Table of Contents

1. HOW DOES THIS REPRESENT AN ENERGY SOURCE?
2. HOW CAN SULFUR BE USED TO GENERATE HYDROGEN?
3. WHAT IS THE COST PER LITER OF SULFUR GENERATED HYDROGEN?
4. WHERE WILL WE GET THE ALUMINUM FOR THIS REACTION?
5. WHERE WILL WE ENOUGH THE SULFUR?
6. DOESN'T SULFUR GIVE OFF ENVIRONMENTALLY HARMFUL GASSES AND SMELL LIKE ROTTEN EGGS?
7. WHY IS SULFUR GENERATED HYDROGEN BETTER THAN RENEWABLE ALTERNATIVES LIKE BIODIESEL ALGAE OR CELLULOSTIC ETHONOL?
8. WHY SHOULD WE CONVERT ELECTRICITY INTO HYDROGEN WHEN IT'S MORE EFFICIENT TO SIMPLY USE THE ELECTRICITY?

Answers

1. HOW DOES THIS REPRESENT AN ENERGY SOURCE?
   
   When considering possible energy sources, it is important to understand that we cannot "make" energy. We only harvest energy from existing sources. For example, a solar panel harvests the energy produced by the sun. As another example, coal and oil represent the stored energy of millions of years of sunlight which we pull from the ground and burn. Where a chemical reaction is used to harvest energy, as in burning oil, molecules having a relatively high energy state are recombined to create molecules having a lower energy state. In going from the higher to the lower energy state, the atoms within these molecules release energy. For example, when we burn natural gas, we are combining three molecules of natural gas, (3CH4), with three molecule of oxygen, (3O2), to get three molecules carbon dioxide (3CO2) and 6 molecules of water (6H2O). Because the natural gas and the oxygen molecules are at a higher energy state than the carbon dioxide and water molecules, this reaction gives off energy in the form of heat. This principle applies to reactions involving sulfur as well. When we generate hydrogen using sulfur and aluminum, the aluminum and the sulfur are at a higher energy state than the aluminum sulfate product. Thus, the reaction harvests the energy inherent in the sulfur and the aluminum in the form of electricity current and hydrogen. The hydrogen is formed because the reaction splits the water in which it takes place into hydrogen and oxygen. The oxygen bonds to the aluminum and sulfur to form aluminum sulfate, and the hydrogen gas is liberated. [Back to the top]
    
2. HOW CAN SULFUR BE USED TO GENERATE HYDROGEN?
   
   To generate hydrogen from sulfur, we combine sulfur with aluminum in an electrochemical reaction using a liquid electrolyte (Na OH) to produce aluminum sulfate and hydrogen. The chemical equation is: 2Al + 3S + 12H2O * Al2(SO4)3 + 12 H2. [Back to the top]
    
3. WHAT IS THE COST PER LITER OF SULFUR GENERATED HYDROGEN?
   
   If it takes 20 kilowatt hours of electricity to recycle the aluminum necessary to generate 1 kilogram of hydrogen and we can buy the electricity at ten cents per kilowatt hour, the cost to refine the aluminum is $2.00. Sulfur historically trades for 50 to 100 dollars per ton. At 100 dollars per ton, one kilogram of sulfur costs ten cents. If the reaction requires 3 kilograms of sulfur to produce a kilogram of hydrogen, the cost of the sulfur would be 30 cents. Thus, the total cost for the materials is $2.30. [Back to the top]
    
4. WHERE WILL WE GET THE ALUMINUM FOR THIS REACTION?
   
   Aluminum does not exist in nature in a pure form. It generally occurs in the form of Aluminum oxide. In this form, it is at too low an energy state to be used as an energy source. Hence it must be refined into pure aluminum through the input of electrical energy to be used in the reaction. Therefore, the Aluminum in this reaction does not represent a fuel source, but rather is an energy storage medium and must be recycled after each use. In a sodium hydroxide electrolyte, the aluminum sulfate breaks down into aluminum oxide and sodium sulfate. The aluminum sulfate precipitates out and can be collected and recycled. It takes approximately 20 Kilowatt hours of electricity to refine aluminum oxide into 2 kilograms of pure aluminum. The sulfur/aluminum reaction uses approximately 2 kilograms of aluminum to generate one kilogram of hydrogen. One kilogram of hydrogen has the energy content of one gallon gasoline. One gallon of gasoline contains approximately 35 kilowatt hours of energy, or 134,200 Kilajoules. Hence this reaction gives us back the 20 kilowatt hours of energy we invested in the aluminum plus an addition 15 kilowatt hours of energy due to the energy contributed by the sulfur. If the energy used to refine the aluminum represents storage of excess electricity from windmills, this system then represents a combination of half renewable and half non renewable energy. Plus, because the products are hydrogen and electricity, this reaction produces nearly zero carbon emission. * [Back to the top]
    
