COOLING | ELECTROCALORIC REFRIGERATION MAKING A DIFFERENCE Electrocaloric cooling works by applying an electric field to change temperatures and requires no refrigerants. Metkel Yebiyo and Professor Andy Ford look at the benefits of the technology and the challenges of bringing it to market R efrigeration, air conditioning and heat pumps account for 19% of UK electricity demand and around 10% of total greenhouse gas (GHG) emissions. In 2015, the EU agreed to intensify reductions in carbon emissions between 2020 and 2030. This will include a further 40% reduction in GHGs, through much greater use of renewable technologies and a massive increase in energy efficiency. Several promising alternative, innovative heating and cooling technologies are under development, including elastocaloric, magnetocaloric, thermoelectric, barocaloric and electrocaloric. While the magnetocaloric effect has been studied extensively since its discovery by Emil Warburg in 1881 (see Magnetic attraction, CIBSE Journal, February 2016, bit.ly/CJJul19electro), electrocaloric cooling (EC) discussed in this article has had much less interest. It is, however, an emerging, innovative and potential low carbon technology. The first experimental measurement of the EC effect was reported in the early 1930s, but the scale was very small. This changed with the recent discovery of the giant EC effect. Since then, the practical application of EC heating and cooling has been subject to a lot of research, and commercial applications are now on the radar. Basic working principles The principle of EC cooling is based on the EC effect the ability of a material to change temperature when an electric field is applied. An EC device has two thin materials separated by a vacuum layer. Application of an electric field causes the most energetic electrons on the negative side to jump across to the positive side. As they leave the negative side, it gets colder. Figure 1 helps to demonstrate how to use this effect. Two types of materials are normally used for EC ceramics and polymers. Ceramics have more advantages because of their high breakdown field, higher electrocaloric efficiency, and larger cooling capacity.2 The main limitation of the EC system shown in Figure 1 is the relatively small temperature difference that can be achieved between the cold and hot source. A number of techniques have been used to increase this exchange, such as active caloric regenerative process. The principle of this cycle uses a heat-transfer fluid in contact with the EC materials flowing from the cold side to the hot side when the An electric field causes electrons to jump across to the positive side. As they leave the negative side, it gets colder www.cibsejournal.com July 2019 47 CIBSE July19 pp47-48 Electrocaloric cooling.indd 47 21/06/2019 14:51