COOLING | ELECTROCALORIC REFRIGERATION CHALLENGES Step 1: Adiabatic polarisation. EC material heats up when electric field is applied n To improve and implement new manufacturing and processing methods for materials and regenerators n Lead-containing ferroelectric ceramics show great potential for EC Hot fluid out Step 2: Isoelectric enthalpic transfer, the heat is removed using heat transfer fluid Cold fluid in Step 3: Adiabatic depolarisation electric field is removed from EC material Cold fluid out Step 4: Isoelectric entropic transfer, EC material is cooler, absorbs heat from cooling load Cold fluid in Figure 1: Schematic showing basic working principle of electrocaloric refrigeration material is heated, and from the hot side to the cold side when the material is cooled down. This progressively increases the temperature difference between the cold and hot source to about 40K1, making the system potentially suitable for a range of commercial applications. One of the obstacles to achieving a sufficient EC effect is related to the exposure of the material to very high electric fields. Benefits EC cooling does not use refrigerant gas but, instead, a cooling fluid, which could be waterbased. As a result, there are no direct CO2 emissions and EC heat pumps comply fully with all regulations, such as F-Gas in Europe and EPA regulations in the US. Its advantage over magnetocaloric cooling is that the high electric fields required for refrigeration technologies, but they are not acceptable environmentally. With this in mind, more research on lead-free materials is required n Advances in materials that support the absorption of large amounts of heat from a cold reservoir have been established as a priority. As such, good progress has been noted over the past five to 10 years, with the improvement of EC temperature change from 2.5K (in ceramics) to 40K (in thin films)1 n Use the EC principles to generate electric energy. refrigeration are easier and less expensive to generate than the high magnetic fields required for magnetocaloric refrigeration. There is no dependence on rare-earth materials and the pumps are the only moving parts. Compared with existing refrigeration and heat pump technologies, EC refrigerators or heat pumps are predicted to have efficiencies of 60-70%.3 The coefficient of performance of existing refrigeration and heatpump technologies is in the range of 3-5. Major research is required to get EC refrigeration to the development stage, and there remain some challenges (see panel). Fundamental and technical features have yet to be resolved but watch this space. CJ M ETKEL YEBIYO is a PhD researcher at London South Bank University PROFESSOR ANDY FORD is acting director of research and enterprise and professor of building systems engineering at LSBU References: 1 K itanovski, A, Plaznik, U, Tomc, U, Poredo, A, Present and future caloric refrigeration and heat-pump technologies, International Journal of Refrigeration, 2015 2 Obolt, M, Kitanovski, A, Tuek, J, Poredo, A, Electrocaloric v magnetocaloric energy conversion, International Journal of Refrigeration, 2014 bit.ly/CJJul19EC 3 Analysis of potential of novel refrigeration technologies suitable for selected industries for application and improvement of food quality, energy consumption and environmental impact, FRISBEE project, 2011 POTENTIAL APPLICATIONS There are various potential applications for this technology1, including: n Replacement of vapour compression in small refrigerators n Small heat pumps n Thermal management of power electronics in integrated circuits n Air conditioning of hybrid and electric vehicles. 48 July 2019 www.cibsejournal.com CIBSE July19 pp47-48 Electrocaloric cooling.indd 48 21/06/2019 14:51