Technologies, and Impacts
geographical, and political contexts have led to the adoption of different
fuels and related technologies to produce energy. As described in the
history section, we have progressed from using above ground, easily accessible
sources of energy, such as wood and direct solar energy, to fuels such
as coal and oil that require large infrastructures and energy to mine
and process before extracting energy from them. Table 9 at the end of
this section outlines different energy sources and the information relevant
to the environmental impact of these sources.
before, over 95% of the world's energy requirement is currently met by
fossil fuels -- coal, oil, and natural gas. In various technologies, they
release energy by the process of combustion. Major byproducts are carbon
dioxide and various residuals such as fly ash. The environmental problems
relating to fossil fuel use are described in detail in the Atmospheric
System. Environmental pollution, especially air, global climate change,
and resource depletion are the greatest drawbacks of heavy fossil fuel
use. Another problem (particularly for the U.S.) is dependence on foreign
resources. Development of oil in the Atlantic has been a response to the
U.S. need for fuel independence. Alaskan oil exploration involves destruction
of pristine land and unique natural habitats.
while a simple technology, has numerous side effects in addition to carbon
dioxide emission noted above. Coal occurs in combination with sulfur in
many places. High sulfur coal, when burned, produces sulfur dioxide, which
is the source of acid rain. Countries like the U.S. regulate the amount
of sulfur that can be in coal used for power production; therefore high
sulfur coal must be cleaned before it can be burned. Coal burning also
produces large amounts of particulates in the form of fly or bottom ash,
which must be disposed of or recycled.
coal power plants with the encouragement of government and to the liking
of environmental groups, are developing ways to burn coal and reduce the
large amount of coal byproducts. Coal-gasification is one such technology.
Coal is pulverized, mixed with water and then combined with gases such
as nitrogen and oxygen. The gaseous mixture is then heated and a synthetic
gas is produced as the particulates or ash falls to the bottom of the
burner. As the gas cools, sulfur particulates are separated and used to
make sulfuric acid. This is an example of getting more than one product
from a fuel source. The gas is then used to produce steam that spins turbines
and generates electricity.
in the bonds within the nucleus may be released through nuclear fission
or nuclear fusion reactions. The technology used to produce nuclear power
is based on nuclear fission. The fuel for fission reactions are heavy
nuclei, particularly uranium, thorium, and plutonium (a material that
no longer occurs in nature, but of which the U.S. and states of the former
Soviet Union have enormous supplies because of the bomb programs). The
U.S. led the world in nuclear power production, producing about 728 billion
kilowatt-hours. France ranked second, with 375
billion kilowatt-hours, and Japan was third, at about 309 billion kilowatt-hours
produced.1 In 1999, the nuclear share of
total electricity generation for France was 75%, for Japan was 33%, and
for the U.S. was 20%.2 Nuclear energy is
often considered the desirable alternative to coal, because it does not
release carbon dioxide. The materials involved in nuclear power are, however,
heavily radioactive varying from uranium, the starting material, to the
various byproducts during all phases of the energy production cycle, and
the last byproduct, generally termed "radioactive waste." These
byproducts are "radioactive," that is, they emit particles of
radiation and high-energy electromagnetic radiation, such as gamma rays.
This quality makes the materials dangerous. People and other parts of
nature exposed to this radiation can suffer serious long-term damage.
Many of the radioactive materials are also very long-lived, continuing
to emit radiation for hundreds of years or more. Nuclear fission power
technologies have been designed with numerous safeguards and extreme caution
as to be "safe." However, if the global economy were to depend
predominantly on nuclear power, radioactive material transport over air,
land, and water could pose a very large exposure risk. Radioactive waste
disposal is also a challenging problem, as it has to be kept isolated
for thousands to millions of years!
fusion is the reaction responsible for the production of energy in the
sun. Hydrogen is the main fuel for energy source. In fact, the sun is
a huge nuclear fusion reactor. But the extreme high temperature and pressure
needed for fusion to take place has been a formidable obstacle to designing
fusion systems on any usable scale. Nuclear fusion would not produce many
radioactive wastes like fission but will produce radioactive tritium (an
isotope of hydrogen) for which we would have to design safeguards.
wind, direct solar radiation, and geothermal power are all renewable resources.
