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A hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle.[1] The term most commonly refers to hybrid electric vehicles (HEVs), which combine an internal combustion engine and one or more electric motors.

Contents

Power

Power sources for hybrid vehicle include:

Vehicle type

Two-wheeled and 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.

  • In a parallel hybrid bicycle human and motor power are mechanically coupled at the pedal drive train or at the rear or the front wheel, e.g. using a hub motor, a roller pressing onto a tire, or a connection to a wheel using a transmission element. Human and motor torques are added together. Almost all manufactured models are of this type. See Motorized bicycles, Mopeds and[4] for more information.
  • 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. SH bicycles are commercially available, because they are very simple in theory and manufacturing.[5]
The first known prototype and publication of an SH bicycle is by Augustus Kinzel (US Patent 3'884'317) in 1975. In 1994 Bernie Macdonalds conceived the Electrilite SH lightweight vehicle which used power electronics allowing regenerative braking and pedaling while stationary. In 1995 Thomas Müller designed a "Fahrrad mit elektromagnetischem Antrieb" in his 1995 diploma thesis and built a functional vehicle. In 1996 Jürg Blatter and Andreas Fuchs of Berne University of Applied Sciences built an SH bicycle and in 1998 mounted the system onto a Leitra tricycle (European patent EP 1165188). In 1999 Harald Kutzke described his concept of the "active bicycle": the aim is to approach the ideal bicycle weighing nothing and having no drag by electronic compensation. Until 2005 Fuchs and colleagues built several prototype SH tricycles and quadricycles. [4]

Heavy vehicles

Hybrid power trains are used for diesel-electric or turbo-electric railway locomotives, buses, heavy goods vehicles, mobile hydraulic machinery, and ships. Typically some form of heat engine (usually diesel) drives an electric generator or hydraulic pump which powers one or more electric or hydraulic motors. There are advantages in distributing power through wires or pipes rather than mechanical elements especially when multiple drives—e.g. driven wheels or propellers—are required. There is power lost in the double conversion from typically diesel fuel to electricity to power an electric or hydraulic motor. With large vehicles the advantages often outweigh the disadvantages especially as the conversion losses typically decrease with size. With the exception of non nuclear submarines, presently there is no or relatively little energy storage capacity on most heavy vehicles, e.g. auxiliary batteries and hydraulic accumulators—this is changing.

Rail transport

Europe
An example of a typical "hybrid" is the new Autorail à grande capacité (AGC or high-capacity railcar) built by the Canadian company Bombardier for service in France. This has dual mode (diesel and electric motors) and dual voltage capabilities (1500 and 25000 V) allowing it to be used on many different rail systems.[6]

China
The First Hybrid Evaluating prototype locomotive was designed and contracted by railway research center MATRAI in 1999 and the sample was ready in 2000. it was a G12 locomotive that was converted to hybrid by using a 200KW diesel generator and batteries and also was equipped with 2 AC traction motors (out of 4) retrofited in the cover of the DC traction motors.

Japan
The first operational prototype of a hybrid train engine with significant energy storage and energy regeneration capability was introduced in Japan as the KiHa E200. It utilizes battery packs of lithium ion batteries mounted on the roof to store recovered energy.[7]

North America
In the U.S., General Electric introduced a prototype railroad engine with their "Ecomagination" technology in 2007. They store energy in a large set of sodium nickel chloride (Na-NiCl2) batteries to capture and store energy normally dissipated during dynamic braking or coasting downhill. They expect at least a 10% reduction in fuel use with this system and are now spending about $2 billion/yr on hybrid research.[8]

Variants of the typical diesel electric locomotive include the Green Goat (GG) and Green Kid (GK) switching/yard engines built by Canada's Railpower Technologies. They utilize a large set of heavy duty long life (~10 yr) rechargeable lead acid (Pba) batteries and 1000 to 2000 HP electric motors as the primary motive sources and a new clean burning diesel generator (~160 Hp) for recharging the batteries that is used only as needed. No power or fuel are wasted for idling—typically 60–85% of the time for these type locomotives. It is unclear if dynamic braking (regenerative) power is recaptured for reuse; but in principle it should be easily utilized.

Since these engines typical need extra weight for traction purposes anyway the battery pack's weight is a negligible penalty. In addition the diesel generator and battery package are normally built on an existing "retired" "yard" locomotive's frame for significant additional cost savings. The existing motors and running gear are all rebuilt and reused. Diesel fuel savings of 40–60% and up to 80% pollution reductions are claimed over that of a "typical" older switching/yard engine. The same advantages that existing hybrid cars have for use with frequent starts and stops and idle periods apply to typical switching yard use.[9] "Green Goat" locomotives have been purchased by Canadian Pacific Railway, BNSF Railway, Kansas City Southern Railway and Union Pacific Railroad among others.

