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Doing this would defeat the only advantage hydrogen has, which is rapid fueling. To add to the inconvenience, you'll need to plug in both the electricity, and

by danans 7y ago

Doing this would defeat the only advantage hydrogen has, which is rapid fueling. To add to the inconvenience, you'll need to plug in both the electricity, and a hose to your supply of distilled water. Beyond that, the best case efficiency for such a hydrogen production process in an industrial setting is 80% (using a process which feeds waste heat back into the electrolysis reaction). From the hydrogen back to energy moving the wheels is at most 50% efficient, so a total plug to wheels efficiency of less than 40%. In the real world, it will be far less efficient than that (probably 25% at best), and very expensive to achieve in a practical car for sale, for the same reason that hydrogen fuel cells in cars are expensive today. That vs the typical plug to wheels efficiency of around 60% in today's electric vehicles. And such regenerative hydrogen fuel cells do not even exist for automotive applications today. This paper has several lifecycle efficiency graphs that explain aspects of this in some detail: https://www.mdpi.com/2032-6653/9/1/3 https://www.mdpi.com/2032-6653/9/1/3

Hypx 7y ago
https://www.sciencedirect.com/science/article/abs/pii/S036031991000340X https://www.sciencedirect.com/science/article/abs/pii/S03603... The best case scenario like you described is about 98%. FYI, 80% is already being hit by real world normal electrolysis reactions. It’s very likely we’re in the same position with fuel cell cars that solar was back in the late-2000s. Arguments that it is “too expensive” are really falling apart, especially considering that green hydrogen is around $2-3/kg today, and that platinum loading has dropped to around 10 grams for a car sized fuel cell.
- danans 7y ago
  > FYI, 80% is already being hit by real world normal electrolysis reactions. Not in a fuel-cell running in reverse in a car, though, which is what the GP was referring to. > especially considering that green hydrogen is around $2-3/kg today More like $3-7 per kg today [1]. And as that article (which is less than 1 month old) points out, producing green hydrogen would require an absolutely massive buildout of renewables, which would better be put to direct use without the conversion penalty to hydrogen. Hydrogen energy storage will still have its niche applications on the margins, but it is unlikely to catch up to the cost and availability advantages of batteries for cars in places where the existing electric grid reaches. 1. https://www.rechargenews.com/transition/a-wake-up-call-on-green-hydrogen-the-amount-of-wind-and-solar-needed-is-immense/2-1-776481 https://www.rechargenews.com/transition/a-wake-up-call-on-gr...
  - Hypx 7y ago
    > Not in a fuel-cell running in reverse in a car, though, which is what the GP was referring to. It would make more sense to have a separate electrolyzer. This way, you can have a tank of hydrogen sitting around that can refuel your car in minutes, not hours. The original scenario is actually a bad idea. > More like $3-7 per kg today [1] You're rounding up to $3-7. It specifically refers to $2.50-6.80. Those higher figures aren't really going to stand for long as cheap green hydrogen displaces expensive green hydrogen. > producing green hydrogen would require an absolutely massive buildout of renewables, But we are massively building out renewables. In fact, we're building too much. During peak production times, renewable energy is literally just grounded since there is no use for it all. > Hydrogen energy storage will still have its niche applications on the margins, Hydrogen can be stored in salt domes in extraordinary quantities.