Of these, hydropower is the best developed. Starting with water wheels
that converted the kinetic energy of running water into various kinds
of motion, to vast projects like the Hoover Dam, the technology for conversion
of hydropower to electricity has long been explored. While it produces
no byproducts, hydroelectric power requires waterfalls or dams with a
large volume of flow. In the case of dams built for hydropower, the devastation
of land and distinctive ecological niches can be large. The conflict between
development of cheap hydroelectricity, preservation of habitat, and economic
interests are encapsulated in the example of the endangerment of salmon
in the Pacific Northwest, due to extensive dam building on the Columbia
River. Hydropower can also come from hot water springs, where the kinetic
energy of water comes from the heat at the Earth's core.
Except for nuclear energy, geothermal energy from the Earth's hot core,
and energy from running water accelerated by the Earth's gravitation naturally
(waterfalls) or artificially (dams), all other energy on the Earth comes
from the sun. The sun's energy also plays a principal role in hydropower
by driving the water cycle. The nature of solar radiation -- electromagnetic
energy from the sun -- is described in detail in the Atmospheric System.
one square meter on the side of the Earth facing the sun receives 1400
W (Joules per second). In a 24-hour period the total amount of energy
reaching the upper atmosphere is 14.4 million calories. One-third of it
is reflected back into space by cloud cover, and the rest, traveling through
the atmosphere, powers the wind and water cycle, and drives the Earth's
climate. The total sunshine entering our atmosphere every year is equivalent
to 500,000 billion barrels of oil or 800,000 billion metric tons of coal!
On a bright sunny day in the northern latitudes, when the sun is at the
highest point, about 1000 Watts/ m2 reaches the ground. On cloudy days,
it can be as low as 200 Watts/m2.
problem with solar energy for high levels of use comes from the fact that
it is so diffuse and spread out, and has to be collected over large areas.
In effect, this is what the foliage of plants does, storing some of the
energy through photosynthesis. It is important to note that only a small
fraction of the solar spectrum -- in the violet and some in the red region
-- is used for photosynthesis. Sunlight has a large quantity of energy
in the green and yellow regions, most of which is reflected by the leaves.
However, it is the capture of energy through photosynthesis, combined
with elements like carbon, oxygen, and hydrogen from the Earth and its
atmosphere, which results in biomass immediately. This biomass eventually
results in a favorite fuel of today (coal) after millions of years of
"processing" by the Earth. Oil and natural gas are similarly
produced from organisms buried for millions of years under rock foundations.
Ancient humans used the gentle, spread out solar energy and biomass for
drying, cooking, and heating. Today's needs demand much larger quantities
concentrated in space and time. This tendency promotes rapid depletion
of the solar "capital" invested into coal formation over millions
One of the
less thoughtful energy uses in our convenience-dominated society is the
use of "high-quality" and concentrated energy even when "low-quality"
spread-out energy would suffice. A good example is our use of fossil fuel
energy driven clothes dryers, even in the summer when clothes could just
dry on a clothesline from direct solar energy. In the ideal use of energy,
we would distinguish between the needs requiring high or low "quality"
energy. Using energy at the appropriate level and from renewable resources
is what is referred to by Amory Lovins as a "soft energy path."
One soft technology philosophy argues that we adapt our life styles to
suit the energy available to us.
is derived from the proceedings of UNERG, the United Nations Conference
on New and Renewable Sources of Energy held in Nairobi, Kenya, in 1981.
The figure shows the different grades of energy derived from direct solar
energy. Passive collectors are static and collect heat energy that falls
on them. Active collection involves mechanisms for storing and/or following
the direction of the sun's rays to receive the maximum energy. Many ancient
civilizations, including the Egyptians, Pueblo and Anastasi Indians, and
Greeks, built their houses to take maximum advantage of the sun's apparent
movement in the sky. However, as more technological energy systems developed,
building with the sun's position in mind became a lost art, especially
in industrialized countries.
21: Solar energy collection options.
refers to collecting the energy through natural or artificial chemicals
-- in the form of biomass (firewood, animal dung, and waste materials)
or in water or chemicals such as certain salts, which hold the heat.
solar radiation into electricity, we use photovoltaic cells. Photovoltaic
cells are based on the phenomenon of photoelectricity -- that light can
release electrons from certain materials. Using these materials, light
can be converted directly into electricity. This phenomenon was discovered
in the late 1800's by George May in Ireland. Rudolf Hertz in Germany produced
the first photoelectric cell soon thereafter using the element selenium
and Albert Einstein explained the physics of photoelectricity in 1905.
