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Advantages of solar energy
(1) Solar energy is common: the sun shines on the
earth, whether land or sea, mountains or islands.
Sunlight is everywhere and does not require
extraction or transportation.
(2) Solar energy is reliable: the development and
utilization of solar energy will not pollute the
environment. It is one of the cleanest forms of
energy, and with the growing concern over
environmental pollution, this is extremely valuable.
(3) It is significant: every year the sun reaches
the earth's surface with radiation equivalent to
about 130 trillion tons of standard coal. This total
is now the world's largest energy source that can be
developed.
(4) It lasts a long time: according to the current
estimated rate of nuclear energy generated by the
sun, the sun has hydrogen storage sufficient to
support it for billions of years. Since the life
expectancy of the earth is also billions of years,
in this sense it can be said that the sun's energy
is inexhaustible.
Disadvantages of solar energy
(1) Solar energy is disperse: though the total solar
radiation reaching the Earth's surface is great, the
energy flux density is very low. On average, near
the Tropic of Cancer, given sunny summer weather and
at noontime, the greatest possible irradiance of
solar radiation with sunlight in the perpendicular
direction, one square meter area would receive on
average about 1000W of solar energy; the average
energy day and night throughout the year is only
about 200W. Roughly half this reaches the surface in
the winter, while on a cloudy day only about 1/5 of
this reaches the surface. This energy density is
very low. Therefore, the conversion of solar energy
to power often requires a fairly large area for the
collection and conversion equipment, at a high cost.
(2) Solar energy is unstable: due to the differences
between day and night, the seasons, geographic
latitudes, and altitude restrictions, as well as
other natural conditions like weather and other
random factors, a certain parcel of land has
intermittent solar irradiance. This instability
makes the large-scale application of solar energy
more difficult. To make solar energy a continuous
and stable form of energy, which eventually becomes
able to compete with conventional energy sources,
alternative energy storage must be used so that as
far as possible the days of solar radiation are
stored up for use at night or on a rainy day. Also,
the utilization of solar energy storage is one of
the weaker links.
(3) Solar energy has low efficiency and high cost:
at the current level of development of solar energy,
some aspects of the theory are feasible and it is
technically mature. However, given the low
efficiency and high cost, in general, of solar
energy installations, it can not compete with
conventional energy sources. A considerable period
of time in the future, solar energy may be developed
further, mainly because of economic constraints.
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