From a grid stability point, you can’t produce more than is used, else you get higher frequencies and/or voltages until the automatics shut down. It’s already a somewhat frequent occurence in germany for the grid operator to shut down big solar plants during peak hours because they produce way more power than they can dump (because of low demand or the infrastructure limiting transfer to somewhere else)
Negative prices are the grid operator encouraging more demand so it can balance out the increased production.
Spot on! I hoped this comment would be higher! The main problem isn’t corps not making money, but grid stability due to unreliability of renewables.
To be fair, the original tweet is kinda shit to begin with. They’ve unnecessarily assigned monetary value to a purely engineering (physics?) problem.
The original commenter’s (OC’s) point has nothing to do with renewables’ reliability.
It is entirely to do with generation vs demand. Grid operators could ask other generators like coal, nuclear, hydro, etc. plants to curtail so inverter-based renewables can export power, but that’s not likely because those producers can’t ramp generation up and down as easily.
Grid stability is a problem when you have overcrowding of generation without enough demand on given feeders. This is moreso an issue with the utilities anyways and how they plan their transmission and substation upgrades.
Piggybacking on your grid stability point, another issue I don’t see getting addressed here is ramp rate.
If we install enough solar where 100% of our daytime load is served by solar, that’s great. But what about when the solar starts to drop off later in the day?
A/Cs are still running while the sun is setting, the outside air is still hot. People are also getting home from work, and turning on their A/Cs to cool off the house, flipping on their lights, turning on the oven, etc.
Most grids have their peak power usage after solar has completely dropped off.
The issue then becomes: how can we serve that load? And you could say “just turn on some gas-fired units, at least most of the day was 100% renewable.”
But some gas units take literal hours to turn on. And if you’re 100% renewable during the day, you can’t have those gas units already online.
Grid operators have to leave their gas units online, running as low as they can, while the sun is out. So that when the peak hits, they can ramp up their grid to peak output, without any help from solar.
There are definitely some interesting solutions to this problem, energy storage, load shifting, and energy efficiency, but these are still in development.
People expect the lights to turn on when they flip the switch, and wouldn’t be very happy if that wasn’t the case. Grid operators are unable to provide that currently without dispatchable units.
One solution to what you’re describing is to expand the grid. If your grid stretches half the planet, when the East starts to experience night, the West still experiences day and can ship electricity from renewables to the East to make up for their self curtailment. The same goes for wind where if one location on the planet doesn’t experience wind, odds are another location does and the power can be shuffled around.
Another option is to build out more battery storage such that any clipped energy from solar or wind - that is, the energy that can be generated from your solar or wind resource but that can’t be exported because it would overload your inverters or transformers or exceed your PPA agreement with your utility - is stored and can be exported for 2-4 hours as the sun goes down or wind dies out.
Not a lot of renewables sites are colocated with battery storage, but more and more are.
If we install enough solar where 100% of our daytime load is served by solar, that’s great. But what about when the solar starts to drop off later in the day?
Store the surprus of energy from the solar panels and use that as a buffer with batteries or gravity
But some gas units take literal hours to turn on. And if you’re 100% renewable during the day, you can’t have those gas units already online.
Why not? Just time it and start it hours before, wind energy could help in that too
Gravity energy storage doesn’t scale well. I’ve replied to other comments with more detail on this.
There are more feasible energy storage technologies out there, but these are super cutting edge and are not ready for grid-level deployment yet.
The future of grid level energy storage is almost certainly not going to be gravity based. At least not on a large scale.
You can’t have 100% of load be renewable/solar and have gas units online on top of that. That’s over generation. You have to match the supply exactly with the demand. If you mismatch, you destabilize the grid. Undersupply causes blackouts, oversupply melts power lines.
If a unit takes 10 hours to start, solar hours are from 6am to 6pm, and peak load is at 7pm with 0% solar; when do you recommend we start this unit? At the minimum, we’d have to order it on at 7am. Units have to run at a minimum load, let’s say 100MW for this unit. So now you can’t 100% solar from 7am to 6pm, you have to leave 100MW of room for this base loaded unit.
