8 ms·

NERC sounds alarm on solar tripping in ‘sobering’ summer reliability report

57 points by bison3 4y ago

imglorp 4y ago
I'm having trouble with the power industry terminology. I /think/ they mean there's going to be more demand, which could overload parts of the distribution grid, causing its overload protections to trip. Is that right? The solar connection is not clear aside from it contributing more power on the grid when it's sunny.
- etimberg 4y ago
  Not exactly. The concern raised in the article is that rooftop solar can disconnect off the grid automatically causing a small problem to be cascade to a larger one. https://news.ycombinator.com/item?id=31463342 https://news.ycombinator.com/item?id=31463342 has a ton of good info on this
- blake1 4y ago
  Solar cells generate DC, but this is converted to AC with power electronics: the inverter is the main one. These are all just very high wattage semiconductors, but like all semiconductors, they can be destroyed by a transient event like a lightning strike, or a high fossil-fuel power plant dropping offline. To prevent the power electronics from being destroyed when this happens, they are protected by safety systems which "trip," and isolate them from the grid. There are loads of designs for grid isolation, but most are big circuit breakers, and break the connection by rotating the conductor out of contact, powered by gravity or a spring. So I think you're basically right, and right to be confused. The solar connection of the risk isn't really clear. But as far as I can tell, they're concerned about a positive feedback loop, where a thermal plant dropping offline will cause a solar plant to trip, which might cause other solar plants to trip. Perhaps solar plants' power electronics are more delicate, and more likely to trip, than thermal plants' switchyard gear. Again, it's not totally clear.
  - parrellel 4y ago
    A lot of the rules for disconnecting solar were written when solar wasn't expected to be a major part of the grid, so the logic has them trip because that was the sane default. That's no longer the sane default and the utilities have been slow walking software and hardware updates to fix it. ...and now that might be a problem.
    - gabereiser 4y ago
      Worse still are areas where laws were enacted that _required_ you to get your solar from your utility vs your roof. Or there's a "minimum service fee" even though you don't consume any energy. In the early days you could "sell" your excess energy back to the grid. Now you can't and worse still, they don't know how to handle the infrastructure they have to meet the ever changing climates of the western United States.
      - benglish11 4y ago
        Where are you where you can’t sell excess electricity back to the grid? You definitely can here in SE Pennsylvania. Amongst the few people I know with solar panels on their roof it’s the most common scenario. Several of them have no battery either so they cannot store excess electricity.
        gabereiser 4y ago
        Net-metering has only just been introduced in many southern states after much lobbying from power companies against it. Here in Florida (where I am now) it’s illegal to disconnect your house from the grid if you have solar. There’s a minimum “service fee” of $60 from FPL even if you only used $10 of energy. In many other states run by a certain political party, they have been making it so your net-metered connections are selling back at wholesale rates instead of retail rates, or limiting just how much you _can_ sell back (sell limits). When I used to work for an energy intelligence company back in 2017 it was worse with legislation across the Midwest and western states that prohibited solar on roofs and required homeowners to pool together for community solar projects (run by the power company) to get their renewable energy. Now, most 47 states have some sort of net-metering at least for wholesale prices but more and more of them are requiring a minimum service fees and making hardships for people to live without them.
- gjvc 4y ago
  > I'm having trouble with the power industry terminology. :-) In the UK, the term "prosumer" is the official term for an electrical system which produces to and consumes power from the supply. (example https://electrical.theiet.org/wiring-matters/years/2019/74-march-2019/latest-developments-in-international-standards-for-prosumers-low-voltage-electrical-installations/ https://electrical.theiet.org/wiring-matters/years/2019/74-m... ) (In the past it was widely taken to mean "a customer who wants to buy very high-quality technical products or equipment", https://dictionary.cambridge.org/dictionary/english/prosumer https://dictionary.cambridge.org/dictionary/english/prosumer )
  - dotancohen 4y ago
    First context: prosumer: Portmanteau of "producer" and "consumer". Second context: prosumer: Portmanteau of "professional" and "consumer".
