less sense on a diesel engine because their heat sources are lower temp. Fuel cells produce much more useful heat for a heat engine to capture. And no, the complexity of heat recovery isn't high at all. The costs pay themselves off almost immediately. They're orders of magnitude less complex than an ICE, last almost forever, and require almost no maintenance apart from cleaning after tens of thousands of hours. If a modern heat recovery turbine is too complex, then so is an electric motor.
bildung 5y ago
OTOH, using the model 3 as an example, you have to drive around 480kg of batteries all the time, while the same energy (75kWh/270MJ) in hydrogen would only amount to less than 2 kg.
- SigmundA 5y ago
  You won't get 75Wh to the wheel with 2kg and the hydrogen tanks and fuel cells have weight.
  - bildung 5y ago
    Yes, obviously, but even then batteries are multiple times heavier. A fuel cell for this size is about 50kg currently, and a tank 50-80kg. The Mirai has a tank for 5kg hydrogen which weighs about 90kg: https://en.wikipedia.org/wiki/Toyota_Mirai https://en.wikipedia.org/wiki/Toyota_Mirai
    - SigmundA 5y ago
      Mirai: 1,850 kg Model 3 (Long-Range Dual-Motor): 1,847kg I am going to guess it's all the structure needed to protect the 10,000 psi hydrogen tanks.
      - bildung 5y ago
        Or you don't guess, follow the link instead and find out the Mirai is a) a bigger car and b) a hybrid, complete with electric motor and battery pack.
        SigmundA 5y ago
        The Mirai has a 1.6 kwh battery pack because the fuel cell cannot output the needed power for acceleration and to allow regenerative braking. It runs on the electric motor alone just like a Tesla. But yeah so add the buffer battery in your weight calculations needed for a fuel cell vehicle. Pretty minor difference in size, unclear how that translates into usable space: Mirai Length 4,890 mm Width 1,815 mm Height 1,535 mm Model 3 Length 4,694 mm Width 1,849 mm Height 1,443 mm Also note the Mirai has a single 113kw motor (even with buffer battery to help) while the long range single motor model 3 is 211kw and only weighs 1730kg, I actually posted the heaviest performance AWD model 3. The Tesla completely outperforms the Mirai in cost, weight, ease of charging and performance.

throwaway0a5e 5y ago

Most commercial trucks are lacking for weight, not for volume. They wouldn't use all those axles and tires if they didn't need to. Weight and charging time are the current major roadblocks to adopting batteries. Hydrogen theoretically solves those but introduces a lot of technical complexity along the way and needs a supply chain that currently doesn't exist.

SigmundA 5y ago
I don't see a lot of extra room on a truck for safe liquid hydrogen tanks 5 times the size of diesel tanks.
- darksaints 5y ago
  That would be true for cars, not so much for trucks. Most trucks hit their mass limits long before they hit their volume limits. Most box trucks, for example, are transporting more air by volume than cargo.
  - SigmundA 5y ago
    Trucks have length limits and more constrained in Europe which is why you still see many cab overs there. The US loosened length limits in the 70's allowing for long nose trucks which help with aero dynamics and safety.
    - darksaints 5y ago
      So you don't store it on the tractor itself, you store it with the trailer. That's how your god Elon is proposing to do it with batteries.
      - SigmundA 5y ago
        Yes with 10,000 psi hydrogen lines from trailer to tractor and expensive tanks on the trailer. AFAIK the Tesla semi has all batteries in the tractor. He is most certainly not my god.
        darksaints 5y ago
        The Tesla semi, without batteries on the trailer, is limited to about 500kWh of batteries...maybe 1000kWh if you have some extremely clever engineering. You can't really do much more than that without moving to a monocoque carbon frame to offset the weight, because the batteries are too dense. Commercial trucks have total weight limits, but they also have per-axle weight limits. If you are too heavy on a single axle, you're illegal. And while 500kWh batteries, are awesome and the perfect use case for local delivery, they won't cut it for OTR trucking. You need 700 mi of range at an absolute minimum for singles, ~2000mi for doubles. The weight of a 700 mile battery is a non-starter. Tesla's largest battery pack that they're even considering selling has a 500 mi range. There is a reason Tesla quotes kWh/mile, and not kWh/lb-mi (cargo, not GVW). They aren't competitive, and they likely never will be. And adding more batteries just makes the economics less competitive. There's a saying in the aircraft industry: it takes a lot of fuel to fly a lot of fuel. The same goes for batteries: it takes a lot of battery to move a lot of battery. Batteries, no matter what technical advances can be made, have limitations posed by the laws of physics, and none of them will ever have the energy density to make sense for long haul trucking. Which is why actual trucking companies that have actually beat His Lord and Savior Elon Musk to market with electric trucks (i.e. Volvo) are still looking to better alternatives in the long run.
        SigmundA 5y ago
        So now how much does a hydrogen fuel cell semi weigh whats its range? How much does it cost? Where do you fill it up? Current hydrogen fuel cell vehicles weight more than an equivalent battery powered car not not even looking at cost and power and refueling infrastructure. I agree that diesel is most viable for long haul and probably will be for some time and still has room to improve see Frieghtliners SuperTruck.
- maxerickson 5y ago
  Split trucks have lots of room. https://m.youtube.com/watch?v=4Bk7-L7ffiY https://m.youtube.com/watch?v=4Bk7-L7ffiY
  - SigmundA 5y ago
    Long wheelbase sleepers are very difficult to maneuver, they are pretty specialized and you won't see them in Europe do to length restrictions.
    - maxerickson 5y ago
      Sure, but it's an absurd example of space not being a particularly critical factor. That thing is a huge factor bigger than the volume of the fuel tanks.
      - SigmundA 5y ago
        Not sure why you say that, its very critical in Europe and still a concern in the US.
marcosdumay 5y ago
The problem with all those calculations is that storing hydrogen requires a lot of weight. If hydrogen were such a great idea, trucks would be already migrating to the in-between solution that is natural gas.
- thehappypm 5y ago
  Trucks maybe aren't, but city buses certainly are, all over the country. That's likely because of the infrastructure. You don't need to dot the entire country with LNG stops for your city buses, just a few fuel-up points here and there around town.
  - marcosdumay 5y ago
    Yes, buses and taxis are big adopters of it. Maybe there is something there and if we cut the cost of hydrogen enough (you know, all that extra solar power must go somewhere), it will be interesting for them too.
- albrewer 5y ago
  I second this insight. I'm a pressure vessel designer by trade. I got my numbers for all of this here[0] Liquefied hydrogen either needs to be stored cryogenically as a liquid, or at a very high pressure as a gas (65 MPa). I'm ignoring adsorption methods here. Given that we can't continuously maintain -253 °C all the time, this method is impractical for mobile usage. That leaves gaseous storage. To match the current range of diesel tractor-trailers, you'd need at least 4x the volume in hydrogen to come close to the standard of 600 miles between refills. I'm going to assume we need to store 1500 L of hydrogen to match the range. Other assumptions: The tank has a max overall length of roughly 2.5 meters. Inner and outer corrosion / gouge allowance of 6mm Design temperature of 200 °C (in case of fire). Material of construction is A-387 5 2 (5% Cr, 2% Mo steel) lined with something that prevents diffusion into and hydrogen embrittlement of the base metal. Vessel consists of a cylinder with spherical head on either end. Given: Inner diameter is 890mm, shell length is 1830mm, allowable stress is 178 MPa at the design temperature, we can use equation 4.3.1 from the ASME BPVC Section VIII Division 2 to determine the minimum thickness required for the given pressure. D is the corroded inner diameter of the vessel, P is the design pressure, S is the allowable stress, and E is the weld joint efficiency (assumed 1). D / 2 * (exp[P / (S * E)] - 1) + Corrosion 902 / 2 * (exp[65 / (178 * 1)] - 1) + 12 = 211mm wall thickness The weight of just the cylinder at that thickness with a length of 1.83m (without the spherical heads) is 11,000 kg. At that weight, batteries are pretty competitive. [0]: https://www.energy.gov/eere/fuelcells/hydrogen-storage-basics-0 https://www.energy.gov/eere/fuelcells/hydrogen-storage-basic...

