internal combustion engine power come together in the technology
of hybrid electric vehicles (HEVs). NREL's scientists and
engineers focus on improving the way the components of
tomorrow's heavy-duty trucks will function as a unified system.
A heavy-duty HEV, as defined by the 21st Century Truck
Partnership, typically features an internal combustion engine
(usually diesel), an electric motor/generator, a rechargeable
energy storage system (usually batteries and/or ultracapacitors),
a power electronics system, and regenerative braking.
Hybrid electric components and
systems are highly developed for light-duty vehicles, but the
technology requires further development for heavy vehicle
applications. To become practical, heavy hybrids will require
efficient, reliable, cost-competitive, high-power components.
The main components of a heavy-duty HEV are described here and
featured in the interactive diagram of a heavy truck.
This diagram shows the basic heavy
hybrid components and systems and how they work. Roll your mouse
over each component to learn more.
Components and Systems
conventional vehicle, an HEV has an internal combustion engine
that can create torque to drive the truck. However, an HEV also
uses an electric motor/generator to create or augment
torque that drives the truck's wheels. This electric
motor/generator can either use electricity to create torque, or
reverse the process to use torque in a generator to create
electricity. The HEV's energy storage system captures
energy from the motor/generator, stores energy captured from
regenerative breaking, and returns energy when the driver
demands power. These advanced systems currently consist of
battery and/or ultracapacitor packs that have electrical,
thermal, and safety control features.
One energy efficiency
advantage of HEV technology over conventional vehicle technology
is regenerative braking. When the driver decelerates an
HEV, the motor becomes a generator and uses the kinetic energy
of the vehicle to generate electricity that can be stored in the
energy storage system for later use. Essentially, the HEV
reclaims some of the energy otherwise lost in deceleration.
devices play a crucial role in converting, managing, and
distributing power and energy in hybrid vehicle applications.
These devices, such as semiconductors, converters/inverters,
control and switching strategies, and packaging and cooling
units, are important to developing an efficient and
high-performance hybrid vehicle system. In heavy hybrid
vehicles, converters and inverters condition and control the
electrical signal between the energy storage unit and the
motor/generator to provide power to various components at
Heavy-duty vehicles are driven
as much as one million miles over a ten-year period and account
for about one-fourth of the U.S. energy consumed in highway
vehicles. Typically, they include trucks of various types and
uses, buses, as well as off-highway vehicles, including
construction, farming, and mining equipment.
To help advance heavy
hybrid vehicles, NREL, DOE, and industry are developing advanced
heavy hybrid propulsion systems that are projected to increase
the fuel efficiency of heavy trucks (Class 3-8) and buses by as
much as 100%, while maintaining their emissions to meet the
Environmental Protection Agency's 2007-2010 emission standards.
Read more about AH2PS's
research and development