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> Then you pick the low-hanging fruit and start trying to find a solution to power heat pumps in the winter at night and it's... not as easy. But it's also no

• AnthonyMouse 3y ago
  Storage isn't just a bad fit for that because it's expensive, though. What do you do when it runs down, because it's unusually cold or you have an extended period of low generation, or both? Now it's 20 degrees below freezing and you have no heat.
  • danans 3y ago
    > What do you do when it runs down, because it's unusually cold or you have an extended period of low generation, or both? I'm not talking about going off grid, just energy price arbitrage. You still have the option of pulling power from the grid to heat your house, although potentially at a higher price. With storage, you could also coordinate grid loads during the night so that at any given time the total load on the grid doesn't exceed the grid's generation capacity.
    • AnthonyMouse 3y ago
      > I'm not talking about going off grid, just energy price arbitrage. You still have the option of pulling power from the grid to heat your house, although potentially at a higher price. It's not a different problem for the grid. If the grid is generating nearly all of its power from solar and wind and it's calm and cold and night, where does the grid get the power to run your heat pumps? Storage is not only expensive, it has finite capacity. On the coldest week of the decade when everyone's heating system is using 250% more power than usual, and has been for days, the storage runs down and then what?
      • danans 3y ago
        > On the coldest week of the decade when everyone's heating system is using 250% more power than usual, and has been for days, the storage runs down and then what? Since we're talking about the grid of the future, there are several possible options: - Hydrogen electrolyzed/stored (pressurized or as NH3) during the summer can be used to add supply to the grid. - Pumped hydro increases its output during the cold snap. - Power imported from regions that aren't experiencing the same cold snap with no renewable generation. > If the grid is generating nearly all of its power from solar and wind Since you said "nearly", there is some room for geothermal, synfuels, and maybe SMRs (if they can ever be built economically). The point is that we won't have a lack of carbon-free generation sources or storage options in the future.
        • AnthonyMouse 3y ago
          > Hydrogen electrolyzed/stored (pressurized or as NH3) during the summer can be used to add supply to the grid. > Pumped hydro increases its output during the cold snap. These are essentially other types of storage, and you're trying to go for something where you trade the cost of storage against the cost of the conversion equipment. (It can't be cheaper for both or that's what you'd use all the time.) The nice thing about batteries is that you can draw power from them as fast as you'd usually ever want to, to the point of discharging the entire battery within 30-60 minutes. A 100kWh battery could give you 200kW for half an hour. And of course then two 100kWh batteries could give you 400kW for half an hour. Whereas if you have a 100kW generator and 100kWh of NH3, you can generate 100kW. If you have a 100kW generator and 200kWh of NH3, you can generate at 100kW for two hours, but you can't generate 200kW, much less 400kW. Which kind of leads to the problem here. If you're going to have a 50GW average shortfall for a week, you need 8.4TWh of storage. Ouch. Okay, so that's why we're using the ones with the cheapest storage, but that's still not cheap. And then you need 50,000,000 kW of generation capacity for that type of storage, on top of the storage. But you're only going to use either of them for one week every two years. That seems impractical. > Power imported from regions that aren't experiencing the same cold snap with no renewable generation. It's not obvious how this one is supposed to work either. Say it's -15 in the Northeast, that's trouble, we'll have to import power from Texas. Where it's also winter, and therefore 25 degrees with significant heating demand, and generation there isn't as low this week but it's below average. Texas can handle that, they charge a higher rate at night, people shift demand enough or lower their thermostats and they can break even. But they have none to spare. Okay then, the Midwest? Nope, too close to the Northeast, it's -15 there too. The South then. Finally, a region with spare capacity... but it's only 10% of what you need and the Midwest wants it too. And the general problem with this one is that people are going to optimize it out. If you have cross-continent transmission lines, they'll be used whenever they're useful, which will lower the price of electricity. And then people will build less generation capacity, because it's less needed and less profitable. And then the whole grid has less slack in it and you can't rely on the slack existing in situations like this. See also "just in time" supply chains in an emergency situation. > Since you said "nearly", there is some room for geothermal, synfuels, and maybe SMRs (if they can ever be built economically). But this is kind of the point. You don't build geothermal or nuclear plants for periodic use in an unusual supply crunch. If they're enough of the grid to address this, they're that much of the grid all the time.