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Solar and wind has a lot of 'negative externalities' though that are generally borne by the grid or other operators. I think the economics really work against i
by martinald 9y ago
Solar and wind has a lot of 'negative externalities' though that are generally borne by the grid or other operators. I think the economics really work against it at high% penetration (30-40%+).
The problem is that solar and wind requires backup generation, usually CCGT natural gas.
This is ok until you scale higher and higher. You end up having CCGT only producing 20-40% of the time (to fill in for wind and solar blips). This massively increases the capex of CCGT plants, as you're only producing rarely. This would get more and more extreme with more solar+wind penetration.
Another massive problem is solar+wind overproduction, which is really hard to solve and is starting to really hit the German, UK and California grids. On very sunny AND windy days you get massive energy overproduction. You then have to either:
a) Turn off solar+wind remotely (often very expensive to retrofit to existing installations as the Germans found out)
b) Pay other (natgas, coal, nuclear, etc) operators to shut down, which can be very expensive
c) Hope that negative electricity prices make more demand. This is unlikely to happen as industrial users can't switch on extra production quick enough to respond to this.
This is made worse by feed in tariffs being paid at any energy price, incentivizing solar+wind to continue generating even if electricity price is negative (say it is -€0.05kWh spot, but your FIT is €0.20/kWh, you are still going to produce as you will net 0.15euro per kWh.
The two 'solutions' which are often mentioned are battery storage and HVDC long distance transmission.
Battery storage is still horrendously expensive on a kWh basis. It may come down, but this is an enormous problem. I am personally not sure there is enough lithium left that is easily extracted to make this viable at the scale (billions of kWh) required.
HVDC connections I also am suspicious of - if it's sunny and windy in Germany, it is likely to also be the same 1000km away more or less.
- mikeash 9y ago> Turn off solar+wind remotely (often very expensive to retrofit to existing installations as the Germans found out) If we're talking about problems that show up when wind/solar becomes an order of magnitude more prevalent than it is now, why would you care about the cost of retrofitting anything?
- dfox 9y agoThis is problem that happens in the German/European electrical grid right now, not at some point in future.
- mikeash 9y agoRight, but in the context of a world where 30-40% of the grid is solar/wind, it's easy.
- martinald 9y agoIt's not. Germany is having to do this right now - hitting 30-40% and it's really expensive.
- mikeash 9y agoBecause they apparently didn't anticipate this and now have to retrofit the equipment. If you're building out new stuff, you don't have to retrofit.
- martinald 9y agoYes but little to no new stuff is getting fitted with this when installed outside of Germany. It significantly puts the price of installs up. You have to dump the power somewhere and it's not cheap/easy to.
- dfox 9y agoI would assume that all-DC grid would happen before that (and solve the issues with grid stability). Extrapolating from the rate at which Europe migrated from 110V AC to 230V AC you are looking at at least 50 years for that to happen.
- ZeroGravitas 9y agoWeirdly, every story I read about this as it starts to happen on windy/sunny weekends and holidays is headlined "Excess solar/wind blah blah" and when you read the story, there's still coal and gas powered electricity production happening at the same time. Even in your entirely hypothetical example you say they're having to pay natgas and coal to stop production. Is it just me or is that really weird? I mean turning off coal and gas is kind of the point, isn't it?
- martinald 9y agoCoal can't be shut down easily, it's incredibly expensive and inefficient to dial it up and down. Natgas is easier but still quite a slow process. If you could turn gas and coal up and down in a few minutes, then perhaps you would have a point. But coal can take 6-24hrs and natgas 1-4hrs. It won't suddenly stop when you have a massive gust of wind.
- ZeroGravitas 9y agoWind and solar generation are highly predictable on those timescales, you can find predicted and actual generation graphs from various sources. They're certainly more predictable than demand. More realistic excuses I've heard are long term contracts, potentially with minimum run times for fossil plants. Which are therefore the actual problem at the moment.