What I'm asking is how much difference in output, reliability and longevity between different manufacturer solar panels .... in an RV application? Are there any brands that are head and shoulders above the rest?
I know that most people on here say if you need more solar .... just add some more panels .... but in my case, I need to maximize what I am getting per square foot.
I would also like to do the best I can to minimize the effects of shading .... do diodes really do any good .... are there any Mfg who do a good job of this and do they test to really work in partial shading?
I am thinking I would like to use higher voltage panels and MPPT controller to reduce current from the panels .... but parallel would be better for partial shading .... maybe parallel higher voltage panels?
What I'm asking is how much difference in output, reliability and longevity between different manufacturer solar panels. Are there any brands that are head and shoulders above the rest?
Sunpower has a very good reputation on all three fronts, they have some features that make them stand out, but not "head and shoulders above the rest"
I know that most people on here say if you need more solar .... just add some more panels .... but in my case, I need to maximize what I am getting per square foot. I would also like to do the best I can to minimize the effects of shading
I am in the same boat as you, watts / sq ft, and performance in variable less ideal conditions (partial shade) matter to me. We are the exceptions to the "a watts a watt, don't waste money on high efficiency panels" wisdom (which holds true for most situations).
do diodes really do any good .... are there any Mfg who do a good job of this and do they test to really work in partial shading?
Yes. I am not an expert, but I've been doing my best to learn about this (its hard to find info since partial shading is a secondary or non-concern for most stationary installations).
So far, the brands that stand out to me in terms of partial shading performance are Sunpower and Rec Solar. Of those two, Sunpower seems to have the advantage in overall efficiency of their panels in unshaded conditions. They have different methods of addressing partial shade.
Rec Solar's Twin Peak line uses half cut cells which splits the panels into 6 sections (as opposed to 3 sections for traditional panels) meaning if only one section is shaded that's a theoretical 17% loss of output as opposed to a 33% loss for a standard panel, Or if shade affects the 1 entire short side of the panel the half cut cells would lose 50% whereas the traditional panel would lose 100%. I believe their may be other companies that use half cut cells, but Rec Solar is the brand I'm aware of and I believe the originator of the concept. Here is a (marketing) video that explains the advantages of half cut cells
Sunpower's technologies that make them well suited for partial shade are a bit less straightforward, and I can't adequately explain them here. If you read through the threads I link to at the bottom of this post you can learn about some of them. They also make use of bypass dioes (the P-series uses 6 like the Rec panels (but all in a lengthwise orientation), The solid copper backing (IBC), low reverse bias voltage, smart use of bypass diodes, and high efficiency make them suitable for mobile use in terms of shading performance, durability, and space efficiency. This is a marketing video but it highlights some of the technologies and shares some apparently independent partial shade test data.
Yes. @Carly posted a picture that does a good job showing both the advantage of bypass diodes and of the half cut cells.
I am thinking I would like to use higher voltage panels and MPPT controller to reduce current from the panels .... but parallel would be better for partial shading .... maybe parallel higher voltage panels?
Yes, this is what I plan(ned) to do (now my plan involves multiple small MPPT controllers but the same principle of high voltage panels in parallel still mostly applies)
Sunpower's X series panels are 96 cell panels with a Voc in the high 60's, and some panels (can't remember which brand) are pushing 100V per panel.
Another thing worth noting is that the focus on voltage drop and line efficiency from panels to SCC is somewhat more relevant to stationary builds than mobile builds (where wire runs are usually quite short so (1) losses are less, and (2) oversizing the wire to compensate for losses is cheaper).
I have asked similar questions and started relevant posts to yours at various points in my research there is some good info in some of them, check them out:
I’ve got one sunpower 327w 60v mono panel on the roof of my small cargo conversion into my MPPT and out to a 12v 100ah LiFePo. The higher voltage really comes through on cloudy days when the voltage remains high enough to produce a good charge. On a good sunny day I get 5.5amps into the CC and the MPPT uses that extra voltage to produce 17-18amps to the battery.
I did buy a second identical panel ground mounted that I use to do the same thing for my garage lights outside lighting and power tools on a second LiFePo battery.
Kinda wish I’d bought a few more now at $100 ea. They went quick up at santan solar.
