4 ms·

Sure, since the lab is running their perovskite at 600 C anyway, just add CO2 in a chamber with some nickel and get methane out via the Sabatier reaction. Send

Sure, since the lab is running their perovskite at 600 C anyway, just add CO2 in a chamber with some nickel and get methane out via the Sabatier reaction. Send the methane to where ever its needed.

eloff 7y ago
So many problems are solved so easily by "just" doing simple thing X. Maybe this really is a simple fix. It doesn't sound that way to me though.
- ChuckMcM 7y ago
  It's not. The response is 'accurate' not 'easy' :-) The biggest challenge is getting a source of CO2 using less energy than you are going to get back by burning the methane. Thermodynamics doesn't let you cheat sadly. When evaluating these sorts of things you follow the energy consumption of each step and remove it from the initial pool of energy. Energy out over energy in will give you a way to compare methods for "goodness" regardless of complexity. Processes that have net negative energy are clearly in the "bad" category. Any positive is something. Localized schemes like hydro pumping do quite well in this equation. It is distance schemes that suffer. Distance schemes are hard because pushing electrons through a wire spends power just getting through the wire. Eventually its all gone. This is why you can't just cover 1/3 of Nevada with PV solar cells and power the grid from that one state. So distance means transforming electricity into some other energy (chemical, potential, kinetic, thermal), moving it physically somewhere else (ideally without much loss) and then converting it back into electricity at the destination. One of the more fanciful ideas I heard was train cars full of Tesla powerwall packs. If you've ever seen an operating coal fired power plant you may have seen the long line of coal cars in a train that pulls in each day. Once at the plant the cars are slowly pulled through the plant, dumping coal when they need to into the feed mechanism. Eventually a string of empty cars is on the other side to take back to be refilled. Imagine doing that with powerwalls. Cars pull up, connect electrically to the plant and start discharging. Once they are down to their "empty" level the car disconnects and moves on. I think it would be fascinating to watch.
  - RandallBrown 7y ago
    Would the energy cost of moving the electricity be lower than the energy cost of just transmitting it over power lines?
    - ChuckMcM 7y ago
      Depends almost entirely on distance. Back in one of my college physics classes in LA we analyzed moving electricity from Hoover Dam in (Nevada/Arizona) to LA. It was a lot of fun. You can raise the voltage so you need less current but then you have to raise the wires so they don't arc to the ground and separate them. As I recall (it was a while ago) we were using the Fischer-Tropsch[1] process to convert electricity into oil to transport by tanker to fossil fueled plants. You plot all the variables (voltage, current, distance) and there are regions where it is better to convert it and regions where it isn't [2] https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces...
  - effie 7y ago
    > spends power just getting through the wire. Eventually its all gone. No, transmission losses for such concentrated power generation could be kept acceptable single digit percent by building a proper power transmission system. Just use higher voltage, thicker wires. It would be expensive, but if Nevada was a great energy source, it could be worth it long term. > This is why you can't just cover 1/3 of Nevada with PV solar cells and power the grid from that one state. I can think of more substantial problems with that - fragile panels exposed to harmful environment, manufacturing and maintaining panels generates too much waste per kWh, unreliable operation dependent on weather. If Nevada was to be used as a primary center for energy generation, I suggest uranium/thorium reactors. They are better in every possible way.
    - ncmncm 7y ago
      Better, except that they take too long to build, cost too much to operate, and have proven incompatible with sound public policy.
triceratops 7y ago
Thanks for the response. In another comment you mentioned that getting the CO2 would likely cost more energy than would be generated by burning the methane. Is there any reason you couldn't burn the hydrogen directly? I'm a chem noob so this might be a stupid question.
- ChuckMcM 7y ago
  Its not a stupid question, I'm sure lots of folks wonder the same thing. The challenge as I understand it is holding on to the hydrogen. As a gas, hydrogen is really really small and not very dense. Storing, transporting, and handling hydrogen is really hard. I got a chance to see the hydrogen refueling station at a hydrogen bus pilot project and keeping enough hydrogen (without spending all the energy to chill it down in to liquid form) and dispensing it pretty amazing. Its way simpler to use gas generators (things that out gas hydrogen) like they did for the big zeppelins[1]) That is why most schemes that have free hydrogen available, if they aren't using fuel cells on site, usually have a process for capturing the hydrogen in a form that is easier to handle and transport as well as convert back into either heat or hydrogen. [1] https://welweb.org/ThenandNow/Hydrogen%20Generation.html https://welweb.org/ThenandNow/Hydrogen%20Generation.html

Sure, since the lab is running their perovskite at 600 C anyway, just add CO2 in a chamber with some nickel and get methane out via the Sabatier reaction. Send the methane to where ever its needed.

eloff 7y ago

So many problems are solved so easily by "just" doing simple thing X. Maybe this really is a simple fix. It doesn't sound that way to me though.

