Electric Charge

Electric Charge

 

The simplest electrical phenomenon is static electricity, the temporary “charging”
of certain objects when they are rubbed against each other. Run a comb
through your hair when it’s dry, and the hair and comb begin to attract each other,
indicating that they are charged. Other familiar examples include clothes sticking
together in the dryer, and the sudden shock that you sometimes get when shaking
someone’s hand after walking across a carpet with rubber-soled shoes.
What you may not have noticed is that static electricity can result in both
attractive and repulsive forces. The comb attracts the hair and vice-versa, but the
hairs repel each other, and two combs similarly charged will likewise repel each
other. To explain this we say that there are two types of electric charge, called
positive and negative. When objects become charged by rubbing against each other,
one always becomes positive and the other becomes negative. Positively charged
objects (the hair, for instance) attract negatively charged objects (the comb) and
vice-versa, but two positives repel each other, as do two negatives. In summary,
like charges repel, while unlike charges attract.
What’s happening at the atomic level is this: All atoms contain particles called
protons and electrons, which carry intrinsic positive and negative charges, respectively.
Ordinarily, the number of protons in a chunk of matter is almost exactly
equal to the number of electrons, so their static-electricity effects cancel out on large
scales. However, rubbing certain objects together transfers some of the electrons
from one to the other, leaving the first object positively charged (because it now
has has an excess of protons) and the other object negatively charged (because it
now has an excess of electrons).
In the official scientific system of units, the amount of electric charge on an object
is measured in units called coulombs (abbreviated C). The total charge on all theprotons in a gram of matter is typically about 50,000 C, while the electrons in the
same gram of matter would carry a total charge of −50, 000 C. These numbers may
seem inconveniently large, but they’re not very relevant to everyday life because
all we normally measure is the excess of one type of charge over the other. The
amount of excess charge that readily builds up on a person’s hair is less than a
microcoulomb, that is, 0.000001 C. (“Micro” is the metric prefix for a millionth,
0.000001.) The charge of a single proton turns out to be 1.6 × 10−19 C, while the
charge of a single electron is minus the same amount. Thus, the number of excess
electrons on a charged comb is quite enormous, but only a tiny, tiny fraction of all
the electrons in the comb.
How long an object remains electrically charged depends on how easily the excess
electrons can find their way back to the excess protons. Some materials, such as
metals, allow electrons to move through them quite readily, while other materials,
such as paper, plastic, and dry air, offer quite a bit of resistance to the motion
of electrons. Materials in the first class are called conductors, while materials in
the second class are called insulators. The distinction between conductors and
insulators is merely a matter of degree, however; all materials conduct to some extent.
Furthermore, any insulating material will become a good conductor if it is
subjected to electrostatic forces that are strong enough to rip electrons out of the
atoms. The most dramatic example is lightning: the sudden discharge of thunderclouds
through a column of air, which is momentarily made into a conductor by the
enormous static charges. The shock that you get when you shake someone’s hand
is the same phenomenon, on a much smaller scale.

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System Cost and Performance

System Cost and Performance

1. Recent progress in Renewable Energy System Cost and Performance

As previously described there has been significant progress in cost reduction made by wind and
PV systems, while biomass, geothermal, and solar thermal technologies are also experiencing
cost reductions, and these are forecast to continue. Figure 8 presents forecasts made by the U.S.
DOE for the capital costs of these technologies, from 1997 to 2030.

