Solar Upgrade AGAIN

[Someone]

... p.s. "net metering" that is 1:1 time shifting is broken, it doesn't price storage. For all the free market bluster of the US they sure like to add bizzare bureaucratic distortions to a free market (electricity, corn, steel, etc).

Time shifting doesn't require storage, it requires the utility to increase or curtail other sources as needed to accommodate a 'priority' producer like solar.  Storage came later.

Depends how you define storage Fossil plants inherently have storage as does hydro, often called "dispatchable" generation. If they arent running and are sitting idle there is still a cost for storing that energy (particularity in lost operating profit!). 1:1 time shifting is a very big distortion on the market that would only make sense if all the generators were roughly equivalent in costs/characteristics, a fossil plant costed on operating12-18 hours per day delivers more expensive power per unit when operated for shorter hours. The approximation works ok when solar is a small % of the total generation capacity but those days are long gone (in the US and Australia). So the US will have to move away from 1:1 time shifting or accept that its a huge enforced subsidy for solar operators.

Just as a fixed rate consumer feed in/selling price shows its limitations/bluntness when solar is pushing past 30-50% of the generation during the day, with no accounting for the difference in market pricing on sunny or very cloudy days. Such schemes wont last as renewable sources increase in share of overall generation.

[bdunham7]

Storage = the electricity going out was put in storage by electricity going in, such as pumped hydro, battery, etc.  Dispatchable is a relative term, ranging from nuclear (not very dispatchable) to aero-based gas turbine (very).  Wind and solar can be curtailed easily enough to make them dispatchable, but that has typically been done less because of the cost recovery and greenwashing issues.

Just as a fixed rate consumer feed in/selling price shows its limitations/bluntness when solar is pushing past 30-50% of the generation during the day, with no accounting for the difference in market pricing on sunny or very cloudy days. Such schemes wont last as renewable sources increase in share of overall generation.

That has already happened here.  https://www.caiso.com/documents/flexibleresourceshelprenewables_fastfacts.pdf   California has passed the point where the grid can no longer simply absorb the maximum available production of solar power.  New installations don't get the same terms as older ones did because without storage (as defined above) the grid is pretty saturated with solar.  Also, electricity rates are now pretty high at peak times so the big thing now is battery systems that can almost entirely take you off grid, or completely if the situation warrants it.

[Someone]

Storage = the electricity going out was put in storage by electricity going in, such as pumped hydro, battery, etc.  Dispatchable is a relative term, ranging from nuclear (not very dispatchable) to aero-based gas turbine (very).  Wind and solar can be curtailed easily enough to make them dispatchable, but that has typically been done less because of the cost recovery and greenwashing issues.

You said time shifting doesnt require storage. Which is plainly incorrect unless the grid is so wildly over provisioned that energy is always in excess. The economics of 1:1 time shifting are a huge subsidy to those people using it, they get a utility (storage) for no cost.

[bdunham7]

You said time shifting doesnt require storage. Which is plainly incorrect unless the grid is so wildly over provisioned that energy is always in excess. The economics of 1:1 time shifting are a huge subsidy to those people using it, they get a utility (storage) for no cost.

I agree that 1:1 time shifting is apparent storage to the user, but it can be and is (or was) accomplished without using any storage (meaning electricity to storage to electricity).  If you call the fuel tank of a generator 'storage', well....  And, in fact, the grid here is overprovisioned in that manner, but even that isn't a huge issue if they can predict their needs accurately enough.  As far as it being a subsidy to the user, yes it was and quite deliberately, as I stated, for the express purpose of subsidizing solar power.  However, before things got saturated with solar, my system was actually helping the grid because it provided a bit of power right when the utilities were struggling the most to provide it and my neighbors were buying that electricity as I produced it and probably paying even more for it than I was getting.  Now they have plenty.

To make matters even a bit more interesting, since I would typically generate during the day when rates were high and then use at night when they were low, I was getting better than 1:1 time shifting, almost 1:3.  I could generate a surplus (exported) kWh in the day and use 3kWh at night and my net bill would be zero.  That party is mostly over, they now have the weekdays as off-peak until 4PM.

[ejeffrey]

  However, before things got saturated with solar, my system was actually helping the grid because it provided a bit of power right when the utilities were struggling the most to provide it and my neighbors were buying that electricity as I produced it and probably paying even more for it than I was getting.  Now they have plenty.

Another factor especially in California is that the distribution infrastructure is also oversubscribed.  Even 12-2pm when there is an overall energy surplus, in many places it's actually still helpful for you to produce electricity on your rooftop to supply your neighbor's AC to reduce the demand on regional distribution lines trying to keep up with everyone's AC.

