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Energy

On the waves of the sea

Port in Ceará will have an electricity generation plant developed at UFRJ

The port of Pecém in Ceará, 60 kilometers from Fortaleza, will be the first spot on the Brazilian coast to house a pilot plant for generating electricity from the waves of the sea.  When it is completed, on a commercial scale, it will be capable of generating 500 kilowatts (kW) to start with, sufficient to meet the consumption needs of 200 families. The main technological innovation in relation to the wave power stations developed in other countries, many still at the test stage, is the use of a hyperbaric chamber – a steel container that stores compressed water and simulates the pressures existing on the bottom of the sea – to produce energy.

The hyperbaric chamber is already being used at the Submarine Technology Laboratory of the Graduate Engineering Project Coordination (Coppe), of the Federal University of Rio de Janeiro (UFRJ), responsible for the coordination of the project, to study the behavior of the structures used in the production of petroleum in deep waters. It was this experience that led the researchers from the institution, coordinated by Professor Segen Stefen, from the Oceanic Engineering Program, to conceive a device for the plant to work in a similar way as a hydroelectric plant.

In the sea, at a distance of roughly 3 kilometers from the beach, on the port’s breakwater, floats are installed, connected to a metallic structure in the form of a beam 22 meters long. With the passage of the waves, the floats move up and down and act as a sort of pump, driving the water stored in a tank through a tube to the high-pressure hyperbaric chamber. The chamber simulates the pressure of a waterfall, like that of a hydroelectric power plant, which drives turbines to generate electricity.

A hydroelectric power plant, after damming the water of the river, has a waterfall of from 100 to 200 meters, which is responsible for spinning the turbine that is down below. In the case of the wave power station, the water from the sea is stored in the hyperbaric chamber. “The power of the hydroelectric power plant is provided by the flow of the water multiplied by the pressure. Our flow is stored in the chamber, which keeps the water under a pressure equivalent to a 300 meter waterfall”, says Stefen. After the hyperbaric chamber, everything works in a conventional way, as if it were a hydroelectric power plant. The water, in the form of a jet, activates the turbine, which, coupled to the generator, produces electricity. This sequence of movements occurs continuously as long as there are waves, but stops when they cease”, Stefen explains. That is why the choice of the place for installing the plant is strategic for the success of the enterprise.

Continuous wind
In the case of the port in Ceará, it benefits from a phenomenon that occurs practically all over the Northeast, called the trade winds, which are responsible for the breeze that blows continuously. “This region does not have large waves, but they are constant”, says the coordinator of the project, who started to think of this power plant in 2001, in the days that possible energy alternatives were being discussed in Brazil for the blackout crisis. “That was the year we organized and hosted an international conference, at which the central theme of discussion was the sea”, says Stefen. He is referring to the International Conference on Offshore Mechanics and Arctic Engineering (Omae), an event promoted annually by the American Society of Mechanical Engineers, or Asme in short, located in the United States. As the Brazilian electricity crisis was a subject that was in all the discussion groups at the time, one of the themes dealt with at the conference, besides the structures for producing petroleum, was making use of the energy of the waves to generate electricity.

The first step to take the idea of using the energy of the sea forward began with a survey of what was being done at that moment in other countries. After a seminar about the potential of the energy from the waves in Brazil, supported by the Ministry of Mines and Energy and held in 2002 in Rio de Janeiro, the project effectively began to take shape, with studies about size, target public and working model. Several other surveys were done by the researchers, to evaluate the viability of developing the first wave power station in the Americas. One of them shows that the Brazilian coast has the potential for supplying 15% of the total of the electricity consumed in the country, around 300 thousand gigawatts a year today. “With 8.5 thousand kilometers of coast and about 70% of the population occupying regions up to 300 kilometers from the coast, the country shows favorable conditions for getting advantages from this source of abundant, renewable and nonpolluting energy”, says Stefen. An estimate of the cost of the energy from the waves points indicates that it should come to between the costs of a hydroelectric plant – US$ 1 thousand the kW – and the wind farm – US$ 1.4 thousand the kW. “Only the commercial version will bring the exact amount”, is the proviso of Eliab Ricarte Beserra, a doctoral student taking part in the project.

