What is a Hybrid Vehicle?

hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles (HEVs), which combine an internal combustion engine and one or more electric motors.

Two wheeled vehicles (cycle type vehicles)

Mopeds and electric bicycles are a simple form of a hybrid, as power is delivered both via an internal combustion engine or electric motor and the rider’s muscles. Early prototypes of motorcycles in the late 1800s used the same principles.

  • An example of Parallel Hybrid Bicycle

    An example of Parallel Hybrid Bicycle

    In a parallel hybrid bicycle human and motor power are mechanically coupled at the at the rear wheel. Human and motor torques are added together. Almost all manufactured models are of this type.

  • In a series hybrid bicycle (SH) the user powers a generator using the pedals. This is converted into electricity and can be fed directly to the motor giving a chainless bicycle but also to charge a battery. The motor draws power from the battery and must be able to deliver the full mechanical torque required because none is available from the pedals. Series hybrid bicycles are commercially available, because they are very simple in theory and manufacturing.

Four wheeled vehicles

Engine type

1) Hybrid electric-petroleum vehicles

When the term hybrid vehicle is used, it often refers to a Hybrid electric vehicle. These encompass such vehicles as the Chevrolet Tahoe, GMC Yukon, Chevrolet Silverado, Cadillac Escalade, and the Saturn Vue, Toyota Prius, Toyota Camry Hybrid, Ford Escape Hybrid, Toyota Highlander Hybrid, Honda Insight, Honda Civic Hybrid Lexus RX 400h and 450h and others.

A petroleum-electric hybrid most commonly uses internal combustion engines (generally gasoline or Diesel engines, powered by a variety of fuels) and electric batteries to power electric motors. There are many types of petroleum-electric hybrid drive trains, from Full hybrid to Mild hybrid, which offer varying advantages and disadvantages.

Toyota Prius, the most popular plug-in

Toyota Prius, the most popular plug-in

Ferdinand Porsche in 1900 developed the first gasoline-electric series-hybrid automobile in the world, setting speed records using two motor-in-wheel-hub arrangements with a combustion generator set proving the electric power. While liquid fuel/electric hybrids date back to the late 1800s, the braking regenerative hybrid was invented by David Arthurs, an electrical engineer from Springdale, Arkansas in 1978–79. His home-converted Opel GT was reported to return as much as  26.5 kilometers per liter  (75 mpg) with plans still sold to this original design.

The plug-in-electric-vehicle (PEV) is becoming more and more common. It has the range needed in locations where there are wide gaps with no services. The batteries can be plugged in to house (mains) electricity for charging, as well being charged while the engine is running.

2) Continuously outboard recharged electric vehicle (COREV)

Given suitable infrastructure, permissions and vehicles, Battery Electric Vehicles (BEVs) can be recharged while the user drives. The BEV establishes contact with an electrified rail, plate or overhead wires on the highway via an attached conducting wheel or other similar mechanism (see Conduit current collection). The BEV’s batteries are recharged by this process—on the highway—and can then be used normally on other roads until the battery is discharged.

This provides the advantage of virtually unrestricted highway range as long as you stay where you have BEV infrastructure access. The technology for such electrical infrastructure outside some cities, is not widely distributed.

3) Hybrid fuel (dual mode)

In addition to vehicles that use two or more different devices for propulsion, some also consider vehicles that use distinct energy sources or input type fuels using the same engine to be hybrids, although to avoid confusion with hybrids as described above and to use correctly the terms, these are perhaps more correctly described as dual mode vehicles:

  • Some electric trolley buses can switch between an on board diesel engine and overhead electrical power depending on conditions . This could be combined with a battery subsystem to create a true plug-in hybrid trolley bus.
  • Flexible-fuel vehicles can use a mixture of input fuels mixed in one tank, for eg. gasoline and ethanol or methanol or biobutanol.
  • Bi-fuel vehicle: Liquified petroleum gas and compressed natural gas are very different from petroleum or diesel and cannot be used in the same tanks, so it would be impossible to build an (LPG or CNG) flexible fuel system.
    Chevrolet Spark LPG (runs on either petrol or LPG)

    Chevrolet Spark LPG (runs on either petrol or LPG)

    Instead vehicles are built with two, parallel, fuel systems feeding one engine. While the duplicated tanks cost space in some applications, the increased range and flexibility where (LPG or CNG) infrastructure is incomplete may be a significant incentive to purchase.

  • Some vehicles have been modified to use another fuel source if it is available, such as cars modified to run on LPG and diesels modified to run on waste vegetable oil that has not been processed into biodiesel.

4) Fluid power hybrid

Hydraulic and pneumatic hybrid vehicles use an engine to charge a pressure accumulator to drive the wheels via hydraulic or pneumatic (compressed air) drive units. The energy recovery rate is higher and therefore the system is more efficient than battery charged hybrids, demonstrating a 60% to 70% increase in energy economy in EPA testing. Under tests done by the EPA, a hydraulic hybrid Ford Expedition returned 13.6 kms per liter (32 miles per US gallon or 38 mpg) in the City, and 9.35 kms per liter(22 miles per US gallon or 26 mpg) highway.