[bdunham7]

Another factor especially in California is that the distribution infrastructure is also oversubscribed.  Even 12-2pm when there is an overall energy surplus, in many places it's actually still helpful for you to produce electricity on your rooftop to supply your neighbor's AC to reduce the demand on regional distribution lines trying to keep up with everyone's AC.

Yes, but they won't pay me for that, just the super-off-peak minimum rate.  I end up selling back power anyway unless I'm charging my EV, but now they are getting the better deal.  On the bright side it is a lot cheaper now to run the AC during the day until 4PM.

[EEVblog]

UNLESS you have a battery system and then the current doesn't come for "free" any more.

Is that true 1:1 or do you mean it as a generalization? It is my understanding that you don't have inherent kWh loss of a pack due to the reactive current, but I2R losses just like in normal AC distribution networks. This is assuming you have a system where the pack has a separate inverter that's grid tied of course. Like, your 280VA won't cause a 280Wh loss on the pack, but would me substantially lower (maybe in order of 10% of the VARs?), and depends on the round trip efficiency of the inverter/pack combo and wiring I2R losses etc..

Edit: I think I made a mistake, the issue must appear only if you're islanded, and the same stuff about it being less than 1:1 kWh:VAR applies.

Yes, after thinking about it I think this the case too. Enphase have also confirmed this.

[EEVblog]

Oh, the other problem with the Enphase microinveretsr is the standby power, it's massive!
They only claim a few watts, but that's real power, apparent power sucks. 280VA for my 14 microinveretrs.
You don't pay for that of course, UNLESS you have a battery system and then the current doesn't come for "free" any more.

That was actually one of the first things I noticed with my system after installation, but eventually I realized that not only don't you pay for it, but since it is essentially capacitance directly across the line it actually serves as a power factor correction since the load on the utility tends strongly toward lagging current.  A battery system would only have an issue (maybe) if it were off-grid and then only overnight with very small loads with no inductive motors.

Yep, 3 x 330nF caps per micro inverter.

[EEVblog]

Reactive power is also much more significant when it accompanies peak real power.  Your entire production / distribution system needs to be sized for peak apparent power and sees the highest losses when operating at peak power.  Idle nighttime reactive power isn't a big deal.

Yes, not a problem in terms of cable capacity because the solar will be on it's own radial, not carry any load current when the inverters are off at night.

[EEVblog]

Dave's video conclusion is wrong/misleading: a battery inverter system would certainly not need to consumer 240 W of battery power to supply that load.  It will take some power, but at a rough guess it will be on the order of the inverter inefficiency * load.  For a 95% efficient inverter it would only be ~12W.  Maybe twice that because you probably loose the conversion losses both directions: forward and reflected power.  It's not nothing but it's equivalent to a few minutes of daytime power production.  If you have any significant inductive load like a ventilation fan that is cooling your house overnight with outside air this will be lost in the noise.

Power factor is an issue when you have to distribute over a long distances picking up big distribution and transformer losses.  Going from your roof to your garage isn't a big deal.

If Dave gets a battery system this will be easy to verify: put a current clamp around the DC battery lead, then measure the draw in the middle of the night.  Use the manual AC disconnect on the solar feed and see how much the battery draw changes with and without the inverters.  I'd certainly be interested to see my handwaving guess verified.

Correct.  battery/inverter swithcing losses + I2R losses for the solar install radial.
And only a problem if you have an isolated battery system. Enphase have confirmed that a battery system would not deliver the apparent current if it's grid connected.

[bdunham7]

Enphase have confirmed that a battery system would not deliver the apparent current if it's grid connected.

Which is interesting because here, with the gradual introduction of Rule 21, solar inverters are required to supply reactive power as needed.  This means they are a sort of active-VAR and assume some of the same burden that the utility generators have.  The capacitance in the standby mode could be advertised as a passive VAR feature of dormant inverters, which like solar itself would be a net positive until there are too many of them.  My area is sprinkled with switchable capacitor banks on the utility poles so I assume there is still a great need for VAR correction.

Scroll down to the Dynamic Voltage/VAR section and you'll see that new inverters here are required to provide up to 62% of their output as reactive power, depending on conditions.

https://www.openintl.com/california-rule-21-interconnection/

[ejeffrey]

Enphase have confirmed that a battery system would not deliver the apparent current if it's grid connected.

Which is interesting because here, with the gradual introduction of Rule 21, solar inverters are required to supply reactive power as needed.  This means they are a sort of active-VAR and assume some of the same burden that the utility generators have.  The capacitance in the standby mode could be advertised as a passive VAR feature of dormant inverters, which like solar itself would be a net positive until there are too many of them.  My area is sprinkled with switchable capacitor banks on the utility poles so I assume there is still a great need for VAR correction.

