The results confirmed that the organic molecules could indeed be used to generate electricity from heat. Before they can be put to use, however, it will be important, Sales says, to design the molecules so that they arrange themselves between metal layers to make large-scale thermoelectric materials. What’s more, so far the efficiency is very low, the researchers say. To improve this, they are creating and testing new versions of the molecules.
“These are very simple molecules that the group is looking at,” says J. Fraser Stoddart, professor of chemistry at the University of California, Los Angeles. He’s interested in the researchers’ plans to alter the molecules to improve their thermoelectric properties. “That’s where my heart starts to beat,” he says. “I hope they follow this research up.”
The research is only the first step, the researchers say, and, because much work remains, applications will be many years away.
If all goes well, though, so-called thermoelectric devices based on the molecules could prove to be an important source of power–and a way to reduce greenhouse-gas emissions by making far more efficient use of fossil fuel. “Ninety percent of the world’s electricity is generated by thermal-mechanical means,” says Arun Majumdar, professor of mechanical engineering at UC Berkeley and another researcher on the project. “And a lot of the heat is wasted. One and a half times the power that is generated is actually wasted.”
For example, a typical way to generate electricity is by heating up steam to drive a turbine. After the steam passes through the turbine, it still contains energy in the form of heat, although not enough to drive a turbine, Segalman says. That heat typically escapes into the atmosphere and is wasted. By wrapping thermoelectric materials around exhaust pipes, that heat could be put to work. In cars, thermoelectrics could replace the alternator and save hundreds of millions of gallons of gas a year, according to an estimate from a General Motors researcher. (See “Free Power for Cars.”)
Organic materials are appealing because they cost much less than thermoelectric inorganic materials: even if they are inefficient, they might still be economical. “These molecules are dirt cheap,” Majumdar says. “If the efficiency is low, that’s fine. You’re throwing that heat away anyway.”