New high-temperature ceramic capacitor could reduce cooling needs in power electronics for hybrids and EVs
Scientists from the National Physical Laboratory (NPL) in the UK have developed a new lead-free, high-temperature ceramic capacitor that could improve the efficiency and reliability of electric and hybrid vehicles.
Hybrid and electric vehicles rely on high efficiency power conversion and management, with automotive power electronics representing an emerging £40-billion (US$61-billion) global market, NPL noted. The power electronics found in vehicles today require cooling because of limitations in the temperature rating of components such as capacitors, which are used to store electrical energy. This is a disadvantage as the extra cooling systems add weight to the vehicles, reducing efficiency and reliability.
The UK Technology Strategy Board program for Low Carbon Vehicles funded scientists at NPL and their collaborators to work on a solution to this problem by developing a new ceramic capacitor dielectric material with a high energy density, called HITECA (HIgh TEmperature CApacitor), which operates with a stable capacitance at temperatures of 200 °C and above.
Currently available capacitors are restricted to operating at temperatures around 150 °C.
The use of this new material in electric and hybrid vehicles would reduce the need for cooling and the associated weight of the vehicles. Its high permittivity could enable smaller electronic devices and its reduced loss of capacitance with voltage could improve overall vehicle performance.
Other types of capacitor, for example barium titanate capacitors, can lose up to 85% of their capacitance at working voltage.
As well as having applications in the automobile industry, HITECA capacitors could improve high temperature electronics in the aerospace, power, oil and gas sectors, and in high energy applications such as pulsed power—in which energy is stored over a period of time before being released as a high power pulse.
Industrial electronics need to be able to perform in the harsh environments in which they operate. The ability of HITECA capacitors to function at higher temperatures than existing capacitors will help make electronic systems more robust and remove barriers for technologies such as electric vehicles that rely on them.—Tatiana Correia, project lead at NPL
Other partners involved in the project are Syfer, NanoForce, Valeo, Queen Mary, University of London and Queen’s University Belfast.
NPL and Queen’s University Belfast are also working on increasing the energy density in simple dielectric capacitors to enable them to compete more generally with other energy storage technologies, using a technique called “dead-layer” engineering—the design of artificial interfacial dielectric dead layers.
M. McMillen, A. M. Douglas, T. M. Correia, P. M. Weaver, M. G. Cain, and J. M. Gregg (2012) Increasing recoverable energy storage in electroceramic capacitors using “dead-layer” engineering. Applied Physics Letters 101, 242909 doi: 10.1063/1.4772016