Global solar energy production
is significantly reduced
due to dust on solar panels
and airborne pollution
blocking sunlight.
A 2017 study found that,
airborne particles
and their accumulation
on solar cells
are cutting energy output
by more than 25%
in some parts of the world.
The regions bit hardest
are those investing the most
in solar energy installations:
China, India and the
Arabian Peninsula.
The study appeared online,
on June 23, 2017,
in Environmental Science
& Technology Letters.
“My colleagues in India
were showing off
some of their rooftop
solar installations,
and I was blown away
by how dirty
the panels were,”
said Michael Bergin,
professor of civil and
environmental engineering
at Duke University
and lead author of the study.
“I thought the dirt
had to affect their efficiencies,
but there weren’t any studies
out there estimating the losses.
So we put together
a comprehensive model
to do just that.”
With colleagues at the
Indian Institute of
Technology-Gandhinagar
and the University of Wisconsin
at Madison, Bergin measured
the decrease in solar energy
gathered by the solar panels
as they became dirty over time.
The data showed
a 50% jump
in efficiency each time
the panels were cleaned,
after being left alone
for several weeks.
8% of the grime was carbon
and other pollutants
from human activity.
“The human made particles
are also small and sticky,
making them
much more difficult
to clean off,”
said Bergin.
“You might think
you could just clean
the solar panels more often,
but the more you clean them,
the higher your risk
of damaging them.”
Grimy buildup on solar panels
isn’t the only thing blocking sunlight
— ambient particles in the air
also have a screening effect.
The NASA GISS
Global Climate Model
already accounts for the
amount of the sun’s energy
blocked by different types
of airborne particles
and estimates the amount
of particulate matter
deposited on surfaces
worldwide.
The resulting calculations
estimated the total loss
of solar energy production
in every part of the world.
While the U.S.
has relatively little
migratory dust,
more arid regions
such as the
Arabian Peninsula,
Northern India
and Eastern China
are looking at losses
of 17% to 25%,
or more, assuming
monthly cleanings.
If cleanings take place
every two months,
those numbers jump
to losses of 25% to 35%.
The Arabian Peninsula
loses much more solar power
to dust than it does to
human made pollutants,
Bergin said.
The reverse is true
for regions of China and India.
This work was supported
by the US Agency for
International Development
and the Office of the Vice Provost
for Research at Duke University.
92% of the dust on each panel
was natural, but the 8%
human made particles
are smaller and stickier --
so the 8% blocked as much
solar energy as the 92%.
Pollution and natural dust
will slow the clean-energy future
in India and China unless they get
auto-cleaning solar panels.
Solar panels work best
when clean,
near the equator,
not under many clouds,
and when electricity demand
peaks at 12 noon
( which, unfortunately
does not happen
in any modern country ).
REFERENCE
Bergin, M.H., Ghoroi, C., Dixit, D.,
James Jay Schauer, Drew Shindell. (2017)
Large reductions in solar energy production
due to dust and particulate air pollution.
Environmental Science & Technology Letters,
2017; DOI: 10.1021/acs.estlett.7b00197
PS: Let me add
the following problems
that would also reduce
solar panel efficiency:
(1) Moss / mildew growth,
(2) Bird doo doo, and
(3) Hail storms !