October 16, 2014
Solar panels for electric fence
Just as the energizer should be matched to the size of the
fencing job, the solar panel must match the energy draw
of the energizer. For each 1 joule energizer output, allow
seven watts of solar panel capacity in high sunlight areas
and ten watts in low sunshine areas. In Missouri the
seven watt capacity has proven adequate in most
conditions, but in wet cloudy springs seven watts has
proven inadequate for keeping batteries fully charged.
Solar panels should be oriented from due south to no
more than 20 degrees to the southwest. The logic for
orienting the panel slightly to the southwest is because
mornings are often cloudy with clearing in later
afternoon, particularly in the spring and fall when day
length is shorter, thus more hours of intense radiation
occur when the sun has already progressed to the western
portion of the sky. The panel should be oriented so many
degrees off horizontal based on your latitude. Because
the angle of the sun's rays striking the earth differs
through the seasons, the efficiency of a fixed orientation
varies seasonally. For panels used only during the spring
to fall grazing season, 25-30 degrees off horizontal may be appropriate. Winter grazing requires a
panel more steeply inclined, up to 60 degrees off horizontal with a south to southwest orientation.
