Itaipu Dam - Paraguay . Brazil

The Itaipu main dam is a concrete dam, of the hollow gravity type. During the initial conception of the project options were studied: solid gravity, hollow gravity, rockfill and in an arc.

After technical and geological evaluation, it was chosen the concrete dam of hollow gravity type for the main dam. The other dam types built at Itaipu, auxiliary dams, such as rockfill and earthfill used rocks and substrate (earth) from local excavations.

The Itaipu Dam is a hydroelectric dam on the Paraná River located on the border between Brazil and Paraguay. The name "Itaipu" was taken from an isle that existed near the construction site. In the Guarani language, Itaipu means "the sound of a stone". The American composer Philip Glass has also written a symphonic cantata named Itaipu, in honour of the structure.

The dam is the largest operating hydroelectric facility in terms of annual generating capacity, generating 94.7 TWh in 2008 and 91.6 TWh in 2009, while the annual generating capacity of the Three Gorges Dam was 80.8 TWh in 2008 and 79.4 TWh in 2009^[1]. It is a binational undertaking run by Brazil and Paraguay at the Paraná River on the border section between the two countries, 15 km (9.3 mi) north of the Friendship Bridge. The project ranges from Foz do Iguaçu, in Brazil, and Ciudad del Este in Paraguay, in the south to Guaíra and Salto del Guaíra in the north. The installed generation capacity of the plant is 14 GW, with 20 generating units providing 700 MW each with a hydraulic design head of 118 m. In 2008 the plant generated a record 94.68 billion kWh, supplying 90% of the energy consumed by Paraguay and 19% of that consumed by Brazil.

Of the twenty generator units currently installed, ten generate at 50 Hz for Paraguay and ten generate at 60 Hz for Brazil. Two 600 kV HVDC lines, each approximately 800 km long, carry both Brazilian and Paraguayan energy to Sao Paulo where the terminal equipment converts the power to 60 Hz.

History

Negotiations between Brazil and Paraguay

The concept behind Itaipu Power Plant was the result of heavy negotiations between the two countries during the 1960s. The "Ata do Iguaçu" (Iguaçu Act) was signed on July 22, 1966, by the Brazilian and Paraguayan Ministers of Foreign Affairs, Juracy Magalhaes and Sapena Pastor, respectively. This was a joint declaration of the mutual interest in studying the exploitation of the hydric resources that the two countries shared in the section of the Paraná River starting from, and including, the Salto de Sete Quedas, to the Iguazu River's watershed. The Treaty that gave origin to the power plant was signed in 1973.

The terms of the treaty, which expires in 2023, have been the subject of widespread discontent in Paraguay. The government of President Lugo vowed to renegotiate the terms of the treaty with Brazil, which long remained hostile to any renegotiation.

In 2009, Brazil agreed to a fairer payment of electricity to Paraguay and also allowed Paraguay to sell excess power directly to Brazilian companies instead of solely through the Brazilian electricity monopoly.

Construction starts

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In 1970, the consortium formed by the companies IECO (from the United States of America) and ELC Electroconsult S.p.A. (from Italy) won the international competition for the realization of the viability studies and for the elaboration of the construction project. Work began in February 1971. On April 26, 1973, Brazil and Paraguay signed the Itaipu Treaty, the legal instrument for the hydroelectric exploitation of the Paraná River by the two countries. On May 17, 1974, the Itaipu Binacional entity was created to administer the plant's construction. The works began in January of the following year.

Paraná River rerouted

On October 14, 1978, the Paraná River had its route changed, which allowed a section of the riverbed to dry so the dam could be built there.

Agreement by Brazil, Paraguay, and Argentina

An important diplomatic settlement was reached with the signing of the Acordo Tripartite by Brazil, Paraguay and Argentina, on October 19, 1979. This agreement established the allowed river levels and how much they could change as a result of the various hydroelectrical undertakings in the watershed that was shared by the three countries. At that time, the three countries were ruled by military dictatorships. Argentina was concerned that, in the event of a conflict, Brazil could open the floodgates, raising the water level in the River Plate and consequently flood the capital city of Buenos Aires.

Formation of the lake

The plant's reservoir began its formation on October 13, 1982, when the dam works were completed and the side canal's gates were closed. Throughout this period, heavy rains and flooding accelerated the filling of the reservoir as the water rose 100 meters (330 ft) and reached the gates of the spillway at 10 a.m. on October 27.

Start of operations

On May 5, 1984, the first generation unit started running in Itaipu. The first 18 units were installed at the rate of two to three a year; the last two of these started running in the year 1991.

Capacity expansion in 2007

The last two of the 20 electric generation units started operations in September 2006 and in March 2007, thus raising the installed capacity to 14 GW and completing the power plant. This increase in capacity will allow for 18 generation units to remain running all of the time while two stay down for maintenance. Due to a clause in the treaty signed between Brazil, Paraguay and Argentina, the maximum number of generating units allowed to operate simultaneously cannot exceed 18 (see the agreement section for more information).

The rated nominal power of each generating unit (turbine and generator) is 700 MW. However, because the head (difference between reservoir level and the river level at the foot of the dam) that actually occurs is higher than the designed head (118 m), the power available exceeds 750 MW half of the time for each generator.

Each turbine generates around 700 MW; by comparison, all the water from the Iguazu Falls would have the capacity to feed only two generators.

Energy

The Itaipu power plant is, at present, the largest hydroelectric power plant in the world as regards the generation of energy. With 20 generator units and 14,000 MW of installed power, it supplies 18,9% of the energy consumed in Brazil and 77,0% of the Paraguayan demand.  

In 2009, the Itaipu power plant generated 91.651.808 megawatts-hour (MWh), the fourth highest in 25 years of power production.

The historic record for electricity production was set in 2008, with a production of 94,684,781 megawatts-hour (MWh). The previous record had been set in 2000, when Itaipu generated 93,427,598 MWh.

Powerhouse

The Powerhouse concentrates the electromechanical equipment responsible for generating electricity at Itaipu. This equipment comprises the scroll casing, the turbine, the generator, the excitation system and the speed governor.

Production from year to year

In 2009, the Itaipu power plant generated 91,651,808 megawatts-hour (MWh), the fourth highest in 25 years of power production. 

This volume of power had never been achieved by any other hydro power plant in the world. The Three Gorges plant China is building on the Rio Yang-Tse River should not surpass Itaipu in terms of production. Once it is finished, the Chinese power plant will have 22,400 megawatts (MW) in installed capacity, compared to Itaipu's 14,000 MW. The latter's advantage over Three Gorges is its hydrological situation: the Paraná River, where Itaipu is located, has a great volume of water all year round.

The electricity generated by Itaipu in 2009 would be enough to supply the entire worldwide consumption for about two days; serve a country like Argentina for 10 months; and Paraguay, a partner in this enterprise, for 9 years. It could also supply the electricity demand of 21 cities the size of greater Curitiba for one year.