Used Sunpower panels for Skybox

Ampster
Ampster Registered Users Posts: 174 ✭✭✭
in Grid Tie and Grid Interactive Systems #1
I recently installed an Outback Skybox with a small battery pack. Originally I was planning on waiting until Spring to evaluate whether to add more battery capacity or add some solar. I already have a grid tied system. I recently discovered an opportunity to acquire some 10 year old Sunpower 305 Watt panels for $90. The West facing patio cover where I propose to install them has some shading in the late afternoon.  

I am looking for input about the use of optimizers to possibly compensate for some of the potential shading that this location may have. I have read that Solaredge optimozers may work but I wont have any of the powerline data available. I have heard of other optimizers that may be less expensive. Any ideas about optimizers for this situation? FWIW, these panels put out 54v and I plan on employing 8 or 1o of them in series which is within the voltage range of the Skybox.

8 kW Enphase micros AC coupled to a SolArk 12K
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,904 ✭✭✭✭✭✭
    edited January 2019 #2
    If you have shading you need another controller to keep from messing up the array in the sun.  This is the best way!

    I use Sunpower in strings of 6 to 8 and they are amazing panels. The last Skybox we did was with an external Schneider 600v mppt for a virtual array. You could also use morningstar's 600v controller.

    or just try it and it might be good enough. Clouds are the enemy of one controller and if you log the mpv you will see it. Still, it might be good enough.

    How is the area recovering from the fires?  Down here, every time it rains they close 140. Winter Storm warnings go up late tonight. Good times at 9,000+ ;)

    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Ampster
    Ampster Registered Users Posts: 174 ✭✭✭
    edited January 2019 #3
    Dave Angelini said:
    If you have shading you need another controller to keep from messing up the array in the sun.  This is the best way!
    ..............
    How is the area recovering from the fires?  Down here, every time it rains they close 140. Winter Storm warnings go up late tonight. Good times at 9,000+ ;)

    The Outback Skybox has a built in controller so I am not sure how that would work. Someone on another forum suggested i look into Tigo optimizers. They are less expensive and easily retrofitted to the panels. I have good access from below and I might only have to put them on the occasionally shaded panels.
    Regarding the recovery in Sonoma from the fires from last year I see a lot of new construction. There are a lot of lots for sale between new construction projects. I can also tell you it is hard to find a good carpenter to help me install a skylight. 
    8 kW Enphase micros AC coupled to a SolArk 12K
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,904 ✭✭✭✭✭✭
    #4
    Give it some thought, you are making it harder than it is. Good Luck. The tigo is a band aid for the best fix. I guess for grid-tie it is ok but we would never do that offgrid.

    I have heard ads on the radio for carpenters wanted. Pretty rare in the past, but now a common problem.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Ampster
    Ampster Registered Users Posts: 174 ✭✭✭
    #5
    Dave Angelini said:
    Give it some thought, you are making it harder than it is. Good Luck. The tigo is a band aid for the best fix. I guess for grid-tie it is ok but we would never do that offgrid.

    I am not sure I understand your drift. I am on the grid although you could consider the Outback Skybox off grid because it does not sell back to the grid. It is there for backup and to load shift my critical loads to off peak. The rest of the house is on the grid and I have a separate grid tied Solaredge system on a south facing roof that gets some shade in December/January. As I mentioned, the Outback Skybox has its own charge controller so I assume that is simpler and easier than adding a separate charge controller. The Skybox charge controller needs a minimum voltage of 250v so I don't think I have the option of paralleling some panels? I have one tree that I can trim and will do that before I install any Tigos. I also have a Nest camera mounted above the patio cover where these will be located so I should be able to watch output and any shading and only retrofit the Tigos where needed. Worse case, I can charge from the grid at off peak rates. 
    What easy solution am I missing?
    8 kW Enphase micros AC coupled to a SolArk 12K
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,904 ✭✭✭✭✭✭
    #6
    When I wrote about Skybox over 2 years ago,

    https://forum.solar-electric.com/discussion/351354/sweets-from-outback-power-systems#latest

    I was told there were 2 hv mppt's in it. Well that was a thing that got a haircut to 1 mppt.

    My point to you is the Skybox has a DC bus and that is what we used on a couple SE and SW arrays to virtual track the sun.

    Using a camera sounds goofy to me, if there is any shading on hv array it is not good and it is to be always avoided.

