Long time listener, First time caller. 10 yr old Sunpower System, need opinions

[vikes98]

Not kicking you as you're blameless in vendor selection here, but potential PV users might take a lesson from your experience and predicament and be a bit more mindful of taking a longer view and spending a bit more time on vendor selection and maybe a bit less time and effort on finding the lowest initial price when considering all the details that go into acquiring a PV system.

I didn't pick Sunpower here... I bought the house and it came with it. So I consider it a pre-existing condition. Just trying to figure out what my annual consumption would be without solar is tough enough, since it appears the existing system is in decline...

I have spent tremendous time trying to learn about solar and what my options are, and I highly suggest any potential PV customer get familiar with the warranty and not to put much stock in it, since the combo of dealer, install and manufacturer creates the perfect finger pointing exercise... Especially considering any or all parties may not even be in business 10 - 25 years into the future.

I am not an Electrician, and my desire is to leave the analysis to professionals. It would seem to me this is something the manufacturer would start with.

Appreciate the help, trying to figure out what my options are and what the best course of action is... Waiting around fo Sunpower to do anything is about the same as waiting for Gadot.

[jflorey2]

Bought this house 2 years ago. Came with a now 10 year old Sunpower system with 2 inverters and 42 panels.

The panels are also 62x32 230 Sunpower panels. 29 are on 4 strings to a 7000m (single azimuth, slightly wnw) and 13 are on a 3000m (8 on a sw different angle and 5 also sw but slightly larger angle)

The system was spec'd as 9660 Watts DC and 8598 Watts AC. I'm in So Cal, so trying to figure out what this should generate on average per year. Any help would greatly be appreciated. All areas get massive unshaded sun year round for 6+ hours per day solar average. If my math is correct 8598 / 1000 = 8.598 kWH * 6.6 solar average days * 365 = 20,712 kWH / solar year max.

Going back to first principles, I suspect your system is poorly designed.

I am going to make a whole lot of assumptions here; feel free to correct me as needed.

Your array is 29 panels in 4 strings and 13 panels in 2 strings. That means you effectively have 4 strings of 7 panels each and 2 strings of 6 panels each. Now, either they feed into two inverters with a total of 6 MPPT channels (that's the right way to do it, in which case odd numbers of panels don't matter) or they feed into two inverters with a total of 2 MPPT channels (one per inverter.) That's the wrong way to do it, but since you are having problems, I will go with that.

Next I am going to make an assumption on your inverter, that one of them is an SPR-5200 and the other one is similar but smaller. (These are rebranded Fronius inverters.,)

The larger inverter is going to see a 25C MPPT of 287 volts and the smaller one is going to have an MPPT of 246 volts at 25C. Those inverters have an MPPT window of 240 to 380 volts. Thus if the temperature goes up by 8 degrees C (i.e. it's 33C at the panel instead of 25C) the inverter is going to drop out of its MPPT operating range and start losing power. You will see this most on hot days.

To confirm this:

1) If your inverter will read operating voltage, then observe it and compare it to the specs of the inverter.
2) If your inverter will not read it, then get an electrician to measure it on a hot day.

BTW I am making these assumptions because that's almost exactly what my system, installed ten years ago by Sunpower, uses. However, my system uses a 7s4p and 8s2p arrangement of panels, and thus is always within the MPPT range of the inverters.

ps. The spr-230-wht-u are not "positive ground." They are ordinary isolated panels with a 600V rating from either conductor to frame ground.

[vikes98]

Going back to first principles, I suspect your system is poorly designed.

Next I am going to make an assumption on your inverter, that one of them is an SPR-5200 and the other one is similar but smaller. (These are rebranded Fronius inverters.,)

The larger inverter is going to see a 25C MPPT of 287 volts and the smaller one is going to have an MPPT of 246 volts at 25C. Those inverters have an MPPT window of 240 to 380 volts. Thus if the temperature goes up by 8 degrees C (i.e. it's 33C at the panel instead of 25C) the inverter is going to drop out of its MPPT operating range and start losing power. You will see this most on hot days.

