DIYrich
Solar Wizard
Hawaii has CA beat on a per household basis. At least CA can dump excess to AZ and beyond (up to WA and Canada). HI has grid instability caused by too much non-firm power.
Is this real or a hoax? California $0.00 export rate
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Hedges
I See Electromagnetic Fields!
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The only thing you can't curtail is rooftop PV. (to be curtailable in the future.)
Of course, probably have to keep a certain percentage of rotating generation on line for stability and regulation.
www.latimes.com
If Arizona curtailed PV, it was probably utility scale plants, because they could get the same power from California, only with cash in addition.
"The number of days that California dumped its unused solar electricity would have been even higher if the state hadn’t ordered some solar plants to reduce production — even as natural gas power plants, which contribute to greenhouse gas emissions, continued generating electricity."
Of course, probably have to keep a certain percentage of rotating generation on line for stability and regulation.
California invested heavily in solar power. Now there's so much that other states are sometimes paid to take it
The state's push forward on both fossil fuel and renewable plants has led to excess power — and energy that goes to waste.
www.latimes.com
If Arizona curtailed PV, it was probably utility scale plants, because they could get the same power from California, only with cash in addition.
"The number of days that California dumped its unused solar electricity would have been even higher if the state hadn’t ordered some solar plants to reduce production — even as natural gas power plants, which contribute to greenhouse gas emissions, continued generating electricity."
wattmatters
Solar Wizard
You can if you allow grid voltage to rise high enough. Crude, indiscriminate as local voltages vary considerably, but it works. Better to have smarter control though.
DIYrich
Solar Wizard
Ul1741 ride through is something like 132-138v on one leg before you are allowed to disconnect.
CaliSunHarvester
Solar Enthusiast
Can you explain this? My grid delivers 245 to 248V. What would happen if it were 270V? My appliances fry???
CAISO curtailment reportThe only thing you can't curtail is rooftop PV. (to be curtailable in the future.)
Of course, probably have to keep a certain percentage of rotating generation on line for stability and regulation.
California invested heavily in solar power. Now there's so much that other states are sometimes paid to take it
The state's push forward on both fossil fuel and renewable plants has led to excess power — and energy that goes to waste.
If Arizona curtailed PV, it was probably utility scale plants, because they could get the same power from California, only with cash in addition.
"The number of days that California dumped its unused solar electricity would have been even higher if the state hadn’t ordered some solar plants to reduce production — even as natural gas power plants, which contribute to greenhouse gas emissions, continued generating electricity."
Yes home solar is harder to curtail into the grid. Plenty of utility solar to throttle down when needed.
Lawrence_SoCal
New Member
My expectation (though it will take a while) is that eventually, like DOCSIS modems, future solar (and wind, etc) residential installs will require some sort of gateway, with customer having control on one side (house), and PoCo having control on export/grid side. That way PoCo could control export (zero, per interconnect agreement, PV curtailment, etc)... basically a 'smarter' smart meter with some standardized way (required) to communicate with home generation system to be able to curtail power output... and that may be a capability of some current smart meters, ?? just not in use yet ??
Today, my simple AC connected system simply watches for grid-power, and turns off panels if grid goes down.
Not hard to see with a hybrid inverter, greater control is available, and simple need to be able to communicate from PoCo Smart Meter to Hybrid Inverter to curtail export (whether partial or all). Seems like with utility smart meters and hybrid inverters, this would be entirely doable. Or with existing virtual power plant type setups? Then over time, as existing solar systems (like mine) age out of NEM, (and presumably new rules /requirements 'enforced' to stay inter-connected, the number of systems not easily curtailable gets smaller..). In my specific case, I have a simple Panel mfr monitoring system (Enphase based) where it would be easy (but not simple) to aggregate such systems, and with right back-end, CalISO /PoCo being in position to order export curtailment from system like mine (lots of security, transparency and other considerations, but all doable without getting that complex).
Today, my simple AC connected system simply watches for grid-power, and turns off panels if grid goes down.
