Question: What have you done/are you doing to overcome the supercapacitors' low energy density, and what effect might this have on the end performance?

Dona Galhena answered on 9 Nov 2015:

We can address the problem of low energy density in several ways. Energy density of a supercap depends on the specific capacitance and the operating voltage of the supercap. If you increase the specific capacitance and/or operating voltage, the energy density increases. Usually Supercaps have carbon based materials to store charge. If we could modify this materials to store more charge, then we can increase the amount of energy stored in the supercap. Also, we can modify the electrolytes used in the supercapacitors to be stable even at very high voltages. Then we can operate the supercap at higher voltages and this would also give high energy density. I am working on both areas.

If the energy density is high, that means amount of energy you can store in the supercap is high. Suppose a bus is powered by a supercap. Then the distance it could travel before recharging its supercaps, becomes longer, as the energy density of the supercap becomes higher.