Valdemar
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Re: Official Southern California Edison thread

Sun Apr 23, 2017 4:36 pm

tbleakne wrote:
He did imply that the PW would automatically cut in if the grid goes down. This by itself is a big step for the utilities to approve, because it means they are relying on the software and not a manual disconnect to keep your generation off the grid when the grid is down. If you folks have different information, please post.


Haven't they already relied on software in grid-tied inverters that shuts down production when the grid goes down? Same kind of idea.

Anyone knows how these batteries are installed? It would seem there must be some sort of disconnect between the MSP and the grid for backup operation.
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tbleakne
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Re: Official Southern California Edison thread

Sun Apr 23, 2017 4:53 pm

In the spirit of "Know thy Enemy" I am posting this link to an interview from Fortune with the NV regulator, Chairman Thomsen, who had a lot to do with the alarming decision by the public utility commission in NV killing Net Metering in NV in Dec 2015.
The original decision phased out grandfathering which no other state had tried, but I believe grandfathering of Net Metering was re-instated later.

http://fortune.com/2016/04/12/solar-firestorm-nevada/

At one point deep in the interview he states:

I’ll tell you, we sat through 20 hours of public comment and the most moving parts of that were the seniors who said, 'I've taken out a second mortgage on my home to put on solar that starts at the retail rate and escalated 3% annually.' I was gobsmacked to hear that. That to me is a reprehensible sales tactic. I wish the commission had the ability to prevent that from happening.

I seriously doubt this. Most likely he was conflating two different sales deals:

Either buy system outright (and possibly do that with 2nd mortgage),
Or pay nothing upfront, and buy the electricity from the array owner at a rate that goes up 3% annually.

If it was both, I agree it would be a fraudulent sales proposal. I also agree the second deal by itself is not good, but some people get pressured into it.

You say what’s the difference between solar power coming off a rooftop that the utilities have to pay 11 cents for, versus the 4.5 cents they're paying for solar energy from large-scale solar panel projects? The delta has gotten so big. That’s the debate.

Compared to SCE prices, 11 cents looks awfully cheap to me. He seems to attribute very little extra value above wholesale to fully distributed power from our rooftops.
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abasile
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Re: Official Southern California Edison thread

Mon Apr 24, 2017 11:59 am

tbleakne wrote:I was told by a Powerwall installer guy at a Tesla OC meetup last month that PW was currently only licensed for Backup, not load leveling. I believe this means you can't draw from the battery unless it thinks the grid is down, but perhaps I am wrong. If you are doing load leveling, you need different software that watches you house usage and solar generation simultaneously.

I'm still not totally clear on how all of this works, and am currently seeking answers through my contact person at Pick My Solar. What I do know is that, to be eligible for SGIP rebates, battery systems must be used for more than just backup purposes; the battery must be cycled at least 52 times during its first year of operation (partial cycles count), from a renewable source. Tesla/SolarCity has been assisting Powerwall customers in applying for SGIP. That implies that Tesla has obtained, or expects to shortly obtain, whatever licensing may be needed to support load leveling.

tbleakne wrote:He did imply that the PW would automatically cut in if the grid goes down. This by itself is a big step for the utilities to approve, because it means they are relying on the software and not a manual disconnect to keep your generation off the grid when the grid is down. If you folks have different information, please post.

In the "Powerwall 2 waiting list" thread on TMC, the user jeeps1979 (in Crestline, by the way) posted a system diagram that seems to show a "gateway" between the main panel and the service meter for this purpose. But there is some question as to how that could work, particularly with main panels that integrate the service meter. Also, if the grid is down, the battery is fully charged, and there is surplus PV generation, I presume that the PV would need to be automatically disconnected. I hope to learn more.
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GRA
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Re: Official Southern California Edison thread

Mon Apr 24, 2017 3:30 pm

Not familiar with the current setups or what is/isn't required, but grid-intertied PV/wind/genset with battery backup used to just use an automatic transfer switch. Here's some discussion from almost 6 years ago: https://www.civicsolar.com/support/installer/questions/what-are-options-grid-tied-array-continue-generate-power-event-power
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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abasile
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Re: Official Southern California Edison thread

Mon Apr 24, 2017 3:55 pm

Following is a query that I sent to Pick My Solar over the weekend. They just responded that the answer is "yes" to all of the below questions:
Thanks for getting the contract sent out. I’ve reviewed it, and would like to ask for written confirmation of a few things before I sign. I’d like to confirm that the contract includes the following, which would reflect our phone conversations, I believe. If my understanding isn’t correct in some area below, then please let me know!

1. All circuits in our home will be backed up, meaning that our entire home would be powered by the battery in the event of a grid outage. I understand that our usage during an outage would be limited by the 5 kW maximum continuous power of the Powerwall 2 (when new) as well as by the available battery charge.

2. During a grid outage, subject to available sunlight, our solar panels will continue to power the circuits in our home, with any surplus going into the battery.

3. During a grid outage, our home’s electrical system will essentially function as an isolated microgrid.

4. During normal operation (no grid outage), we will be able to choose to charge the battery from our surplus solar power (above whatever our house is using) during certain hours, namely during the TOU “super off peak” and “off peak” hours.

5. During TOU peak hours, we will have the ability to zero out our use of grid electricity by drawing from the battery instead, subject to available battery power/charge.

