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Have we solved the hydrogen storage issue yet? This seems like pumped hydro storage except the dam has a not-so-slow leak. People keep the o2 as well right? E

Have we solved the hydrogen storage issue yet? This seems like pumped hydro storage except the dam has a not-so-slow leak. People keep the o2 as well right? Even in fuel cell mode you could use air as the oxidizer and keep the purified o2.

pfdietz 4y ago
Hydrogen can be stored in underground reservoirs, like solution mined cavities in salt domes and spent natural gas fields. The cost is as little as $1 per kWh of storage capacity. This is the great advantage of hydrogen over many other storage schemes, which have a much higher cost per unit of energy storage capacity. There is also the per-power cost of charging and discharging equipment, but that's independent of per-energy capacity cost. I don't believe the oxygen is kept. Even if it were, O2 is very cheap. Liquid oxygen is the second cheapest industrial liquid, after water. Maybe it would make sense to store O2 underground as compressed gas also, for use in Allam cycle turbines (which would prevent NOx formation and even recover the water of combustion for reuse.) In fuel cell mode you're consuming oxygen, not purifying it.
- galangalalgol 4y ago
  What is the source on the price of liquid o2? That seems insane that it would be so cheap, don't you have to either chill the air until it condenses, or use a selective absorber to separate it from air? My point was why waste purified o2 on the fuel cell when you could use air and then sell the o2?
  - pfdietz 4y ago
    Yes, you chill the air. You get to recover the "cold" from the nitrogen (by using the cold separated nitrogen to chill the incoming air via countercurrent heat exchange), so you're actually only chilling (without recovery) the oxygen. Cryogenic air separation is done on a vast scale to get gaseous oxygen for the basic oxygen steelmaking process. LOX can be obtained by tapping off some of that rather than also using to chill the incoming air.
- daveguy 4y ago
  Liquid oxygen is definitely not the cheapest industrial liquid after water. Just the temperature required to maintain liquid oxygen makes this false on its face. Even oxygen gas isn't the cheapest gas.
  - pfdietz 4y ago
    NASA in 2001 paid $0.67/gallon for liquid oxygen. What industrial liquid aside from water (or things dissolved in water) is that cheap?
    - tuatoru 4y ago
      Just recently methanol was $378/ton in small amounts. In 2019 it was between $200/ton and $300/ton. I'm too lazy to do the price deflation--and I wouldn't know what deflator to use--but that seems like it would have been at least comparable. Fuel oil may have been similar. Sulfuric acid $170/ton in 2022.
      - Robotbeat 4y ago
        Liquid oxygen is about $100/tonne in large quantities, and the price can be even lower if you pay for large scale, on-site generation.
        londons_explore 4y ago
        Liquid oxygen pricing is mostly the electricity pricing... Equipment cost is small in comparison. Which means it varies widely depending on where in the world you're wanting it. It isn't valuable enough to ship far.
        Robotbeat 4y ago
        It takes about 200kWh per tonne of oxygen separated. If it’s mostly electricity price (therefore total price is at most twice the electricity price), and your industrial electricity is 7¢/kWh (common in the US), then you’re saying the total price of liquid oxygen is no more than about $30/tonne, even lower than my $100/tonne.
nanomonkey 4y ago
Our existing natural gas pipelines can handle storing up to 10% added hydrogen gas. If we were to start ramping up biogas production from waste streams we could produce some, if not all of the methane that goes along hydrogen in natural gas. This would utilize existing infrastructure, and help with energy production at night (think heating) when solar is unavailable. Hydrogen is only difficult to store if it is pressurized, at low pressures there are low losses due to adiabatic expansion. Embrittlement is only a concern when you're holding back high pressures, and isn't a big concern for pipelines which can conceivably hold a large amount of reserve fuel. I think the purified oxygen is an overlooked resource, as it can be used at, or near, the electrolizer as a method of producing pure syngas from waste organic matter using gasification. Normally woodgas or producer gas isn't desirable because it is made from atmospheric air as the oxidizer which contains a large amount of inert nitrogen which takes up space and produces nitric oxides at high temperatures. By using pure oxygen one can produce higher temperatures in the gasification reactor, and a purer syngas. This could be stored, and then used along with the hydrogen to produce heat and electricity in existing natural gas turbines when it is needed.
- pfdietz 4y ago
  The use I would think of for the oxygen would be burning fuels in Allam cycle turbines. These use supercritical CO2 and burn fuels with oxygen in the CO2 (oxygen is needed so nitrogen doesn't build up in the CO2). The products of combustion are water and CO2. Water condenses and can be reused (an Allam cycle turbine burning natural gas would be a net producer of liquid water); CO2 from burning natural gas would be tapped off in pure form at zero marginal cost (unlike other CO2 capture methods.) Allam cycle turbines burning hydrogen would not make CO2, of course, but they'd avoid the need for NOx reduction stage after the turbine. One could also imagine a system where CO2 is captured and stored, then used to make methane from hydrogen, that is also then stored. You'd need three kinds of storage reservoirs (methane, CO2, and oxygen) but perhaps this could be easier than storing hydrogen.
  - nanomonkey 4y ago
    I'm curious if this could be utilized with less pure fuels such as organic wastes rich with oils and waxes. Supercritical CO2 is often used to remove oils and waxes from organic matter and clothing. The high temperatures and pressures might even be sufficient for pyrolysis of the organic matter, allowing for further removal of combustable materials. Of course organic materials are highly variable and full of other volatiles that may harm the turbines (i.e. sulfur, fatty acids, etc.). Sadly the purity of the exhaust gases would likely be effected as Nitrogen from proteins, along with other elements are going to end up in the exhaust stream. These could all be distilled out, or scrubbed, but with higher energy costs. Still there are lots of exciting developments that can be made to cogeneration power production using organic waste streams.

