# Best solar panel brands?



## Gresford (Oct 7, 2005)

I'm new to photovoltaics so I may not be wording this question correctly but I'm hoping that someone can help me. I am looking to purchase solar panels to add an array to my off grid generator system. Are there certain brands or types of solar panels that are more efficient than others? By efficiency I mean the ability to collect the sunlight for the most hours during the day regardless of the angle of the sun for battery charging and the quality of the panel itself. 

Thanks,

Gresford


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## mightybooboo (Feb 10, 2004)

I can answer regarding heat and efficiency.
In hot climes,nothing beats unisolar,they can even exceed ratings in hot areas(Why they are so popular in Australia),something unknown to other panels.Next best in heat are monocrystalline panels.
3rd for heat are multicrystalline panels.

You can put a bullet through a unisolar panel,so in that regard its also a winner.Unisolars cost more per watt,but then again at hot temps,they produce full output,others produce less than rated,so costs even out.Unisolars are larger sized per watt,if space is a premium,thats a drawback.

Unisolars only have 20 year gaurantees,the others usually have more.
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http://www.windsun.com/tech_tips.htm

Heat vs Solar Panel Output
All solar panels lose power at higher cell temperatures. This is why most panels are designed for 16.5 to 17.5 volts output at room temperature - when the panel cell temperatures get up to 150 degrees F or so, voltage output can drop as much as 20%. It is for this reason that we do NOT recommend the so-called "self regulating" panels, such as the Siemens SM46 or Kyocera KC35 for hot climates. These are lower voltage panels, and at hot desert temperatures, output can fall below the 13+ volts needed to charge the battery. In a typical solar panel, about 14% of the sunlight is converted into electricity, 7% is reflected, and the rest is turned into heat - this is why solar panels MUST have space under them for air circulation. It is also one of the reasons why we do not recommend the "solar roofing tiles" - since they are actually part of the roof, they can lead to tremendous heat buildup in the house.

Most amorphous, or thin-film, such as Unisolar and the Siemens ST series, have less power loss at high temperatures. Some recent measurements done here in Phoenix in the Summer showed that at an ambient air temp of 109F, that the Unisolar 64 put out about the same amps into the load as the Siemens SP-75, despite the 11 watt higher rating of the Siemens. If you plan on using solar where the cell temperatures will be high, such as the Southwest deserts, we recommend considering the Unisolar over the crystalline panels. The one problem with the Unisolar panels is that due to their overall lower efficiency, the physical size per watt is 50-60% more than a crystalline panel - however, if measured on an "area per delivered amp" basis, there is less difference.

Shade losses in PV panels
All panels, regardless of what the advertising says, will lose considerable output even if only partly shaded. Some, such as the Unisolar panels, lose less in partial shade, but the output is still reduced. In crystalline panels, when a cell is shaded, it essentially "turns off" that cell, turning it into a high resistance. If a single cell in a panel is shaded, it can reduce or even completely cut off the output of the panel. In some cases, it can also result in overheating of the cell as the unshaded cells try to force current through the high resistance cell. Unisolar panels are less susceptible due to built-in bypass diodes on the cells, but will still lose up to most or all of their power with 15-20% shading due to the voltage dropping below the battery voltage.
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BooBoo


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## Jim-mi (May 15, 2002)

I have a rack of 8 Uni's--- really like them.
Unfortunately the vast majority of Uni's product is going overseas.
They are really getting top dollar over there.

Hopefully in a year when Uni's new plant is on line we may see *some* product here.


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## WisJim (Jan 14, 2004)

I have some old Sovonics panels, which are now Unisolar (but correct me if I am wrong, Jim-mi), and they are about 20 years old and haven't worked for years. I hope that they have improved over the years.

My 25 year old Arco panels still work well, my others whose name I forget, but are no longer sold in the USA are great, and I bought Kyocera panels a few years ago, and have no complaints. And they occassionally put out rated output or even a bit more.


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## Gresford (Oct 7, 2005)

WisJim,

Is it uncommon for solar panels to put out the rated output?


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## Jim-mi (May 15, 2002)

PV pannels are rated/tested in lab conditions.
Out in the real world these "lab conditions" are not often met.
For a long while the manos rated pannel's way high........some mano's worst than others.
Finally, after being called out, most all mano's are putting on (their PV pannels) more realistic ratings.

