Adding storage to my Enphase system

[GXMnow]

I actually got back another e-mail from Schneider this morning. But the answer was not encouraging.

"Without DC coupling, your loads will directly be connected to the grid, and therefore, when using the grid, you are not able to have AC coupling at the same time, and viceversa.

The main consequence of particularity is that once the battery has been discharged below the Grid Support volts value, it will enter the voltage range between Grid Support volts and Recharge volts and stay there forever.

Your grid will do a pass-though without inverting or charging your batteries, but you are also not getting any solar energy because AC coupling cannot be enabled at the same time as the grid.

That is why your batteries won't get charged again, if you don't keep changing your configuration manually, as you are doing at the moment."

Well..... It seems their engineers are either lazy, stupid, or just don't care.

I am very interested in seeing their reply to what I sent them after that. I wrote out a bit of pseudo basic code.

If "AC Coupling" = True and "Charge Block Time" = False
Then set "Recharge Volts" = 57.5 set "Grid Support Volts" = 58
Else set "Recharge Volts" = 47.5 set "Grid Support Volts" = 48
End If

Then I said, "There, fixed your code, now have the engineer send me his paycheck."


Maybe a bit rude, but SERIOUSLY?? How can they think this is such a strange thing to want?

This is basically the code I am putting into my PLC to set those registers in the XW inverter. I am getting help with the code from a relative with a computer science degree. Hopefully between the two of us we can get the handshake with Modbus working properly.

 

[400bird]

I wish I knew if lazy or dumb was the case, but I don't think it really matters in the end.

While you're fixing their code, could you also disable the 0.5 volt offset when AC coupled? Lol

Also, I am sure your emails are getting red listed!

 

[GXMnow]

Rather than eliminating the 0.5 volt offset, they should allow Grid Support Volts to be lower than the Recharge Volts and just have it ignore recharge while it is in Charge Block, and ignore Grid Support while Grid Sell or Load Shave is active. Very simple fix. I offered that one first. The code idea was something that the Gateway could do by just sending the settings based on the clock.

Poor babies at Schneider, I am calling them out for not supporting a feature they advertise on their web page.

 

[GXMnow]

So I got a very nice reply back from Schneider tech support.

He has forwarded my suggests and the code clip for the gateway. And also put my name in as a beta tester when they do come out with a new firmware. I am not going to hold my breath, but I will hold optimism. He agrees this is a feature they should support. He also said they will look at the web site and see if they can word it better to not mislead about the capability.

As for Enphase, they looked at my production and said they did not see a problem. Well DUH. I intentionally did the test right at the end of the solar day so I would not loose a lot of energy production. I was asking if I should try a different grid profile to see if that could be causing the inverters to go offline when there is a power glitch, like when it goes into backup mode on the inverter. They totally ignored 3/4 of my e-mail.

So it is back to the pile of papers trying to figure out how I am going to code the PLC. My first version is going to be really slow. It only has to change 2 registers twice a day. So if it takes 5 seconds to load the values, it is not a big deal. The version 0.5 is not even going to bother checking the charge rates etc. It will just make it charge in the morning and discharge in the evening. If I can get that to run reliable, then I will try to add reading the grid power and adjusting the charge and sell currents to zero the grid power.

Should I start a new thread on the XW-Pro PLC control? Where should I put it?

 

[GXMnow]

The last 2 days have started with heavy overcast. My entire array was putting out less than 500 watts until after 11 AM. Without an input to know how much solar is being produce, the XW-Pro was pulling quite a bit more power as it was trying to charge up the batteries. In reality, the way my net billing is setup, as long as I don't charge between 4PM and 9PM I am fine. But I do want to make it charge as much as possible while the sun is making the power, and not pull from the grid. The letter of the rules for battery storage states that you can't export stored energy that came from the grid. Obviously, you can't prove where the electrons came from, but looking at my data from yesterday and this morning, it is pretty obvious about half of the power that got stored in the battery came from the grid. But now at 3PM, the battery is in absorb charge, nearly full, and the solar is exporting back to the grid. If I had the system start storing later, it would have been fine, but there was no real way of knowing, unless you really trust weather forecasts. I found a few different energy meters. This one looks promising for the price

Bundle BEY630MCT & 2x200 Amps CTs - - Amazon.com

Bundle BEY630MCT & 2x200 Amps CTs - - Amazon.com

www.amazon.com

I'll try to find more info on it. It would be very cool to have the PLC adjust the charge and grid support currents to totally flatten my power use across the day, and zero it during the peak rate time.