2. Lessons Learned in Developing Countries

In developing nations, renewable energy technologies are increasingly used to address energy
shortages and to expand the range of services in both rural and urban areas. In Kenya over
80,000 small (20 - 100 Wp) solar PV systems have been commercially financed and installed in
homes, battery charging stations, and other small enterprises. Meanwhile, a government program
in Mexico has disseminated over 40,000 such systems. In the Inner Mongolian autonomous
region of China over 130,000 portable windmills provide electricity to about one-third of the
non-grid-connected households in this region.
These case studies demonstrate that the combination of sound national and international policies
and genuinely competitive markets – the so-called ‘level playing field’ -- can be used to generate
sustainable markets for clean energy systems. They also demonstrate that renewable energy
systems can penetrate markets in the developing world, even where resources are scarce, and that
growth in the renewables sector need not be limited to applications in the developed world. Just
as some developing countries are bypassing construction of telephone wires by leaping directly
to cellular-based systems, so too might they avoid building large, centralized power plants and
instead develop decentralized systems. In addition, to help mitigating the environmental costs of
electrification, this strategy can also reduce the need for the construction of large power grids.
Despite their limited recent success, renewable energy sources have historically had a difficult
time breaking into markets that have been dominated by traditional, large-scale, fossil fuel-based
systems. This is partly because renewable and other new energy technologies are only now being
mass produced, and have previously had high capital costs relative to more conventional
systems, but also because coal, oil, and gas-powered systems have benefited from a range of
subtle subsidies over the years. These include military expenditures to protect oil exploration and
production interests overseas, the costs of railway construction that have enabled economical
delivery of coal to power plants, and a wide range of smaller subsidies.
However, another limitation has been the intermittent nature of some renewable energy sources,
such as wind and solar. One solution to this last problem is to develop diversified systems that
maximize the contribution of renewable energy sources but that also uses clean natural gas
and/or biomass-based power generation to provide base-load power when the sun is not shining
and the wind is not blowing. Using a range of different renewable energy technologies to provide
energy for a region can also help to mitigate the intermittent nature that some of them exhibit.
Even when there is no wind blowing there may be strong solar insolation, and vice versa.
In essence, however, renewable energy technologies face a similar situation confronting any new
technology that attempts to dislodge an entrenched technology. For many years, we have been
“locked-in” to a suite of fossil fuel and nuclear-based technologies, and many of our secondary
systems and networks have been designed and constructed to accommodate these. Just as
electric-drive vehicles face an uphill battle to dislodge gasoline-fueled, internal combustion
engine vehicles, so too do solar, wind, and biomass technologies face a difficult time upstaging
modern coal, oil, and natural gas power plants. This “technological lock-in” situation has several
important implications. First, various types of feedstock and fuel delivery infrastructure have
been developed over the years to support conventional energy sources, and in some cases these
would require modifications to support renewable energy technologies. This would entail
additional cost, tipping the table away from the new challengers. Second, the characteristics of
conventional energy systems have come to define how we believe these systems should perform,
and new renewable energy technologies that offer performance differences compared to
conventional technologies (such as intermittent operation) may raise doubts among potential
system purchasers. Third, to the extent that new technologies are adopted, early adoptions will
lead to improvements and cost reductions in the technologies that will benefit later users, but
there is no market mechanism for early adopters to be compensated for their experimentation that
later provides benefits to others. Since there is no compensatory mechanism, few are likely to be
willing to gamble on producing and purchasing new technologies, and the market is likely to
under-supply experimentation as a result.
Hence, particularly in the absence of policy intervention (discussed below), we may remain
locked-in to existing technologies, even if the benefits of technology switching overwhelm the
costs. There are numerous examples, however, of an entrenched or locked-in technology being
first challenged and ultimately replaced by a competing technology. This process is generally
enabled by a new wave of technology, and it is sometimes achieved through a process of
hybridization of the old and the new. Technological "leapfrogging" is another possibility, but this
seems to occur relatively rarely. A prime example of the hybridization concept is in the case of
the competition between gas and steam powered generators, which dates back to the beginning
of the century. From about 1910 to 1980, the success of steam turbines led to a case of
technological lock-in, and to the virtual abandonment of gas turbine research and development.
However, partly with the aid of "spillover" effects from the use of gas turbines in aviation, the
gas turbine was able to escape the lock-in to steam turbine technology. First, gas turbines were
used as auxiliary devices to improve steam turbine performance, and then they slowly became
the main component of a hybridized, "combined-cycle" system. In recent years, orders for
thermal power stations based primarily on gas turbines have increased to more than 50 percent of
the world market, up from just 15-18 percent in 1985.
Furthermore, increasing returns to adoption, or "positive feedbacks," can be critical to
determining the outcomes of technological competitions in situations where increasing returns
occur. These increasing returns can take various forms, including the following: industrial
learning (e.g., learning-by-doing in manufacturing, along with economies of scale, leads to
production cost declines); network related externalities (e.g., networks of complementary
products, once developed, encourage future users); returns on information (e.g. information
about product quality and reliability decreases uncertainty and reduces risk to future adopters);
and/or better compatibility with other technologically interdependent systems. Where increasing
returns are important, as in most technology markets, the success with which a challenger
technology can capture these effects and enter the virtuous cycle of positive feedbacks may, in
conjunction with chance historical events, determine whether or not the technology is ultimately
successful.
Thus, just as the hybridization between gas and steam turbines gave gas turbines a new foothold
in the market, so might hybridization between gas and biomass-fueled power plants allow
biomass to eventually become a more prominent energy source. Hybridization of intermittent
solar and wind power with other clean “baseload” systems could help to allow solar and wind
technologies to proliferate, and perhaps with advances in energy storage systems they could
ultimately become dominant. Once they are able to enter the market, through whatever means,
these technologies can reap the benefits of the virtuous cycle brought on by increasing returns to
adoption, and clearly this is already beginning to happen with several new types of renewable
energy technologies.

