Shape-shifting chemical is key to new solar battery

Author: Alison Pearce Stevens / Source: Science News for Students

Kasper Moth-Poulsen shows off a solar collector — Kasper Moth-Poulsen shows off the solar collector his team used to test its liquid battery.

What powers the device you’re using? Electricity, obviously. But where did that come from? Two thirds of the electricity used in the United States comes from power plants fueled by fossil fuels — coal, oil or natural gas.

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Solar energy produces just 1.3 percent of the electricity. Yet energy from the sun could easily power our every need if it could be stored for use when the sun doesn’t shine (such as at night). Researchers in Sweden now think they might have a way to do just that.

As a chemical engineer, Kasper Moth-Poulsen uses chemistry and physics to design solutions to problems. He works at Chalmers University of Technology in Gothenburg, Sweden. He teamed up with other researchers in Sweden and Spain to tackle the problem of storing energy from the sun. Their solution: Store that energy inside the bonds of molecules that have been suspended in a liquid.

Molecules consist of two or more atoms. Those atoms share electrons through bonds that hold them together.

Different types of molecules have distinct 3-D shapes. For example, methane is shaped like a three-sided pyramid called a tetrahedron (Teh-tra-HE-drun). Other molecules have different shapes. Adding energy to a molecule can alter its shape. New bonds may now form between its atoms — ones that may hold different amounts of energy. When a molecule later absorbs energy, that energy can become trapped within those new bonds.

That’s the key to the new solar-energy battery.

Using bonds inside a molecule to store solar energy isn’t new. Moth-Poulsen’s group had been working on that for years. But the molecules it initially worked with contained a rare and pricey metal called ruthenium (Roo-THEE-nee-um). The researchers needed a less costly alternative.

For inspiration, they turned to work by other chemists. They soon found a promising candidate called norbornadiene (Nor-BORN-uh-DY-een). It is made mostly of carbon and hydrogen, atoms that are found in all living things. That means this molecule should be cheap and easy to make.