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Electricity and Basic Electronics
easy for golf courses to recharge their golf cart
batteries each night. Some vehicle charging
stations are showing up at malls and at a
limited number of service stations.
Some companies have been investigating
electric transportation for a single person. One
example of this is the Segway®, Figure 24-12.
A Segway® uses batteries for power and
gyroscopes for balance. Some police offi cers
and some security offi cers in airports and
on college campuses are using these to move
about quickly without becoming tired. The
average speed of most models is over 12 mph.
Alternative Energy
Alternative energy is energy derived
from a source that does not deplete the earth’s
natural resources or harm the environment.
The use of two leading sources of alternative
energy has evolved over the last few decades.
One source is the sun and other is the wind.
Photovoltaics are used to harness the Sun’s
energy, and turbines are used to harness the
wind’s energy. This section discusses these
systems.
Photovoltaics
The total amount of energy the Earth
receives from the Sun is estimated to be over
1,500,000,000,000,000,000 kWh per year. That
is many thousand times more than all the
energy consumed by all the countries on this
planet. The Sun represents a tremendous
reserve of energy, surpassing that of all the
Earth’s energy sources.
The use of solar energy to produce elec-
tricity is called photovoltaics. Photovoltaic
(PV) cells, or solar cells, convert sunlight
directly into electrical energy. This technology
was initially developed in the 1950s at Bell
Laboratories. Sunlight causes the electrons to
move about in the solar cell. If the solar cell is
connected to a circuit, an electrical current is
produced.
Since there are no moving parts, these
units are very reliable, operate silently, and
have an expected life of 20 to 30 years. Since
the sun serves as the energy source, there is
no pollution.
When a number of the solar cells are
connected together they form a photovol-
taic module, Figure 24-13. Depending on the
number of solar cells used, PV modules are
sized by the number of watts they produce.
A PV module that is roughly 20″ by 20″ might
produce 1.63 A at 17.1 V and would thus be
rated at 27.9 W (P = EI).
A larger size might vary the number
of solar cells and be able to produce 190 W.
A 1 kWp (kilowatt peak output) module
Figure 24-12. The Segway® balances itself and
moves forward or backward by the rider leaning
slightly in the desired direction.