Boost transportation efficiency with ultracaps

Boost transportation efficiency with ultracaps

Manufacturers are using ultracaps to replace or enhance

batteries for hybrid buses, micro hybrids, and light rail

BY CHAD HALL
Vice President of Sales
Ioxus
www.ioxus.com

Rising fuel costs and the looming Corporate Average Fuel Economy (CAFE) regulations make the need for electrification of transportation more immediate. With an increased focus on clean technology, transportation markets are being hybridized and more engineers are seeking ultracapacitor technology to increase the efficiency of energy storage systems. Manufacturers are using ultracapacitors to replace or enhance batteries in transportation applications like hybrid buses, micro hybrids and light rail. When combined with a battery in a hybrid system, ultracapacitors improve the power density of the hybrid supply, enabling the battery to work more efficiently.

The iCAP 3,000-F capacitor features low equivalent series resistance targeting transportation drive, grid power storage, and regenerative energy capture applications.

As the adoption of ultracapacitor technology grows, manufacturers and engineers demand continually improved technology. They look for technology improved thermally, electrically and mechanically that betters the overall efficiency of transportation applications. To meet these demands, Ioxus introduced the next generation in its ultracapacitor cell offering: a 2.7-V, 3,000-F iCAP cell. The cell enhances energy storage systems by improving performance in the particular areas where they fall short, and it helps meet manufacturers’ and engineers’ latest requirements, which encourages faster market adoption.

The Ioxus iCAP has a lower equivalent series resistance (ESR) and an increased power density beyond its competitors, allowing a variety of applications to take better advantage of ultracapacitors. ESR measures the resistance within a capacitor, and as the rating goes up, it results in a greater loss of efficiency. Stemming that loss boosts the power capabilities, which improves performance. Transportation markets have been eagerly awaiting ultracapacitor technology that frees manufacturers from the burden of excess cooling requirements. With a 12% lower ESR than any product on the market, Ioxus’ 3,000-F iCAP cell is one step closer to meeting these needs. In addition, the cell is rugged and designed to withstand the high shock, high vibration and wide-ranging temperature conditions present in rail, bus and electric vehicle applications.

Hybridized energy storage system

Ultracapacitors are extremely beneficial in hybrid bus applications in assisting with regenerative braking. Regenerative braking captures energy generated during braking that would otherwise be wasted and quickly releases it for re-acceleration. The ultracapacitors are charged during braking and, because they provide the fast discharge needed during this process, they allow the vehicle to accelerate without hesitation.

A lower ESR is advantageous in hybrid bus applications, as well, because it significantly reduces the cooling requirements, thereby prolonging cell life. Ultracapacitors have a high life cycle and more power in comparison to batteries, making them useful in these kinds of applications. When an ultracapacitor is combined with a battery, it allows the power density of the hybrid supply to increase. The battery can operate more efficiently since it is not diminished by large current spikes that occur without the presence of a capacitor, leading to more usable energy per charge from the battery. Using such an energy storage solution improves the overall system, as it reduces the size and weight of the required battery. Combining ultracapacitors with batteries can lengthen the life cycle of the batteries, ultimately increasing efficiency of the bus. By doing this, we allow each chemistry type to do as it was intended: ultracapacitors provide the power, and the battery provides the energy.

Ride-through in light-rail applications

Light rail transit is an electric rail form of transportation which operates at a higher capacity and higher speed than tramways, while implementing pollution-free electric rail cars. Light rail applications use ultracapacitors in several ways. For example, small advanced power units are used to maintain voltage during power-station switches, eliminating the brown-outs and dim lights that cause problems with digital electronics. Ultracapacitors are also tapped to provide a fast charge during regenerative braking, which is then used to accelerate the train from the station, removing the need for unsightly and expensive overhead wires. Due to the high cycle life requirements, ultracapacitors are the only energy storage product with enough volumetric power and longevity to handle this demanding application.

A low ESR is important in light rail applications that practice on-board acceleration because their cooling requirements can easily become high. Trains accelerate away from the station across distances as long as 500 m, using power provided by ultracapacitors. A large number of ultracapacitors are required to provide this power and the number of cycles can reach 350,000 per year, which generates heat from the system and cell resistance. This in turn creates demanding cooling requirements. Ultracapacitors with a lower ESR can significantly lower the heat generation of the system, thus lowering the high cooling requirements of these applications by a parallel amount, making systems smaller, lighter and more efficient. The iCAP 3,000-F cell has a 12% lower ESR than any other product on the market, making it extremely desirable to transit manufacturers for use in on-board acceleration.

Prime for start-stop applications

In micro hybrids using start-stop technology, a regular combustion engine is turned off while at a stop light or in traffic. The engine is then restarted quickly upon acceleration, before the driver even notices. Because ultracapacitors can charge and discharge energy rapidly and handle high cell cycles, they offer a prime technology to support this application. Pairing the 3,000-F iCAP cell with a battery enhances the efficiency of the start-stop application by providing a large amount of support for the system. While some start-stop systems perform poorly under cold temperatures because of battery limitations, ultracapacitors have an operational range of 40°C to +65C, ensuring that systems work properly even under extreme conditions. By placing the capacitor in series with the battery, the capacitor provides a boost of voltage, keeping the battery from dropping below lower voltage limits.

Ultracapacitors are much more efficient at recapturing energy than batteries, and they significantly improve vehicles’ energy storage capabilities. An ultracapacitor has a 95% to 98% round-trip efficiency, compared to the 60% to 70% efficiency of various battery types. In micro hybrids, this increased level of efficiency conserves fuel and allows more energy to be stored in a shorter amount of time for use in re-launching a vehicle. Using technology like the iCAP 3,000-F ultracapacitor can improve efficiency in micro-hybrid applications by 10% to 15% . Ultracapacitors are not only a better alternative to batteries because of their performance, but also because of their cost. Ultracapacitor pricing has fallen quickly; it experienced a 90% decrease over the past decade.

Transportation and mass transit markets are moving toward greater efficiency and better performance, and implementing an ultracapacitor-based energy storage solution can help manufacturers achieve both. Ioxus’ newest ultracapacitor cell features the lowest weight, lowest ESR, and highest power density available on the market. All of these aspects of improved energy storage systems highlight the important role ultracapacitors have in bringing hybrid transportation mainstream. With this increased focus on electric transportation and vehicle efficiency, it is not surprising that ultracapacitor volumes are expected to see more than 50 percent compounded annual growth during this decade. ■