4 ms·

Electrolyzer reactions tend to be reversible... If they could do the reverse (water+propane to CO2+hydrogen+electricity) at the efficiency claimed (91%), they

Electrolyzer reactions tend to be reversible... If they could do the reverse (water+propane to CO2+hydrogen+electricity) at the efficiency claimed (91%), they can replace all gas turbine generators (who typically have efficiencies of only 60% at best)

murkt 3y ago
Reversed electrolyzer would be called a fuel cell then? What are their typical efficiencies?
- londons_explore 3y ago
  Yep. Fuel cell efficiency varies widely, but the efficiency of the reverse process is a good guide - typically efficiency is fairly symmetrical.
fodkodrasz 3y ago
Gas turbines scale much better than fuel cells, and can achieve great power density, are durable, can be produced without too much exotic materials needed, are a proven technology. If you can solve the storage of intermittent renewable production as conversion to propane, you already won!
- londons_explore 3y ago
  At a current density of 395mA/cm² @0.8V, these already won on the power density and scalability front. 500 stacked 0.5mm layers of this would make 400 volts for an ev battery or stationary AC generator. It would have a power density of 6.3 kilowatts per litre, far exceeding both lithium batteries and gas turbines.
  - fodkodrasz 3y ago
    Did they? Are they capable to be scaled to 100 MW scales with MTBF of years already?
  - galangalalgol 3y ago
    Propane fuel cells already exist, and are in use for remote power. The problem with using them for cars is that they operate at high temperature, so you spend a lot of battery warming the cell for steady state, but most trips are short so you would be there before it got to temp. Might make sense as a phev sort of thing where you punch in a trip and it decides to warm it up or not. You'd always leave enough battery to warm the cell while driving so you never get stuck.
    - londons_explore 3y ago
      High temperature isn't a problem for cars. It's simple enough to have a small fuel cell which can be heated up quickly, which in turn can provide the energy required to heat up a larger cell if needed. A small battery can drive you a few miles while that process is happening. The small fuel cell could then recharge the battery while parked if most journeys are only a couple of miles, avoiding the energy cost of heating the large cell except for extended journeys.
      - panick21_ 3y ago
        This is massively more complex then you make it sound. And if it doesnt work at least as well as current ICE its not going be used. There is a reason this simply isnt done. If you want to use that fuel, just burn it.
      - galangalalgol 3y ago
        Not sure why no one has done it? Not carbon neutral I guess, but paired with this and solar power it would be. Batteries are already so good is probably part of it too. But adding about 25% travel time on long drives is annoying.
        infinityio 3y ago
        Up until this point I'd imagine there was no significant advantage to creating propane vehicles unless they could be made significantly more efficient than petrol or diesel (which I'm guessing is not known to be the case) by comparison, this discovery could make it a green-vs-brown fuel debate, at which point it would be much more valuable to invest in for vehicles
- rjmunro 3y ago
  I wonder if you can have the same plant act as both a propane producer at times of extra power available on the grid, but also generate electricity when there is a shortage. Then the power density and exotic materials are irrelevant as the plant already exists. You'd use the plant mainly to make propane, just run it backwards when electricity prices were the highest.
legulere 3y ago
Shouldn’t the chemical reaction be: 4 H2O + 3 CO2 <=> C3H8 + 5 O2
- londons_explore 3y ago
  The reaction described in the paper doesn't have spare oxygen on either side, presumably because oxygen has a habit of destroying catalysts and being explosive when mixed with hydrocarbons. Instead hydrogen is required.
  - jabl 3y ago
    (Not having access to the paper) So are you saying the reaction is 10 H2 + 3 CO2 <=> C3H8 + 6 H2O Of course, neither this nor the reaction mentioned in the parent comment matches up with the diagram in the linked article which says "water + CO2 => propane + water", which well, doesn't make sense..
  - bertil 3y ago
    So you would need to have two separate electrolyzing processes, one that isolates H2 and one that runs this operation? How much energy would have to go into the first one? I’m asking because a lot of the demand for hydrocarbon that I see mentioned is for processes that have more efficient, non-hydrocarbon equivalents.

