Future Energy eNews IntegrityResearchInstitute.org May 21, 2007
Purdue researchers demonstrate their method for producing hydrogen by adding water to an alloy of aluminum and gallium. The hydrogen could then be used to run an internal combustion engine. The reaction was discovered by Jerry Woodall, center, a distinguished professor of electrical and computer engineering. Charles Allen, holding test tube, and Jeffrey Ziebarth, both doctoral students in the School of Electrical and Computer Engineering, are working with Woodall to perfect the process. (Purdue News Service photo/David Umberger)
A Purdue University engineer has developed a method that uses an aluminum alloy to extract hydrogen from water for running fuel cells or internal combustion engines, and the technique could be used to replace gasoline.
The method makes it unnecessary to store or transport hydrogen - two major challenges in creating a hydrogen economy, said Jerry Woodall, a distinguished professor of electrical and computer engineering at Purdue who invented the process.
"The hydrogen is generated on demand, so you only produce as much as you need when you need it," said Woodall, who presented research findings detailing how the system works during a recent energy symposium at Purdue.
The technology could be used to drive small internal combustion engines in various applications, including portable emergency generators, lawn mowers and chain saws. The process could, in theory, also be used to replace gasoline for cars and trucks, he said.
Hydrogen is generated spontaneously when water is added to pellets of the alloy, which is made of aluminum and a metal called gallium. The researchers have shown how hydrogen is produced when water is added to a small tank containing the pellets. Hydrogen produced in such a system could be fed directly to an engine, such as those on lawn mowers.
"When water is added to the pellets, the aluminum in the solid alloy reacts because it has a strong attraction to the oxygen in the water," Woodall said.
This reaction splits the oxygen and hydrogen contained in water, releasing hydrogen in the process.
The gallium is critical to the process because it hinders the formation of a skin normally created on aluminum's surface after oxidation. This skin usually prevents oxygen from reacting with aluminum, acting as a barrier. Preventing the skin's formation allows the reaction to continue until all of the aluminum is used.
The Purdue Research Foundation holds title to the primary patent, which has been filed with the U.S. Patent and Trademark Office and is pending. An Indiana startup company, AlGalCo LLC., has received a license for the exclusive right to commercialize the process.
The research has been supported by the Energy Center at Purdue's Discovery Park, the university's hub for interdisciplinary research.
"This is exactly the kind of project that suits Discovery Park. It's exciting science that has great potential to be commercialized," said Jay Gore, associate dean of engineering for research, the Energy Center's interim director and the Vincent P. Reilly Professor of Mechanical Engineering.
The research team is made up of electrical, mechanical, chemical and aeronautical engineers, including doctoral students.
Woodall discovered that liquid alloys of aluminum and gallium spontaneously produce hydrogen if mixed with water while he was working as a researcher in the semiconductor industry in 1967. The research, which focused on developing new semiconductors for computers and electronics, led to advances in optical-fiber communications and light-emitting diodes, making them practical for everything from DVD players to automotive dashboard displays. That work also led to development of advanced transistors for cell phones and components in solar cells powering space modules like those used on the Mars rover, earning Woodall the 2001 National Medal of Technology from President George W. Bush.
"I was cleaning a crucible containing liquid alloys of gallium and aluminum," Woodall said. "When I added water to this alloy - talk about a discovery - there was a violent poof. I went to my office and worked out the reaction in a couple of hours to figure out what had happened. When aluminum atoms in the liquid alloy come into contact with water, they react, splitting the water and producing hydrogen and aluminum oxide.
"Gallium is critical because it melts at low temperature and readily dissolves aluminum, and it renders the aluminum in the solid pellets reactive with water. This was a totally surprising discovery, since it is well known that pure solid aluminum does not readily react with water."
The waste products are gallium and aluminum oxide, also called alumina. Combusting hydrogen in an engine produces only water as waste.
