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Old 11-01-2012, 06:38   #16
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re: Best Solar Panels For The Buck

I'll second Solar Blvd. for value. They were recently having a sales on some of their panels.

http://www.solarblvd.com/Solar-Panel..._25/index.html
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Old 11-01-2012, 06:56   #17
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re: Best Solar Panels For The Buck

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Originally Posted by vientoman View Post
Iv'e noticed that they seemed to have felt the need to extend the decks in order to grab more sun. Not to be overly critical, but seems like a bad idea from the standpoint of compromising the seaworthiness of such a vessel. You wouldn't want to catch yourself in any sort of actual sea conditions. However, I imagine the primary function of such a vessle is to motor around various ports showing off the million dollar array of panels.
They can be pulled back in in rough seas though.

And they wanted to do this to show boaters it can be done. A lot of people don't believe in theory.

I do like the catamaran design of that boat and the wave piercing & SWATH features.

As for the solar panels, I got mine from sunelec.com
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Old 11-01-2012, 07:41   #18
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re: Best Solar Panels For The Buck

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Hmmmm . . . Sanyo 225w vs Sun Power 240w--which is better?
All things considered, the Sanyo technology is better. But that would you consider best, a 200 watt panel @28Vdc or a 200 watt panel @ 56Vdc? Obviously the 56V version as the amperage output is double that of the first. My choice Sanyo "HIT-HIP" technology. The best bang for the buck, HIT195 @ 56V (3.5 amp) for <$350.00 which is less than the 225s.
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Old 11-01-2012, 08:21   #19
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re: Best Solar Panels For The Buck

Close to a dollar a watt thats incredible.

The solar ships were to prove it could be done. Thats about how many panels are needed to power a boat with electric drive. Any less than that and you have to either cut speed, or charge for several hours for every hour of runtime.

If you could fit just 10 of those panels on a boat, you could toss the generator.
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Old 11-01-2012, 11:19   #20
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re: Best Solar Panels For The Buck

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
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Old 11-01-2012, 11:45   #21
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re: Best Solar Panels For The Buck

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All things considered, the Sanyo technology is better. But that would you consider best, a 200 watt panel @28Vdc or a 200 watt panel @ 56Vdc? Obviously the 56V version as the amperage output is double that of the first. My choice Sanyo "HIT-HIP" technology. The best bang for the buck, HIT195 @ 56V (3.5 amp) for <$350.00 which is less than the 225s.
SEAHUNTER A 200 Watt panel making 28 volts produces 7.14 Amps. A 200 Watt panel making 56 volts produces 3.57 Amps. There is no particular advantage of either 200 Watt panel. Since Watts equal Volts time Amps, at constatnt power output (Watts) doubling the voltage cuts the current in half. The controller will have to deal with the higher voltage however to get it down to around 14.4 Volts to charge batteries.
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Old 11-01-2012, 12:17   #22
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re: Best Solar Panels For The Buck

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Originally Posted by Tashtego View Post
SEAHUNTER A 200 Watt panel making 28 volts produces 7.14 Amps. A 200 Watt panel making 56 volts produces 3.57 Amps. There is no particular advantage of either 200 Watt panel. Since Watts equal Volts time Amps, at constatnt power output (Watts) doubling the voltage cuts the current in half. The controller will have to deal with the higher voltage however to get it down to around 14.4 Volts to charge batteries.
The higher voltage will have less loss in the cables, though (or smaller cables with the same loss) due to the lower current. I believe the controller will be somewhat less efficient with the higher input voltage (I'm assuming MPPT if you're paying for the deluxe panels, you'd pay for the deluxe controller). I wonder if the lower wire losses would offset the lower efficiency.
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Old 11-01-2012, 16:11   #23
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re: Best Solar Panels For The Buck

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Originally Posted by Tashtego View Post
SEAHUNTER A 200 Watt panel making 28 volts produces 7.14 Amps. A 200 Watt panel making 56 volts produces 3.57 Amps. There is no particular advantage of either 200 Watt panel. Since Watts equal Volts time Amps, at constatnt power output (Watts) doubling the voltage cuts the current in half. The controller will have to deal with the higher voltage however to get it down to around 14.4 Volts to charge batteries.
Yes, what cwyckham said. I appreciate your math but the thread asks what's the "Best solar panels for the buck". By going for the higher (double) the voltage (virtually the same amperage as the 28V version at 12V) at half the cost.
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Old 11-01-2012, 16:23   #24
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re: Best Solar Panels For The Buck

Seahunter, I think you're getting confused here. You ask:
" a 200 watt panel @28Vdc or a 200 watt panel @ 56Vdc?"
To which I'd say, 200 watts is 200 watts, period. But then you say:
" Obviously the 56V version as the amperage output is double that of the first"
And that's simply wrong. Watts is a measure of POWER, not Amperage. Amperage is a measure of CURRENT, not POWER.

The 56V panel does not have twice the amperage, it has HALF the amperage if it has twice the voltage but the same output power, as measured in WATTS.

