Hybrid electric vehicles (HEV) use “two or more energy conversion technologies.” Often, this means coupling an internal combustion engine (ICE) with a secondary source of stored electrical power such as batteries. The different power sources are then used separately or in tandem to deliver an optimum combination of power and fuel economy. The objective that has led to the development of hybrid vehicles involves delivering every greater fuel economies as the amount of allowable harmful emissions trends towards zero.
There are a number of different types of hybrid vehicle that have been released onto the market. Here is a sample of some of those HEV types. Not all of these models will have been made available outside of the United States, and those that have been released may be known by a different name in other regions.
The Insight is a gasoline/electric 2-seater parallel HEV sports coupe featuring a 12 valve, 3 cylinder, 1 liter gasoline “VTEC™ - E lean burn” engine. Insight’s engine provides 67 hp / 66 lb. ft. of torque, has variable valve timing, and a 10.8:1 compression ratio. The engine runs whenever the vehicle is underway, but shuts off under “idle-stop” situations. Power assistance comes from a 10 KW PM motor. The 5 speed manual trans and NiMH batteries help the Insight get 70 EPA test mpg and over 600 miles of driving range. A lightweight aluminum chassis and special low rolling resistance tires help to achieve this goal. The Insight demonstrates the fuel economy gains possible using hybrid technology. Insight’s Integrated Motor Assist (IMA) powertrain was in the 2002 Civic, and was expected to spread to other Honda models.
The Prius is a very successful 4-5 passenger sedan. The gasoline/electric HEV features a 1.5 liter, 16 valve, 4 cylinder “low-rev” engine with reduced pumping losses and maximized thermal efficiency and fuel economy. A “high expansion ratio cycle” Atkinson cycle engine with variable delayed intake valve closing and 13:1 CR provide 70 HP / 82 lb. ft. of torque. The gasoline engine only runs when needed. Power also comes from a 33 KW / 258 lb. ft. PM electric motor. The planetary type “power-split” electronically controlled variable transmission (ECVT), regenerative braking, and NiMH batteries help current U.S. models get around 50–56 mpg and a driving range of 550-600 miles.
The Escape is Ford’s hybrid SUV. Ford cites the Escape as getting “nearly 40 mpg under city driving conditions.” Prodigy is Ford’s family PNGV hybrid entry. It uses the energy efficient DIATA 1.2 liter, 4 cylinder diesel engine (which shuts off at vehicle standstill), a combination manual/automatic trans, and aerodynamic features to get nearly 80 mpg. The prodigy uses Ford’s LSR (low storage requirement) powertrain technology to help reduce vehicle weight and meet PNGV objectives. Ford also announced a HEV Explorer in 2004 using Volvo’s hybrid design system.
The Durango hybrid SUV uses the “through the road” system for a modest 15% mpg gain and reduced tailpipe emissions. A 3.9 liter engine powers the rear wheels, and a 3 phase AC motor the front. Combined city/highway mileage of 18.6 mpg is reported. The Dodge RAM hybrid electric pickup features a 15% mpg/kpl improvement, but can supply up to 20 kilowatts of electrical energy for auxiliary power use. Dodge’s ESX3 is an PNGV 5 passenger family sedan entry which gets 72 mpg and features an all aluminum 1.5 liter diesel and lithium-ion batteries; its range is 400 miles. DaimlerChrysler also has an 8 passenger Powerbox SUV with a 2.7 liter V-6 CNG fueled ICE, and a 70 hp electric motor to get 25 mpg GGE (gasoline gallon equivalent), and a 350 mile range. Rated SULEV, the Powerbox’s top speed is reportedly 125 mph, doing 0-60 in seven seconds.
The Precept is a highly technologically advanced PNGV 5 passenger mid-size 4WD car- reported to achieve around 80 mpg, and over 90 on the highway using a 3 cylinder, 1.3 liter CIDI Isuzu diesel engine paired with two electric motors. One electric motor powers the front wheels and the other adds motive power as required or serves as a generator to recharge the batteries. Power reaches the wheels through an automatically shifted manual trans, and the Precept uses a 3 camera rear-vision system to eliminate drag associated with exterior rear-view mirrors. GM's ParadiGM hybrid system, featuring a 3.6 liter V-6 powered hybrid SUV with 2 electric motors claims a 20% mpg/kpl improvement.
France has two hybrid Renault vans, the Modus and Operandi, which use only battery-electric power in the city, then switch to hybrid mode once outside city limits. Renault’s Koleos is an all-terrain hybrid 4WD, 2 liter turbocharged SUV with lithium ion batteries powering a 30 KW motor driving the rear wheels.
Italian Fiat’s Multipla hybrid sedan can be plugged in overnight, and can be run in three different modes – including battery-only for ZEV compliance.
Trucks and buses typically rack up highway mileage with its associated emissions, and stop-and-go urban vehicles operate where tailpipe emissions must be curtailed. Both driving situations lend themselves to hybrid technology. Engine manufacturers like Cummins, GM and others, along with truck & coach and drive system manufacturers are working together to produce more HEVs, often co-partnering with state and federal agencies. Along with clean fuel diesel ICEs, natural gas or propane fueled microturbines are being used for electro-motive power. Electric engine powered hybrid vehicles for military applications have the dual advantage of operating in a quiet battery-only “stealth mode”, or can serve as a field generator.
Most industry experts recognize the heat-engine (ICE) powered hybrid EV is an interim step towards achieving near pollution-free (hydrogen powered) transportation and cargo handling.