Positive ground Sunpower 327 watt T5 solar panels

TheAppleTreeGuy

Howdy folks, Long time reader but never a poster. I have read countless hours and clicked on a million dead links about this issue, as I hate to waste anyone's time... but we could really use advice. 

We bought a few thousand used Sunpower T5 style 327 watt solar panels not knowing they are "positive ground" panels.(SPR-E20-327-COM-LAM SUNPOWER T5-SPR-327 are both model numbers exactly, but they seam to be exactly the same panels physically)  These are the composite/fiber/plastic frame panels that hook into each other on a flat rooftop for easy installation. I have talked to and emailed back and forth with an engineer from Sunpower and they just repeat that no equipment was tested on these panels besides being hooked up to transformer style inverters, which are no longer manufactured for single phase power. Most of their catalogs have been lost or unable to look up for me. 

1) How do you ground/earth the frame of a plastic solar panel?

2) If hooked up to a normal transformer less inverter, does this do any damage to the inverter or panels themselves? What is an estimated loss of power when doing so... I have read peoples opinions as a 3% to 50% loss, but with no reason to their numbers. Someone answered that they knew I needed a "pid box" to use these properly but did not know what it actually meant. Hey, it's a lead!

3)Would these lose power on an charge controller off-grid system just as much? 

I've seen these for sale on ebay before and now assume that the seller/purchaser does not know about this grounding issue. There are millions of these panels coming out of service shortly and I would love to have accurate information for the next person that gets into this situation also. I appreciate the help to whoever can help point me in the right direction! 

BB.

I do not believe that the "current crop" (say later than 2008, and possibly eariler) have the "positive grounding" requirement.

Note that there was never any issue of damaging the panel(s)... It was just they built up a internal charge to the solar cells themselves that caused a loss of harvest. If positive grounded, the internal charge was bled off and things went back to normal (even if was negative grounded, connecting to positive ground was "fix" the problem--In hours or a few days, I don't remember).

At some point in production (at the time), Sunpower did include a sticker on the back of the panels saying to positive ground...

Here is a thread with some information:

https://forum.solar-electric.com/discussion/3518/sunpower-positively-grounded-modules

This post has some quotes on the grounding issues:

https://forum.solar-electric.com/discussion/comment/35704#Comment_35704

And Dave A. posted a copy of a paper detailing the issues:

https://forum.solar-electric.com/discussion/comment/403142#Comment_403142

At this point, unless you are buying 15 year old original panels, I don't believe that this is an issue anymore.

Regarding grounding... You cannot ground a plastic frame. However, you can ground the metal rails holding the panels per NEC rules. If a panel (or wiring) fails shorted to the structure (or you get a lightning strike), then the grounding still performs its job.

For installation instructions, Sunpower has a PDF:

https://us.sunpower.com/solar-resources/sunpower-solar-panel-safety-and-installation-manual-dc

Following the Mfg's instructions is always a good place to start (and usually UL/NRTLs require installation instructions). Originally, Sunpower only marketed to installers and not to DIY self installations--So some information was hard to find years ago.

Also, be aware, Sunpower seems to be a common name in the industry (or some version of sun power)... Make sure you are looking at the exact brand/model number of panels to be sure you have the correct information.

-Bill

TheAppleTreeGuy

Wow that's for the fast and in depth response. I waited a few days to respond as I had to take in all the new information. 

B.B. If you believe that positive ground panels don't get damaged by running them like a normal panel, that's what I'm going to do. 

These Panels are listed in one of their old advertisements with the date code of 2012 on the bottom of the paperwork, so that means they are less than 10 years old... but not exactly sure their true age. 

As per Sunpower, their response for how they label their panels for grounding either negative or positive is in this small chart. 

I do have a pdf copy of the T5 install manual that the engineer said it took forever to find, if I have a place to host it I'll put that on here and hopefully that helps anyone else in the future. I know there are boatloads of these panels coming out of commission eventually and I would like to help people get the correct information about them being that Sunpower doesn't seam to support them. Pretty sad being they advertise to be the best warranty/support solar manufacture out there. 

I will attach that PDF on this post but I am not sure if they stay here forever. 

Thanks for your help and confidence! 

BB.

Note: I am not in the solar industry and do not work for Sunpower... I have no personal experience with these panels.

All the statements I have ever found (see old documents/links), say they loss in power by negative grounding a "positive ground required" set of panels does not cause permanent damage. And the loss of output can be "fixed" by connecting in a positive grounded system.

