Environmental Engineering Reference
In-Depth Information
of an optically very successful photovoltaic system that produces an output of 4.2
kilowatts, which provides most of the power needed for charging the batteries.
In addition to its climate-compatibility, this solar boat also offers other environmen-
tal benefi ts. It runs very quietly and, unlike conventional diesel engine ships, does
not emit unpleasant exhaust fumes. The construction of the ship only causes minimal
waves and, as a result, does not contribute towards any further erosion on the lake's
shores.
Figure 14.14
The Helio solar ferry has been crossing Lake Constance since 2000.
Photos: Bodensee-
Solarschifffahrt, www.solarfaehre.de.
14.4.3 World Altitude Record with a Solar Aeroplane
Hot-air balloons were the fi rst fl ying machines people used. Fire from fi rewood or
straw produced the hot air needed for the carbon-neutral powering of a balloon.
Today hot-air balloons are usually powered by natural gas burners. However, these
balloons are highly unsuitable for freight transport or regular services. Without
exception, propeller and jet-powered airplanes rule commercial aviation. The kero-
sene used is produced from oil, so the prospect of climate-friendly air travel is still
a long way off.
But an unmanned light aeroplane called Helios, after the Greek sun god, shows that
fossil fuels and fl ying do not have to be inextricably linked (Figure 14.15). The
plane was developed by NASA and the California company AeroVironment and
had its maiden fl ight in 1999. A total of 62 130 silicon solar cells with an effi ciency
of 19% are located on the wings, which have a span of 75.3 m and a depth of 2.4 m.
These solar cells deliver the energy for 14 electric engines with a total output of 21
kilowatts. Powerful lithium batteries enable the plane to fl y even after sunset.
Due to the low power output, the fl ight speed at low altitudes did not even reach
45 km/h. However, the performance of this aeroplane is not attributed to its speed
but to its fl ying altitude. Flying over Hawaii at an altitude of 29 524 m on 13 August