[1] A single cavern can store 150,000 MWh of energy, and one formation in Utah can contain 100 caverns. That's something like 200 million BEVs worth of energy storage! As a niche, it's dominant one, and frankly hydrogen is easily going to be bigger in absolute metrics on that fact alone. > but it is unlikely to catch up to the cost and availability advantages of batteries for cars in places where the existing electric grid reaches. This is not a race. Fuel cell technology will still advance regardless of what happens of battery powered cars. Furthermore, nothing is close to the internal combustion engine in terms of marketshare. If it were a race, ICEVs are way ahead and neither BEVs nor FCEVs are anywhere close to winning. 1. https://www.forbes.com/sites/mitsubishiheavyindustries/2020/03/13/in-utah-hydrogen-and-a-massive-salt-dome-are-winning-the-west-for-renewable-energy/#8bcb09e5c52f https://www.forbes.com/sites/mitsubishiheavyindustries/2020/...
    - danans 7y ago
      > It would make more sense to have a separate electrolyzer. A separate electrolyser and hydrogen storage at the household level just to fill up your car? It's doubtful that will make financial sense anytime in the near future, vs a plug. > It specifically refers to $2.50-6.80. You quoted $2-3 - in whole dollars - which are undoubtedly rounded figured themselves. How else would express $2.50-6.80 in whole dollars than $3-7? > But we are massively building out renewables. Not nearly enough to power ground transportation on green hydrogen, which was the point of the article I linked. On top of that, the tank-to-wheels efficiency of hydrogen fuel cell vehicles is 1/2 that of BEVs, which implies double the renewable electricity needed for green hydrogen vs directly using electricity in BEVs. It's better to keep ground transport as efficient as possible by using BEVs, and use the remaining electricity to synthesize fuels for applications like aviation that don't lend themselves to batteries due to weight constraints. > A single cavern can store 150,000 MWh of energy, and one formation in Utah can contain 100 caverns. There's a lot of "can" in that, similar to initiatives pushing carbon-capture from coal plants. I applaud it if it eventually works, but that article is a paid marketing release (note the "Mitsubishi Heavy Industries BRANDVOICE| Paid Program" at the top). > This is not a race. Fuel cell technology will still advance regardless of what happens of battery powered cars It is a race to which tech has a market viable product for cleanly fueled road transportation. Battery tech isn't sitting still either, especially on the rapid charging and range front. It's totally possible that hydrogen tech will come through with a series of breakthroughs that mitigate its current issues with cost, lack of distribution infra, but projections like the one in the article I shared put that out 10-20 years, and predicting anything past 10 years is a crapshoot anyways. > If it were a race, ICEVs are way ahead and neither BEVs nor FCEVs are anywhere close to winning. It's a race for the transportation tech of the future. Obviously ICEs are the majority of vehicles now, but that's hardly interesting to the debate about FCEVs vs BEVs, except in the matter of how much the gap between either of the new technologies and ICEs closes on the consumer price level.
mrpopo 7y ago
> so a total plug to wheels efficiency of less than 40%. In the real world, it will be far less efficient than that (probably 25% at best). > That vs the typical plug to wheels efficiency of around 60% in today's electric vehicles. 1) Just to add a point of comparison, current ICE engines have an efficiency of around 25-35%, so while 25% sounds bad, that's the technology we've been putting up with for a century. But obviously, new technologies ought to be more efficient. 2) Speaking of efficiency, here we are talking about plug-to-wheel efficiencies. The true useful efficiency of a car is the ability to move you to your destination. So adding in the "weight efficiency" of 5-10%, given a 1-2t car and a 100kg charge (based on average 1.5 people occupancy in a car), the efficiency drops to ~1% for ICE/hydrogen cars and ~3% for electric cars. Please consider using lighter cars, a lot more gains can be achieved that way.

