Hybrid car

Overview

A hybrid car uses more than one power source, almost always an internal-combustion engine and an electric motor. In the hybrid design the engine replaces batteries that would normally be used in an all-electric car, thereby avoiding problems with range that many complain about.

There are several advantages to this configuration:

• The vehicle is lighter and roomier than a purely electric vehicle, because it does not need to carry nearly as many batteries
• The internal-combustion engine in a hybrid-electric can be much smaller and lighter, getting far better gas mileage than in a conventional vehicle, because the engine runs at a relatively constant speed, and does not need to provide direct power for acceleration, which is the biggest reason for large engines
• Braking can be configured to recapture part of the kinetic energy of movement that is otherwise lost in a conventional vehicle

There are also some disadvantages:

• The initial vehicle is costlier due to the extra hardware as for example large batteries and generators
• Due to the additional hardware the weight is increased
• Maintenance cost may increase as more hardware has to be maintained and repaired if necessary
• Some hybrid electric vehicles hold parts of the additional hardware in the trunk, resulting in a reduced storage capacity

History

The first successful hybrid electric car was engineered by Ferdinand Porsche in 1928. Since then, hobbyists have built such cars but no such car was put into production until the twenty-first century, when Honda Insight and Toyota Prius were the commercially available hybrid models. These vehicles have a direct linkage from the internal combustion engine to the drive, so that the engine can provide acceleration power. Prototypes of plug-in hybrid cars, with larger battery packs that can be re-charged from the power grid, have been built in the U.S., and one production PHEV, the Renault Kangoo, went on sale in France in 2003.

Early hybrid designs tended to use the electric motor for all power, due to simplicity. The engine would charge batteries from which the motor drew power, running only when needed to charge them back up, and at its "best power" speed when doing so.

Recent developments

More modern designs reverse this to some degree, using the gasoline engine for primary power, but using one that is smaller than would otherwise be needed. The motor is essentially a very large starter motor, which operates not only when the engine needs to be turned over, but also when the driver "steps on the gas" and requires extra power. Instead of the engine solely charging the batteries, the motor acts as a generator during braking, using the momentum of the car to generate electricity. Thus the energy that would normally be lost when stopping is used to speed the car back up. Since the amount of electrical power needed is much smaller, the need for large battery systems is eliminated. Such designs were released in the late 1990s in the Honda Insight and Toyota Prius, but both were impractical, small designs that didn't see wide consumer acceptance. Newer designs are considerably more conventional, often appearing and performing identically to their non-hybrid counterparts while delivering 50% better gas mileage. The Honda Civic Hybrid appears identical to the non-hybrid version, for instance, but delivers about 50 mpg (US gallons).

One particularly interesting combination uses the newer technique, with a diesel engine. Diesels are excellent engines for delivering constant power for long periods of time, suffering less wear while delivering higher efficiency. However, the engines also suffer from poor acceleration due to having a limited RPM range. This poor acceleration can be addressed with the hybrid technique, and such designs may offer performance in a car of over 100 mpg; however, there are no production models as of 2003.

In the first generation hybrid car, the internal combustion engine only serves as an on-board generator to supply power to the electric motor which provide the sole driving force to the wheels. In the second generation, the internal combustion engine drives the wheels directly with the electric motor serves as a power assist when extra power is needed and to recapture the kinetic energy into electic energy during braking. The extra power from the electric motor enables the manufactorers to reduce the engine size to achieve fuel economy. Either approach has its limitations. Starting from 2004 model year, the Toyota Prius uses the third generation hybrid design. In this new design, the wheels can be driven by either the internal combustion engine or the electric motor using a planetary gear system to draw power from either source. The on-board computer optimizes the fuel usage by shutting off the internal combustion engine when the electric motor is sufficient to provide the power. The internal combustion engine starts up whenever extra power is needed or the battery needs recharging. The electric motor serves as the main driving force and a generator. The more efficient new design enabled Toyota to build the new Prius as a mid-size car without sacraficing fuel economy.

2004 should see the first hybrid SUV's. Announced model year 2005 hybrid versions include the Toyota Highlander and Lexus RX 400h and Ford Escape.

Battery technology

It appears that battery technology will not evolve to address the needs of fully-electric cars in the near future. All companies involved in such research have since given up, and moved to fuel cells and hybrids. Toyota has announced that it intends that all its vehicles will have a hybrid electric version by 2012. It appears many European companies, where diesel is much more common, will follow Toyota's lead and move in the same direction.

See also

• Diesel electric locomotive
• Gas-electric hybrid engine

External links

• Ars Technica: 2003 Honda Civic Hybrid Car Review
• MIT/Industry Consortium on Advanced Automotive Electrical/Electronic Components and Systems: Jumpstarting and Charging Batteries with the New 42V PowerNet.

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