Maxwell Technologies signed a memorandum of understanding (MOU) with Valeo covering a development collaboration to incorporate Maxwell’s BOOSTCAP ultracapacitors in Valeo’s next generation StARS+X—a stop/start and regenerative braking system. (Earlier post.)
The new StARS 14+X (starter alternator reversible system) consists of a reversible starter-alternator, a multi-cell ultracapacitor energy storage module and other power and control electronics in a 14-volt architecture. It enables standard gasoline and diesel engines to shut down during idle phases and restart instantly, eliminating fuel consumption and emissions anytime the vehicle is stopped.
Valeo estimates that the system can reduce fuel consumption and associated emissions by about 12% in normal operation and more than 20% in stop-and-go urban traffic.
In its earlier efforts with StARS+X, Valeo was working with multiple ultracapacitor technologies with capacitance values of 200 farads with nominal voltage between 20V and 30V, depending upon the technology. The company is using different size powerpacks—12-, 10- and 6-cell—to support a range of powertrains and internal space constraints.
The powerpacks must last for the lifetime of the vehicle, deliver reliability in the harsh thermal environment created by being close to the engine, and be safe and environmentally friendly. Valeo is specifying 600,000 stop-starts, 1 million regeneration events, and 200,000 boost events for the system.
The first generation StARS with start-stop capability, which did not include a dedicated energy storage component, initially was offered in 2004. The new 14+X architecture incorporates enhanced electronics and an ultracapacitor energy storage module that allows it to recuperate and store energy from braking, which otherwise would be dissipated as friction and heat in a conventional braking system.
The recovered energy is then available to power peak electrical loads such as de-icing and rapid cabin and seat heating and cooling, avoiding increased fuel consumption for such functions.
Because its energy storage employs high-efficiency, low-cost, ultracapacitor technology rather than costly nickel metal hydride or lithium-ion batteries, StARS 14+X can deliver 80 percent of the benefit of a mild hybrid system at 20 percent of the cost. Tax incentives and free access to high occupancy vehicle lanes have helped to stimulate demand for current premium-priced hybrid cars as niche products, but we believe that mass adoption of low-emission vehicles and much greater benefits in reduced CO2 and other greenhouse gas emissions will be driven by the availability of more cost-effective hybrid architectures.—Daniel Richard, Director, R&D Valeo Electrical Systems
Richard also noted that the flexible 14+X system’s ability to be adapted for integration with a wide variety of existing motor platforms and to be applied to any new fuel technology such as flex fuel will make time-to-market for new models incorporating it much shorter than more radical hybrid approaches.
The MOU also covers terms of a proposed multi-year development and supply agreement through which Valeo will source ultracapacitors from Maxwell.