⇒ - Backup. Of course, anything inherently CO₂-producing is out for this, and this includes gas, obviously, and biomass (maybe less obviously, but think about it). And that leaves?
So, this is my plan: keep building solar and wind till peak demand is sometimes met, build nuclear to replace all the fossil »backup«.
⇒ - Storage: obviously, we'd want to smoothen out the time dimension as well. This means adding storage that can meet 100% of demand as well (volatile sources frequently drop to 0), and feeding it with enough additional clean sources that it can fill every expected gap (and gap accumulation).
And here I'd like to repeat my point from before: the best (most effective) storage we have right now is pumped hydro, by far. And pumped hydro is not enough, by far.
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⇒ Now the volatile supply line has valleys between the peaks. If you integrate over time and place, the supply line covers about 40% of demand in this situation.
That is /very rough/ and depends on a lot of factors, but my point is the same if it were 30% or 60%: where does the rest come from?
- Transmission: as already mentioned, we know how to transmit electric energy, it's just material and effort. This smoothes out the »place« dimension.
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⇒ (But at least we already have transmission tech, it is now just a question of materials and effort.)
So, assume that we have enough wind and solar that we can regularly produce 100% of demand from them. You can imagine peaks just touching the demand line at top demand.
(You could imagine more than that, but that would mean overbuilding, which hurts the economics quite badly while not making the end result much better.)
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⇒ Aside: the »place« problem is that you can't build solar panels and wind turbines just anywhere, and they need a lot of space. E. g. Germany has now the problem that the wind blows much better in the north, but the industry is more in the south. So, you need a lot more/stronger transmission lines. Same for offshore wind: more wind at sea, but you need a lot of cables.
The more wind and solar you already have, the more the good places are already taken.
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I'll try to explain the 40%, sorry for the parts that you already know.
Electric energy is always produced at the same time (and »place« roughly) as it is consumed. (You can't pump electricity into some reservoir to be consumed later, you always need a different energy form for storage.)
The problem with volatile sources is that they mostly (more than half) produce energy at the wrong time and/or the wrong place, and at other times produce nothing.
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@MattMastodon @Sodis We're going in circles. Volatile sources can only supply 40% of current demand for £50/MWh. The question is what fills the rest.
If storage, then the price goes up immediately by at least two conversion losses from/to storage, in addition to the cost of storage itself. Which doesn't exist at the needed scalability.
Pointing to single projects is not meaningful, as we need to build a fleet anyway, which has its own dynamics.
@MattMastodon @Sodis If you include construction and disposal (and transport and so on…) it is called lifecycle costs. First image shows that per energy produced (sorry german, »AKW neu« is new-built nuclear).
Uranium comes from all over the world. Second image shows the situation a few years ago. Niger is place 5, Russia place 7.
@MattMastodon @Sodis Again: that demand is lower at night is already factored in. Roughly 40% of demand can be directly met by volatile sources. You may think nuclear is slow to deploy, but it's still much faster than anything that doesn't exist.
The gap is 60%. Gas is a fossil fuel. Varying use is mostly a euphemism. If you hurt industry, you won't have the industry to build clean energy sources.
@MattMastodon @Sodis Careful about labels. »Renewables« often includes biomass (which is just fast-track fossil tbh) and hydro (which is not so volatile). I'm talking about wind and solar specifically (volatiles).
40% is roughly the mean capacity factor of a good mix of volatiles. This is what you can directly feed to the user from the windmill/panel, without storage. You can expand a bit by massive overbuilding, but you can't overbuild your way out of no wind at night.
@Sodis @MattMastodon Nuclear power plants can quite easily do load following. It happens regularly e. g. in France. However, since it has the lowest running costs, other sources are usually cut first as far as possible.
@MattMastodon @Sodis My thinking about biomass: if we don't burn it, it will not be released as CO₂ to the atmosphere.
I guess the thinking about biomass was: if we only burned biomass, not fossil mass, then we'd have an equilibrium and no problem. But saying that biomass is net-zero gets it backwards. The CO₂ doesn't care where it's coming from. It is our task to produce as little CO₂ as possible. The goal is to get below the amount of CO₂ /captured/ by biological processes.