Thursday, August 04, 2005

Microbial Fuel Cells

An article in any science journal/magazine/newspaper that talks about new ways to produce/harness electricity (preferably 'cheap') definitely grabs my attention. And a recent article in the EETimes talked about harnessing electricity from wastewater. This time, it is from the lab of Chemical engineering Professor Lars Angenent @ Washington University, St. Louis. To simply put it in one sentence..

"Angenent's microbial fuel cell design uses the bacteria from wastewater on its anode and cathode instead of platinum, enabling it to make a fuel from the water to create electricity while simultaneously neutralizing the biological matter that would otherwise have to be purged from the water. "

For the scientific types - please visit Angenent's lab and browse through some of his work available as full texts.

Quoting from the same article..

"Angenent has applied for a patent on the stacked microbial fuel cell design and received preliminary funding from Washington University to scale up the device. The university hopes to license it commercially to existing companies or to fund its own startup."

AAh!way to go..

Relevant MFC research links..
Professor Bruce Logan's research team @ Penn State
Geobacter Project @ UMass-Amherst

Some interesting (technical) reads include..
"Electricity generation by direct oxidation of glucose in mediatorless microbial fuel cells" by Swades K Chaudhuri and Derek R Lovley.
"Electricity production by Geobacter sulfurreducens attached to electrodes" by Daniel R Bond and Derek R Lovley.
"Production of bioenergy and biochemicals from industrial and agricultural wastewater" by Largus T Angenent et al.
"Electricity generation from artificial wastewater using an upflow microbial fuel cell" by Zhen He, Shelley D Minteer and Largus T Angenent.
"Harnessing microbially generated power on the seafloor" by Leonard M Tender et al.

India Slant: (Non-MFC news..)
Just last year, Professor Ajay K Sood @ IISc (along with his doctoral student Shankar Ghosh) demonstrated that an electric current and a voltage difference can be generated merely by flowing a common gas like oxygen, argon or nitrogen over a doped semiconductor.
Quoting from Dr. Sood's paper titled "Direct generation of a voltage and current by gas flow over nanotubes and semiconductors"..

"We report here a direct generation of measurable voltages and currents when a gas flows over a variety of solids even at the modest speed of a few meters per second. The underlying mechanism is an interesting interplay of Bernoulli's principle and the Seebeck effect: Pressure differences along streamline give rise to temperature differences across the sample; these in turn produce the measured voltage. The electrical signal is quadriatically dependent on the Mach number M and proportional to the Seebeck coefficient of the solids. Results are presented for doped Si and Ge, single wall and multiwall carbon nanotubes, and graphite. Our results show that gas flow sensors and energy conversion devices can be constructed based on direct generation of electrical signals."

A Business World India article rightly put the commercial aspect of the 'Sood Effect'..

"Sood's discovery can be used to generate electricity. You could bundle several wires, and all of them would produce currents that can be added up and transmitted. Windmills generate power from winds, but Sood's technique needs no moving parts. You can put wires wherever there is a gas flow, and generate electricity. The current is proportional to the speed of the flowing gas, so the principle can be used to measure velocity directly. Velocity sensors form a multibillion dollar market. It is not out of place to mention that IISc has filed a patent application in the Patent Cooperation Treaty."

Some relevant reads..
"Carbon nanotube sensors" by Shankar Ghosh, A K Sood and N Kumar.

For readers with a non-Science background..
Bernoullis' theorem (Basic, Advanced)
Seebeck Effect
Semiconductors (doping, etc explained too)

Snippet: "Use a 10-Kilowatt Brain"
A research student of Physics was conducting an experiment using an one-kilowatt power X-ray tube. On hearing that a scientist in England was experimenting on the same problem with a five-kilowatt X-ray tube, he grew dejected. When his Professor got to know of this, he walked up to the student and with supreme confidence and a smile, said: "There is a very simple solution: use a 10-kilowatt brain on the problem.” Professor Chandrashekhar Venkata Raman was speaking from experience. He had won the Nobel Prize for Physics in 1930, with simple equipment barely worth Rs 300 (approx $7), for the famous 'Raman Effect'.


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