When we talk about clean and renewable electricity generation, we immediately think of two specific cases: wind and solar. That's because turning wind into electricity using turbines (reminiscent of giant weather vane) and using cells to convert sunbeams are technologies that have been in practical use for some time.
Sought by Tilt, the National Electric Energy Agency (Aneel) reported that the generation of electricity through wind farms and solar corresponds to 9.09% and 1.27% of the Brazilian energy matrix, respectively. In all, there are 615 wind and 2,474 solar plants in operation in the country — and 56 new wind and 30 solar plants are under construction.
It is a very different stage of use than seen with another technology for generating renewable energy: the one that uses tidal power.
Present in countries such as the United Kingdom and Canada, this method consists of using the tidal "back and forth" to move turbines and thereby generate electricity. It is a process similar to that used in wind farms, with one advantage: because it is denser, water exerts a greater force on turbines and consequently generates more energy.
"This is another possibility of extracting renewable energy from the ocean. It is possible to use the movement of waves, wind over the sea, temperature variation and also salinity," explains Gustavo Assi, professor of the Department of Naval Engineering at USP Polytechnic School.
Where to install?
Assi has been studying the topic since 2013 and brought together a group of about 40 researchers from Poli and the USP Oceanographic Institute, aiming to leverage a project on the subject that aims to map the Brazilian coast to know the best places for installations in the region. type.
Locating points of the Brazilian coast that allow the installation of turbines of this type is one of the main challenges, considering that we speak of 9,200 km long, a distance that takes into account the protrusions and recesses of the coast.
The analysis needs to be careful for one particular reason: landforms, with channels between mainland and islands, tend to be perfect spots for setting up a tidal power farm.
"The idea is to find places where there is a good variation of tides, such as the north coast of Brazil, where the sea varies from five to eight meters high between low and high tide. That adds up to a favorable geographic accident and we have an interesting situation, "says Assi.
This survey has the help of maps of entities such as the Brazilian Navy and the Port Authority. But it needs to be adjusted, since in this case the main interest is not to determine shipping routes, but a survey of the energy potential of the coast.
"The idea is to identify points with great potential and then make a more targeted analysis. For this, we will use computational models," says the professor, noting that other factors need to be taken into account. One is the presence of sediment in the water, which tends to shorten equipment durability — and, by the way, make it more expensive to operate.
In addition, each chosen location demands specific positioning of each turbine so that they do not disrupt the operation of each other. And, albeit on a smaller scale, we also need to analyze the environmental impact, as these moving turbines can cause changes in the underwater bed and impair fish reproduction.
Assi's group plans to propose this mapping in the second half of this year, so that it will begin in the second half of next year. It is expected to take four to five years to complete.
The professor states that it is not possible to estimate how soon Brazil would produce electricity from these turbines, but it is still optimistic.
"Building and installing a farm is something that depends on legislation and demand, but we need to consider that we are not dealing with new technology. After all, turbines have been around for a long time. Another positive point is that Brazil has mastered ocean-based technology." , says, citing cases such as the oil and gas extraction platforms of Petrobras, one of the world references in this area.
Once the research goes further, it will be the first such concrete movement in Latin America.
When we talk about a new way of generating electricity, one of the first questions that comes to mind is: is it worth it?
In the case of tidal energy generation this is no different. And, as with most renewable energy plants, the initial cost tends to be much higher than the installation of more traditional plants.
Taking Europe as an example, Assi says the average cost is 4,400 euros for each kilowatt (kW) installed. "Considering a turbine that generates 1 Megawatt (MW) of power, its cost would be 4.4 million euros," says Assi. He mentions that in a plant like Itaipu, the cost of the kilowatt corresponds to half of that value.
And how much could a tidal power farm feed? According to Assi, a complex with ten turbines would be able to feed about 20,000 homes, or somewhere around 100,000 inhabitants.
The teacher points out, however, that looking only at cost in this case is a mistake. "What pays for this investment is the lower impact and the cost of clean energy. We need to evaluate renewable energy in the long run. And in the case of turbines, they don't necessarily have to be integrated into the country's power grid. can be built to power facilities that are too far away to be connected to the power grid with oil and gas extraction platforms. "
Another point that weighs in favor not only of this method but of all clean energy means is pollution in the case of thermoelectric plants and the lack of resources such as the space for the construction of new hydroelectric plants.
Finally, a specific advantage of tidal movement power generation is its predictability and inexhaustible energy source. "Unlike wind energy, which depends on winds, and solar energy, which depends on the incidence of light, with tidal energy we can accurately predict energy generation. In addition, as long as the Sun, Earth and Moon circulate between them, it will be possible to generate energy in this way. That is: forever ", concludes the teacher.
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