    - gjvc 4y ago
      i fail to see what your comment adds
      - dotancohen 4y ago
        I too take pride in admitting my failures.
- kkfx 4y ago
  The tricky part is not much "power production" but "keeping the grid at a certain frequency" witch means balanced between consumers and producers. A classic large-enough but not too large grid is sized like that to achieve a somewhat constant load so their generator have to supply a certain amount of power without sudden high or low loads spike. A small personal example, I have a small domestic p.v. system for self-consumption, when my dishwasher start heating water my micro-grid load suddenly spike +~2kW my inverter take time to produce more, like few seconds, so without a grid or a battery my micro-grid will simply collapse because the frequency goes too low. Similarly when water heating phase is ended there is a sudden -~2kW load and the micro-grid frequency skyrocket. Again without a grid or a battery my micro-grid will simply collapse due to a too high frequency. Instead a small sudden load change, like a light that turn on or off, have essentially no impact since such so small amount of power vary the frequency of the micro-grid so little that the solar inverter have no issue to keep anything in place. At a classic grid scale ±2kW are just background noise on the frequency, like for my microgrid the led light turned on and off. However at a classic grid scale with massive p.v. things start to be far less constant, sudden spike for so many microgrids means sudden spikes projected to the main grid causing much more frequency perturbations. Also Sun power tend to peak really fast witch means that a grid with an actual production of let's say 1GW at 10 a.m. this morning around my latitude suffer a sudden drop in demand, witch means a high frequency peak because that when most p.v. systems in sunny days quickly goes from few hundreds W to few thousands W in a very little time. So the grid need to reduce power quickly, let's say a quick perturbation pass varying much the p.v. production, again a load peak for them, a big drop in frequency they need to boost production in very few seconds to keep up the frequency. The alternative is rolling blackouts to cut most perturbation and keep the overall grid up, something that do not touch much those how have a p.v. system with battery storage since actual inverters are fast enough to keep homes powered on most load cases BUT touch all other citizens... grid-connected EVs can help quickly absorbing loads and quickly releasing energy BUT for far such applications are just on paper and I doubt we can allow private EVs to talk with the public grid since any vehicle is a mass of proprietary crapware crap built by countless of private parties, many outside national Govs. control, in unknown health shapes, response time, ... such grid is theoretically possible, but practically probably as unstable as without such system, with many smaller rolling blackouts and much higher risks of large scale ones... Long story short: - with climate change we know we have to adapt and adapt means change, changes we can't much design up front due to too many variables, witch means we can't build large/complex systems because they solve a PRESENT issue, taking years to be built, and we do not know if such issue will be solved in the same way once we finished such large systems. - the ideas some from Green New Deal push is: we need to cut such complexity. Witch means making autonomous homes who can be powered locally without a grid, smaller cities with their own local small networks etc instead of nation-wide systems. The very same happen for transportation networks where we start preferring small/medium water and air born systems because we can re-organize them fast instead of rails and roads that take decades to be build and changed. - the issue here is that PERHAPS we can do so, but very unlikely for anyone, probably only of less than a third of the whole humanity and of course those who are excluded for a reason or another would not be happy of that, and not "being happy" means unrest, revolutions, violence, instability etc that beside the carnage and suffering also impede to build pretty anything for anyone. Energy grids operators are just some of the party who start understanding the amplitude of such issue and start blowing all whistle they have alerting: "we can't do that, we do not know alternatives to put on the table". Probably the sole viable alternative we have is PUBLIC only nuclear waiting for tech progress, but so far build such massive nuclear move takes decades.
londons_explore 4y ago