Not hard to see with a hybrid inverter, greater control is available, and simple need to be able to communicate from PoCo Smart Meter to Hybrid Inverter to curtail export (whether partial or all). Seems like with utility smart meters and hybrid inverters, this would be entirely doable. Or with existing virtual power plant type setups? Then over time, as existing solar systems (like mine) age out of NEM, (and presumably new rules /requirements 'enforced' to stay inter-connected, the number of systems not easily curtailable gets smaller..). In my specific case, I have a simple Panel mfr monitoring system (Enphase based) where it would be easy (but not simple) to aggregate such systems, and with right back-end, CalISO /PoCo being in position to order export curtailment from system like mine (lots of security, transparency and other considerations, but all doable without getting that complex).
wattmatters
Solar Wizard
It probably won't need to get quite that high. Check the volt-watt requirements for grid-tied solar PV in California though, I don't have that at my fingertips, but on the high side, I think when voltage exceeds 106% of the standard then the PV inverter's volt-watt mode kicks in and begins to derate the inverter's output. The derating is linear down to zero output once voltage exceeds 110% of the standard. Above that and the inverter likely shuts down until voltages fall back below the 106% mark.
So if your grid standard is nominally 240 V, then those two points are 254 V derating will start and 264 V shut down.
But I'm not certain on the current standards there, so check, others may know.
In my grid (Australia) when the grid feed-in point voltage exceeds 253 V the inverter will begin to throttle production. If it exceeds 258 V for long enough (10-min avg) it shuts down until voltage reduces back down below 253 V.
CaliSunHarvester
Solar Enthusiast
I had no idea!
wattmatters
Solar Wizard
The vast majority wouldn't.
For those interested, watch the development on this stuff in the state of South Australia. They are the world's canary in a solar mine with solar PV meeting close to 1/3rd of the state's electricity demand and VRE (solar + wind) at 75% so for this year.
Yeah it's a small grid relative to CA but the principles of management are the same.
In SA now if you install rooftop PV then it can either be very restricted with a low export power limit (like 1.5 kW) or you are allowed to export up to 10 kW (per phase) provided the inverter has the ability for the grid operator to throttle exports at times of extreme grid stress (very low system demand).
Previously the permitted export limit was much lower, but but by allowing the network operator to have some emergency control on the few days a year they need it, then people get to install much more PV capacity which really makes a difference on cloudy days and Winter.
Up until now (well the option still exists and can still be used), the grid operator can strategically set grid voltages higher in some areas so as to force PV off-line. That's worse than throttling exports, since the latter still allows a home to self consume their own generation rather than having it turned off completely.
It's the way of the future, and I expect other states here will eventually follow suit.
There are some country grid codes set in the inverters that limit export based on frequency, Holland has such a grid code so they can limit household PV export without raising voltage. I have always set my system up to be nil export when grid tied.
wattmatters
Solar Wizard
Pretty much all grid tied inverters have that but changing the grid's frequency is ASTONISHINGLY DIFFICULT and would never be a tactic ussed to throttle grid tied PV. There is MASSIVE inertia in the grid and grid operators work very hard to keep grid frequency within a very narrow band. They do this by having various rapid response mechanisms to keep things in spec, as well as maintaining a minimum level of inertia in the system (be it real or virtual).
Grid frequency only goes out of spec when something large and bad happens, like a major power station blows up, a major transmission line goes down, or a massive industrial load has an unscheduled failure.
It's way way way easier to adjust grid voltage as that can be done at substation level, often without too much effort and/or remotely. Far better of course to have logical control of a system's generation and manage it that way, but voltage can be used if needed.
Inverter frequency control is more of a safety net for grid being out of spec due to a major grid event, or as is the more common use case - it is used by off-grid systems (or systems which kick in when the grid goes down) which form a micro-grid and use frequency control to manage the production from GT inverters.
It’ll be the carrot and the stick method for getting more batteries installed which solves some of the problems created by PV integration.