"No toxic fumes are produced," Woodall said. "It's important to note that the gallium doesn't react, so it doesn't get used up and can be recycled over and over again. The reason this is so important is because gallium is currently a lot more expensive than aluminum. Hopefully, if this process is widely adopted, the gallium industry will respond by producing large quantities of the low-grade gallium required for our process. Currently, nearly all gallium is of high purity and used almost exclusively by the semiconductor industry."
Woodall said that because the technology makes it possible to use hydrogen instead of gasoline to run internal combustion engines it could be used for cars and trucks. In order for the technology to be economically competitive with gasoline, however, the cost of recycling aluminum oxide must be reduced, he said.
"Right now it costs more than $1 a pound to buy aluminum, and, at that price, you can't deliver a product at the equivalent of $3 per gallon of gasoline," Woodall said.
However, the cost of aluminum could be reduced by recycling it from the alumina using a process called fused salt electrolysis. The aluminum could be produced at competitive prices if the recycling process were carried out with electricity generated by a nuclear power plant or windmills. Because the electricity would not need to be distributed on the power grid, it would be less costly than power produced by plants connected to the grid, and the generators could be located in remote locations, which would be particularly important for a nuclear reactor to ease political and social concerns, Woodall said.
"The cost of making on-site electricity is much lower if you don't have to distribute it," Woodall said.
The approach could enable the United States to replace gasoline for transportation purposes, reducing pollution and the nation's dependence on foreign oil. If hydrogen fuel cells are perfected for cars and trucks in the future, the same hydrogen-producing method could be used to power them, he said.
"We call this the aluminum-enabling hydrogen economy," Woodall said. "It's a simple matter to convert ordinary internal combustion engines to run on hydrogen. All you have to do is replace the gasoline fuel injector with a hydrogen injector."
Even at the current cost of aluminum, however, the method would be economically competitive with gasoline if the hydrogen were used to run future fuel cells.
"Using pure hydrogen, fuel cell systems run at an overall efficiency of 75 percent, compared to 40 percent using hydrogen extracted from fossil fuels and with 25 percent for internal combustion engines," Woodall said. "Therefore, when and if fuel cells become economically viable, our method would compete with gasoline at $3 per gallon even if aluminum costs more than a dollar per pound."
The hydrogen-generating technology paired with advanced fuel cells also represents a potential future method for replacing lead-acid batteries in applications such as golf carts, electric wheel chairs and hybrid cars, he said.
The technology underscores aluminum's value for energy production.
"Most people don't realize how energy intensive aluminum is," Woodall said. "For every pound of aluminum you get more than two kilowatt hours of energy in the form of hydrogen combustion and more than two kilowatt hours of heat from the reaction of aluminum with water. A midsize car with a full tank of aluminum-gallium pellets, which amounts to about 350 pounds of aluminum, could take a 350-mile trip and it would cost $60, assuming the alumina is converted back to aluminum on-site at a nuclear power plant.
"How does this compare with conventional technology? Well, if I put gasoline in a tank, I get six kilowatt hours per pound, or about two and a half times the energy than I get for a pound of aluminum. So I need about two and a half times the weight of aluminum to get the same energy output, but I eliminate gasoline entirely, and I am using a resource that is cheap and abundant in the United States. If only the energy of the generated hydrogen is used, then the aluminum-gallium alloy would require about the same space as a tank of gasoline, so no extra room would be needed, and the added weight would be the equivalent of an extra passenger, albeit a pretty large extra passenger."
The concept could eliminate major hurdles related to developing a hydrogen economy. Replacing gasoline with hydrogen for transportation purposes would require the production of huge quantities of hydrogen, and the hydrogen gas would then have to be transported to filling stations. Transporting hydrogen is expensive because it is a "non-ideal gas," meaning storage tanks contain less hydrogen than other gases.
"If I can economically make hydrogen on demand, however, I don't have to store and transport it, which solves a significant problem," Woodall said.
