Battery Usage Question

[ggunn]

Perhaps I'm the odd one out, but I think you should stop saying these things, or think about how to say them more accurately. What you say is true for the majority of legacy inverters, but it is and will be increasingly untrue for newer ones.

I say that it is true for most PV systems, which is for the time being true. It's also true that it is usually (maybe always) more expensive to set up than a straight grid tied PV system. I cannot contest your claim that Enphase and SolarEdge command 90% of the residential PV market, but the company I work for builds more than 500 residential PV systems per month in five US states and virtually none of them are from either of these manufacturers.

 

[ggunn]

Also, the comment about frequency munging leaves out the point that interactive inverters can be connected to non-grid primary sources, e.g. a battery inverter in an off-grid or temporarily islanded setup, which is also an increasingly common setup I'm sure our OP will want to eventually understand.

What I meant by that comment was that although many inverters can throttle back their output in response to changes in frequency, you cannot change the AC frequency that an inverter sees while it is directly connected to the grid.

 

[pv_n00b]

Unless someone is working with a non-export interconnection there is really no reason to curtail grid tied PV inverter output in a PV+ESS setup. Even if you get nothing for the export you lose nothing if the ESS is full and all the local loads are bring supplied from the PV system. Give the excess away if you can't find a local use. Sure you are just enriching the utility but you are enriching it with renewable energy.
If you have a microgrid mode and operate with the grid disconnected the more granular control you give the energy management system over the PV output the better the system will be. The old On/Off control where the PV system is either generating full power or generating nothing is not very efficient. Better than nothing, but poor at best.

 

[ggunn]

I say that it is true for most PV systems, which is for the time being true. It's also true that it is usually (maybe always) more expensive to set up than a straight grid tied PV system. I cannot contest your claim that Enphase and SolarEdge command 90% of the residential PV market, but the company I work for builds more than 500 residential PV systems per month in five US states and virtually none of them are from either of these manufacturers.

Full disclosure: the company I work for is a Sunpower distributor, and Sunpower microinverters are rebranded Enphase, but the monitoring for them is Sunpower proprietary and as far as I know does not have the capability you describe. Also, I have been out of resi PV for a couple of years (these days I am strictly commercial - cue Frank Zappa); things change.

 

[ggunn]

Unless someone is working with a non-export interconnection there is really no reason to curtail grid tied PV inverter output in a PV+ESS setup. Even if you get nothing for the export you lose nothing if the ESS is full and all the local loads are bring supplied from the PV system. Give the excess away if you can't find a local use. Sure you are just enriching the utility but you are enriching it with renewable energy.

I had that discussion with a customer a while back. He lives in a jurisdiction with tariffs not especially friendly to PV and he adamantly wanted not to give away any of the energy his PV system produces to "the man". When he discovered that it would actually cost him money to avoid doing that, he changed his position.

 

[ggunn]

I just saw this today, though apparently it was released about a month ago:

Enphase Energy Launches IQ8, the Industry’s First Microgrid-Forming Microinverter | Enphase Energy

Pre-orders begin today, with production shipments expected in December for North American customers FREMONT, Calif. , Oct. 25, 2021 (GLOBE NEWSWIRE) -- Enphase Energy, Inc. (NASDAQ: ENPH), a global energy technology company and the world's leading supplier of microinverter-based solar and battery

newsroom.enphase.com

I don't know if this will (yet?) affect the Sunpower rebranded micros that we employ.

 

[tortuga]

Unless someone is working with a non-export interconnection there is really no reason to curtail grid tied PV inverter output in a PV+ESS setup. Even if you get nothing for the export you lose nothing if the ESS is full and all the local loads are bring supplied from the PV system. Give the excess away if you can't find a local use.

I have been told some residential utility meters measure kwH in both directions, so if someone had the non-export situation you speak of they could acutally be billed for the power they export.

 

[GoldDigger]

I have been told some residential utility meters measure kwH in both directions, so if someone had the non-export situation you speak of they could acutally be billed for the power they export.

This happens only when POCO is using a traditional meter with anti-tampering features because they have not been notified that a grid interactive system is being installed.
POCO's goal is to prevent people from rewinding their meter by reversing source and load sides ("turning the meter upside down").

 

[tortuga]

This happens only when POCO is using a traditional meter with anti-tampering features because they have not been notified that a grid interactive system is being installed.
POCO's goal is to prevent people from rewinding their meter by reversing source and load sides ("turning the meter upside down").

Right so say your in a state that has a per kilowatt hour PV generation charge or a monthly solar fixed fee slapped on your bill, or just has no net-metering laws and thus the local utility does not support it.
In this scenerio it would be more cost effective to permit and install a PV / energy storage system, leaving the existing traditional meter alone, and keep all the excess power in the Energy Storage System.

 

[pv_n00b]

Right so say your in a state that has a per kilowatt hour PV generation charge or a monthly solar fixed fee slapped on your bill, or just has no net-metering laws and thus the local utility does not support it.
In this scenerio it would be more cost effective to permit and install a PV / energy storage system, leaving the existing traditional meter alone, and keep all the excess power in the Energy Storage System.

Except that would require installing the system without notifying the utility to avoid a charge connected to even having a PV system. Possible, but most likely they would notice the loss of revenue and investigate. Once they discover the illegal PV+ESS installation there would be problems for the owner.

 

[tortuga]

Except that would require installing the system without notifying the utility to avoid a charge connected to even having a PV system. Possible,

Yep very possible, I have seen one.

but most likely they would notice the loss of revenue and investigate.

Unlikely the utility would even notice, loads change all the time.

Once they discover the illegal PV+ESS installation there would be problems for the owner.

I would not say such a system would break any law, just the contractual agreement with the utility.

