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-   -   Best solar panels for the buck (http://www.sailnet.com/forums/electrical-systems/82573-best-solar-panels-buck.html)

prroots 01-10-2012 06:41 AM

Best solar panels for the buck
 
I have been looking at generators. Now I'd like to consider solar panels which offer huge advantages such as no moving parts, quiet, reliable and non-flammable. I'd like to satisfy on average 120 Ah/day (in Florida) as an initial starting point. From what I've read so far that may require three 120 Watt panels or two 180 Watt panels. It seems that the $/watt would be considerably less in the latter case. I would very much appreciate recommendations for types of panels and charge controllers that are reliable and cost effective. Thanks
Pete

kd3pc 01-10-2012 08:24 AM

the bigger question with panels, is where you are going to mount them...that will drive the size and mounting style...at that point you can shop $/watt...doing it the other way will force you in to an installation that may be substandard, won't work, safety hazard, etc.

Hamilton Ferris is a good place to start.

Blue Sky MPPT controller are well respected and will provide the things you need in a reliable package.

None are cost effective, unless you NEED solar...and plan to keep using them for years. I would suggest that you would need 4-6 years of full time use to break even...as compared to other systems. Nice part is they are very quiet when compared to wind or generator.

They do work, we used two 110 watt panels on our previous 42' and were quite happy, since the new owner did not want them, they currently supply all the power for our 25' RV.

aeventyr60 01-10-2012 08:04 PM

You won't go wrong in buying Kyocera solar panels. had them on my boat for 12 years...still putting out lots of clean power.

prroots 01-11-2012 01:21 PM

I've been searching for panels and controllers. One thing I've learned is that panels come with nominal voltages (eg, 12, 18, 24..). Any of them will work with an MPPT controller. The Kyocera 185 I stumbled on for $300 is not a nominal voltage; it is actually somewhere between 12 and 18. When I called Blue Sky they said that their controllers automatically determine the nominal voltage of the connected panel and in the case of this panel it would select 18 even though that was not the case. He said that if I could find a 12 volt panel I would accrue two advantages compared to the Kyocera 185 as follows:
- the controller would work more efficiently; he guessed 5%
- the controller would be cheaper (ie, 2512iX vs 3024iL); about $150 savings

Comments appreciated.
Pete

aeventyr60 01-11-2012 10:46 PM

All the panels I've ever worked wth put out considerably more then 12v....these Kyocera's I have are 16.9 VpMax and VOC of 21.5......

mitiempo 01-12-2012 01:11 AM

Pete

Most panels will output about 17.7 volts + or -. Probably the most popular large panel for boats is the Kyocera 135 watt which has a max output of 17.7 volts. Kyocera KD135GX-LFBS 135 Watt 12 Volt Solar Module Either controller you mention will work well - the 2512iX accepts voltage up to 35. With multiple panels wired in parallel there should not be a problem as long as the controller's max amperage is not exceeded.

What output voltage is the panel you are looking at?

prroots 01-12-2012 05:54 AM

Quote:

Originally Posted by mitiempo (Post 815779)
Pete

Most panels will output about 17.7 volts + or -. Probably the most popular large panel for boats is the Kyocera 135 watt which has a max output of 17.7 volts. Kyocera KD135GX-LFBS 135 Watt 12 Volt Solar Module Either controller you mention will work well - the 2512iX accepts voltage up to 35. With multiple panels wired in parallel there should not be a problem as long as the controller's max amperage is not exceeded.

What output voltage is the panel you are looking at?

Here are the specs:
Quote:

Max Power: 185W
Open Circuit Voltage (Voc): 22.3V
Short Circuit Current (Isc): 11.2A
Maximum Power Voltage (Vmp): 17.9V
Maximum Power Current (Imp): 10.3A
As you can see the Voc is only 22.3V and both of those controllers referenced are good up to 45.6 Volts. The 2512iX has a max current of 20 Amps, but as you can see the current output by two panels in parallel is 22.4. The tech rep from Blue Sky said that would be fine ie, the controller can easily handle it. I believe that there is a 25% margin built in due to the NEC, but we're only exceeding it by approximately 10%.
Pete

prroots 01-12-2012 06:00 AM

Quote:

Originally Posted by aeventyr60 (Post 815746)
All the panels I've ever worked wth put out considerably more then 12v....these Kyocera's I have are 16.9 VpMax and VOC of 21.5......

When they quote the nominal voltage of a panel they are not referring to the actual panel output Voltage; it's more like a match up. For example, a nominal 12 Volt panel typically has 36 cells and is a good match for a 12 Volt battery system. That's because of the need to charge at up to 15 Volts and allow for various losses along the way. Of course, with the advent of MPPT charge controllers one can match a much higher Voltage panel to a 12 Volt battery system. I was first made aware of this definition when trying to use the Blue Sky controller sizing bulletin (http://blueskyenergyinc.com/uploads/pdf/100214.pdf) to find the proper size controller for a given pair of panels. Both sizing tables refer to the nominal panel voltage as 12, 18, 24, 36, and 48. This, of course, begged the question what is the nominal voltage of a panel.
Pete

mitiempo 01-12-2012 10:25 AM

I would buy the larger capacity controller - saves a problem if you ever add another panel.

prroots 01-12-2012 11:13 AM

Quote:

Originally Posted by mitiempo (Post 815868)
I would buy the larger capacity controller - saves a problem if you ever add another panel.

Thanks. Unfortunately, we have no additional space. On the other hand, if these panels had to be replaced for any reason, the larger controller would give me more flexibility in selecting panels. However, this is a budget project and the less expensive controller will significantly reduce the overall price. It's all about compromises

You mentioned the Kyocera 135 which is a nominal 12 Volt panel. I just learned that that panel is so popular that they have been making it for years. Thus if I went that route and ever had to replace a panel, I would likely find the identical one. This is certainly not the case with all panels. I would love to find something around 185 watts, preferable in the 12 Volt size, that has had a long production run. Any suggestions?
Pete


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