A solar power researcher discusses the “duck curve” he helped discover
vox.com
vox.com
When you curtail the coal plant, though, you still have the fuel. You’re not wasting it.
Paul Denholm
But what fraction of the LCOE [levelized cost of energy] of a mine-mouth coal plant is the fuel? It’s a small fraction. The cost of the plant is the major component of the LCOE, so when I curtail generation from that coal plant, I’m losing the opportunity to recover the cost of investing in that really expensive asset.
I never considered that running a coal plant below capacity is the same as dumping solar panel energy, economically speaking.
Talking about seasonal storage is kind of silly costs are low enough that you can build say 20% more solar and wind than you need on average and they are still cheaper than gas/nuclear/coal. On top of that hydropower is very dispatchable which acts a lot like seasonal energy storage because you are storing months worth of river flow.
Obviously energy intensive businesses like aluminum smelting, chemical production, etc, but also things like refrigeration units running slightly more midday to produce chilled water and then idling until ~10pm, battery backups at datacenters being half way drained and then refilled off-peak, etc.
My intuition is that the power and agricultural water demand roughly match up, both high in the summer.
For levies and fish, you can't just dump or cut off water quickly. Ramping flow up creates turbidity that can harm fish. Cutting it off leaves saturated levies without support and leads to sloughing and failure.
I don't know whether these limits would actually matter for an energy management scenario, just pointing out that there are certainly some limits.
The northwest US for example has an abundance of water. The southwest on the other hand has to manage water of multiple years and has far less slack in the system.
As to flow rates, that's a issue for sudden changes in output over minutes not seasonal shifts in demand. An average flow rate of +/- 10% for a month is a non issue for river ecosystems as long as it's within normal variation, but can represent a lot of stored energy over that month.
Hell. Yes.
Most of the deregulated markets already have a futures market price scheduled in 15 minute intervals that clears 24 hours in advance. Expose end customers to that day-ahead market and we can get all kinds of flexibility.
It is unfortunately true that most residential users will not pay enough attention to either curtailing their own use or -- and I think this is the big one -- shenanigans by the electric utility.
If the result is an effective rate hike, residential users will oppose it. It's not even that hard to get residential users to love it, but it seems no one is interested in solving that problem.
Facing solar panels towards the sun throughout the day, to maintain the angle of incidence at the same as midday (i.e. 0°) flattens and lengthens the demand curve.
This sun-tracking is important, not to maximize power output, but for this effect on the demand curve, reducing storage and grid need.
Not sure how a technology that relies on the availability of titanic quantities of fresh water is going to play out in California, though. :(
The ultimate result is that the moon falls towards the earth a couple micrometers and everything is fine.
A system based mostly around turbines has the inertia of thousands, maybe millions of tons of spinning metal across the entire grid, which buffers enough energy for control systems (for example controlling how much fuel to inject) to respond to sudden demand changes while maintaining stability.
If everything's solid-state solar, following demand is harder.
Following demand is a different function called frequency regulation. Regulating frequency down (curtailing output) is easy for solid-state inverters (including solar), though regulating up (increasing output) is, as you note, more difficult for generation (but very easy for load).
And the peak time (and pricing) is 3 p.m. to 8 p.m. PG&E recommends to "shift usage to the least expensive hours: before 3 p.m. and after 8 p.m. every day".
However, this is, in most scenarios today, more expensive than simply spinning up a combustion turbine to provide power well after sunset.
Other types of tech have much faster adoption cycles due to the lower cost of substitution. For each peak-hour kWh from PV comes at an increased cost of non-peak-hour kWh from non-PV (whether storage or generation).
Lithium ion batteries can only do so much. On a global scale, they are too small to have a meaningful impact.
But unfortunately, the sun disappears for hours. A bigger solution is needed. Pumped hydro works for sure, but even at GW-hr scale (and yes, there are pumped-hydro plants at GW-hr size), its not going to be enough.
Utilities in the US have been changing their rates (tariffs) to decease the cost of energy (kWh), but increase the cost of demand (kW) as a way to (dissuade solar adoption / align cost of service -- depending on your perspective). But within increased demand charges, this permits batteries to offer more value than shifting the time of use of energy.