IEEE Power & Energy Magazine - May/June 2022 - 79

face of a building from external elements
(wind, rain, and so on). On the
south side, the solar radiation during
the winter was open, but was shaded in
the summer. This simple principle was
widely accepted and implemented not
only in private houses but also in public
buildings and the world famous Roman
baths. A picture of a Roman bath
is shown in Figure 3.
Photovoltaic
Development-A New Era
For centuries, we have used the power
of the Sun in several ways. But it wasn't
until the 1800s that scientific breakthroughs
allowed us to fully exploit the
potential of this free and abundant fuel
source. A French physicist named Edmund
Becquerel (Nobel laureate) published
his experiments conducted with
wet cell batteries in 1839, which led to
the transition to solar energy use.
In the 1800s, there was further support
for this discovery, but it took until
the mid-20th century for proof to be
made. A publication by William G.
Adams and Richard E. Day considered
the effects of sunlight on selenium, and
Charles Edgar Fritts developed a very
inefficient prototype cell (1%-2% efficiency)
during the late 1880s that
looked like a typical cell in use today.
A typical diagram of a modern PV cell
is shown in Figure 4.
To calculate the efficiency of PV
cells, one must measure the amount of
electricity generated using the total potential
energy received by the PV module.
In many ways, the prototype solar
cell resembles today's modern cells. Beneath
it was a glass sheath with a fine
chunk of gold wire sandwiched between
the glass and a thin layer of selenium.
This was the first model for further improvement
by scientists, but it would
take decades before efficiency improved
and a true understanding of the causes
of early low power is reached.
A lack of interest, a lack of knowledge,
or the low price of fossil fuels may
be behind the little development that occurred
in the half-century after the initial
discovery. The only notable event in
the first half of the 20th century that followed
the same trend was Max Planck's
new idea, his light quantum hypothesis.
An explanation of the photoelectric
effect was published by Albert Einstein
in March 1905. Five years earlier,
Planck had shown that atoms in cavities
can only absorb or emit radiation
from discrete " quantum, " which is why
the energy of each proton is an integer
multiple: frequency times new default
constant. Planck thus solved the problem
of blackbody radiation.
Planck believed that his conception
of quantum was nothing more than a
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IEEE Power & Energy Magazine - May/June 2022

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