murkt 3y ago

Reversed electrolyzer would be called a fuel cell then? What are their typical efficiencies?

londons_explore 3y ago
Yep. Fuel cell efficiency varies widely, but the efficiency of the reverse process is a good guide - typically efficiency is fairly symmetrical.

fodkodrasz 3y ago

Gas turbines scale much better than fuel cells, and can achieve great power density, are durable, can be produced without too much exotic materials needed, are a proven technology. If you can solve the storage of intermittent renewable production as conversion to propane, you already won!

londons_explore 3y ago
At a current density of 395mA/cm² @0.8V, these already won on the power density and scalability front. 500 stacked 0.5mm layers of this would make 400 volts for an ev battery or stationary AC generator. It would have a power density of 6.3 kilowatts per litre, far exceeding both lithium batteries and gas turbines.
- fodkodrasz 3y ago
  Did they? Are they capable to be scaled to 100 MW scales with MTBF of years already?
- galangalalgol 3y ago
  Propane fuel cells already exist, and are in use for remote power. The problem with using them for cars is that they operate at high temperature, so you spend a lot of battery warming the cell for steady state, but most trips are short so you would be there before it got to temp. Might make sense as a phev sort of thing where you punch in a trip and it decides to warm it up or not. You'd always leave enough battery to warm the cell while driving so you never get stuck.
  - londons_explore 3y ago
    High temperature isn't a problem for cars. It's simple enough to have a small fuel cell which can be heated up quickly, which in turn can provide the energy required to heat up a larger cell if needed. A small battery can drive you a few miles while that process is happening. The small fuel cell could then recharge the battery while parked if most journeys are only a couple of miles, avoiding the energy cost of heating the large cell except for extended journeys.
    - panick21_ 3y ago
      This is massively more complex then you make it sound. And if it doesnt work at least as well as current ICE its not going be used. There is a reason this simply isnt done. If you want to use that fuel, just burn it.
    - galangalalgol 3y ago
      Not sure why no one has done it? Not carbon neutral I guess, but paired with this and solar power it would be. Batteries are already so good is probably part of it too. But adding about 25% travel time on long drives is annoying.
      - infinityio 3y ago
        Up until this point I'd imagine there was no significant advantage to creating propane vehicles unless they could be made significantly more efficient than petrol or diesel (which I'm guessing is not known to be the case) by comparison, this discovery could make it a green-vs-brown fuel debate, at which point it would be much more valuable to invest in for vehicles
rjmunro 3y ago
I wonder if you can have the same plant act as both a propane producer at times of extra power available on the grid, but also generate electricity when there is a shortage. Then the power density and exotic materials are irrelevant as the plant already exists. You'd use the plant mainly to make propane, just run it backwards when electricity prices were the highest.

legulere 3y ago

Shouldn’t the chemical reaction be: 4 H2O + 3 CO2 <=> C3H8 + 5 O2

londons_explore 3y ago
The reaction described in the paper doesn't have spare oxygen on either side, presumably because oxygen has a habit of destroying catalysts and being explosive when mixed with hydrocarbons. Instead hydrogen is required.
- jabl 3y ago
  (Not having access to the paper) So are you saying the reaction is 10 H2 + 3 CO2 <=> C3H8 + 6 H2O Of course, neither this nor the reaction mentioned in the parent comment matches up with the diagram in the linked article which says "water + CO2 => propane + water", which well, doesn't make sense..
- bertil 3y ago
  So you would need to have two separate electrolyzing processes, one that isolates H2 and one that runs this operation? How much energy would have to go into the first one? I’m asking because a lot of the demand for hydrocarbon that I see mentioned is for processes that have more efficient, non-hydrocarbon equivalents.