 

[svetz]

The last 2 days have started with heavy overcast. My entire array was putting out less than 500 watts until after 11 AM.

If it makes you feel better, we got about 10" of rain on Tuesday, and I had less than a kwh of power for the day.... ?

 

[GXMnow]

Wow. We could use some rain here, but that is crazy.

 

[Hedges]

Have you considered adding a Pelton wheel to your downspout?

Micro/Mini Hydro Systems - Turbines - Pelton Wheel Turbine - Rickly Hydro

ricklyhydrosystems.com

(in the vein of that traffic-powered wind turbine out of England)

Or replace the front steps with a treadmill for solicitors?

Looks like I got 60 kWh today in San Jose. Which is pretty good, considering bushes have grown to where they shade some of my arrays in the afternoon. (Production was 3x the capacity of my battery.) Plan to re-orient them for morning sun and swap panels for 50% more efficient SunPower ones when I do.

 

[GXMnow]

How many panels do you have? My 16 panels top out at about 31 KWH in a day. About 20-21 KWH is what I am getting lately. But the last two days, this cloud cover moved in and I only produced 15 KWH yesterday and 11 KWH today. Each panel produced between 600 and 750 WH so they are all working, just no decent sun for the first half of the day. Peak power still topped 3 KW in the afternoon but it soon dropped off again.

How much power can a turbine in the gutter actually make? The worst rain we ever get here is maybe a decent garden hose worth coming out the downspouts, and it never lasts very long. Same with wind. We do get some gusty days, but 90% of the time, nothing.

I am measuring out to see if I can fit four 400 watt panels on my garage roof. But I am really torn whether I should DC couple them to the battery bank, or just get 4 more Enphase inverters. It would be cool to get iQ8's when they become available. They could help the XW-pro form the grid.

 

[svetz]

10" is unusually high even for here. I was watching myRadar and there was a narrow yellow curved continuous band that was pretty much centered over the house all day- it was like the cartoon where the cloud follows the cursed guy around. 5 miles south had 6" and 3 miles north 4" (weather underground sites). I wish I could have shipped a few inches to you all and the rest to Colorado. Looks like more is coming (right now it's SW of Cuba and building up). 7.8 kW array in 23 LG panels. Gutter turbines, I'm pretty sure, were meant as a joke.

 

[Hedges]

How many panels do you have? My 16 panels top out at about 31 KWH in a day. About 20-21 KWH is what I am getting lately. But the last two days, this cloud cover moved in and I only produced 15 KWH yesterday and 11 KWH today. Each panel produced between 600 and 750 WH so they are all working, just no decent sun for the first half of the day. Peak power still topped 3 KW in the afternoon but it soon dropped off again.

How much power can a turbine in the gutter actually make? The worst rain we ever get here is maybe a decent garden hose worth coming out the downspouts, and it never lasts very long. Same with wind. We do get some gusty days, but 90% of the time, nothing.

I am measuring out to see if I can fit four 400 watt panels on my garage roof. But I am really torn whether I should DC couple them to the battery bank, or just get 4 more Enphase inverters. It would be cool to get iQ8's when they become available. They could help the XW-pro form the grid.

Presently mounted: 96, 120W Astropower, 24, 165W Sharp, 16, 237W SunPower.
On one particular day total was just shy of 100 kWh. Looks like my recent number as a percentage was similar to yours, and I didn't have clouds yesterday.

I've figured out a way to put the 61" x 41" SunPower in a portrait orientation, 4 in a row on a pair of 17' rails (drilling holes in the frames of two hanging off the end.) Then 4 more panel for each additional rail (adding a flat piece of metal tying together panels that share a rail.) Each array will be 6x4 physically, 21'x20', and wired as 3 strings of 8. There will be four of those arrays, some morning and some evening orientation.

