Solar energy refers to forms of energy emitted by the sun, including
light, radio waves, and x-rays. Accounting for 99.8 percent of the mass in our
solar system, the sun is a self-sustaining nuclear fusion reaction by which hydrogen
is converted to helium. Every second, the sun converts over 4 million metric
tons of matter into solar energy. This matter is converted and released from
the sun in the form of radiation waves that travel through the void of space
and eventually reach earth. The radiant energy that eventually reaches the
earth’s surface is estimated around 1,000 watts per sq. m. The sun is similar
to a fusion reactor that emits 3,800 million, million, million, million watts
of energy each second, which is 20,000 times the energy requirement of the
world.
Solar power, as an alternative fuel, involves transforming some of the
sun’s massive thermal energy into electricity. Individuals driven by
environmental and other concerns encourage the implementation of policies that
require the use of solar and other renewable energies. Solar energy can be
broadly classifed in two categories on the basis of its use: active and
passive.
Active Solar Energy
Active solar energy can be converted to electricity and used directly, as
in the case of solar heating applications and solar photovoltaic (PV)
applications. In a PV cell, sunlight strikes a layer of semiconductors, which
in turn creates an electrical current. By 2005, this proven technology was
being used to provide heat and power to well over 650,000 homes, primarily in
the United States, Germany, and Japan. Electricity can be produced from solar
power by placing solar panels on roofs. These panels consist of PV cells that
can convert sunlight directly into electricity. Moreover, electricity produced
as solar power during the day may be stored in batteries for use at night.
Another method of electric generation employs the use of turbines. In
turbines, the sun’s heat can be used to convert water into steam and then this
steam is used to run turbines. The turbines, in turn, run generators, which
produce electricity. Solar PV applications have found many uses in rural areas
for multiple activities besides home lighting. Remote villages deprived of grid
power can be easily powered using solar photovoltaic technology. The economics
of rural electrifcation can be attractive considering the high cost of power
transmission and erratic power supply in rural areas. From portable indoor uses
such as calculators, to generating plants alongside railways and roads, PVs are
adaptable. They easily function across most areas in both the Northern and
Southern Hemispheres.
Passive Solar Energy
Passive solar thermal technology is employed for collecting and
converting the sun’s energy to heating applications such as water and air
heating, cooking and drying, steam generation, and distillation. To accomplish
this, a solar thermal collector device absorbs and stores heat. Solar thermal
technology requires good heat conducting materials, insulation, and reflectors.
Solar geysers, solar concentrators, and solar cookers are some examples of
devices based on solar thermal technology.
Also, solar energy can be put into use by incorporating appropriate
designs in buildings to maximize utilization of solar energy for various
purposes such as lighting, air conditioning, and water and space
heating/cooling and thereby reduce external energy inputs. PV cells require
high exposure to direct sunlight. To assure maximum exposure to the sun
throughout the day, a phyrheliometer is used to calculate how much sun exposure
a location experiences. This information is useful in determining whether or
not a specific location issuitable for solar energy, as well as what direction
the cells should face. In many cases, these cells are placed on rooftops.
Use And Development
Increasingly, PV cells are being added to residential and commercial structures.
Tis approach to using solar energy is modular, as panels can be added to any
existing structure with sufcient exposure to sunlight. In addition, photovoltaic
cells are able to tie directly into the existing electrical grid, thus avoiding
the need to build additional transmission lines. In cases where the solar
energy provides more energy than any one location can use, it can actually
supplement the electrical grid with additional power to be used elsewhere. In such
cases, the electric company is required to pay the individual the same amount they
would charge per unit of electricity. Therefore, rather than being billed for
using electricity from the
grid, the
individual could actually receive a check from the electric company for any
power that was sold to the grid. Tis helps offset the initial cost of installing
solar cells.
Different groups perceive the issue of
solar energy differently. Advocates see solar energy simply as another
fuel to plug into the existing energy system and do not feel that it carries
any social or political relevance. They argue that the removal of conventional
impediments to the diffusion of solar power, such as
financing or getting high-quality installation on new devices, leads to
substantial growth in the solar energy market. Solar advocates tout the
technology as environmentally benign, and believe it will be an important part
of the solution to the structural problem of energy-related pollution. Other
groups maintain that there are too many barriers for solar energy to be a large-scale
option in the immediate future.
Economic barriers have stood in the
way of using solar energy because of the high price of solar equipment.
However, technological advances and economies of scale are making PV
electricity production steadily more cost-effective. The market for solar power
is growing, primarily overseas, where two billion people, most in developing
countries, still live without electricity. In countries where energy from the
sun is abundant, a small PV panel on a house can create enough power for two
light bulbs, a television, and a radio. With installation costs of $400–$600
per house and low maintenance, these solar panels already appoint thousands of
rooftops in India, Indonesia, Mexico, and Brazil. In addition to residential
buildings, many commercial buildings are now starting to add photovoltaic
cells, as well. Large areas such as rooftops of office buildings are ideal
places for these cells, as they are otherwise wasted space. They are also high
enough to avoid any obstructions that might block exposure to the sun.