Source: Purdue University
4) NASA - The Equivalence Principle
NASA Headlines, Science@NASA, May 18, 2007,
Standing on the Moon in 1971, Apollo 15 astronaut Dave Scott held his hands out at shoulder height, a hammer in one hand and a feather in the other. And as the world looked on via live television, he let go.
It was an odd sight: the feather didn't drift to the ground, it plummeted, falling just as fast as the hammer. Without air resistance to slow the feather, the two objects hit moondust at the same instant.
"What do you know!" exclaimed Scott. "Mr. Galileo was right."
Scott was referring to a famous experiment of the 16th century. Depending on who tells the story, Galileo Galilei either dropped balls from the top of the Leaning Tower of Pisa or he rolled balls down slopes at home. Either way, the result was the same: Although the balls were made of different materials, they all reached bottom at the same time.
Today, this is known as "the equivalence principle." Gravity accelerates all objects equally regardless of their masses or the materials from which they are made. It's a cornerstone of modern physics.
But what if the equivalence principle (EP) is wrong?
Galileo's experiments were only accurate to about 1%, leaving room for doubt, and skeptical physicists have been "testing EP" ever since. The best modern limits, based on, e.g., laser ranging of the Moon to measure how fast it falls around Earth, show that EP holds within a few parts in a trillion (1012). This is fantastically accurate, yet the possibility remains that the equivalence principle could fail at some more subtle level.
"It's a possibility we must investigate," says physicist Clifford Will of Washington University in St. Louis, Missouri. "Discovering even the slightest difference in how gravity acts on objects of different materials would have enormous implications."
In fact, it could provide the first real evidence for string theory. String theory elegantly explains fundamental particles as different vibrations of infinitesimal strings, and in doing so solves many lingering problems of modern physics. But string theory is highly controversial, in part because most of its predictions are virtually impossible to verify with experiments. If it's not testable, it's not science.
"Some variants of string theory predict the existence of a very weak force that would make gravity slightly different depending on an object's composition," says Will. "Finding a variation in gravity for different materials wouldn't immediately prove that string theory is correct, but it would give the theory a dose of supporting evidence."
Modern tests of the Equivalence Principle.
Figure based on a similar diagram in a review article from Physics World. http://physicsweb.org/articles/world/18/1/5/1/PWrel3_01-05
This new facet of gravity, if it exists, would be so astonishingly weak that detecting it is a tremendous challenge. Gravity itself is a relatively weak force—it's a trillion trillion trillion (1036) times more feeble than electromagnetism. Theorists believe the new force would be at least ten million million (1013) times weaker than gravity.
Just as magnetism acts on objects made of iron but not plastic, the new force wouldn't affect all matter equally. The force's pull would vary depending on what the object is made of.
For example, some versions of string theory suggest that this new force would interact with the electromagnetic energy contained in a material. Two atoms that have the same mass can contain different amounts of electromagnetic energy if, say, one has more protons, which have an electric charge, while the other has more neutrons, which have no charge. Traditional gravity would pull on both of these atoms equally, but if gravity includes this new force, the pull on these two atoms would differ ever so slightly.
No experiment to date has detected this tiny difference. But now three groups of scientists are proposing space-borne missions that would hunt for this effect with greater sensitivity than ever before.
"What you want to do is take two test masses made of different materials and watch for very small differences in how fast they fall," Will says. "On Earth, an object can only fall for a short time before it hits the ground. But an object in orbit is literally falling around the Earth, so it can fall continuously for a long time." Tiny differences in the pull of gravity would accumulate over time, perhaps growing large enough to be detectable.
One test mission, called the Satellite Test of the Equivalence Principle (STEP), is being developed by Stanford University and an international team of collaborators. STEP would be able to detect a deviation in the equivalence principle as small as one part in a million trillion (1018). That's 100,000 times more sensitive than the current best measurement.
Concept of STEP in orbit: http://einstein.stanford.edu/STEP/
STEP's design uses four pairs of test masses instead of just one pair. The redundancy is to ensure that any difference seen in how the test masses fall is truly caused by a violation of the equivalence principle, and not by some other disturbance or imperfection in the hardware.