Cranes

Railpower Technologies Corp. engineers working with TSI Terminal Systems Inc. in Vancouver, British Columbia are testing a hybrid diesel electric power unit with battery storage for use in Rubber Tyred Gantry (RTG) cranes. RTG cranes are typically used for loading and unloading shipping containers onto trains or trucks in ports and container storage yards. The energy used to lift the containers can be partially regained when they are lowered. Diesel fuel and emission reductions of 50–70% are predicted by Railpower engineers.[10] First systems are expected to be operational in 2007.[11]

Road Transport, Commercial Vehicles

GM has launched hybrid versions of its full-size GMC Yukon (pictured) and Chevrolet Tahoe SUVs for 2008

Early hybrid systems are being investigated for trucks and other heavy highway vehicles with some operational trucks and buses starting to come into use. The main obstacles seem to be smaller fleet sizes and the extra costs of a hybrid system are yet compensated for by fuel savings,[12] but with the price of oil set to continue on its upward trend, the tipping point may be reached by the end of 1995. Advances in technology and lowered battery cost and higher capacity etc. developed in the hybrid car industry are already filtering into truck use as Toyota, Ford, GM and others introduce hybrid pickups and SUVs. Kenworth Truck Company recently introduced a hybrid-electric truck, called the Kenworth T270 Class 6 that for city usage seems to be competitive.[13][14] FedEx and others are starting to invest in hybrid delivery type vehicles—particularly for city use where hybrid technology may pay off first.[15]

Military Off Road Vehicles

Since 1985, the U.S. military has been testing serial hybrid Humvees[16][17] and have found them to deliver faster acceleration, a stealth mode with low thermal signature/ near silent operation, and greater fuel economy.

Ships

Ships with both mast-mounted sails and steam engines were an early form of hybrid vehicle. Another example is the diesel-electric submarine. This runs on batteries when submerged and the batteries can be re-charged by the diesel engine when the craft is on the surface.

Newer hybrid ship-propulsion schemes include large towing kites manufactured by companies such as SkySails. Towing kites can fly at heights several times higher than the tallest ship masts, capturing stronger and steadier winds.

Aircraft

Delta Air Lines is going to be turning their Boeing 737NGs into hybrids in early 2010 by mounting the WheelTug ground propulsion system on their fleet of Boeing 737NGs [18][19]. By using the APU, which is powered by a turbine, to power a Chorus Motor mounted on the landing gear for ground movement, Delta Air Lines will be creating a hybrid configuration by ceasing to use the main engines for anything but take off, landing, and flight.

Boeing 737-800

The Boeing Fuel Cell Demonstrator Airplane has a Proton Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electric motor, which is coupled to a conventional propeller. The fuel cell provides all power for the cruise phase of flight. During takeoff and climb, the flight segment that requires the most power, the system draws on lightweight lithium-ion batteries.

The demonstrator aircraft is a Dimona motor glider, built by Diamond Aircraft Industries of Austria, which also carried out structural modifications to the aircraft. With a wing span of 16.3 meters (53.5 feet), the airplane will be able to cruise at approximately 100 kilometers per hour (62 miles per hour) on power from the fuel cell.[20]

Engine type

Hybrid electric-petroleum vehicles

Hybrid Optare Solo

When the term hybrid vehicle is used, it most often refers to a Hybrid electric vehicle. These encompass such vehicles as the AHS2 (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 drivetrains, from Full hybrid to Mild hybrid, which offer varying advantages and disadvantages.[21]

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 75MPG with plans still sold to this original design, and the "Mother Earth News" modified version on their website.[22]

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.

Continuously outboard recharged electric vehicle (COREV)

Given suitable infrastructure, permissions and 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, in principle, of virtually unrestricted highway range as long as you stay where you have BEV infrastructure access. Since many destinations are within 100 km of a major highway, this may reduce the need for expensive battery systems. Unfortunately private use of the existing electrical system is nearly universally prohibited.

The technology for such electrical infrastructure is old and, outside of some cities, is not widely distributed (see Conduit current collection, trams, electric rail, trolleys, third rail). Updating the required electrical and infrastructure costs can be funded, in principle, by toll revenue, gasoline or other taxes.

Hybrid fuel (dual mode)

Ford Escape Hybrid the first hybrid electric vehicle with a flexible fuel capability to run on E85(ethanol).