> But the biggest long-term risk may be the unexpected tripping of solar resources during grid disturbances, This is entirely the electricity grids own doing. They told everyone who wanted solar that they must use inverters that are super safe and self disconnect if anything unexpected happens. The regulations were written super tight, with frequency limits, harmonic limits, reactive power limits, rate of change of frequency limits, residual current limits, DC injection limits and vector shift detection requirements, presumably because rulemakers were hoping that having a massive thick rulebook would make rooftop solar too expensive. Unfortunately for them, all the complexity is pushed to software, and when that's written once it can be deployed lots almost free. Fast forward 10 years, and this stuff is widely deployed, meeting all the very strict criteria. Except the grid only stays within those strict limits during the good times. When the grid is stressed, for example low frequency due to insufficient generation, it will go outside the frequency limit, and all rooftop solar generation statewide will disconnect all at once. And now the grid has lost gigawatts of solar production, making a minor incident far far worse. The end result is a cascading failure and within a matter of seconds half the state has a blackout. Smart rulemakers back in the 2010's would have dropped islanding protection, and vector shift protection (they actively destabilise the network). They would also remove underfrequency protection (again - destabilises the network) and slacken substantially undervoltage protection. The only protections important to leave in are rate of change of frequency (upwards only), overfrequency, and overvoltage. What's ironic is there is a more sensible requirement they could have required to make rooftop solar cost more and add substantially to grid stability. They could have required solar systems have a load line equivalent to coal. That pretty much means if the grid frequency decreases, the solar systems must output more power. But solar can't output more power than the sun provides. So in turn, to meet this requirement all solar systems would have to be constantly throwing away say 10% of capacity, so that it could be delivered if and only if the frequency suddenly dropped.
- aaaaaaaaaaab 4y ago
  So noone was bothered to run a simulation to see the second-order effects of their regulations on the grid?
basicplus2 4y ago
This is what happens when you have insufficient or no spinning reserve
- Animats 4y ago
  The Economist had an article on in the May 7th issue with a beautiful picture of inertia storage being delivered.[1] [1] https://www.economist.com/science-and-technology/green-power-needs-more-than-just-solar-panels-and-wind-turbines/21809104 https://www.economist.com/science-and-technology/green-power...
csours 4y ago
If you expect your solar panels to power your house when the grid goes down, make sure you check that. They most likely will not, unless you've added a battery and switches.
- nichohel 4y ago
  And an inverter!
  - amluto 4y ago
    The battery is largely optional. The critical bits are the switch, aka “microgrid interconnection device”, and the inverter’s ability to make a decent sine wave without grid assistance.
    - rcxdude 4y ago
      Only kind of. Without a battery your power will go out every time a cloud covers the sun, unless you have a hugely oversized array.
ars 4y ago
Why is solar thermal so rare?
- ip26 4y ago
  Because photovoltaic got so good & cheap, with no moving parts. In most locales it’s now more cost effective to heat your water with photovoltaic panels & an electric water heater.
  - hn_go_brrrrr 4y ago
    More reading on this: https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead https://www.greenbuildingadvisor.com/article/solar-thermal-i...
  - zeckalpha 4y ago
    Specifically, a heat pump water heater.
    - xxpor 4y ago
      That usually is true if your electricity is generated by natural gas too and you're comparing it against a gas HWH Rough math is NG -> Electricty is 50% efficient thermally. A heat pump can have a COP of 4.2. 100 * .5 * 4.2 = 210% efficient, thermally A hot water heater powered directly by gas is ~100% efficient thermally.
      - kkfx 4y ago
        Personally I do not care about efficiency: I can't sell energy I produce so the point is just heating the water and the load profile of a classic resistance and the load needs of my houses match normally to heat without the heat-pump (witch have a far limited life respect of a classic resistence)... I use the heat pump mode only when there is little solar for few days where there is not enough overall energy production, otherwise being able to produce 120-130% of the overall consumption (of course ONLY when the Sun shine, so NOT independent as some sell just playing with absolute numbers) why care about efficiency? I can't use the extra energy anyway...
deleted 4y ago
[deleted]
etaioinshrdlu 4y ago
This sounds like what utility scale batteries should solve, stabilizing the grid frequency for short periods of time.

