(625c) Ultracapacitor and Its Applications in Rapid Energy Storage and Conversion

Liquid fuels such as gasoline fossil fuels and FTS non-fossil fuels have high energy density and as a result are desirable for onboard energy storage through chemical bonds. To increase fuel efficiency, kinetic energy from braking, conventionally thought of as unusable, can in reality be recovered and electrochemically converted into reusable energy that can charge Ni-MH or Li-ion battery packs through chemical reactions. However, due to the effects of severe weather and the consequences of thermal and mechanical stresses during charge and discharge, the expected cycle lifetime of the energy storage system is diminished, reducing its efficacy. An alternative to using battery packs is to use the ultracapacitors, which store electrostatic charges in Helmholtz layers. An additional advantage using an ultracapacitor is that it has higher energy density than the conventional dielectric capacitor. Due to the absence of chemical reactions, it also has a longer cycle lifetime, albeit a higher discharge rate than a system using batteries to store energy. This work examined the viability of using an ultracapacitor module as a power capturing device. In order to understand the physical processes inside the capacitor power module, an ultracapacitor module with 300 F at an operating window from 4.0 to 14.5 volts was tested and evaluated through an ac impendence measurement via 5 mV small ac currents that were used to disturb the energy storage system. The capacitance values were determined using ac impendence technique and also calculated using V-t­ curves at different constant currents.  The further effort likely extends the lifetime for the onboard energy storage system. The advancement of the system structure and design for energy storage and conversion gives valuable support to efficient power capturing for sustainable energy needs.