What is Hybrid Vehicle Engineering?

Hybrid electric vehicles (HEV’s) typically combine the internal combustion engine of a conventional vehicle with the battery and electric motor of an electric vehicle.

How do Hybrids Work?

Hybrid electric vehicles (HEV’s) are powered by two energy sources—an energy conversion unit (such as a combustion engine or fuel cell) and an energy storage device (such as batteries or ultra capacitors). The energy conversion unit may be powered by gasoline, methanol, compressed natural gas, hydrogen, or other alternative fuels.

HEV’s can have a parallel design, a series design, or a combination of the two.

Off-Highway vehicles that use hydrostatic transmissions might want a series design.  In a series design, the HEV does not have a direct mechanical connection between the hybrid power unit and the wheels.  The primary engine is connected to a generator which supplies power directly to the propulsion motors & to charge the battery.  The battery provides added propulsion power during climbs & accelerations, and provides power to drive non-propulsion components.  An example might be an agricultural combine.  The wheels propelling the machine could be driven by motors wired directly to the generator.  The threshing cylinder & header could be wired to the battery.  When the engine has power, in excess of propulsion need, the generator would recharge the batteries.  The downside is that series HEV’s require larger, and therefore, heavier battery packs than parallel vehicles.  In addition, the engine works hard to maintain battery charge because the system is not operating in parallel.

The main advantage of the series design is it’s easier to configure than the parallel design, especially where the parallel design would require elaborate drivelines.  Series designs are usually less expensive.

Fig. 1: Series Hybrid Drive

In a parallel design, the HEV has a direct mechanical connection between the hybrid power unit and the wheels, as in a conventional vehicle, but also has an electric motor that drives the wheels.  The primary engine is used for driving; the electric motor provides added power during climbs, acceleration, and other periods of high demand.  One benefit of a parallel configuration is the parallel design will usually be more efficient than the series design, if a mechanical driveline can be made simple,

A second benefit is power does not need to be redirected through the batteries and can therefore be more efficient.

Fig. 2: Parallel Hybrid Drive

Prairie Engineering:  What we can do to assist with your projects.

We are the Off-Highway distributor and integrator for Azure Dynamics.  They are one of the premier HEV manufacturers and integrators for buses and step delivery vans with queued up order volumes in the multiple thousands, working with Ford and several major delivery fleet services.

We are able to leverage their volumes and HEV expertise along with our own Off-Highway experience from sizing and providing components, all the way up to full engineering design of the power train and VCU systems.