4 ms·

Do you have sufficient battery capacity to power your grid through a 90th percentile worst case scenario solar outage? 95th? 99th? How long can it go without

Do you have sufficient battery capacity to power your grid through a 90th percentile worst case scenario solar outage? 95th? 99th? How long can it go without running coal and gas? Nuclear works when you want it to. Solar and wind work when they want to. That's a very big difference when you're producing the electricity people rely on to live their daily lives.

pfdietz 5y ago
It's a very common mistake to think that batteries are to be used to get to a 100% renewable grid. Hydrogen can be much cheaper for (say) the last 10%, because (1) hydrogen has very low capital cost per unit of storage capacity, and (2) the efficiency hit of going through hydrogen vs. batteries is less important when it's just 10% of the total. Think of batteries and hydrogen as analogous to cache memory and main memory in a computer. They have different performance and economic characteristics and compensate for each others weak points. To see this in operation, go to https://model.energy/ https://model.energy/ and try turning hydrogen off and on in the settings. If you simulate for Germany, for example, turning off hydrogen can double the cost of achieving a certain level of constant grid power. Hydrogen can be particularly valuable for places with large seasonal variation or lots of wind (which has a long timescale component in how it varies.) I will add that China is already selling electrolysers for < $300/kW, less than half that simulation's 2030 cost assumption.
- arcticbull 5y ago
  > Hydrogen can be much cheaper for (say) the last 10%, because (1) hydrogen has very low capital cost per unit of storage capacity, and (2) the efficiency hit of going through hydrogen vs. batteries is less important when it's just 10% of the total. Basically all hydrogen comes from fossil fuels. It's just natural gas with extra steps.
  - pfdietz 5y ago
    That's true right now, but that doesn't mean that hydrogen has to come from fossil fuels in the future (any more than most electrical power coming from fossil fuels right now means that that must also be the case in the future.) When describing hydrogen for energy storage in a 100% renewable grid, the hydrogen would be produced by electrolysis using renewable energy.

pfdietz 5y ago

It's a very common mistake to think that batteries are to be used to get to a 100% renewable grid. Hydrogen can be much cheaper for (say) the last 10%, because (1) hydrogen has very low capital cost per unit of storage capacity, and (2) the efficiency hit of going through hydrogen vs. batteries is less important when it's just 10% of the total. Think of batteries and hydrogen as analogous to cache memory and main memory in a computer. They have different performance and economic characteristics and compensate for each others weak points. To see this in operation, go to https://model.energy/ https://model.energy/ and try turning hydrogen off and on in the settings. If you simulate for Germany, for example, turning off hydrogen can double the cost of achieving a certain level of constant grid power. Hydrogen can be particularly valuable for places with large seasonal variation or lots of wind (which has a long timescale component in how it varies.) I will add that China is already selling electrolysers for < $300/kW, less than half that simulation's 2030 cost assumption.

arcticbull 5y ago
> Hydrogen can be much cheaper for (say) the last 10%, because (1) hydrogen has very low capital cost per unit of storage capacity, and (2) the efficiency hit of going through hydrogen vs. batteries is less important when it's just 10% of the total. Basically all hydrogen comes from fossil fuels. It's just natural gas with extra steps.
- pfdietz 5y ago
  That's true right now, but that doesn't mean that hydrogen has to come from fossil fuels in the future (any more than most electrical power coming from fossil fuels right now means that that must also be the case in the future.) When describing hydrogen for energy storage in a 100% renewable grid, the hydrogen would be produced by electrolysis using renewable energy.