3. Leveling the Playing Field

As shown in Figure 7.3, above, renewable energy technologies tend to be characterized by
relatively low environmental costs. In an ideal world, this would aid them in competing with
conventional technologies, but of course many of these environmental costs are “externalities”
that are not priced in the market. Only in certain areas and for certain pollutants do these
environmental costs enter the picture, and clearly further internalizing these costs would benefit
the spread of renewables. The international effort to limit the growth of greenhouse emissions
through the Kyoto Protocol may lead to some form of carbon-based tax, and this could prove to
be an enormous boon to renewable energy industries. However, support for the Kyoto Protocol
among industrialized countries remains relatively weak, particularly in the U.S., and any
proposed carbon-based taxation scheme will surely face stiff opposition.
Perhaps more likely, concern about particulate matter emission and formation from fossil-fuel
power plants will lead to expensive mitigation efforts, and this would help to tip the balance
toward cleaner renewable systems. In a relatively controversial move, the U.S. Environmental
Protection Agency (EPA) has recently proposed new ozone and particulate matter (PM)
standards that are even more stringent than the current standards that remain unattained in some
U.S. urban areas. The EPA has justified these new regulations with analysis that shows that new
standards are necessary to provide increased protection against a wide range of potential health
impacts. For example, the EPA estimates that even if Los Angeles County were to meet the
existing PM standards, 400 to 1,000 deaths per year would still occur as a result of exposure to
very fine PM (under 2.5 microns in diameter) that presently is not regulated. The combination of
increased pressure to attain ozone and PM standards will further complicate siting of new fossilfueled
power plants in some areas of the U.S., particularly where they are now required to find
“offsets” for their pollution impacts. This will indirectly but surely benefit renewable energy
technologies, which do not typically face these difficulties in obtaining siting permits.

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Hydropower

Hydropower

1. Introduction

Hydropower is the largest renewable resource used for electricity. It plays an essential role in

many regions of the world with more than 150 countries generating hydroelectric power. Asurvey in 1997 by The International Journal on Hydropower & Dams found that hydro supplies
at least 50 percent of national electricity production in 63 countries and at least 90 percent in 23
countries. About 10 countries obtain essentially all their commercial electricity from hydro,
including Norway, several African nations, Bhutan and Paraguay.
There is about 700 GW of hydro capacity in operation worldwide, generating 2600 TWh/year
(about 19 percent of the world’s electricity production). About half of this capacity and
generation is in Europe and North America with Europe the largest at 32 percent of total hydro
use and North America at 23 percent of the total. However, this proportion is declining as Asia
and Latin America commission large amounts of new hydro capacity.
Small, mini and micro hydro plants (usually defined as plants less than 10 MW, 2 MW and
100kW, respectively) also play a key role in many countries for rural electrification. An
estimated 300 million people in China, for example, depend on small hydro.

2. Capacity and Potential

There is vast unexploited potential worldwide for new hydro plants, particularly in the
developing countries of Asia, Latin America and Africa while most of the best sites have already
been developed in Europe and North America. There is also upgrading potential at existing
schemes though any future hydro projects will, in general, have to satisfy stricter requirements
both environmentally and economically than they have in the past.
As shown in Table 4 the world’s gross theoretical hydropower potential is about 40000
TWh/year, of which about 14000 TWh/year is technically feasible for development and about
7000 TWh/year is currently economically feasible. The last figure fluctuates most being
influenced not only by hydro technology, but also by the changing competitiveness of other
energy/electricity options, the status of various laws, costs of imported energy/electricity, etc.

