The ultimate source
of much of the world's energy is the sun, which provides the earth with
light, heat and radiation. While many technologies derive fuel from one
form of solar energy or another, there are also technologies that directly
transform the sun's energy into electricity.
The sun bathes the earth in a steady, enormous flow
of radiant energy that far exceeds what the world requires for electricity
electricity directly from sunlight does not deplete any of the earth's
natural resources and supplies the earth with energy continuously, solar
energy is a renewable source of electricity generation. Solar energy is
our earth's primary source of renewable energy.
There are two different
approaches to generate electricity from the sun: photovoltaic (PV) and solar-thermal
- Initially developed for the space program over 30 years ago, PV, like
a fuel cell, relies upon chemical reactions to generate electricity.
PV cells are small, square shaped semiconductors manufactured in thin
film layers from silicon and other conductive materials. When sunlight
strikes the PV cell, chemical reactions release electrons, generating
electric current. The small current from individual PV cells, which
are installed in modules, can power individual homes and businesses
or can be plugged into the bulk electricity grid.
- Solar-thermal technologies are, more or less, a traditional electricity
generating technology. They use the sun's heat to create steam to drive
an electric generator. Parabolic trough systems, like those operating
in southern California, use reflectors to concentrate sunlight to heat
oil which in turn creates steam to drive a standard turbine.
Two other solar-thermal technologies are nearing commercial status.
Parabolic dish systems concentrate sunlight to heat gaseous
hydrogen or helium or liquid sodium to create pressurized gas or steam
to drive a turbine to generate electricity. Central receiver systems
feature mirrors that reflect sunlight on to a large tower filled with
fluid that when heated creates steam to drive a turbine.
What are the environmental
systems operate without producing air, water or solid wastes.
as grid-connected central station systems, they require significant land,
which can impact existing ecosystems. Nevertheless, most PV installations
come in the form of distributed systems that use little or no land since
the panels are installed on buildings.
cells involves the generation of some hazardous materials. Nonetheless,
appropriate handling of these small quantities of hazardous material reduces
risks of exposure to humans and to the environment.
Like PV, solar-thermal
technologies generate zero air emissions, though some emissions are created
during the manufacture of both technologies. Water use for solar thermal
plants is similar to amounts needed for a comparably sized coal or nuclear
The biggest concern with solar technologies may be
...since five acres
of land are often needed for each megawatt of capacity. PV can eliminate
the land use impacts by integrating the generators into building construction,
eliminating the need for dedicating land use to PV generation.
Interstate Renewable Energy Council Site http://www.irecusa.org/
Million Solar Roofs http://www.millionsolarroofs.com/
Solar Energy Industries
American Solar Energy Society http://www.ases.org/index.html
Florida Solar Energy Center http://www.fsec.ucf.edu/
Natural Resources Defense Council Photovoltaic Fact Sheet http://www.nrdc.org/air/energy/fphoto.asp
North Carolina Solar Center (NCSU) http://www.ncsc.ncsu.edu/
Solar Electric Power Association http://www.solarelectricpower.org
Database: State Incentives for Renewable Energy http://www-solar.mck.ncsu.edu/dsire.htm
Union of Concerned Scientists: How Solar Works http://www.ucsusa.org/clean_energy/_renewable_energy/page.cfm?pageID=79
International Solar Energy Society http://www.ises.org/ises.nsf!Open
Solar Energy Society of Canada http://www.solarenergysociety.ca/2003/index.asp
Surface Meteorology and Solar Energy (NASA site)http://eosweb.larc.nasa.gov/sse/