View Single Post
Old 06-22-14, 05:14 AM   #17
osolemio
Hong Kong
 
Join Date: May 2010
Location: Hong Kong
Posts: 108
Thanks: 20
Thanked 17 Times in 13 Posts
Default

Quote:
Originally Posted by jeff5may View Post
The problem with what you propose is this: what happens during the winter when the sun shines bright? The oil in the collector heats up and thins out, while the plate hx is clogged with tar. The thin oil sheds its heat to warm the cold oil before it can effectively move fast enough through the loop to warm the house.

If you really need that high of a stagnation temperature, the oil will expand, too. Not as much as boiling water, but enough that you will need a holding tank. Something open to atmosphere.
The heat exchanger is indoors and should be fine, but the issue you mention is valid, mainly for the content in the tubes between the panels and the indoor part.

Not very many days a year are actually below -10C, and even more seldom -20C. I have been considering a very slow running of the system in case of severe cold, just as an extra precaution. Maybe a one-minute flush when it reaches a certain temperature. Since it's not very often, the loss of energy could be a small price to pay for "extra insurance". Nothing as annoying as busted pipes or panels!
__________________
Space heating/cooling and water heating by solar, Annual Geo Solar, drainwater heat recovery, Solar PV (to grid), rainwater recovery and more ...
Installing all this in a house from 1980, Copenhagen, Denmark. Living in Hong Kong. Main goal: Developing "Diffuse Light Concentration" technology for solar thermal.
osolemio is offline   Reply With Quote