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> the most cost-efficient method (of making hydrogen) has been using natural gas to reclaim the hydrogen. So this wasn’t clean energy to begin with, but now th

> the most cost-efficient method (of making hydrogen) has been using natural gas to reclaim the hydrogen. So this wasn’t clean energy to begin with, but now they’re improving: > solar energy and wind power and wind-generated energy, to make hydrogen using electrolysis And this sounds definitely less efficient than using electricity directly. Maybe hydrogen cells will have the density advantage, but at what cost to overall efficiency?

barrkel 7y ago
Efficiency only has meaning when applied to a metric. Hydrogen is more efficient for speed of refuel and for energy density, important for things like flying and other long distance work.
- deleted 7y ago
  [deleted]
chaboud 7y ago
If it's a completely closed-loop process, efficiency doesn't matter nearly as much as scalability. Let's say the solar cells are 20% efficient, and electrolysis is 50% efficient... So 10% of the solar energy makes it into the tank, and some subset of that makes it through the fuel cell... But we started with water and photons and end up with evaporated water and heat. That's where we were going to be, anyway... If it scales, we're okay. If that electricity is generated from some non-renewable resource, efficiency is of huge importance. If it's something like wind or solar, it can take a back seat.
darksaints 7y ago
If electricity costs $.15/kWh, efficiency might matter. If it costs $.03/kWh, there are way more factors that might matter a lot more.
tomp 7y ago
> And this sounds definitely less efficient than using electricity directly. Not necessarily. (1) There are losses transporting in storing electricity. If hydrogen was made on the spot, and if the losses storing and transporting hydrogen were smaller (unlikely), that would be a gain. (2) Hydrogen can be produced at solar peaks, when energy prices turn negative, and stored... huge (net) efficiency gain!
- _ph_ 7y ago
  Why not charge 2-3x as many cars during the solar peaks? Hydrogen might be in the far future for long-term storage of electricity, but then it will get used to power the grid in times of lacking sun/wind, rather then propelling cars.
Eric_WVGG 7y ago
Seems like they could have some huge advantages for air travel. Part of the calculations in flight is that your vessel weighs less as the journey progresses, and for maximum efficiency you really only want to carry as much fuel as you need to get from point A to point B. A plane powered by batteries would never stop being heavy. Given the eye popping carbon costs of routine flights, clean hydrogen is worth pursuing for aircraft alone.
hutzlibu 7y ago
"> solar energy and wind power and wind-generated energy, to make hydrogen using electrolysis And this sounds definitely less efficient than using electricity directly" Of course not. But since you do not want to drive with a cable on your car you allways have to transform the energy. And the overall efficiency with fuel cells is much lower, but it has other advantages. Like the potential unlimited storage element water (plus iron for the tank walls), compared to limited avaiable batterie ressources.

barrkel 7y ago

Efficiency only has meaning when applied to a metric. Hydrogen is more efficient for speed of refuel and for energy density, important for things like flying and other long distance work.

deleted 7y ago
[deleted]

chaboud 7y ago

If it's a completely closed-loop process, efficiency doesn't matter nearly as much as scalability. Let's say the solar cells are 20% efficient, and electrolysis is 50% efficient... So 10% of the solar energy makes it into the tank, and some subset of that makes it through the fuel cell... But we started with water and photons and end up with evaporated water and heat. That's where we were going to be, anyway... If it scales, we're okay. If that electricity is generated from some non-renewable resource, efficiency is of huge importance. If it's something like wind or solar, it can take a back seat.

darksaints 7y ago

If electricity costs $.15/kWh, efficiency might matter. If it costs $.03/kWh, there are way more factors that might matter a lot more.

tomp 7y ago

> And this sounds definitely less efficient than using electricity directly. Not necessarily. (1) There are losses transporting in storing electricity. If hydrogen was made on the spot, and if the losses storing and transporting hydrogen were smaller (unlikely), that would be a gain. (2) Hydrogen can be produced at solar peaks, when energy prices turn negative, and stored... huge (net) efficiency gain!

_ph_ 7y ago
Why not charge 2-3x as many cars during the solar peaks? Hydrogen might be in the far future for long-term storage of electricity, but then it will get used to power the grid in times of lacking sun/wind, rather then propelling cars.

Eric_WVGG 7y ago

Seems like they could have some huge advantages for air travel. Part of the calculations in flight is that your vessel weighs less as the journey progresses, and for maximum efficiency you really only want to carry as much fuel as you need to get from point A to point B. A plane powered by batteries would never stop being heavy. Given the eye popping carbon costs of routine flights, clean hydrogen is worth pursuing for aircraft alone.

hutzlibu 7y ago

"> solar energy and wind power and wind-generated energy, to make hydrogen using electrolysis And this sounds definitely less efficient than using electricity directly" Of course not. But since you do not want to drive with a cable on your car you allways have to transform the energy. And the overall efficiency with fuel cells is much lower, but it has other advantages. Like the potential unlimited storage element water (plus iron for the tank walls), compared to limited avaiable batterie ressources.