Green Tech

Mention hydrogen and a legion of critics will outline the reasons why the gas will likely never be a major energy source.

But it doesn't mean that researchers still aren't working on these problems. And the latest idea comes from Rice University, where scientists have found that buckyballs-- molecular balls made up of 60 or more carbon atoms--can store hydrogen quite well.

The molecules can store around 8 percent of their weight in hydrogen at room temperature, Rice found. The federal government, meanwhile, has set a goal of finding materials that can store 6 percent of its weight in hydrogen.

The density of the hydrogen is about the same density that hydrogen would be held at the center of Jupiter.

"Based on our calculations, it appears that some buckyballs are capable of holding volumes of hydrogen so dense as to be almost metallic," said Boris Yakobson, professor of mechanical engineering and materials science at Rice, in a prepared statement.

An ability to store more hydrogen would likely translate into a longer driving range for hydrogen-powered forklifts or vehicles. Conceivably, the buckyballs could be reduced to a powder and sprinkled into a fuel tank: a chemical or physical agent could then be added to release the hydrogen at a steady rate from its carbon cage.

A decent storage medium is one of the chief challenges to hydrogen. Hydrogen can't be sent down ordinary pipelines--a lot of the gas could escape as well as damage the pipe. Compressing the gas and storing it in tanks takes energy and results in bulky storage. Many are experimenting with fixing the gas in metals. Metal prices, however, are escalating. Some others are working on ways to fix hydrogen in chemical powders.

Others are touting microbes and low-cost electrodes.

Hydrogen storage would also help buckyballs start to live up to their commercial promise. Discovered more than 20 years ago (through the work of now deceased Rice professor and Nobel winner Richard Smalley), buckyballs helped put nanotechnology on the map. Many thought the molecules would get adopted by industry. Instead, industry has largely gravitated toward the nanotube, which is a tube-shaped molecule made most of the time from carbon.

As a fuel source, hydrogen has some great characteristics. It's the most abundant element in the universe and in combustion engine it leaves water as a byproduct. Now, the problems: producing it requires electricity or large amounts of heat, production often results in ornate amounts of carbon dioxide, and the infrastructure of filling stations doesn't exist. Hydrogen car prototypes cost about a billion.

Still, advocates say you have to think big and futuristic. Naysayers have been wrong before and the interesting lab results can't be denied. The waste heat from nuclear plants could be harnessed to produce hydrogen. One idea being floated about is building a wave farm in the open ocean that would provide electricity for hydrogen production. The gas could then be compressed into a liquid in an undersea chamber.

Cheap, clean hydrogen is the holy grail in the green-technology world, and Nanoptek says it could have part of the answer.

The Maynard, Mass.-based company, which Wednesday announced that it has raised $4.7 million, has come up with a low-cost, durable titania electrode that can split water molecules into hydrogen and oxygen.

Sunlight hits the electrode, and the electrode splits the light into a positive charge (called a hole) and an electron. Before the two charges can rejoin, the electron gets captured by the electrode and then is exploited to split water. Silicon solar cells operate on the same principle.

Other companies have tried to use titania electrodes for this job in the past, but they broke down relatively rapidly, according to Nanoptek. The company's electrodes work better because, ironically, they are more brittle. The crystal lattice in the electrode is stressed, i.e. additional materials are added. (Semiconductor makers similarly stress their chips with germanium to create strained silicon, which improves performance.)

"This stretches the titania crystal lattice so that electrons (red areas in the image) are held less tightly in the lattice and so can be knocked out of the titania with (the) light of lower energy, meaning visible (light)," Nanoptek says.

A space 50 feet by 50 feet on a sunny roof could provide enough surface area for a Nanoptek hydrogen generator. This generator could, hypothetically, provide enough hydrogen to meet the driving needs of a family of four, the company says.

This electrode is stressed.

(Credit: Nanoptek)

Stanford University's Jim Swartz has identified a microbe that metabolizes sunlight and makes hydrogen and oxygen out of water. The problem, however, is that the microbe dies when oxygen levels rise. His team is working on genetically enhancing the organism. (Swartz also has a start-up called Fundamental Applied Biology that has raised $21 million.)

If Nanoptek's technology can move from the experimental stage, it could prove to be a boost for the hydrogen industry. Although hydrogen is the most abundant element in the universe, it's not fun to make.

Currently, most companies make it by combining methane with water and heating up the mix to 815 degrees Celsius. That takes a lot of energy, but it also produces . Whoops. Hence, critics like Joseph Romm assert that hydrogen cars actually pollute more than regular cars.

Some have said the energy for the cleaner water electrolysis process can be generated from the waste heat at nuclear power plants, but that solution requires nuclear plants, always a contentious issue. (Some have proposed building nuclear plants in India that can provide electricity and waste heat for running desalination plants.)

Another solution for cheap hydrogen could lay in metal alloy pellets that react with water to produce hydrogen. Purdue University, New York's Signa Chemistry and Ecotality are all working on this. Typically, the metals in the alloys come from the part of the periodic table that includes sodium.

And for you crazy people, some believe, years from now, that it might be possible to harness wave power to drive water electrolysis plants built far offshore. The hydrogen produced in these offshore plants would then be delivered by underground pipelines, which would compress it, further saving energy in the hydrogen distribution process. Who knows? It could actually work if enough pieces fall into place.

Toyota, BMW, and Ford all have active hydrogen car programs and hope to move beyond the experimental stage sometime in the second half of the next decade.

Although hydrogen is the most abundant element in the universe, it's a royal pain to make.

Most industrial hydrogen producers currently make the gas by heating methane and water to 815 degrees Celsius and causing a reaction. Unfortunately, this process generates 9.3 kilograms of carbon dioxide for every kilo of hydrogen, so it's not environmentally friendly or cheap.

Other companies like Signa Chemistry have come out with chemical catalysts that can strip hydrogen from water.

Then there is electrolysis, which involves cracking water molecules with electricity. Electrolysis doesn't produce any greenhouse gases or chemical residues so it's the most environmentally friendly. It's also expensive and time consuming. QuantumSphere says it has a way around this problem.

It has devised an iron-nickel power for coating an electrode that speeds up the electrolysis process, according to CEO Kevin Maloney. It's a classic nano play. Coating a surface with small, independent particles increases the reactive surface area, which means more simultaneous reactions between molecules. Quantum's Stingray electrodes have more than 2,000 times more catalytic surface area than standard electrodes coated with standard sized particles, he said.

The Stingray can produce 2.4 kilograms of hydrogen in 25 minutes. Standard electrodes can take hours or days, he said. As a result, the Stingray can produce hydrogen at $2.50 to $9 a kilo, not including subisidies. That's in the range that excites the Department of Energy.

No, the hydrogen economy doesn't exist yet. But researchers around the globe continue to ponder ways to produce, store and transport the stuff cheaply. Some car makers still maintain that hydrogen cars will come out within a decade or so.

A spin-out from Caltech, QuantumSphere also makes particles for rocket engines and other industrial applications. We wrote about them a few years ago here.