Environmental Engineering Reference
In-Depth Information
electricity is attractive. On the East coast of the United
States where my daughter lives, electricity costs
cents
per kilowatt-hour and solar is unattractive. As time goes on
perhaps there should be new types of systems available at
lower cost and PV systems may become more attractive.
As of now, they are only for rich countries.
There is an exception to this. If you are a poor country
without a well-developed electrical grid and large power
plants, it can be advantageous to use small solar systems at
the village level. Electrifying schools and supplying
recharging for the cell phones of farmers can offer great
bene
ts at low costs.
Solar thermal electric generation is the second solar
electric system. This technology is more typically used in
systems much larger than those on roof tops.
Figure
shows an example of a system installed in the state of
Nevada. The curved mirrors form long troughs that focus
the sunlight on a tube that carries a
.
fluid that is heated to
a high temperature. The long axis of the system runs
north
south and the troughs rotate to follow the Sun
from east to west.
In principle, if the insulation on the tube was perfect,
the
-
fluid could reach the same temperature as the surface
of the Sun,
C. These systems are used to generate
steam to run electricity-producing turbines and typically
heat the
C. The overall
fluid in the tube to
to
electrical ef
%, better than
all but the most exotic (and expensive) solar PV cells.
ciency is typically
%to
California also has a program for large PV systems more typical of
commercial applications. The rules are too complicated to
summarize here.