Oceanic tank
Small scale models of the wave power station were tested in Coppe’s oceanic tank, which simulates marine environments at depths of up to 5 thousand meters, to evaluate the resistance of the product to dire conditions. Dimensioning the prototype on a real scale has also been done now. Within a month, the measurements of the location will be taken, and the forecast is that by the end of 2005 the first two modules of the prototype will begin to be installed; they are going to generate 50 kilowatts, sufficient energy to illuminate a small factory and make it work. The power plant was conceived in modular form to facilitate its expansion, when there is a need for generating additional energy. “Monitoring of the prototype of the power plant will be carried out over two years to evaluate how to improve the performance and optimize the machine, until arriving at the final product”, Stefen explains. It is only after this that the energy from the commercial model will be supplied to the conventional electricity network. In this stage, 20 modules of the power plant go into operation initially.

For researches to be extended until the pilot power plant is reached, an agreement was signed at the beginning of last year between Coppe, Eletrobrás and the Government of  Ceará. The university was entrusted with the development of the equipment and the monitoring of the prototype. For the stage of implanting the prototype, the company will give half of the amount necessary for the project, which has an estimated cost of R$ 3.5 million. The other half depends on the approval of a request made to the Financier of Studies and Projects (Finep) by Eletrobrás itself, the result of which should come out by September. The Government of Ceará will take care of the infrastructure and logistical support, to make it viable to monitor the conditions of the sea.

Energy from the waves, at the current stage, does not have the objective of replacing the other sources used today, but rather to supplement them. There is not yet a single technology for making a power plant of this kind work. One of the models most studied is the pilot plant installed in the Azores, in Portugal. It is based on an energy converting system known as OWC (which stands for Oscillating Water Column) to put the waves to good use. On land, there is an air chamber, which also contains water, connected to the sea through a submerged mouth. The elevation of the waves causes a difference in pressure of the air in the chamber. This difference works in a system of compression and decompression, which makes the turbine rotate and produce electricity using a generator.

The possible environmental impacts related to the installation of a wave power station are described as minimal by the researchers. As experience in the use of these projects is still little, it is not possible to evaluate in all their extent the effects that may be caused to the surrounding environment. “The main impact will be felt during the construction period, with all the assembly apparatus on the shore”, Beserra points out. Nevertheless, in the real model that will be assembled at the port in Ceará, the water that passes through the hyperbaric chamber and moves the turbine remains in a closed circuit, to prevent it from being returned to the sea with any kind of contamination.

Old dream
The interest in obtaining energy from the waves was given a boost in the 70s, with the oil crisis, and reinforcement, particularly amongst the European countries, with the signature of the Kyoto Protocol, which provides for a reduction in emissions of pollutant gases by as much as 12% between 2010 and 2012. One of the ways of attaining this target is to increase the participation of renewable energies in the generation of electricity. But the idea of making good use of this energy matrix is very old. In 1799, France already registered the first patent request for a wave power station. The first to work effectively using this energy was the port of Huntington, in Great Britain, in 1909, which used it to light the quay. “This power plant was destroyed by the waves themselves, since the technical knowledge in those days was incipient”, says Eliab Ricarte Beserra, from UFRJ.

Studies carried out in the United Kingdom about the energy potential available in the oceans indicate amounts in the order of 1 terawatt (TW), which means the possibility of meeting the whole demand of the planet. “Although making good use of all the energy available in the oceans is practically impossible, converting a small fraction into electricity can have great significance for the countries that master this technology”, says Professor Segen Stefen.

Several countries have done studies in this direction, such as the United States, Canada, Norway, Sweden, Denmark, the United Kingdom, Holland, Spain, Portugal, India, China, South Korea, Japan, Australia and New Zealand. Those already having installations in the sea in commercial operation are Holland, with the AWS project, with 2 megawatts (MW) of power, Portugal, with the OWC, of 400 kilowatts (kW), and the United Kingdom, with Limpet, of 500 kW. Denmark recently installed in the sea its Wave Dragon, with 4 MW in power, and the United Kingdom, a prototype which already has commercial proportions, called Pelamis, with 750 kW (please see Pesquisa Fapesp nº 112). Japan has the largest number of prototypes and has made a series of adaptations for specific purposes, such as for boats that do dredging using the energy from the waves.

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