5 ms·

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

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
        galangalalgol 3y ago
        Propane combustion vehicles are common, and I'd guess a fuel cell would extract roughly 30% extra energy from the same fuel. They typically have battery efficiencies.
  - cduzz 3y ago
    Several tesla superchargers near where I live have fuel cell setups, presumably to shave peak loads for the rare cases that the charging stations are all in use and all charging at peak rates.
    - londons_explore 3y ago
      I suspect they have batteries rather than fuel cells? Tesla is known to colocate them for exactly the reasons you say - also to shift load to cheaper hours of the day and to get paid by the grid for balancing services.
      - sp332 3y ago
        I think the current ones don't use generators, but that one time they used a gas generator to charge Teslas, called it a "battery swap station", and got a bunch of money from California that was supposed to go to zero-emissions car projects. I doubt they'll ever live that down.
        panick21_ 3y ago
        Live what down? California paid for a research and demonstration project. Tesla did that but decide for a whole number of reasons that it wasn't worth doing.
        cduzz 3y ago
        sorry for the late reply -- definitely fuel cell setups. Orleans MA and Hyannis MA supercharger stations. The one in Hyannis is right next to the superchargers, the other is 2 minutes walk away. I believe one or both have "bloom energy" branding. I can't find a good picture on the internet.
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.

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
      - galangalalgol 3y ago
        Propane combustion vehicles are common, and I'd guess a fuel cell would extract roughly 30% extra energy from the same fuel. They typically have battery efficiencies.
- cduzz 3y ago
  Several tesla superchargers near where I live have fuel cell setups, presumably to shave peak loads for the rare cases that the charging stations are all in use and all charging at peak rates.
  - londons_explore 3y ago
    I suspect they have batteries rather than fuel cells? Tesla is known to colocate them for exactly the reasons you say - also to shift load to cheaper hours of the day and to get paid by the grid for balancing services.
    - sp332 3y ago
      I think the current ones don't use generators, but that one time they used a gas generator to charge Teslas, called it a "battery swap station", and got a bunch of money from California that was supposed to go to zero-emissions car projects. I doubt they'll ever live that down.
      - panick21_ 3y ago
        Live what down? California paid for a research and demonstration project. Tesla did that but decide for a whole number of reasons that it wasn't worth doing.
      - cduzz 3y ago
        sorry for the late reply -- definitely fuel cell setups. Orleans MA and Hyannis MA supercharger stations. The one in Hyannis is right next to the superchargers, the other is 2 minutes walk away. I believe one or both have "bloom energy" branding. I can't find a good picture on the internet.

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.