Project in Brazil studies technologies to integrate offshore wind farms into the country's power grid

Work conducted at the Research Center for Greenhouse Gas Innovation will also analyze the best way to bring electricity to oil platforms off the Brazilian coast.

Agência FAPESP* – What is the best technology to transmit the electricity produced by future offshore wind farms off the coast of Brazil to the mainland? And what is the best way to supply electricity to oil and gas platforms installed in Brazilian waters? A project by the Research Center for Greenhouse Gas Innovation (RCGI) has begun to investigate these two questions as part of a new program funded by the multi-energy company TotalEnergies.

The RCGI is an Engineering Research Center (ERC) created with the support of FAPESP and companies at the University of São Paulo’s Engineering School (POLI-USP).

Twenty researchers, including professors, postdoctoral students, doctoral students, master’s students, and undergraduates, will work over three years to develop tools that can help select the most appropriate technology for energy transmission in each case.

“The project has two distinct objectives that share a common element: the transmission of energy by sea. The first involves bringing energy to the coast from offshore wind farms. The other will take energy from the coast to the oil and gas exploration platforms,” says electrical engineer Renato Machado Monaro, professor at POLI-USP and coordinator of the project “Investigation of offshore transmission technologies off the Brazilian coast applied to oil and gas exploration and the integration of wind farms (TransBRcoast).” The initiative is also supported by FAPESP through a project coordinated by Monaro.

“The two strands have different characteristics. Offshore wind farms will be built close to the coast; the projects envisage distances of up to 20, 30 kilometers from the beach, most of them still on the continental shelf, where the water table is shallower. Oil platforms, on the other hand, are installed where the oil is,” explains the professor.

He adds that Brazilian platforms with structures for oil and gas exploration are located on average 148 kilometers away, with the farthest reaching 300 kilometers from the coast, in the Santos basin, in deep or ultra-deep waters. The energy consumed on these platforms comes from the gas in the exploration well itself. In other words, they currently operate as an isolated system, but the idea is to decarbonize oil extraction as much as possible.

In the context of climate change, companies and countries have been working towards an energy transition period where there is gradual decarbonization of activities. “With the electrification of platforms, we’ll reduce our dependence on oil, we’ll emit less CO₂ in this exploration,” says Monaro. “Maybe in our lifetime we’ll see a society with much less oil, but I don’t think it’ll disappear.”

Brazilian conditions

In the first phase of the project, the researchers are studying the technological limits, the costs of systems and materials already used in other countries, such as transmission cables, transformers, converters, etc., as well as future prospects. They are also investigating the generating capacity of planned wind farms and how much energy they are expected to produce, as well as assessing the amount of energy consumed by current platforms.

“To a large extent, what we need to know for the transmission system is how much energy will be transmitted and over what distance,” says Monaro. The project’s final report will be submitted to the National Agency for Petroleum, Natural Gas and Biofuels (ANP) and made public.

In the case of Brazilian oil, in addition to the distance, the researchers will also have to take into account the adversities posed by the depth of the water table in the places where exploration is carried out. “The big challenge will be to find the cheapest and most reliable technology. If the transmission systems are too expensive or unsuitable for the conditions of the project, the investment becomes unattractive,” says the engineer.

Three technologies will be investigated, both for connecting an offshore wind farm to the coast and for integrating the grid with the platforms. “Each has its own characteristics and costs. At certain distances, one technology begins to prevail over the other,” says the project coordinator.

According to the researchers, high voltage alternating current transmission at a conventional frequency (50/60 Hz) is the most technologically mature configuration. However, the maximum transmission distance is limited to about 50 kilometers from the coast.

An alternative is to reduce the frequency, which reduces energy transmission losses and consequently increases the power transferred. Known as low frequency alternating current (LFAC), this technology consists of transmitting high voltage alternating current at a third of the conventional frequency (16.67/20 Hz).

In this case, an AC/AC power converter must be installed on shore to change the transmission frequency before connecting the offshore system to the onshore grid. Although studies in the technical literature indicate that LFAC technology is suitable for transmission over medium distances of 30 to 75 km, in practice it has only been applied to railway systems in Europe, the RCGI team cautions.

Many of the technical challenges associated with transmission losses can also be overcome by using direct current. In this case, high voltage direct current (HVDC) technology stands out because it can be applied to long-distance projects. In the context of offshore applications, an HVDC network would require the installation of onshore and offshore AC/DC converter stations, which would increase costs.

“For each of these three technologies, there’s a whole discussion about equipment availability, cost, and technological limits,” Monaro concludes. “Of course, it’s not one study that brings definitive results, but it starts the investigation and brings evaluation vectors.”

* With information from the RCGI.