Solar heating-what's the best system?

[Kwikee]

And what's the best value system? I'm looking at this now and had sort of settled for the old PVC ribbon-type matting looped across the roof:
[attachment=0:188qbg72]PVC tube.jpg[/attachment:188qbg72]
I am also aware of the much wider, pre-assembled mats like this, although this one is polypropylene and claims better efficiency, lifespan and ease of installation:
[attachment=2:188qbg72]PolyPropylene tubing.jpg[/attachment:188qbg72]
These also caught my eye and claim greater efficiency (50% they claim)and less frictional losses than the traditional PVC type so easier on your pump and you need less area:
[attachment=1:188qbg72]HDPE panel.jpg[/attachment:188qbg72]
That sort of makes sense, to heat a lot of water a little bit at a time is the most efficient way.
$'s per sq.m the PVC is hard to beat, but if the efficiency is true for the HDPE and PP, then it's about the same.
I haven't included vacuum tubes purely because they are expensive, but I would imagine the most efficient.

So what's the latest and greatest? Or can someone open my eyes to something better value?!

 

[X-PertPool]

I don't know what model is the best but it seems the consensus is that you want to maximize the surface area and move the water as quickly as possible. For example having water moving slowly through a black garden hose is the total opposite of what you want. You want a super thin band of water moving very fast. With that being said, before we replaced our home made system with actual panels we had 1/2" black poly tubing running in coils in a box on a roof that was enclosed in glass to further trap heat. It worked but having a coil of pipe made it hard to find a leak when it happens.

 

[Isaac-1]

I am not sure what is available in your market, here in the US I have seen panels of the first two types shown. Each has advantages and disadvantages, mostly related to wind loading, freeze resistance, and to some degree heat lost to wind. The problem is it is hard to tell quality of construction from photos, it is often even hard to tell in person without dissecting a panel, even then it is hard to tell the quality of things like the UV inhibitors used in the plastic, etc. Having said that the efficiency of most commercial panels that have been tested by independent labs like the University of Florida Solar Energy Center, http://www.fsec.ucf.edu/en/consumer/sol ... /index.htm are very close under controlled conditions. Usually this will be less than 10% variation on performance in the lab tests, and in the real world could even change positions if the lower performing one from the lab test retains more heat in windy conditions, etc.

Ike

p.s. note that the ribbon style collectors are available made from a number of different materials, with different trade off's for longevity and performance

 

[chem geek]

These also caught my eye and claim greater efficiency (50% they claim)and less frictional losses than the traditional PVC type so easier on your pump and you need less area:

That 50% greater efficiency is a bunch of baloney. Don't believe marketing hype at all. Actual independently measured solar panel efficiencies are listed at the Florida Solar Energy Center. The least expensive are the "unglazed flat plate" type of panel and the highest efficiency panels are the FAFCO Revolution or Performance Solar Performance Plus at 1060 BTU/ft² though many panels are at 1000 or above which should be fine.

The unglazed flat plate panels are the highest efficiency of all panel types when there is no temperature difference between the water in the panel and the air outside the panel or if there is some temperature difference but no wind. When the air is cooler than the panel and especially when that occurs with wind, then the glazed flat plate is more efficient. When the temperature difference is even more extreme as with domestic hot water heating, then the evacuated tube (tubular) are most efficient. Note that the collector ratings for the glazed flat plate do not include losses from the required heat exchanger since the manufacturers recommend not putting pool water directly through their systems that use copper piping. See also Solar Panel Technology Comparisons.

The glazed panels used to cost around 3x the unglazed panels, but I believe that difference is closer to 2x these days. The evacuated tubes are around 2x the cost of the glazed panels. Generally speaking, if you want to heat your pool more into the spring and fall (or even some heating in winter), then the glazed or evacuated tube panels would work better. Also, if your air temperature isn't warm and you have wind, then the glazed and evacuated tube panels work better. Most pools, however, use the less expensive unglazed panels and they heat the pools reasonably well since most people don't heat their pools to warm temperatures much hotter than air temps and most people don't use their pools when air temps get very cool. With our pool which we heat to 88ºF (used for water therapy) and that we want to use from April to November or December, it would have been better for us to get glazed panels and when we replace our panels some day that is what we will do.

 

[peterdaly]

My SolarAttic system, although not traditional solar, is giving me roughly 12-15 temperature lift. Mid-80's right now. Where I am located, I suspect it works better than traditional panels.

There is no "best" solar system. It's more a question of what is right for you, and why. The answers above are quite good. Wind is a key consideration.

Never seen that bottom panel...what is it?

 

[ENCSOLAR]

Helicoil made in Israel