Tuesday, October 23, 2007

More on the demo solar panel

I was somewhat unsatisfied with my measurements over the weekend (b/c of high variability), so I decided to measure the solar panels again today.

First of all I wanted to confirm that the 27% power increase was not a one time fluke, and secondly (perhaps because of my engineering background) I like to double check my measurements before making claims & assertions. The bottom line is that I measured between 26-30% increase in power with my solar panel design over the standard design.

It was a good sunny day although there were some small clouds that passed across the sun while I was taking measurements. I tried to wait for them to clear before making a reading, but I noticed some fluctuations in the current measurements (as a result I provide a range rather than a single number).

I got even higher readings for both panel's output (despite slight clouds, the day was cooler {weather service forecast 62F}). Solar panels should produce more power in cooler temperatures which may have contributed a bit. Also of interest on the topic of temperature the standard panel temperature was ~35C while the mirrored design read 45-50C when I took power measurements. Today was not as windy so I was able to do a better job setting up the panels so they faced toward the sun.

Standard panel
Voltage = 20.3V
Current = 2.4-2.6A
Power = 48.7-52.8W

My panel
Voltage = 5.11-5.3V*
Current = 11-13A

Max Power = 68.9W (13A x 5.3V)

*The voltage was steady each time I measured it, but I did get two different readings. My meter measures either current or voltage so I need to switch back and forth to take my readings.

If I use the 5.3V reading, power = 69W; the power increase is 30.5%...yes!

Even using the lower 5.11V reading shows a power increase of 25.8% from my panel.

This time I also brought my camera to document the set-up.
Here are the solar panels side by side, soaking up the sun. In case it is hard to tell, with my demo solar panel, the solar cells are roughly straight up and down and the mirrors are basically parallel to the ground. Both panels are set at roughly 45 degrees, although the panel with the mirrors may be at a slightly steeper angle.

I've included a snap shot of the current measurement of the mirror panel showing a high (12.98A) current reading. After nearly throwing away the 11.4A reading from Sunday (after having trouble getting it again, I was delighted to get much higher readings today).

Panels above and meter below.


At 3:38 PM, Anonymous Anonymous said...

I've done some research in this area and it sounds like CPV is only 15% cheaper than straight PV. Based on your work, do you think (as do I) that the CPV people are exploiting the technology? Heck, a 25% increase by merely adding mirrors as you've done, seems a no-brainer, and shouldn't increase the cost as much as the CPV people have raised the cost. Am I way on in left field in this opinion? There's a company that makes the same exact style you make, but the cost per Watt is almost as much as straight PV. In fact, it's probably the same if you went for the budget PV panels.

At 4:58 PM, Blogger Daniel said...

Hi Anonymous.

I agree getting 25% more power by simply adding a mirror seems like a good deal.

If you can remember which company makes panels the same way I do, I'd love to check them out.

I am aware of several CPV (concentrating photo-voltaic) vendors including amonix, solaria, sol-focus and a few others that are not immediately jumping to mind. They all have different designs-some use lenses, some use mirrors, some use multiple mirrors or some combination of lenses and mirrors and as a result get different concentration factors (i.e. different amounts of mirror/lens to cell ratios) which makes it difficult to generalize or compare technologies other than on a $/watt basis. Also some CPV systems require solar tracking which adds cost and complexity (as well as boosting output).

But the bottom line is that CPV systems really should be much cheaper to make than straight PV. As to what they charge for CPV systems, I'm sure that any CPV manufacturer is trying to capture as much of the "cost savings" as they can while still offering a better value $/W than straight PV.

At 2:17 PM, Blogger Daniel said...

I think this link provides a very good list of companies working in CPV arena fyi


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