[quote=Fearful][quote=sreeb]I don’t think it is just efficiency. The black pigment they use (carbon black?) is the cheapest/best one for protecting the polypropylene from UV light. Your system will not only be bigger, the individual components will cost more and fail sooner.[/quote]
Bollocks – iron oxide is also a very good photostabilizer. Not quite as good as carbon black, but close. Nice rusty red brown.
Besides, there are plenty of non black plastics that hold up fine in the sun. We aren’t even talking about water that’s under pressure, after all. And it’s kept cool by the circulating water.
Furthermore, a coat of latex paint is prescribed to protect ABS or PVC that emerges in roof vents. Just paint the stupid things.
The material cost of the polypropylene is small relative to the total installed cost. It could be coated, painted, impregnated, and the total installed cost would not change by much.
I think the reason it has not been attempted is because the market is small enough in the first place – people mostly only really care about swimming where it is hot enough during the day that the pool is nice to have somewhat cool anyway – that fiddling with the colors wouldn’t grow the market much. If given a choice, most consumers would like to have roof colored solar panels, but the availability of roof colored panels would not make many more people buy them.
That and the fact that people who make or buy them are thinking in terms of getting as much free energy from the sun as possible, aesthetics be damned.[/quote]
Not entirely accurate on the cooling and pressure arguments.
The system is only being cooled when water is flowing through it, and there are two reasons for water to not be flowing through it. One is when the pump system is off (lower duty-cycle, off-season, etc.). The other is when the solar system is isolated from the pool for being too hot. If the solar would take the pool to higher than the thermostat setting, then it is removed from the loop (allowing the water and pipes up there to get significantly hotter than when the system is running).
With respect to pressure, the system requires positive pressure to force water through the small pipes on the roof at the desired rate. I’ve seen some pretty spectacular failure on roofs where the system finally springs a small leak, and pressure forces the pool water out fairly forcefully (up into the air, onto the neighbors roof, etc.).