Between a fence and retaining wall I have a 5th array oriented at 4:00 PM sun to keep production from dropping off as soon given our new 4:00 to 9:00 PM peak time. That will get the relocated Sharp panels. I may put the Astropower on roof after replacing shakes with shingles; up to 3/4 of them may fit. But I probably don't need the power at this time.

Downspout generator - I'm joking of course. Places with frequent rains get their water from roof but probably never enough power to matter. Small pelton wheel starts to get useful with 2 gallons/minute 24 hours a day and 100 foot head. Usually there is more water in winter - without a variable nozzle, simply a valve to turn on additional nozzles would let a small turbine generate more power during months when PV is less. I have a property with seasonal stream but haven't set anything up because not living there. Nice thing about high head with pelton wheel is hardware is small compared to a low-head generator like for a small dam.

 

[ArthurEld]

What do you do with all that energy Hedges?

 

[Hedges]

What do you do with all that energy Hedges?

That's my problem. I've got electricity down to just $10/month fee to be connected, but water for landscaping on my (almost) 1 acre has gone through the roof; it's the biggest bill other than mortgage and property taxes.

I was allowed rebate on a system to cover 200% of consumption, so I ran 2 HP pool pump for a continuous month to get a bill documenting power. My plan was to get another home in an island paradise and ship half the system there. (Early rebate program didn't have the wording about intending to keep system in place indefinitely.) I never did follow through with that.

I added an electric duct heater after the gas furnace, and can switch between the two. When peak time of use was Noon to 6:00 PM, my panels with 2:00 PM orientation earned lots of credits and I could get back more power off-peak. Gas heat might be $80 to $120 per month, but electric can hit $700. So long as that is Monopoly money it isn't a problem, but have to avoid running past the surplus I've been credited for.

California or at least some cities now prohibit gas connection for new homes, with the exception of gas stoves for some upscale communities. Big mistake, I think; ought to allow gas/electric appliances so it will be possible to use gas during electricity shortages, which we've recently experienced.

My original system cost $8/watt (less 50% rebate) but now I can upgrade panels and inverters for $0.50/watt, increasing output on the same mounts by 50%. I'm doing that mostly because I can, not because I need to, and out of concern the new time of use schedule will cost me if I don't. At $0.50/watt, the system will cost me $0.025/kWh amortized over a decade. Just looking at getting 50% more power than existing system, $0.075/kWh for the extra. Compare to $0.15, $0.30, $0.45 rates depending on time of day.

 

[Hedges]

Over-paneling beyond average needs also would help with off-grid operation, especially since my battery is sized for 1/3 day rather than 3 days.

Some charts I've found indicate San Jose average winter equivalent hours full sun is about 1/2 in winter what it is in summer.

US Solar Insolation Maps

For designing a system, you almost always use the worst case, or December-January map.

www.solar-electric.com

2 to 3 kWh/m^2/day in December, 5 to 6 in June.

(given the large geographical area covered, suspect it represents sun angle and hours of daylight but not local cloud/fog cover)

But here's a data set for Oakland which shows winter 1/4 of summer

https://www.nrel.gov/docs/legosti/old/789.pdf

647 btu/ft^2 in December vs. 2350 in June

Daily rather than monthly max/min would be better for my system.
I consider battery cost to be an order of magnitude higher than PV cost, so my model is "use it or lose it" not "save for a rainy day".
And that would be if I was using the battery daily. Mine is just floating, waiting for an occasional grid failure or rotating outage.
That of course is coming down quickly with batteries. PV came down by a factor of 10 or 20 in the past couple of decades. Now it is battery's turn.

 

[GXMnow]

Here are 2 days of my usage from SCE this past week. It has been cool enough that the A/C compressor has not needed to run at all. BUT the solar also has not been producing the best either.



We are now on Winter rates, so it is 3 sperate times. The light green is the "Super Off Peak" which lines right up with when solar actually works. Hmmm. So it is 25 cents per KWH there, the lighter orange from 9 PM to 8 AM is the "Off Peak" rate at 27 cents. The darker orange, which goes from 4 PM to 9PM is the "Mid Peak" rate which for winter is 38 cents.