While the system has faster and more efficient charge/discharge cycling and is cheaper than gas-electric hybrids, the accumulator size dictates total energy storage capacity and requires more space than a battery.

UPS using Hydraulic Hybrid Trucks

UPS using Hydraulic Hybrid Trucks

Hybrid vehicle power train configurations

1) Parallel hybrid

In a parallel hybrid the electric motor and the internal combustion engine are installed so that they can both individually or together, power the vehicle. In contrast to the power split configuration typically only one electric motor is installed. Most commonly the internal combustion engine, the electric motor and gear box are coupled by automatically controlled clutches. For electric driving the clutch between the internal combustion engine is open while the clutch to the gear box is engaged. While in combustion mode the engine and motor run at the same speed. The first mass production parallel hybrid is the Honda Insight.

Honda Insight

Honda Insight

2) Mild parallel hybrid

These types use a generally compact electric motor (usually <20 kW) to provide auto-stop/start features and to provide extra power assist during the acceleration, and to generate on the deceleration phase (regenerative braking).

On-road examples include Honda Civic Hybrid, Honda Insight, Mercedes Benz S400 BlueHYBRID, BMW 7-Series hybrids, General Motors BAS Hybrids and Smart fortwo with micro hybrid drive.

Honda Civic Hybrid

Honda Civic Hybrid

3) Power-Split Series-Parallel Hybrid

Typical passenger car installations include the Toyota Prius, the Ford Escape, the Lexus Gs450 and LS600.

In a power-split hybrid electric drive train there are two motors: an electric motor and an internal combustion engine. The power from these two motors can be shared to drive the wheels via a power-splitter, which is a simple planetary gear set. The ratio can be from 0-100% for the combustion engine, or 0-100% for the electric motor, or an anything in between, such as, 40% for the electric motor and 60% for the combustion engine. The electric motor can act as a generator charging the batteries.

On the open road, the primary power source is the internal combustion engine, when maximum power is required, for example to overtake, the electric motors are used to assist maximizing the available power for a short period, giving the effect of having a larger engine than actually installed. In most applications, the engine is switched off when the car is stationary reducing curbside emissions.

Ford Escape Hybrid

Ford Escape Hybrid

4) Series-Hybrid

Series or serial-hybrid have also been referred to as a Extended Range Electric Vehicle or Range-Extended Electric Vehicle (EREV/REEV) however, range extension can be accomplished with either series or parallel hybrid layouts.

Series-hybrid vehicles are driven by the electric motor with no mechanical connection to the engine. Instead there is an engine tuned for running a generator when the battery pack energy supply isn’t sufficient for demands.

This arrangement is not new being common in diesel-electric locomotives and ships. Ferdinand Porsche used this set up in the early 20th century in racing cars, effectively inventing the series-hybrid arrangement. Porsche named the system, System Mixt. A wheel hub motor arrangement, with a motor in each of the two front wheels was used, setting speed records. This arrangement was sometimes referred to as an electric transmission, as the electric generator and driving motor replaced a mechanical transmission. The vehicle could not move unless the internal combustion engine was running.

The setup was never proved to be suitable for production cars being unable to synchronise the electric driving motors with the generator set power, resulting in higher fuel consumption. It is currently being revisited by several manufacturers, but no data is available to say if running the engine at peak efficiency will override all the energy conversion steps necessary and result in an improvement over a parallel or series/parallel setup. It does not seem likely that it will equal the peak transmit efficiency of an optimized manual transmission simply due to electronic and switching/conversion losses, but it does simplify the engineering a little, and might make it easier for an “average” driver to get better fuel economy.

In 1997 Toyota released the first series-hybrid bus sold in Japan. Meanwhile, GM will introduce the Chevrolet Volt in 2010, aiming for an all-electric range of 40 miles after which operates as a series hybrid.And a price tag of around $40,000. Supercapacitors combined with a lithium ion battery bank have been used by AFS Trinity in a converted Saturn Vue SUV vehicle. Using supercapacitorsthey claim up to 150 mpg in a series-hybrid arrangement.

Chevrolet Volt

Chevrolet Volt

5) Plug-in hybrid electrical vehicle (PHEV)

Another subtype added to the hybrid market is the Plug-in Hybrid Electric Vehicle (PHEV). The PHEV is usually a general fuel-electric (parallel or serial) hybrid with increased energy storage capacity (usually Li-ion batteries). It may be connected to mains electricity supply at the end of the journey to avoid charging using the on-board internal combustion engine.

Reva, a Indian made PHEV

Reva, a Indian made PHEV

This concept is attractive to those seeking to minimize on-road emissions by avoiding – or at least minimizing – the use of ICE during daily driving. As with pure electric vehicles, the total emissions saving, for example in CO2 terms, is dependent upon the energy source of the electricity generating company.

For some users, this type of vehicle may also be financially attractive so long as the electrical energy being used is cheaper than the petrol/diesel that they would have otherwise used. Current tax systems in many European countries use mineral oil taxation as a major income source. This is generally not the case for electricity, which is taxed uniformly for the domestic customer, however that person uses it. Some electricity suppliers also offer price benefits for off-peak night users, which may further increase the attractiveness of the plug-in option for commuters and urban motorists.

