March 11, 2016

Here heat is stored as electricity

(March 11, 2016)  Researchers at the Laboratory for Organic Electronics at LiU, with Professor Xavier Crispin in the lead, have created a supercondenser that can be charged by the sun. It contains no expensive or hazardous materials, has patents pending, and it should be fully possible to manufacture it on an industrial scale.

In the future we could have a completely new type of energy storage, charged by heat energy – for example during the day when the sun shines, or by waste heat from an industrial process. The heat is converted to electricity, which can be stored until it is needed. The results have recently been published in the esteemed journal Energy Environmental Science.

Simply put, a supercondenser is energy storage: a type of battery that consists of an electrolyte of charged particles – ions – between two electrodes. The charge is stored next to the electrodes, most often in carbon nanotubes. One of the physical phenomena that the researchers make use of here is that if a supercapacitor is exposed to a temperature gradient – that is, one end is warm and the other cold – the ions rush towards the cold side and an electric current arises.

The thermoelectric effect is used to make electricity of heat; how much heat is converted to electricity depends both on which electrolyte is used and how great the temperature difference is.

For many years, researchers at the Laboratory for Organic Electronics have experimented with fluid electrolytes consisting of ions and conductive polymers. The positively-charged ions are small and quick, while the negatively-charged polymer molecules are large and heavy. When one end is heated and the other one cooled down, the small, quick ions rush towards the cold side while the heavy polymer chains stay where they are. Since they are ions, and not electrons, they stick to the metal electrodes. The charge that then arises is stored in carbon nanotubes next to the metal electrodes, and can be discharged whenever the electricity is needed.

journal reference >>