A
s the search for renewable and carbon-
neutral forms of energ y intensifi es, solar
energ y is leading the way for aircraft. One
aircraft soaring through boundaries is the Solar
Impulse 2. This incredible machine has just
fi nished a non-stop round-the-world trip powered
only by the Sun. It used its 72-metre- (236-foot-) wide
w ings, each of which carr y ing over 8,500 solar cells,
which were used to power four electric motors and
four lithium batteries. Despite this astonishing
w ingspan, the entire aircraft only weighs 2,300
kilograms (5,071 pounds) – about as heav y as a large
great white shark.
A nother major player in the world of solar
powered av iation is Solar Flight. Their newest
project is Sunseeker Duo, which is the only
two-seater solar-powered aeroplane in operation.
It follows a similar pattern to the Solar Impulse 2,
w ith long w ings covered w ith solar panels and a
lightweight body. Its panels have been improved to
become 50 per cent more effi cient than their
predecessors. It can fl y for 12 hours and its engine
produces 25 kilowatts (33.5 horsepower) of power.
The main question w ith using solar power is
‘what happens at night?’ During the day, not all the
energy is used. Enough will be stored in the
batteries to allow the aircraft fl y at night.
The Solar Impulse 2 landed successf ully on the
3rd of July 2015, and marked a huge achievement for
alternative energ y. The next challenge for
solar-powered aviation is to be able to carry
multiple passengers, so hopefully one day tourists
can use the Sun on their way to soaking it up.The fl ying machines that are fuelled only by the Sun
Solar-powered aircraft
How exactly do solar panels convert sunlight
to energ y? Inside a solar panel is a number of
silicon cells, placed on top of each other. One
of the silicon atoms has all its electrons, while
the one beneath it has a few missing. In order
to restore the balance, the f ull silicon
atom transfers electrons to the
one below, but it needs light
to trigger the process.
Once the sunlight hits
the panel, electrons are
transferred from one
silicon cell to the other,
thus creating an
electric current that
powers a load.How solar
panels work
How the Solar Impulse 2 gets off the
ground and stays thereAnatomy of a solar aircraft
The cockpit
The cockpit is only 3.8m3
(134ft3), so it will be fairly
cramped but essential for the
lightweight design.Lift
The plane will rise to 8,500m
(27,887ft) during the day to
make the most of the power
and then drop to 1,500m
(4,921ft) at night.Insulation
To keep the pilot from
suffering in the +40 to -40°C
(104 to -40°F) temperature
change, the cockpit uses
thermal insulation.Wings
The wingspan of the plane is
a total of 72m (236ft),
stretching wider than a
jumbo jet’s wings.Batteries
There are four rechargeable
lithium polymer batteries
inside the plane, weighing a
total of 633kg (1,396lb) that
provide the 50kW (70hp) power.AIR