Is this real or a hoax? California $0.00 export rate

Hedges said:

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.

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."

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CAISO curtailment report

Yes home solar is harder to curtail into the grid. Plenty of utility solar to throttle down when needed.

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).

CaliSunHarvester said:

Can you explain this? My grid delivers 245 to 248V. What would happen if it were 270V? My appliances fry???

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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.

wattmatters said:

So if your grid standard is nominally 240 V, then those two points are 254 V derating will start and 264 V shut down

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I had no idea!

CaliSunHarvester said:

I had no idea!

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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.

kommando said:

There are some country grid codes set in the inverters that limit export based on frequency

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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.

hwy17 said:

If I read this correctly, I agree: You export into negative rates, you should actually pay for it.

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It’ll be the carrot and the stick method for getting more batteries installed which solves some of the problems created by PV integration.

wattmatters said:

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:

CAISO Live Dashboard

View live data for CAISO on Grid Status

www.gridstatus.io

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Presumably this was offsetting natural gas peaker plants that would normally handle the load, so probably decent saving to the utility.

740GLE said:

It’ll be the carrot and the stick method for getting more batteries installed which solves some of the problems created by PV integration.

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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.

wattmatters said:

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.

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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

When system frequency exceeds 60.1Hz, the active power output produced by the Smart Inverter shall be reduced by 50% of real power nameplate rating per hertz (5% of real power nameplate rating reduction per 0.1 hertz)

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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.

olivinelife said:

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

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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.

olivinelife said:

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.

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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:

olivinelife said:

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.

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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.

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.

billvon said:

OhmConnect - pays me $$$ to feed power back to the grid during power shortages. I've made about $1800 in the past four years.

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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?

wattmatters said:

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.

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You are suggesting the tail wags the dog in both physics and politically. Frequency rises because of oversupply, not as an independent variable. If frequency rises too much, then removing supply is absolutely the right thing to do.

You are absolutely right that frequency-watt is not a tactical form of control, whatever that means. From the utility's point of view, they would love to tactically shut off everyone's rooftop PV forever (at least in California) because it's a huge money-loser due to lost revenue from inflated utility rates. As you mentioned, physically they cannot do that on purpose, but secondarily and more importantly, they cannot do that politically either because it would be reneging on existing NEM contracts with individual customers. That is precisely the reason why it's possible for prices to go negative at all. Other players pay the cost for rooftop PVs oversupply.

Anyways, the answer is more battery storage everywhere, and with increasing grid interactivity. Your own linked chart shows this. VPP is still a new concept that needs to be refined more to fit the distributed energy landscape of the future.

olivinelife said:

From the utility's point of view, they would love to tactically shut off everyone's rooftop PV forever (at least in California) because it's a huge money-loser due to lost revenue from inflated utility rates. As you mentioned, physically they cannot do that on purpose, but secondarily and more importantly, they cannot do that politically either because it would be reneging on existing NEM contracts with individual customers.

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If that occurred at a time of peak demand, I think the grid would collapse due to lack of supply.

Which is why I want to form an Organization of Photo Electric Customers, yank our disconnect switches all at 2:30 PM on a hot summers day, then sit down to negotiate how much we must be paid to put our valuable power back on the grid.

Hedges said:

If that occurred at a time of peak demand, I think the grid would collapse due to lack of supply.

Which is why I want to form an Organization of Photo Electric Customers, yank our disconnect switches all at 2:30 PM on a hot summers day, then sit down to negotiate how much we must be paid to put our valuable power back on the grid.

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Following the Enron playbook I see....oh heavenstobetsy all these plants just went down for maintenance at the same time...what are the odds?

Brucey said:

Following the Enron playbook I see....oh heavenstobetsy all these plants just went down for maintenance at the same time...what are the odds?

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A lot has changed since the Wild West that was first few years of de regulation. Thanks California, it put a pause on de regulation by a few years on the east coast.

Lots of markets have capacity supply obligation markets, generators get paid before they are needed, so when they are needed they will be there. The flip side is if they are broke or trip, then they have to caught up the coin.

Again carrot and stick method.

This is why people are starting to move their solar panels to face the sun during peak demand instead of the 1980s concept of max total production.

In this area, peak demand / highest pricing is roughly August 2 pm - 8pm. The later in the day, the better.

Go outside and look at how the sunlight hits your house a few times from 3 pm - 7 pm tonight. That is where the bulk of the panels need to be.

The other time is from 7 am - 10 am.

The rest of the day is not that helpful IMHO.

Look out for #1 (have some panels aimed at Noon or so to supply yourself when the grid is down.)
The AM panels may help the grid, but no financial incentive for that, only do it to help yourself.

Highest pricing used to be Noon - 6:00 PM. Now it is 4:00 - 9:00 PM under NEM 1.0 and I think 2.0, difficult to do much there with orientation.
So you may want to just maximize production. Either backfeed at that time for off-tier credit, or put in a battery for $0.20 higher peak credits.
I think panels aimed due south will earn more credit than aimed to catch sun after 4:00 PM.

NEM 3.0, the only decent credit is going to be something like 6:00 to 8:00 PM, so unless you use it when you make it, battery is the only way.

billvon said:

They do something like that with me. An aggregator - OhmConnect - pays me $$$ to feed power back to the grid during power shortages. I've made about $1800 in the past four years.

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Hey! A fellow member of OhmConnect. I've posted here a couple times. I've made something around $900 a per year the last 3+ years running.

They're really pushing for Texas members to join.

olivinelife said:

Anyways, the answer is more battery storage everywhere, and with increasing grid interactivity. Your own linked chart shows this. VPP is still a new concept that needs to be refined more to fit the distributed energy landscape of the future.

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Agree although I would say it's but one of multiple strategies required.

Which is why I suggest keeping an eye on Australia (esp. Sth Aust). Multiple VPPs in operation. But definitely it's a developing area. VPPs started here in 2016, and now there is something like 500-700 MW under VPP management across Australia. From an engineering perspective they have been shown to work quite well and there has been a fair bit of knowledge gained. As a commercial option it's a bit more challenging to make them attractive to the household.

olivinelife said:

You are absolutely right that frequency-watt is not a tactical form of control, whatever that means.

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Just to be clear - the suggestion was made upthread that the grid operators would be better to use frequency control than voltage as a means to curtail rooftop PV generation as desired.

I'm just pointing out the physical folly of that. Allowing (or causing) the grid frequency to rise as a way to throttle PV generation is not a method which can target just rooftop PV. It impacts everything connected to the entire grid - all loads and generation sources. Grid operators will never use that as a means for strategic or tactical curtailment of rooftop PV. That's akin burning the whole suburb/town down because you found a spider in your bedroom. Yes, if the grid frequency rises out of spec then rooftop PV inverters will (should) throttle/shut down. But that's an emergency response mechanism, not strategic management.

Meanwhile voltage can be managed locally and fairly easily at substation level.

But better again is data control signals to the inverters themselves.

As to political and commercial/contractual considerations, in the end if they are not sorted out then physics takes over.

Overpricing excess exported rooftop PV generation is madness, so that will take some time to wash out of the system. At least here that was realised relatively early on and the last of the high feed in credit rates were abandoned the best part of a decade ago. Some still have them as a legacy arrangement but they will soon pass and in general they are a minority and those that do still have them have relatively small systems.