Researchers in the US are developing ferroelectric polymers for use in cooling applications such as refrigerators. The polymers, known as polarpolymers, exhibit temperature changes at room temperature under an electrical field. They include poly(vinylidene fluoride-trifluoroethylene) and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene). "This is the first step in the development of an electric field refrigeration unit," said Qiming Zhang, professor of electrical engineering at Pennsylvania State University (USA; www.psu.edu). "For the future, we can envisage a flat panel refrigerator. No more coils, no more compressors, just solid polymer with appropriate heat exchangers."

Most conventional cooling systems, such as refrigerators or air conditioners, rely on the change in density of gases at changing pressures to cool, and require energy-intensive compressors and heating coils. Zhang's approach uses the change from disorganised to organised that occurs in some polarpolymers when placed in an electric field. The electricity causes the molecules to become highly ordered, and the material gives off heat and cools down. When the electricity is turned off, the material reverts to its disordered state and absorbs heat. Zhang and colleagues at Pennsylvania State University reported in “Science” journal a change in temperature of the material of about 22.6 degrees Fahrenheit.

Repeated randomising and ordering of the material, combined with an appropriate heat exchanger, could provide a wide range of heating and cooling temperatures, they said. In addition to refrigerators and air conditioning units, the polarpolymers could be used in electronics applications to cool heating circuit boards, allowing closer packing and hence smaller devices. They could also be used to cool or heat clothing, for example to cool protective gear for fire-fighters or heat socks for law enforcement officers.