Wis-Jim, ya I've got a couple of the old Uni 22 watters.......they will do a good job as a Trickle charger...and no more. The other two were, I believe, zapped by a near by lightning strike.

I can only hope that the newer generation Uni Solar 64's have a longer life.

Yes my old Arco vintage pannels are still going just fine.
Speaks well for 27 ??? year old PV pannels.


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## mightybooboo (Feb 10, 2004)

Jim-mi said:


> PV pannels are rated/tested in lab conditions.
> Out in the real world these "lab conditions" are not often met.
> For a long while the manos rated pannel's way high........some mano's worst than others.
> Finally, after being called out, most all mano's are putting on (their PV pannels) more realistic ratings.
> ...


Yep,hard to beat monocrystalline panels for proven durability.
I have bp-75 panels,they are nice!

A monocrystalline is panels that have individual cells wired together.Multicrystalline are like the Blue Kyoceras,another fine brand of panel.
Unisolars are called thin film or amorphous panels.They can be flexible or solid frame mounted.The verdict isnt in on longevity yet,unlike mono or multi crystallines having proven durability.

BooBoo


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## Jim-mi (May 15, 2002)

Gotta add this; All the pv that comes out of Japan (that I am aware of) is pretty good stuff.

There is new pv comming out of china that has, as of yet, no track record.
Can they(china)--will they-- make something with any degree of quality ------------stay tuned.


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## joe (Jan 12, 2006)

As far as efficiency goes, this company's products seem to be pretty good: http://www.greenandgoldenergy.com.au However, it is an Austrailian company, and their products are new, so availability may be a concern. Also, it is a tracking collector, which means there are more possibilities of things to break. I would tend to go with a flat panel, proven product like those produced by BP, Kyocera, etc. Of course, we are assuming you mount the system in a sunny location, free from shadows, etc.

All in all, I think that the bigger issue is in the battery system, and whether you are willing to run a generator occasionally.


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## jnap31 (Sep 16, 2005)

Some folks are waiting a few years for the more efficient and cheap nano solar technology to be mass produced before buying solar cells


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## mightybooboo (Feb 10, 2004)

jnap31 said:


> Some folks are waiting a few years for the more efficient and cheap nano solar technology to be mass produced before buying solar cells


Bet they produce 3 times as much power.....for 3 times the cost.
Too much politics,but I'd like to be wrong.

BooBoo


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## WisJim (Jan 14, 2004)

jnap31 said:


> Some folks are waiting a few years for the more efficient and cheap nano solar technology to be mass produced before buying solar cells


Some folks have been waiting for prices to drop tremendously for decades. Remember some years ago that "in a few years PVs will be $1 a watt for panels"??

I suspect that any big "breakthrough" is going to n eed lots of start up money to get in production and even if such a breakthrough really happens, it will be a long time before less demand forces a seller to drop their prices very much. Demand is what keeps the price up, in my opinion.


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## zant (Dec 1, 2005)

I was reading on another forum about someone buying pv panels from china :nono: thye were commenting that they were lokking for a good silicone to seal them because the info on them said they may delaminate if outside..***..these were brand new out of box..where else would pv panels be..When are people going to smarten up and not buy chinese crap just because it's chaep-quality is always worth the extra cost....I have 25yr old arco's that aren't delaminating..makes you wonder :shrug:


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## WisJim (Jan 14, 2004)

There was a dealer or distributor for Chinese pv panels at the Wisconsin energy Fair last June--they were out of brochures by the time I got to their booth, and didn't have much to say about their panels, AND their "retail" prices quoted at the booth were higher than the prices I was quoted by the local Kyocera dealer at his booth, and I could have loaded Kyocera panels into my truck within an hour if I had the money at the moment--he had a good stock. No idea what delivery was on the Chinese panels. I think I will stick with something I know. My Arco M51s turned 25 this summer, too, and are working fine.


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## Jim-mi (May 15, 2002)

Anybody with any dought
PLEASE
go reread Wis Jim's last post.

Good stuff.



(I talked with the same guy at the fair)


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