Here's another antidote to MDTL's hype! Compare:
- the first statement by MDTL's Lifton, in which he makes the wild claim that MDTL "invented" the liquid electrolyte
- the second statement by Hockaday (of MHTX, a competitor of MDTL).
PEM's (a membrane alternative to liquid electrolytes) go back to GE in the late 1950s. But fuel cells go back to 1839 -- they've been based on non-PEM liquid eletrolytes for a long time. Even the alkaline iquid electrolytes that MDTL uses were not invented by MDTL (although it claims to have created a particular method of using them).
Bottom line: MDTL has nothing. It took an existing technology that has not been widely adopted for micro fuel cells because of its many problems (caustic liquids, and the inability of fuel cells made with it to work in any orientation) and they hypes it to the moon.
- Charles
== MEDIS HYPE == THEY "INVENTED" LIQUID ELECTROYLTES!!!! ===
Ethanol fuel cells take aim at portables' power www.eetimes.com/story/OEG20010713S0075
July 17, 2001
Medis said the "X-additive" allows engineers to scrap proton exchange membranes, typically used in large hydrogen-based fuel cells. Proton exchange membranes, or PEMs, are considered too bulky and costly for the smallest fuel cell applications, and they can be damaged by high concentrations of methanol or ethanol. "Our people recognized that you can't make a small fuel cell with a PEM," Lifton said. "So they invented the proprietary liquid electrolyte."
===== A COMPETITOR SPEAKS ================
fuelcellsworks.com [EXCERPTS]
HOCKADAY: The Medis El Patent applications are publishing now and many of the details are what we suspected. Their "magic" electrolyte ingredients appear to be sodium borohydride and potassium hydroxide. This is caustic and messy stuff, and it means their fuel will be gradually filled with a solid carbonate as it runs. In the past we considered using this fuel mixture in some of our unique fuel cells.
ANDERSON: Regarding Medis El, have you ever tried using this "magic" formula. And what do you think that their real problems will be in the future. I still believe they have not come up with a solution to the orientation problem.
HOCKADAY:
A basic problem is that the very alkaline electrolyte will form low solubility carbonates from the carbon dioxide produced and from the air that would be expected to fill the fuel cell electrodes. Changing the fuel or electrolyte would be expected to be messy. This is the same situation that the zinc air battery faces.
Another problem with these salt type electrolytes is that they can dehydrate or over hydrate depending on the surrounding relative humidity. When the cell's electrolyte excessively absorbs water from the surroundings it can flood the air electrode and leak out of the cell. The caustic electrolyte can corrode the surrounding equipment, clothing and skin. Or, if the electrolyte is dehydrated it can shrink the electrolyte and loose ionic continuity through the cell. This is a similar situation for alkaline batteries and zinc air batteries, and this is why they operate as nearly sealed systems.
This fuel, if not used, will evolve hydrogen. So, it will gradually lose its energy and some provision needs to be in place to vent the hydrogen, or chemically store it. At higher temperatures this hydrogen evolution is accelerated.
I suppose Medis El might have a gravity problem if there is a bubble in their cell and the cell is placed such that the bubble prevents the electrodes from having continuous electrolyte between them.
In talking to someone who claimed to have studied under the Nobel Prize winner for conductive polymers, he suggested that the conductive polymer would be very sensitive to the chemical surroundings. So, the conductive polymers may not be very conductive in strong acids or bases. We tried some conductive polymers in simple fuel cell tests and did not see any significant improvement in current collection. |