Scroll down to the Dynamic Voltage/VAR section and you'll see that new inverters here are required to provide up to 62% of their output as reactive power, depending on conditions.

https://www.openintl.com/california-rule-21-interconnection/

Interesting. I don't quite get how the "absorbing / supplying reactive power to deal with over/undervoltage" works, but this seems like an obviously necessary and helpful step.  It also includes frequency stabilization, transient ridethrough without triggering islanding, and a bunch of other stuff.

Of course the utilities still want to reduce the feed in price down to next to nothing even during demand imbalance and also charge you for electricity you generate and consume locally, even while mandating that solar installations help improve grid stability...

[bdunham7]

Of course the utilities still want to reduce the feed in price down to next to nothing even during demand imbalance and also charge you for electricity you generate and consume locally, even while mandating that solar installations help improve grid stability...

Fortunately that rather extreme position on the part of the utilities hasn't been accepted in California, but other states have adopted plans like that.  And if you try to go off-grid, they'll do things ranging from denying your building permit to taking your kids away. 

I think the first-stage simple implementation simply assumes that current is lagging during sags and supplying some reactive current to the local grid will reduce the total distribution inflow to that section of the grid, which reduces voltage drop in that leg of the distribution network.  Or something like that.  I'd like to see the detailed explanation.

[David Hess]

Fortunately that rather extreme position on the part of the utilities hasn't been accepted in California, but other states have adopted plans like that.  And if you try to go off-grid, they'll do things ranging from denying your building permit to taking your kids away.

Usually the law requires that the house have a power grid hookup to be considered habitable.

I think the first-stage simple implementation simply assumes that current is lagging during sags and supplying some reactive current to the local grid will reduce the total distribution inflow to that section of the grid, which reduces voltage drop in that leg of the distribution network.  Or something like that.  I'd like to see the detailed explanation.

That would work for correcting power factor at the power meter where it can be measured.  If it was used to correct the power factor of a remote load, then it would cause poor power factor on the line to that point.

Online UPSes which have power factor correction do this for their own loads.  You can plug a 0.6 power factor load into an online UPS which has power factor correction, and the line side will see a 1.0 power factor when powering that load.

[Geoff-AU]

Any modern DC string inverter with Global MPPT (Fronius Dynamic Peak Manager, SMA Shadefix, etc) will give you more energy over the long run than microinverters - due to the distributed inefficiency of the microinverters.  Even in light to moderate shading and dealing with a hard shadow or two.

The only time microinverters "win" is if you have shading so heavy that it's not economical to put a panel in that location anyway.

Has been proven many times in many tests that microinverters are simply an example of very effective FUD marketing.

But they do make it easy to make ad-hoc expansions, in the case where SWMBO has firm opinions about the roof which despite being firm, are subject to change.  Luckily I managed to put all 13kW of panels up in one go, so I went with DC strings.

[NiHaoMike]

Time shifting doesn't require storage, it requires the utility to increase or curtail other sources as needed to accommodate a 'priority' producer like solar. 

Or adjust demand to try to match production. Ohmconnect is one program that tries to do it. Adding thermal storage would be far cheaper than batteries and would do a lot in any area that has significant HVAC use.

Of course the utilities still want to reduce the feed in price down to next to nothing even during demand imbalance and also charge you for electricity you generate and consume locally, even while mandating that solar installations help improve grid stability...

At that point, if selling back is not going to net a positive, I would just put in a DIY zero export system.

Usually the law requires that the house have a power grid hookup to be considered habitable.

What would the Amish do? Even though some have given in and decided to use some modern technology, I'd imagine there are still some who are sticking with how they did it in the old days.

[EEVblog]

Any modern DC string inverter with Global MPPT (Fronius Dynamic Peak Manager, SMA Shadefix, etc) will give you more energy over the long run than microinverters - due to the distributed inefficiency of the microinverters.  Even in light to moderate shading and dealing with a hard shadow or two.
The only time microinverters "win" is if you have shading so heavy that it's not economical to put a panel in that location anyway.
Has been proven many times in many tests that microinverters are simply an example of very effective FUD marketing.
But they do make it easy to make ad-hoc expansions, in the case where SWMBO has firm opinions about the roof which despite being firm, are subject to change.  Luckily I managed to put all 13kW of panels up in one go, so I went with DC strings.

That's the thing with my situation. I already have 14 x Enphase microinverters and the Envoy system.
If I want to consolidate into one system then I either have to expand the Ephase system or scrap it entirely and move back to string inverters. Or expand with another string inverter, and stick with having two separate systems.
 
Also, DC string fires a real thing, so potential safety advantages there with the AC micro inverters.
Also, if one panel fails for whatever reason is doesn't take down the string. Plus from a data point of view you can get individual graphs from each panels which is prety cool. Not essential of course, but cool.

As you can see here, I am getting shading in winter in the morning where I want the new system to go. I summer time there is another tree you see on the left there that will likely also shade it.

[EEVblog]

Enphase have confirmed that a battery system would not deliver the apparent current if it's grid connected.