Until recent years there has been less than 100 GW (about 350 TWh/year) of new hydro capacity
under construction at any one time, equivalent to less than 15 percent of the capacity in
operation. The figure has now risen, reflecting China’s vast construction program, which
includes the 18.2 GW Three Gorges Project, now in its second phase of construction. Most new
hydro capacity is under construction in Asia and South America. China has by far the most, with
about 50 GW under way. Brazil has largest resources in world (800,000 GWh/year) of
economically exploitable capacity and Norway depends almost entirely hydro for its electricity
needs.
Hydropower continues to be the most efficient way to generate electricity. Modern hydro
turbines can convert as much as 90 percent of the available energy into electricity. The best fossil
fuel plants are only about 50 percent efficient. In the U.S., hydropower is produced for anaverage of 0.7 cents/kWh. This is about one-third the cost of using fossil fuel or nuclear and onesixth
the cost of using natural gas. Hydro resources are also widely distributed compared with
fossil and nuclear fuels and can help provide energy independence for countries without fossil
fuel resources.
There is also significant, widespread activity in developing small, mini and micro hydro plants.
At least forty countries, particularly in Asia and Europe, have plants under construction and even
more have plants planned. China, Brazil, Canada, Turkey, Italy, Japan and Spain all have plans
for more than 100 MW of new capacity.

3. Small Hydro

Small-scale hydro is mainly ‘run of river,’ so does not involve the construction of large dams and
reservoirs. It also has the capacity to make a more immediate impact on the replacement of fossil
fuels since, unlike other sources of renewable energy, it can generally produce some electricity
on demand (at least at times of the year when an adequate flow of water is available) with no
need for storage or backup systems. It is also in many cases cost competitive with fossil-fuel
power stations, or for remote rural areas, diesel generated power.
Small hydro has a large, and as yet untapped, potential in many parts of the world. It depends
largely on already proven and developed technology with scope for further development and
optimization. Least-cost hydro is generally high-head hydro since the higher the head, the less
the flow of water required for a given power level, and so smaller and less costly equipment is
needed. While this makes mountainous regions very attractive sites they also tend to be in areas
of low population density and thus low electricity demand and long transmission distances often
nullify the low cost advantage. Low-head hydro on the other hand is relatively common, and also
tends to be found in or near concentrations of population where there is a demand for electricity.
Unfortunately, the economics also tend to be less attractive unless there are policy incentives in
place to encourage their development.

4. Environmental and Social Impacts

Although hydroelectricity is generally considered a clean energy source, it is not totally devoid
of greenhouse gas emissions (GHG) and it can often have significant adverse socio-economic
impacts. There are arguments now that large-scale dams actually do not reduce overall GHG
emissions when compared to fossil fuel power plant. To build a dam significant amounts of land
need to be flooded often in densely inhabited rural area, involving large displacements of usually
poor, indigenous peoples. Mitigating such social impacts represents a significant cost to the
project, which if it is even taken into consideration, often not done in the past, can make the
project economically and socially unviable.
Environmental concerns are also quite significant, as past experience has shown. This includes
reduction in biodiversity and fish populations, sedimentation that can greatly reduce dam
efficiency and destroy the river habitat, poor water quality, and the spread of water-related
diseases. In fact, in the U.S. several large power production dams are being decommissioned due
to their negative environmental impacts. Properly addressing these issues would result in an
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enormous escalation of the overall costs for producing hydropower making it far less competitive
then is usually stated. As many countries move toward an open electricity market this fact will
come into play when decisions regarding investments in new energy sources are being made. If
the large hydro industry is to survive it needs to come to grips with its poor record of both cost
estimation and project implementation.

5. Conclusions

Hydropower is a significant source of electricity worldwide and will likely continue to grow
especially in the developing countries. While large dams have become much riskier investment
there still remains much unexploited potential for small hydro projects around the world. It is
expected that growth of hydroelectricity will continue but at a slower rate than that of the 70’s
and 80’s. Thus, the fraction of hydroelectricity in the portfolio of primary sources of energy,
which is today at 19 percent, is expected to decrease in the future. Improvements and efficiency
measures are needed in dam structures, turbines, generators, substations, transmission lines, and
environmental mitigation technology if hydropower’s role as a clean renewable energy source is
to continue to be supported.

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Solar Photovoltaic and Solar Thermal Technologies

Solar Photovoltaic and Solar Thermal Technologies

There are two basic categories of technologies that convert sunlight into useful forms of energy,
aside from biomass-based systems that do this in a broader sense by using photosynthesis from
plants as an intermediate step. First, solar photovoltaic (PV) modules convert sunlight directly
into electricity. Second, solar thermal power systems use focused solar radiation to produce
steam, which is then used to turn a turbine producing electricity. The following provides a brief
overview of these technologies, along with their current commercial status.