    I get that using a roof forces compromise. It is one reason of many that I never do this for offgrid.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Ampster
    Ampster Registered Users Posts: 174 ✭✭✭
    edited January 2019 #7
    Okay, now I understand the context of your recommendations. I live on a small lot and already have the camera set up. One of the benefits the camera gave me is I could high speed through the video on a sunny day and see where the best spot was for planting vegetables. That is how I knew I would see some shading. The camera will provide a secondary benefit as I tune this array. 
    My grid tied array already covers the best south facing roof. This is a patio cover that is facing west and is not optimum but, I only need a few hours of insolation to keep my batteries charged and to help shift my loads. My backup charging option is AC coupled from the grid tied system or at super off peak rates late at night. Also this array will be partially shaded by the building until Noon, so I am only looking at an afternoon window of insolation but that is all I need. I wouldn't spend money on new panels to do this but at $0.30 per Watt if this doesn't perform optimally the panels still will provide some needed shade. The patio trellis is being purpose built for this array. I already have the racking from another project and and the wood framing materials are costing less than $500. I will have to post some photos during construction. I do appreciate your input and particularly your confidence in Sun Power panels.
    8 kW Enphase micros AC coupled to a SolArk 12K
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,904 ✭✭✭✭✭✭
    #8
    My confidence in Sunpower or any panel for that matter is from when it is new. I buy my Sun Powers from a dealer who we trade favors.

    I would be very careful with used 330w Sunpower panels as they have been dumping their factory reject panels that for whatever reason to places like Sun Electric in Miami. They do not have a Sunpower Label. Lot's of very obvious defects.

    Make sure the panels you buy still have the Sunpower label on them and why they are being sold?

    I grew up in your area and have alot of old friends between Santa Rosa and San Rafael. The fire that burned the Burbank theater also burned the hotel we were in for a wedding 2 weeks before.

    Lot's of new snow at the Ski area in the park. If they could only lure the park people back from their free vacation.....
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Ampster
    Ampster Registered Users Posts: 174 ✭✭✭
    edited January 2019 #9
    Dave Angelini said:
    My confidence in Sunpower or any panel for that matter is from when it is new. .......
    Make sure the panels you buy still have the Sunpower label on them and why they are being sold?
    ........
    I have a good friend who is a SunPower installer in Southern California. He recently installed some new SunPower panels on my townhome in Hermosa Beach. He and I have talked at great lengths about how well these panels do over time. These 305 Watt panels were on an industrial building that was sold and new owner wanted them removed. Another friend of mine found them on Craigslist. The seller is ML Solar in Campbell, California and has good reviews on EBay. I pick them up tomorrow and will check each one as I load them on my trailer. Thanks for the reminder about the label. I realize it is a risk buying used panels but with proper risk management it can be an economically beneficial investment. This is not for the timid. Your mileage may vary. 
    8 kW Enphase micros AC coupled to a SolArk 12K
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,904 ✭✭✭✭✭✭
    #10
    I think you will be fine with ML. Good Luck any way.
    Sunpower is probably the best made in the commercial world. Amazing in the heat with output. Triple redundant wiring,and the most watts per square foot on a tracker or small array. For decades they were the only panel with a 25 year product warranty. Now, LG and Panasonic do that also and make some very efficient panels.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Ampster
    Ampster Registered Users Posts: 174 ✭✭✭
    edited January 2019 #11
    I did pick them up yesterday and as I loaded them I checked to see that they all had original Sunpower labels. I got a couple panels up today between breaks in the weather. I connected them in series and measured the voltage at about 3PM even though it was cloudy.  I got over 100 volts so I think they will work out great. My Skybox needs a minimum voltage of 250 volts so I should be fine with 8 panels. 
    8 kW Enphase micros AC coupled to a SolArk 12K
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  • Ampster
    Ampster Registered Users Posts: 174 ✭✭✭
    edited January 2019 #12
    While getting ready to pull the building permit for this I realize I need a Rapid Shutdown Device. The Outback solution is rather pricey. It would cost almost as much as my used Sunpower panels. One of the sales persons at our host suggested the Tigo RSD solution which comes in at around $400. The other benefit is, since I alread purchased 3 Tigo optimizers, I could get NEC 2017 compliance by the adding more optimizees.

     This project has taken longer than anticipated because the scope of the project has creeped. My significant other provided some design input including a new patio door and awning window. LOL.
    8 kW Enphase micros AC coupled to a SolArk 12K
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