Background: Super-capacitors provide other significant advantages over large batteries. They are capable of delivering higher peak currents to facilitate large dynamic electric load swings are essentially maintenance free and operate across a wider range of temperature and charging life cycle. They are also more environmentally friendly. However unlike batteries super-capacitors provide a less stable voltage output over time as the stored charge depletes.

Solar photovoltaic (PV) power generation systems require electrical inverters to convert direct current (DC) into alternating current (AC) the standard type of electricity supplied by utilities. Inverters make up a large portion of capital costs because they must be replaced periodically over the lifetime of a solar system. The mean time before failures (MTBF) is about 3 -5 years for most PV inverters while the expected lifetime of PV cells is 20 years or more. Reductions in inverter costs as well as extended lifetimes would significantly reduce overall system costs.

Three phase PWM converters are widely used in numerous applications including adjustable speed motor drives uninterruptible power supplies and grid integration of renewable and distributed resources such as solar photovoltaics. Some of the important metrics of performance for these converters are related to the amount of total harmonic distortion (THD) in the line current switching losses in the power devices and dynamic performance.

UC San Diego researchers have developed the methods materials and designs for producing electrochemical capacitors based on carbon nanotube electrodes with enhanced capacitance due to the addition of charged defects. Specifically exposure to argon is used to controllably incorporate extrinsic defects into CNTs and increase the magnitude of both the pseudo-capacitance and double-layer capacitance by as much as 50% and 200% respectively compared to untreated electrodes.

Electrochemical capacitors are energy storage devices that provide a high-power and lightweight alternative to rechargeable industrial batteries and backup power supplies. Furthermore the capacitors exhibit high cycling efficiency fast recharge capability and reliable cold temperature performance. However current electrochemical capacitors are limited by their relatively low energy densities.

Some charge storage devices such as supercapacitors and batteries require high surface area materials that form a double layer with an electrolyte. These materials which serve as the electrode can be carbonaceous materials such as carbon black or carbon nanotubes but must also be interfaced with metal charge collectors resulting in a multi-layer structure. Such a structure often has problematic interfaces between the carbon and metals and due to the metal charge collectors such super-capacitors and batteries cannot be fabricated in a simple room-temperature process.

Future pulsed-power capacitors will require dielectric materials having very large energy densities with operating voltages > 10 kV. The operating characteristics of current state-of-the-art pulsed-power capacitors which utilize either ceramics or polymers as dielectric materials fall significantly short of this goal. To address this researchers at Northwestern University have developed nanocomposites that combine inorganic constituents and polymer matrices.

Background: While traditional electronic robots and artificial limbs have become increasingly sophisticated and athletic they employ purely electrical actuators which are wired to and thus anchored to large stationary power supplies. Though batteries can be used for these applications they store too little energy and deliver it at too low a rate for prolonged intense and autonomous activity. Therefore there is increased necessity for alternative more energy efficient actuators which will be the essential for the future of prosthetics and autonomous robots.