Hybrid Vehicles: Hybrid Vehicles

Hybrid Vehicles

Toyota Prius

A hybrid vehicle (HV) is a vehicle using an on-board rechargeable energy storage system (RESS) and a fuelled power source for vehicle propulsion. The HV pollutes less and uses less fuel. The different propulsion power systems may have common subsystems or components. The HV provides better fuel economy than a conventional vehicle because the engine is smaller and may be run at speeds providing more efficiency. Other techniques may be used to recover or reduce waste energy (such as regenerative braking and shutting down the combustion engine).

The term most commonly refers to petroleum-electric hybrid vehicles, also called Hybrid-electric vehicle (HEV) which use internal combustion engines and electric batteries to power electric motors. Modern mass-produced hybrids prolong the charge on their batteries by capturing kinetic energy via regenerative braking. As well, when cruising or in other situations where just light thrust is needed, "full" hybrids can use the combustion engine to generate electricity by spinning an electrical generator (often a second electric motor) to either recharge the battery or directly feed power to an electric motor that drives the vehicle. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrids still require gasoline and diesel as their sole fuel source. A number of other hybrid vehicles use hydrogen fuel.

Hybrid was often used to describe an engine swap. Some have also referred to flexible-fuel vehicles as "hybrids" because they can use a mixture of different fuels — typically gasoline and ethanol alcohol fuel.

Automobiles and light trucks

A number of manufacturers currently produce hybrid automobiles and light trucks, including Ford, General Motors, Honda, Mazda, Nissan, Peugeot, Renault and Toyota.

Trains, trucks and buses

In May 2003 JR East started test runs with the so called NE (new energy) train and validated the system's operability (series hybrid with lithium ion battery) in cold regions. In 2004, RailPower Technologies had been running pilots in the US with the so called Green Goats which led to orders by the Union Pacific and Canadian Pacific Railways starting in early 2005.
Also in 2005 GE introduced its hybrid shifters on the market. Toyota claims to have started with the Coaster Hybrid Bus in 1997 on the Japanese market. In May 2003 GM started to tour with hybrid buses developed together with Allison. Several hundreds of those buses have entered into daily operation in the US. The Blue Ribbon City Hybrid bus was presented by Hino, a Toyota affiliate, in January 2005.

In 2003 GM introduced a diesel hybrid military (light) truck, equipped with a diesel electric and a fuel cell auxiliary power unit. Hybrid light trucks were introduced 2004 by Mercedes (Hybrid Sprinter) and Micro-Vett SPA (Daily Bimodale). International Truck and Engine Corp. and Eaton Corp. have been selected to manufacture diesel-electric hybrid trucks for a US pilot program serving the utility industry in 2004. In mid 2005 Isuzu introduced the Elf Diesel Hybrid Truck on the Japanese Market. They claim that approximately 300 vehicles, mostly route buses are using Hinos HIMR (Hybrid Inverter Controlled Motor & Retarder) system.
New Flyer and Gillig produce hybrid buses using Allison's electric drive system. The Whispering Wheel bus is another hybrid.

A promising but as-yet unseen application for hybrid vehicle technology would be in garbage trucks, since these vehicles do stop-start driving and often stand idling.

Locomotives

Railpower offers hybrid road switchers, as does GE. Diesel-electric locomotives may not always be considered hybrids, not having energy storage on board, unless they are fed with electricity via a collector for short distances (for example, in tunnels with emission limits), in which case they are better classified as dual-mode vehicles.

Other military vehicles

The United States Army's manned ground vehicles of the Future Combat System all use a hybrid electric drive consisting of a diesel engine to generate electrical power for mobility and all other vehicle subsystems.

Taxicabs

Hybrid technology may be particularly appropriate for use as taxicabs, as in many locations they are used in predominantly urban environments; have intensive operating schedules, maximizing fuel savings over the life of the vehicle; and may spend considerable periods of time at idle, where the hybrid engine may allow for the combustion engine to be shut off (while retaining use of electrical accessories). Hybrid taxicabs are primarily based on production passenger vehicles, with modifications (often aftermarket) to meet specialized usage requirements and/or local regulations (security features, for example). Since vehicles in taxicab service may operate for 10-20 hours per day, the reduction in local pollution and noxious emissions may be more significant than that achieved by hybrids in private vehicle use.

