Energy harvesting is a hot topic in printed electronics, partly because of shortcomings of printed batteries. Several companies have used smaller batteries in active RFID tags boosted by photovoltaics, for example. However, even here the batteries can present challenges of life, cost or environmental credentials.
Maybe we can learn from electric vehicles, where use of ultracapacitors - sometimes called supercapacitors - to balance power delivery is receiving increased attention. Like traditional electrolytic capacitors, ultracapacitors rely on ionic effects to provide exceptionally large capacitance in a small volume and thin film versions are possible.
Unlike batteries, ultracapacitors do not rely on a chemical reaction so they last longer. Unfortunately, they usually have only 5% of the power storage of a battery, so any major use in energy storage rather than management of energy delivery has been elusive. Power balancing is more usual rather than replacing batteries themselves.
Electric vehicle demonstration
Recently, a souped up Saturn Vue car demonstrated outstanding performance thanks to power delivered as appropriate from batteries, a gasoline engine and an ultracapacitor, the latter providing very rapid power delivery when needed.
Much better performance - even replacing the battery
However, EEStor of Texas now seems to be changing the fundamentals of ultracapacitors by employing barium titanate rather than an electrolyte. Its "Electrical Energy Storage Units" will go into production later this year and the company already has a deal to supply energy units for mobile military applications.
Another envisaged application is the rapid charging of electric vehicles. Indeed, Zenn Motor Company in Toronto has signed a deal with EEstor to use the ultracapacitors to replace batteries, according to the press. That means that the leakage of energy from such capacitors, which has prevented them storing energy for an extended period of time, has also been overcome.
Nanotechnology approach
Joel Schindall of Massachusetts Institute of Technology gets the necessary large surface area in an ultracapacitor by using carbon nanotubes, each five nanometers across. He hopes this can push ultracapacitors up from 5% to 50% of the storage capacity of a battery.
For more attend Printed Electronics Europe 2008.
