Page 11 - A Comprehensive Guide to Solar Energy Systems

P. 11

Why Solar Energy?

Trevor M. Letcher
UNIVERSITY OF KWAZULU-NATAL, DURBAN, SOUTH AFRICA
trevor@letcher.eclipsr.co.uk

1.1 Introduction

The importance of the sun in sustaining life has probably been known to humans in all
ancient societies, and many of these people, including the Babylonians, ancient Hindus,
Persians, and Egyptians worshipped the sun. From written records, the ancient Greeks
were the first to use passive solar designs in their homes and no doubt experimented with
harnessing the sun’s energy in many different ways. There is a story that, Archimedes in
the 2nd century BC reflected the sun’s rays from shiny bronze shields to a focal point and
was thus able to set fire to enemy ships. The Romans continued the tradition of using the
sun in their homes and introduced glass, which allowed the sun’s heat to be trapped. The
Romans even introduced a law that made it an offence to obscure a neighbor’s access to
sunlight.
By contrast, PV technology (the creation of a voltage by shining light on a substance)
and the main focus of this book, is a very recent application. Scientists, as early as 1818,
noticed that the electrical conductivity of some materials, such as selenium, increased by
a few orders of magnitude when exposed to sunlight; however, it was not until the 1950s
that scientists working on transistors at the Bell Telephone Laboratories showed that sili-
con could be used as an effective solar cell. This very soon led to the use of silicon solar
cells in spacecraft; and in 1958, Vanguard 1 was the first satellite to use this new invention.
This application paved the way for more research into better and cheaper solar cells. The
work was further encouraged after the rapid oil price rise in the 1970s. In 1977, the US
Government created the National Renewable Energy Laboratory. A further indication of
the rapid rise of silicon solar cell technology was the building of the first solar park in 1982
in California, which could generate 1 MW; this was followed a year later by a larger Cali-
fornian solar park, which could generate, at full capacity, 5.2 MW. The United States has
now built several PV power plants in the range of 250–550 MW. It is amazing to think that
just 34 years after the first solar farm was built in California, China has built a solar farm of
850 MW. Furthermore, the solar PV worldwide generating capacity, at the end of 2016, was
in excess of 300 GW. To put this into perspective, 1000 MW (1 GW) is the power generated
by a traditional fossil-fueled power station.

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