I was able to net a bit negative during the mid peak rate on both days. I had decent sun on the first day, so even though it was charging during the super off peak, it went to exporting power for a good chunk of it. On the second day, we had basically no sun, so the charging current was coming from the grid. So I did buy more 25 cent power than I should have, but then exported most of it back to them at the 38 cent rate. Ideally I want to get closer to zero on both ends. I actually made a little money this way, but I really do want to keep it to only exporting solar power. Looking at the actual numbers, this is really small change. They scale the graph, so as I use little energy, it just scales the Y to fill the height. So what looks like a big hump is really only hitting 2.3 KW coming into my home. That is not even 10 amps on my main breaker. And my export peaked at just 700 watts. So to be fair, my "normal" steady house load is about 1,000 watts. So my solar power charging the battery, and then exporting and running all of my house load for the 5 hour peak rate time, theoretically saved me about $2.30 more than just the solar alone on just 1 day. That is a real good day though. More common is about $1.50 per day. With solar only, I produce about 18 KWH when I get decent sun. But that would all be at the 25 cent rate. That is $4.50 per day on solar alone, and $6.80 per day with the battery bank shifting it to peak rate time. My system has produced 9.1 Megawatt hours since it went online. It's first day was July 30 of last year. So it has been running for a year and almost 3 months. 365 + 85 days = 450 days 9,100,000 / 450 = 20.22 KWH / day average. I will estimate, it will hold at least 18 KWH / day in the future.

Dumb math problems...
Solar alone cost me $13,000 / $4.50 = 2900 days or about 8 years to pay it off.
The battery system total has cost me about $6,500 and I can save about $1.50 per day more ($2.30 was ideal) 4333 days or 12 years.
Add them together though, and it does not look so bad. $19,500 / $6.00 per day is 3250 days or 8.9 years.

So adding the battery only added a year to my payoff time, and that is if I don't get the 26% tax rebate on the XW-Pro inverter. Of course, the price on the surplus Bolt batteries makes a huge difference. If I bought a similar amount of LFP capacity, even with cheap import cells, it would have added a few thousand. I also got a crazy good deal on the inverter and free shipping. If I get just 6 years out of the batteries, I am still doing well. And maybe new battery tech will be available when these start to die off.

 

[svetz]

Cost of power goes up here every year, if you're the same the payback will be sooner. Of course, considering they turn your power off when its windy and dry it's probably priceless. I think you're smart to shop bargains and right about the new battery tech time frames (if nothing else, there will be more second-life battery systems on the market driving costs down).

 

[GXMnow]

It is amazing how the weather can change.
We went from over 100 for a week straight to below 50 last night, and a high under 70 today. Most of the morning was still in the 50's with strong winds, but almost no clouds and a lot of sun. Today looks to be my highest solar production in weeks. I topped 3,500 watts for a full hour and I am over 19 KWH already and it is just 3:15 PM. I still have over 2 hours of production left. My highest in the month of Oct. was 22.6 KWH. Will it beat that? Quite a change from the last 3 days of overcast barely hitting over 8 KWH a day.

 

[GXMnow]

My "Anti Murphy's Law" strikes again.

Murphy's Law says "Whatever can go wrong, will go wrong"
My Anti Murphy's Law says "Whatever you have prepared for, won't happen"

My brother got solar over a full year before me. In almost 3 years, he has had just one power outage, and it was not very long. But he still decided to buy a generator just in case. He has no storage, so his solar goes out with the grid. I told him what I am doing and he has helped me get my gear installed. He says he may add a battery as well when he sees how mine goes. His system is Sun Power AC panels, they have built in micro inverters.

Sure enough, our valley had a power failure. Over 5,000 homes lost power. He was in the dark, but my power stayed on.

I have the battery and didn't lose power. He still does not have storage, and loses power.

 

[ArthurEld]

I hope I never lose power and my 66 cells never get used.

 

[svetz]

... he still decided to buy a generator just in case. ... our valley had a power failure...He still does not have storage, and loses power.

What happened to the generator?