Brucey
Solar Wizard
Presumably this was offsetting natural gas peaker plants that would normally handle the load, so probably decent saving to the utility.I note in recent days California's grid batteries have been discharging at 6+GW during the peak period and covering 25% or more of the power demand for 60-90 minutes. In those peak periods they were the single largest source of grid electrical energy, that light green blob on the right is battery discharge right through peak period:
View attachment 211437
CA grid battery capacity is expected to nearly double in the next 12 months.
You can view the live and historical data here:
Grid Status - Energy data in sync with the grid
Stay informed on the real-time status of the US Electric Grid with comprehensive monitoring and data.www.gridstatus.io
wattmatters
Solar Wizard
Or use a means to reduce exports, or even production, to zero during such times. My inverter has export control, should that ever be required. But if prices are negative, then turn on discretionary controllable loads (e.g. water heater, EV charging) and get paid for consuming.
olivinelife
New Member
California Rule 21 requires Frequency-watt control as specified in IEEE1547-2018, 6.5.2.7 for both curtailment and grid frequency support. The recommended deadbands are actually even tighter at 59.95Hz to 60.05 Hz
This is a more reliable and safe way of curtailment of distributed energy resources going forward than voltage, which for historical reasons has a very wide acceptable voltage range. In my experience, California grid frequency definitely breaches below 59.95 Hz during the late afternoon/evening ramp which is exactly the problem that batteries are ideal for solving.
The general idea is to incentivize battery storage, at both grid-scale and in the home. In my view the historical problem with grid-tie rooftop PV is that it acts as a unidimensional financial asset with the sole purpose of making money from the homeowner's point of view. Batteries actually make a lot more sense in people's homes and can provide numerous ancillary benefits (backup, grid resilience, load-shifting) beyond just making money.
wattmatters
Solar Wizard
That's for the grid's protection, not used as a tactical curtailment strategy.
Tactical changes to demand and supply are used to adjust the grid's frequency, not the other way round.
Put another way, if you wanted to curtail rooftop PV by employing a tactic of raising the grid's frequency, then you'd have to add more supply (or remove load or both) in order to cause a rise in grid frequency. That makes zero sense if you are attempting to remove supply (i.e. rooftop PV) in the first place.
wattmatters
Solar Wizard
Rooftop PV plays a minor but important element in strategies for reducing carbon emissions, and enables use of an idle asset (rooftop space) to contribute towards that. In that sense it has much wider value than just to the homeowner. It is after all the reason why there are incentives around the world to encourage people to install it. Here in sunny Oz, we are expecting rooftop PV to be a very significant component of our grid's energy supply capacity:
Batteries can definitely be of great assistance. Home batteries generally help with peak shaving, being a preventative measure rather than a responsive one. Rapid response frequency control (and ancillary) services are generally better managed by grid batteries.
The FCAS market is where the big grid batteries here have made most of their money so far, while price arbitrage has the been cream on top. They're taking the place of gas peakers and made those services far more responsive, and cheaper.
Where home batteries can help with FCAS is when they are part of a virtual power plant (VPP). We have a number of those in Australia with many thousands of batteries participating and contributing to FCAS.
The main problem is the offers to join VPPs suck dogs' balls. The benefit is heavily weighted in favour of the VPP operator while the home owner gets little return for allowing someone else to control their battery and degrade their asset. Where I think governments have an opportunity is to tie any home battery incentives with participation in a VPP.
wattmatters
Solar Wizard
Aside from volt-watt, PV inverters should also have Volt-Var management, adjusting the level of reactive power generation as needed, be it leading or trailing as the voltage determines.
Ampster
Renewable Energy Hobbyist
I used to be with OhmConnect, years ago but they only compensated me for dropping load during that time frame. Back then I was not able to control export like I can do know, maybe I should look into it again to offset the fixed charge that is coming this summer. This almost sounds like what Tesla is doing with Powerwalls and Virtual Power Plants? Do you remember when this started?
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