5 ms·

> that puts the hydrogen at roughly 15kWh of useful energy. That's not the hydrogen's fundamental fault as a medium. It's the fault of the conversion process.

> that puts the hydrogen at roughly 15kWh of useful energy. That's not the hydrogen's fundamental fault as a medium. It's the fault of the conversion process. 33 kWh of thermal to 15 kWh of work, according to your calculation. That's in the realm of highly efficient (Diesel) internal combustion engines. As for 4 miles per kWh for a Tesla, you're already comparing apples to oranges. The Tesla feeds off batteries, where the expensive conversion part is already past. You're comparing high-exergy (battery) to low-exergy (raw hydrogen). I don't know anything about fuel cells, but imagine they reach 90% efficiency (is that even theoretically possible? Don't know); suddenly you get 30 kWh of work out of 1kg of hydrogen. We're just starting out, and a hundred years ago ICE efficiencies were atrocious, too.

ben_w 5y ago
> We're just starting out, and a hundred years ago ICE efficiencies were atrocious, too. Are we just starting out with fuel cells? They were on the Apollo missions and the Space Shuttle, and Wikipedia says they were invented in 1838 and commercialised in 1932.
- diarrhea 5y ago
  Large scale, yes, I'd say so.
- coderenegade 5y ago
  We are. There's a world of difference between the alkaline fuel cells that were used by NASA, and the solid oxide cells we have today.
  - ben_w 5y ago
    That sounds like a confirmation of my point, not a rebuttal — it being more advanced now is also evidence we’re not just starting out.
    - coderenegade 5y ago
      It depends on what your intent is; if it's that the technology has been around for a long time, that's not really adding much to the conversation. It would be like saying that battery technology is centuries old, which is technically true, but meaningless in the context of advances being made in li-ion batteries today. If the intent is to say that fuel cell technology is mature and unlikely to significantly advance further -- which is how it's often presented on this topic in particular -- that just isn't true. SOFCs have only recently reached commercialization, and there are still gains to be had in, for example, manufacturing PCFCs, rSOCs, reducing platinum content of low-temperature (PEM) devices, etc. We're starting in the context of scaling up an industry, and all of the gains that brings.
Robotbeat 5y ago
You can’t ignore one of the main relative advantages of batteries (very high round trip efficiency) in this discussion and arbitrarily use the heating value of hydrogen without taking the relatively low efficiency into account. Skews the discussion. And hydrogen is produced via electricity, so I’m not skewing the discussion at all. Round trip efficiency of battery is 90-95% (can be higher). Round trip for hydrogen (ie electrolysis & then storage and then fuel cell conversion back to electricity), including cooling (required for fast refueling) and compression, is about 25-40%. Even when that hydrogen is already in your tank, you only get about 60% of the energy out of it in useful energy. Heck, in California, hydrogen stations typically are only 33% renewable with most of it being gray hydrogen (9.3kg of CO2 per kg of gray hydrogen, not counting liquefaction), which makes hydrogen cars even at $10-14/kg, worse for the environment than even just random electric cars (although many EVs use primarily nuclear or renewables). And while electric cars can have distribution losses, they’re pretty low, ie single-digit percent. But hydrogen stations are almost always refueled by truck, which has its own inefficiencies, and the stations also must constantly maintain the hydrogen at cryogenic temperatures to be ready to fuel. Also, some new stations get fuel delivered as liquid hydrogen, which is denser than compressed and therefore easier to transport, but liquefying 1kg of hydrogen (and converting it to para-hydrogen, which is normal) requires about 10-13kWh of electricity… which could send a Model 3 about 40-50 miles. So you almost can get further on an electric car on just the energy needed to distribute the kilogram of hydrogen as the hydrogen car can get by consuming that kilogram! It’s pretty bad. Hydrogen for transport just doesn’t make much sense except for niche use cases. Maybe the last 10% of air transport that proves electrification-resistant or certain long distance ships or rockets.

ben_w 5y ago

> We're just starting out, and a hundred years ago ICE efficiencies were atrocious, too. Are we just starting out with fuel cells? They were on the Apollo missions and the Space Shuttle, and Wikipedia says they were invented in 1838 and commercialised in 1932.

diarrhea 5y ago
Large scale, yes, I'd say so.
coderenegade 5y ago
We are. There's a world of difference between the alkaline fuel cells that were used by NASA, and the solid oxide cells we have today.
- ben_w 5y ago
  That sounds like a confirmation of my point, not a rebuttal — it being more advanced now is also evidence we’re not just starting out.
  - coderenegade 5y ago
    It depends on what your intent is; if it's that the technology has been around for a long time, that's not really adding much to the conversation. It would be like saying that battery technology is centuries old, which is technically true, but meaningless in the context of advances being made in li-ion batteries today. If the intent is to say that fuel cell technology is mature and unlikely to significantly advance further -- which is how it's often presented on this topic in particular -- that just isn't true. SOFCs have only recently reached commercialization, and there are still gains to be had in, for example, manufacturing PCFCs, rSOCs, reducing platinum content of low-temperature (PEM) devices, etc. We're starting in the context of scaling up an industry, and all of the gains that brings.

Robotbeat 5y ago

You can’t ignore one of the main relative advantages of batteries (very high round trip efficiency) in this discussion and arbitrarily use the heating value of hydrogen without taking the relatively low efficiency into account. Skews the discussion. And hydrogen is produced via electricity, so I’m not skewing the discussion at all. Round trip efficiency of battery is 90-95% (can be higher). Round trip for hydrogen (ie electrolysis & then storage and then fuel cell conversion back to electricity), including cooling (required for fast refueling) and compression, is about 25-40%. Even when that hydrogen is already in your tank, you only get about 60% of the energy out of it in useful energy. Heck, in California, hydrogen stations typically are only 33% renewable with most of it being gray hydrogen (9.3kg of CO2 per kg of gray hydrogen, not counting liquefaction), which makes hydrogen cars even at $10-14/kg, worse for the environment than even just random electric cars (although many EVs use primarily nuclear or renewables). And while electric cars can have distribution losses, they’re pretty low, ie single-digit percent. But hydrogen stations are almost always refueled by truck, which has its own inefficiencies, and the stations also must constantly maintain the hydrogen at cryogenic temperatures to be ready to fuel. Also, some new stations get fuel delivered as liquid hydrogen, which is denser than compressed and therefore easier to transport, but liquefying 1kg of hydrogen (and converting it to para-hydrogen, which is normal) requires about 10-13kWh of electricity… which could send a Model 3 about 40-50 miles. So you almost can get further on an electric car on just the energy needed to distribute the kilogram of hydrogen as the hydrogen car can get by consuming that kilogram! It’s pretty bad. Hydrogen for transport just doesn’t make much sense except for niche use cases. Maybe the last 10% of air transport that proves electrification-resistant or certain long distance ships or rockets.