1. Solar Photovoltaics

Solar PV modules are solid-state semiconductor devices with no moving parts that convert
sunlight into direct-current electricity. The basic principle underlying the operation of PV
modules dates back more than 150 years, but significant development really began following
Bell Labs’ invention of the silicon solar cell in 1954. The first major application of PV
technology was to power satellites in the late 1950s, and this was an application where simplicity
and reliability were paramount and cost was a secondary concern. Since that time, enormous
progress has been made in PV performance and cost reduction, driven at first by the U.S. space

program’s needs and more recently through private/public sector collaborative efforts in the
U.S., Europe, and Japan.
At present, annual global PV module production is over 150 MW, which translates into a more
than $1 billion/year business. In addition to the ongoing use of PV technologies in space, their
present-day cost and performance also make them suitable for many grid-isolated and even gridconnected
applications in both developed and developing parts of the world. PV technologies
are potentially so useful that as their comparatively high initial cost is brought down another
order of magnitude, it is very easy to imagine them becoming nearly ubiquitous late in the 21st
century. PV systems would then likely be employed on many scales in vastly differing
environments, from microscopic cells to 100 MW or larger ‘central station’ generating plants
covering square kilometers on the earth’s surface and in space. The technical and economic
driving forces that favor the use of PV technologies in these widely diverse applications will be
equally diverse. However, common among them will be the durability, high efficiency, quiet
operation, and lack of moving parts that PV systems offer, and the fact that these attributes
combine to provide a power source with minimum maintenance and unmatched reliability.
PV system cost and performance have been steadily improving in recent years. PV
manufacturing costs have fallen from about $30 per watt in 1976 to well under $10 per watt by
the mid-1990s as can be seen in Figure 5. Installed PV system costs today are about $8.00 to
$12.00 per watt, depending on the level of solar insolation at the site and other factors. These
installed system costs are expected by some analysts to reach a range of from $3.00 to $6.00 per
watt by 2010, and if this is achieved PV systems could achieve a sales level of over 1,600 MW
per year by that time.

2. Solar Thermal Systems

Solar thermal power systems use various techniques to focus sunlight to heat an intermediary
fluid, known as heat transfer fluid that then is used to generate steam. The steam is then used in a
conventional steam turbine to generate electricity. At present, there are three solar thermal power
systems currently being developed: parabolic troughs, power towers, and dish/engine systems.
Because these technologies involve a thermal intermediary, they can be readily hybridized with
fossil fuels and in some cases adapted to utilize thermal storage. The primary advantage of
hybridization and thermal storage is that the technologies can provide dispatchable power and
operate during periods when solar energy is not available. Hybridization and thermal storage can
enhance the economic value of the electricity produced, and reduce its average cost.

Parabolic trough solar thermal systems are commercially available. These systems use parabolic
trough-shaped mirrors to focus sunlight on thermally efficient receiver tubes that contain a heat
transfer fluid. This fluid is heated to about 390° C. (734° F) and pumped through a series of heat
exchangers to produce superheated steam that powers a conventional turbine generator to
produce electricity. Nine of these parabolic trough systems, built in 1980s, are currently
generating 354 MW in Southern California. These systems, sized between 14 and 80 MW, are
hybridized with up to 25 percent natural gas in order to provide dispatchable power when solar
energy is not available.
Power tower solar thermal systems are in the demonstration and scale-up phase. They use a
circular array of heliostats (large individually-tracking mirrors) to focus sunlight onto a central
receiver mounted on top of a tower. The first power tower, Solar One, was built in Southern
California and operated in the mid-1980s. This initial plant used a water/steam system to
generate 10 MW of power. In 1992, a consortium of U.S. utilities joined together to retrofit Solar
One to demonstrate a molten-salt receiver and thermal storage system. The addition of this
thermal storage capability makes power towers unique among solar technologies by allowing
dispatchable power to be provided at load factors of up to 65 percent. In this system, molten-salt
is pumped from a “cold” tank at 288° C. (550° F) and then cycled through the receiver where it
is heated to 565° C. (1,049° F) and finally returned to a “hot” tank. The hot salt can then be used
to generate electricity when needed. Current designs allow storage ranging from 3 to 13 hours.
Dish/engine solar thermal systems, currently in the prototype phase, use an array of parabolic
dish-shaped mirrors to focus solar energy onto a receiver located at the focal point of the dish.
Fluid in the receiver is heated to 750° C (1,382° F) and used to generate electricity in a small
engine attached to the receiver. Engines currently under consideration include Stirling and
Brayton-cycle engines. Several prototype dish/engine systems, ranging in size from 7 to 25 kW,
have been deployed in various locations in the U.S. and elsewhere. High optical efficiency and
low startup losses make dish/engine systems the most efficient of all solar technologies, with
electrical conversion efficiencies of up to 29.4 percent. In addition, the modular design of
dish/engine systems make them a good match for both remote power needs, in the kilowatt
range, as well as grid-connected utility applications in the megawatt range.
System capital costs for these systems are presently about $4-5 per watt for parabolic trough and
power tower systems, and about $12-13 per watt for dish/engine systems. However, future cost
projections for trough technology are higher than those for power towers and dish/engine
systems due in large part to their lower solar concentration and hence lower operating
temperature and efficiency. By 2030, the U.S. Department of Energy forecasts costs of $2.70 per
watt, $2.50 per watt, and $1.30 per watt, respectively, for parabolic trough, power tower, and
dish engine systems.