In 2005, New York City added six Ford Escape Hybrids to their taxi fleet and city officials said the entire fleet of 13,000 vehicles could be converted within five years.

Two-wheeled vehicles

Mopeds and Power-assisted bicycles can be considered hybrid vehicles in a sense, because power is delivered both via a conventional or electric motor and the rider's muscles.

Benefits of the hybrid design

1) Current hybrid vehicles reduce petroleum consumption (compared to otherwise similar ICE vehicles) primarily by using three mechanisms:

a) Reducing wasted energy during idle/low output, generally by turning the internal combustion engine off;

b) Recapturing waste energy (i.e. regenerative braking);

c) reducing the size and power of the ICE engine, and hence inefficiencies from under-utilisation, by using the better torque response of electric motors to compensate for the loss in peak power output from the smaller internal combustion engine.

2) Hybrids may also make more aggressive use of other fuel-saving techniques, such as reduced weight; these are not advantages of the hybrid design, but engineering choices made for various reasons, including marketing to consumers conscious of these issues.

3) Trade-offs include higher weight for electric motors and batteries, which may reduce fuel efficiency at highway speeds compared to otherwise equivalent ICE vehicles, or even result in lower fuel efficiency at highway speeds than in urban use

4) The internal-combustion engine in a hybrid vehicle is smaller, lighter, and more efficient than the one in a conventional vehicle, because the engine can be sized for slightly above average power demand rather than peak power demand. A standard combustion engine is required to operate over a range of speed and power, yet its highest efficiency is in a narrow range of operation—in a hybrid vehicle, the engine operates within its range of highest efficiency. The power curve of electric motors is better suited to variable speeds and can provide substantially greater torque at low speeds compared with internal-combustion engines.

5) Like many electric cars, but in contrast to conventional vehicles, braking in a hybrid is controlled in part by the electric motor which can recapture part of the kinetic energy of the car to partially recharge the batteries. This is called regenerative braking and one of the reasons for the high efficiency of hybrid cars. In a conventional vehicle, braking is done by mechanical brakes, and the kinetic energy of the car is wasted as heat.

6) Hybrids' greater fuel economy has implication for reduced petroleum consumption and vehicle air pollution emissions worldwide

7) Reduced wear on the gasoline engine, particularly from idling with no load

8) Reduced wear on brakes from the regenerative braking system use.

9) Reduced noise emissions resulting from substantial use of electric engine at low speeds, leading to roadway noise reduction and beneficial noise health effects. Note, however, that this is not always an advantage; for example, people who are blind or visually-impaired, and who rely on vehicle-noise while crossing streets, find it more difficult to do safely.

10) Reduced air pollution emissions due to lower fuel consumption, leading to improved human health with regard to respiratory and other illness. Composite driving tests indicate total air pollution of carbon monoxide and reactive hydrocarbons are 80 to 90 percent cleaner for hybrid versus conventional vehicles. Pollution reduction in urban environments may be particularly significant due to elimination of idle-at-rest.

11) Increased driving range without refueling or recharging, compared with electric vehicles and perhaps even compared with internal-combustion vehicles. Limitations in range have been a problem for traditional electric vehicles. Hybrids may have substantially longer "operating hours" per unit of petroleum in certain conditions than the mileage-rated fuel efficiency figures may indicate, due to the reduction of idle-at-rest.

Mileage of Different Models of Hybrid cars

Vehicle (automatic transmission) & Mileage ( Miles per U.S. Gallon)
Honda Insight hybrid (two seater)
-57 city / 56 highway
Toyota Prius hybrid (midsize)
-60 city / 51 highway
Honda Civic hybrid (compact)
-49 city / 51 highway
Honda Accord (midsize)
-30 city / 37 highway
Mercury Mariner (SUV)
-33 city / 29 highway
Ford Escape hybrid (SUV)
-33 city / 29 highway
Toyota Highlander (SUV)
-33 city / 26 highway
Lexus RX 400h (SUV)
-31 city / 27 highway
Chevrolet Sierra (Pickup Truck)
-17 city / 19 highway
GM Silverado (Pickup Truck)
-17 city / 19 highway

Toyota Hybrid System

Toyota has also developed and has been marketing Electric Vehicles (EV) that use motors for the driving source; Hybrid Vehicles (HV) that combine an engine and a motor, fusing the advantages of these two power sources; Fuel Cell Hybrid vehicles (FCHV) that use Fuel Cells (FC) to generate electricity based on a chemical reaction between hydrogen and the oxygen in the air and that supply this electricity to electric motors to produce driving power.