darksaints 5y ago

SOHCs are approaching 100% conversion efficiency, and SOFCs have 60% baseline efficiency, and with practical heat conversion technologies, have closer to 75% efficiency. And they can use hydrocarbon fuels which can open up fuel options to synthetic fuels that have more reasonable mass/volume tradeoffs.

SigmundA 5y ago
Heat conversion is going to mean more equipment (heat recovery turbine?). SOHCS run at what 1000c? Don't see that being practical for vehicle use any time soon.
- darksaints 5y ago
  Heat recovery turbines are awesome. A single moving part, that's it. And those temperatures are not a problem at all. Standard off-the-shelf calcium silicate insulation will work fine.
  - SigmundA 5y ago
    Single moving part and generator and power control. None of that is free in terms of complexity, weight and cost. This is on top of whats needed for the fuel cell, plus you will probably need a buffer battery to fully utilize. Makes more sense to look at heat recovery turbines for a diesel engine which is exactly what Freightliner is doing with their Supertruck bringing its thermal efficiency up around 60%.
    - darksaints 5y ago
      It makes less sense on a diesel engine because their heat sources are lower temp. Fuel cells produce much more useful heat for a heat engine to capture. And no, the complexity of heat recovery isn't high at all. The costs pay themselves off almost immediately. They're orders of magnitude less complex than an ICE, last almost forever, and require almost no maintenance apart from cleaning after tens of thousands of hours. If a modern heat recovery turbine is too complex, then so is an electric motor.

bildung 5y ago

OTOH, using the model 3 as an example, you have to drive around 480kg of batteries all the time, while the same energy (75kWh/270MJ) in hydrogen would only amount to less than 2 kg.

SigmundA 5y ago
You won't get 75Wh to the wheel with 2kg and the hydrogen tanks and fuel cells have weight.
- bildung 5y ago
  Yes, obviously, but even then batteries are multiple times heavier. A fuel cell for this size is about 50kg currently, and a tank 50-80kg. The Mirai has a tank for 5kg hydrogen which weighs about 90kg: https://en.wikipedia.org/wiki/Toyota_Mirai https://en.wikipedia.org/wiki/Toyota_Mirai
  - SigmundA 5y ago
    Mirai: 1,850 kg Model 3 (Long-Range Dual-Motor): 1,847kg I am going to guess it's all the structure needed to protect the 10,000 psi hydrogen tanks.
    - bildung 5y ago
      Or you don't guess, follow the link instead and find out the Mirai is a) a bigger car and b) a hybrid, complete with electric motor and battery pack.
      - SigmundA 5y ago
        The Mirai has a 1.6 kwh battery pack because the fuel cell cannot output the needed power for acceleration and to allow regenerative braking. It runs on the electric motor alone just like a Tesla. But yeah so add the buffer battery in your weight calculations needed for a fuel cell vehicle. Pretty minor difference in size, unclear how that translates into usable space: Mirai Length 4,890 mm Width 1,815 mm Height 1,535 mm Model 3 Length 4,694 mm Width 1,849 mm Height 1,443 mm Also note the Mirai has a single 113kw motor (even with buffer battery to help) while the long range single motor model 3 is 211kw and only weighs 1730kg, I actually posted the heaviest performance AWD model 3. The Tesla completely outperforms the Mirai in cost, weight, ease of charging and performance.