This doesn’t even factor in regulatory requirements like flex, spinning reserve, and other balancing and reliability requirements. Grids are required to have emergency units available at an instant to prevent mass destabilization if parts of the grid fail.
Well I wasn’t expecting to find THE right answer in the comments already. Kudos!
And to everyone reading through this post: If you have questions, need more explanations or want to learn more about the options that we have to “stabilize” a renewable energy system and make it long term viable, just ask!
As someone with a technical background this is the stupidest problem with solar that I don’t get… just turn off the panels in groups until generation is closer to demand… how have engineers not figured that out. And if they have why does this still get written about.
Someone is an idiot. Maybe it’s me?
I’m in solar/BESS, and I mean more and more DER sites are making use of string inverters which break out arrays into greater chunks than with central inverters. With those, you have more granularity of control where you can drop entire blocks/strings at a time to fall to your curtailed export rate.
You might ask yourself though why DERs can’t just ramp inverter outputs up or down to match curtailment automatically across a whole site. You can absolutely do that, but what happens is your solar or wind resource stays high on the DC or low frequency (LF) AC side, respectively, while power frequency AC is low on the other side of the inverters. This is referred to as DC:AC ratio in the biz, and the higher that ratio, the more losses your inverters experience and less efficient they are. This also puts a huge strain on your inverters and can lessen their operational lifetime.
But really, DERs tie into the grid at distribution level and so they don’t fall under the regulations of FERC & NERC (at least in North America). This means that smaller producers don’t have the same requirements for control as do utility-scale players, so the incentive to control these string inverters at that granular level isn’t there. It’s much easier to just trip the main breaker and wait until the utility gives you the go ahead to turn back on.
I suspect that at lot of producers may want to look into greater control capabilities in the future, but this also depends on inverter OEMs too allowing that control.
I’m adjacent to this problem, so I have a little context, but am not an expert at all.
To my knowledge, we don’t have granular control over panels. So we can shut off legs of a plant, but that’s a lot of power to be moving all at once.
Instead, prices are set to encourage commercial customers to intake more power incrementally. This has a smoother result on the grid, less chance of destabilizing.
A customer like a data center could wait to perform defragmentation or a backup or something until the price of power hits a cheap or negative number.
Thanks that’s helpful.
But right…?
Solar plants can be reduced to rationalize supply.
To my understanding. The bigger issue is you can’t as effectively do this with other non-renewables like coal/gas… so this not a solar problem but a problem of legacy power plants.
So stupid. The narrative as well.
But the thing is, you CAN simply turn them off at the press of a button (or an automated script) so its really a complete non issue. As long as big solar installations control systems are accessible by the grid operators, it should be fine.
You can do more with them too actually. You can ramp down the AC power production incrementally to meet curtailment requirements, in theory. When you do that though you subject your inverters to greater strain/losses and less efficiency which shortens your lifetime.
If inverter-based producers in solar, wind, and/or BESS want their sites to last for 30-40 years so that ROI is achieved via operation, then it is in their interest to protect their equipment and operate as much as possible at rated conditions or de-energized conditions.
You might think that it would make sense to have more of a slider control between ON and OFF to save everyone, from producers to grids to consumers, but my guess from being in the industry is that grids don’t really supply incentives for that kind of operation. If they did, maybe you’d see more variable control at utility- and community-scale levels.
If you’re spending billions to build a solar plant that has to turn off all the time during peak hours then you’re wasting your money. That seems like a fundamental issue to me, not a non-issue.
Are there any solar plants that cost a billion dollars each?
Secondly, you want to over build solar, so that you have enough capacity during off peak hours. Grid storage is obviously the better solution, but seems not widely available enough yet.
Ok, but what do you do when you’re short of power at night? Keep in mind to turn on conventional power stations it’s expensive & time consuming. Once they startup they need to stay on for a long while to be efficient & cheap.
The real solution is to store excess power in batteries. Lithium ion is too expensive to scale, Sodium ion batteries are economically & capacity viable AFAIK.
Thats just not what this post is about. Obviously storing is the way but until then yiu just gotta turn em off
I’ve read that gravity batteries and sand batteries are ecologically sound options that work on the scale needed to support large sections of the electrical grid.