57 points by bison3 4y ago

I'm having trouble with the power industry terminology. I /think/ they mean there's going to be more demand, which could overload parts of the distribution grid, causing its overload protections to trip. Is that right? The solar connection is not clear aside from it contributing more power on the grid when it's sunny.

etimberg 4y ago
Not exactly. The concern raised in the article is that rooftop solar can disconnect off the grid automatically causing a small problem to be cascade to a larger one. https://news.ycombinator.com/item?id=31463342 https://news.ycombinator.com/item?id=31463342 has a ton of good info on this
blake1 4y ago
Solar cells generate DC, but this is converted to AC with power electronics: the inverter is the main one. These are all just very high wattage semiconductors, but like all semiconductors, they can be destroyed by a transient event like a lightning strike, or a high fossil-fuel power plant dropping offline. To prevent the power electronics from being destroyed when this happens, they are protected by safety systems which "trip," and isolate them from the grid. There are loads of designs for grid isolation, but most are big circuit breakers, and break the connection by rotating the conductor out of contact, powered by gravity or a spring. So I think you're basically right, and right to be confused. The solar connection of the risk isn't really clear. But as far as I can tell, they're concerned about a positive feedback loop, where a thermal plant dropping offline will cause a solar plant to trip, which might cause other solar plants to trip. Perhaps solar plants' power electronics are more delicate, and more likely to trip, than thermal plants' switchyard gear. Again, it's not totally clear.
- parrellel 4y ago
  A lot of the rules for disconnecting solar were written when solar wasn't expected to be a major part of the grid, so the logic has them trip because that was the sane default. That's no longer the sane default and the utilities have been slow walking software and hardware updates to fix it. ...and now that might be a problem.
  - gabereiser 4y ago
    Worse still are areas where laws were enacted that _required_ you to get your solar from your utility vs your roof. Or there's a "minimum service fee" even though you don't consume any energy. In the early days you could "sell" your excess energy back to the grid. Now you can't and worse still, they don't know how to handle the infrastructure they have to meet the ever changing climates of the western United States.
    - benglish11 4y ago
      Where are you where you can’t sell excess electricity back to the grid? You definitely can here in SE Pennsylvania. Amongst the few people I know with solar panels on their roof it’s the most common scenario. Several of them have no battery either so they cannot store excess electricity.
      - gabereiser 4y ago
        Net-metering has only just been introduced in many southern states after much lobbying from power companies against it. Here in Florida (where I am now) it’s illegal to disconnect your house from the grid if you have solar. There’s a minimum “service fee” of $60 from FPL even if you only used $10 of energy. In many other states run by a certain political party, they have been making it so your net-metered connections are selling back at wholesale rates instead of retail rates, or limiting just how much you _can_ sell back (sell limits). When I used to work for an energy intelligence company back in 2017 it was worse with legislation across the Midwest and western states that prohibited solar on roofs and required homeowners to pool together for community solar projects (run by the power company) to get their renewable energy. Now, most 47 states have some sort of net-metering at least for wholesale prices but more and more of them are requiring a minimum service fees and making hardships for people to live without them.
gjvc 4y ago
> I'm having trouble with the power industry terminology. :-) In the UK, the term "prosumer" is the official term for an electrical system which produces to and consumes power from the supply. (example https://electrical.theiet.org/wiring-matters/years/2019/74-march-2019/latest-developments-in-international-standards-for-prosumers-low-voltage-electrical-installations/ https://electrical.theiet.org/wiring-matters/years/2019/74-m... ) (In the past it was widely taken to mean "a customer who wants to buy very high-quality technical products or equipment", https://dictionary.cambridge.org/dictionary/english/prosumer https://dictionary.cambridge.org/dictionary/english/prosumer )
- dotancohen 4y ago
