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Solar Photovoltaic Systems Follow the path of solar energy from the Sun to a
school.
| The Sun
produces radiant energy by
consuming hydrogen in nuclear fusion reactions. Solar energy is transmitted to the earth
in portions of energy called photons, which interact with the earth's atmosphere
and surface. It takes about 8 minutes and 20 seconds for the sun's energy to reach
the earth. |
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| The Earth receives and collects solar energy in the atmosphere, oceans, and plant life.
Interactions between the sun's energy, the oceans, and the atmosphere, for example, create
winds, which can produce electricity when directed through aerodynamically designed wind
machines. |
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| Solar
photovoltaic cells on the school's
rooftop convert solar radiation into electricity (photovoltaic
literally means "light energy"; "photo" = light, "voltaic" =
energy). Individual cells are packaged into modules, like the one
shown at the right; groups of modules are called arrays. Photovoltaic
arrays act like a battery when the sun is shining, producing a stream of direct current
(DC) electricity and sending it into the school building. Click here to see technical specifications of the modules
we use. |
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| The
weather station, located on the array, tracks
current weather conditions on the school's rooftop. The weather station contains an anemometer
to measure wind speed, a pyranometer to measure the amount of solar energy
reaching the array, and a thermometer to measure the temperature. The
electronic signals from the weather station are transmitted to the data acquisition system
where they are interpreted and stored for collection on a periodic basis. |
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| The DC
disconnect switch allows professional
electricians to disconnect the photovoltaic array from the rest of the system. With
the switch in the "off" position, workers can safely perform maintenance on
other system components. |
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| The
inverter converts direct current (DC)
electricity generated by the array into alternating current (AC) electricity for use in
the school. Most electrical loads (energy consuming devices like lights,
motors, computers, and air conditioners) in schools, homes and businesses use AC
electricity. Click
here to see technical specifications of the inverter we use. |
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| The
transformer ensures that the voltage of
the electricity coming from the inverter is compatible with the voltage of the electricity
in the school building. |
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| The AC
disconnect switch allows professional
electricians to disconnect the school's electrical system from the solar photovoltaic
system. With the AC disconnect switch in the "off" position, workers can
isolate the solar photovoltaic system and its components from the school's electrical
system, and can safely perform maintenance on the solar photovoltaic system's components. |
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| The
electric meter keeps track of the amount of electrical
energy produced by the solar photovoltaic system and sends electronic signals to the data
acquisition system where they are recorded. Electrical energy is measured in kilowatt-hours.
How much energy is contained in a kilowatt-hour? We're glad you asked. Use our
calculator to find out. |
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| The data acquisition system receives
signals from the weather station and the electric meter. It runs a computer program
to calculate and record the weather conditions and electrical output of the system every
fifteen minutes, and it allows students, teachers, and Watts On Schools staff to log in
and download information from the school or offsite. |
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| The
school's electrical distribution panel receives
electricity generated by the solar photovoltaic system, combines it with other electricity
supplied by the school's electric utility company, and routes the energy to the school's
classrooms to power lights, computers, and other energy consuming devices. |
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| Students
and teachers enjoy the benefits of
electric energy without even thinking about it. The school also benefits by having a
portion of its electrical needs met by solar power, resulting in lower monthly electric
bills. |
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CSGServices, Inc.
for American Electric Power
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