Why don’t we cover the desert with solar panels? - Dan Kwartler
Every day, the sands of the Sahara Desert
reach temperatures up to 80° Celsius.
Stretching over roughly
nine million square kilometers,
this massive desert receives about
22 million terawatt hours of energy
from the Sun every year.
That’s well over 100 times more energy
than humanity consumes annually.
So, could covering the desert with solar
panels solve our energy problems for good?
Solar panels work when light particles hit
their surface with enough energy
to knock electrons
out of their stable bonds.
On their journey back to stability,
these electrons produce electricity.
However, there’s a limit to how much power
panels can generate.
Solar panels can only interact
with certain wavelengths of light,
making it impossible to convert
over half the sunlight they receive.
And even light particles they can convert
often bounce off them
without ever hitting an electron.
But thanks to clever scientists
and engineers
and substantial government investment,
solar panels are generating
more electricity than ever.
Anti-reflective coatings and patterns
on the panels’ surface
create more opportunities for incoming
light particles to hit electrons.
These techniques have increased commercial
solar panel efficiency
from the low-teens to 25%,
with experimental models reaching
up to 47%.
What’s more, solar has gotten
89% cheaper over the last decade,
thanks in part to global supply chains
for other technologies
that use the same materials.
Together, these factors have
made solar power
the cheapest source of electricity
on Earth.
Countries including India, China,
Egypt, and the US,
have already taken
these new panels into the desert.
Their massive solar farms range
from 15 to 56 square kilometers,
and when the sun is high in the sky,
these plants can provide energy
for hundreds of thousands
of local residents.
But these farms also get
extremely hot.
Light that solar cells don’t convert
or reflect is absorbed as heat,
which reduces a panel’s efficiency.
And the cooling systems employed by many
farms can use huge amounts of energy
powering fans or moving water
to maintain optimal temperatures.
Even with these systems, solar panels
in the desert absorb far more heat
than the natural sandy environment.
This hasn’t been a problem
on the scale of existing solar farms.
But if we tried to cover the Sahara,
this effect could create massive changes
in the region's climate.
Constructing solar farms already
disrupts local ecosystems,
but a plant of this scale could
dramatically transform
the desert landscape.
Thankfully, solar panels
aren’t our only option.
And some of the largest solar plants
in the world are trying a new approach:
giant mirrors.
Morocco’s Noor Power Plant,
which will eventually cover roughly
30 square kilometers of the Sahara,
is a concentrated solar power plant.
This design reflects light
onto a receiver,
which converts that energy to heat,
and then electricity.
These mirrors still create a dangerous
temperature shift for local wildlife,
but they have less potential
to transform the landscape.
And since it takes time for the materials
being heated to cool off,
these plants often continue producing
electricity past sunset.
Whether they use panels or mirrors,
industrial solar farms are often easy to
fit into existing energy infrastructure.
However, getting their electricity beyond
local power grids is much more difficult.
Some countries are working on ways to
connect electric grids across the globe.
And many farm store energy
in massive batteries,
or convert their electricity
into clean gas that can be used later.
But right now, these techniques are still
too expensive and inefficient to rely on.
Worse still, industrial renewables
can share some of the same problems
as fossil fuels,
relying on destructive mining operations
and carbon-emitting global supply chains.
Fortunately, solar can
exist on many scales,
from industrial solar farms
to smaller installations
that power individual buildings
and rural communities.
These projects can supplement energy use
or provide a passive source of energy
for regions off the grid.
And since solar panels rely
on a few simple components,
they’re quick to install
and relatively easy to update.
In fact, it’s this flexibility
that enabled solar
to become so cheap and ubiquitous
over the last decade.
So if we want to keep up with humanity's
rising energy use,
we'll need answers both big and small.
