IN DEPTH: Brazil's hybrid revolution
The dream of supplying affordable renewable energy around the clock is closer to being realised than many might think — at least, in some parts of Brazil.
Hybrid power plants that incorporate more than one energy source — usually wind and solar — are being planned by several developers, mainly in the sunny Northeast region, which has some of the world’s strongest, most consistent winds.
“In the region where we operate wind farms [the highlands of Bahia], the wind starts to pick up in late afternoon and gets stronger overnight, when the sun is not shining,” says Mathias Becker, chief executive of Renova Energia, Brazil’s biggest wind developer. “So we saw the opportunity of using the same substations and transmission lines to inject power into the grid almost 24 hours a day.”
The sparsely populated Northeast states of Bahia, Pernambuco, Rio Grande do Norte and Ceará already have a large proportion of Brazil’s wind projects, making them ideal locations to add solar power. According to recent solar maps, annual irradiation in the region is 1.5-2MWh per square metre — far higher than the 0.9-1.1MWh/square metre in Germany, where about 36GW of PV has been installed.
"In Pernambuco, the recent wind atlases we commissioned confirmed with data what we were observing: that the best wind areas coincide with good solar areas,” says Eduardo Azevedo Rodrigues, energy secretary for the state, which is actively courting developers of hybrid plants.
Developers believe that adding PV to wind farms will make their facilities more cost-effective — making optimum use of existing transmission structure and leased land, while benefiting from 24/7 output.
Brazilians have long been aware of the potential for energy synergies, especially between hydropower (which provides about 70% of the country’s electricity power) and wind — when reservoirs fill in the rainy season, winds are weaker; when the reservoirs empty, winds pick up.
Over the past 30 years, more than a dozen pilot hybrid projects have been built in the country — all of which have been small and experimental, and often involved back-up diesel-fired generators.
“We looked for examples around the world [of wind/solar hybrid power plants], but there were very few, and the ones we found combined concentrating solar power with wind,” Becker tells Recharge.
Renova is keeping its cards close to its chest over the logistics of its Caetité project, but it has revealed that it will sell the power to an undisclosed buyer on the unregulated market. It has also managed to obtain millions of reais of below-market credit from the federal government’s innovation support authority, Finep, which will cover 80% of the costs of the R$108m ($48.5m) project, and be paid back over ten years.
Several other companies, including GDF Suez subsidiary Tractebel and Queiroz Galvão Energias Renováveis, are also planning hybrid plants, and will be eager to see how Renova’s project pans out.
Italy’s Enel Green Power is planning an 11MW solar plant at its 80MW Fontes dos Ventos wind farm in Pernambuco, according to Rodrigues, and the company is already developing a 1.2MW solar/small-hydro hybrid project in the state of Mato Grosso, as well as investing in a thin-film solar/wind/diesel/energy-storage project in Chile’s Atacama Desert.
CPFL Renováveis, a unit of Brazilian power group CPFL Energia, is planning to start hybrid system testing at its 1MW Tauá pilot PV plant in São Paulo state. “This was always part of the original project because we need to understand the synergies between solar and other sources,” says Alessandro Gregori, new business development director at CPFL Renováveis.
CPFL Renováveis is currently testing different PV technologies at Tanquinho, and is now studying which type and size of wind turbine to use at the facility. It is also planning to combine solar with other energy sources elsewhere.
“We can, for example, combine solar power with biomass generators, where solar power can be used to dry the fuel, or we can use it to complement small-scale hydro projects,” says Gregori.
“But we want to study the solar technology in detail because, in the end, we want the combination of different power technologies to be the most advantageous possible, in which the sum of ‘one plus one’ has to be bigger than two.”
The challenges facing developers of large-scale hybrid projects should not be underestimated.
Typically, in Brazil’s Northeast, developers have to negotiate with dozens of smallholding land owners for each wind farm — before, during and after construction. Land leases range from R$10 per hectare per month at the prospecting stage, to tens of thousands of reais per month for each operating turbine over the 20-year contract.
So it makes sense for developers to increase the amount of power they can produce on each plot of land. However, renegotiating leases may be tricky.
“Wind power uses up only 2-3% of the land. In some places, farmers use the land below the wind towers for cattle-raising or plantations,” says Pedro Bezerra, head of power generation development at federal utility Chesf. Some landowners use the income from the turbines to increase agricultural production on their land.
The problem for solar/wind developers is that PV arrays take up a lot more space than wind turbines — a small 1MW plant will take up about 12,000 square metres — and this is land that cannot simultaneously be used for grazing animals or growing crops, he adds. Health and safety requirements also restrict access to ground-mounted solar arrays due to the high voltages involved.
Adding solar panels to wind farms also raises the issue that the existing power lines and substations may be insufficient for the increased capacity. The national grid operator, ONS, demands that all power plants’ transmission infrastructure can output 100% of their nominal capacity — even though that is something that renewables projects rarely, if ever, do.
Current regulations also do not say how transmission systems at mixed-output energy complexes should be configured. So the ONS and power regulator Aneel would have to devise and approve new rules to allow for a project’s power to reach the grid.
Similarly, it is far from clear how power purchasers would, in practice, buy the energy from a hybrid plant. Wind power in Brazil currently sells for about R$130 per MWh, with solar at an estimated R$250/MWh.
“It’s still uncertain how the power can be sold,” says Bezerra. “At the moment, I can’t imagine that the power generated by both solar and wind can be sold together, but who knows, maybe in the future it will.”
For now, developers looking into hybrid solutions will be scrutinising Renova’s experiences at Caetité, while continuing to study their own models. They will also be keen to see how the PV sector develops after the government holds its solar-only auction in October.
Nevertheless, there is a feeling of inevitability in Brazil that commercial-scale hybrid plants will become widespread across the country.
“We still have to learn a lot about solar power, but hybrids make sense,” says Gregori.
Bezerra agrees. “Combining wind and sun makes sense in a country like Brazil.”