by danans 7y ago

Hypx 7y ago

https://www.sciencedirect.com/science/article/abs/pii/S036031991000340X https://www.sciencedirect.com/science/article/abs/pii/S03603... The best case scenario like you described is about 98%. FYI, 80% is already being hit by real world normal electrolysis reactions. It’s very likely we’re in the same position with fuel cell cars that solar was back in the late-2000s. Arguments that it is “too expensive” are really falling apart, especially considering that green hydrogen is around $2-3/kg today, and that platinum loading has dropped to around 10 grams for a car sized fuel cell.

danans 7y ago
> FYI, 80% is already being hit by real world normal electrolysis reactions. Not in a fuel-cell running in reverse in a car, though, which is what the GP was referring to. > especially considering that green hydrogen is around $2-3/kg today More like $3-7 per kg today [1]. And as that article (which is less than 1 month old) points out, producing green hydrogen would require an absolutely massive buildout of renewables, which would better be put to direct use without the conversion penalty to hydrogen. Hydrogen energy storage will still have its niche applications on the margins, but it is unlikely to catch up to the cost and availability advantages of batteries for cars in places where the existing electric grid reaches. 1. https://www.rechargenews.com/transition/a-wake-up-call-on-green-hydrogen-the-amount-of-wind-and-solar-needed-is-immense/2-1-776481 https://www.rechargenews.com/transition/a-wake-up-call-on-gr...
- Hypx 7y ago
  > Not in a fuel-cell running in reverse in a car, though, which is what the GP was referring to. It would make more sense to have a separate electrolyzer. This way, you can have a tank of hydrogen sitting around that can refuel your car in minutes, not hours. The original scenario is actually a bad idea. > More like $3-7 per kg today [1] You're rounding up to $3-7. It specifically refers to $2.50-6.80. Those higher figures aren't really going to stand for long as cheap green hydrogen displaces expensive green hydrogen. > producing green hydrogen would require an absolutely massive buildout of renewables, But we are massively building out renewables. In fact, we're building too much. During peak production times, renewable energy is literally just grounded since there is no use for it all. > Hydrogen energy storage will still have its niche applications on the margins, Hydrogen can be stored in salt domes in extraordinary quantities.[1] A single cavern can store 150,000 MWh of energy, and one formation in Utah can contain 100 caverns. That's something like 200 million BEVs worth of energy storage! As a niche, it's dominant one, and frankly hydrogen is easily going to be bigger in absolute metrics on that fact alone. > but it is unlikely to catch up to the cost and availability advantages of batteries for cars in places where the existing electric grid reaches. This is not a race. Fuel cell technology will still advance regardless of what happens of battery powered cars. Furthermore, nothing is close to the internal combustion engine in terms of marketshare. If it were a race, ICEVs are way ahead and neither BEVs nor FCEVs are anywhere close to winning. 1. https://www.forbes.com/sites/mitsubishiheavyindustries/2020/03/13/in-utah-hydrogen-and-a-massive-salt-dome-are-winning-the-west-for-renewable-energy/#8bcb09e5c52f https://www.forbes.com/sites/mitsubishiheavyindustries/2020/...
  - danans 7y ago
    > It would make more sense to have a separate electrolyzer. A separate electrolyser and hydrogen storage at the household level just to fill up your car? It's doubtful that will make financial sense anytime in the near future, vs a plug. > It specifically refers to $2.50-6.80. You quoted $2-3 - in whole dollars - which are undoubtedly rounded figured themselves. How else would express $2.50-6.80 in whole dollars than $3-7? > But we are massively building out renewables. Not nearly enough to power ground transportation on green hydrogen, which was the point of the article I linked. On top of that, the tank-to-wheels efficiency of hydrogen fuel cell vehicles is 1/2 that of BEVs, which implies double the renewable electricity needed for green hydrogen vs directly using electricity in BEVs. It's better to keep ground transport as efficient as possible by using BEVs, and use the remaining electricity to synthesize fuels for applications like aviation that don't lend themselves to batteries due to weight constraints. > A single cavern can store 150,000 MWh of energy, and one formation in Utah can contain 100 caverns. There's a lot of "can" in that, similar to initiatives pushing carbon-capture from coal plants. I applaud it if it eventually works, but that article is a paid marketing release (note the "Mitsubishi Heavy Industries BRANDVOICE| Paid Program" at the top). > This is not a race. Fuel cell technology will still advance regardless of what happens of battery powered cars It is a race to which tech has a market viable product for cleanly fueled road transportation. Battery tech isn't sitting still either, especially on the rapid charging and range front. It's totally possible that hydrogen tech will come through with a series of breakthroughs that mitigate its current issues with cost, lack of distribution infra, but projections like the one in the article I shared put that out 10-20 years, and predicting anything past 10 years is a crapshoot anyways. > If it were a race, ICEVs are way ahead and neither BEVs nor FCEVs are anywhere close to winning. It's a race for the transportation tech of the future. Obviously ICEs are the majority of vehicles now, but that's hardly interesting to the debate about FCEVs vs BEVs, except in the matter of how much the gap between either of the new technologies and ICEs closes on the consumer price level.

mrpopo 7y ago

> so a total plug to wheels efficiency of less than 40%. In the real world, it will be far less efficient than that (probably 25% at best). > That vs the typical plug to wheels efficiency of around 60% in today's electric vehicles. 1) Just to add a point of comparison, current ICE engines have an efficiency of around 25-35%, so while 25% sounds bad, that's the technology we've been putting up with for a century. But obviously, new technologies ought to be more efficient. 2) Speaking of efficiency, here we are talking about plug-to-wheel efficiencies. The true useful efficiency of a car is the ability to move you to your destination. So adding in the "weight efficiency" of 5-10%, given a 1-2t car and a 100kg charge (based on average 1.5 people occupancy in a car), the efficiency drops to ~1% for ICE/hydrogen cars and ~3% for electric cars. Please consider using lighter cars, a lot more gains can be achieved that way.