7
When you accelerate,
the battery powers elec-
tric motors that allow
the wheels to spin and
create forward motion.
When you brake, the
motors become gen-
erators that harvest
the kinetic, mechanical
energy created by thecar’s movement and
transform it into electri-
cal energy.
The electrical energy is
sent back to the battery
and stored as potential
energy for the next time
the car accelerates.
In cars with combus-
tion engines, up to 70percent of the kinetic
energy created by mov-
ing downhill is lost as
heat. EVs do lose some
kinetic energy from
movement and heat
loss, but Tesla says
regenerative braking
is about 90 percent
efficient.now carrying 65 tons of ore. To
rectify that scenario, the truck’s
regenerative braking system actu-
ally recaptures the energy created
by going downhill, refilling the
battery’s charge for the next time
the truck travels uphill.
For a crash course in regener-
ative braking, think back to high
school physics. Kinetic energy
is created through motion, and
potential energy is stored because
of its placement relative to other
objects. You can experience this
in gasoline-powered vehicles, too.
The kinetic energy is created by a
spark and the ignition, but while
rolling down a hill, a vehicle cre-
ates more energy due to gravity.
Regenerative braking, then,
takes kinetic energy and trans-
forms it into electrical potential
energy that is stored back in the
battery. Other factors—the truck’s
weight, load, vertical position, and
gravitational pull—dictate how
much energy can be transformed
and stored. The same process is
used in other electric vehicles, like
the Honda Clarity plug-in hybrid.
“Rock trucks” like the Komatsu
HD 605-7 haul marlstone, a type of
lime-rich mudstone readily found
in the sides of Swiss mountains.
The cement trade relies on this raw
material; these trucks transport it
directly to their factories.
While the eDumper can go days
without charging, an eMining AG
rep says the truck still needs a
good jolt from time to time if you
put it through a rigorous workout.
Frequently hitting the brakes, for
example, may take up too much
energy due to the mechanical
parts moving.
While EVs are quickly prolif-
erating throughout the United
States, the serious work in the
trades is still done by gas-guzzling
diesel engines. And according
to the World Economic Forum,
How Regenerative
Braking Worksan international organization
for public-private cooperation,
heav y industry and transport
will account for 15.7 gigatons of
carbon emissions by 2050 if left
unchecked.
The eDumper is a good start,
but it isn’t just a science experi-
ment—it’s already hauling tons of
rocks from a quarry on the slopes
of the Chasseral to the CimentsVigier SA cement factory near the
Swiss town of Biel.
Making the trip from quarr y to
factory 20 times a day produces a
surplus of 200 kilowatt-hours of
energy (or 77 megawatt-hours per
year), says the eMining AG rep.
Your average dump truck, by con-
trast, uses between 11,000 and
22,000 gallons of diesel fuel each
year. You do the math.BRAKESBRAKES
ELECTRIC
MOTORSBATTERYWHEEL WHEEL28 December 2019