 

[jaggedben]

... just the contractual agreement with the utility.

Maybe not even that.

 

[pv_n00b]

I would not say such a system would break any law, just the contractual agreement with the utility.

For most utilities, a customer that goes from a $300/mo bill to $10/mo will trip a review flag in the system. You might be surprised then to know that a utility tariff is a legal contract between the customer and the utility. Violating that contract can have legal consequences. Good luck when your customer gets in trouble with the utility and pulls the contractor into the scuffle for aiding and abetting. What is most likely to happen is the customer is assessed for any lost revenue to the utility, fined for the violation, and the PV system locked out until it is permitted. Maybe the contractor is sued by the customer to recover that and the contractor is reported to the state board for a license review. Is a guerilla PV system really worth all that?

 

[ggunn]

For most utilities, a customer that goes from a $300/mo bill to $10/mo will trip a review flag in the system. You might be surprised then to know that a utility tariff is a legal contract between the customer and the utility. Violating that contract can have legal consequences. Good luck when your customer gets in trouble with the utility and pulls the contractor into the scuffle for aiding and abetting. What is most likely to happen is the customer is assessed for any lost revenue to the utility, fined for the violation, and the PV system locked out until it is permitted. Maybe the contractor is sued by the customer to recover that and the contractor is reported to the state board for a license review. Is a guerilla PV system really worth all that?

And the customer's service from the utility may be disconnected until the matter is resolved to their satisfaction.

 

[jaggedben]

For most utilities, a customer that goes from a $300/mo bill to $10/mo will trip a review flag in the system. You might be surprised then to know that a utility tariff is a legal contract between the customer and the utility. Violating that contract can have legal consequences. Good luck when your customer gets in trouble with the utility and pulls the contractor into the scuffle for aiding and abetting. What is most likely to happen is the customer is assessed for any lost revenue to the utility, fined for the violation, and the PV system locked out until it is permitted. Maybe the contractor is sued by the customer to recover that and the contractor is reported to the state board for a license review. Is a guerilla PV system really worth all that?

I'm skeptical. I'm skeptical of your first sentence because I've seen enough cases where it didn't go down like that, say when a customer had an 18th remodel but didn't replace the service panel. I suppose there might be flags in the sytem, but nothing seems to happen. As far as the rest...

First of all, one way around breaking any law or agreement might just be to apply to interconnect as a non-exporting system, thus avoiding any fees associated with net metering. So there's that, which just sort of takes the bite out of all of this.

On the larger point though, while I'm not skeptical that there would be some battles along the lines you describe, I doubt that the utilities can really push policies that incentivize a black market in electricity and then also marshall the extra resources to punish those who participate it. That doesn't work for most markets. I'm also doubtful that the typical service agreement obligates the customer to use a certain amount of electricity along the lines you imply. If I just use less electricity, then I just use less electricity, same as if I went on vacation or my air conditioner broke and I couldn't afford to replace it. There's no claim of 'lost revenue' for electricity that they didn't provide. A good lawyer will be able to fight back against any claims of harm against the utility as frivolous. And in the many cases where the bill might go from $50 to $10 or $300 to $200 instead of what you suggest, there will be less lost revenue to pursue per the cost to do so for each customer.

What it will come down to in the end is the money utilities can spend on lawyers vs. the bad press they'll get and the consequent erosion of public support for the regulations that might allow them to win those cases.

 

[Grouch]

Here’s some info from Generac you might find helpful.

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Thanks for sending this! I'll be reading this over the weekend.

 

[Grouch]

Except that would require installing the system without notifying the utility to avoid a charge connected to even having a PV system. Possible, but most likely they would notice the loss of revenue and investigate. Once they discover the illegal PV+ESS installation there would be problems for the owner.

I'll make sure to be filing an application with Con Edison so they know a PV system is going in . Have to learn the process though. A rep was supposed to reach out to me but never did.

 

[tallgirl]

Another question... can the grid be used to charge the ESS, or is that function solely for the PV array to do?

EDIT: actually I think post #2 answered this. so the grid can charge the ESS as well?

Unless you have a burning need to charge the batteries, charging or discharging batteries is a horrible idea. One number in the economic decisions about when to charge and when to discharge is the fact that most chemistries have a limited number of cycles in their lifetime.

 

[tallgirl]

And the customer's service from the utility may be disconnected until the matter is resolved to their satisfaction.

I was a TXU Energy customer and they went for months without crediting me for PV generation. I then found an interesting pair of laws.

1. PV system owners were "electric utilities".
2. Theft of electricity was a felony.

I was flying back from a meeting with some folks at Outback Power when I got a very apologetic call from some VP saying that they hadn't trained all of their people on PV systems yet and would I kindly not be mean to them.

Another time I was having a fight with my electric utility, so I disconnected from the grid thinking I could actually stay disconnected. That lasted for 9 days before the combination of bad weather and being careless resulted in the batteries running low and me giving in. BUT! It did get their attention and they once again straightened out my billing.

 

[rainwater01]

I was a TXU Energy customer and they went for months without crediting me for PV generation. I then found an interesting pair of laws.

1. PV system owners were "electric utilities".
2. Theft of electricity was a felony.

I was flying back from a meeting with some folks at Outback Power when I got a very apologetic call from some VP saying that they hadn't trained all of their people on PV systems yet and would I kindly not be mean to them.

Another time I was having a fight with my electric utility, so I disconnected from the grid thinking I could actually stay disconnected. That lasted for 9 days before the combination of bad weather and being careless resulted in the batteries running low and me giving in. BUT! It did get their attention and they once again straightened out my billing.

When did you try to go off grid? Was that with lithium or lead acid batteries? What system do you have installed at your place? Out of curiosity…


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