However, the first practical solar cells were only developed in the 1950's
by the Bell Telephone Company. The early version of the cell cost thousands
of dollars per watt of electricity yielded. The first large scale testing
occurred in space on the NASA satellite Vanguard in 1958.
efficiency (amount of electrical energy output per input of light energy)
of the largest photoelectric cells is still below 20%. This means we have
to collect sunlight over a large area for any useful application. For
example, if the conversion efficiency is 15%, we need a 6.5 square feet
of photovoltaic material to power a 100-watt light bulb.
have made the largest inroads in space applications. Collection of solar
energy by satellites for Earth's applications have been long considered.
The basic idea is that if the collection were in a geosynchronous orbit
around the Earth (35,890 km or about 22,500 miles above the equator),
we could capture the energy before so much of it was absorbed by clouds
and the atmosphere. Various technical difficulties have essentially halted
this SPS (Solar Power Satellite) project.
If we followed
a philosophy of ecologically friendly design, the best use of solar would
be in the passive or active collection, rather than the conversion to
electricity. However, as a society, we have chosen to use electricity
as the form of energy for almost all applications and a large source of
our environmental problems -- pollution, resource depletion, habitat loss
-- lies in this societal choice.
derived from solar energy moving large masses of air. The two basic phenomena
that are responsible for wind patterns are a large global circulation
and local effects. Cool polar air is drawn towards the tropics to replace
lighter, warmer air that rises and moves towards the poles. This creates
areas of high and low pressure and circulation patterns are set up differently
in the northern and southern hemispheres because of the Earth's rotation.
This sets up the global patterns, such as the trade winds. Locally, the
circulation depends upon whether the air is over land or water. Air over
oceans and large bodies of water is cooler than that over land, and cooler
air is drawn toward the land as the warmed air rises. Together these two
patterns produce movements of enormous complexity.
represents kinetic energy of air arising from the thermal energy of sunlight.
A large part of this energy is lost in various functional forces, and
only a small portion can be captured by windmills. High tech windmill
designs have been developed by various aircraft companies, because of
their expertise in wind dynamics.
the sun it still our most valuable source, powering most of our energy
sources. Our survival may depend upon a wise and judicious use of the
numerous, versatile sources the sun provides.
Cycle of Electricity Generation
Electricity is a form of energy that has become the core of our industrial
societies. The ease with which it can be transported, stored, controlled,
and used has changed the fabric of society. This section looks at the
generation of electricity from various common fuel sources.
energy is the combined potential and kinetic energy of electrons in materials.
Materials that have electrons that are mobile, rather than being confined
to orbits around the atomic nucleus, can conduct electricity. Metals are
prime examples of conductors. A discovery by Michael Faraday of England
in 1831 is the cornerstone of our large-scale electricity generation.
Faraday discovered that when a conductor moves in a magnetic field, an
electric current is produced in the conductor. This Faraday's Law, and
the fact that we can make large magnets is the basis of an electric generator.
If we can use an energy source to move a conducting coil of wire that
is placed in a magnetic field, the current produced in the wire can then
be transported to deliver electric energy. Figures 24.A-D demonstrate
the sequence of electric power production and distribution from four sources:
running water, coal, nuclear fission, and wind.
24.A-D: Electricity Generation Methods
power plant consists essentially of a huge generator -- a gigantic coil
of wire capable of rotating in the space between the poles of an enormous
horseshoe magnet. The motion of the coil is caused by a shaft connecting
it to a turbine, whose rotation spins the coil. In all power plants then,
the energy obtained from the sources has to cause the turbines to turn,
which then rotates the coil. This energy is delivered directly to the
turbines by the falling water in a hydroelectric power plant, and by the
wind in a wind farm. In the case of coal and nuclear fission, the primary
energy is used to transform water into steam or high-pressure water, which
then drives the turbines. Figures 24.A-D illustrate the steps prior to
this, and show the similarity of the final steps of electricity distribution
for all sources.
from the coil is then carried to the final place of use through transmission
and distribution lines. Some of the energy is lost along the wires. To
minimize this loss, the electricity is transmitted at very high voltages
(thousands of volts) along transmission lines and the voltage "stepped
down" near the location of use using transformers. Electricity is
then carried over smaller distribution lines to homes and businesses for
use. The huge steel towers typical of transmission lines are a familiar
sight, as are the distribution lines -- the smaller wires near buildings
attached to "telephone poles." Transformers are the ceramic
structures on local distribution line poles.
of Energy Production and Use
Energy production and use produce some of the most lasting and significant
environmental effects. Some of these are discussed in detail in the Atmospheric
System. Each source of energy brings with it some impacts. Here we summarize
the overall nature of the impacts.
cause some of the largest impacts. In order for a typical 500-Megawatt
plant to produce about 158 Terawatt-hours (tera = 1012) of electricity
per year, it takes 1.5 million tons of coal and 0.15 million tons of limestone.