Which is interesting because here, with the gradual introduction of Rule 21, solar inverters are required to supply reactive power as needed.  This means they are a sort of active-VAR and assume some of the same burden that the utility generators have.  The capacitance in the standby mode could be advertised as a passive VAR feature of dormant inverters, which like solar itself would be a net positive until there are too many of them.  My area is sprinkled with switchable capacitor banks on the utility poles so I assume there is still a great need for VAR correction.

Scroll down to the Dynamic Voltage/VAR section and you'll see that new inverters here are required to provide up to 62% of their output as reactive power, depending on conditions.

https://www.openintl.com/california-rule-21-interconnection/

Interesting. The Enphase inveretrs do indeed have an active VAR, but I'm not if that's continuously variable or fixed at install, but it can be varied +/- 0.2 I think.

[David Hess]

Usually the law requires that the house have a power grid hookup to be considered habitable.

What would the Amish do? Even though some have given in and decided to use some modern technology, I'd imagine there are still some who are sticking with how they did it in the old days.

The Amish would have lived and built their house where it was not a requirement.  Usually it comes up when someone wants to convert to solar power with a battery system and disconnect entirely from the grid.  With a suitable investment it is feasible, but usually not legal.

[NiHaoMike]

Also, DC string fires a real thing, so potential safety advantages there with the AC micro inverters.

You can get an arc fault detector like the PVAF-T2.

The Amish would have lived and built their house where it was not a requirement.  Usually it comes up when someone wants to convert to solar power with a battery system and disconnect entirely from the grid.  With a suitable investment it is feasible, but usually not legal.

Wouldn't a workaround be to just put in a transfer switch and leave it in the inverter position?

[EEVblog]

I got a response from Enphase, and their system can indeed do active VAR control.

All of the Enphase microinverters are totally capable of supplying any amount of reactive power.   This means that we can keep one inverter running at nighttime and get this one inverter to offset all the capacitive reactive current of all the shutdown inverters.   In this way we can end up with zero reactive current at a system level.   We could do this at an individual inverter level, but this would mean keeping all the inverters running 24 hours a day and it is more efficient to do this at a system level using just one inverter.

The ability for our microinverters to generate reactive current is part of the "advanced grid functionality" required by most jurisdictions before inverters can be connected to the grid.  Accordingly, your power utility company will dictate to Enphase how they want our system to behave,  and this includes the nighttime behavior.  Some utility companies want our solar system to zero out the reactive current at nighttime and if this is the case, we will program your inverters to do that (at a system level).

For most utility companies, common sense prevails, and they see the mutual advantage to them and the system owner of simply allowing a capacitive reactive nighttime behavior.

[Someone]

The Amish would have lived and built their house where it was not a requirement.  Usually it comes up when someone wants to convert to solar power with a battery system and disconnect entirely from the grid.  With a suitable investment it is feasible, but usually not legal.

Wouldn't a workaround be to just put in a transfer switch and leave it in the inverter position?

A large part of the economic justification for going off grid is not paying for a service you dont want/use. There are similar odd laws around connection to town water/sewer. In some places if the "essential" service runs past your property you are required to pay for it even if you dont use it.

[David Hess]

The Amish would have lived and built their house where it was not a requirement.  Usually it comes up when someone wants to convert to solar power with a battery system and disconnect entirely from the grid.  With a suitable investment it is feasible, but usually not legal.

Wouldn't a workaround be to just put in a transfer switch and leave it in the inverter position?

You could do that, but you are still paying for the hookup to the power grid whether you use it or not.

[bdunham7]

I got a response from Enphase, and their system can indeed do active VAR control.

All of the Enphase microinverters are totally capable of supplying any amount of reactive power.   This means that we can keep one inverter running at nighttime and get this one inverter to offset all the capacitive reactive current of all the shutdown inverters.   In this way we can end up with zero reactive current at a system level.   We could do this at an individual inverter level, but this would mean keeping all the inverters running 24 hours a day and it is more efficient to do this at a system level using just one inverter.

The ability for our microinverters to generate reactive current is part of the "advanced grid functionality" required by most jurisdictions before inverters can be connected to the grid.  Accordingly, your power utility company will dictate to Enphase how they want our system to behave,  and this includes the nighttime behavior.  Some utility companies want our solar system to zero out the reactive current at nighttime and if this is the case, we will program your inverters to do that (at a system level).

For most utility companies, common sense prevails, and they see the mutual advantage to them and the system owner of simply allowing a capacitive reactive nighttime behavior.

I see your issue got bumped up to someone that appears to know what they are talking about.

[Towger]

In this part of the world we get SFA for feeding power back into grid.  Often new systems in order of preference will change over from: Supply house, charge EV, heat water and charge a battery. The last option is to feed back into the grid.