Tesla Roadster

Tesla Roadster

6) Fuel cell, electric hybrid

The fuel cell hybrid is generally an electric vehicle equipped with a fuel cell. The fuel cell as well as the electric battery are both power sources, making the vehicle a hybrid. Fuel cells use hydrogen as a fuel and power the electric battery when it is depleted.

The Chevrolet Equinox FCEV, Ford Edge Hyseries Drive and Honda FCX are examples of a fuel cell/electric hybrid.

Honda FCX

Honda FCX

Hybrid Vehicle Emissions

Hybrid Vehicle emissions today are getting close to or even lower than the recommended level set by the EPA (Environmental Protection Agency). The recommended levels they suggest for a typical passenger vehicle should be equated to 5.5 metric tons of carbon dioxide. The three most popular hybrid vehicles, Honda Civic, Honda Insight and Toyota Prius, set the standards even higher by producing 4.1, 3.5, and 3.5 tons showing a major improvement in carbon dioxide emissions.

Hybrid vehicles can reduce air emissions of smog-forming pollutants by up to 90% and cut carbon dioxide emissions in half. Based on the average driving habits of an individual, pollution of these vehicles can be reduced anywhere between 25% to 90%, when you compare them to an everyday gas-powered vehicle.

There are also different pollution numbers when you are comparing different brands of hybrid vehicles. It is also important to note that the emissions are merely transferred to electrical plants for plug-in hybrids; and with many areas of the world burning fossil fuels for electricity, these transferred emissions are quite large.

Environmental impact of hybrid car battery

Though hybrid cars consume less petroleum than conventional cars, there is still an issue regarding the environmental damage of the Hybrid car battery. Today most Hybrid car batteries are one of two types, either nickel metal hydride, or lithium ion. Both these batteries are regarded as more environmentally friendly than lead-based batteries, which constitute the bulk of car batteries today. There are many types of batteries. Some are far more toxic than others. While batteries like lead acid or nickel cadmium are incredibly bad for the environment, the toxicity levels and environmental impact of nickel metal hydride batteries (the type currently used in hybrids) are much lower. Nickel-based batteries are known carcinogens, and have been shown to cause a variety of teratogenic effects.

Hitachi Lithium-ion Battery

Hitachi Lithium-ion Battery

The Lithium-ion battery has attracted attention due to its potential for use in hybrid electric vehicles. Hitachi is a leader in its development. Additionally, the market for Lithium-ion batteries is rapidly expanding as an alternative to the nickel-metal hydride batteries, which have been utilized in the hybrid market thus far. In addition to its smaller size and lighter weight, lithium-ion batteries deliver performance that helps to protect the environment with features such as improved charge efficiency without memory effect. In an environment where motor vehicle requirements including lower exhaust emissions and better fuel economy are prevalent, it is anticipated that the practical use of hybrid, electric, and fuel cell vehicles will continue to increase. The lithium-ion batteries are appealing because they have the highest energy density of any rechargeable batteries and can produce a voltage more than three times that of nickel-metal hydride battery cell while simultaneously storing large quantities of electricity as well. The batteries also produce higher output (boosting vehicle power), higher efficiency (avoiding wasteful use of electricity), and provides excellent durability, compared with the life of the battery being roughly equivalent to the life of the vehicle. Additionally, use of lithium-ion batteries reduces the overall weight of the vehicle and also achieves improved fuel economy of 30% better than gasoline-powered vehicles with a consequent reduction in CO2 emissions helping to prevent global warming.

The lithium-ion batteries supplied by Hitachi are flourishing in a wide range of different applications including cars, buses, commercial vehicles and trains. Electric vehicles that have the ability to be recharged from an owner’s main power supply are now available in several global automotive markets. When these vehicles are charged overnight (which is less costly than charging the vehicle during the day in Japan), the expense is about one-ninth of the cost for fueling a gasoline powered vehicle.

Raw materials increasing costs

There is an impending increase in the costs of many rare materials used in the manufacture of hybrid cars.

For example, the rare earth element dysprosium is required to fabricate many of the advanced electric motors and battery systems in hybrid propulsion systems. Neodymium is another rare earth metal which is a crucial ingredient in high-strength magnets that are found in permanent magnet electric motors.

Nearly all the rare earth elements in the world come from China, and many analysts believe that an overall increase in Chinese electronics manufacturing will consume this entire supply by 2012. In addition, export quotas on Chinese Rare Earth exports have resulted in a generally shaky supply of those metals.

A few non-Chinese sources such as the advanced Hoidas Lake project in northern Canada as well as Mt. Weld in Australia are currently under development, however it is not known if these sources will be developed before the shortage hits.

Alternative green vehicles

Other types of green vehicles include other vehicles that go fully or partly on alternative energy sources than fossil fuel. Another option is to use alternative fuel composition (i.e. biofuels) in conventional fossil fuel-based vehicles, making them go partly on renewable energy sources.

Volkswagen Jetta TDI Clean Diesel

Volkswagen Jetta TDI Clean Diesel

If you guys and gals have any questions just write in a comment and i will surely post a reply.


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