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Wind Energy

 Wind Energy

 

1. Introduction

Wind has considerable potential as a global clean energy source, being both widely available,
though diffuse, and producing no pollution during power generation. Wind energy has been one
of humanity’s primary energy sources for transporting goods, milling grain, and pumping water
for several millennia. From windmills used in China, India and Persia over 2000 years ago to the
generation of electricity in the early 20th century in Europe and North America wind energy has
played an important part in our recorded history. As industrialization took place in Europe and
then in America, wind power generation declined, first gradually as the use of petroleum and
coal, both cheaper and more reliable energy sources, became widespread, and then more sharply
as power transmission lines were extended into most rural areas of industrialized countries. The
oil crises of the 70’s, however, triggered renewed interest in wind energy technology for gridconnected
electricity production, water pumping, and power supply in remote areas, promoting
the industry’s rebirth.

This impetus prompted countries; notably Denmark and the United States, to establish
government research and development (R&D) programs to improve wind turbine technology. In
conjunction with private industry research this lead to a reemergence in the 1980’s of wind
energy in the United States and Europe, when the first modern grid-connected wind turbines
were installed. In the 1990’s this development accelerated, with wind becoming the fastest
growing energy technology in the world developing into a commercially competitive global
power generation industry. While in 1990 only about 2000 MW of grid-connected wind power
was in operation worldwide by 1999 this figure had surpassed 10,000 MW, not including the
over one million water-pumping wind turbines located in remote areas.
Since 1990 the average annual growth rate in world wind generating capacity has been 24
percent, with rates of over 30 percent in the last two years. Today there is more than 13,000 MW
of installed wind power, double the capacity that was in place just three years earlier (Figure 3).
This dramatic growth rate in wind power has created one of the most rapidly expanding
industries in the world, with sales of roughly $2 billion in 1998, and predictions of tenfold
growth over the next decade. Most 2000 forecasts for installed capacity are being quickly
eclipsed with wind power having already passed the 10,000 MW mark in early 1999.

2. Economics of Wind Energy

Larger turbines, more efficient manufacturing, and careful siting of wind machines have brought
wind power costs down precipitously from $2600 per kilowatt in 1981 to $800 per kilowatt in
1998. New wind farms in some areas have now reached economic parity with new coal-based
power plants. And as the technology continues to improve, further cost declines are projected,

which could make wind power the most economical source of electricity in some countries.
Market growth, particularly in Europe, has been stimulated by a combination of favorable
governmental policies, lower costs, improved technology (compared to wind turbines built in
1981, modern turbines generate 56 times the energy at only 9 times the cost), and concern over
environmental impacts of energy use.
Wind energy is currently one of the most cost-competitive renewable energy technologies.
Worldwide, the cost of generating electricity from wind has fallen by more than 80 percent, from
about 38 US cents in the early1980s to a current range of 3-6 UScents/kWh levelized over a
plant's lifetime, and analysts forecast that costs will drop an additional 20-30 percent in the next
five years. Consequently, in the not-too-distant future, analysts believe, wind energy costs could
fall lower than most conventional fossil fuel generators, reaching a cost of 2.5 UScents/kWh

Wind technology does not have fuel requirements as do coal, gas, and petroleum generating
technologies. However, both the equipment costs and the costs of accommodating special
characteristics such as intermittence, resource variability, competing demands for land use, and
transmission and distribution availability can add substantially to the costs of generating
electricity from wind. For wind resources to be useful for electricity generation, the site must (1)
have sufficiently powerful winds, (2) be located near existing transmission networks, and (3) beeconomically competitive with respect to alternative energy sources. While the technical
potential of wind energy to fulfill our need for energy services is substantial the economic
potential of wind energy remains dependent on the cost of wind turbine systems as well as the
economics of alternative options.

