Go Greener Tips

From the operators of www.GreenLivingRocks.com — providing education regarding how to build a solar panel, solar energy facts, and evacuated tubes.

There are 3 key kinds of hot water solar collectors commonly used in homes: flat plate and evacuated tube systems.  There are a number of different “recipes” for constructing each kind.  But here is a short description of their similarities and differences.

First, there are pool solar collectors.  These are usually a type of flat plate design, but there are enough differences between solar pool heating systems and solar hot water heating systems that some clarification is necessary.

Pool solar collectors, are usually designed as rows of UV resistant black polypropylene pipe that is heat welded together.  Since pool heaters call for lower water temperatures than hot water for showers or for heating a building, the collectors do not need to be encased in a box.  In fact, the polypropylene plastic is not proposed to withstand the high temperatures needed for other domestic hot water use, and should not be enclosed by glass.

Though solar pool heating systems are about the easiest solar energy system that you can make or install, the solar collectors themselves are not so easy to make.  The polypropylene pipe does not react to adhesives, and the procedure and equipment needed for heat welding is cost prohibitive for a do-it-yourself project.  And using a substitute material may not be wise because of its tendency to break down with ongoing exposure to the sun and chlorine from the swimming pool.  For this reason, it is probably easier to purchase the solar collectors even if you prefer to install the system yourself.

Evacuated tube solar collectors are also complicated to build.  Although they are used for domestic hot water and for heating a house with hot water, the materials call for special handling.  They use unique glass tubing with double walls.  The air trapped between the walls act as insulation, similar to the way dual pane windows trap air for insulation.  The innermost tube can be filled either with water or with a heat transfer fluid to prevent freezing in frozen climates. Obviously, this kind of system is more complicated to build and install than a simple hot water heating system.  Again, it might be easier to purchase the solar collectors unless you have a lot of expertise and confidence.

Flat plate solar collectors, also used for residential hot water and heating, are generally easier for a do-it-yourselfer to build.  The design is fairly uncomplicated and basic.  Flexible tubing for the water is attached to an absorber plate and positioned inside of an insulated metal box.  A glass cover is used, which allows the sun to heat the water.  As the water is heated, it is pumped into an insulated storage container and held for use as needed for bathing or washing dishes.  With the assistance of a good set of instructions, constructing and installing a hot water system using flat plate solar collectors is a good project for people who are handy and motivated.