Growth Of A New Industry
The solar PV
industry grew at an annual rate of over 20 percent worldwide in the past
decade, and 40 percent from 2007–07, reaching an annual PV module production of
100 megawatts (MW) in the United States and about 400 MW globally. Worldwide,
in 2001, photovoltaics were a $2 billion business. In the United States alone,
the industry employs about 20,000 people in high-value, high-tech jobs. In the
swimming pool sector of solar thermal, according to the Florida Solar Energy
Center, the equivalent of 594 MW of power was installed last year in the United
States. For solar hot-water heating for general home use, one utility, Hawaii
Electric, has installed systems that produce approximately 60 MW per year, and
it continues to add around 12 MW of capacity annually.
The “power tower” in California uses
a feld of mirrors focusing on a boiler atop a tower. A working fluid is heated,
which in turn makes steam to drive a turbine. The hot fluid also may be stored
to generate electricity at night. A simple but promising idea is the solar pond,
developed in Israel. If the bottom layer of water is heated by the sun and then
prevented from rising, then heat can reach usable temperatures and be stored in
the pond. Electricity can be generated, or, for that matter, any
low-temperature heat demand can be met.
Although geography, daylight, and
weather present major barriers to the use of solar power, high cost is still
its biggest impediment. Most new technologies need initial research and
development support to get established, which represents a major institutional
hurdle, especially because governments are the most probable source of initial
support. There are likely to be disagreements about which projects should be
funded and over how projects should be developed. In addition, there may be
resistance to new developments from those with vested interests in the existing
range of technologies, and a lack of commitment from decision-makers to press
ahead with what may seem to be risky and long-term development programs.
The growing energy demand is mounting pressure on conventional energy
supplies, such as oil, coal, and natural gas. By 2025, worldwide electricity
use is projected to increase. Solar energy could provide a large percentage of
the future electricity used. Solar energy is expected to form a signifcant
share of the U.S. energy market by 2020, and by 2030 is expected to meet 10
percent of U.S. peak energy demand. For this statement to become a reality,
millions of homeowners and businesses would have to switch to solar energy.
This is possible only if solar power becomes affordable.
It is expected that some of the technologies, such as roof-mounted
systems, solar dishes, and concentrating PVs, will also play a role in
America’s energy future. Experts predict that the main use for solar energy in
the future will be for space heating. Currently, houses are being designed to
make maximum use of solar heat so that the needs for space heating could be met
almost entirely by solar energy in populated regions of the world as far north
as Boston.
Environmental And Economic Impacts
Perhaps the greatest beneft of using solar energy is the environmental
impact. The beauty of solar energy is that it simply uses existing energy. No
hydrocarbons need to be burned in order to release the energy required for
doing other forms of work. Energy from the sun is simply collected and used. In
essence, the sun is doing all of the work that a conventional nuclear reactor
would be doing on Earth. However, the sun takes care of this process without
fuel or maintenance. There are costs and environmental impacts associated with
manufacturing PV cells to harness this energy, though. Initially, these cells
would need to be manufactured in facilities powered by a conventional source of
energy, such as coal or nuclear power.
Although progress is being made in the feld of solar energy, one of the
major concerns holding solar energy back is the high cost. Currently, solar
cells must be viewed as an investment in order to justify the initial cost of
the cells, and the installation. However, the government does offer
incentives at both the state and federal level for those interested in adding
solar cells to homes.
The economic impact of solar energy is huge. Because solar energy is
dispersed more evenly throughout the globe than fossil fuels, no one country or
government would be able to control it. This would ultimately lead to a more
stable infrastructure for countries whose energy needs are dependent on foreign
nations. Solar energy would not only alleviate the pressures of oil dependence,
it would also bring seemingly free energy to developing regions of the world,
where conventional forms of energy are either too expensive or impractical. For
instance, there are regions of the world that do not have any sort of power
grid. For places such as these, the modular design of solar cells allows for
the construction of cells on a case-by-case basis.
Solar energy does have its limits. While the distribution of solar energy
is much more homogeneous than that of fossil fuels, there are portions of the
world that experience more or less solar exposure. For instance, during winter,
the sun does not shine for months at a time at the North pole. For the rest of
the world, there is the dilemma of night. Solar energy alone cannot provide
power 24 hours a day. To overcome this barrier, batteries are required to store
the energy overnight until they can be recharged the next day. Also, because PV
cells are constantly exposed to the elements, they are susceptible to damage
from high winds or hail storms. However, solar energy will continue to gain momentum
as a practical source of energy in the coming decades. As more and more
manufacturing facilities are built to handle the demand, the cost of such cells
will be reduced, and solar energy will become more practical for the average
consumer.
Source: Encyclopedia of Global Warming and Climate Change (Click Here)
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