10-01-2011, 05:12 PM
SUBMITTED BY TRYSON J PURATHUR
ABSTRACT:
Electronics power systems in automotive applications are undergoing a massive change.
Firstly, the transition from internal combustion engines to electric, fuel cell, and hybrid power is gathering momentum. At the same time, cars are becoming more sophisticated, evolving towards an intelligent electrically-powered platform with many more electronic subsystems and accessories—requiring a substantial increase in the need for electric power
There have been fundamental problems of energy storage and delivery among automotive applications that have yet to be successfully and cost effectively overcome. Many of these issues are due to the limitations of batteries—heavy, large, with a limited charging rate and potentially high maintenance.
Recently, newer designs have taken advantage of the benefits of another component: the ultracapacitor. Ultracapacitors, utilize high surface area electrode materials and thin electrolytic dielectrics to achieve capacitances several orders of magnitude larger than conventional capacitors. . Integrating ultracapacitors with other energy devices solves many challenges that are not solved efficiently using a single device. For example, combining high energy lead-acid batteries and ultracapacitors can create a system that has the excellent energy, self-discharge, availability, and low cost associated with lead-acid technology, and the high charge acceptance, high efficiency, cycle stability, and excellent low-temperature performance of the ultracapacitor. Ultracapacitors can also play a valuable role in distributed power systems, thus simplifying the wiring required and reducing cost.
System design engineers can take advantage of the power of ultracapacitors to conserve energy by allowing the engine to stop while the vehicle is stationary, and then to be restarted nearly instantly on “tip in” of the throttle. Ultracapacitors also allow regenerative braking energy to be captured, thereby significantly increasing efficiency and reducing pollution. The use of engine start/stop and regenerative braking has been estimated to produce between 7 and 15% increased fuel efficiency while reducing pollution by even more.
Ultracapacitors are based on an electric double layer technology. An ultracapacitor stores energy electro statically by polarizing an electrolytic solution. Though it is an electrochemical device there are no chemical reactions involved in its energy storage mechanism. This mechanism is highly reversible, allowing the ultracapacitor to be charged and discharged hundreds of thousands of times—in fact, Maxwell’s latest ultracapacitors are rated at one million charging cycles.
Ultracapacitors are compact in size and can store a much higher amount of energy than conventional capacitors while also being able to deliver at a much higher power than batteries
