Tuesday, May 8, 2012

Benefits Of A Solar Tracker


I wanted to answer the question,  "How much does a solar PV tracker produce - theory vs. real world measurement as compared to a static mount system?"

I found lots of advertisements with numbers, such this one from Zomeworks:

     "Track Racks being 25% - 45% more efficient means either you get 25% - 45% more power or you can buy 25% less panels for your system and still receive the same amount of power had you chosen fixed racks. Either way you get more for the same amount of money."

   Zomeworks statement made sense, but I like to measure for myself. A few years back

I had my windows replaced. The advertised savings was 35%. Silly me, I did not measure and compare the new and old performance factors. However, they really needed to be replaced anyway, as the old aluminum frames were very cold in the winter.  There was a benefit, but since I didn't measure, I can't quantify it.

   The cost of a Zomeworks model Utrf - 120 (144" X 160" tracker, fits @ 8 panels) is about $2,400 from altE, an online store, and that did not include shipping. I like the Zomeworks tracker design. It has no motors, uses fluid transfer and balance. The drawbacks are size and this is hurricane country, so a solidly designed static mount has the survivability edge. 

  Back in Dec of 2011, I was l part of a Solar Coop.  We made a group buy of 66 solar panels and that gave us a little purchasing power. I purchased 8, 230 watt panels with Enpase micro inverters. The Enphase models logs solar production through a separate unit called an Envoy, so I could see my investment working on my computer. I was so impressed by the performance that I bought 8 more panels and microinverters, two of which were used in this Solar tracker experiment.

   My experimental  budget was $50.  I used scrap wood for both frames, bought 4 male/female MC-4 connectors from Solar Services and a few parts from Home depot. The grand total: $33.

  The Static frame was the easiest. I started there. 


   The Solar equinox was 20 March, so elevation was @ 36 degrees, azimuth: 180 degrees. Due solar South was checked at solar noon with a triangle, (11:03 on the 15 of Apr).  If the shadow didn't lie within itself, I was out of alignment. I adjusted the frame until it was aligned. If you want to find out about solar noon, NOAA has a geo-location solar calculator that is really easy to use http://www.esrl.noaa.gov/gmd/grad/solcalc/.

  The Enphase Envoy unit does the data logging, so that make measurement and tracking performance info accurate. 



  The Tracker rotated on a 68" x 1/2" conduit pipe. The bearings were three 3/4" PVC pipes strapped to a wooden frame that held the panel. It pivoted with ease and was adjusted once an hour by two 24" opposing  ratcheting bar clamps. On the day of the test it was a bit windy, so I rigged a damping system using a 5 gallon water bucket and bungee cord attached to one side.  

Because of the distance from the test rigs to the Enphase microinverters (which were on the roof), I used a 100 ft. extension cord and MC-4 connectors plugged into the correct connections.  


  The test results for the static mount showed the 1.0 KW produced a bell curve graph. 



The tracking mount produced a 1.3 KW mesa shaped graph, and a 30% gain over the static mount. 

The test was not perfect, it had location shading and connection losses, but the results were positive. 

My test results show that a tracking system will have a gain of approximately 30% more measured power, as  the advertised Zomeworks statement suggests, than a static mount system.

If you want to conduct your own experiment, contact me for further details.

Beau Gillis



3 comments:

Mark Martin said...

Hey there! Thank you for sharing your thoughts about residential solar in your area. I'm glad to stop by your site and know more about residential solar. This is a good read. I will be looking forward to visit your page again and for your other posts as well.
A solar power tower uses an array of tracking reflectors (heliostats) to concentrate light on a central receiver atop a tower. Power towers are more cost effective, offer higher efficiency and better energy storage capability among CSP technologies. The PS10 Solar Power Plant and PS20 solar power plant are examples of this technology.
We offer power meters for solar electricity products and services.

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