Barbecue energy
Carlos Luengo works on the construction of a furnace capable of
to produce a new type of vegetable 'charcoal'

JOÃO MAURÍCIO DA ROSA

The atmosphere around the hot barbecue is permeated with the aroma of volatile gases – carbon oxides, acetic acid and aldehydes, among others. If the structure of the barbecue were more efficient, it could trap these gases and transform them into electrical energy, just as is already being done with the trapped heat of a generator at the Federal University of Acre. These two energy sources – coal gases and heat from generators – are some of the research carried out at the Gleb Wataghin Institute of Physics (IFGW) at Unicamp, by the Alternative Fuels Group (GCA).

A barbecue capable of trapping gases is actually an oven. Professor Carlos Alberto Luengo points to the work, erected in the GCA’s “backyard”. Coordinator and postgraduate advisor for the Group, Luengo shows a rustic building, made of refractory bricks, with some ducts attached to the walls.

Rusticity, however, is a mere illusion. It is a sophisticated furnace for producing a new type of vegetable “charcoal”, with different properties from traditional charcoal. Properties that make it an interesting alternative for energy production and capable of supplying, for example, small rural communities that act cooperatively.

Born in Buenos Aires, graduated and received his doctorate in Bariloche, Luengo was a researcher at the University of California, San Diego for a few years. Here, he coordinates a true alternative energy production plant. Currently, in addition to the biomass roasting oven, as the brick construction is called, there is other work developed at Unicamp already in operation in Acre, cooling the air of university facilities in that State, and even capable of feeding the state electrical distribution network .

The roasting oven is being developed by the graduate student Felix Fonseca Felfli, in research with a complicated name: Study of the Introduction Routes of Toasted Biomass in the Brazilian Energy Inputs Market. “Unlike the traditional oven for charcoal production, this one conserves volatile gases that the other wastes due to the lack of precise control of temperature and burning time”, explains Félix, graduated in mechanical engineering from the University of the East, in Cuba, and PhD student in the Energy Planning course at Unicamp.

“While traditional ovens burn wood at a temperature of 400 degrees, controlled by intuition, this does not exceed 200 degrees and is controlled by exact parameters”, he informs. This control reduces the burning time from 4 or 5 days to 4 hours. It also has a superior performance: if the normal system obtains 30 kilos of charcoal from 100 kilos of firewood, the Felfli oven obtains 70 kilos. And it also preserves gases such as carbon oxides, acetic acid, aldehyde and others that are channeled to produce energy, which is the reason for the ducts in the walls.

For those who are not familiar with the gases mentioned by Felfli, Professor Luengo asks you to improve your sense of smell in front of the burning barbecue. “These are gases that are part of families’ daily lives,” he notes.

Complexity – Despite its rudimentary appearance, the construction of the experimental furnace involves complex mathematical models to simulate the process, meticulous engineering calculations to develop the design of the basic unit and experiments with the products obtained. “If it weren’t complex, it wouldn’t justify a PhD”, observes Felfli.

Unlike traditional ovens used to produce charcoal, in the shape of an igloo, which control the temperature through holes that are opened or closed, this high-tech oven has the heat controlled by strict parameters. “It is possible to accurately determine the temperature and burning time without room for error”, guarantees the researcher.

“The carbonization process aims to eliminate volatiles and water from wood to facilitate combustion and concentrate energy. Roasting will achieve the same goal, but will conserve those volatiles that have energy.” Torrefacing coal, technically called so, is considered ecologically compatible in light of current requirements and can be widely used by companies concerned with environmental preservation. “It’s an alternative to replacing wood in boiler and ceramics feed, for example,” explains Felfli.

Domestic use – Used domestically, the oven can generate energy for associations of rural producers that have raw materials such as rice straw, sugar cane and any other carbonizing products. Simply combine Felfli's equipment with a generator and a gasifier to turn on the lights or run the irrigation pump. “The oven will only consume crop residues normally wasted”, argues the researcher.

Professor Luengo believes that, as a product that is ecologically compatible with the new world order, torrefied coal has everything it needs to consolidate itself in the market as an energy alternative. “It’s a process that just needs to demonstrate its economy,” he says.

The research is financed by Fapesp (São Paulo State Research Support Fund), with a deadline for completion in two years. The result, according to Felfli, should be obtained in 2002. Market research will be carried out the following year to disseminate the product. which is already in the patenting process by Fapesp.

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University of Acre adopts energy co-generation

Located on the westernmost side of the Amazon, the State of Acre, like much of the North region, is supplied by thermoelectric energy from diesel oil transported on ferries that leave Manaus and is therefore extremely expensive. Therefore, the doctoral project by student Francisco Eulalio dos Santos, from the Federal University of Acre (Ufac), could not be more appropriate.

Known by his colleagues at Unicamp as Magnésio, Francisco came with a scholarship to implement an idea that is already producing results at his home institution. It has been taking advantage of the heat given off by Ufac generators to cool the air in its facilities; the method can also generate energy for the local electrical grid.
“Magnésio transformed a 300 kVA diesel motor generator set, similar to the emergency ones at the Hospital das Clínicas at Unicamp and very common in the North region, into a compact co-generator”, explains professor Carlos Luengo. “Using heat absorption refrigerators, he gets air conditioning and electricity.”

The professor recalls that energy cogeneration technology is widely disseminated in the paper and sugarcane industries, but its application in the tertiary sector, as Francisco dos Santos is doing, has been neglected so far.

“Ufac is the first Brazilian university to implement this form of energy conservation, but thanks to the crisis, some shopping malls and other establishments in the tertiary sector are already considering this possibility”, he informs.

Magnésio's project was developed as part of his doctorate with the CPE/FEM (Energy Planning Course at the Faculty of Mechanical Energy), in which the Institute of Physics also participates. Its presentation at Unicamp will take place as soon as the project is tested by Eletronorte, the state-owned energy company in the North region.