How Windmills as Wide as Jumbo Jets Are Making Clean Energy Mainstream

Yes, that's precisely the thing I was referring to. Wasn't sure about the correct terminology (not an EE) so I didn't try to make the comment sciency-souding :).

Selling solar back to the grid has one major problem that, fortunately, doesn't plague windmill installations: The Duck Curve [1].

The problem is that peak energy usage now occurs after sunset. So no matter how many solar panels you stack on your home, around 6-7 PM the coal, oil, and gas power plants all have to spin up to their max capacity. Your solar panels are new less likely to _replace_ a coal power plant, although they do change how many hours a day it runs.

Unfortunately for the power companies, running a coal power plant for 3 hours a day costs just about as much as running it for 8 hours a day. This leads to the power companies naturally feeling rather sour about being forced to credit residents for the power they supply to the grid during low-demand hours. Their costs are staying about the same, but now their revenue stream goes down.

In some regions (Utah/Idaho/Colorado is the one I'm aware of) these power companies are now negotiating with governments for lower and lower solar credits for these kinds of residents and they're winning because the abundance of solar power at mid-day is legitimately creating an oversupply, thus making that energy worth less and less.

I see this causing problems for many of my neighbors, who had solar sales reps factoring in energy buy-back rates from 2016 into 10-year loans models to pay for the solar panels. Soon the energy the power companies pay my neighbors is going to offset their panel loans less and less, which may result in a reversal of the economics that led to them buying the panels in the first place.

[1] https://en.wikipedia.org/wiki/Duck_curve

There is always demand. The issue is that sometimes demand exceeds supply. Taking away supply has the same net effect as increasing demand.

EDIT: with the one caveat of transmission capacity, which certainly can be an issue.

When power gets more expensive in the evenings, a lot of heating/cooling/charging loads may shift in time. Also, hvdc grids let you transmit over a couple of timezones.

(And wind does not have the problem the first place, obviously)

That's true when looking at an individual plant, but is not directly relevant when you're looking at the grid as a whole (though it may be an issue when you have transmission limitations), where the problem is that at some point you have a supply of +2X MW, and demand is only X MW, and you need to deal with the X MW of oversupply. If one of the suppliers can then turn off X MW of supply rapidly, that has the same effect as if you add X MW of demand.

At a hydro plant you have multiple options: You can bypass the turbines; you can close the dam, as long as it's not near capacity; if you have a lower reservoir you can close the dam and pump water up to the upper reservoir. All of these help reduce the excess supply, but pumping up does so by increasing demand and reducing supply, and the other two options reduce supply.

You can of course do pumped storage without normally producing electricity too - in places where the only convenient location for a reservoir is not "in line" with a water source with sufficient fall height, you can still pump up to a convenient location, in which case the plant is basically "only" storage.