Heather Andreas

Assistant Professor

BSc, PhD (University of Calgary)

E-mail: heather.andreas@dal.ca
Phone: (902) 494-4505
Fax: (902) 494-1310

* Accepting Graduate Students

Research Interests: Alternative energy storage

My laboratory’s research focus is the use of electrochemical methods to study and optimise alternative energy systems (including energy production and energy storage). The research in my group will focus on supercapacitors, an energy storage system that is similar to batteries, but utilises a different storage mechanism. In a battery, charge (and hence current) is typically provided by the electrochemical (faradaic) conversion of one chemical species to another. Conversely, in double-layer supercapacitor systems, the charge is stored in a manner similar to a capacitor, where the charge of one sign is stored on one capacitor plate and an equal but opposite charge is stored on the other plate. With supercapacitor systems, the two plates are replaced with a electrode (solid) / electrolyte (liquid) boundary, and charge is stored on the electrode surface, with the corresponding opposite charge stored in the electrolyte near the electrode surface. Typically, a high surface area carbon is used as the electrode material, while a number of different solutions can be successfully used as the electrolyte. Unlike typical capacitors, however, supercapacitors are able to store approximately a million times more charge on the same geometric area. This variation in the way charge is stored results in a number of theoretical advantages for the supercapacitor systems, including drastically increasing cycle life, (up to a million cycles compared to the 1000s of cycles available with batteries),  excellent state-of-charge indication, good power-density, and relatively inexpensive (for some configurations) and environmentally “friendly” materials.

Recently there has been significant interest in the use of supercapacitors in vehicle applications (for cold starting assistance and hybrid fuel-cell capacitor car load levelling), power line backup, and energy storage for intermittent power sources (i.e., solar panels or windmill turbines). However, one very poorly understood aspect of supercapacitor behaviour which limits their practical application is the phenomenon of self-discharge (SD), which is the loss of voltage exhibited by a supercapacitor as it sits in a charged state for long periods of time. Obviously, this is of practical importance as one would like to know that the supercapacitor is ready for use, whether it has been unused for a day or a year.

The research in my lab is designed to discover and overcome the causes of supercapacitor SD and study the factors which change the rate of this discharge. In order to examine the SD processes, the supercapacitor will be examined before and after SD using electrochemistry (using electricity to examine a system’s characteristics).   Electrochemical experiments will include (but not be limited to) Cyclic Voltammetry (measuring the current as the potential is changed in a controlled manner), Direct Current charging and discharging (recording the voltage vs. time response as charge is added or withdrawn from the system at a constant current) and SD measurements (where the voltage of the cell is recorded while the cell is resting at open circuit). These experiments will allow us to examine the effect of SD on the charge and energy storage capability of the supercapacitor. By gaining a more complete understanding of the self-discharge process it is hoped that it can be minimized or even prevented altogether, thereby extending the life and applicability of the supercapacitor.

Visit Our Lab: Andreas Research Group