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Old 18-01-2012, 17:48   #1
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Best Solar System

I would like to keep my question as simple as I can as I do not know much about solar panels.

Assume the power requirment is for 300 +/- watt panel or panel.

Should a single panel rated at 300 watts 28 volts combined with a MPPT controller be considered?

How would a higher voltage single panel compare to say 2- Kyocera 135 watt ( 12 volt nominal panels) ?

comments on non 12 nominal panels would be appreciated, it seems I have trouble understanding how many volts I can go if I use an MPPT controller.

I would like to get about 80 to 100 amp hours per day in 8 to 10 hours of sun ( Southern Ontario - summer only)

Thanks Gang


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Old 18-01-2012, 18:58   #2
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Re: Best Solar System

Just a note that you can only count on 4-5 hours of real solar output from a fixed mounted solar panel. My 135watt Kyocera puts out about 6 amps (not Mppt) in the summer, mounted flat. Might get a bit more slanted but that does not work so well on the hook.

The maximum voltage is a function of the Mppt controller, so you have to match the panel or panels peak voltage to the MPPT controller peak voltage rating. They give about 10-15% improvement in output over non-mppt controllers.

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Old 18-01-2012, 19:17   #3
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Re: Best Solar System

What a thread title! Best Solar System. I was going to nominate an eight-planet solar system out near the edge of the Milky Way galaxy.
cruising is entirely about showing up--in boat shoes.
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Old 18-01-2012, 19:33   #4
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Re: Best Solar System


Some real world numbers. At your latitude during the summer I get about 6 hours of full output with flat mounted panels, plus a few more hours of partial output. The KC-130 puts out 7.5 amps and the two 40W panels 2.5 amps each, wired in parallel to an MMPT controller for a total of 12.5 amps at the battery monitor. It seems logical that two KC-135s would provide 15.0 amps, so yes, 100 amp-hrs is theoretically possible, if you have clear skies, your panels aren't shaded, and your batteries are depleted enough to take a full 15 amps throughout the day. Realistically, when your batteries are near full charge the sun will shine, but when your batteries are really down it will be foggy, you'll be heeling away from the sun, the sails will be shading the panels! So plan on something like 60% of your theoretical amp-hrs, and realize you'll need another power source when you get a few days of heavy overcast.

With multiple panels the unshaded ones can provide full output. You'll need to think about parallel vs. series wiring. I'll leave that discussion to others.
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Old 18-01-2012, 19:45   #5
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Re: Best Solar System

Space is usually a premium for boaters. After much research, We chose Sanyo HIT-225 watt panels. About 31 x 61 and about 18% PANEL effieiency. Supposedly improved low light capability, made USA. Most other panels are 11-12% so larger for the same power. These are high voltage panels; 54 Volts open circuit. Match your MPPT to the panels. We will use Blue SKy 3048 with high voltage capability. The MPPT can modify the output to reduce panel voltage and increase amperage. THey cannot increase voltage above the solar output. If your choose high voltage panels then you will be able to continue to get power out of your panels and MPPT as they are shaded or as the sun ebbs. If you can guarantee that the panels are never individually shaded you can run them in series and further boost the voltage. Blue Sky has a variety of both high and low voltage MPPT units and their staff was really helpful guiding us to a ballanced design.

We have a Ketch so the only open area is on top of the Bimini. I can put three HIT-225 panels on top. Due to likely shading, we will wire in parallel. The panels have internal diode seperated circuits to be somewhat shade tollerant. I plan to make the mounts tiltable to improve the incidence angle when possible.
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Old 18-01-2012, 19:46   #6
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Re: Best Solar System

Sorry BASH, MIA CULPA, perhaps I should have titled the thread "Stupid". Sarcasim is the lowest form of humor. Just would like to know what voltage of panel to shop for.

So the thread should have been titled " What Voltage "

I guess I have been Bashed!

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Old 18-01-2012, 19:55   #7
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Re: Best Solar System

There is really no practical difference between different voltage setups. Make sure MPPT regulator can cope with the voltage and you will be fine. You are best to fit the maximum wattage you can squeeze in. If all other things are equal multiple panels will be slightly more shade tolerant than a single large panel and will provide some redundancy, but other differences such as ease of mounting and cost are generally more critical.

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