Energy can be stored in a number of ways, from pumped hydro to supercapacitors, but you’d be unlikely to engineer pumped-hydro energy storage into an electric vehicle or smartphone.
On the other hand, there are plenty of small-scale energy storage systems for electric vehicles, smartphones, and laptops. Currently, lithium-ion battery technology delivers the best balance of energy density, durability, and lifespan. In electric vehicles, these traits are particularly critical in, not only offering low-emissions transportation, but a decent enough range and lifespan that would encourage their adoption. After all, what good is an electric vehicle if no one will drive it?
While lithium-ion batteries can take hours to charge, a potential limitation in an electric vehicle, supercapacitors take mere seconds to charge. Also, supercapacitors tend to have lifespans around ten times longer than lithium-ion, another consideration for electric vehicle lifespan. How soon could supercapacitors take over for lithium-ion batteries in an electric vehicle? It’s all a question of energy density, and supercapacitors are already in use, at least in limited applications and testing, by some automakers.
Volvo, for example, has been testing supercapacitor-embedded structural panels as a replacement for the heavy sealed lead acid battery in the engine bay. The result is a lighter vehicle for better fuel economy. The Toyota TS030 race car, a hybrid electric vehicle, employs electric motor-generators backed up by supercapacitors instead of lithium-ion or nickel-metal hydride battery packs, a great application because supercapacitors cycle so quickly and hold a lot of energy. The Toyota Yaris Hybrid R concept features 400 hp total power with three electric motors and a supercapacitor bank, yet the fuel economy of, probably, the base Yaris.
Currently, the best supercapacitors offer tens of thousands of cycles more than lithium-ion battery chemistry, can charge and discharge in just seconds, yet top out at just 40% the energy density. Supercapacitors need a little more development before they can replace lithium-ion in an electric vehicle.
Photo credit: Christophe.roques