"When trying to measure such a miniscule effect, you have to eliminate as many external disturbances as possible," Will explains. STEP's design places the test masses inside a large tank of liquid helium to insulate them from external temperature fluctuations, and surrounds the masses with a superconducting shell to shield them from magnetic and electrical interference. Microthrusters counteract the effects of atmospheric drag on the orbiting satellite, making the free fall of the test masses nearly perfect.
In this pristine environment, each pair of test masses should stay perfectly aligned with each other as they fall around the Earth—that is, if the equivalence principle holds. But if this new component of gravity does exist, one test mass will fall at a slightly different rate than its partner, so the pair will drift slightly out of alignment over time.
Currently, STEP is still in the design phase. Another satellite-based experiment, the French-developed Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence (MICROSCOPE), is scheduled to launch in 2010. MICROSCOPE will have two pairs of test masses instead of four, and will be able to detect a violation of the equivalence principle as small as one part in a million billion (1015).
The third experiment is the Italian satellite Galileo Galilei ("GG" for short), which will operate in much the same way as STEP and MICROSCOPE, except that it uses only one pair of test masses. To improve its accuracy, the Galileo Galilei satellite will spin about its central axis at a rate of 2 rotations per second. That way, any disturbances within the spacecraft will pull in all directions equally, thus canceling themselves out. The experiment should be able to achieve a sensitivity of one part in a hundred million billion (1017).
Whether any of these missions stand a chance of detecting a violation of the equivalence principle is hard to say. Will says that he expects the experiments won't find any deviation, in part because finding one would be such a major revolution for modern physics. And string theory makes a range of predictions about how strong this new force would be, so it's possible that the effect would be too small for even these space-borne instruments to detect.
Finding no deviation would still be helpful: it would rule out some variants of string theory, inching physicists toward the correct "Theory of Everything." But finding a deviation, however small, would be a giant leap.
For More Information
Note: The equivalence principle discussed in this story is now referred to by physicists as the "weak equivalence principle" or WEP for short.
In 1907, Einstein formulated a more comprehensive strong equivalence principle (SEP) for his General Theory of Relativity. The WEP is a subset of the SEP.
The home page of Clifford M. Will -- professor of physics at the University of Washington; President of the International Society on General Relativity and Gravitation; member of the National Academy of Sciences.
The legend of the leaning tower -- Historians are not sure if Galileo ever carried out experiments at the Leaning Tower of Pisa. So why, asks Robert P Crease, has the story become part of physics folklore?
Tests of the Weak Equivalence Principle (PhysicsWorld)
The Eöt-Wash Group: Laboratory Tests of Gravitational and sub-Gravitational Physics -- learn more about recent laboratory tests of the Equivalence Principle
NASA's Future: The Vision for Space Exploration
5) Supplying the World's Energy Needs with Light and Water
Kevin Bullis, Technology Review, May 18, 2007 http://www.technologyreview.com/Energy/18707/
A leading chemist says that a better understanding of photosynthesis could lead to cheap ways to store solar energy as chemical fuel.
While researchers and technologists around the world scramble to find cleaner sources of energy, some chemists are turning to nature's own elegant solution: photosynthesis. In photosynthesis, green plants use the energy in sunlight to break down water and carbon dioxide. By manipulating electrons and hydrogen, oxygen, and carbon atoms in a series of complex chemical reactions, the process ultimately produces the cellulose and lignin that form the structure of the plant, as well as stored energy in the form of sugar. Understanding how this process works, thinks Daniel Nocera, professor of chemistry at MIT, could lead to ways to produce and store solar energy in forms that are practical for powering cars and providing electricity even when the sun isn't shining.
What's needed are breakthroughs in our understanding of the fundamental chemical processes that make photosynthesis possible, according to Nocera, a recognized photosynthesis expert. He is studying the principles behind photosynthesis and applying what he learns to making catalysts that use solar energy to create hydrogen gas for fuel cells. Nocera's goal: a world powered by light and water.