In January 1997, Toyota declared the start of the Toyota Eco Project. As part of this effort, Toyota decided to tackle the international challenge of reducing CO2 emissions in order to prevent global warming and accelerated the development of a hybrid vehicle with the goal of achieving twice the fuel efficiency of conventional vehicles. Then, in March of the same year, Toyota announced the completion of a new power train called the Toyota Hybrid System (THS) for use in passenger vehicles.

HS: This power train combines a gasoline engine and an electric motor, and because it does not require external charging, as do existing electric vehicles, it works within existing infrastructures such as fueling facilities. This system also achieves nearly twice the fuel efficiency of conventional gasoline engines.THS was installed in the passenger vehicle Prius, which was introduced in December 1997 in the Japanese market as the first mass-produced hybrid passenger vehicle in the world. In 2000, overseas marketing of the Prius began. The Prius has gained a reputation as a highly innovative vehicle, and its cumulative worldwide sales have exceeded 110,000 units. Meanwhile, THS has continued to evolve, and in 2001, THS-C, which combines THS with CVT (Continuously Variable Transmission), was installed in the Estima Hybrid minivan and THS-M (a mild hybrid system) was installed in the Crown, luxury sedan, both for the Japanese market thereby contributing greatly to innovations in the automobiles of the 21st century.Building on the ecology-focused THS, Toyota has developed the concept of Hybrid Synergy Drive. Based on this concept, Toyota has developed a new-generation Toyota hybrid system called THS II, which achieves high levels of compatibility between environmental performance and power by increasing the motor output by 1.5 times, greatly boosting the power supply voltage and achieving significant advances in the control system, aiming for synergy between motor power and engine power.

How THSII works:

Superb coordination between engine and motor.Motor power is used for starting the vehicle. For normal operation, the engine and the motor are optimally controlled to increase fuel efficiency. When powerful acceleration is needed, the high-output motor and the engine generate optimum power. This represents further evolution in smooth yet powerful running performance.

The system consists of two kinds of motive power sources, i.e.,
- a high-efficiency gasoline engine that utilizes the Atkinson Cycle, which is a high- expansion ratio cycle
- a permanent magnet AC synchronous motor with 1.5 times more output,
- a generator, high-performance nickel-metal hydride (Ni-MH) battery
- a power control unit.
This power control unit contains a high-voltage power circuit for raising the voltage of the power supply system for the motor and the generator to a high voltage of 500 V, in addition to an AC-DC inverter for converting between the AC current from the motor and the generator and the DC current from the hybrid battery. Other key components include a power split device, which transmits the mechanical motive forces from the engine, the motor and the generator by allocating and combining them. The power control unit precisely controls these components at high speeds to enable them to cooperatively work at high efficiency.

1. Start and low to mid-range speedsThe engine stops when in an inefficient range, such as at start-up and in low to mid-range speeds. The vehicle runs on the motor alone. (A)

2. Driving under normal conditionsEngine power is divided by the power split device. Some of the power turns the generator, which in turn drives the motor. (B)The rest of the power drives the wheels directly. (C)Power allocation is controlled to maximize efficiency.

3. Sudden accelerationExtra power is supplied from the battery (A), while

the engine and high-output motor provide smooth response (B+C) for improved acceleration characteristics.

4. Deceleration, brakingThe high-output motor acts as a high-output generator, driven by the vehicle's wheels. This regenerative braking system recovers kinetic energy as electrical energy, which is stored in the high-performance battery. (D)

5. Battery rechargingBattery level is managed to maintain sufficient reserves. The engine drives the generator to recharge the battery