Any experts on fuel cells around here?greenspun.com : LUSENET : TB2K spinoff uncensored : One Thread
I recently had the opportunity to have a brief dialog with a representative of Avista on a local radio station call in show. The radio station is KSMF; the commentator is Jeff Golden. There is a forum available as well, at www.jeffnet.org. (the "jeff" in that name stands for Jefferson Public Radio)
I called to challenge the statement that fuel cells only byproduct is water vapor. The current fuel cells are being designed to "burn" either propane or natural gas, both of which are hydrocarbons. So my position was that there HAD to be other byproducts they weren't bothering to mention--presumably carbon dioxide, or carbon dioxide.
The Avista rep told me that there is another byproduct, but it was pure carbon (in other words, it was not "burned" or otherwise oxidized in the process) This is very encouraging, if true, as we could certainly use the pure carbon for many things.
Anyone here care to verify, or contradict the man's statement?
-- jumpoff joe (firstname.lastname@example.org), April 21, 2000
Sorry, they are right. However, the hydrocarbons do not come without a pollution cost. Unless you are using solar to split water into hydrogen and oxygen for a hydrogen cell, your stuck with by-products.
Incidently, people should re-read or get the old book, Limits to Growth by the Club of Rome. I just happen to be re-reading my copy and, ultimately, THSF reagrdless of what actions are taken. The book came out around 1972.
-- Todd Detzel (email@example.com), April 21, 2000.
If a fuel cell's inputs were only hydrogen and oxygen, as on US spacecraft AFAIK, then indeed its only byproduct (aside from the principal product of electricity, and ignoring contaminants) would be water vapor.
2 H2 + O2 => 2 H2O
But if a fuel cell's input includes hydrocarbons, then the carbon has to go somewhere -- whether it's called a "byproduct" might depend on what the cell's principal products, besides electricity, are considered to be.
I'm not up-to-date on fuel cell development, and don't know whether it's feasible for a fuel cell design to produce pure carbon as a result of its reactions on hydrocarbon and oxygen input, perhaps with the proper catalyst.
But I do clearly recall the day when my high school chemistry teacher called me up to the front to help demonstrate what happens when one adds sulphuric acid to sugar. A black porous smelly mass erupted from the sugar like a slow jack-in-the-box because, according to the teacher, the sulphuric acid pulled all the hydrogen and oxygen out of the sugar, leaving only pure carbon (with some sulphur compund contaminants to teach the experimenter not to watch the experiment from too close a distance).
-- No Spam Please (firstname.lastname@example.org), April 21, 2000.
Environmental Acceptability - Because fuel cells are so efficient, CO2 emissions are reduced for a given power output. By 2000, fuel cell power plants are projected to decrease CO2 emissions by 0.6 MMT of carbon equivalent. The fuel cell is quiet, emitting only 60 decibels at 100 feet. Emissions of SOx and NOx are 0.003 and 0.0004 pounds/megawatt-hour respectively. Fuel cells can be designed as water self-sufficient. Since fuel cell exhaust is primarily water and CO2 natural gas fuel cell powerplants have a blanket exemption from regulations in California's South Coast Air Quality Management District. The emission restrictions are possibly the strictest in the nation.
Here's one good source for links on fuel cells:
-- FactFinder (FactFinder@bzn.com), April 21, 2000.
I don't know diddly squat, but when Bill Gates bought 5% of Avista, I decided he was a lot smarter than I and we bought in too. Taz
-- Taz (Tassie123@aol.com), April 21, 2000.
There are actually serveral different kinds of fuel cells - some that use pure hydrogen and oxygen, and others that burn various kinds of carbon/hydrogen mixtures. The one being developed for automotive use (the Proton Exchange Membane fuel cell) can run on pure hydrogen, as well as natural gas, alcohol, and gasoline. If it is fed pure hydrogen, it will produce zero pollution; otherwise it will not. One would hope that the ultimate source of energy would be a renewable source (such as photovoltaics), separating water into hydrogen and oxygen, so that the fuel cell can run on pure hydrogen.
-- Jim (email@example.com), October 10, 2001.
In order to reduce or eliminate greenhouse gas pollutants, the fuel cell must run on hydrogen or natural gas (methane).
For the hydrogen case, a complete zero emission cycle would be electrolysis -> split water into H2 and O2 -> fuel cell -> water and electricity. Of course, everyone knows that you need more energy to do the electrolysis than you would gain from the fuel cell. So, solar power or wind power would be the best complement to provide an economical solution. If you were to use hydroelectricity, you could still come out ahead in terms of money. Consider this scenario, use electricity during off-peak times when it's cheaper (middle of the night) to produce your hydrogen. Store your hydrogen in a tank and then use it during peak times to produce electricity with the fuel cell. You could sell this electricity back to the utility company during peak times (when electricity is a premium) and make a little money.
Natural gas is widely considered a non-renewable resource but they is one source: anaerobic digester gas. That is, getting methane from your garbage. There are some companies that convert household garbage into methane. This gas can be sent to a fuel cell to produce electricity. Of course, depending on the fuel cell type, you might need a fuel processor to convert the methane into usable hydrogen which leads us to carbon dioxide emissions. This will always be a product but it will be at substantially lower amounts when compared to propane, butane, or gasoline. (A simple way to think about it is the number of carbons per molecule. For instance, methane has one carbon while propane has three carbons. So, methane would produce less carbon dioxide than propane.)
Hope this helps!
-- Ben (firstname.lastname@example.org), January 18, 2002.