Solar Panel Conversion Challenge

[Keegan]

Sanyo solar panels are some of the best rated solar panels on the market and are primarily for land based applications.

They are very impressive for use on a boat when you consider that you get 200 watts in a 30lb package with a reasonable size frame. They are also thinner than other panels so they would lay flatter on the bimini. Plus they are some of the more efficient ones out there.

This sounds like an advertisement but it is not, these are just the features that attracted me to the panels.

The problem is that the panels are not rated for 12V applications and I do not know how to convert the spec sheet ratings to a 12V application so that I compare apples to apples.

I have been told that as long as these are used with a charge controller such as the Outback 60 then they will have some of the best performance that one could buy even with a 12V application.

Can someone expalin how to convert the spec sheet to a 12V application.

Has anyone used this type of panel for 12V appllications? If so, what was the result?

I have attached a link to the spec sheet below.

http://us.sanyo.com/industrial/solar...ril%202007.pdf

Thanks
Keegan

[GordMay]

Amps = Watts ÷ Volts
A 200W Panel puts out a maximum of 14.286 Amps at 14 Volts
A = 200W ÷ 14V = 14.286 A

[Cruisingdad]

I have an Outback.

The Outback will convert the higher voltage panels to the necessary charge rate for your batteries. In fact, my array is wired in series, putting the voltage well beyond the 14.3 charge voltage. THe outback converts it for you.

Regarding the Sanyo's - I have no direct experience. I use Kyoceras, as do most of the cruisers I know. However, there is more to panels than just their output. Check:

1) Warranty and support.
2) Durability in a marine environment (which is considerably harsher than almost any land based environment).
3) Do they have self blocking diodes built in? Can they be over-riden?
4) How strong it the frame and glass/plastic top panel?
5) Accept any literature, especially lightning and power source production like solar panels and wind gens, with a grain of salt. Review the real world performance and charachteristics of your panels here: Eligible Photovoltaic Modules

Now you have a bit more information to make an informed decision.

- CD

[charlie p]

A high voltage panel and an MPPT controller (e.g. Outback MX60) is a good way to go. You will be able to use much smaller wires between the panels and the controller.

One thing to watch out for when selecting a controller is maximum input voltage. The Sanyo panel has an open circuit voltage of about 68 volts. Not all controllers will tolerate this. For example, the popular Blue Sky Energy model 2000E has a max input rating of 30 volts. Fine for the usual 17v panels but not with the Sanyo units. Some other Blue Sky models having higher ratings. The Outback MX60 is fine, with a max input of 140 volts.

Be prepared for at least some RF interference. Not a deal breaker but something to be aware of. When you install the controller, provide an easy way to turn it off. Many users just flip the controller off when using their SSB radio.

Charlie

[hellosailor]

"You will be able to use much smaller wires between the panels and the controller."
That doesn't make any sense to me, Charlie. Regardless of what controller you have, or how it works, using smaller wires between the panels and the controller will result in a higher power loss between them (greater voltage drop) and that can only mean less power to the controller.
Now, an MPPT controller may be able to "salvage" more power so the wire may not be as critical--but the voltage and power loss will still be caused by thinner gauge wiring.

[Keegan]

Thank you everyone for your comments. I still need to do more homework but your comments and information is appreciated.

For every one of the 200W Sanyo Panels that I place what would be a rough estimate of what they could produce on a daily basis in the tropics?

I am guessing they could put out ~60Amps per day in good tropic sun. Am I overly optimistic or on target?

Thanks again
Keegan

[GordMay]

I suspect that your 800 - 900W (60A @ ± 14V) is optimistic, in assuming over 4 hours of theoretical maximum output.

I’d expect an average of something more like half that (30 Amp/Hours -or- 400 Watt/Hours), in lower latitudes (Tropics).

There are a number of de-rating factors that will affect the actual daily output of your photo-voltaic module (solar panel), including:
- Solar Irradience (PTC watt ratings are based on 1000 Watt/m2 solar irrandiance, 20 degree Celsius ambient temperature, and 1 meter/second wind speed). Any cloud will reduce this significantly.
- Local Shading (masts, booms, etc).
- Angle of Solar Incidence (a horizontally mounted panel cannot achieve any where near maximum output).
- Dirt
- more ...

[charlie p]

hellosailor - It may not seem to make sense, but it is true about the smaller wires. The key point is that for a given amount of power, a higher voltage panel will produce a lower current (watts = volts x amps). The voltage drop on a segment of wire is proportional to the current, so it will be less (volts = amps x ohms). For the same voltage drop, the resistance can be higher (i.e. smaller wire).

Power loss through a given resistance is proportional to the square of the current, so dropping the current by a factor of 4, as in the Sanyo case, will drop the power loss by a factor of 16.

There are other issues to consider, such as mechanical integrity, when selecting wire sizes, but from a power loss perspective, higher voltage lets you go with smaller wires.

There is a reason power lines use very high voltages and automakers want to switch to 42 volts.

Charlie

[DeepFrz]

The Sanyo panel has an open circuit voltage of about 68 volts

Isn't 68 volts on a wet boat getting dangerous? Some of our electrical engineers might like to add their comments about electrical safety.

Maybe one of the reasons that the low voltage panels are used on boats.

[camaraderie]

Keegan...I'd say that with a good charge controller you might average 50A/H per day for unshaded flat mounted panels. (Less on rainy days <G>)!

[coot]

Originally Posted by DeepFrz

Isn't 68 volts on a wet boat getting dangerous? Some of our electrical engineers might like to add their comments about electrical safety.

I wouldn't worry about it. Yes, higher voltages are more dangerous, but that applies when you actually come in contact with the conductors, not just having it in an insulated wire somewhere. I have 120 volts AC on my boat, but it isn't a problem. The European version of this boat uses 240 volts. If you transmit with a marine SSB radio, there can be hundreds of volts on your antenna.

If you are actually working on the system, you should be careful. Of course, that also applies to 12 volt systems, which may not electrocute you outright, but can easily start a fire and destroy your boat.

Maybe one of the reasons that the low voltage panels are used on boats.

I think it has to do with 12 volt car batteries. The choice of 12 volts for our batteries is entirely arbitrary, but we use it because everybody else does. There is nothing special about multiples of 12 either, except that you can get 24 volts from two 12 volt batteries, 48 volts from four batteries, etc.