Hydro Power Plants.
By Emil Bedi, CANCEE and Hakan Falk, "Energy Saving Now".
HYDRO POWER PLANTS
Amongst renewable energy sources, hydroelectric
power seems to be the most desirable for utilities and its economic feasibility
has been successfully proven. Power stations with a capacity of up to 10 GW have
been built and it is estimated that there are economic resources for 3,000 GW
world-wide, compared to 10,000 GW world primary energy consumption. In Europe,
however, most hydroelectric potential has been realised, with Norway deriving
98% of its energy consumption from water power and the West German government
concluding that there are no more sites available for exploitation. World-wide
it is estimated that about 10% of resources have been realised, with most
potential remaining in Africa and Asia.
Consumption of hydro power in the world.
Present worlds total installed hydro power capacity is about 630 000 MW.
The data are uncertain because the contributions from small hydro power plants
and private systems are difficult to estimate, but it is assumed that these
facilities can add just a few per cent to the total figure. The annual power
production world-wide is 2200 TWh (billion kilowatt hours), which means that the
power plants are running at 40 % of its rated power.
The largest hydroelectric complex in the world is on the Parana River,
between Paraguay and Brazil. It is called the Itaipu Dam and its 18 turbines
produce 12 600 MW of electricity. Hydro power is growing in many regions of the
world. China and India pledged increases in large-scale hydroelectric
development. In 1999 China completed its 3300 MW Ertan hydroelectric station
which has six generating units, each with a capacity of 550 megawatts. Ertan is
Asia’s second tallest dam and China’s largest electricity supplier.
The largest hydro power plants.
 Hydroelectric projects
currently under construction in China amount to some 32 000 MW of installed
generating capacity. In India, 12 large-scale projects - adding up to 3700 MW of
installed hydroelectric capacity - have been given government approval. All the
projects are scheduled for completion by 2002. Construction on the world’s
largest hydroelectric project, the 18,2 GW Three Gorges Dam (China), entered
Phase 2 of a three-phase process in 1998. Although construction on the dam was
temporarily suspended in August 1988 because of the extensive flooding along the
Yangtze, Phase 2 is still scheduled for completion in 2003, when the dam will
start generating electricity. Phase 3 should end in 2009 with the beginning of
full power generation. About USD 3.7 billion has already been spent on
construction of Three Gorges Dam, including temporary diversion of the Yangtze
and draining of the building site so that construction of the dam can continue.
Upon completion, the project will extend 2 kilometres across the Yangtze and
will be 200 meters tall, creating a 550 km long reservoir. The official Chinese
estimate for the cost of the entire project is USD 25 billion. Three Gorges Dam
has been the subject of much controversy. Environmental and social
problems related to this projects are enormous. Water pollution along the
Yangtze will double as the dam traps more than 50 kinds of pollutants from
mining operations, factories, and human settlements that used to be washed out
to sea by the strong currents of the river. Heavy silt in the river will deposit
at the upstream end of the dam and clog the major river channels of Chongqing.
An estimated 1.1 million to 1.9 million people will have to be resettled before
the reservoir is created; around 1,300 archaeological sites will have to be
moved or flooded; and the habitats of several endangered species and rare plants
will be jeopardised. In 1996, the U.S. Export-Import Bank declined to grant
guarantees for U.S. companies hoping to work on Three Gorges Dam, citing
the potential environmental problems.
Construction is also underway on a pumped-storage station in Tibet at
Yamzho Yumco Lake. The Tibetan station is being constructed at an elevation of 4
000 to 5,000 meters, the highest project in the world. In 1997, China announced
plans to build a hydroelectric project along Tibet’s Brahmapoutre river, near
the Yalutsan mountain, which could generate a proposed 40 000 MWh per year.
Many countries of Central and South America rely heavily on
hydroelectricity for electricity generation. In Brazil - which accounts for
about 40 percent of the region’s total installed capacity - 86 percent of the 59
000 MW of total installed capacity in 1996 consisted of hydropower.
Hydroelectric dams also account for 50 percent or more of the total installed
generating capacity in Chile, Colombia, Paraguay, Peru, and Venezuela. Although
many of the region’s hydroelectric resources have been developed, there are
still plans to add substantial capacity in near future. Brazil still has more
hydroelectric projects under construction or planned for future installation
than any other country in the Central and South America region. In September
1997, the final turbine was installed in the 3 000 MW Xingó hydroelectric
power facility on the São Francisco River at Piranhas. The USD 3.1 billion
project accounts for 25 percent of the installed capacity in Northeast Brazil.
Other large hydroelectric facilities currently under construction in Brazil
include the 1450 MW Itá hydroelectric plant, which is scheduled for
completion in mid-2000, and the 1140 MW Machadinho hydroelectric plant, which is
scheduled for completion in 2003; both facilities are located on the Uruguay
River. Finally, there are also plans to expand the 12600 MW Itaipu project
held jointly between Brazil and Paraguay. The facility is to be expanded by 1400
MW at a cost of about USD 200 million.
ITAIPU - world largest hydro power plant.
HYDROPOWER POTENTIAL
There are two main factors that determine the generating potential at any
specific site: the amount of water flow per time unit and the vertical height
that water can be made to fall (head). Head may be natural due to the
topographical situation or may be created artificially by means of dams. Once
developed, it remains fairly constant. Water flow on the other hand is a
direct result of the intensity, distribution and duration of rainfall, but is
also a function of direct evaporation, transpiration, infiltration into
the ground, the area of the particular drainage basin, and the
field-moisture capacity of the soil. Runoff in rivers is a part of the
hydrologic cycle in which -powered by the sun - water evaporates from the
sea and moves through the atmosphere to land were it precipitates, and
then returns back to the sea by overland and subterranean routes.
Hydro power potential can be estimated with the help of river flows around
the world. The results show that this total resource potential is 50 000 TWh per
year – only a quarter of the world precipitation, but still over four times the
annual output of all the world present power plants. Realistic resource
potential which is based on local conditions of world rivers is in range 2 - 3
TW with an annual output of 10 000 - 20 000 TWh (UN 1992). But the important
question remains : how much of hydro potential can we afford to use (see the
chapter on environmental aspects).
A theoretical yearly production potential of 10.000 TWh of electrical
energy means that the same amount of electrical energy produced in thermal
plants with oil as fuel would require approximately 40 million barrels of
oil per day. If this is compared to the world consumption of petroleum
products, which amounted to around 80 million barrels per day in 1995. For
developing countries, who together possess almost 60 % of the installable
potential, the magnitude is striking.
COST
Hydro
power plants are very attractive for the investors. This is due to the relative
low investment costs and competitive price of electricity produced. Moreover the
life span o hydro facilities is considerably longer than for conventional fossil
power plants. There are hydro power plants which run for almost 100 years.
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