Skip to content

University Gazette

The University of North Carolina at Chapel Hill

Perfect timing brings final puzzle piece in Meyer’s solar energy mystery

meyer_tom_400For Tom Meyer, the solution to storing solar energy began 40 years ago in the mystery of a molecule.

“When molecules absorb light, they form excited states in which the electrons are rearranged and become more accessible,” he said. “The key was to take advantage because, at that point, with light absorption, energy conversion has occurred with the sun’s energy stored in the molecule.”

Though it was just one piece of information Meyer would need to uncover in the coming years, it was this insight into basic chemistry that eventually brought about what might become a significant breakthrough in solar energy: the ability to harness the sun’s energy for use even after it sets by converting its energy into fuels.

“You have an idea like this and then you go into the lab and try it out,” said, Meyer, Arey Distinguished Professor of Chemistry. “In this case, it actually worked.” (See here for more on the science behind the breakthrough.)

‘It’s all about timing’

Shortly after he arrived at Carolina in 1968, Meyer began collecting clues in pursuit of a mystery: how to mimic natural photosynthesis in converting and storing the sun’s energy as fuel.

That’s a long time to follow a thread, but Meyer was patient.

Key members of the research group had come and gone, and so had funding. Each step of the scientific process brought another piece to the puzzle. But, finally, with UNC’s Energy Frontier Research Center and a partnership with a group at N.C. State, “the talents we needed all fell into place.”

11 solar_fuel.jpg

Meyer’s new system generates hydrogen fuel by using the sun’s energy to split water into its component parts. After the split, hydrogen is stored, while the byproduct, oxygen, is released into the air. (Credit: Yan Liang, L2Molecule.com)

They had figured out light absorption, water oxidation and how to make molecules that split water and separate the electrons needed to generate hydrogen fuel. But the electrons couldn’t be freed quickly enough. Meyer wanted to try a “core-shell technique” with a thin coating of titanium dioxide on the outside of a conducting material that would allow the electrons to move more rapidly and allow time to strip electrons and protons from water to make oxygen.

To refine this technique, the Parsons group at N.C. State had something the Carolina group did not: the machine to make the layers Meyer needed to create the core-shell coating for the reactive molecules.

“All these pieces had to be in place, and without them, and without that capability, we couldn’t have done it,” he explained.

Meyer is a big believer in the right team: with chemists, physicists and materials scientists involved, difficult research problems can be addressed quickly with access to a broad spectrum of capabilities. Teamwork brings together scientists who create new materials with those who measure properties and those who make the devices to integrate it all.

It’s an object lesson in how to use the strengths of basic science to improve things and make changes rapidly, Meyer said. “That’s at the heart and soul of all this: if you can’t integrate and respond quickly, you’re not in the game.”

It’s all about timing, Meyer said. With the last piece of the puzzle in place, the team began repeatedly to produce the reaction they were looking for – they had made it happen.

“There was a feeling of, at last!” he said.

The rise of energy awareness

In the 1970s when Meyer was beginning to contemplate this idea, the nation faced a crisis that brought the idea of alternative energy into focus.

In 1973 during the Arab-Israeli war, Arab members of OPEC (Organization of Petroleum Exporting Countries) placed an oil embargo on the U.S. and other countries. The price of oil skyrocketed, a nation dependent on foreign oil experienced gasoline rationing and people began to think more about energy conservation.

“It wasn’t that big a deal until the oil embargo, and then it occurred to people to start thinking about energy security,” Meyer said. “There was a growing interest in energy issues right around the time our initial observations were made. Then, all of a sudden, the embargo was lifted and oil prices went down.”

The conversations stalled. Funding, again, became scarce.

When Meyer looks back at the projects he was undertaking during those years, he notes that many were pieces of the larger problem. When solved individually, they would allow him to crack the big one. He just didn’t know exactly how or when at the time.

“I had an effort in water oxidation, one in molecular assemblies and one in photochemistry. All needed to be brought together to guide the way toward solving the larger problem,” he said.

Solar energy as a dominant source of energy is making inroads and it will be more popular as it becomes more economically sound, Meyer said.

Currently the cost of devices that convert solar energy into electricity is decreasing while the price of energy continues to rise. Countries with low energy resources will become increasingly interested in using the sun and how to store solar energy and make it a viable, everyday source of power on the short term, Meyer said.

“Being able to use the sun’s ability to provide energy on demand is especially appealing in places where energy supplies are short,” he explained.

And it might become more appealing in the U.S., too.

Natural gas is a hydrocarbon gas mixture that is not a renewable resource, but is in great abundance in the U.S. One of the main ways these gasses are extracted is by hydraulic fracturing (fracking), in which rocks below the earth’s surface are fractured and widened to release the hydrocarbons.

It’s a practice that has both detractors and supporters. There is the additional issue that burning hydrocarbons produces greenhouse gases.

“In the long term, if the environmental issues that people are raising are real, we’re going to have to use the sun,” Meyer said. “You’ve got a technology that’s there and a sun that continues to become more efficient price-wise. So, the drivers are there to keep this alive.”

From basic science to marketplace

Forty years ago, Meyer knew there had to be a way to make his idea work.

“I intuited that we should be able to figure it out. We followed our noses and improved this over time, but the outline was there from the very beginning,” he said.

He feels the same way about translating this basic science, an idea planted long ago that’s finally come to fruition, to the marketplace.

“What we do here, the thing we do best, we’ll continue to do: that is to refine this and make it better,” Meyer said.

“But we’re also looking for the way to translate these findings into a new energy technology. It’s the interplay between those two where this will really pay off.”