Short Course #4 Fundamentals and Applications of Electrochemical Capacitors John R. Miller, Instructor
Electrochemical capacitors, sometimes called supercapacitors or ultracapacitors, are receiving increased attention in power sources for many applications. They offer extraordinarily high power density compared with batteries as well as high cycle-life and maintenance-free operation. Recently, emphasis has broadened from the traditional low-power to the emerging high-power applications. Power systems with battery-capacitor combinations, IC engine-capacitor combinations, and fuel cell-capacitor combinations are now appearing. Capacitor technology is being used to increase the energy efficiency of industrial equipment like fork lifts, earth-moving vehicles, and overhead cranes by capturing energy that is normally wasted. Systems developed specifically for power quality applications are appearing.
This course is targeted at technologists interested in advancing and/or exploiting electrochemical capacitor technology. The fundamentals part of the lecture covers the nature and significance of “electric double layer” and “pseudocapacitance” charge storage and compares and contrasts these charge storage mechanisms with traditional capacitor and battery technologies. Basic design rules for electrochemical capacitor components are covered.
The applications part of the lecture covers the two-terminal electrical response of electrochemical capacitors and describes how to derive and use equivalent circuit models. Power/energy behavior is discussed with reference to selecting the optimum product. Reliability aspects of electrochemical capacitor cells are discussed in detail and typical de-rating practices given that can be used to extend operational life. The importance of voltage and temperature uniformity in strings of series-connected cells is covered in detail. The goal is to provide basic understanding, necessary tools, and general information needed to successfully use such capacitor products.
A review of capacitor property and performance measurement procedures will be given with special emphasis on electrochemical impedance spectroscopy (EIS) measurement techniques. Basic measurements of capacitor properties will be demonstrated in the classroom using commercial test equipment. Time will be devoted to analysis and interpretation of the collected data.
The course will conclude with a summary of the present status of electrochemical capacitor technology, available commercial and near-commercial products, manufacturers of these products, and projections of future performance levels.
About the Instructor
John R. Miller is President of JME, Inc., a company he started in 1989 to serve the electrochemical capacitor (EC) industry providing materials evaluations, capacitor design services, capacitor testing, reliability assessment, and system engineering. Dr. Miller has reported on many critical EC technology issues and prepared test methods for the DOE. He is Chair of the annual Advanced Capacitor World Summit. Present activities include reliability evaluations of ECs for heavy hybrid vehicles and development of an advanced EC for the U.S. Navy’s all-electric ship. Dr. Miller previously held positions at SOHIO, the University of Rochester, and Los Alamos National Laboratory. He earned BS and Ph.D. degrees in physics from the Massachusetts Institute of Technology, and has 50+ publications and 8 patents. He may be reached at JMECAPACITOR@att.net.