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Curtailment already happens routinely today for solar PV in some countries (eg Spain) - though it's due to running out of grid capacity in the right places, not

Curtailment already happens routinely today for solar PV in some countries (eg Spain) - though it's due to running out of grid capacity in the right places, not oversupply on the grid as a whole. Economically for PV farms which are being curtailed building colocated hydrogen storage makes some sense. If there's no curtailment (and if you have sites available in the country) then pumped storage makes a lot more sense. But either way, building sufficient storage to do anything other than peak-shave is very, very, very expensive, so we'd be better off with nuclear even at a 2-3x cost overrun.

pydry 3y ago
Pumped storage and hydrogen are, paired with wind or solar, much, much cheaper than nuclear power. We'd even be better off if all solar and wind power were converted into hydrogen first and only then turned into electricity. Not because thats cheap but because nuclear power is that expensive. Nuclear power only becomes cost competitive when you use it to share costs with the nuclear-military industrial complex - which is why it is built.
- tomatocracy 3y ago
  For intraday variation, yes I agree - intermittent renewables+storage works well. But for longer term variability (eg wind droughts) or even worse, if you wanted to cover seasonal variation in production (solar PV can have enormous seasonal variability in northerly latitudes), the amount of storage you need in MWh is absolutely enormous. This is why nuclear still winds up being much more sensible.
  - pydry 3y ago
    Nuclear power doesnt store energy. It will pump out 2GW all the time whether you need 6GW or you need 0GW. It doesn't really help in that respect at all because it can't be scaled up and down. It's not a peaker. Seasonal variation is best dealt with by creating and storing hydrogen underground. It's easy to store lots of MWhs this way. This isnt as efficient as a battery or pumped storage when roundtripped (~50% not 90%) but if seasonal variation is 4-7% of your power then that just means you'll have to overproduce in aggregate by 10-20% to accommodate this. That's not really a problem given how dirt cheap solar and wind are - about that much is being lost to curtailment already. The funny thing is, even if all electricity generated by solar and wind were stored as gas before being used it would still work out a bit cheaper than nuclear power. Nuclear is that expensive.
    - tomatocracy 3y ago
      Seasonal variation in PV production is much much more than 4-7% in northern Europe. In the UK daylight hours vary between 8hrs in winter and 16.5hrs in summer (more in Scotland), and on top of that winter has many more overcast days meaning you get a lot less irradiation during those hours. As a result, total irradiation in December is many multiples lower than that in June. Given that, it's not (currently) economically viable to build storage+PV on anything approaching the scale we would need to replace baseload generation completely.
      - pydry 3y ago
        >Seasonal variation in PV production is much much more than 4-7% in northern Europe. 4-7% isn't seasonal variation in PV production. It's the amount of grid energy that needs to be supplied under a hypothetical 100% solar/wind/pumped storage grid when: * Solar output is low * and wind output is low * and ~8 hours of pumped storage is depleted. Obviously the wind blows at night and pumped storage works at night and electricity demand is lower at night. Obviously seasonal storage would not have to be tapped every night. >Given that, it's not (currently) economically viable to build storage+PV Why would that be given? It's categorically false. The opposite is true. Maybe what you meant to say was that "GIVEN 2GW of solar energy was being produced today" AND "coire glas is under construction" because it's highly economically viable, maybe we should lend a hand in the form of subsidies in scaling that up? Or did you want to push those subsidies to a form of energy with a 5x higher LCOE?
        tomatocracy 3y ago
        I'm not saying that Solar PV isn't economically viable at all (I've invested in Solar PV projects for my day job in fact, and obviously wouldn't have done so if I didn't think this). My concern is the "end game", where all current baseload generation gets disconnected from the grid (including current nuclear when it reaches end of life). Solar PV's current low LCOE doesn't help you a lot in that case because in order to actually deliver the energy needed at the right time you will need to do some combination of (1) build a lot more PV than "needed" and routinely curtail it significantly in summer (ie significantly derate nameplate capacity) and (2) build a lot more storage to deal with seasonal and other variations. This is when nuclear starts to look like it makes sense as part of the energy mix in my view.
  - pfdietz 3y ago
    No, you use green hydrogen for that storage use case. This ends up being cheaper than using nuclear.
pfdietz 3y ago
> But either way, building sufficient storage to do anything other than peak-shave is very, very, very expensive, so we'd be better off with nuclear even at a 2-3x cost overrun. This is only true if you imagine batteries as the only storage technology. But complementary storage technologies, like hydrogen, allow 100% RE to be achieved at a cost that will likely be lower than what nuclear would allow.

