Making Fuel from the Sun

Could the sun's rays one day make the gasoline to power your car? Scientists who gathered at ICTP's workshop on "Materials Challenges in Devices for Fuel Solar Production and Employment" from 19-23 May are studying and designing materials to convert sunlight into chemical fuel.

Currently, renewable energy sources like the sun and wind can be converted directly into electricity, but there isn't a good way to use the energy at another time or place. That limits how much of the sun's energy can actually be consumed.

"This is why this workshop is important," said Ralph Gebauer who organized this event together with Nicola Seriani from ICTP. "We are trying to solve the big issue of storage and transportation."

One way to tackle these problems would be to convert the sun's energy into the chemical bonds that hold together more familiar hydrocarbon fuels like gasoline and methane.  These fuels are both easily transportable and ready for immediate use in devices like cars.

Hydrocarbon fuels are composed of three ingredients:  hydrogen, carbon, and the energy that holds them together.  In so-called "solar fuels," the sun provides the energy and water can provide the hydrogen.  The carbon would come from the most notorious of greenhouse gases:  what Gebauer called "the famous CO₂" (carbon dioxide).

"The idea is to use the CO₂ (produced from burning fuels) instead of dumping it into the environment...to basically use it as a feedstock to make the fuels," Gebauer explained.

Michele Aresta, from the University of Bari, Italy, was one of the invited speakers who lectured about how to use the CO₂ in this way.  For Aresta, the work of the researchers at the conference could be especially critical for those with the greatest access to solar energy.  "Often the countries that are the richest in solar energy are the poorest in technology.  So they depend on richer countries for technology," he said.

Richard Catlow of the University College of London, who presented computational methods to study the fuel storage capacity of new materials, agreed.  "I think it's particularly important for developing countries because a lot of them have very appropriate conditions for using solar energy," he said.  "But we all need (these technologies)."

It costs more to develop fuels from renewable energy compared to traditional sources, according to Gebauer, so solar fuels aren't yet widely available.  Both the conference attendees and Gebauer's renewable energy research group at ICTP hope to change that.  "That's why we need research to make processes of obtaining renewable fuels more efficient," Gebauer said.