best low light performance

I did this for amorphous vs poly. This data is for a 1 m^2 panel at low irradiance.

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

BTW, Don's US64 has 1 m^2 area. And that's the same size as a 135W Kyrocera.

Comparing those two panels, we get:

*************** US64 *** 135W Kyrocera
Max Power ** 64W *** 135W
Low Light **** 16W *** 22W

Sal

full_mosey wrote:
Salvo;

All we need now is the size of the panels to be stated in m^2.

We know that Amorphous panels are huge. What we need to know is what happens if we use the same m^2 size for Amorphous, Mono or Poly.

Which gives more Watts per roof real estate at low irradiance? :)

HTH;
John

HiTech wrote:

harold1946 wrote:

I have heard many claims over the years about this or that panel being superior, but the fact remains, if one is using more than can be produced, the only answer is to produce more, and the answer to that is an array that will produce the most power with the available realestate.

I basically agree, but my take would be *enough* power *under the actual conditions the solar panels are in*. Or possibly under the worst case conditions you care to plan for.

That seems to be the difference in the approach. Design for specific conditions that are different than nominal, or select technology for nominal conditions and just keep getting more until it meets your actual conditions often enough.

Jim

I guess we could go with different climatic scenarios, but what would be the point. I believe everyone would agree that solar is not without its shortcommings, and under extreme conditions can be taxed passed its capability.
My AGS system kicks in the genny whenever the solar is not able to handle the load.

We are fulltimers, not weekenders. We go where we choose from Mexico to Alaska, east or west coast. If it snows I have to clean off the solar panels. Over 90% of the time we are boondocking. Between March and November of last year we spent two days with hookups.

I love that shot. Makes me guffaw at the thought so many tech discussions end up resembling that contest of wills...

Like the wildebeest and crocodile/log...

But I did notice a substantial drop in potential from my Kyocera panels when they heated up. 11:00 AM panels covered. 0 amps. 11:01 uncover panels 62.6 amps. 11:45AM 51.3 amps. Battery bank between 12.25 and 12.35. No voltage droppage increase across controller. No droppage increase between panel junctions and battery posts. Key word: INCREASE

Ambient temp 38.8C (according to my notes). Cloudless sky. Latitude 19.88 Month of May. Year 2009

Mex

Did you take that picture of the Elk in my back yard in late February
This time of year there are no large Antlers aka to the locals "horns" up high
I have large stack of them my dog brings them up from the back yard

harold1946 wrote:

I have heard many claims over the years about this or that panel being superior, but the fact remains, if one is using more than can be produced, the only answer is to produce more, and the answer to that is an array that will produce the most power with the available realestate.

I basically agree, but my take would be *enough* power *under the actual conditions the solar panels are in*. Or possibly under the worst case conditions you care to plan for.

That seems to be the difference in the approach. Design for specific conditions that are different than nominal, or select technology for nominal conditions and just keep getting more until it meets your actual conditions often enough.

Jim

Yet more fuel for the fire of these seeming discrepancies in low light performance different trustworthy people are seeing in the real world compared to presumed or predicted results:

Low light is not just full spectrum straight-on light at lower intensity. That's one form. That's the form in the standard tests.

Another form is light far from straight on, coming in at a high angle of incidence. This light hitting the cell is low due simply to geometry. Performance is similar across technologies if they are behind plate glass because it is responsible for the bulk of the light loss at these angles, but very different for other surfaces.

One form of low light is light with a skewed spectrum, either because of time of day, haze, fog or clouds. Not sure about Unisolar's spectrum specifically other than that it has 3 PVs in one, each for a different frequency range. But Amorphous silicon has a higher bandgap (1.7 eV) than crystalline silicon (c-Si) (1.1 eV), which means it absorbs the visible part of the solar spectrum more strongly than the infrared portion of the spectrum. So low light with lots of red will perform differently on the different technologies than low light with more blue. If you can feel warmth on your face from the sunlight there is IR, if not, much of it is filtered.

Also already mentioned, yet another form of low light is partial shade or dappled sunlight. Different technologies will respond differently to this form of low light than uniform light levels.

Honestly there are so many variables in low light performance, I don't think there are many here with enough information to legitimately discredit other's real-world results in most cases.

Jim

JiminDenver wrote:
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

I will do the best I can.
Battery bank AH 735.
860 watts of solar.
I do not bother calculating our daily use, never found a need to.
The amount of amps being produced it totally dependent upon the amount of sunlight, not the amount of shade, and I do not have a means of measuring shade.
If I am not using any power the battery bank only looses at a rate of 1% per month. Otherwise the length of time varies greatly depending on power consunption.

I did not side step the question, I can not answer for what PT claims. Only he can answer that.

It is 12:55 right now and my array is producing 30.43 amps in full sun.
I have also seen days when the best being produced was 3 amps.

Solar charging batteries is like filling a bucket with a hose. A firehose will fill it faster than a garden hose. If water is being used out of the bucket it takes a bigger hose to keep it full.

I have heard many claims over the years about this or that panel being superior, but the fact remains, if one is using more than can be produced, the only answer is to produce more, and the answer to that is an array that will produce the most power with the available realestate.

Yep I need Dramamine for this'un...

Salvo;

All we need now is the size of the panels to be stated in m^2.

We know that Amorphous panels are huge. What we need to know is what happens if we use the same m^2 size for Amorphous, Mono or Poly.

Which gives more Watts per roof real estate at low irradiance? :)

HTH;
John

Beautiful shot Mex.