Current solar technologies
Solar technologies – some primitive, some more advanced
– have been used in all ages and in every corner of
the world, but the invention and development of modern
solar technologies goes back only forty or fifty years.
By now the world has seen numerous practical demonstrations
that sophisticated solar-powered facilities can be built
and operated successfully as part of energy systems
ranging from the scale of an individual home, to a large
industrial or commercial complex, or even a whole city
or rural area.
As early as the 1980’s, a 354-MW solar power plant was
built in the Mojave desert, in California. Here the
heat contained in solar rays, concentrated by reflecting
troughs and raised to 400oC, produces steam that runs
a conventional power generator. When the sun is not
shining, the plant switches to natural gas. The latest
generation of this type of plant incorporates new engineering
solutions and new scientific principles such as non-imaging
optics, which makes it possible to build much more efficient
concentrators at lower costs. These developments open
new prospects for the technology in the sunniest parts
of the world.
A solar technology that has already had a great impact
on our lives is photovoltaics. Not in terms of the amount
of electricity it produces (in 1999 only 200 MW were
installed), but because of the fact that photovoltaic
cells – working silently, not polluting – can generate
electricity wherever the sun shines, even in places
where no other form of electricity can be obtained.
The technology has been around since the 1950’s, but
the effect on our lives is not widely known. As the
American solar-technology historian John Perlin observes,
it was the determining factor in a whole series of otherwise
unthinkable developments.
For instance, photovoltaic cells generate the power
that runs space satellites. Without telecommunications
satellites, many of our now-routine activities – from
watching internationally broadcast entertainment to
using cell phones – would still be in the realm of science
fiction. And space exploration and research too might
still be science fiction.
On earth, photovoltaic technology is used to produce
electricity in areas where power lines do not reach.
In the developing countries, it is significantly improving
living conditions in rural areas. Thanks to its flexibility,
it can be incorporated in packages of energy services
and thus offer unique opportunities to improve rural
health care, education, communication, agriculture,
lighting and water supply.
In the industrialised countries, programmes that provide
incentives for the incorporation of photovoltaic systems
in building roofs and walls have tallied up thousands
of completed projects in the United States, Japan and
Europe.
Annual worldwide sales of photovoltaic systems are growing
by around 30% and now stand at about one billion dollars.
The use of energy in the form of heat is one of the
largest items in the energy budget. In Europe, for instance,
it accounts for around 50% of total energy consumption:
around 630 million toe, of which 383 in low-temperature
heat and 247 in medium- and high-temperature heat.
Today, low-temperature (<100oC) thermal solar technologies
are reliable and mature for the market. Worldwide, they
help to meet heating needs with the installation of
several million square metres of solar collectors per
year.
These technologies can play a very important role in
advanced energy-saving projects, especially in new buildings
and structures that require large amounts of hot water,
heating and cooling.
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