Glass is a dielectric material, which means electrons don’t pass easily between two of its surfaces. This property makes glass (and other dielectrics) suited for capacitor applications, where its two sides get polarized (positive and negative), and hold an electric potential between them. Some types of glass are better than others for this purpose.
A recent paper written by postdoc researcher Mohan Manoharan reports progress on various experiments with alkali-free glass of different thicknesses used in capacitor applications. The report also compares the glass with currently used polymer-based ultracapacitors, which are designed to operate at low temperatures (a very unlikely scenario in high-power applications such as electric vehicles, where power discharge is abrupt and produces a lot of heat). Polymer ultracaps need cooling and are thus inefficient.
Glass, on the other hand, doesn’t have this drawback. Manoharan identified a type of glass manufactured by Nippon Electric Glass (NEG) which can withstand temperatures higher than 180 degrees Celsius and that are still very thin.
Collaborating with Manoharan, Penn State professor of engineering science and mechanics Michael Lanagan and his team are working on a solution to make the glass even better by coating it with high-temperature polymers. This would enhance the energy density of a capacitor made with such glass by 2.25 times compared to the case when untreated glass is used.
“These flexible glass capacitors will reduce weight and cost if replacing polypropylene capacitors. They could be used in any high energy density capacitor application – not only in electric vehicles, but in heart defibrillators or weapons systems such as the electric railgun the navy is developing,” Manoharan said.
Remember that article our Ben Jerew wrote two months ago, about how the army needs powerful energy storage for a powerful electric railgun? Well I think things are on the right track now that the call has been made. It’s funny how these things work, after all.
Elon Musk is also a fan of ultracapacitors, as he told me in a February interview. If these guys’ research proves itself fruitful and the army uses it, for sure Tesla will get a hang of things before anyone else and we’ll have the technology in future Tesla cars. Ultracapacitors mean ultra-fast charging and discharging times, which is a bit in line with its co-founder’s recent statement that we’ll have 5-minute halfway recharging in a few years. Maybe they’re onto something right now, who knows?