best low light performance

Performance per square foot, yes.

Performance per watt, no. On that graph all those different panels would have different wattages due to their differing efficiency per square meter. We normally compare a 100 watt poly to say a 100 watt mono. To do that with the information on this graph, you have to shift the curves to the standard test conditions that define what a 100 watt panel is. To do that, you have to shift all the curves vertically so they cross 1000 (standard testing illumination to define panel wattage) at the same point.

If you do this then follow the Unisolar line left, it rises when the others are all basically flat. It falls, but later than many, and starting from a higher point than all the rest.

Jim

I didn't read that graph the same way you did HiTech. There's four panels on there that get better low light performance than the Unisolars.

pianotuna wrote:
Hi harold,

Just like the really accurate information from some of the sources you have quoted on other threads that create watts from no where.

Thats quite an accusation. Would you care to support it with Quotes?
All of my posts are available for your research and scrutiny.
If there is any post you can find where I have stated it is possible to create wattage without as outside source, (from nowhere) I will apologize to you formally on this forum and any thread.

Hi harold,

Just like the really accurate information from some of the sources you have quoted on other threads that create watts from no where.

Thats some really nice information directly from Unisolar's advertising department. Now, if there were some independent company confirming the results, I would think Unisolar would have added that to their brochure.

Their graph, their test results, their claims, their advertisement.
Auto manufacturers make claims of fuel mileage that no one can achieve and thats very compelling also. They even have graphs comparing one to another.

bdosborn wrote:

Unisolar Efficiency by Bdosborn, on Flickr

Yes, Unisolar is more efficient at lower light levels. Unfortunately, efficiency decrease with increased irradiance so you actually have decreased unit output on sunny days. This doesn't address partial shading, angle to the sun or high heat conditions but I don't see much of a reason to go with Unisolar based on low light performance. The typical poly and mono panel is still going to outperform the unisolar, watt for watt, in low light conditions at STP.

From the link posted earlier:

Unisolar Linky

Bruce

Upon studying this, it actually proves that of the technologies listed on this chart, UniSolars have the best low light performance per watt (not per square meter) of any technology listed in the graph.

If you are comparing a 100w panel of each technology, you need to look at the 1000 irradiance w/square meter line and normalize there for the same wattage per panel. You shift all graphs so that they intersect this line at the same point. The standardized test point where the nominal panel wattage is defined, 1000. Now you have normalized to have a comparison for each technology in an equal wattage panel for each, rather than for a constant physical footprint for each panel.

As you move left on the curves in this shifted graph, the Unisolar is the only one where the power efficiency actually increases above that intersection point. The unisolar efficiency increases as light level drops. All the rest stay flat and then some start dropping off early, non linearly. The Unisolar drops off too but at a much lower light level and after climbing. When normalized so the panels being compared are all the same nominal watts, the UniSolar curve is the last to drop off and stays the highest from full power all the way to the left. In very low light, it actually achieves the same performance *per square meter* as the very best mono technology, and has more square meters per watt, so the output for the same wattage panel is significantly higher at lower light levels.

This is pretty compelling proof for the superior low light performance of UniSolars to me.

Jim

harold1946 wrote:

HiTech wrote:

harold1946 wrote:
One of the main reasons for early failure with all PV made by Unisolar is that the protective coating for both their rigid and flexable panels is plastic. UV destroys plastics, and it has to pass through that before reaching the cells.

Actually I think it's the other way around. I believe the plastic lense on the front of Unisolar units is heavily UV stabilized, resulting in the lower efficiency rating per square meter, because some of the light energy is absorbed by the stabilizing additive in the polymer coating.

UV stabilizer

Jim

That is one of the points I have been trying to make. The stabelizers used, reduce the efficiency at all times.
I do not know whether the stabelizers are applied as a topcoat or as an ingredient in the polymer.
Another possibility for reduced efficiency may be refraction caused by the stabelizing agent. Interesting.

Yes the UV stabilizer which stops UV degradation does make the efficiency per unit area (which is not positively correlated to efficiency at low light levels per nominal watt of power) less. We all agree poly and Unisolar panels take more space for a given wattage. The UV protection specifically absorbs UV frequency radiation, which is minimal at low light levels. So Unisolar panels have a huge surface area per watt to collect non UV light, much the way that a larger camera lense does better in low light. So possibly their low efficiency per unit and consequent large size per watt, may be exactly the specific reason they do better at low light levels. Huge light collection area per watt, and a non-clouded transparent coating that passes the frequencies of light that are most abundant in low light situations.

Jim

MrWizard wrote:

except for what ever is covering the cells

Harold did you read my complete post or did you stop before you got to that phrase

yes i know there is a coating over the cells, it is still clear, there is no degradation of output

No I did not stop, I read the whole post carefully. The first part of the post says there is no glass or plasiic on the panels. That is not correct, it is wrong. The cells are an intigrated part of the panels and are coated with a plastic.
I never said you have any degradation, I said it has been an issue with thin film panels.


Yours seem to be doing what you want and thats great.

HiTech wrote:

harold1946 wrote:
One of the main reasons for early failure with all PV made by Unisolar is that the protective coating for both their rigid and flexable panels is plastic. UV destroys plastics, and it has to pass through that before reaching the cells.

Actually I think it's the other way around. I believe the plastic lense on the front of Unisolar units is heavily UV stabilized, resulting in the lower efficiency rating per square meter, because some of the light energy is absorbed by the stabilizing additive in the polymer coating.

UV stabilizer

Jim

That is one of the points I have been trying to make. The stabelizers used, reduce the efficiency at all times.
I do not know whether the stabelizers are applied as a topcoat or as an ingredient in the polymer.
Another possibility for reduced efficiency may be refraction caused by the stabelizing agent. Interesting.

except for what ever is covering the cells

Harold did you read my complete post or did you stop before you got to that phrase

yes i know there is a coating over the cells, it is still clear, there is no degradation of output