Solar - Best Prices?

[kirsi]

I am near Stuart Florida. Where is the best price for a panel about 140W? Someone mentioned picking them up. Is there a difference in the size vs quality? How are grape ones? Thanks

[geoleo]

google Flagstaff AZ and kyocera

[Sumner]

Originally Posted by kirsi

I am near Stuart Florida. Where is the best price for a panel about 140W? Someone mentioned picking them up. Is there a difference in the size vs quality? How are grape ones? Thanks

A friend got his here...

Solar Panels, PV Systems and Inverters Distributor

...not to far from you and they had great prices.

We have gotten ours here....

Solar Cell, Solar Panel, Renewable Energy, Wind Energy, Charge Controller, Solar Trackers - Solar Cell, Solar Panel, Solar PV, Solar Products, Charge Controllers, Solar Trackers

...and have been happy with the pricing and service and the panels.

All of these places have different voltage panels so be aware of what you are buying and how they will work with a charge controller. Most likely you are looking for what are considered 12 volt panels (17-18 volt operating voltage).

Sum

[kirsi]

Thank you very much. I can pass it on to others here at the marina looking to upgrade.

[neelie]

A bit of thread drift here, but almost on topic.

How do they measure efficiency of a panel?

Is it W/Sq M?

I see some listed at 14% and some listed at 21% - this seems a wide range for what is ostensibly the same material and the same technology.

I also notice that the larger panels have greater claimed efficiencies and also greater output voltages - is there a correlation?

Furthermore, price per claimed Watt does not always correlate with the claimed efficiency - this is counter intuitive (at least to me)

Is it worth chasing down the last 1/10th of percent of efficiency or is this number just a marketing tool with no value in the real world?

[gettinthere]

Look into e marine in Ft. Lauderdale. Wide variety of panels, mppt controllers, many wind gens plus mounting & installation hardware too

[Dsanduril]

Neelie,

Efficiency is measured by shining a light on the panel at a level of 1000 Watts per square meter, and then measuring the power output of the panel. If the power output is 140W (for a one square meter panel) then the efficiency is 14%, if the power output is 200W then it is 20%.

You may see two efficiency numbers, the cell efficiency and the panel/module efficiency. The cell efficiency is tested by just measuring the actual solar cell output, the module efficiency includes all the dead space (space between cells, frame, etc.) on the module that is a combination of many cells and so will always be lower than the cell efficiency.

Higher efficiency only means that you can squeeze more power out of the same area. A 140W panel is a 140W panel. If one is more efficient than the other then it will be smaller. So, if you have limited space (most boats), higher efficiency will allow you to get more power out of the same amount of space. Within reason go for higher efficiency, but you will have to do your own cost/benefit analysis to figure out where "within reason" falls.

On the "same material" note, even if you only look at silicon, and set aside all the other cell types, there is a wide range of efficiencies because there are a lot of variables in design and manufacturing. Sunpower, for instance, uses "back side contacts". If you look at most panels you'll see a network of wires on the front face that collect the electrons. These, being between the sun and the silicon, reduce efficiency but are easier to manufacture. Then there are the silicon "dopants". None of the silicon is pure, the manufacturers deliberately introduce impurities that are intended to reduce the resistance to the flow of electrons. These formulas are closely guarded secrets. Some dopants are quite expensive and quite difficult, others not as much. The mix in these formulas is probably the largest difference between efficiency measurements. Then there's the glass (or other substance) on the front of the panel, what are its light transmission characteristics (and associated costs)? Lots of variables in the mix.

Each manufacturer will tell you theirs are the best, and some modules have benefits in terms of low light performance, or construction, or... but for the most part you can just look at the rated power output to compare modules/costs. Being aware that you will never get that power from the panel. For best comparisons, see if you can find (and then use) the NOCT power ratings for the panels. NOCT = normal operating cell temperature and is a better reflection of actual panel output that the STC (standard test condition) rating that is what is advertised. You'll see some panels drop more from STC to NOCT than others, you want the higher NOCT rating, especially if you will be installing/traveling in the tropics.

[neelie]

Dsanduril:

Many thanks - that was a great explanation. I have one more question.

In an effort to shorten the short list, I'm thinking of making up my own "efficiency quotient" which will be: NOCT power rating divided by module footprint area.

Is this a sensible way to narrow down the search?

Of course, I Understand that there are other many other variables to be considered in the decision making process.

[Dsanduril]

Actually that makes a lot of sense as a metric for sorting out modules. Should give you a pretty decent way to judge modules and compare prices.

[neelie]

A useful website for those researching solar panels:

Solar Panel Efficiency Comparison | SRoeCo Solar

[myocean]

Two more question to discuss:
1. Are there big difference in corrosion resistance? (Are the high end panels, e.g from SunPower or Sanyo very well suitable for yachting)
2. Is it better to use smaller panels with small surface area instead of larger ones in oder to have more mechanical stability?

[neelie]

and another... Compare Solar Panels

[neelie]

Myocean.... Everyone seems to use Kyocera, they have the good reputation for being more robust in the marine environment.

As far as stability goes, this is more a function of the base / mounting. On an Outremer, you will have no problems with a getting a good stable foundation to mount the panels - you have hectares of flat roof!!!.. Lucky you.. More panels have the potential to minimize losses due to partial shade. But then you will have many more connections and these are always the weak point.

Two days ago,I was planning on 4 x Kyocera 140W panels, today I am trending towards 2 x Sanyo 225 W for aesthetics and reduced windage. Tomorrow?? Who knows. There are so many variables.

With a mono, there is always the danger of building an array so big and ugly that you look like an oil rig and helicopters will try and land on it.

[Dsanduril]

I find this site pretty comprehensive:

Solar Panel Database

The link is sorted by efficiency from high to low, but you can sort by any of the columns. Quite handy.

It still fails in terms of using STC ratings, but is a good starting point.

[Mirar]

Hello, I have ordered 5 of the 130 Watt panels from www.windtubine.ca on Vancouver Island. They are rated at something like 44 volts for my 24 volt system. Of course I plan on MMPT controllers to deal with the excess voltage. I am getting these for around $1.19 /watt. Check out Kevin's website, he has sold hundred's if not thousands of panels. All panels are around the same price/watt. No financial connection what soever.
Greg