Technology Review: What's the biggest challenge related to energy right now?
Daniel Nocera: The real challenge with energy is the scaling problem. We're going to have this huge energy need, and when you start looking at all the numbers, there's only one supply that has scale, and it's the sun. But it's still a research problem. Technologies all follow lines; then there's a discovery and a new line that's better. We're on a very predictable line now in solar. Most things you hear about are incremental advances.
TR: You're studying photosynthesis to get ideas for how to convert sunlight into a chemical fuel--hydrogen--for use when the sun isn't shining or in powering fuel-cell vehicles.
DN: You can use the electricity directly when the sun is out, in places that have sun. [But] you need storage. There's absolutely no way around it. I am distilling the essence of photosynthesis down to be able to use it.
TR: Why is photosynthesis attractive in finding a source of clean energy?
DN: [Photosynthesis] does three things. It captures sunlight, and [second,] it converts it into a wireless current--leaves are buzzing with electricity. And third, it does storage. It stores the converted light energy in chemical energy. And it uses that chemical energy for its life process, and then it stores a little.
It turns out [that] photosynthesis is one of the most efficient machines in the world for energy conversion. But it's not great for storing energy because that's not what [a plant] was built to do. It was built to live and grow and reproduce.
And so that's the approach we take. Can we now do what the leaf is doing artificially, which is the capture, conversion, and storage in chemical bonds? But my device doesn't have to live: it can take a lot more of that energy and put it into chemical bonds.
TR: And you've had some success putting what you've learned to use.
DN: We did make a compound that makes hydrogen using light. We have something that you can dissolve in solution, shine light on it, and hydrogen comes bubbling up. It didn't do it that efficiently. But it was a big advance because it had a lot of new concepts in there to show how you can use sunlight to make hydrogen.
TR: What are some of the research problems you're addressing that you hope can lead to a big step forward in solar?
DN: Something we've really been working hard at is [understanding] the design principles that photosynthesis operates off.
One is that when [photosynthesis] splits water into hydrogen and oxygen, it uses more than one electron. This current that's running is going one electron at a time. But then [the plant] stores them and uses four electrons at once. We don't know how to do multi-electron reactions very well. We don't even have theories to describe them.
And then you have to manage protons--and that's what biology does really well. It takes electrical current and then it converts it to a chemical current, and the thing conducting the chemical current is protons. And then it sends atoms. What a photovoltaic does is send electrons to a point. Photosynthesis actually sends not an electron but an atom. And that's even a tougher thing to do because atoms are so much heavier than electrons. So we've gotten down deep into understanding, how do you move atoms [such as hydrogen atoms] around from point A to B so that they can join up with each other? How do you assemble them so they can unite?
TR: You've written that chemistry "will likely play the most central role of all the sciences" in addressing energy problems. How would you summarize the role of chemistry?
DN: For game changers, it's really easy. There's three.
Make photovoltaics cheap, which is a lot of chemistry. It's inventing new materials to make PV cheap.
Replace noble metals--things like platinum--with abundant metals. Because there's not enough stuff. When you're talking about this much scale, you better be using things like iron and manganese. You better look at your book that says what are the most abundant elements on the face of the earth.
TR: And this is for fuel cells, and also for photovoltaics.
DN: Photovoltaics--everything. That's the real technology issue that you have to keep in your mind. Not something that's so great, it's 100 percent efficient--and oh, by the way, I'm using ruthenium. I can use ruthenium now to teach me a principle, but ruthenium's below iron [on the periodic table]. So I better figure out, how can I take everything I'm learning with ruthenium and apply it to iron?
TR: And the third game changer?
DN: Split water with light. You do those three things, and you have a full new energy economy. It's hard for me to say exactly what that technology will look like, because the science is missing. But at the beginning of the 1900s, we built an entire society based on a new energy system. And I believe, once solar is in place, with help from biofuel, with a little help from wind, we will invent our society again from a new energy source.