In addition to vehicles that use two or more different devices for propulsion, some also consider vehicles that use distinct energy sources or input types ("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 trolleybuses can switch between an on board diesel engine and overhead electrical power depending on conditions (see dual mode bus). In principle, this could be combined with a battery subsystem to create a true plug-in hybrid trolleybus, although as of 2006, no such design seems to have been announced.
  • Flexible-fuel vehicles can use a mixture of input fuels mixed in one tank — typically gasoline and ethanol, or methanol, or biobutanol.
  • Bi-fuel vehicle:Liquified petroleum gas and 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 NG) flexible fuel system. 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 NG) 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 autogas (LPG) and diesels modified to run on waste vegetable oil that has not been processed into biodiesel.
  • Power-assist mechanisms for bicycles and other human-powered vehicles are also included (see Motorized bicycle).

Fluid power hybrid

Hydraulic and pneumatic hybrid vehicles use an engine to charge a pressure accumulator to drive the wheels via hydraulic or pneumatic (i.e. 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 [23]. Under tests done by the EPA, a hydraulic hybrid Ford Expedition returned 32 miles per US gallon (7.4 L/100 km; 38 mpg-imp) City, and 22 miles per US gallon (11 L/100 km; 26 mpg-imp) highway.[24] UPS currently has two trucks in service with this technology.[25]

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.

Hybrid vehicle power train configurations

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.

Mild parallel hybrid

These types use a generally compact electric motor to give extra output[26] during the acceleration, and to generate on the deceleration phase.

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

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 maximising 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 cars is stationary reducing curbside emissions.

Series-Hybrid

The Chevrolet Volt is a series plug-in hybrid on sale in 2011. The car is powered by electric traction only. The power of the Internal combustion engine is exclusively used to generate electricity, being part of a generator set.
Ford Escape plug-in hybrid.

Series or serial-hybrid have also been referred to as a Range-Extended Electric Vehicle (REEV); however, range extension can be accomplished with either series or parallel hybrid layouts. The series-hybrid looks promising and looks to be the most common form of hybrid vehicle in the near future.

Series-hybrid vehicles are driven only by the electric motor. Unlike piston internal combustion engines, electric motors are efficient with exceptionally high power/weight ratios providing adequate torque over a wide speed range. Unlike combustion engines electric motors matched to the vehicle do not require a transmission between the engine and wheels shifting torque ratios. Transmissions add weight, bulk and sap power from the engine. Mechanical automatic shifting transmissions can be very complex. In a series-hybrid system, the combustion engine drives an electric generator instead of directly driving the wheels. The generator provides power for the driving electric motors. In short, a series-hybrid is simple, the vehicle is driven by electric motors with a generator set providing the electric power.

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. Technology has caught up, with modern computer engine management systems optimising generator set running to match the power needed for the electric traction. Electric motors have become substantially smaller, lighter and efficient over the years. These advances have given the advantage to the electric transmission in normal operating conditions, over a conventional internal combustion engine and mechanical automatic transmission. One of the advantages is the smoother progressive ride with no stepped gear ratio changes.

The electric transmission is currently viable in replacing the mechanical transmission. However, the modern series-hybrid vehicles take the electric transmission to a higher plain adding greater value. There is a difference to an electric transmission. Modern series-hybrids contain:

  • Electric traction only - using only one or more electric motors to drive the vehicle.
  • Combustion engine - that turns only a generator.
  • A generator - turned by the combustion engine to make up a generator set that also acts as an engine starter.
  • A battery bank - which acts as an energy buffer.
  • Regenerative braking - reclaims energy lost when braking by converting it to electricity instead of releasing it as heat.
  • May be plugged into the electric mains system to recharge the battery bank.
  • May have supercapacitors to assist the battery bank and claw back most energy from braking - currently only fitted in proven prototypes.

The electric driving motor may run entirely fed by electricity from a large battery bank or via the generator turned by the internal combustion engine, or both. The battery bank may be charged by mains electricity reducing running costs as the range running under the electric motors only is extended. The vehicle conceptually resembles a Diesel-electric locomotive with the addition of large battery bank that may power the vehicle without the internal combustion engine running. The generator may simultaneously charge the battery bank and power the driving electric motor that moves the vehicle. The battery bank acts as an energy buffer. An advantage is that when the vehicle is stopped the combustion engine is switched off. When the vehicle moves it does so using the energy in the batteries. This reduces kerbside emissions greatly in cities and towns. Vehicles at traffic lights, or in slow moving stop start traffic need not be polluting when stationary, and saving fuel in the process.