pydry 3y ago

Pumped storage and hydrogen are, paired with wind or solar, much, much cheaper than nuclear power. We'd even be better off if all solar and wind power were converted into hydrogen first and only then turned into electricity. Not because thats cheap but because nuclear power is that expensive. Nuclear power only becomes cost competitive when you use it to share costs with the nuclear-military industrial complex - which is why it is built.

tomatocracy 3y ago
For intraday variation, yes I agree - intermittent renewables+storage works well. But for longer term variability (eg wind droughts) or even worse, if you wanted to cover seasonal variation in production (solar PV can have enormous seasonal variability in northerly latitudes), the amount of storage you need in MWh is absolutely enormous. This is why nuclear still winds up being much more sensible.
- pydry 3y ago
  Nuclear power doesnt store energy. It will pump out 2GW all the time whether you need 6GW or you need 0GW. It doesn't really help in that respect at all because it can't be scaled up and down. It's not a peaker. Seasonal variation is best dealt with by creating and storing hydrogen underground. It's easy to store lots of MWhs this way. This isnt as efficient as a battery or pumped storage when roundtripped (~50% not 90%) but if seasonal variation is 4-7% of your power then that just means you'll have to overproduce in aggregate by 10-20% to accommodate this. That's not really a problem given how dirt cheap solar and wind are - about that much is being lost to curtailment already. The funny thing is, even if all electricity generated by solar and wind were stored as gas before being used it would still work out a bit cheaper than nuclear power. Nuclear is that expensive.
  - tomatocracy 3y ago
    Seasonal variation in PV production is much much more than 4-7% in northern Europe. In the UK daylight hours vary between 8hrs in winter and 16.5hrs in summer (more in Scotland), and on top of that winter has many more overcast days meaning you get a lot less irradiation during those hours. As a result, total irradiation in December is many multiples lower than that in June. Given that, it's not (currently) economically viable to build storage+PV on anything approaching the scale we would need to replace baseload generation completely.
    - pydry 3y ago
      >Seasonal variation in PV production is much much more than 4-7% in northern Europe. 4-7% isn't seasonal variation in PV production. It's the amount of grid energy that needs to be supplied under a hypothetical 100% solar/wind/pumped storage grid when: * Solar output is low * and wind output is low * and ~8 hours of pumped storage is depleted. Obviously the wind blows at night and pumped storage works at night and electricity demand is lower at night. Obviously seasonal storage would not have to be tapped every night. >Given that, it's not (currently) economically viable to build storage+PV Why would that be given? It's categorically false. The opposite is true. Maybe what you meant to say was that "GIVEN 2GW of solar energy was being produced today" AND "coire glas is under construction" because it's highly economically viable, maybe we should lend a hand in the form of subsidies in scaling that up? Or did you want to push those subsidies to a form of energy with a 5x higher LCOE?
      - tomatocracy 3y ago
        I'm not saying that Solar PV isn't economically viable at all (I've invested in Solar PV projects for my day job in fact, and obviously wouldn't have done so if I didn't think this). My concern is the "end game", where all current baseload generation gets disconnected from the grid (including current nuclear when it reaches end of life). Solar PV's current low LCOE doesn't help you a lot in that case because in order to actually deliver the energy needed at the right time you will need to do some combination of (1) build a lot more PV than "needed" and routinely curtail it significantly in summer (ie significantly derate nameplate capacity) and (2) build a lot more storage to deal with seasonal and other variations. This is when nuclear starts to look like it makes sense as part of the energy mix in my view.
- pfdietz 3y ago
  No, you use green hydrogen for that storage use case. This ends up being cheaper than using nuclear.

pfdietz 3y ago

> But either way, building sufficient storage to do anything other than peak-shave is very, very, very expensive, so we'd be better off with nuclear even at a 2-3x cost overrun. This is only true if you imagine batteries as the only storage technology. But complementary storage technologies, like hydrogen, allow 100% RE to be achieved at a cost that will likely be lower than what nuclear would allow.