6. During TOU peak hours, we will also be able to feed any surplus solar power (above whatever our house is using) into the grid rather than using it to charge the battery.
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Valdemar
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Re: Official Southern California Edison thread

Mon Apr 24, 2017 8:00 pm

Make sure this becomes a part of the contract as it may well be an ignorant sales rep just trying to make you sign it, just an e-mail may not be enough of a proof in court.
'11 SL, totaled
-1CB@33k/21mo, -2CB@53k/33mo, -3CB@68k/41mo, -4CB(41.5AHr)@79k/49mo, -5CB(38.85AHr)@87.5k/54mo
-0CB(66.14AHr)@87.5k/54mo (BBB)
54.94AHr, SOH 86%, 130k miles
9kW Solar

GregH
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Re: Official Southern California Edison thread

Wed Apr 26, 2017 9:58 am

In olden times battery based grid tied inverters like my old Xantrex/Trace SW4048 would do all of the above.. albeit with PV strings in a relatively low voltage (48-55V) tied to batteries with no ability to do peak powerpoint tracking.

If the grid goes down, the house isolates itself and can run off the battery. If the sun is shining the battery is charged from the sun simultaneously. If the sun is providing more than the house is demanding the batteries could overcharge. I was too cheap to get a charge controller for my original lead acid pack 16 years ago so I setup a circuit to disconnect the PV by sending a small current through one leg of the GFCI thus throwing the breaker, disconnecting the PV and preventing the overcharge of the batteries. If I came home at night and saw the GFCI tripped I'd just flip it back on... I know, crude..

Now with the 10kWh lithium battery I never go over about 85% SOC or below 35% SOC so I have extra margin in both directions if the grid goes down for a few hours. Worst case would be the grid going down at 2pm right when the batteries are full on a sunny day.

Modern micro inverters on PV systems all have the ability to disconnect automatically in the case of a downed grid to prevent islanding.

Presumably the PW2 also can disconnect from the grid and power the house like my old inverter.

The question of when to charge the batteries is a good one though:

Should I charge them at super off peak rates ($0.13/kWh) and then let the solar power generated in normal off peak ($0.27/kWh) flow right out to the grid and get credit at that rate?

Or should I not charge overnight, put the grid in silent mode all night and during most of the day while the sun directly charges the battery. When the battery is full then turn around and sell full blast until 8pm at the end of the super on peak? That might be healthiest for the grid but there's no incentive in TOU-D-A for me to do that.

Charging the batteries from the sun is more efficient.. But in the end I think I'd rather get credit for the solar at $0.27/kWh and buy extra energy at $0.13/kWh to charge the batteries.

Like I'd mentioned before, this cycling of about 6kWh/day is netting me about $400 annually on the SCE TOU-D-A plan.

The actual battery cost (used EV batteries) is about $120/kWh. The cost for someone without one of these old 48V inverters would be the cost of adding another inverter.. potentially $1000-$1300. Battery backup might still be possible with one of these inverters but I'm looking into even cheaper options ($400-$500) that might be able to do this but not provide the switch to provide backup power.. it depends what your priority with batteries is.. arbitrage or backup.
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abasile
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Re: Official Southern California Edison thread

Wed Apr 26, 2017 12:28 pm

GregH wrote:Like I'd mentioned before, this cycling of about 6kWh/day is netting me about $400 annually on the SCE TOU-D-A plan.

Is this actually permitted under TOU-D-A? While I haven't closely studied the rules, I've gotten the impression that you're not supposed to feed into the grid unless it's directly from your renewable energy generation. Otherwise, there'd be nothing stopping someone from buying lots of batteries (as in, two Powerwall 2 units totaling 27 kWh of usable capacity) and fully cycling them daily for arbitrage. That'd net about $1800 annually in credits, on top of a possible 30% income tax credit.

Under the terms of the SGIP rebate, you have to cycle the battery 52 times per year, and those charges have to come from your renewable energy source.
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Re: Official Southern California Edison thread

Wed Apr 26, 2017 1:32 pm

abasile wrote:
GregH wrote:Like I'd mentioned before, this cycling of about 6kWh/day is netting me about $400 annually on the SCE TOU-D-A plan.

Is this actually permitted under TOU-D-A? While I haven't closely studied the rules, I've gotten the impression that you're not supposed to feed into the grid unless it's directly from your renewable energy generation. Otherwise, there'd be nothing stopping someone from buying lots of batteries (as in, two Powerwall 2 units totaling 27 kWh of usable capacity) and fully cycling them daily for arbitrage. That'd net about $1800 annually in credits, on top of a possible 30% income tax credit.

Under the terms of the SGIP rebate, you have to cycle the battery 52 times per year, and those charges have to come from your renewable energy source.


Good question.. If you're willing to shell out the cash for Powerwall 2s with installation I don't know what would stop you from doing this.

There's nothing wrong with charging batteries from the grid at whatever time you're willing to do so. The question is when you feed it back to the grid in the evening (when the grid REALLY DOES NEED IT), does it matter where those electrons came from? I really don't know.

Yes the addition of SGIP $$ would seem to tip the scales. My inverter was 16 years old and the batteries were cheap.

I'm cycling the battery 365 days a year but I haven't received any SGIP money.
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Re: Official Southern California Edison thread

Wed Apr 26, 2017 2:41 pm

GregH wrote:There's nothing wrong with charging batteries from the grid at whatever time you're willing to do so.

Yes, agreed.

GregH wrote:The question is when you feed it back to the grid in the evening (when the grid REALLY DOES NEED IT), does it matter where those electrons came from? I really don't know.

I agree that feeding into the grid during the evening is good for the grid.

Whether the utility is okay with crediting you at peak retail rates is another matter. The CPUC (under NEM 1.0) forces them to credit you at retail rates whenever your solar panels are producing a surplus. But does the utility have to buy whatever comes out of your battery? I don't know, and I'd be happy to be proven wrong.
2011 LEAF at 71K miles, pre-owned 2012 Tesla S 85 at 98K miles
LEAF battery: 9/12 bars and < 49 Ah (-28% vs. new)
Tesla battery: 250+ miles of range (-5% vs. new)

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