Thursday, September 29, 2011
2 Comparing concentrator to flat plate solar collector
Flat plate thermal collectors are not normally rotated to face normal to the sun but it is commonly accepted that if tracking can be used, it will increase the effectiveness of the solar heating or PV. Since the mechanism was available (and necessary) for the concentrator, I decided to try rotating the flat plate collector.
At the beginning of this test I saw that the concentrator was partially shading the flat plate collector (see the first picture above). In spite of this partial shading, the flat plate started heating quickly.
As can be seen in the first picture above (best if you click it to see an enlarged view), the surface of the mirror was covered with water drops from the rain we had last night. This would tend to scatter the sun's light at the beginning of the test. I did not clean the mirror.
As is normal at this time of year here, the day was mostly sunny with clouds. There was almost no wind. By mid-afternoon however, the cloud cover was solid and at the end of the test, it had started to rain.
You will see that I added a channel for the ambient air temperature. That sensor is out of the sun under the deck, about four feet off the ground, not touching anything but air.
I will be busy for a few days switching over to the insulated configurations for both the flat plate and the concentrator but I hope to have results from the next set of tests sometime next week.
Perhaps I should change the working fluid to 50/50 water/glycol in anticipation of winter? Brrr.