It produces emissions to the air of 1 million tons of carbon as carbon
dioxide, plus 10000 tons of ash and 193000 tons of scrubber sludge --
both of which contain large quantities of sulfur. (check numbers) Global
climate change, resulting from atmosphere increases in CO2, is described
in detail in the Atmospheric System. Even seemingly slight temperature
changes can cause changes in weather patterns, climate, melting of polar
ice caps, and sea-level rise.
combustion releases pollutants that, under certain conditions, give rise
to photochemical smog and high levels of atmospheric ozone. Impacts from
oil drilling include destruction of ecosystems. The many impacts of extensive
fossil fuel use is discussed in detail in the Atmospheric
mining and processing of the fuels to the production stage, nuclear power
requires the handling of radioactive
material. The potential for accidental release of these materials and
exposure to people, and the problem of long-term disposal of radioactive
wastes, are the main environmental concerns of nuclear power.
power causes disturbances in ecosystems from dams and large land use.
A striking example of the loss of biodiversity is the rapidly declining
populations in the remaining species of salmon in the Pacific Northwest.
(See exercise: Salmon Management in
the Pacific Northwest.)The Three Gorges Dam project currently underway
in China requires the displacement of one million people, in addition
to the devastation of land and ecosystems. But the People's Republic of
China has made rapid industrialization a national priority, and this requires
an enormous development of power production systems.
energy sources, such a wind and solar energy, also have large land use
forces in atomic bonds
38% of world's consumption in 2000
· Easily transported
· Large portion in transportation industry
and consuming produce air, water, and solid waste pollutants
forces in atomic bonds
20% of world's consumption in 2000
· Flexible for use in industries, transportation, power generation
fewer pollutants than oil and coal, and less CO2
forces in atomic bonds
resource for electricity
CO2 and other air, water and solid waste pollutants
Wood and organic waste including societal waste
forces in atomic bonds
· In terms of timber, it is easily harvested and abundant
in certain areas; but it takes a long time to grow a tree.
energy potential relative to other resources
Burning emits CO2 and other pollutants
· Possible toxic byproducts from societal waste
· Loss of habitat when trees harvested, unless sustainable
force of water
· Clean resource with high efficiency
· Influenced by climate and geography
economic cost, though high start up costs
of farmlands, dislocation of people, loss of habitat, alteration of
energy from the sun
· High economic cost particularly in terms of start-up
· Dependent on climate and geographical location
· Need a storage system for the energy to ensure reliability
· Not advanced enough for global use
Technology is already in use for remote applications and non-centralized
uses where it is economically competitive with alternatives
· Unlimited resource that is clean, efficient, safe, and renewable
Power - (solar thermal)
energy from the sun
· Central-thermal systems to convert solar energy directly
· More competitive economically than photovoltaics
· Dependent on climate and geographical location
Solar energy technology not advanced enough for global use
· Many industrial plants use solar
pressure and nuclear reactions in the Earth's core
Extracts heat from underground masses of hot rock.
· Technology is still undeveloped.
· Can be geographically dependent
Consumption is localized
natural geyser activity
& electromagnetic energy from the sun
· Unlimited resource that is a very clean process, no pollutants
Economic cost comparable to current technologies
· System must be designed to operate reliably at variable rotor
· Technology not advanced enough for global societal us
lots of land
· Possible impacts on birds and their migration patterns
· Some noise pollution
nuclear forces in nuclear bonds
Non renewable resource U-235 (uranium)
· Highly technological infrastructure necessary for safe operation
· Production of nuclear energy has a high cost due in part
· High water usage for cooling
accounts for 10-12% of the world's electricity
Byproduct is highly radioactive and highly toxic
· Produces radioactive wastes that have a long lifetime
· Disposal solution complex technically and politically
· Safety issues in terms of operating a facility with the potential
to release radiation to the atmosphere
· Public perception problem in terms of radiation, etc.
Technology is not yet viable and requires research investment
· Technology still not developed enough to make this a viable
high for water pollution because of radioactive tritium
9: Energy Sources and related information.
Energy Information Administration, International Energy Annual 1999, DOE/EIA-0219(99)
(Washington, DC, January 2001.)
Energy Information Administration, International Energy Outlook 2001,
DOE/EIA-0484(2001) (Washington, DC, March 2001.)