Saturday, October 08, 2011
An insulated collector for the concentrator
Here is an example of one such commercial system with an explanation of how it works
Fortunately due to high production volumes in China and India, the evacuated tubes are relatively inexpensive. I paid about $20 each for mine, a lot less than buying industrial glass tubing.
These type of commercial systems do not incorporate a large area concentrator. The heat captured in each tube is related to the area of the tube that faces the sun and maybe a bit on the back from the snow as a reflector in winter, some say. I felt that the usefulness of the tubes could be increased and less of them would be required if they were used at the focus of a concentrating reflector. The power into each tube could be increased, up to about 15x with my current concentrator. Would this be too much heat?
I had read that the heat pipes used are rated for a maximum of about 125 watts and I anticipated getting much more heat from the concentrator, perhaps 800 watts. Also, there was the difficulty of scaling up the manifold to the higher heat captured. So I had decided to remove the provided heat pipes and substitute a pipe loop into the interior of the evacuated tubes and to run my fluid directly through the evacuated tube.
The 3/8" copper tubing came on a roll. Creating more or less straight sections was an adventure in itself but I eventually, by hand and sighting by eye, had two more or less straight sections which were soldered into the 180 degree elbow. Next time, I will see if I can buy the 3/8" tubing in straight sections.
Lee Valley Copper Blocker material at hand. It is pure copper (not sure what the copper pot scrubbers are really made from) and it is formed as a sleeve, so it is easy to slide over the copper tubes.
The evacuated tube collector is finished and ready for testing.