We sure love our roads. 
We love them so much that we seem
determined to pave the entire world.
But maybe roads can become the
future of renewable energy. 
That’s right, roads as energy generators.
How?
By building them with solar panels. 
In 2017, the United Kingdom promised to
run on 100% renewable energy by 2025.
Yet, they still have a long way to go, 
with only 33% of their energy having come from 
renewable sources in 2018.
Could solar panel roads be the answer?
Energy is created when photons from the Sun
hit a silicon solar panel. 
Silicon is a semi-conductor and has similar
properties to metal and an electrical insulator.
So when the Sun's photons
hit the silicon atoms on a solar cell,
they transfer their energy to loose electrons,
which knocks them off the silicon atoms. 
This generates electricity.
Sounds good for the solar industry. 
However in 2019, 
out of the 17,127 terawatt-hours (TWh)
of renewable energy created globally,
only 3% came from solar.
Turning our abundance of roads into
energy creating thoroughfares 
could move solar to the fast lane for 
renewable sources. 
In 2016, Waywatt built a 1km (0.6 mi) 
solar roadway. 
It generated about 280 
megawatt-hours (MWh) per year.
That's enough energy to power 
25 homes for 12 months.
The United Kingdom has around 
400,000 km (248,548 mi) of road.
If 20% of those roads were converted, 
that would equal around 81,000 km 
(50,000 mi)
of new solar panel paved roads. 
The energy from those roads
would only account for 5% of the UK’s 
total energy consumption in a year. 
The price tag? 
Well, a 1 km (0.69 mi) road in Normandy, France, 
cost €5 million, or approximately 
$5.5 million U.S., to build. 
That's enough to burn a sizeable hole
in a city's wallet.
So let’s hope the cost for solar technology
goes down before attempting to build an
81,000 km (50,000 mi) stretch. 
The largest change, 
and the reason behind creating solar roads, 
is the reduction of carbon dioxide (CO2), 
the biggest driver of global climate change. 
Many roads are currently paved in asphalt.
which increases heat on the road 
and surrounding areas.
A phenomenon called the 
urban heat island effect.
Switching over to solar roads 
would reduce this effect, 
creating cooler roadways 
and cooler cities. 
As these solar roads stretched 
over more of the globe,
the coal industry would have to 
shutter its doors.
And we would need less petroleum 
for asphalt production.
Many people would lose their jobs. 
Governments would need to create programs
to retool the workers for the growing 
demand of solar road construction. 
Then there’s the roads themselves. 
To build these roads,  
solar panels are placed between layers of glass, 
silicon rubber, and concrete.
This makes for a slippery road,
especially during rain or snow.
The roads would need a durable coating 
to create traction, 
and that coating would have to be safe 
for the environment and humans.
Or would we develop improved car tires 
from another material to better 
grip road surfaces?
Another route is to create smart solar roads. 
These roads would include technology to 
keep its surface above freezing,
charge electric cars as they drive, 
and use LEDs for bright road surface markings. 
There are a lot of roadblocks for 
this new technology. 
Cost, material, and safety being the big ones. 
But is it worth it to invest in
research and development?
In 2014, the Netherlands built a solar bike path.
This 70 meter (220.6 ft) bike path 
generated 3,000 kilowatt-hours (kWh).
In other words, 
the solar bike path could power a small 
household for one year. 
Talk about recycling your carbon footprint
in a powerful way.
Despite current limitations, 
solar paved roads might still be
a possibility in our future. 
Though there are other ways
to use solar panel technology
for renewable energy.  
Why ground our thinking earthbound?
For instance, there is a lot of open space
up on our Moon. 
Is it possible to install solar panels 
on the Moon, 
and for us to access that energy? 
That’s a story for another What If.
