Help:with reflector design for black plastic hot water collector, etc.

System
System Posts: 2,511 admin
in General Solar Power Topics #1
I have been heating water on a black aluminum roof in a tilted coil of black coiled plastic water line made for burial in a trench. I would like to get more BTUs on cloudy days. I thought a reflector underneath it along with an enclosure to trap heat may do.

I'd like to have some ideas of reflector designs and configuration of my black pipe. I prefer to use gravity flow, but have 60-watt circulators if needed.

Thanks in advance

Nevin
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Comments

  • Frank
    Frank Solar Expert Posts: 54 ✭✭✭
    #2
    Re: Help:with reflector design for black plastic hot water collector, etc.

    An insulated enclosure with tempered glass will allow sunlight to penetrate then trap the reradiated heat, so that's a good idea. Not sure if you need a reflector: you may be getting more heat through conduction from the roof through the plastic line. You could use aluminum flashing as a reflector to do a test.
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: Help:with reflector design for black plastic hot water collector, etc.

    If it won't melt, I would go with a black backing wherever the sunlight could reach it, however, where the backing is hidden from the sun by the collector, a reflector would re-direct heat radiated FROM the COLLECTOR, back to the collector.
    What pressure do you have inside your black plastic water line? Be aware that this pipe wasn't meant for high temperatures, and will soften, perhaps to the point of bursting if enclosed under glass.
    I built my own collector using copper pipe, painted flat black, under glass and insulated back and sides with styrofoam. It works great, but in the few places where the sun gets through to the styrofoam backing, the heat melted holes in it. I had painted it black where the sun could hit it, to "make" more heat and protect it from UV etc. I now know it would have been better for the styrofoam if I had used white paint, of aluminum foil to protect it from the sun.
    Good luck
    Wayne
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