ChuckMcM 7y ago
It's not. The response is 'accurate' not 'easy' :-) The biggest challenge is getting a source of CO2 using less energy than you are going to get back by burning the methane. Thermodynamics doesn't let you cheat sadly. When evaluating these sorts of things you follow the energy consumption of each step and remove it from the initial pool of energy. Energy out over energy in will give you a way to compare methods for "goodness" regardless of complexity. Processes that have net negative energy are clearly in the "bad" category. Any positive is something. Localized schemes like hydro pumping do quite well in this equation. It is distance schemes that suffer. Distance schemes are hard because pushing electrons through a wire spends power just getting through the wire. Eventually its all gone. This is why you can't just cover 1/3 of Nevada with PV solar cells and power the grid from that one state. So distance means transforming electricity into some other energy (chemical, potential, kinetic, thermal), moving it physically somewhere else (ideally without much loss) and then converting it back into electricity at the destination. One of the more fanciful ideas I heard was train cars full of Tesla powerwall packs. If you've ever seen an operating coal fired power plant you may have seen the long line of coal cars in a train that pulls in each day. Once at the plant the cars are slowly pulled through the plant, dumping coal when they need to into the feed mechanism. Eventually a string of empty cars is on the other side to take back to be refilled. Imagine doing that with powerwalls. Cars pull up, connect electrically to the plant and start discharging. Once they are down to their "empty" level the car disconnects and moves on. I think it would be fascinating to watch.
- RandallBrown 7y ago
  Would the energy cost of moving the electricity be lower than the energy cost of just transmitting it over power lines?
  - ChuckMcM 7y ago
    Depends almost entirely on distance. Back in one of my college physics classes in LA we analyzed moving electricity from Hoover Dam in (Nevada/Arizona) to LA. It was a lot of fun. You can raise the voltage so you need less current but then you have to raise the wires so they don't arc to the ground and separate them. As I recall (it was a while ago) we were using the Fischer-Tropsch[1] process to convert electricity into oil to transport by tanker to fossil fueled plants. You plot all the variables (voltage, current, distance) and there are regions where it is better to convert it and regions where it isn't [2] https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process https://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_proces...
- effie 7y ago
  > spends power just getting through the wire. Eventually its all gone. No, transmission losses for such concentrated power generation could be kept acceptable single digit percent by building a proper power transmission system. Just use higher voltage, thicker wires. It would be expensive, but if Nevada was a great energy source, it could be worth it long term. > This is why you can't just cover 1/3 of Nevada with PV solar cells and power the grid from that one state. I can think of more substantial problems with that - fragile panels exposed to harmful environment, manufacturing and maintaining panels generates too much waste per kWh, unreliable operation dependent on weather. If Nevada was to be used as a primary center for energy generation, I suggest uranium/thorium reactors. They are better in every possible way.
  - ncmncm 7y ago
    Better, except that they take too long to build, cost too much to operate, and have proven incompatible with sound public policy.

triceratops 7y ago

Thanks for the response. In another comment you mentioned that getting the CO2 would likely cost more energy than would be generated by burning the methane. Is there any reason you couldn't burn the hydrogen directly? I'm a chem noob so this might be a stupid question.

ChuckMcM 7y ago
Its not a stupid question, I'm sure lots of folks wonder the same thing. The challenge as I understand it is holding on to the hydrogen. As a gas, hydrogen is really really small and not very dense. Storing, transporting, and handling hydrogen is really hard. I got a chance to see the hydrogen refueling station at a hydrogen bus pilot project and keeping enough hydrogen (without spending all the energy to chill it down in to liquid form) and dispensing it pretty amazing. Its way simpler to use gas generators (things that out gas hydrogen) like they did for the big zeppelins[1]) That is why most schemes that have free hydrogen available, if they aren't using fuel cells on site, usually have a process for capturing the hydrogen in a form that is easier to handle and transport as well as convert back into either heat or hydrogen. [1] https://welweb.org/ThenandNow/Hydrogen%20Generation.html https://welweb.org/ThenandNow/Hydrogen%20Generation.html