And while there are some advantages to going to higher voltage (at equal wattage) there are some disadvantages as well. Some regulators won't take a 56V panel, they may max out at 40V. And if your regulator fails and you have a nominal 12V panel, you can still use the panel directly for charging. With a 56V panel if your regulator goes out, you're screwed till you can replace it.
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Old 11-01-2012, 16:45   #25
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re: Best Solar Panels For The Buck

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And that's simply wrong. Watts is a measure of POWER, not Amperage. Amperage is a measure of CURRENT, not POWER.

The 56V panel does not have twice the amperage, it has HALF the amperage if it has twice the voltage but the same output power, as measured in WATTS.

And while there are some advantages to going to higher voltage (at equal wattage) there are some disadvantages as well. Some regulators won't take a 56V panel, they may max out at 40V. And if your regulator fails and you have a nominal 12V panel, you can still use the panel directly for charging. With a 56V panel if your regulator goes out, you're screwed till you can replace it.
Yikes. Do it your way then. I do this all day long. A 56V panel at 14+ volt float is over 13 amps, something a 28V panel can't do. You're right they are different but the whole idea is VALUE. At half the price they are the best deal. There was no discussion about MPPT charge controllers, it was about the best value in panels.
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Old 11-01-2012, 17:00   #26
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re: Best Solar Panels For The Buck

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"what will it take to get "
Rule of thumb, as repeated by places like Sandia National Labs and a host of universities, is that you will get about 4x the nominal noon output of a panel, during the course of an entire day. More in Florida's summer, maybe less in these short winter days. So you divide 120AH by 4 hours, you need a panel(s) rated for 30A output. 30A at a nominal 12 volts would be 360 watts of panels. Two 180's or three 120's should be able to provide the 120AH of power during a Florida day, year round.

An MPPT controller gives you about a 10% boost over other charge controllers, and the charging efficiency of AGMs or gel cells (because of their lower internal resistance) can give you a 10% gain again, so the controller and battery type can shift the numbers by a good 10-20% as well. Batteries are a longer issue but that makes an MPPT controller a no-brainer.
I think this is optimistic because it

1) Assumes that you actually get the full rated output from the panels

2) It assumes that the sun shines fully every day.

I know we are gluttons for punishment here in New England, but even Florida has rainy days. I'd suggest cutting your expected output in half to accommodate these other pesky realities.

As for the original question about best bang for the buck, it unfortunately depends on so many things. I'm working through the same thing now for my boat, and I have some hard size/space constraints that I need to work within.

I'd suggest you first make a list of the constraints that you need to work within. On a boat I'd pay special attention to where and how you plan to mount the panels, shading, etc. It might force you to constrain your search to a certain size panel, or to two panels and not three.

On a boat where space is at a premium, SunPower's improved power/sq ft is very attractive, but given the specifics of your boat there might be other issues that trump power/sq ft.

Good luck with the project!
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Old 11-01-2012, 17:20   #27
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re: Best Solar Panels For The Buck

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I'd suggest you first make a list of the constraints that you need to work within. On a boat I'd pay special attention to where and how you plan to mount the panels, shading, etc. It might force you to constrain your search to a certain size panel, or to two panels and not three.

On a boat where space is at a premium, SunPower's improved power/sq ft is very attractive, but given the specifics of your boat there might be other issues that trump power/sq ft.

Good luck with the project!
Thanks. My two primary constraints are space and cost. The space constraint suggests that I should go with two panels placed end to end in the athwartship direction above existing dinghy davits. I would like to keep the overall length below 10 feet which suggests that each panel should be no longer than 60 inches and preferably less. Width is less critical since that's the fore and aft direction. With respect to the cost constraint, I've learned that the overall cost will be approximately $140 less if I select a 12 Volt nominal panel (at least when considering the Blue Sky MPPT controllers). That's because if you go above 12 Volt you're into a more expensive controller (ie, 3024iL vs 2512iX). The largest 12 Volt nominal panel at reasonable cost that I've found so far, that meets the dimensional requirements, is 185 watts so that's probably what I'll end up with. I'm now into the mode of searching for the best panel of this size for the buck. Suggestions appreciated
Pete
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Old 11-01-2012, 17:22   #28
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re: Best Solar Panels For The Buck

There were news stories recently in the States about a group of scientists at a university making a major breakthrough in increasing the efficiency of photovoltaic cells. I was wondering if anyone noticed this story and when the market might start to reap the benefits of the improved tecnology?
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Old 11-01-2012, 17:32   #29
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re: Best Solar Panels For The Buck

prroots,
Here is a 210 watt panel 58" long that might fill the bill for you:

Solar Cell, Solar Panel, Solar PV, Solar Products, Charge Controllers, Solar Trackers
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Old 11-01-2012, 17:50   #30
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re: Best Solar Panels For The Buck

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Originally Posted by twistedtree View Post
I think this is optimistic because it

1) Assumes that you actually get the full rated output from the panels

2) It assumes that the sun shines fully every day.

I know we are gluttons for punishment here in New England, but even Florida has rainy days. I'd suggest cutting your expected output in half to accommodate these other pesky realities.
The most common rule of thumb I've seen for horizontal panels on a sailboat in "the tropics" is to divide total watts by three to get approximate Ah per day you can expect.
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