The human population has now crossed the 6.5 billion mark, and the world is starting to
show the strain we humans place on it. 6.5 billion people need a great deal of energy to run their
3.3 billion cell phones and over half a billion cars, but the planet has a limited supply of energy
that was built slowly over four billion years. This is why solar power has captured the attention
of all but those whose fortunes are tied to the success of non-renewable energy sources. Along
with wind, wave, and thermal energy, solar power is an element of the renewable energy class.
Barring a failure of our sun, solar power can never diminish in intensity or availability. In
addition, generation of solar power does not detract from the environment, whereas most other
sources of power emit toxins and pollution that do, causing solar power to be a commonplace
Despite its prevalence, most people do not understand the inner workings of a solar panel.
A solar panel is a large array of solar, or photovoltaic, cells. The word photovoltaic is derived
from the words “photo”, meaning light, and voltaic, meaning “producing electricity”. This is
clearly the essence of a solar cell. In general terms, light shines on a semiconducting material,
which produces free electrons, which in turn follow an electric field to create a current. The
detailed explanation of a solar cell will follow this chronological order, beginning with the most
essential factor: light.
The sun produces an infinite supply of light at the earth, with an intensity of around 300
, which, when collected by a decently-sized solar panel, is more than enough to power
the average US home, which uses power at a rate about 1.2 kW
. Commercial solar panels
have about 20% efficiency
, resulting in a necessary 20 m
to power the average US home.
The seemingly low efficiency is actually near on par with the internal combustion engine, which
provides near 30% efficiency. However, the low efficiencies exist for different reasons. The low