The loss of power output is (can be?) significant--So one would normally not install "positive ground required panels" in a negative grounded system.

Are you saying that, via model numbers, that you have "ground agnostic" panels from Sunpower and will install them in your negative grounded system... Or that these are PGR (positive ground required) panels and you are going to install them in your negative grounded system?

And thank you for the updated information/confirmation of model/part numbers that are PGR. Hopefully that will help others as (possibly) these older panels are removed from service and make their way into the used market.

-Bill

Dave Angelini

I have 5 or 6 sources that email regular stock (new and used)  to me over the years. I am in a group of pro installers in the US, Caribbean and the + ground panels are long gone!
  
It is good that the OP is concerned but frankly I have not seen any of these panels talked about or sold in over 10 years.
They are often smaller wattage panels and less than the 327 watt and up that are current SunPower models.

The only thing I ever see is someone looking for an Inverter to run positive ground for an old array with the + grounding.
In most cases the array is replaced if they can't find an inverter.

One owner wrote me many years ago how Bill (moderation man) saved him thousands of dollars with his SP array. It never surprises me how lucky we are here.

Other premium panels on the market often reverse engineered SunPower panels as they were built far better than anyone else.

SunPower panels had amazing performance in hot desert conditions where the MPV often declined on the competition. They also had triple foil junctions that gave you two cell connection failures before the third took the cell out.

Other things also, along with still being installed by a large company that was made up of Ex US military guys and gals.

TheAppleTreeGuy

You guys are awesome, thanks for the help and opinions again. 

As for the panels themselves, They are a little awkward themselves as the plastic frames are meant to mount to each other on a flat roof. Most people make their own brackets and figure out a way to mount them to pipe or poles. 

At this point I just want to make sure anyone that has these exact panels will know what to expect and to know if there is any loss of power that they can do something about it still. 

My current (haha) system I put up is 46kw of panels to 37.7kw of inverters, single phase. If I remember right I got about 55kwh a year last year. I call that an $8000 offset of power, or $6,000 they pay for surplus of power if I sat back and just a lantern and shut all the fun energy gobbling stuff off (what homeowner doesn't run 6 freezers, a hot tub, a walk-in cooler, and a freeze dryer?) They charge us an average of 13c/kwh and pay about 10.5c for any surplus on net metering. I did that entire system a few years ago for about $30k, using a lot of used oil drill pipe, used panels, cheap inverters, and really cheap beer. 

BB.

With your newer, no positive ground required, you will just have the usual losses over the years. Worst case, something like 20% losses over 20-25 years...

However, remember that you are looking at 75-77% of "name plate" rating because panels are rated at ~25C (77F) under "flash sun lamps"... And reality, panels can see upwards of 40C over ambient on hot/sunny/windless summer days--Which is almost 20% (actual temperature of cells at that moment of time) and 5% or so losses in inverter/charge controllers... We use 75-77% loss for new panels--Just to avoid being overly optimistic with "marketing numbers".

Yes, panels in subfreezing weather with snow on the ground (for reflection of sun) can see >100% rated output--But most people do not live in such cold areas.

And, frankly, unless you have lab grade meters and reference sources to measure solar energy--You would be hard pressed to accurately a 10% "loss" in day to day operations--The variables are just too many (between equipment, atmosphere, etc.) for an average user to quantify.

The thing I do worry about are panels that have plastic construction (vs glass and aluminum)... Many panels do not last much longer that 5-7 years and as little as 2 years (such as "flexible" panels marketed to boaters and RVs) before the plastics fail.

I don't know anything about the Sunpower with plastic frames--Perhaps they are a better construction.

I guess you are in Minnesota... Just keep an eye on power costs and what is happening with your state public utility commission rules for GT solar... Your State PUC can easily wipe out your solar power business business model with the swipe of a pen (you may be grandfathered for 10 years--Or not).

Things like this have happened in several states, and even parts of Canada (in California, we are looking at $0.40 to $0.50 per kWH power costs, and for "new GT solar" something like $0.085 per kWH for "excess power" produced (i.e., kWH produced in summer was credited for use to offset winter bills).

PUCs are a political animal. And political winds (and engineering/business cases for utilities) change over time. When GT solar was "small" (less than 5% of power generation), then GT Solar Subsidies were rounding errors. Today in some states we are >10% of power generation--And the subsidies (and grid stability) can no longer be ignored--And we are seeing those now in the form of weather/and other issue caused blackouts.

-Bill