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Benefits of ultracapacitor for EV energy storage

Posted: 14 Mar 2012 ?? ?Print Version ?Bookmark and Share

Keywords:Electric vehicles? ultracapacitor? battery pairing?

Nowadays, electric vehicles (EVs) are basking in the limelight with several models from auto manufacturers such as General Motors, Tesla and Nissan on the market today. There are also more models to come in the future. The cost of fuel continues to rise, and there is pressure from the government 每 through proposed legislation like the corporate average fuel economy (CAFE) regulations 每 for automakers to reduce vehicle emissions and improve fuel efficiency. Automakers are calling for more efficient power sources to meet these demands. In short, the market need for EVs will only increase with time and more consumers will make the switch to fuel-efficient vehicles.

The growing demand for EVs is spurring the automotive industry's search for sophisticated components to extend the longevity of these vehicles while simultaneously improving their performance capabilities. Research and advancements in efficient components over the last several years has led to a hybrid energy storage system consisting of an ultracapacitor and battery pairing. This pairing increases energy and improves the power density of the hybrid supply, which allows the battery to operate without large current spikes that would normally occur when using just a battery. When the battery can operate without current spikes, it has a longer, more effective life. The hybrid system reduces the cycling of the battery under heavy load conditions, in turn extending the life of the hybrid supply and providing a more efficient energy supply.

Benefits over batteries
Ultracapacitors store energy electrostatically, whereas batteries produce energy via a chemical reaction. For automotive manufacturers, this difference means an economical, versatile power delivery technology more beneficial than batteries. Coupled with batteries in a hybrid system, ultracapacitors improve the range and performance of trucks, passenger and delivery vehicles.

An important step in improving fuel efficiency is reducing the gross weight of vehicles. Using an ultracapacitor helps with this, as the size and weight of the battery used is greatly reduced. Batteries are heavy and large, so implementing a system where ultracapacitors provide the power allows the battery to be sized for energy instead of power. This results in a smaller-size, higher energy density battery that achieves the same performance.

Beyond size and weight reduction, ultracaps offer other benefits over batteries. They operate with high efficiency, high charge acceptance and cycle stability in a wide temperature range 每 from +65∼ Celsius to 每40∼ Celsius. Batteries can't perform well below 0∼ Celsius. Ultracaps also boast a high cycle life; often their life cycles are longer than the machines into which they are built. Ultracaps can go through charge and discharge cycles more than a million times, which meets the requirements of hybrid vehicle start/stop applications. The long lifecycle makes for little to no required maintenance, ultimately resulting in cost savings.

In further demonstration of their cost savings, ultracapacitors' prices have fallen by 99 per cent in the past decade, while battery prices have fallen by just 30 to 40 per cent in the same period. Mass volume savings possible with ultracapacitors just aren't achievable with batteries. Ultracapacitors are a relatively new introduction to the industry, and as they are further developed and adopted, their prices are likely to keep dropping. Batteries, though, have been on the market for more than 100 years and their prices are for the most part stabilised.

One final advantage over batteries is the increased efficiency and power ultracaps provide. They are 95 to 98 per cent round-trip efficient compared to an average of 60 to 80 per cent efficiency for various batteries. An important benefit, especially to vehicle acceleration applications, is that ultracapacitors have up to 1,000 times the power density of batteries. Higher power means a higher fuel savings since a hybrid system can power starting and ignition systems at a lower voltage regulation.

Automotive apps
Ultracapacitors on the market today are more rugged and durable in order to provide the best solution for acceleration, energy recapture, peak load shaving and other high power applications. Durable cells are able to operate in demanding environments such as hybrid drive technology and meet an industry need for high performance. In addition, ultracapacitors are increasingly built for easy integration so auto manufacturers can easily install the cells without additional engineering teams.

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