I came across into Sunpower solar panels which I found interesting due to their color (black) and extremely high efficiency. By first look they seem OK panels (UL Listed, 25 year warranty, etc...). So, is there a catch?

In addition they have seem to have some inverters that seem to be on par with Xantrex GT-series.... didn't read the specs very carefully yet, but I might if I was on the market purchasing inverter.

http://www.sunpowercorp.com/home.html

Anybody has any comments, suggestions?

Sunpower has been successful in getting their high efficiency (22%) panels on a lot of west coast rooves where space is more of a premium over cost. A part of their high efficiency is derived by mandatory wedding of their inverters. They've inked a very large deal with PowerLight right in their own backyard (N Ca) and have several deals with other very large installers around the world in the works. They have no problems in moving all of what they manufacture, which will be expanding greatly in capacity very soon.

So, besides giving a thumbs-up for Sunpower panels, what I'm also trying to say is that you better be a VERY BIG solar installer in order to:
1) Talk to them
2) Get your hands on any panels (after they've taken care of their other large clients)

FYI: I'm confident enough in the company's future that I'm a (small potatos) shareholder - SPWR

SunPower resells the Xantrex GT inverters under there own label, as does GE

15 months back, when I was specifying my system, I narrowed it down to SunPower or Sanyo panels because of their high efficiency and my limited space.

Unless something's changed, SunPower panels have a positive DC ground. That's why they will only work with specific inverters. Since the life of the panels will probably exceed that of the inverter, and I didn't want to be tied down to one model of inverter, I decided to go with Sanyo.

That said, I know the guy who runs one of the largest PV installers in California, and he puts in SunPower.

Sanyo panels will give you the same efficiency, but the frames are normal aluminum.

How can a panel, have any kind of ground on either output. That would prevent panels from being wired in series.

Only the frame should be grounded, AFIK, and both power leads should be isolated from anything.

Maybe the bought a bunch of pos gnd inverters, and needed a way to market them, and "invented" + gnd panels ??

I've talked to SunPower about this issue and it is apparently a fact of life for the panels they build. A bit of patent/Google research brings up some material that appears to explain the reason (at least if you have a smattering of semiconductor physics in your background), but I'm not going to attempt to summarize (mangle), the technical details here. At least some of the stuff I found seemed to suggest that this may not continue to be the case for newer versions of the basic back-contact technology, so this limitation may disappear at some point. I haven't asked them about this possibility, however, so this is merely speculation on my part.

ok i won't quote you, but what makes you think it will change to allow other than + grounds and why?

I will cross link this thread with one on Wind-Sun forums... Somebody had some questions about SunPower panels and I found a couple of links that explain, in detail, the issues and why they require positive ground.

http://www.wind-sun.com/ForumVB/showthread.php?t=1458

There is a pretty detailed paper (PDF file) that describes the issues and solutions for their particular rear contact construction:

http://www.solarsales.com.au/download/polarization_paper.pdf



Buried in the paper (2005?), was this quote:



I don't know if this process ever made it into production or not...

-Bill

yes bill i am aware of the technical end of the pvs as i believe i brought it to the attention of many people. now i wasn't aware they were planning on putting the standard front connections to try and i don't know if they did do it or not(maybe somebody will find out?)
where i was really going was with the grounding of other equipment such as the controllers and inverters. at the risk of saying it when it comes to the option of grounding + or -, does the equipment go both ways?

Niel,

I am guessing that they did not modify the panels--SunPower still seems to require positive grounding.

Not quite sure of your question. On my Xantrex GT inverter, it appears to be just a stuffing option (where the fuse holder is stuffed on the PCB) as to whether the unit is positive or negative grounded (negative ground is the "standard" unit, and the positive ground an option).

From an engineering view--the DC to AC connection is completely isolated and either grounding (or even no grounding, just use a high value resistor to bleed off static charge) will be functionally equivalent (other than for SunPower's requirement).

As I posted in the other thread, there is actually a reason to choose positive grounded systems... There are fewer corrosion issues (a positively charged wire wrt ground will corrode if not completely insulated from dirt/etc.--A negatively charged wire wrt ground, will quickly corrode away--hence the reason telephone systems are positive ground and cathodic protection systems for pipelines and such).

http://www.windsun.com/CP_Stuff/cp-index.htm Cathodic Protection

But there is the problem that many items these days (especially 12 VDC automotive items) have negative grounded cases--In a positive ground system, these cases would be hot wrt ground and a danger for accidental shorts to earth grounded components.

However, I have a feeling I still did not quite understand your question...

-Bill