Drawing On Science
by Stephen Yaeger
In his recent State of the Union speech, President Bush said, “America is addicted to oil…” and we must “change how we power our automobiles” by researching the production of ethanol and pollution free cars running on hydrogen. Reducing or ultimately eliminating our need for oil is something that must be done. It is not only a question of dealing with an unstable country or area, it is important to the health of the planet as far as pollution and global warning are concerned and we must remember that fossil fuels are non-renewable energy sources. A recent study has shown that a gallon of ethanol requires 95% less petroleum energy than producing a gallon of gas from fossil fuels. According to Daniel Kammen of the University of California, Berkeley, ethanol is more energy efficient than gasoline and fossil fuels, and is 95% free of greenhouse gas emissions.
What is ethanol and how is it produced? Ethanol or ethyl alcohol is an organic compound, and, as its name implies, it is an alcohol. It’s composed of carbon, hydrogen and oxygen having the chemical formula, C2H5OH. It is the most common of the alcohols. Ethanol is also called grain alcohol because it can be prepared from corn by a process called fermentation (=a chemical change brought about by enzymes). The starch in corn is first converted into a fermentable sugar. Enzymes are added and allowed to work on the sugar. Once the sugar has fermented the ethanol is removed by distillation (=evaporating a liquid in one container and condensing its vapor in another container). During prohibition, you may have learned (or remember) distillation was a no-no. But ethanol, as concerns us here, is for automobile consumption, not human consumption. So if ethanol is to be used in the place of gasoline, it must be denatured (=making it unfit for drinking). This is accomplished by adding methanol or wood alcohol, which is poisonous. Ethanol produced from cellulose and lignin , substances found in woody, fibrous plants such as willows, rice stalks and switch grass has been found to be even more energy efficient. It is also cleaner burning and costs half the price of gasoline.
In the United States about five million cars and trucks are flex-fuel vehicles. No, it has nothing to do with muscles. Flex-fuel vehicles can run on either traditional gasoline fuels or a fuel known as E85. E85 is a mix of 85% ethanol and 15% gasoline. Flex-fuel cars and trucks have a yellow fuel cap. An automobile can be converted to run on flex-fuel for about $100.00. Right now, however, there are not many pumps in the US, which are dispensing ethanol fuel. Brazil has already converted just about all of its cars and pumps to run on and dispense ethanol, which they produce from sugarcane. Keep in mind that Brazil accomplished this feat in some 25 years. With the technology today the US can do it in much less time…if it is willing.
A hydrogen fuel cell is similar to a battery. By breaking down and combining chemical components energy is produced. This energy can then be used to power any electrical device or automobile. Basically what you have are two electrodes : a cathode or positive electrode and an anode or negative electrode. The electrodes are separated from each other by an electrolyte , consisting of platinum powder acting as a catalyst. The powder coats the electrode facing surfaces of a proton exchange membrane (PEM) through which protons or positively charged ions pass.
OK, so how does it work?
Here it comes.
Ready? Read slowly and follow the diagram. Oxygen and hydrogen gases are fed to a reservoir where, with pressure they are forced through the catalyst. Hydrogen gas, H2, is oxidized (=loses electrons) at the anode forming two hydrogen (H+) ions and two electrons (e-). The positively charged H+ ions pass through the PEM to the cathode, and the electrons are conducted through an external circuit to power an electric motor then they travel to the cathode.
On the cathode side of the fuel cell, oxygen gas, O 2, is being forced through the catalyst also where the molecules split, forming two oxygen atoms. When hydrogen ions reach the cathode they are reduced (=gain electrons) by combining with two electrons to form two hydrogen atoms. Ok so far?
Now, all atoms have an attractive force for the electrons of other atoms; this is known as electronegativity . Oxygen atoms have a relatively high electronegativity, whereas hydrogen atoms have a low electronegativity. So, what happens? Well two hydrogen atoms are attracted to an oxygen atom where they all combine to form a water molecule, H2O, which completes the process. If you are still following this here are the chemical reactions: Reaction at the anode: 2H 2 ? 4H+ + 4e-; Reaction at the cathode: O2 + 4H+ + 4e- ? 2H2O; Overall reaction: 2H2 + O2 ? 2H2O.
So now you understand the chemis-try, right? And, yes, there are mil-lions of electrons, protons and atoms playing a part in this so, obviously, a whole bunch of liquid water is the re-sult of the process; not just two mole-cules of water. Think of it…no carbon monoxide is exhausted to pollute the air, just clean, non-pollutant water is the waste product!
Keep in mind also that the voltage resulting from a single fuel cell is quite low; about 0.7 volts. So to raise the voltage a number of cells are combined to form a fuel-cell stack.
Next month Alternative Source of EnergyII.
Questions? E-mail Steve:
Alternative Sources Of Energy, Part I