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ajriding

st clair

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Posted: 08/30/19 05:08pm Link  |  Quote  |  Print  |  Notify Moderator

It would be interesting to see the amps change as the panel is tilted

ktmrfs

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Posted: 08/30/19 09:34pm Link  |  Quote  |  Print  |  Notify Moderator

ajriding wrote:

It would be interesting to see the amps change as the panel is tilted


been there, done that, what I found pretty much matches the math.

the drop in power is related to the cosine of the angle error in the vertical and horizontal plane. as an example if the error is 45 degrees, power drops to 70% of max. a 60 degree error drops power by 50%. depending on your latitude and time of year and time of day the error can be insignficant or noticeable.

And measuring voltage or current alone is NOT a good way to determine the loss. you need to measure both voltage AND current.

to get "perfect" alignment, place a tube, like an empty tp tube perpendicular on the panel and adjust for no shadow. easy to do on portable panels. almost impossible to do on roof panels since most only allow tilt in one axis.

and unless you have a tracking system, perfect alignment only lasts a short time. On my portable panels I just set them for best alignment around noon and live with what I get.


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ktmrfs

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Posted: 08/30/19 09:36pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

Hi ajriding,

Thanks for taking the time to experiment and share it with us.

Solar panels are a 'constant voltage' device. You may loose 25 to 30% by not tilting. But NO WAY am I climbing the roof in a storm to stow the panels.

I'd consider a remote controlled tilting mechanism--but it is cheaper just to add another panel.

I trust folk's opinions when they have actually done an experiment, rather than guessing.


solar panels are not a perfect constant voltage device, but close enough for most first order calculations.

pianotuna

Regina, SK, Canada

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Posted: 08/30/19 09:46pm Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs,

Thanks for the correction on "constant voltage"!

Since I don't monitor incoming voltage which is nominally 33, the Blue Sky controller jumps from "off", to "on", at something above the overnight float voltage (which is depended upon how much I've drawn the bank down). It starts charging at 0.1 amps about 30 minutes after sunrise.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Harvey51

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Posted: 08/30/19 09:54pm Link  |  Quote  |  Print  |  Notify Moderator

The physics of solar energy is that the voltage (energy per charge) is determined by the colour of the photons hitting the molecules in the panel. V = hf where h is Planck’s constant and f the frequency of the light which determines the colour. Angle has no effect on the voltage. Each photon hits one electron transferring its energy to the electron. Angle does affect the current or number of photons that hit the panel, determining the number of electrons carrying solar energy.


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pianotuna

Regina, SK, Canada

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Posted: 08/30/19 10:06pm Link  |  Quote  |  Print  |  Notify Moderator

Harvey51,

Thanks for that lovely morsel of knowledge!

Does that extend to infrared and ultraviolet?

I know my panels are "triple junction" to respond to 3 different frequencies of light.

And how come you know this stuff???? * chuckle *

TomG2

Central Illinois

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Posted: 08/31/19 03:16am Link  |  Quote  |  Print  |  Notify Moderator

Some good information here.

http://www.solarelectricityhandbook.com/solar-irradiance.html

red31

Bryan

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Posted: 08/31/19 06:25am Link  |  Quote  |  Print  |  Notify Moderator

ajriding wrote:

It would be interesting to see the amps change as the panel is tilted


set your meter to amps and redo!

takes very little light to yield voltage (Voc) but the current (I) is approx directly proportional to the light, in the graph, full sun perpendicular to the panel is ~ 1000 W/m2, panel operates @ battery voltage (PWM) or mppt voltage.

[image]

BFL13

Victoria, BC

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Posted: 08/31/19 06:44am Link  |  Quote  |  Print  |  Notify Moderator

I also did some measurements. This was in May at 49N latitude, using a 130w panel where I was able to take all-day AH hauls over three days with the same perfect sun conditions.

Tilted up and also aimed during the day- 90AH
Tilted up fixed aim South- 70AH
Flat- 56AH

A second panel lying flat would be 56 x 2 = 112AH, more than the single panel tilted and aimed getting 90AH.

It is situational what to do about that. When we went there for a few years seasonal off-grid all summer with the 5er, I chose single 255w panel ground- mounted in a tilted, twirler contraption. With the MH, and not seasonal anymore, but still off-grid a lot, I chose more panels flat on the roof.


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profdant139

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Posted: 08/31/19 07:54am Link  |  Quote  |  Print  |  Notify Moderator

Interesting discussion! I wonder why home solar panels aren't built to track the sun -- they are almost always stationary. My guess is that the cost and maintenance of tracking outweigh the gain in extra power.


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