On good days the plants would compress air into man made caves. After the cave reached a certain pressure, the generator would distribute energy as a pass through. If there were bad generation days out SW, the compressed gas would spin turbines at the plant. I believe that each plant was to have 3-5 days worth of common load production. After that, I think there were fallback generators like gas.
The reason I bring this up, is that battery/storage can be more than what we normally think about. In the case of the caves, there are several states that have natural formations. Investment in this idea, or others could reap great returns for the future.
Looks like there are at least 3 operating CAES plants: Huntorf, Germany [2], McIntosh, Alabama [3], and Gaines, Texas [4].
[1] http://www.duke-energy.com/news/releases/2014092301.asp
[2] https://www.eon.com/en/about-us/structure/asset-finder/hunto...
Pumped storage is vastly better than batteries. Also the variance between median days and calm days for wind is far less extreme than generally assumed. PV solar also provides power in cloudy weather.
Anyway the US can get to ~99.99% from ~30% oversupply and ~6 hours of grid storage which is vastly less than many people assume.
PS: Cloudy calm days over large areas are fairly rare. Heavy clouds are generally associated with weather and increased wind. EX: Hurricane incoming, solar down wind UP.
Purpose-built pumped storage plants, such as Helms near Fresno, tend to have much smaller reservoirs, about enough for a daily cycle, and they go from full to empty and back each day. This annoys some people. They're not recreational lakes. Efficiency is 60% - 80% round trip from electricity in to electricity out.
Actually, the variance is worse than assumed by enthusiasts. Here's today's output from wind, hour by hour, for the entire CAISO area, which is about 400 miles across and covers most of California.[1] Today was a bad day; about 10x variation between peak wind and minimum wind. 5:1 is typical; a good day is 2:1.
You can also see similar data for PJM, which covers the Northeastern US.[2] Today's wind variation is about 2:1.
There's a myth that, with enough transmission distance, fluctuations in wind will average out. The two largest power grids in the US aren't seeing that. Maybe for the whole planet, but not for any area one can reasonably interconnect.
[1] http://content.caiso.com/green/renewrpt/DailyRenewablesWatch... [2] https://dataviewer.pjm.com/dataviewer/pages/public/windpower...
Also of note you can smooth out or shift solar by shifting power east-west without involving storage.
And the actual numbers are considerably less optimistic than you report, and that paper was rather optimistic to begin with.
But I agree with the gist of it: storage worries are quite a bit overrated,and oversupply and transmission capacities are underrated. We can fix those easily enough, though
Yes, except for those who live next to the reservoir (or actually, in the would-be reservoir). That could be people, or nature.
Or in the extreme case, consider Lake Erie is next to Lake Ontario. Pumping extra water back up for a few hours a day would have minimal issues as boat bilge water has already cross contaminated them.
PS: The water feature is even down for matinee. http://www.refinery29.com/2016/02/102431/new-york-niagara-fa...
But isn't that what it does? Unless you start to limit (more than before) the waterflow to the falls themselves, which probably would meet resistance from conservationists.
(I understand the Lewiston power plant already does have capability to pump water up.)
And, many places don't have such reservoir capacity at hand. Over here any new reservoir project meets fierece resistance, and it's rather the other way round: nature conservationists want to shut down existing hydroelectric capacity.
It's complex there are few environmental effects from blocking the falls as they are already one way and tend to kill fish that make the trip. However, there is a treaty that set's minimum flow levels and more water is diverted at night to a holding area which is then used for hydro in the day.
https://en.wikipedia.org/wiki/Niagara_Falls_hydroelectric_ge...
Anyway, the area already has plenty of pumped storage it's only by importing a lot of power that you would need to expand. But, at that point you can scale really far with few environmental costs.
TIL
For example, all those people working in the power plant. They're about to be "disrupted" because they have not been willing to evaluate new technology honestly.
Last time I talked to someone still working there, they were making enough per-megawatt on green energy credits that they can run full-bore even if the hourly price for electricity production is negative and make a profit. Not to mention that in the past year, there have been a handful of paper mill closings in the area, so the logging contractors have been scrambling to find anybody that will take their pulpwood production, at any price, and the state government has been mulling legislation to add further subsidies to make sure they take all the wood they can, to keep everyone else in the logging, trucking and other subsidiary industries open.
https://www.iisd.org/gsi/news/us-renewable-energy-tax-credit...
It seems that in order to get the credit, they have to add small amount of diesel? I'll look into that a bit later.
Thanks for sharing this interesting niche of the energy market.
Black Liquor is interesting. Just down the road from my old plant, there is an International Paper mill that has been relying on that loophole for years to keep themselves afloat. All the mill's internal machinery is either steam-driven or runs on the electricity produced by their on-site plant. Lately they've been over-producing power and selling it back on the grid due to these credits, to the point that they have kept paper machines running at paper prices that would otherwise be unsustainable, just to keep a steady supply of black liquor for their power plant.
Even without any breakthroughs, high voltage DC interconnects between between electrical grids would allow us to use wind, solar, and a small amount of natural gas (certainly not megawatt for megawatt!)
And the end result is a system that pays for itself and has cheaper electricity. If we could ever get the stakes holders aligned...
http://arstechnica.com/science/2016/01/making-a-single-us-el...
https://www.youtube.com/watch?v=NvCIhn7_FXI&feature=youtu.be...
There are going to be quite a few electric cars on the road over the next decade, all acting as sinks and sources of power when necessary.
Or by rescheduling load on the grid.