  First context: prosumer: Portmanteau of "producer" and "consumer". Second context: prosumer: Portmanteau of "professional" and "consumer".
  - gjvc 4y ago
    i fail to see what your comment adds
    - dotancohen 4y ago
      I too take pride in admitting my failures.
kkfx 4y ago
The tricky part is not much "power production" but "keeping the grid at a certain frequency" witch means balanced between consumers and producers. A classic large-enough but not too large grid is sized like that to achieve a somewhat constant load so their generator have to supply a certain amount of power without sudden high or low loads spike. A small personal example, I have a small domestic p.v. system for self-consumption, when my dishwasher start heating water my micro-grid load suddenly spike +~2kW my inverter take time to produce more, like few seconds, so without a grid or a battery my micro-grid will simply collapse because the frequency goes too low. Similarly when water heating phase is ended there is a sudden -~2kW load and the micro-grid frequency skyrocket. Again without a grid or a battery my micro-grid will simply collapse due to a too high frequency. Instead a small sudden load change, like a light that turn on or off, have essentially no impact since such so small amount of power vary the frequency of the micro-grid so little that the solar inverter have no issue to keep anything in place. At a classic grid scale ±2kW are just background noise on the frequency, like for my microgrid the led light turned on and off. However at a classic grid scale with massive p.v. things start to be far less constant, sudden spike for so many microgrids means sudden spikes projected to the main grid causing much more frequency perturbations. Also Sun power tend to peak really fast witch means that a grid with an actual production of let's say 1GW at 10 a.m. this morning around my latitude suffer a sudden drop in demand, witch means a high frequency peak because that when most p.v. systems in sunny days quickly goes from few hundreds W to few thousands W in a very little time. So the grid need to reduce power quickly, let's say a quick perturbation pass varying much the p.v. production, again a load peak for them, a big drop in frequency they need to boost production in very few seconds to keep up the frequency. The alternative is rolling blackouts to cut most perturbation and keep the overall grid up, something that do not touch much those how have a p.v. system with battery storage since actual inverters are fast enough to keep homes powered on most load cases BUT touch all other citizens... grid-connected EVs can help quickly absorbing loads and quickly releasing energy BUT for far such applications are just on paper and I doubt we can allow private EVs to talk with the public grid since any vehicle is a mass of proprietary crapware crap built by countless of private parties, many outside national Govs. control, in unknown health shapes, response time, ... such grid is theoretically possible, but practically probably as unstable as without such system, with many smaller rolling blackouts and much higher risks of large scale ones... Long story short: - with climate change we know we have to adapt and adapt means change, changes we can't much design up front due to too many variables, witch means we can't build large/complex systems because they solve a PRESENT issue, taking years to be built, and we do not know if such issue will be solved in the same way once we finished such large systems. - the ideas some from Green New Deal push is: we need to cut such complexity. Witch means making autonomous homes who can be powered locally without a grid, smaller cities with their own local small networks etc instead of nation-wide systems. The very same happen for transportation networks where we start preferring small/medium water and air born systems because we can re-organize them fast instead of rails and roads that take decades to be build and changed. - the issue here is that PERHAPS we can do so, but very unlikely for anyone, probably only of less than a third of the whole humanity and of course those who are excluded for a reason or another would not be happy of that, and not "being happy" means unrest, revolutions, violence, instability etc that beside the carnage and suffering also impede to build pretty anything for anyone. Energy grids operators are just some of the party who start understanding the amplitude of such issue and start blowing all whistle they have alerting: "we can't do that, we do not know alternatives to put on the table". Probably the sole viable alternative we have is PUBLIC only nuclear waiting for tech progress, but so far build such massive nuclear move takes decades.