To confirm this:

1) If your inverter will read operating voltage, then observe it and compare it to the specs of the inverter.
2) If your inverter will not read it, then get an electrician to measure it on a hot day.

BTW I am making these assumptions because that's almost exactly what my system, installed ten years ago by Sunpower, uses. However, my system uses a 7s4p and 8s2p arrangement of panels, and thus is always within the MPPT range of the inverters.

ps. The spr-230-wht-u are not "positive ground." They are ordinary isolated panels with a 600V rating from either conductor to frame ground.

Appreciate the technical details. Happy to provide as much info, trying to clear through the clutter, as it seems like a lot of false information is thrown out and to those like myself that are very technical in other aspects of my knowledge are struggling with since I don't have experience or knowledge in PV and Electrical fundamentals (I know enough to know I don't know enough)

Both inverters are Sunpower branded, SPR-7000m (29 panels supposedly) and SPR-3000m with (13 panels). link to spec sheet http://www.solar-energy-solutions.co...78361484_1.pdf

Manual http://static1.squarespace.com/stati...ormat=original

Both were manufactured in 2008.

They have a 2 line LCD screen that shows Lifetime kWh and hours, daily kWh and hours, the gridtype and then Pac and Vpv which I assume are current ac power and current dc input voltage.

Gridtype - 240V
L1 124V, l2 121V (larger inverter 7000m) L1 122V L2 122V (smaller 3000m)

7000M
Pac 2001W
Vpv 268V

E-today 5.42 kWh
mode Mpp

E-Total 97151kWh
h-Total 43242h

3000M
Pac 799W
Vpv 251V

E-today 2.19kWh
Mode Mpp

E-Total 41254kWh
h-total 44591

This was read at 11:30am on a cloudy / overcast day with temp around 70F

Forecast is similar for next week, so might be awhile before it gets above 95F to take similar readings

It is my understanding that there are 4 strings on the 7000m and 2 strings on the 3000m

I do not know how the strings are arranged on the roof and what panels go where, none of the plans or documents explain the installation.

I do know that the original design was for 40 panels and 3 months laters 2 more panels were added, but as to where and why, I do not know.

The 29 panels going into the 7000m are all on the same plane, and there are two different placements and planes for the remaining 13 going into the 3000m

[J.P.M.]

[QUOTE=vikes98;n399183]Appreciate the technical details. Happy to provide as much info, trying to clear through the clutter, as it seems like a lot of false information is thrown out and to those like myself that are very technical in other aspects of my knowledge are struggling with since I don't have experience or knowledge in PV and Electrical fundamentals (I know enough to know I don't know enough)/QUOTE]

I'd reiterate the suggestion Peakbagger and I both made in the first sentences of our first posts to this thread about getting and reading a copy of "Solar Power Your Home for Dummies" as a first step toward the PV knowledge you say you don't have.

Respectfully,

[vikes98]

I've read that book. I am probably understating my knowledge of the core concepts but where I lack is the experience and expertise.

[J.P.M.]

I've read that book. I am probably understating my knowledge of the core concepts but where I lack is the experience and expertise.

Understood. Have you done any modeling with PVWatts yet to get some idea or dart throw est. of what the system might do when new ?

It helps to know where you might have started to get a better feel of how you got where you are.

[jflorey2]

Both inverters are Sunpower branded, SPR-7000m (29 panels supposedly) and SPR-3000m with (13 panels). link to spec sheet http://www.solar-energy-solutions.co...78361484_1.pdf

OK so these are rebranded SMA's.

First off the extra panel on one string (for each inverter) isn't doing anything; you could get rid of them safely. Those SMA inverters only have one MPPT channel each.

Secondly the voltages are close to OK. On the 7000 watt inverter you'd need to hit a panel temp of 70C to start hitting bottom on voltage and it's rare to see panel temps above 65C. There isn't as much margin as I'd like - at 65C your string voltage can drop to 245 volts, and adding 2% voltage drop (not unusual) you are down at 240 volts. Still you are right at the margin there.