pfdietz 4y ago

Hydrogen can be stored in underground reservoirs, like solution mined cavities in salt domes and spent natural gas fields. The cost is as little as $1 per kWh of storage capacity. This is the great advantage of hydrogen over many other storage schemes, which have a much higher cost per unit of energy storage capacity. There is also the per-power cost of charging and discharging equipment, but that's independent of per-energy capacity cost. I don't believe the oxygen is kept. Even if it were, O2 is very cheap. Liquid oxygen is the second cheapest industrial liquid, after water. Maybe it would make sense to store O2 underground as compressed gas also, for use in Allam cycle turbines (which would prevent NOx formation and even recover the water of combustion for reuse.) In fuel cell mode you're consuming oxygen, not purifying it.

galangalalgol 4y ago
What is the source on the price of liquid o2? That seems insane that it would be so cheap, don't you have to either chill the air until it condenses, or use a selective absorber to separate it from air? My point was why waste purified o2 on the fuel cell when you could use air and then sell the o2?
- pfdietz 4y ago
  Yes, you chill the air. You get to recover the "cold" from the nitrogen (by using the cold separated nitrogen to chill the incoming air via countercurrent heat exchange), so you're actually only chilling (without recovery) the oxygen. Cryogenic air separation is done on a vast scale to get gaseous oxygen for the basic oxygen steelmaking process. LOX can be obtained by tapping off some of that rather than also using to chill the incoming air.
daveguy 4y ago
Liquid oxygen is definitely not the cheapest industrial liquid after water. Just the temperature required to maintain liquid oxygen makes this false on its face. Even oxygen gas isn't the cheapest gas.
- pfdietz 4y ago
  NASA in 2001 paid $0.67/gallon for liquid oxygen. What industrial liquid aside from water (or things dissolved in water) is that cheap?
  - tuatoru 4y ago
    Just recently methanol was $378/ton in small amounts. In 2019 it was between $200/ton and $300/ton. I'm too lazy to do the price deflation--and I wouldn't know what deflator to use--but that seems like it would have been at least comparable. Fuel oil may have been similar. Sulfuric acid $170/ton in 2022.
    - Robotbeat 4y ago
      Liquid oxygen is about $100/tonne in large quantities, and the price can be even lower if you pay for large scale, on-site generation.
      - londons_explore 4y ago
        Liquid oxygen pricing is mostly the electricity pricing... Equipment cost is small in comparison. Which means it varies widely depending on where in the world you're wanting it. It isn't valuable enough to ship far.
        Robotbeat 4y ago
        It takes about 200kWh per tonne of oxygen separated. If it’s mostly electricity price (therefore total price is at most twice the electricity price), and your industrial electricity is 7¢/kWh (common in the US), then you’re saying the total price of liquid oxygen is no more than about $30/tonne, even lower than my $100/tonne.

nanomonkey 4y ago

Our existing natural gas pipelines can handle storing up to 10% added hydrogen gas. If we were to start ramping up biogas production from waste streams we could produce some, if not all of the methane that goes along hydrogen in natural gas. This would utilize existing infrastructure, and help with energy production at night (think heating) when solar is unavailable. Hydrogen is only difficult to store if it is pressurized, at low pressures there are low losses due to adiabatic expansion. Embrittlement is only a concern when you're holding back high pressures, and isn't a big concern for pipelines which can conceivably hold a large amount of reserve fuel. I think the purified oxygen is an overlooked resource, as it can be used at, or near, the electrolizer as a method of producing pure syngas from waste organic matter using gasification. Normally woodgas or producer gas isn't desirable because it is made from atmospheric air as the oxidizer which contains a large amount of inert nitrogen which takes up space and produces nitric oxides at high temperatures. By using pure oxygen one can produce higher temperatures in the gasification reactor, and a purer syngas. This could be stored, and then used along with the hydrogen to produce heat and electricity in existing natural gas turbines when it is needed.

pfdietz 4y ago
The use I would think of for the oxygen would be burning fuels in Allam cycle turbines. These use supercritical CO2 and burn fuels with oxygen in the CO2 (oxygen is needed so nitrogen doesn't build up in the CO2). The products of combustion are water and CO2. Water condenses and can be reused (an Allam cycle turbine burning natural gas would be a net producer of liquid water); CO2 from burning natural gas would be tapped off in pure form at zero marginal cost (unlike other CO2 capture methods.) Allam cycle turbines burning hydrogen would not make CO2, of course, but they'd avoid the need for NOx reduction stage after the turbine. One could also imagine a system where CO2 is captured and stored, then used to make methane from hydrogen, that is also then stored. You'd need three kinds of storage reservoirs (methane, CO2, and oxygen) but perhaps this could be easier than storing hydrogen.
- nanomonkey 4y ago
  I'm curious if this could be utilized with less pure fuels such as organic wastes rich with oils and waxes. Supercritical CO2 is often used to remove oils and waxes from organic matter and clothing. The high temperatures and pressures might even be sufficient for pyrolysis of the organic matter, allowing for further removal of combustable materials. Of course organic materials are highly variable and full of other volatiles that may harm the turbines (i.e. sulfur, fatty acids, etc.). Sadly the purity of the exhaust gases would likely be effected as Nitrogen from proteins, along with other elements are going to end up in the exhaust stream. These could all be distilled out, or scrubbed, but with higher energy costs. Still there are lots of exciting developments that can be made to cogeneration power production using organic waste streams.