Tuesday, August 04, 2009
How Effective Are Solar Hot Water Systems?
Solar hot water heating systems are relatively simple to install, easy to maintain and the most
cost effective way to introduce your home to solar energy. They can save considerable energy and
cost when they replace an electric hot water heater. And they can be successfully used even if you
live in a climate where freezing temperatures are common during the winter.
If you live in a climate that does not have freezing temperatures, and your household consists of
fewer than five people, you can install a batch heater. This is the least expensive solar water
heating option, and it is relatively easy to build if you have the inclination to do-it-yourself.
It is simply a water storage tank that also serves as the solar collector.
The tank is enclosed in a glass-covered box that is positioned to allow maximum exposure to the
sun. The water in the tank heats up and hot water is available for use. However, it is not
the most efficient system, since it takes longer to heat an entire tank of water than to heat a
flat panel solar collector. And as the tank cools at night, there is less hot water available for
use.
There are two better systems that can be used even in freezing climates. The direct pump system
circulates water between a solar collector and a storage tank. With this design, water in the solar
collector can heat up faster, and the tank can be insulated for better temperature holding
capacity. The pump can be designed to run on electricity from a photovoltaic cell if you want to
keep your system completely solar powered.
A thermosiphon system also uses a separate solar collector, along with the pull of gravity. And it
allows for the use of an insulated storage tank for more consistent hot water delivery. When using
either of these systems in cold climates where freezing is an issue, both the piping and the
storage tank should be located indoors and properly insulated to provide hot water even on the
coldest days.
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