If it were my system I'd get/borrow a pyranometer to measure actual insolation and then use that as a starting point to compare to instantaneous power. If I got ambitious I'd disconnect one of the panels (one of the ones the system doesn't need) and run a curve on that to see how the panel itself is performing. But I agree with several others here who said that the first step is to relentlessly bang on Sunpower until they give you some answers.

[vikes98]

According to PVWatts, and using the specs from the panels 230 watts x 42 panels puts the DC rating at 9.66 kW and based on location and PVWatts data, the system should be able to generate 16.36k kWH / year (15.7 to 16.46k). Based on my readings, the current system didn't generate 12k last year and has averaged about 13k over its lifetime (per year based on meter reads)

This is backed up by several dealers that have quoted replacing the existing panels minus setbacks due to code around the 14k range.

Something is causing the system to degrade much faster than expectation. Could be a poorly designed / implemented system, could be warranty related issues. I simply don't know and am trying to figure out how the manufacturer, Sunpower, could even stand behind a claim of 90% performance guarantee for first 12 years, without at least an explanation of how they would measure such a claim.

Ultimately I expect Sunpower to point the figure at the now defunct installer / designer and blame that for the failures. Regardless, the question remains as to what, if anything I can or should do to add to, upgrade or replace to maximize my future investment.

Here's what I do know, if it fails, and I assume this will be the inverters that fail, it will most likely happen in the biggest months of solar generation. My assumption has been that due to the high heat, our energy consumption skyrocketed but given what I am seeing on the last several hot days, its more likely a combo of heat related failure (or overvolting, etc.) that wasn't considered 10 years into the system combined with running ACs, etc.

The hardest part is with an existing system that has no real monitoring and being on net metering, I have no idea what power I'm using if I didn't have solar, its just a wild ass guess as to how much solar I actually need as a benefit to cost ratio.

I'm happy to spend the money as if I didn't have this existing system, but switching out systems or adding to this system would result in getting out of my grandfathered net metering to TOU as well. Plus the permitting and time puts me well outside the peak solar months for generation anyway.

Combined with the reduction in federal tax credits, it seems like a good time to do the analysis and determine if now is the right time to do something, or wait and see over next months to years as to when to fix or replace this apparent declining / underperforming system.

[vikes98]

OK so these are rebranded SMA's.

First off the extra panel on one string (for each inverter) isn't doing anything; you could get rid of them safely. Those SMA inverters only have one MPPT channel each.

Secondly the voltages are close to OK. On the 7000 watt inverter you'd need to hit a panel temp of 70C to start hitting bottom on voltage and it's rare to see panel temps above 65C. There isn't as much margin as I'd like - at 65C your string voltage can drop to 245 volts, and adding 2% voltage drop (not unusual) you are down at 240 volts. Still you are right at the margin there.

If it were my system I'd get/borrow a pyranometer to measure actual insolation and then use that as a starting point to compare to instantaneous power. If I got ambitious I'd disconnect one of the panels (one of the ones the system doesn't need) and run a curve on that to see how the panel itself is performing. But I agree with several others here who said that the first step is to relentlessly bang on Sunpower until they give you some answers.

Thanks, that matches up with my undestanding that 2 of my 42 panels are doing essentially nothing for the system, which probably explains why the original installer added 2 more 3 months after install.

I keep pounding on Sunpower for at least options... If this is how they handle warranty inquiries, why in the world would anyone ever promote their 25 year warranty as anything but sales rhetoric.

Given the relationship with dealers that seemingly disappear and appear by the hour, Sunpower has the easiest escape clause, by blaming the installer for any issues and then the next dealer comes in with replacement cost and the cycle repeats itself.

Am I safe to assume there are other companies besides Sunpower that actually stand behind their products, past installs and at least respond in a timely fashion to end customers? Or is it dealer roulette?

How far up the food chain do I need to go to get basic answers from Sunpower? Guess we'll find out