A hybrid electric vehicle (HEV) is a hybrid vehicle that combines a conventional propulsion system with a rechargeable energy storage system (RESS) to achieve better fuel economy than a conventional vehicle. Its secondary propulsion system, additional to the electric motors, means that it does not require regular visits to a charging unit as a battery electric vehicle (BEV) does. Modern mass-produced HEVs prolong the charge in their batteries by capturing kinetic energy by means of regenerative braking, and some HEVs can use the internal combustion engine (ICE) to generate electricity by spinning an electrical generator (often a motor-generator) to either recharge the battery or directly feed power to an electric motor that drives the vehicle. Many HEVs reduce idle emissions by shutting down the ICE at idle and restarting it when needed (start-stop system). An HEV’s engine is smaller than a non-hybrid petroleum fuel vehicle and may be run at various speeds, providing greater efficiency.
HEVs became widely available to the public in the late 1990s with the introduction of the Honda Insight and Toyota Prius, and are viewed by some automakers as a core segment of the future automotive market. Futurist magazine recently included hybrid electric vehicles as cars of the near future. Worldwide sales of Toyota and Lexus hybrids reached 1.7 million vehicles by January 2009. Hybrid cars are now a top priority for every American automaker. In 1901, while employed at Lohner Coach Factory, Ferdinand Porsche designed the “Mixte”, a series-hybrid vehicle based on his earlier “System Lohner-Porsche” electric carriage. The Mixte broke several Austrian speed records, and also won the Exelberg Rally in 1901 with Porsche himself driving. The Mixte used a gasoline engine powering a generator, which in turn powered electric hub motors, with a small battery pack for reliability. It had a range of 50 km, a top speed of 50 km/h and a power of 5.22 kW during 20 minutes.
In 1905, H. Piper filed a US patent application for a hybrid vehicle. The 1915 Dual Power, made by the Woods Motor Vehicle electric car maker, had a four-cylinder ICE and an electric motor. Below 15 mph (25 km/h) the electric motor alone drove the vehicle, drawing power from a battery pack, and above this speed the “main” engine cut in to take the car up to its 35 mph (55 km/h) top speed. About 600 were made up to 1918
A more recent working prototype of the HEV was built by Victor Wouk (one of the scientists involved with the Henney Kilowatt, the first transistor-based electric car). Wouk’s work with HEVs in the 1960s and 1970s earned him the title as the “Godfather of the Hybrid”. Wouk installed a prototype hybrid drivetrain (with a 16 kW electric motor) into a 1972 Buick Skylark provided by GM for the 1970 Federal Clean Car Incentive Program, but the program was stopped by the United States Environmental Protection Agency (EPA) in 1976 while Eric Stork, the head of the EPA at the time, was accused of a prejudicial coverup.