5. WHERE WILL WE ENOUGH THE SULFUR?
   
   Sulfur exists in three general forms. The first form is as elemental sulfur. The world reserves of elemental sulfur deposits total approximately 5 billion tons. This form of sulfur has traditionally been mined using a process invented by Herman Frasch in the 19th century wherein steam is injected into the sulfur formation to melt it and the molten sulfur is then piped to the surface. If one ton of sulfur yields the energy equivalent of 8 barrels of oil, then the world's reserve of elemental sulfur would yield the energy equivalent of 40 billion barrels of oil. Clearly the reserves of elemental sulfur are not sufficient to satisfy the world's energy needs, although. used judiciously, they can make a contribution. Sulfur also exists as a sulfide. A sulfide is a molecule in which sulfur is bonded to another atom such as iron to form iron sulfide, zinc to form zinc sulfide or mercury to form mercury sulfide. The chemical formula for iron sulfide is FeS2. Iron sulfide has an enthalpy of -40 KJ per mole. In other words, it takes 40 KJ of energy to separate the two sulfur atoms from the iron atom. However, the product of the sulfur/aluminum reaction is a sulfate, with an enthalpy of -909KJ per mole. Thus, we invest 40 KJ to get one mole of sulfur, but get over 900 kilajoules back when we react the sulfur. The important point here is that sulfur bound to a mineral as a sulfide is at a much higher energy state than a sulfur bound as a sulfate. Hence, even when we factor in the entropy associated with separating the sulfur in its sulfide form, there still remains sufficient harvestable energy to make the overall energy gradient positive. In the sulfide form, the amount of sulfur contained in the earths surface dwarfs the supply of fossil fuels. For example, the oil shale of the Colorado Plateau region of the United States contains an estimated 600 billion tons of sulfur in this form. 600 billion tons of sulfur would yield the energy equivalent of 4.8 trillion barrels of oil. Sulfur also exists in organic sulfide form-i.e bound to carbon chains such as coal, natural gas and crude oil. Approximately 100 million tons of elemental sulfur is produced each year as the result of refining of oil and natural gas, with the majority of this going to industrial processes. Finally sulfur exists in sulfate form. Gypsum, for example is calcium sulfate. However, as explained in the paragraph above, sulfur in the sulfate form is in too low an energy state to be usable as a fuel in this reaction. [Back to the top]
    
6. DOESN'T SULFUR GIVE OFF ENVIRONMENTALLY HARMFUL GASSES AND SMELL LIKE ROTTEN EGGS?
   
   Sulfur is the 8th most common element on earth. Therefore, it is all around us. However, it generally occurs as a solid in the form of sulfides and sulfates. In solid form, sulfur does not smell or present a hazard. For example, gypsum, the white substance used in wall board is calcium sulfate. Aluminum sulfate is a useful industrial product. Iron Sulfide (fools gold) is a common occurring mineral. Only when it is in the form of a gas does sulfur present the smells and toxins with which people associate sulfur. In a solid form, sulfur is environmentally benign. In the aluminum/sulfur reaction, the solid sulfur is turned into a sulfate, another solid. The reaction initially produces aluminum sulfate. However, the sodium hydroxide electrolyte which drives the reaction, breaks down the aluminum oxide into sodium sulfate and aluminum hydroxide. Hence, no sulfur gas is released. The solid sodium sulfate can be disposed of in an environmentally benign manner. The aluminum oxide is refined back into aluminum. [Back to the top]
    
7. WHY IS SULFUR GENERATED HYDROGEN BETTER THAN RENEWABLE ALTERNATIVES LIKE BIODIESEL ALGAE OR CELLULOSTIC ETHONOL?
   
   Virtually all the renewable energy sources on the drawing board today, with the exception of wind and solar, are at least ten years away from being capable of implementation, even if they prove to be scalable. Unfortunately, we do not have ten years. Our problem is now. Sulfur generated hydrogen works, it's scalable, it's clean, and, because it is a relatively simple reaction, it can be implemented immediately. [Back to the top]
    
8. WHY SHOULD WE CONVERT ELECTRICITY INTO HYDROGEN WHEN IT'S MORE EFFICIENT TO SIMPLY USE THE ELECTRICITY?
   
   Because of the inherent efficiency of electricity, it makes sense to use electric energy whenever possible. However, because electricity cannot be stored unless it is converted into another energy form, a great deal of electric energy goes to waste, especially at night when demand is low. In addition, a windmill's generation of electricity is dictated by the speed of the wind, which varies over time. When the wind blows too hard, again electricity is wasted unless it can be stored. In fact, the inability to store electricity is often cited by those in the industry as the main barrier to their widespread adoption of alternatives such as electricity. Sulfur generated hydrogen represents a cost effective method for storing excess alternative energy in a method that allows 100% of the energy stored can be recovered. (remember, the energy contribution from the sulfur makes up for the entropy losses in converting the electricity into refined alumium) In addition, the wind often blows in areas far distant from where the energy is needed. Sulfur generated hydrogen represents a way to convert that electrical energy into a solid form that can then be readily transported through the world's existing infrastructure to generate energy where it is needed. Finally, sulfur generated hydrogen represents a way to convert electrical energy into a home heating and motor fuel. [Back to the top]