Environmental Engineering Reference
In-Depth Information
Electricity production from photovoltaics has been increasing at an
average rate of 25 per cent per year over the past decade, which is far in
excess of the growth rate in energy consumption. Rapid growth in produc-
tion is causing steady reductions in cost, which will eventually lead to a true
mass-market developing. The current value of annual photovoltaic system
sales worldwide is about A$7 billion per year. Australia manufactures about
5 per cent of the world's solar cells.
Solar thermal energy
Solar thermal energy can be harvested in many forms, including high tem-
perature steam, warm air and hot water.
Solar thermal electricity
Most solar thermal electricity technologies use mirrors to concentrate sun-
light onto a receiver. The resulting heat is ultimately used to generate steam,
which passes through a turbine to produce electricity. Two non-concentrat-
ing exceptions are solar chimneys and solar ponds. Concentrator methods
are equally applicable to concentrating photovoltaic systems. The usual ways
of concentrating sunlight are point focus concentrators (dishes), line focus
concentrators (troughs, both reflective and refractive) and central receivers
(heliostats and power towers).
Solar thermal electricity is not yet a commercial proposition. The reason
for this is that, unlike photovoltaic, there are strong economies of scale. This
means that small systems that might be suitable for an individual household
are far too expensive. This lack of a niche market, in contrast to photovolta-
ics, inhibits the development of solar thermal electricity in the short to
medium term.
High temperature solar heat
Concentrated solar energy can achieve the same temperatures as fossil and
nuclear fuels, either directly (using mirrors) or through the use of chemicals
(thermochemicals or bio fuels) created using solar energy. One problem for
high temperature solar heat is that heavy industry (e.g. the steel industry) is
often located near coalfields, in regions that are relatively poorly endowed
with solar energy. Perhaps the next steel mill could be built in the Pilbara
region of Western Australia, close to iron ore deposits, rather than on the
