A small heated glass container containing bubbling alcohol inside it is the initial stage of a type of fuel cell that is under development at the Institute of Nuclear Energy and Research (Ipen), in São Paulo. This equipment produces electricity by means of a chemical reaction between hydrogen and oxygen, and it uses ethanol, the alcohol made from sugarcane that is available at Brazilian filling stations, directly, without the need for another device , called a reformer. The cells work with pure hydrogen of an industrial origin, which is expensive to be obtained, or they extract this gas from a fuel (ethanol, natural gas, gasoline etc). “As far as we know, it is the first time in Brazil that ethanol is used directly in a SOFC cell”, says the researcher from Ipen, Reginaldo Muccillo, the coordinator of the research.
The cell called SOFC, which stands for Solid Oxide Fuel Cell, is pointed out as an electricity generator of great potentiality for the near future. All that is needed is a supply of hydrogen to transform the equipment into an autonomous generator and to produce up to dozens of megawatts (MW). As a comparison, the Itaipu Hydroelectric Plant produces about 12 thousand MW. Large multinational companies like Siemens, General Electric, Mitsubishi and Delphi are getting ready to go into this field. The group from Ipen is itself closing an agreement with Pirelli Labs, headquartered in Milan, in Italy, for joint studies of SOFCs.
“Many laboratories and large companies have prototypes under analysis of such items as durability, efficiency and price of the kilowatt”, says Fábio Coral Fonseca, a researcher from the group who in 2006 was at a symposium on SOFCs in Honolulu, United States, with the participation of researchers from companies and from research institutes under the sponsorship of the United States Department of Energy and of Solid State Energy Conversion Alliance (Seca in the Portuguese acronym) program, an alliance between industry, the government and the scientific community for the development of solid oxide hydrogen generators. Seca’s objective is to give an impulse to the production of these cells in formats from 3 kilowatts (kW) to 10 kW, to work as generators in residences, in industrial concerns and in military applications.
“What we are doing at Ipen is preparing what we could call a third generation of this cell”, Muccillo says. The SOFCs are characterized by having their conductor of electricity, or electrolyte, made of a ceramic material, which breaks up the molecules of hydrogen or of oxygen, making it possible to separate the electrons and consequently to generate electricity. “They are pieces of equipment conceived over 30 years ago that are only now finding new materials, new solutions for assembly and a price for them to become commercial”, says Daniel Zanetti de Florio, a researcher from the group who recently became a professor at the Federal University of the ABC (UFABC), in Santo André, in the Metropolitan Region of São Paulo.
The first generation of SOFCs, which is undergoing tests on prototypes, has the electrolyte made with zirconium oxide and yttrium oxide, substances that, like those of other generations, are extracted from minerals and industrially processed. This type of cell has now been constructed, in an experimental way, by the same group at Ipen (please see Pesquisa Fapesp nº 112). The second is made with cerium oxide, used in many experiments all over the world, and the third is produced with barium cerate and barium zirconate. They are electrolytes developed in Japanese research institutions ten years ago and that are now prepared from the Ipen team of researchers itself. “Another fundamental difference is that the first two generations are of an ionic conception, while the one developed by us to work with ethanol is protonic”, Muccillo says.
Break up of the oxygen
To understand these concepts, you have to know that the fuel cell work like batteries producing electricity for as long as there is a fuel supply. They have positive and negative electrodes (anodes and cathodes). In the generations that are about to become commercial, the molecule of oxygen (O2) is broken up on the surface of the ceramic. The electrons, with a negative charge, leave the ceramic cathode and generate electricity with the electrons of the hydrogen, which is injected and broken up on the side of the anode. The protons (H+), with a positive charge, that are left over receive the oxygen ions that pass through the electrolyte to form water (H2O), the fuel cells’ “waste”.
The path that leads to all these reactions in the SOFC happens in the opposite way in PEM (Protein Exchange Membrane) cells, in which the electrolyte is a polymer membrane conductor instead of a ceramic one. In the PEM – currently with its use more disseminated and with pre-industrial prototypes, including in Brazil, and indicated for equipping automobiles (please see Pesquisa Fapesp n° 126) – it is the proton of the hydrogen (H+) that passes through the membrane and finds the oxygen on the other side to form water, which is characterized as protonic conception. Another important difference between the two is that the PEM works at a low temperature, around 80 degrees Celsius (C), while the SOFC works at temperatures from 600 to 900ºC. “What we have managed to do is to make a ceramic cell in which it is the hydrogen protons that pass through the ceramic electrolyte”, Muccillo explains.
To make the cell work, the alcohol processed by it is initially volatilized and its molecule is broken up at 670°C, generating hydrogen and carbon dioxide (CO2). This latter gas is eliminated in the atmosphere, but there are now experiments in which it is put to use in systems to produce alcohol. The new prototype reaches 1.1 volt in power, with 20 millimeters in diameter and 1 millimeter thick, and is installed in a cabinet 5 centimeters (cm) high and 5 cm wide.
Besides alcohol, the researchers from Ipen have also made the cell work with methane gas. “That was our first idea, because we imagined putting a fuel cell on top of a landfill to use the methane that is released with the degradation of the waste for the generation of houses in the environs”, Muccillo says. But there still have to be more studies to improve a cell on a large scale. The researchers are going to present the novelty at the 10th International Symposium on Solid Oxide Fuel Cells, which will take place in the city of Nara, in Japan, this June. “Now we want to produce plates (electrolytes) that are even denser, for the gas (methane or ethanol) not to pass through in molecule form, but rather for it to be broken up with more efficiency”, says Muccillo, who receives finance from the Multidisciplinary Center for the Development of Ceramic Materials (CMDMC), one of FAPESP?s Research, Innovation and Diffusion Centers (Cepids), besides a thematic project of the Foundation and the Energy Sectorial Fund (CT-Energ) of the Ministry of Science and Technology.
1. Study of intergranular phenomena in ceramic materials
Reginaldo Muccillo – Ipen
R$415,463.52 and US$163,933.14 (FAPESP)
2. Ceramics for SOFC fuel cells
Research, Innovation and Diffusion Center (Cepid)
Elson Longo – Unesp/CMDMC
R$1,200,000.00 a year for the whole CMDMC