2016年12月英语六级阅读理解100篇:可再生能源
Renewable EnergyIn the past century,it has been seen that the consumption of non-renewable
sources of energy has caused more environmental damage than any other human
activity. Electricity generated from fossil fuels such as coal and crude oil has
led to high concentrations of harmful gases in the atmosphere.This has in turn
led to many problems being faced today such as ozone depletion and global
warming. Vehicular pollution has also been a major problem.
Therefore,alternative sources of energy have become very important and
relevant to today's world.These sources,such as the sun and wind,can never be
exhausted and therefore arc called renewable.They cause less emission and are
available locally.Their use can. to a large extent,reduce chemical,radioactive,
and thermalpollution. They stand out as a viable source of clean and limitless
energy.These are also known as non-conventional sources of energy.Most of the
renewable sources of energy are fairfy non-polluting and considered clean though
biomass,a renewable source,is a major polluter indoors.
Solar Energy
Solar energy is the most readily available source of energy.It does not
belong to anybody and is,therefore,free.It is also the most important of the
non-conventional sources of energy because it is non-polluting
and,therefore.helps in lessening the greenhouse effect.
Solar energy has been used since prehistoric times.but in a most primitive
manner.Before 1970,some research and development was carried out in a few
countries to exploit solar energy more efficiently,but most of this work
remained mainly academic.After the dramatic rise in oil prices in the
1970s,several countries began to formulate extensive research and development
programmes to exploit solar energy.
When we hang out our clothes to dry in the sun,we use the energy of the
sun.In the same way, solar panels absorb the energy of the sun to provide heat
for cooking and for heating water.Such systems are available in the market and
are being used in homes and factories.
Solar energy can also be ursed to meet our electricity requirements.Through
Solar Photovoltaic(SPV)cells,solar radiation gets converted into DC electricity
directly.This electricity can either be used as it is orcan be stored in the
battery.This stored electrical energy then can be used ac night.
Hydro Power
Hydro power is one of the best,cheapest,and cleanest source of
energy,although,with big dams,there are many environmental and social
problems.Small dams are,however,free from these problems.This is in fact one
ofthe earliest known renewable energy sources.in the country(since the beginning
of the 20th century).
In fact,for the last few hundred years,people living in the hills of the
Himalayas have been using water mills.or chakki,to grind wheat.Besides being
free from the problem of pollution.small hydropower plants arealso free from
issues and controversies that are associated with the bigger projects.namely
affecting the lives of thousands of people living along the banks of the
rivers.destruction of large areas under forest.and seismological threats.
New environmental laws affected by the danger of global warming have made
energy from small hydropower plants more relevant.These small hydropower piants
can serve the energy needs of remote rural areas independently.The real
challenge in a remote area lies in successful marketing of the energy and
recovering the dues.Local industries should be encouraged to use this
electricity for sustainable development.
It is a technology with enormous potential.which could exploit the water
resources to supply energy to remote rural areas with little access to
conventional energy sources.It also eliminates most of the negative
environmental effects associated with large hydro projects.
Energy From the Sea-Ocean Thermal,Tidal and Wave Energy
On an averaige,the 60 million square kilometre of the tropical seas absorb
solar radiation equivalent to the heat content of 245 billion barrels of
oil.Scientists feel that if this energy can be tapped a large source of energy
will be available to the tropical countries and to other countries as well.The
process of harnessing this energy is called OTEC(ocean thermal energy
conversion).It uses the temperature differences between the surface of the ocean
and the depths of about lOOOm to operate a heat engine.which produces electric
power.
Energy is also obtained from wavcs and tides.In some countries such as
Japan small scale power generators run by energy from waves of the ocean,have
been used as power sources for channcl marking buoys.
Biomass
Biomass is a renewable energy resource derived from the carbonaceous waste
of various human and natural activities.It is derived from numerous
sources,including the by-products from the timber industry.agricultural
crops,raw material from the forest,major parts of household waste and wood.
Biomass does not add carbon dioxide to the atmosphere as it absorbs the
same amount of carbon in growing as it releases when consumed as a fuel. Its
advantage is that it can be used to generate electricity with the same equipment
of power plants that are now burning fossil fuels.Biomass is an important source
of energy and the most important fuel worldwide after coal,oil and natural
gas.
Traditional use of biomass is more than its use in modern application.In
the developed world biomass is again becoming important for applications such as
combined heat and power generation.In addition,biomass energy is gaining
significance as a source of clean heat for domestic heating and community
heating applications.In fact in countries like Finland.USA and Sweden the per
capita biomass energy used is higher than it is in India.China or in Asia.
Geothermal Energy
We live between two great sources of energy,the hot rocks beneath the
surface of the earth and the sun in the sky.Our ancestors knew che value of
geothermal energy;they bathed and cooked in hot springs.Today we have recognized
that this resource has potential for much broader application.
The core of the earth is very hot and it is possible to make use of this
geothermal energy(in Greek it means heat from the earth).These are areas where
there are volcanoes.hot springs,and geysers,and methane under the water in the
oceans and seas. n some countries,such as in the USA water is pumped from
underground hot water deposits and used to heat people's houses.
The utilization of geothermal energy for the production of electricity
dates back to the early part of thetwentieth century.For 50 years the generation
of electricity from geothermal energy was confined to Italy and interest in this
technology was slow co spread elsewhere.In 1943 the use of geothermal hot water
was pioneered in lceland.
Co-generation
Co-generation is the concept or producing two forms of energy from one
fuel.One of the forms of energy must always be heat and the other may be
electricity or mechanical energy.In a conventional power plant,fuel is burnt in
a boiler to generate high-pressure steam.This steam is used to drive a
turbine.which in turn drives an alternator through a steam turbine to produce
electric power.The exhaust steam is generally condensed to water which goes back
to the boiler.
As the low-pressure steam has a large quantum of heat which is lost in the
process of condensing,the efficiency of conventional power plants is only around
35%.In a cogeneration plant,very high efficiency levels,in the range of
75%-90%,can be reached.This is so,because the low-pressure exhaust steam coming
out of th turbine is not condensed,but used for heating purposes in factories or
houses.
Since co-generation can meet both power and heat needs, it has otber
advantages as well in the form of significant cost savings for the plant and
reduction in emissions of pollutants due to reduced fuel consumption.
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