Anyone experienced using evacuated-tube solar waterheater?

[tomhelm]

Hi all,
Has anyone had any experience using an evacuted-tube solar water heater?
How well do they work? In bright sun summer days? Too hot?
What about cloudy Oregon winters? Too cold?
Pumping water thru them? Too expensive?
Brands, pumps, sizes?


I am considering adding as heat source for my soon to be installed
Doughboy 24' round indoor pool. I need to maintain about 90 degrees year round.
I live in the Willamette Valley, Oregon. Aka, the winter home of the Rain gods.

Thank you,

Tom

 

[dmanb2b]

Re: Anyone experienced using evacuated-tube solar waterheate

Hopefully someone soon will be along with some help, but do know our folks just north of the border there may have more experience with the tube type heaters. Although any solar system will require plenty of sun, which from recollection is not the northwest's strong point :lol: Anyhow, anything would help in conjunction w/ a gas heater or heat pump, but they will likely not get your water up to 90deg on it's own.

Welcome to TFP.

PS, I bought two fireplace doors from Portland Williamette...not sure if that is in you neck of the woods or not?

 

[chem geek]

Re: Anyone experienced using evacuated-tube solar waterheate

Welcome to TFP!

As you can see from the table in the first post of this thread, evacuated tube systems are less efficient than glazed panels unless the outdoor temperature is cold or the weather is cloudy. Even for the most efficient evacuated tube panels (that are 13% more efficient than the one listed in the table), the temperature difference between the water and the air has to be >= 50ºC / 90ºF so even heating the hot water to 140ºF this means the outdoor temperature would need to be below 50ºF on a sunny day for the evacuated tube to be more efficient than a glazed panel. However, for a cloudy day, the evacuated tube will be more efficient than a glazed panel at any reasonable outdoor temperature, though total heat output is obviously lower regardless of type of panel used.

Efficiencies vary a lot between different types of panels so check out the system ratings at the Florida Solar Energy Center. So choose an evacuated tube system with a reasonably high thermal performance rating. It will always be a lower number than glazed systems because these ratings are using full sun, but as noted above for domestic hot water the evacuated tube will heat better on cold or cloudy days. They are about twice as expensive as glazed panels, however.

 

[learthur]

Re: Anyone experienced using evacuated-tube solar waterheate

What chem geek said....

I would add... you should consider how much space you have to devote to tubes or panels. If space is tight, that may sway you more towards tubes and perhaps more cost. If space is generously available that may sway you towards panels and less cost. SNOW is another issue. If you have lots of snow, then you may want a panel as they can heat up enough to melt the snow off themselves. Tubes won't heat up (except at the header), but their shape should hold less snow ...in theory...