PRODUCT SPOTLIGHT - Solar Panels
Electricity-Producing
Solar Panels
Solar panels or, more
accurately, modular
panels comprising a
number of photovoltaic
(PV) cells, seem to be
appearing on more
and more roof areas
across the country
these days, reducing
consumers’ electricity
bills and in many
instances feeding
power into the
national grid.
Although they currently
make only a relatively
small contribution to
the country’s overall
energy needs, as the
use of PV cells grows,
this could become
more significant in the
future – especially as
an increasing number
of farmers and landowners are considering
their application in large
-scale “solar farms”.
Today’s advanced
solar panels only
need daylight and
not necessarily direct
sunlight to generate
electricity.
An average 1kW panel
installation in the UK
will generate around
800kWh over a year.
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So how do they work and what surface coatings
do they utilise to protect against the elements?
A photovoltaic cell converts solar radiation
into electricity. The basic technology involved –
sometimes termed the “Becquerel effect” – was
discovered in the 1880s by Alexandre-Edmond
Becquerel, a French physicist who studied the
solar spectrum, magnetism, electricity and
optics. Becquerel created the world’s first
photovoltaic cell using silver chloride placed
in an acidic solution,
which was illuminated
while connected to
platinum electrodes,
generating voltage and
current. Today’s cells
employ semiconductors.
The coatings on solar
cells are specifically
designed to absorb as
much energy from the
photons in light as they
can. This process is not
100% efficient and only
up to around 25% of the
light that hits a cell is
transferred into electrical
energy. The coating on
the cell helps to absorb
the light while the glass above provides
protection. The array of specially designed,
interconnected photovoltaic semiconductors
under the glass – there are normally hundreds
of them – produce the electricity.
In essence, two different types of semiconductor
are involved, a negatively charged one and a
positively charged one, placed on top of each
other with a junction between that acts as a
barrier between the two. Light striking the solar
cell creates a molecular reaction between the
two parts of the semiconductor, producing a
flow of electrons or current. This is collected
at junction points and directed to a main outlet
cable, usually connected to an inverter that
transforms the direct current produced into
an alternating one for domestic use.
The protective outer glass of a solar cell is itself
coated both for additional protection and to
enhance the transmission of the daylight.
May 2014
A “nano-coating” with hydrophobic (waterrepelling) and self-cleaning properties is applied
to some of the most advanced photovoltaic
panels. The coating’s self-cleaning glass effect
stops dust and bird faeces from sticking to the
panels, keeping them clean, maintaining their
efficiency and ensuring the maximum amount
of electricity is produced, and its hydrophobic
properties repel water more quickly than
uncoated “self-cleaning glass” which is also
used for PV panels.
“Self-cleaning glass” involves the use of a
coating based on titanium oxide, which also
has hydrophobic properties as well a photocatalytic effect that repels dirt and grime.
Anti-reflection coatings are also applied to
some PV panels. Untreated solar panels reflect
around 68% of the light exposed to it. This
means over 30% of the light, and potential
electricity, is reflected away and lost. A thin-film
anti-reflective coating on the glass – similar to
that used on spectacles – cancels out much of
the reflection, ensuring far greater transmission
of light and allowing the panel to absorb as
much as 95% of the light it is exposed to,
considerably increasing its efficiency.
Useful websites for further
information: www.ehow.com/howdoes_5369215_photovoltaic-cell-works
and www.nanoshell.co.uk/protectivecoatings
read online @ www.surfaceworld.com