5 ms·

Not necessarily. High pressure electrolysis tends to be very efficient, and gets you over the hump of getting to 200 bar with only around 3% energy loss. Compre

Not necessarily. High pressure electrolysis tends to be very efficient, and gets you over the hump of getting to 200 bar with only around 3% energy loss. Compression energy is logarithmic, so getting to 700 bar from that point takes less than half the energy that we would have spent getting it 200 bar. Figures I've seen have it at around 6-8% energy lost to get to 600-700 bar (the last part is done on gas, which is less efficient). That said, if we really wanted to, we could do deepwater electrolysis and let the Earth do the compression for us. You wouldn't even need oceanic electricity generation, because there's enough of a pressure differential between the surface and, say, 2km depth, that you could comfortably siphon some of the pressure in a turbine to power the reaction. The limitations at this point are mostly engineering and manufacturing -- we know how to do electrolysis at those pressures, and we can even do salt water electrolysis.

throwawaylinux 5y ago
How could you comfortably siphon some of the pressure in a turbine to power the reaction? What does that mean?
- coderenegade 5y ago
  If you have a pressure differential, a fluid will jet from high pressure to low pressure, where the difference is converted to the velocity of the fluid. If you have a moving fluid, you can use it to drive a turbine and generate power, which in turn reduces the fluid's velocity. Since there's a huge difference in pressure between the ocean 2km down, and the surface, you could build a pipe and a reservoir that lets you "push" the byproducts of electrolysis to the surface. Say your surface reservoir is 150 bar, and the original is 200 bar -- that gives you 50 bar of pressure to get the hydrogen to the surface, and drive a turbine to generate power for electrolysis.
  - throwawaylinux 5y ago
    You can't get your fluid to the surface though with that pressure differential. And as your pipe fills up, it reduces the pressure differential, and pumping it out would cost more than the electricity you could get from the turbine.
- sandworm101 5y ago
  Make gas at bottom of ocean, under pressure. Bring it up to the surface (low pressure) and run it through a turbine. Plug that turbine into the machine making gas at bottom of ocean. Not exactly free energy but very efficient. Harvesting the weight of the ocean to help generate hydrogen gas.
  - throwawaylinux 5y ago
    > Make gas at bottom of ocean, under pressure. Bring it up to the surface (low pressure) and run it through a turbine. That isn't what OP meant (see his reply), but if the reason you create the hydrogen at high pressure is to reduce the cost of pressurizing it more, you would not want to reduce its pressure. But let's say you do want to -- the energy stored in the pressure, would extracting that be worth the additional energy cost of creating hydrogen at the bottom of the ocean and bringing it to the surface? > Plug that turbine into the machine making gas at bottom of ocean. Not exactly free energy but very efficient. Harvesting the weight of the ocean to help generate hydrogen gas.

throwawaylinux 5y ago

How could you comfortably siphon some of the pressure in a turbine to power the reaction? What does that mean?

coderenegade 5y ago
If you have a pressure differential, a fluid will jet from high pressure to low pressure, where the difference is converted to the velocity of the fluid. If you have a moving fluid, you can use it to drive a turbine and generate power, which in turn reduces the fluid's velocity. Since there's a huge difference in pressure between the ocean 2km down, and the surface, you could build a pipe and a reservoir that lets you "push" the byproducts of electrolysis to the surface. Say your surface reservoir is 150 bar, and the original is 200 bar -- that gives you 50 bar of pressure to get the hydrogen to the surface, and drive a turbine to generate power for electrolysis.
- throwawaylinux 5y ago
  You can't get your fluid to the surface though with that pressure differential. And as your pipe fills up, it reduces the pressure differential, and pumping it out would cost more than the electricity you could get from the turbine.
sandworm101 5y ago
Make gas at bottom of ocean, under pressure. Bring it up to the surface (low pressure) and run it through a turbine. Plug that turbine into the machine making gas at bottom of ocean. Not exactly free energy but very efficient. Harvesting the weight of the ocean to help generate hydrogen gas.
- throwawaylinux 5y ago
  > Make gas at bottom of ocean, under pressure. Bring it up to the surface (low pressure) and run it through a turbine. That isn't what OP meant (see his reply), but if the reason you create the hydrogen at high pressure is to reduce the cost of pressurizing it more, you would not want to reduce its pressure. But let's say you do want to -- the energy stored in the pressure, would extracting that be worth the additional energy cost of creating hydrogen at the bottom of the ocean and bringing it to the surface? > Plug that turbine into the machine making gas at bottom of ocean. Not exactly free energy but very efficient. Harvesting the weight of the ocean to help generate hydrogen gas.