Civil Engineering Reference
In-Depth Information
FIGURE 12-1
Photovoltaic stand-alone power system with battery.
inverter converts the DC power of the array and the battery into 60 or 50 Hz
power. Inverters are available in a wide range of power ratings with effi-
ciency ranging from 85 to 95 percent. The array is segmented with isolation
diodes for improving the reliability. In such designs, if one string of the solar
array fails, it does not load or short the remaining strings. Multiple inverters,
such as three inverters each with 35 percent rating rather than one with
105 percent rating, are preferred. If one such inverter fails, the remaining two
can continue supplying essential loads until the failed one is repaired or
replaced. The same design approach also extends in using multiple batteries.
Most of the stand-alone pv systems installed in developing countries pro-
vide basic necessities, such as lighting and pumping water. Others go a step
further (
Figure 12-2
)
.
12.2
Electric Vehicle
The solar electric car developed in the U.S.A. and in many other countries
is an example of the stand-alone (rather the move-alone) pv power system.
The first solar car was built in 1981 and driven across the Australian Outback
by Hans Tholstrup of Australia. The solar car has been developed and is
commercially available, although more expensive than the conventional car
at present. However, the continuing development is closing the price-gap
every year.
A new sport at the American universities these days is the annual solar
car race. The DOE and several car manufacturers sponsor the race every two
years. It is open to all engineering and business students, who design, build,
and run their car across the heartland of America. The first U.S. solar car
race was organized in 1990.
Figure 12-3
shows one such car built by the
University of Michigan. In 1993, it finished first in the 1,100-mile “Sunrayce”
that began from Arlington, Texas, and cruised through Oklahoma, Kansas,
Missouri, Iowa and ended in Minnesota. It covered 1,102 miles in six and a
