MadSci Network: Engineering

Re: What happens to the carbon in methanol when it is used in a fuel cell?

Date: Mon Jun 22 10:06:23 1998
Posted By: Adrian Popa, Directors Office, Hughes Research Laboratories
Area of science: Engineering
ID: 897711856.Eg


Your questions address some of the key issues facing fuel cell designers 
and the questions will not be settled until a great deal of testing in an 
operational environment is conducted.

It is claimed that the major emissions from a gasoline powered fuel cell 
are carbon monoxide (CO) and carbon dioxide (CO^2). 

How much improvement will fuel cells offer relative to internal combustion 
engines has been studied on a small scale in laboratories with some 
promising results ; however, much testing will be required in the future. 

The following quotations present two different views on gasoline powered
fuel cells.

From the New York Times  


"The A.D. Little innovation, which was tested earlier this month, mixes 
oxygen with the gasoline fumes, breaking up the complex hydrocarbon 
molecules into H2 and carbon monoxide, which is a pollutant. 

If carbon monoxide exceeds about 40 parts per million, it will poison the 
fuel cell. To prevent such damage the new system includes a device built at 
the Los Alamos  National Laboratory, a nuclear weapons laboratory, that 
accepts the gas and adds a second oxygen atom to the carbon
monoxide, producing carbon dioxide. Engineers were able to accomplish that 
difficult step without adding oxygen to the H2, a step that would rob the 
fuel cell of its fuel. 

Then the gas, almost pure H2, goes to a fuel cell, an older technology that 
has been gradually improved in the last few years. The hydrogen atoms, 
which consist of one proton and one electron, flow down one side of a 
permeable membrane. On the other side is oxygen from air.
The hydrogen's proton wants to join with the oxygen, to create H2O, or 
water, and is drawn through the membrane, but the electron is left behind. 
With the positively charged proton on one side and the negatively charged 
electron on the other, the membrane creates an electrical difference that 
becomes a current. "
"In 16 hours of tests earlier this month at a Little laboratory in 
Cambridge, Mass., a processor ran smoothly on gasoline and ethanol, 
officials said. It produced enough hydrogen for 50 kilowatts,
big enough to run a medium-size car. Ethanol can be produced from corn, and 
the Energy Department hopes it will eventually be the main fuel for such 
cells. Gasoline might therefore be a transitional step to ethanol, which is 
completely renewable. 

The system delivers 84 percent of the energy in a gallon of gasoline to the 
fuel cell, said Jeffrey M. Bently, a vice president of Little, and the fuel 
cell turns most of that  energy into electricity. In contrast, an internal 
combustion engine loses more than 80 percent of the energy in a gallon,
either as heat out the tail pipe or friction in the drive train. "

"In this version, a team of researchers at Arthur D. Little Co., a Boston-
based energy consulting firm, came up with a fuel cell that produces energy 
by combining oxygen and hydrogen from gasoline.

The company said Tuesday it would work with major automakers to develop the 
system in an electric car, cutting auto emissions by 95 percent while 
doubling fuel efficiency. Officials estimated commercial production as 
early as 2005.

Some remaining challenges include reducing the cost, getting the system 
smaller to fit under a car's hood and developing more power than the 
laboratory model, company officials said. A spokesman for Chrysler Corp., 
which has worked with the research team, said costs would have
to be cut drastically for the engine to compete with current cars. Even 
mass produced, the technology would cost $30,000 per car now compared with 
$3,000 for conventional cars.

But, said Chrysler spokesman Tony Cervone, the automaker anticipates having 
a prototype car using the technology in less than two years and expects to 
cut costs enough to have commercial production before 2010.

The chemical reaction between oxygen and hydrogen produces energy and 
leaves only water. The extraction of hydrogen from gasoline leaves carbon 
dioxide, but because of increased efficiency carbon emissions would be cut 
by 50 to 70 percent from conventionally powered cars. The fuel
cell could produce cars that get up to 80 miles per gallon while cutting 
air pollution by 95 percent,the researchers said.


What the gasoline fuel cell doesn't do 


"It doesn't do much for the greenhouse effect. The end product of gasoline 
combusion is CO2, whether you burn the fuel in an engine, or chemically 
oxidize it to release hydrogen in a reformulator (the hydrogen is then fed 
to the fuel-cell directly or tanked for later use).
Combustion, by definition, uses up oxygen and releases CO2. What 
improvements in CO2 emissions comes about as a result of using an electric 
drivetrain. Don't think about sitting in a
closed garage with a running fuel-cell car with a gasoline reformulator on-
board. You may not die from the hydrocarbons or NOX, but you will still 

Fuel-cells are best used in a complete hydrogen energy cycle, which uses 
renewable solar or thermal energy sources to generate hydrogen from water 
without releasing CO2. Stored hydrogen then is used to drive hydrogen fuel-
cell EVs, which emit only water vapor. 

If we are going to use feul-cells. let's use the hudrogen ones. Even 
methanol isn't so bad, since it
can be produced from corn."
The process for electrically converting water (H2O) into hydrogen (H2) and 
oxygen (O2) gas has been studied for many years. One of the most promising 
techniques was by using a photovoltaic membrane process similar to solar 
cells; however, to date all of these processes have been very inefficient 
requiring far more energy input than fuel output. Also, the major costs for 
all forms of energy for use in transportation are for the fuel delivery 
system. Gasoline powered fuel cells will use a multi - billion dollar 
system that is already in place. The cost and environmental effects for 
creating a new fuel delivery system must be balanced with the environmental  
impact of the vehicle emissions.

Best regards, Your Mad Scientist

Adrian Popa

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