Vehicle Energy Storage
Energy storage devices and systems, which include batteries and ultracapacitors, are essential components of many advanced vehicles. Reliable energy storage systems are especially important in hybrid electric vehicles, which include an electric motor as well as a gasoline-powered motor. Energy storage systems save fuel by allowing the engine to turn off when it isn't needed, such as at stop lights. Energy storage systems also provide electricity to operate equipment such as lights and air conditioners when the engine is turned off.
Using electric energy to start and accelerate a vehicle means we can use a smaller and lighter gasoline engine would be needed in many vehicles that run only on gas or diesel fuel. These smaller engines can operate at a higher efficiency more of the time (known as load leveling). The energy storage system in a hybrid electric vehicle can capture and store kinetic energy when the vehicle slows down or stops (known as regenerative braking). A regenerative braking system captures, for later use, the energy that is usually dissipated by the brakes through heat.
Today's hybrid electric vehicles usually feature nickel-metal hydride or lithium-ion batteries. The power going in and out of these batteries generates heat, however, and this heat can reduce the efficiency and life of a battery. So, NREL's researchers use complex computer models and test methods to find ways to effectively remove unwanted heat while developing more powerful (and more energy-efficient) batteries.