Piezo Crystals: Harnessing Sound Waves to Generate Fuel?

Scientists at the University of Wisconsin-Madison [2] may have discovered a new, somewhat strange way to efficiently produce hydrogen fuel without the need for "dirty" catalysts like oil.

The new ingredients: water submersion and noise pollution.

The team has made piezoelectric crystals of zinc oxide [3] that, when immersed in water, absorb vibrations and develop areas of strong negative and positive charge. These charges rip apart nearby water molecules, releasing hydrogen and oxygen gas.

"This is like a free lunch," says lead researcher Huifang Xu [4]. "You are getting energy from the environment just like solar cells capture energy from the sun."

Hydrogen fuel being the greenest around, but sadly void of any efficient means of extraction.

What The Heck Are Piezoelectric Crystals?

Piezoelectricity is the ability of some materials (notably crystals and certain ceramics, including bone) to generate an electric field or electric potential in response to applied mechanical stress.

The effect is closely related to a change of polarization density within the material's volume. If the material is not short-circuited, the applied stress induces a voltage across the material.

The word is derived from the Greek piezo or piezein, which means to squeeze or press.

What Makes These New Crystals Different?

Xu and colleagues generate hydrogen using a new variation on piezoelectric crystals.

The new crystals are designed to be submerged, so the charge they generate instead pulls apart water molecules to release hydrogen and oxygen gas, a mechanism Xu's team calls the piezoelectrochemical effect [5].

By submerging a new type of zinc oxide crystal in water, the scientists claim to be able to harvest hydrogen using vibrations from passing traffic and crashing waves.

And Just How Efficient Is This Process?

Well, it's better than the old way, but not necessarily a home run. Xu says that lab tests suggested the material can convert 18 per cent of the energy it absorbs from vibration into energy locked up in hydrogen gas, which can be released by burning.

Conventional piezoelectric materials are not as efficient at converting vibrations into electricity, and typically achieve around a 10 percent conversion rate.

Something new and cool under the sun, which just might cause a momentary consideration for the unbearable noise of morning traffic.

Sources: New Scientist [6] and Inhabitat [7]