Ultracapacitor Technology Leading the Way Toward Improved Electric Vehicles

by | Nov 7, 2011

As fuel prices continue to rise, electrification of transportation is increasingly important. This importance highlights the need for improved energy storage solutions with high performance and low resistance in order to meet consumer and manufacturer demands. The answer is found in ultracapacitors. Ultracapacitor technology is vital in solving consumers’ concerns, including reservations about charging time and vehicle range. Consumers need to be assured that if they switch to EVs, their cars will charge quickly and that the charges will hold for a convenient length of time. As research around energy storage technology – and specifically ultracapacitors – increases, new innovations such as higher energy density and reduced equivalent series resistance (ESR) will help overcome manufacturer and consumer concerns and further popularize EVs.

Using ultracapacitor technology for energy storage offers several benefits over batteries. Ultracapacitors operate at 95 to 98 percent efficiency, which is far beyond the efficiency of 70 percent that batteries see. Ultracapacitors can perform well in wide-ranging temperature conditions, from +65 degrees Celsius to -40 degrees Celsius. In addition, ultracapacitors have a long lifespan and require little to no maintenance.  Pricing of ultracapacitors has declined by more than 90 percent. By comparison, battery pricing has declined by less than 40 percent, and ultracapacitor prices will likely continue to decline at a faster rate than batteries.

Ultracapacitors already improve EV performance by harvesting energy from regenerative braking and other actions and storing it for other uses, thereby lengthening the time needed between charging. Ultracapacitors are able to store and provide energy quickly and have a much faster response time than that of batteries. In the regenerative braking system, which employs a motor generator and is sent with a capacitor bank, the motor generator is driven when braking is required. This in turn charges the capacitor, and the motor then delivers assistance to the vehicle as it accelerates.

Hybrid lithium/carbon ultracapacitors and carbon/carbon ultracapacitors working in conjunction with batteries are used by manufacturers to provide computer power back-up, battery disconnect, safety communication back up, airbag back-up power, emergency brakes and lights, security back-up power and power windows. By incorporating hybrid capacitors into these vehicle applications, auto manufacturers can improve their current offerings. In addition to these applications, ultracapacitors are used to increase fuel efficiency and reduce emissions, as they are a prime energy storage solution for vehicles with start/stop technology. Micro hybrids, or vehicles that employ the start/stop technology, work by shutting off the engine when a car is stopped in traffic, thereby saving fuel and reducing emissions. Ultracapacitors are used to re-launch the engine, as they provide the necessary quick start.

Already, ultracapacitors provide faster re-charge rates and longer life spans than what is found with batteries. With a higher energy density, ultracapacitors will be positioned to replace lead acid storage batteries. Research is now focused on this effort, aiming to match the energy density of lead acid storage batteries. The ability to recharge in minutes as opposed to hours means ultracapacitors can tolerate hundreds of thousands of charge/discharge cycles without failing and with almost no maintenance. As research pursues higher density ultracapacitors, the benefits to drivers will drastically increase.

EV consumers can expect to see several benefits as ultracapacitor technology approaches the stage of replacing lead acid storage batteries. Consumers will be able to recharge their EVs in minutes as opposed to hours, and ultracapacitors will be able to tolerate hundreds of thousands of charge/discharge cycles. Furthermore, virtually no maintenance is required for the ultracapacitor component. These advantages over lead acid batteries only make EVs more appealing to consumers.

Furthermore, a lower ESR in ultracapacitors means applications such as micro hybrids will be able to take greater advantage of ultracapacitors. ESR is the measure of resistance within the capacitor. As the ESR is lowered, efficiency is increased, which is, of course, a highly desired result. Increasing the efficiency even by a mere 10 percent increases the power capabilities of the ultracapacitor by a parallel amount. That boost of power translates into higher performance.

Micro hybrids require low resistance, highly efficient ultracapacitors to perform a high number of cycles during starting and stopping. When drivers start the vehicle, ultracapacitors with a lower resistance are able to deliver more energy. Although fuel performance is already increased over traditional vehicles, using ultracapacitors with low ESR and high power will allow automakers to save an even higher percentage of fuel. A more fuel-efficient car is more desirable to consumers, as it translates into higher savings and money in their pockets.

When a lower ESR is achieved, and these demands will be met in the near future, manufacturers of EVs will produce greatly improved products. Manufacturers will no longer have the burden of excess cooling requirements or suppressed cycle life.

Improved technology, such as reduced ESR, and lower costs have enticed auto manufacturers to adopt ultracapacitors for their EV models. With a forecasted compounded annual growth of 40 percent this decade, material and manufacturing costs and overall pricing will be driven down significantly. As the energy density of ultracapacitors begins to rival that of lead-acid batteries, consumer anxiety about range and charging challenges will be resolved and EVs will see true mass market adoption.

Jeff Colton is vice president of sales, North America at Ioxus.  He is responsible for managing and growing the company’s North American sales operations in multiple alternative energy sectors. Previously, Jeff held executive roles at companies including General Electric Corporation, Sanyo Electric Corporation, and Saft Battery Corporation.  

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