Simple questions about not completely illuminated flex cells

[dongfang]

Hi,

I am trying to design a power system for a remotely located circuit which needs very little power. Super ultra light weight is critical. And I don't know much about solar

I thought about using one or more of the 3.0 or 3.6 volts versions of these: http://www.flexsolarcells.com/PowerF...Components.php . Since it is going to be on the Northern hemisphere and its operating in the winter and because I cannot control the horizontal direction of the device, I thought of rolling one of these into a cylinder and suspend it from the end. So half the panel is more or less illuminated and the other half not. The sun will be only 20 degrees of so above the horizon, that's why I am thinking vertical surface.
Will that work? I am concerned that at least one cell in the series connection will not be illuminated - does it go high impedance (serial resistence) and kill the power from the others then?
In which direction can I expect the series to be aligned on such a foil, side to side with a power but on each side, or top to bottom? If side to side, some series will be all in the dark when hanging as a cylinder in the low sun. Will they eat up power (parallel parasite) that the illuminated ones generate?
Or is that a bad idea, and should I have all illuminated always?
Any guess at how many cells are in series for 3V and 3.6V ? Okay 5 and 6 of 0.6 seems logical but is it right?

Regards
Soren

[SunEagle]

Hi,

I am trying to design a power system for a remotely located circuit which needs very little power. Super ultra light weight is critical. And I don't know much about solar

I thought about using one or more of the 3.0 or 3.6 volts versions of these: http://www.flexsolarcells.com/PowerF...Components.php . Since it is going to be on the Northern hemisphere and its operating in the winter and because I cannot control the horizontal direction of the device, I thought of rolling one of these into a cylinder and suspend it from the end. So half the panel is more or less illuminated and the other half not. The sun will be only 20 degrees of so above the horizon, that's why I am thinking vertical surface.
Will that work? I am concerned that at least one cell in the series connection will not be illuminated - does it go high impedance (serial resistence) and kill the power from the others then?
In which direction can I expect the series to be aligned on such a foil, side to side with a power but on each side, or top to bottom? If side to side, some series will be all in the dark when hanging as a cylinder in the low sun. Will they eat up power (parallel parasite) that the illuminated ones generate?
Or is that a bad idea, and should I have all illuminated always?
Any guess at how many cells are in series for 3V and 3.6V ? Okay 5 and 6 of 0.6 seems logical but is it right?

Regards
Soren

After reading a little about that technology I would presume that if any part of the "panel" is in the shade the it will not produce much so making a cylinder out of it will put some of the "panel" not facing the sun all of the time. So it seems to be better to have the entire "panel" to be facing the sun as directly as possible to get 100% output with a drop in output to 71% if the Sun angle reduces to 45 degrees.

Also those 3 and 3.6 volt versions are not compatible for outside use. You would need to use the WeathrerPro Series which are at 7.2 and 15.4volt ratings.

Go check the "Instructions" section on their website and it will give you a little more detail on how the "panels" can be wired.

[dongfang]

After reading a little about that technology I would presume that if any part of the "panel" is in the shade the it will not produce much so making a cylinder out of it will put some of the "panel" not facing the sun all of the time. So it seems to be better to have the entire "panel" to be facing the sun as directly as possible to get 100% output with a drop in output to 71% if the Sun angle reduces to 45 degrees.

Also those 3 and 3.6 volt versions are not compatible for outside use. You would need to use the WeathrerPro Series which are at 7.2 and 15.4volt ratings.

Go check the "Instructions" section on their website and it will give you a little more detail on how the "panels" can be wired.

Hi SE, thanks for the answer -

I know the portion of the foil not in sunlight will not produce much - that's okay but will it kill the power produced by the part in sunlight? Either by series resistance or by parallel load?

They are not made for long time outdoor use okay, but it has to be ultra light and just live for a few days. Should work.

Regards
Soren

[Wy_White_Wolf]

Put 4 of them on a cube with blocking diodes on each one. That way 1 would always be within 45d of the sun and the diodes would prevent the current from reversing through the others.

WWW

[SunEagle]

Put 4 of them on a cube with blocking diodes on each one. That way 1 would always be within 45d of the sun and the diodes would prevent the current from reversing through the others.

WWW

That might work. With at least one of them facing the sun at some producing angle.

I can't tell from the website but it looks like if any part of the "panel" is in shade the entire panel will not produce anything. So having multiple panels "flat" on a cube at different compass points should be able to yield some output from one or more.

[bcroe]

I think every surface will produce a bit of power in sun, so I would put them all in
parallel. I would try it without blocking diodes. Bruce Roe

[PNjunction]

Powerfilm has some of the best thin-film panels out there, and you will pay dearly for it.

Note that you are looking at the bare "OEM" products, and might do better with those already prefabricated into complete rolls with backing, cabling etc from powerfilm themselves and not a distributor of their oem line.

The shaded portions of thin-films do not hamper the power production of those parts that are in sunlight. However, LONG TERM consistent shadows will eventually degrade the shaded portion. For what you are doing, that doesn't sound like a problem - and for many portable users where the sun and shadows are moving anyway, not a huge issue. Permanant large installations vs mono/polycrystalline and lifetimes have been discussed elsewhere. But you aren't doing isn't permanent, so moving forward....

The problem is that like any solar panel, you want most of it illuminated evenly at the best angle. If you lay one of these flat instead of optimally angled, you'll experience about a 30% loss of power or more. Wrapped around a pole - even more.

In the end, it would be hard to figure out if your project would be successful or not based on ANY non-standard shape, unless the panel/pole and load draw ratio was huge to make it all work. That's going to be big bucks.

[Mike90250]

And there are 2 ways to wrap a panel around a pole.

One reduces your power harvest to 1/4 of the panel rating.

The other reduces the voltage to 1/4 voltage, and nothing will help with that.

[dongfang]

Hi,

And there are 2 ways to wrap a panel around a pole.

One reduces your power harvest to 1/4 of the panel rating.

The other reduces the voltage to 1/4 voltage, and nothing will help with that.

Okay thanks for the answers. Seems there is no easy way for me this time. Either I have to go with multiple panels each in different directions, or I have to live with a high loss from a wrap into a cylinder, or I have to suspend the panel flat face up. The latter seems obvious, but the application is supposed to be used in low winter sun in a very remote location..

Regards
Soren

[inetdog]

Hi,



Okay thanks for the answers. Seems there is no easy way for me this time. Either I have to go with multiple panels each in different directions, or I have to live with a high loss from a wrap into a cylinder, or I have to suspend the panel flat face up. The latter seems obvious, but the application is supposed to be used in low winter sun in a very remote location..

Regards
Soren

I think that given you want the panel surface to be vertical so that it sheds snow, the triangle or square of flat panels wired in parallel will be your best bet for using standard parts and having a predictable output voltage.

[SunEagle]

I think that given you want the panel surface to be vertical so that it sheds snow, the triangle or square of flat panels wired in parallel will be your best bet for using standard parts and having a predictable output voltage.

That would be the type orientation that White Wolf mentioned.

Put 4 cells on the vertical face of a cube (wired in parallel) and support it in the middle. Now which ever direction the sun shines then one or two of those panels may get enough to produce the desired voltage.