In some arrangements when high levels of power are required, such as in vehicle acceleration, the electric driving motor draws electricity from both the batteries and the generator. With the Chevy Volt if the battery bank is depleted the vehicle may run entirely with electricity provided only from the generator. Some prototype vehicle designs such as the Volvo ReCharge and Ford F-Series pickup have electric motors in wheel hubs reducing the need for a differential saving weight, space and power being sapped by the differential. Series-hybrids can be also fitted with a supercapacitor or a flywheel to store regenerative braking energy, which can improve efficiency by clawing back energy that otherwise would be lost being dissipated as heat through the braking system.

Because a series-hybrid omits a mechanical link between the combustion engine and the wheels, the engine can be run at a constant and efficient rate even as the vehicle changes speed. The vehicle speed and engine speed are not necessarily in synchronisation. The engine can thus maintain an efficiency closer to the theoretical limit of 37%, rather than the current average of 20%.[citation needed] At low or mixed speeds this could result in ~50% increase in overall efficiency (19% vs 29%). However General Motors have designed the Chevy Volt's engine/generator set to operate between 1,200 and 4,000 revolutions per minute. The Lotus company has introduced an engine/generator set design that runs at two speeds, giving 15 kW of electrical power at 1,500 rpm and 35 kW at 3,500 rpm via the integrated electrical generator.[27]

As the requirements for the engine are not directly linked to vehicle speed, this gives greater scope for more efficient or alternative engine designs, such as a microturbine[28], rotary Atkinson cycle engine or a linear combustion engine.[29]

There are stages of operation: power from the combustion engine to the generator and then to the electric motor and, depending on the design, may also run through the generator and into the battery pack then to the electric motor further reducing efficiency (see illustration). Each transformation through each stage results in a loss of energy. However in normal vehicle operating conditions the energy buffer of the battery bank, which stores clawed back energy from braking and the optimum running of the combustion engine may raise overall operating efficiency, despite each stage being an energy loss. The engine to a mechanical automatic shifting transmission efficiency is approximately 70–80%. A conventional mechanical clutch transmission, has an engine to transmission efficiency of 98%.[citation needed] In a series-hybrid vehicle, during long-distance high speed highway driving, the combustion engine will need to supply the majority of the energy, in which case a series-hybrid may be 20–30% less efficient than a parallel hybrid.[citation needed]

The use of a motor driving a wheel directly eliminates the conventional mechanical transmission elements: gearbox, transmission shafts and differential, and can sometimes eliminate flexible couplings. This offers great simplicity. If the motors are integrated into the wheels a disadvantage is that the unsprung mass increases and suspension responsiveness decreases which impacts ride performance and potentially safety. However the impact should be minimal if at all as electric motors in wheel hubs such as Hi-Pa Drive, may be very small and light having exceptionally high power/weight ratios. The braking mechanisms can be lighter as the wheel motors brake the vehicle. Light aluminium wheels may be used reducing the unsprung mass of the wheel assembly. Vehicle designs may be optimised to reduce the centre of gravity having the heavy mechanicals and battery banks at floor level. If the motors are attached to the vehicle body, flexible couplings are still required. Advantages of individual wheel motors include simplified traction control and all wheel drive if required, allowing lower floors, which is useful for buses. Some 8x8 all-wheel drive military vehicles use individual wheel motors. Diesel-electric locomotives have used this concept for over 60 years.[citation needed]

In a normal road vehicle the whole series-hybrid power-transmission setup may be smaller and lighter than the equivalent conventional mechanical power-transmission setup, liberating space and less weight. As the combustion generator set only requires cables to the driving electric motors, there is greater flexibility in major component layout spread across the vehicle giving superior weight distribution or maximising vehicle cabin space. This flexibility may lead to superior vehicle designs.

In 1997 Toyota released the first series-hybrid bus sold in Japan.[30] Meanwhile, GM hopes to introduce the Chevy Volt by 2011, aiming for an all-electric range of 40 miles[31] and a price tag of around $40,000.[32] Supercapacitors combined with a lithium ion battery bank have been used by AFS Trinity in a converted Saturn Vue SUV vehicle. Using supercapacitors they claim up to 150 mpg in a series-hybrid arrangement.[33]

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.[34][35]

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.

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.

