THE SUN
• The source of solar energy
• Our nearest star
• Produces 3.8 x 1023 kW of power through
nuclear fusion reactions.
• Most of the energy we use derives from
the sun e.g. wind, hydro, wood, petroleum
USES OF SOLAR ENERGY
• Heating
• Drying
• Cooking
• Distilling
• Producing steam
• Generating electricity
CONVERSION OF SOLAR
ENERGY
• Solar » Chemical
This is done in plants through a process
called photosynthesis.
• Solar » Heat
This is done in heating devices such as
solar heaters and crop driers.
• Solar » Electricity
This is done by solar cells which convert solar light
energy into DC electricity.
SOLAR RADIATION PRINCIPLES
• Not all the solar energy reaches the earth
• Part of the sun’s energy is lost in the
atmosphere through reflection, refraction and
absorption.
• Solar energy varies over the day, month and
year.
• Solar energy is maximum at noon over a day
and in summer over a year.
• Areas between tropical of Cancer and Capricorn
receive more solar energy than areas outside
the tropics.
• Not all the solar energy reaches the earth
• Part of the sun’s energy is lost in the
atmosphere through reflection, refraction and
absorption.
• Solar energy varies over the day, month and
year.
• Solar energy is maximum at noon over a day
and in summer over a year.
• Areas between tropical of Cancer and Capricorn
receive more solar energy than areas outside
the tropics.
ANGLE OF INCIDENCE
• The angle at which the sun rays hits a surface have an
effect on the amount of energy reaching the surface.
• The closer the incident angle to 90 degrees the higher
the amount of energy received by surface. Solar devices
have a specific orientation and angle of installation to
make sure the devices capture as much energy as
possible.
NOTE: All panels in the south of the equator are supposed
to face north and those in the north of equator are
supposed to face south. The tilt angle depends on
latitude of specific site where the installation is taking
place.
• The angle at which the sun rays hits a surface have an
effect on the amount of energy reaching the surface.
• The closer the incident angle to 90 degrees the higher
the amount of energy received by surface. Solar devices
have a specific orientation and angle of installation to
make sure the devices capture as much energy as
possible.
NOTE: All panels in the south of the equator are supposed
to face north and those in the north of equator are
supposed to face south. The tilt angle depends on
latitude of specific site where the installation is taking
place.
SUN PEAK HOURS
• The number of hours of effective sunlight in a day is very
important. We can have 6 hours of effective sunlight
during some days of the year and 4 hours of sunlight
during some days of the year.
• Solar equipment converts energy only when the sun is
available.
• It is important that solar energy systems are designed to
work effectively even when sun peak hours are less. For
example, a solar PV system should be sized such that it
can provide enough power in October as well as in
June.
• It is always wise to verify with meteorological data on
sun peak hours for reliable solar PV systems