3.Conclusions

For the first time, we are seeing one of the emerging renewable energy generating options—wind
power—in a position to compete with the generation technologies of the last century. A variety
of players are engaged in pushing forward wind projects worldwide. Enron Wind Corporation
acquired German turbine manufacturer Tacke; NEG Micon of Denmark has built manufacturing
facilities in the U.S., Vestas of Denmark has built factories in Spain and India and many
manufacturers have developed joint ventures in various countries around the world. This
globalization trend is likely to continue as financial institutions are beginning to view the wind
industry as a promising investment opportunity. As more countries are added to the wind energy
34
roster, uneven development focusing on a half-dozen key markets will most likely be replaced by
more balanced growth. During the next couple of years, large-scale projects are expected to be
developed in Egypt, Nicaragua, Costa Rica, Brazil, Turkey, Philippines, and several other
countries, totaling thousands of MW of new installed capacity, and expanding the number of
countries using their wind resources.
Yet, as land constraints, lower average wind speeds in future projects, as well as possibly lower
energy prices impact the economics of future projects wind penetration will likely begin to
saturate and the growth rates quoted above slow. This trend may be offset, however, by the use
of larger, more efficient turbines, where the average size per turbine installed has already
increased from 630 kW in 1997 to megawatt size systems in 1999, allowing operators to lower
generation costs. The increase in capacity factor (annual energy output/output based on full time
operation at rated power) from 20 percent to 25 percent also reflects improved efficiency and
siting of projects. In addition, the future development of offshore wind farms will open up new
frontiers in wind energy development.
The issue of wind power opportunity is likely to become increasingly relevant in determining its
future use in world electricity supply. Understanding wind prospects is important in expected
“normal” energy futures as well as for possible exceptional ones. As wind turbine costs decline
and their performance improves, the extent to which wind resources, transmission and
distribution networks, and market forces complement or offset these improvements becomes all
the more pertinent for near and mid-term electricity supply. If these additional factors have little
influence, then improved wind technologies may enjoy fairly rapid penetration into electricity
markets. To the extent that economically accessible wind resources are soon exhausted, networks
are full, or markets are resistant, however, wind power may find itself still a marginal source of
electric power supply.

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Principles of renewable energy

Principles of renewable energy

1.1 Introduction

The aim of this text is to analyse the full range of renewable energy supplies
available for modern economies. Such renewables are recognised as
vital inputs for sustainability and so encouraging their growth is significant.
Subjects will include power from wind, water, biomass, sunshine and
other such continuing sources, including wastes. Although the scale of local
application ranges from tens to many millions of watts, and the totality is
a global resource, four questions are asked for practical application:

1 How much energy is available in the immediate environment – what is

the resource?

2 For what purposes can this energy be used – what is the end-use?

3 What is the environmental impact of the technology – is it sustainable?

4 What is the cost of the energy – is it cost-effective?

The first two are technical questions considered in the central chapters by
the type of renewables technology. The third question relates to broad issues
of planning, social responsibility and sustainable development; these are
considered in this chapter and in Chapter 17. The environmental impacts
of specific renewable energy technologies are summarised in the last section
of each technology chapter. The fourth question, considered with other
institutional factors in the last chapter, may dominate for consumers and
usually becomes the major criterion for commercial installations. However,
cost-effectiveness depends significantly on:
a Appreciating the distinctive scientific principles of renewable energy.
b Making each stage of the energy supply process efficient in terms of
both minimising losses and maximising economic, social and environmental
benefits.
c Like-for-like comparisons, including externalities, with fossil fuel and
nuclear power.
When these conditions have been met, it is possible to calculate the costs
and benefits of a particular scheme and compare these with alternatives for
an economic and environmental assessment.
Failure to understand the distinctive scientific principles for harnessing
renewable energy will almost certainly lead to poor engineering and uneconomic
operation. Frequently there will be a marked contrast between the
methods developed for renewable supplies and those used for the nonrenewable
fossil fuel and nuclear supplies.