londons_explore 4y ago

> But the biggest long-term risk may be the unexpected tripping of solar resources during grid disturbances, This is entirely the electricity grids own doing. They told everyone who wanted solar that they must use inverters that are super safe and self disconnect if anything unexpected happens. The regulations were written super tight, with frequency limits, harmonic limits, reactive power limits, rate of change of frequency limits, residual current limits, DC injection limits and vector shift detection requirements, presumably because rulemakers were hoping that having a massive thick rulebook would make rooftop solar too expensive. Unfortunately for them, all the complexity is pushed to software, and when that's written once it can be deployed lots almost free. Fast forward 10 years, and this stuff is widely deployed, meeting all the very strict criteria. Except the grid only stays within those strict limits during the good times. When the grid is stressed, for example low frequency due to insufficient generation, it will go outside the frequency limit, and all rooftop solar generation statewide will disconnect all at once. And now the grid has lost gigawatts of solar production, making a minor incident far far worse. The end result is a cascading failure and within a matter of seconds half the state has a blackout. Smart rulemakers back in the 2010's would have dropped islanding protection, and vector shift protection (they actively destabilise the network). They would also remove underfrequency protection (again - destabilises the network) and slacken substantially undervoltage protection. The only protections important to leave in are rate of change of frequency (upwards only), overfrequency, and overvoltage. What's ironic is there is a more sensible requirement they could have required to make rooftop solar cost more and add substantially to grid stability. They could have required solar systems have a load line equivalent to coal. That pretty much means if the grid frequency decreases, the solar systems must output more power. But solar can't output more power than the sun provides. So in turn, to meet this requirement all solar systems would have to be constantly throwing away say 10% of capacity, so that it could be delivered if and only if the frequency suddenly dropped.

aaaaaaaaaaab 4y ago
So noone was bothered to run a simulation to see the second-order effects of their regulations on the grid?

basicplus2 4y ago

This is what happens when you have insufficient or no spinning reserve

Animats 4y ago
The Economist had an article on in the May 7th issue with a beautiful picture of inertia storage being delivered.[1] [1] https://www.economist.com/science-and-technology/green-power-needs-more-than-just-solar-panels-and-wind-turbines/21809104 https://www.economist.com/science-and-technology/green-power...

csours 4y ago

If you expect your solar panels to power your house when the grid goes down, make sure you check that. They most likely will not, unless you've added a battery and switches.

nichohel 4y ago
And an inverter!
- amluto 4y ago
  The battery is largely optional. The critical bits are the switch, aka “microgrid interconnection device”, and the inverter’s ability to make a decent sine wave without grid assistance.
  - rcxdude 4y ago
    Only kind of. Without a battery your power will go out every time a cloud covers the sun, unless you have a hugely oversized array.

ars 4y ago

Why is solar thermal so rare?

ip26 4y ago
Because photovoltaic got so good & cheap, with no moving parts. In most locales it’s now more cost effective to heat your water with photovoltaic panels & an electric water heater.
- hn_go_brrrrr 4y ago
  More reading on this: https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead https://www.greenbuildingadvisor.com/article/solar-thermal-i...
- zeckalpha 4y ago
  Specifically, a heat pump water heater.
  - xxpor 4y ago
    That usually is true if your electricity is generated by natural gas too and you're comparing it against a gas HWH Rough math is NG -> Electricty is 50% efficient thermally. A heat pump can have a COP of 4.2. 100 * .5 * 4.2 = 210% efficient, thermally A hot water heater powered directly by gas is ~100% efficient thermally.
    - kkfx 4y ago
      Personally I do not care about efficiency: I can't sell energy I produce so the point is just heating the water and the load profile of a classic resistance and the load needs of my houses match normally to heat without the heat-pump (witch have a far limited life respect of a classic resistence)... I use the heat pump mode only when there is little solar for few days where there is not enough overall energy production, otherwise being able to produce 120-130% of the overall consumption (of course ONLY when the Sun shine, so NOT independent as some sell just playing with absolute numbers) why care about efficiency? I can't use the extra energy anyway...

deleted 4y ago

[deleted]

etaioinshrdlu 4y ago

This sounds like what utility scale batteries should solve, stabilizing the grid frequency for short periods of time.