Environmental issues

Fuel consumption and emissions reductions

The hybrid vehicle typically achieves greater fuel economy and lower emissions than conventional internal combustion engine vehicles (ICEVs), resulting in fewer emissions being generated. These savings are primarily achieved by three elements of a typical hybrid design:

  1. relying on both the engine and the electric motors for peak power needs, resulting in a smaller engine sized more for average usage rather than peak power usage. A smaller engine can have less internal losses and lower weight.
  2. having significant battery storage capacity to store and reuse recaptured energy, especially in stop-and-go traffic.
  3. recapturing significant amounts of energy during braking that are normally wasted as heat. This regenerative braking reduces vehicle speed by converting some of its kinetic energy into electricity, depending upon the power rating of the motor/generator;

Other techniques that are not necessarily 'hybrid' features, but that are frequently found on hybrid vehicles include:

  1. shutting down the engine during traffic stops or while coasting or during other idle periods;
  2. improving aerodynamics; (part of the reason that SUVs get such bad fuel economy is the drag on the car. A box shaped car or truck has to exert more force to move through the air causing more stress on the engine making it work harder). Improving the shape and aerodynamics of a car is a good way to help better the fuel economy and also improve handling at the same time.
  3. using low rolling resistance tires (tires were often made to give a quiet, smooth ride, high grip, etc., but efficiency was a lower priority). Tires cause mechanical drag, once again making the engine work harder, consuming more fuel. Hybrid cars may use special tires that are more inflated than regular tires and stiffer or by choice of carcass structure and rubber compound have lower rolling resistance while retaining acceptable grip, and so improving fuel economy whatever the power source.
  4. powering the a/c, power steering, and other auxiliary pumps electrically as and when needed ; this reduces mechanical losses when compared with driving them continuously with traditional engine belts.

These features make a hybrid vehicle particularly efficient for city traffic where there are frequent stops, coasting and idling periods. In addition noise emissions are reduced, particularly at idling and low operating speeds, in comparison to conventional engine vehicles. For continuous high speed highway use these features are much less useful in reducing emissions.

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 have an excellent improvement towards the environment when your dealing with air quality emissions, for those vehicles powered by fuel. This is a big step in the environmental impact of these vehicles. With an electric engine and a gasoline one, still shows that gasoline is not totally out of the picture. They still do contribute to a very small percent of the green house emissions due to the fact that they are still powered by petroleum based fuel which is used in other gasoline powered vehicles. Due to their small and lightweight size these current hybrid vehicles use less energy and fuel which puts out less emissions.[36] With the assistance of the electric motor the gasoline engine can be smaller (and therefore less polluting). Hybrid vehicles can reduce air emissions of smog-forming pollutants by up to 90% and cut carbon dioxide emissions in half.[37] Most of these vehicles are designed for commuting through cities, where there is an excessive amount of traffic to reduce the gas emissions and have a positive effect on the environment. 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.[38] Here is a link showing the amount of CO2 emissions, of hybrid vehicles compared to gasoline vehicles. [5]. There are also different pollution numbers when you are comparing different brands of hybrid vehicles. Some manufacturers of hybrid vehicles add this technology to their existing models, where as other manufacturers redesign their vehicles with this new technology. [6]

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: (1) nickel metal hydride, or (2) lithium ion; both 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.[39] 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.[40]. Nickel-based batteries are known carcinogens, and have been shown to cause a variety of teratogenic effects.[41].

The Lithium-ion battery has attracted attention due to its potential for use in hybrid electric vehicles. Hitachi is a leader in its development. What's more, 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.[42]

Raw materials increasing costs

There is an impending increase in the costs of many rare materials used in the manufacture of hybrid cars [43].

For example, the rare earth element dysprosium is required to fabricate many of the advanced electric motors and battery systems in hybrid propulsion systems [44][43]. Neodymium is another rare earth metal which is a crucial ingredient in high-strength magnets that are found in permanent magnet electric motors [7]

Nearly all the rare earth elements in the world come from China[45], and many analysts believe that an overall increase in Chinese electronics manufacturing will consume this entire supply by 2012.[43] In addition, export quotas on Chinese Rare Earth exports have resulted in a generally shaky supply of those metals [44][46].

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;[46] 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.

Other approaches include personal rapid transit, a public transportation concept that offers automated on-demand non-stop transportation, on a network of specially-built guideways.

See also

References

  1. ^ What is a Hybrid Vehicle? - An introduction to hybrid cars and how they are defined, with examples of different hybrid technologies
  2. ^ Clean Power Technology CESAR system
  3. ^ Biochar burner/stirling engine hybrid vehicle
  4. ^ "Das Powerbike (German), ISBN 3895951234". http://gso.gbv.de/DB=2.1/SET=1/TTL=1/SHW?FRST=1&PRS=HOL&HILN=888#888. Retrieved February 27, 2007. 
  5. ^ "Velomobile Seminar 1999, ISBN 3-9520694-1-8". http://www.futurebike.ch/page.asp?DH=2305. Retrieved January 11, 2006. 
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External links

Hybrid Automobile Manufacturers' Websites

Other Hybrid Links

Hybrid airplanes








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