Environmental Engineering Reference
In-Depth Information
electrodes of a saline battery were exposed to sunlight. Becquerel was generally more
interested in photography and optics than electricity, and he did not capitalize on his
discovery. That honour fell to an American, Charles Fritts, who patented the first solid
device able to convert sunlight into electricity in 1883. While Fritts's solar cell, based on
the same principle as modern photovoltaic (PV) panels, represented a breakthrough, it was
far too inefficient to be commercially viable, especially as far cheaper sources of electricity
- fossil fuel and water-powered - were available.
It was not until the 1950s that solar electricity came into use, in an application that
was appropriately futuristic: space exploration. Whereas the high research and production
costs of solar panels prohibited their use on Earth, in space they represented the only
a compelling argument for the further development of PV panels. Instead of relying on a
chemical battery that could last at most a couple of weeks, Vanguard 1 was able to transmit
data from space to Earth for six years (from 1958 to 1964) thanks to solar cells mounted
on the exterior. This success raised both public and scientific interest in the potential of
solar power. Within a decade, the first terrestrial applications were appearing on oil rigs
and pocket calculators.
How a Solar Cell Works
The development of solar PV cells coincided with the information revolution. This was
not an accident, as PV cells share with all electronic devices a key component: the
semiconductor. As the name suggests, semiconductors are elements or combinations of
elements that conduct electricity, but only under certain conditions. Some semiconductors
- such as the selenium used by Charles Fritts - are elemental. Others are synthesized
by enriching natural semiconductors with other elements to magnify the semiconductor
effect, a process known as doping. Whereas metals (such as iron, copper, and gold) release
electrons, thereby conducting electricity, and non-metals (such as oxygen, chlorine, and
iodine) adopt electrons, thus insulating against electron flow, semiconductors both conduct
and insulate.
Though it sounds unspectacular, this characteristic is the lynchpin in all electronic
devices, from mobile phones to the International Space Station. Because semiconductors
allow us to switch the flow of electrons on and off at will, sequences of electric charge can
be configured and stored. A semiconductor layer, such as that in a hard drive, is 'inscribed'
with a unique combination of positive and negative charges, which can then be 'translated',
using software, into another form of information: a text, an image, computer code, or a
piece of music. This effect is often explained in terms of the digits 1 and 0 (binary code).
