16 September 2016
an opening to allow sunlight to focus on the P-N junction
where the incident photon energy creates hole-electron
pairs. The electrons migrate into the N-material creating
holes in the P-material which causes an electrically neutral
zone called the depletion layer or region. The separation
of charges across the depletion layer creates a voltage
of 0.5 to 0.6 VDC. If the solar cell’s metallic contacts are
connected to a load, a small current flows (approximately
three amps at 0.5 VDC with full insolation of 1,000 watts/
Solar cells produce a fair amount of current, but not
enough voltage to be useful. So, many individual cells are
connected together in series banks to increase the overall
voltage output, and a number of banks are connected in
parallel modules to increase the overall current output. A
number of these solar modules are connected in series-parallel arrays to further increase the volt and current
The solar arrays are enclosed in metal frames with glass
covers for protection from the environment’s elements
(rain, sand, etc.), and are called solar panels. Figure 8
shows a 4 x 3 solar panel where you can see the individual
solar cells as the small squares and the arrays with a 6 x
10 arrangement of 4 inch x 4 inch solar cells. Solar panels
seem like the way to go for protecting the environment
but if we look into the solar cell manufacturing processes,
we see the use of corrosive materials such as sodium
hydroxide and hydrofluoric acid. Plus, some green house
gases are generated, and the necessary energy to melt
sand to make the solar cell wafers comes into play.
However, the overall effect of using solar photovoltaic
energy has a smaller carbon footprint than that of fossil fuel
This type of generated energy uses wind blowing
through wind turbines which rotate and turn electrical
generators. To make wind energy economically feasible,
you have to have a consistent wind velocity of 10 to 13
miles per hour. Wind turbines are installed as high as
possible above the local terrain to maximize the wind
speed. Additionally, the wind turbines need a mechanism
to “feather” the turbine blades during periods of high
winds to prevent damage. The turbines are also notorious
for killing raptor birds.
Figure 9 shows a number of wind turbine electrical
generators arranged over several acres to form a wind farm.
Most wind farms are located in the Plains States and Rocky
Mountain States in the US. The only carbon footprint for
wind energy comes from constructing the wind turbines,
towers, and generation/storage systems. Wind energy can
be scaled to the point that you can build your own roof top
system, but be aware that the turbines can be fairly noisy.
Tidal and wave energy use the ebb and flow of the
oceans to generate electricity. Wave energy uses the short
n FIGURE 8. Solar photovoltaic panels.
n FIGURE 10. Wave energy electrical generation system.
n FIGURE 9. Wind power farm at the Alta Wind Energy
Centre (AWEC) in Tehachapi (Kern County), CA which
generates 1,550 megawatts of electrical power.