best low light performance

Harold


I've asked nothing of PT, if the man says he gets those numbers, I have no reason to question him. I would also be thrilled to get those amps in low light. I know I live in "sunny Colorado" but I've seen plenty of overcast days here while camping. Especially in the spring and fall when we need the amps to run the furnace at night.
My concept is meet your needs in low light and you will always be happy, meet your needs in only bright light and one day you will meet my lil friend... Mr Generator.

BTW

The question was asked of you, not PT. You were the one that side stepped it, PT has been upfront with real world experience. You have only dismissed or discredited anything that doesn't support your position.

So here is a different question of the real world for you. What kind of amps do you get in shade or sun blotting out overcast and yes even in the rain? How long can your batteries last in those situations before you find a alternate means of charging? A week? Two weeks?

When you give the answer please add how many watts, how many AH and daily use.

Thanks

JiminDenver:
Seems you are not going to get an answer from pianotuna. I have made requests of him to support his claims several times to no avail.

Given the space restrictions we have on RV's, if you're looking for low light performance then amorphous is not a good choice.

Power output at 200W/m^2
Unisolar: P = 200W * 8% = 16W
Siemens: P = 200W * 12% = 24W
Kyrocera: P = 200W * 11.2% = 22.4W

If you're looking to maximize solar power, then amorphous is not a good choice.

Power output at 1000W/m^2
Unisolar: P = 1000W * 6% = 60W
Siemens: P = 1000W * 13.2% = 132W
Kyrocera: P = 1000W * 12% = 120W

For a one square meter area, poly produces about 8 W more power at low light levels, and more than 60W at high irradiance.

BTW, Kyrocera advertises efficiency better than 16%. The Unisolar chart listed it at 12%. That means for a 1 m^2 panel, the Kyrocera will output 160W while the Unisolar outputs 60W.

Sal

full_mosey wrote:

pianotuna wrote:
Hi,

Amorphous panels are clearly the best for low light performance--but are relatively speaking huge.

Does any one know if Poly or Mono are better in low light?

The answer is NO, neither Poly or Mono are better than Amorphous.

The real question is "How many sq meters will be needed to beat Amorphous and be less huge?".


HTH;
John

pianotuna wrote:
Hi,

Amorphous panels are clearly the best for low light performance--but are relatively speaking huge.

Does any one know if Poly or Mono are better in low light?

The answer is NO, neither Poly or Mono are better than Amorphous.

The real question is "How many sq meters will be needed to beat Amorphous and be less huge?".

HTH;
John

mena661 wrote:
For me it's only about total amp hour haul per day.

I am with you on a day that I cannot drop out of bulk charge and all the power is being consumed. If you are actually consuming every amp hour produced, it's all about amp hours. Once PWM pulsing kicks in and some of the solar output is being wasted, the number of hours charging after that matters to me as well.

And so does output at the actual temperature of the PVs, rather than output under test conditions. I think one of the reasons I'm seeing useable power much longer into the afternoon/evening shoulder is that many solar panels get hot on sunny days and drastically drop their afternoon output with that temperature rise. The Unisolars seem a lot more immune to this, so what would appear to be much more low light output in the evening is partly sustained output under higher surface temps. The effect is the same, but it is a compound cause.

Also flat mounting panels immediately makes lower light performance more important, since it shifts the whole curve down toward the lower end, except for when the sun is directly overhead, if ever.

Jim

Don't forget MPPT conversion. 15.5 amps in at Vmp can yield a lot more amps out into a 10.5 v battery, even after conversion losses. Again, no violation of physics here.

Jim

Hi,

In ideal solar conditions in June the system harvests 17 amps @13.6 volts on the output side of a blue sky 3024di MPPT controller. The panels are fixed flat install on the roof. I have no idea of the input amperage, and no easy way to measure it.

In leafy shade output is 7 amps, and in full rain 3 amps (don't remember voltages).

In bright sun on April 13 I was harvesting 14 amps @ 14.4 volts. Of that figure 12 amps were going back to the chassis power system.

Harvest numbers are all from the output side of the blue sky 3024di.

This is not about Uni-Solar being better or more efficient. Just real life numbers, which may be useful to folks.

pianotuna wrote:
Hi,

Misleading information, panels intended for charging a 12 volt battery are never 12 volts. Very optimistic numbers. Even worse if pwm is used. MPPT has conversion losses of between 2 and 4%, and losses increase as input voltage rises.

harold1946 wrote:
Watts = amps x volts. cant have one without the other.
a 12 volt, 256 watt panel is capable of producing 21.3333 amps maximum.
12 volt, 460 watts will produce 38.3333 amps maximum.

How is it misleading? the formula is the same, just change the volts to Unisolars spec of 16.5 volts and calculate for 256 watts.
256/16.5 = 15.5151 amps maximum. at peak output. Or what ever voltage trips your trigger.

JiminDenver wrote:

harold1946 wrote:
Watts = amps x volts. cant have one without the other.
a 12 volt, 256 watt panel is capable of producing 21.3333 amps maximum.
12 volt, 460 watts will produce 38.3333 amps maximum.

So then what's your explanation as to how Tuna can get more amps in the shade and rain than I can with near close to 200 watts more in my panels combined?

I will let Tuna explain how he can get more amps from a grid than it is designed to produce.
US-64 specs are 16.5 volt. output
So using the total wattage of the grid (256 watts)we calculate amps= watts / volts.
256/16.5 = 15.5151 amps.
As you can see, as the voltage increases the output amps decrease.