View Single Post
Old 10-10-14, 05:08 AM   #4
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Quote:
Originally Posted by SDMCF View Post
Can you explain your reasoning behind this?
That is quite simple.

Vacuum tubes, no matter what situation they are placed in, have a high failure rate. Industry rates vary but range from 0.5 to 4% annually. The worst offenders are the basic Chinese made tubes with heat pipes ( some people on here have commented on trying to fix their heat pipes) and I have gotten tired of being asked to come and fix a solar system that is not performing as expected just to see 20 or 30% of the tubes have lost vacuum after just a few years operation.

Flat plate collectors don't work under the same stresses and can go 30+ years without a problem, as long as the glycol is changed regularly.

It is true that tubes can outperform flat collectors IN SOME CIRCUMSTANCES......but we don't see those circumstances as often as people think. For example, a tube will be more efficient at temps above 100C where they lose less heat than a flat collector per m2 of area but residential solar doesn't operate at those temps.

To my mind, if you want 4m2 of tube collector area, great but if you want better longevity and less maintenance put in 6m2 of a good flat collector and the performance will be better.
Mikesolar is offline   Reply With Quote