IN DEPTH: Sweet opportunity for Brazilian solar

The concentrating solar power (CSP) sector has fallen on hard times globally, but it may be about to get an unexpected boost from a centuries-old Brazilian industry: sugar.

A growing number of experts believe that integrating CSP technology with Brazil’s vast and expanding fleet of biomass-fired power stations can create a multi-gigawatt industry providing 100% renewable energy around the clock 365 days a year.

While still largely untested, the idea is attracting some of the CSP world’s heaviest hitters, including Spain’s Abengoa, and the Brazilian government recently expanded an R&D programme for stand-alone CSP to include such hybrid plants.

The idea is simple. Today, roughly half of Brazil’s 355 sugar mills have on-site power plants fuelled by bagasse, the fibre-rich, high-energy material that is left over after the cane has been crushed to remove the juice that is processed into raw sugar or ethanol.

These bagasse-fuelled plants — typically ranging from 40-100MW — sell their excess power onto the grid and play a huge role in Brazil’s electricity system. Together, they produce 11GW of generation capacity spread across the country’s sunniest regions, making them the country’s second-largest source of electricity after hydropower. The government expects the country’s installed base of bagasse-fired plants to reach 18GW within a decade.

The drawback to these biomass power stations is that bagasse is only produced during the seven- to nine-month sugarcane harvest season, leaving operators needing to buy wood pellets or other forms of fuel to keep the plants generating electricity year round.

Sugar mills have tried a variety of fuel sources to smooth out the seasonal and market-based variations in their bagasse supplies — including natural gas, grass from their plantations, and biogas produced from vinasse, the slop left over after distilling the cane juice.

But the smartest solution may prove to be above their heads: the Sun.

The Brazilian government has been funding CSP research for the past five years, with backing from Germany’s international development agency, which saw an opportunity for German companies to supply CSP components.

But Brazil kicked off a new strategic R&D programme for CSP in September, with the intention of getting a series of pilot projects built across the country. Critically, the decision was taken to include hybrid biomass/CSP plants.

“We were initially looking at pure CSP power generation projects, but we changed the rules to allow these hybrid projects,” says Carlos Cabral, an adviser to the board of power regulator Aneel, which is overseeing the programme. 

More than two dozen companies have declared an interest in building pilot CSP plants in Brazil as part of the programme, including Abengoa, Iberdrola, Enel Green Power, China’s State Grid, local developer CPFL and São Paulo state power company CESP.

It remains to be seen whether a commercial CSP market will take off in Brazil. But the government used a similarly structured and funded R&D programme four years ago to kick-start the country’s PV industry — three years ahead of Brazil’s first PV auction.

Aneel, expects a similar timeline before the country’s first CSP auction, which would mean the first commercial projects would be set in motion around 2019.

Some sugar mill operators have been looking at integrating CSP for years. One such operator is Jalles Machado, a large sugar mill in Goiás state with a 40MW bagasse-fired power plant.

“Here in Goiás we have very good solar irradiation, so we thought we could use solar power and [conserve] the bagasse so we could generate power during the whole year,” says Otávio Lage de Siqueria Filho, chief executive of the Jalles Machado mill.

An initial feasibility study, backed by Abengoa and the University of Brasília, found that CSP did not make economic sense at Jalles Machado. With an estimated generation cost of R$400 ($101) per MWh, it would have been impossible to get financing, says Siqueria Filho.

But Celso Oliveira, a researcher at the University of São Paulo, says CSP can be integrated more cheaply than earlier studies indicate.

Bagasse-fuelled plants already have steam turbines and transmission lines in place, meaning those costs can be stripped out of the equation. And there is no need to build expensive storage systems, because the bagasse can be burned during the night, allowing the plant to generate power around the clock.

The total cost of building a CSP solar field and tower can be reduced to about a third of what previous studies have found, says Oliveira.

For Jalles Machado, a CSP plant would require just 20 of its 50,000 hectares of land.

Oliveira has drawn up plans for a 10MW pilot power-tower hybrid project that uses water as the heat-conducting fluid, rather than more expensive oils or molten salt.

This project is backed by local CSP start-up Solinova, and Jalles Machado are in talks with some of the power companies targeting Brazil’s CSP R&D programme.

The Brazilian Union of Sugar and Ethanol Industry (Unica) welcomes the idea of combining solar and biomass.

But it says the government must now offer good cap prices at national auctions to enable biomass power producers to modernise their existing plants and start thinking about adding CSP.