Page 164 - Applied Photovoltaics

excellent ‘showcase’ opportunity for exposure of PV to large numbers of people. An
excellent example is the A9 motorway near Amsterdam Airport with a 220 kW p
system spread along 1.65 km (EC, 2002).
Solar powered boats are attractive for use in waters where fuel spillages are
particularly discouraged, such as on lakes, or where engine noise would detract from
the surroundings, such as in nature reserves. Two photovoltaic-powered shuttle boats,
each seating 24 passengers, began service between Lausanne and Saint Sulpice on
Lake Geneva in Switzerland in 1997. The vessels’ electric motors are operated by
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power generated by a photovoltaic array covering 14 m , located on the roof of each
vessel, providing environmentally-friendly public transport. On overcast days they
can be charged from the grid at the pier. The 27.5 m Bécassine carries 60 passengers
on a Swiss lake, powered by a 1.8 kW p photovoltaic array. Energy storage is in a
180 V, 72 Ah battery. Solar Sailor is a tour boat, operating on Sydney Harbour,
powered by photovoltaics, wind and an efficient, quiet compressed gas motor. The
‘sails’ are fibreglass aerofoils, with solar cells on the upper surface, that can be
oriented to optimise wind and/or solar power.
Photovoltaic-powered airships are an active research and development area, making
use of the large surface area for the mounting of low weight modules. Proposed
applications for solar-powered aircraft include cargo transport, telecommunications,
remote sensing and atmospheric measurement. NASA’s pilotless solar aeroplane
unfortunately crashed in 2003 but there are plans for a 20-day, around-the-world
flight of a PV-powered aeroplane with a solo pilot (Krampitz, 2004). That flight will
require up to seven stops unless the storage capacity of batteries is dramatically
improved.

8.12 SOLAR CARS

Solar car races provide a small but growing market, particularly for high efficiency
photovoltaic cells. Recent races include those held since 1987 in Australia and since
the early 1990s in the USA, Japan and Europe (Roche et al., 1997; Cotter et al., 2000;
WSC, 2004).
The efficiency of the photovoltaic cells is of prime importance for car races, owing to
the practical limitations on the physical area of photovoltaics useable. Price is often
no obstacle, with US$600/W p currently being charged for the best cells. The leading
cars in recent World Solar Challenge races have used extremely expensive cells made
from gallium arsenide and related material, usually only affordable for space
applications. Nevertheless, many top place getters are student cars built using
standard cells. The emphasis is on efficient vehicle design, including:
x aerodynamics (which is more important than weight)
x motor efficiency (often two motors are used)
x power conditioning and control circuitry
x battery storage densities and efficiencies.
It is likely to be many years before large numbers of regular commuter vehicles are
powered by photovoltaics, owing to the need for:
x cost reductions
x on-road compatibility with other vehicles, such as trucks

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