Environmental Engineering Reference
In-Depth Information
ronmental or social problems. Unlike fossil fuels, the resource is ubiquitous,
which removes questions of monopolisation of energy supply. Solar energy
collectors can be spread over a wide geographical area, unlike a nuclear
power station, and terrorist strikes on a solar energy collector would not
cause massive environmental problems. In addition, a renewable energy
system is inherently robust because it comprises thousands of small collec-
tors rather than a small number of large, and potentially vulnerable, genera-
tion units.
Solar energy options
Solar energy includes both direct radiation (i.e. harnessing energy from sun-
light) and indirect forms of energy (such as biomass, wind, hydro, ocean
thermal, ocean currents and wave energy) caused by the effects of the sun on
Earth. Most of these energy forms will be part of the energy mix when solar
energy becomes the dominant traded-energy form. Some solar energy tech-
nologies are more advanced than others. The key to successful mass-utilisa-
tion of solar energy is diversity. The solar energy mix will vary from region to
region.
Photovoltaics, solar thermal energy (also called solar heat energy) and
wind energy are presently the only solar energy technologies that can
provide very large quantities of sustainable energy with high (more than 10
per cent) overall efficiency (Blakers 2000). These conversion technologies
have small environmental impacts and insignificant military applications. In
some countries biomass may also make a substantial contribution to energy
supply, despite low conversion efficiency.
Photovoltaics
Photovoltaics is the science of converting sunlight directly into electricity via
solar cells without the use of moving parts. It is an elegant but expensive
technology. It has found widespread use in niche markets such as consumer
electronics, remote area power supplies and satellites. Large numbers of
photovoltaic systems are being installed on house roofs in cities. The cost of
photovoltaic systems is not a strong function of scale, which means that
photovoltaic systems are often the most economical energy source for small
applications. Over 90 per cent of the world photovoltaic market is serviced
by crystalline silicon solar cells. This dominance is likely to continue for
many years.
