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.
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.
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.
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.
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.
Yea, more control over the panels will help with the overgeneration issue.
But there’s other issues like ramping supply to meet peak demand and general generation during non-solar hours that still have to be addressed.
Each have interesting proposals on how to solve them, but they haven’t been developed to the point that they’re ready to be put onto the grid at a large scale.
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!
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.
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.
It doesn’t matter how much solar you build; without storage you’ve got zero power available at night.
The issue with overbuilding solar is that you drive daytime electricity prices to zero so that everyone is losing money on all these solar plants. Furthermore, base load plants such as nuclear plants also start losing money and they have no ability to shut down during peak hours. So you end up driving the base load plants out of business and they shut down permanently. Now you have even less capacity available at night! This causes nighttime power to become extremely unreliable, potentially leading to rolling blackouts and skyrocketing nighttime energy prices.
Another issue that people rarely discuss is the quality of power on the grid. All the grids in the world operate on 50/60 Hz AC which must be carefully maintained at an accurate frequency and synchronized with the grid. The main base load turbines are the source of this waveform which is carefully monitored and adjusted to remain stable.
Solar panels produce DC power which needs to be converted into AC with an inverter and synchronized with the grid. The problem is that if all the base load turbines are taken off the grid then there is nothing for the solar inverters to synchronize with! Turbines are nice and stable because they’re literally an enormous, massive spinning flywheel. Without them you’ll have an extremely unstable system where all of the solar plants are trying to adjust their frequencies and phases to match each other and the whole thing wanders all over the place.
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.
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.
that work on the scale needed to support large sections of electrical grid
That first link is for a 10MW, 8 hour battery. 10MW is on the smaller end of generators, you’d need quite a few of these to start making an impact. For example, a small gas turbine is like 50MW, a large one is over 250MW.
And you could say “just build a lot of them” but the capacity per unit of area tends to be pretty low for these types of technologies.
Building them where we have ample space is okay. But now this power has to be transmitted, and we are already having a lot of problems with transmission line congestion as-is. The real advantage of energy storage is when it’s done local, no need for transmission lines.
Plus there’s permitting/stability issues as well. These wouldn’t work if the area was prone to earthquakes or other natural events.
I think a more feasible potential technology for the grid are flow batteries.
They work through some kind of ion-exchange. Where they have two liquids, one charged and one not. By running power through a catalyzer, they move charges into one tank. Then you can apply a load across the catalyzer, and remove the charge as power.
I’m by no means an expert, but these are already pretty popular in Japan, and have started to make their way into the US.
Still definitely an expensive technology, but I’m hopeful that scale and investment can drive the cost down.
One of their biggest advantages over other technologies like Li-Ion is that their duration is independent of their capacity. Because the duration is only determined by the size of your tanks and the amount of liquid you have.
Meaning that you can take an existing 50MW, 4 hour plant and upgrade it to an 8 hour plant by doubling the size of the tanks and filling them up with the electrolyte. All without having to upgrade the catalyzer.
Edit: also worth mentioning they don’t have the same supply/environmental/recyclability concerns that lithium batteries do. I believe the electrolyte is relatively inert and does not degrade over time.
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.
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.
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 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.
Yea, more control over the panels will help with the overgeneration issue.
But there’s other issues like ramping supply to meet peak demand and general generation during non-solar hours that still have to be addressed.
Each have interesting proposals on how to solve them, but they haven’t been developed to the point that they’re ready to be put onto the grid at a large scale.
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!
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.
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.
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.
It doesn’t matter how much solar you build; without storage you’ve got zero power available at night.
The issue with overbuilding solar is that you drive daytime electricity prices to zero so that everyone is losing money on all these solar plants. Furthermore, base load plants such as nuclear plants also start losing money and they have no ability to shut down during peak hours. So you end up driving the base load plants out of business and they shut down permanently. Now you have even less capacity available at night! This causes nighttime power to become extremely unreliable, potentially leading to rolling blackouts and skyrocketing nighttime energy prices.
Another issue that people rarely discuss is the quality of power on the grid. All the grids in the world operate on 50/60 Hz AC which must be carefully maintained at an accurate frequency and synchronized with the grid. The main base load turbines are the source of this waveform which is carefully monitored and adjusted to remain stable.
Solar panels produce DC power which needs to be converted into AC with an inverter and synchronized with the grid. The problem is that if all the base load turbines are taken off the grid then there is nothing for the solar inverters to synchronize with! Turbines are nice and stable because they’re literally an enormous, massive spinning flywheel. Without them you’ll have an extremely unstable system where all of the solar plants are trying to adjust their frequencies and phases to match each other and the whole thing wanders all over the place.
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.
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.
https://interestingengineering.com/innovation/two-massive-gravity-batteries-are-nearing-completion-in-the-us-and-china
https://www.bbc.com/news/science-environment-61996520
I hesitate on
That first link is for a 10MW, 8 hour battery. 10MW is on the smaller end of generators, you’d need quite a few of these to start making an impact. For example, a small gas turbine is like 50MW, a large one is over 250MW.
And you could say “just build a lot of them” but the capacity per unit of area tends to be pretty low for these types of technologies.
Building them where we have ample space is okay. But now this power has to be transmitted, and we are already having a lot of problems with transmission line congestion as-is. The real advantage of energy storage is when it’s done local, no need for transmission lines.
Plus there’s permitting/stability issues as well. These wouldn’t work if the area was prone to earthquakes or other natural events.
That’s fair. They’re certainly imperfect, but a large improvement over electrolytic cells for large scale storage.
I think a more feasible potential technology for the grid are flow batteries.
They work through some kind of ion-exchange. Where they have two liquids, one charged and one not. By running power through a catalyzer, they move charges into one tank. Then you can apply a load across the catalyzer, and remove the charge as power.
I’m by no means an expert, but these are already pretty popular in Japan, and have started to make their way into the US.
Still definitely an expensive technology, but I’m hopeful that scale and investment can drive the cost down.
One of their biggest advantages over other technologies like Li-Ion is that their duration is independent of their capacity. Because the duration is only determined by the size of your tanks and the amount of liquid you have.
Meaning that you can take an existing 50MW, 4 hour plant and upgrade it to an 8 hour plant by doubling the size of the tanks and filling them up with the electrolyte. All without having to upgrade the catalyzer.
Edit: also worth mentioning they don’t have the same supply/environmental/recyclability concerns that lithium batteries do. I believe the electrolyte is relatively inert and does not degrade over time.
Thats just not what this post is about. Obviously storing is the way but until then yiu just gotta turn em off