 Wind energy conversion system

1.2 Energy and sustainable development

Sustainable development can be broadly defined as living, producing and
consuming in a manner that meets the needs of the present without compromising
the ability of future generations to meet their own needs. It has
become a key guiding principle for policy in the 21st century. Worldwide,
politicians, industrialists, environmentalists, economists and theologians
affirm that the principle must be applied at international, national and local
level. Actually applying it in practice and in detail is of course much harder!
In the international context, the word ‘development’ refers to improvement
in quality of life, and, especially, standard of living in the less developed
countries of the world. The aim of sustainable development is for the
improvement to be achieved whilst maintaining the ecological processes on
which life depends. At a local level, progressive businesses aim to report a
positive triple bottom line, i.e. a positive contribution to the economic, social
and environmental well-being of the community in which they operate.
The concept of sustainable development became widely accepted following
the seminal report of the World Commission on Environment and
Development (1987). The commission was set up by the United Nations
because the scale and unevenness of economic development and population
growth were, and still are, placing unprecedented pressures on our planet’s
lands, waters and other natural resources. Some of these pressures are severe
enough to threaten the very survival of some regional populations and, in
the longer term, to lead to global catastrophes. Changes in lifestyle, especially
regarding production and consumption, will eventually be forced on
populations by ecological and economic pressures. Nevertheless, the economic
and social pain of such changes can be eased by foresight, planning
and political (i.e. community) will.
Energy resources exemplify these issues. Reliable energy supply is essential
in all economies for lighting, heating, communications, computers, industrial
equipment, transport, etc. Purchases of energy account for 5–10% of
gross national product in developed economies. However, in some developing
countries, energy imports may have cost over half the value of total
exports; such economies are unsustainable and an economic challenge for
sustainable development. World energy use increased more than tenfold
over the 20th century, predominantly from fossil fuels (i.e. coal, oil and
gas) and with the addition of electricity from nuclear power. In the 21st
century, further increases in world energy consumption can be expected,
much for rising industrialisation and demand in previously less developed
countries, aggravated by gross inefficiencies in all countries. Whatever the
energy source, there is an overriding need for efficient generation and use
of energy.
Fossil fuels are not being newly formed at any significant rate, and thus
present stocks are ultimately finite. The location and the amount of such
stocks depend on the latest surveys. Clearly the dominant fossil fuel type by
mass is coal, with oil and gas much less. The reserve lifetime of a resource
may be defined as the known accessible amount divided by the rate of
present use. By this definition, the lifetime of oil and gas resources is usually
only a few decades; whereas lifetime for coal is a few centuries. Economics
predicts that as the lifetime of a fuel reserve shortens, so the fuel price
increases; consequently demand for that fuel reduces and previously more
expensive sources and alternatives enter the market. This process tends to
make the original source last longer than an immediate calculation indicates.
In practice, many other factors are involved, especially governmental
policy and international relations. Nevertheless, the basic geological fact
remains: fossil fuel reserves are limited and so the present patterns of energy
consumption and growth are not sustainable in the longer term.
Moreover, it is the emissions from fossil fuel use (and indeed nuclear
power) that increasingly determine the fundamental limitations. Increasing
concentration of CO2 in the Atmosphere is such an example. Indeed, from
an ecological understanding of our Earth’s long-term history over billions of
years, carbon was in excess in the Atmosphere originally and needed to be
sequestered below ground to provide our present oxygen-rich atmosphere.
Therefore from arguments of: (i) the finite nature of fossil and nuclear fuel
materials, (ii) the harm of emissions and (iii) ecological sustainability, it
is essential to expand renewable energy supplies and to use energy more
efficiently. Such conclusions are supported in economics if the full external
costs of both obtaining the fuels and paying for the damage from emissions
are internalised in the price. Such fundamental analyses may conclude that
renewable energy and the efficient use of energy are cheaper for society
than the traditional use of fossil and nuclear fuels.
The detrimental environmental effects of burning the fossil fuels likewise
imply that current patterns of use are unsustainable in the longer term. In
particular, CO2 emissions from the combustion of fossil fuels have significantly
raised the concentration of CO2 in the Atmosphere. The balance of
scientific opinion is that if this continues, it will enhance the greenhouse
effect1 and lead to significant climate change within a century or less, which
could have major adverse impact on food production, water supply and
human, e.g. through floods and cyclones (IPCC). Recognising that this is
a global problem, which no single country can avert on its own, over 150
national governments signed the UN Framework Convention on Climate
Change, which set up a framework for concerted action on the issue. Sadly,
concrete action is slow, not least because of the reluctance of governments
in industrialised countries to disturb the lifestyle of their voters. However,
potential climate change, and related sustainability issues, is now established
as one of the major drivers of energy policy.
In short, renewable energy supplies are much more compatible with sustainable
development than are fossil and nuclear fuels, in regard to both
resource limitations and environmental impacts .
Consequently almost all national energy plans include four vital factors
for improving or maintaining social benefit from energy:
1 increased harnessing of renewable supplies
2 increased efficiency of supply and end-use
3 reduction in pollution
4 consideration of lifestyle.

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