Hybrid vehicle

For other types of hybrid transportation, see Hybrid vehicle (disambiguation).

Prius hybrid vehicle

Prius used by NYPD Traffic Enforcement

A hybrid vehicle is a vehicle that uses two or more distinct power sources to propel the vehicle. Power sources include:

• On-board or out-board rechargeable energy storage system (RESS)
• Gasoline or Diesel fuel
• Hydrogen
• Compressed air
• Human powered e.g. pedaling or rowing
• Wind
• Compressed or liquefied natural gas
• Solar
• Coal, wood or other solid combustibles

The term most commonly refers to hybrid electric vehicles (HEVs), which combine an internal combustion engine and one or more electric motors.

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 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.

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. [1]

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

Example of a typical "hybrid" is the new Canadian, Bombardier-built railroad engine called the AGC (Autorail à grande capacité, high-capacity railcar) which 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. [2]. The first operational prototype of a hybrid train engine with significant energy storage and energy regeneration capability has been introduced in Japan as the Kiha E200. It utilizes battery packs of lithium ion batteries mounted on the roof to store recovered energy. 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. Variants of typical diesel-electrical locomotives are like 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. Its unclear if dynamic braking (regenerative) power is recaptured for reuse; but in principle 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. "Green Goats" locomotives have been purchased by Canadian Pacific Railway, BNSF Railway, Kansas City Southern Railway and Union Pacific Railroad among others.

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. First systems are expected to be operational in 2007.

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, 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. FedEx and others are starting to invest in hybrid delivery type vehicles—particularly for city use where hybrid technology may pay off first. Since 2002, the U.S. military has been testing serial hybrid Humvees 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 engines were an early form of hybrid vehicles. 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.[3] [4] 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 flight and take-off.

Engine type

Hybrid electric-petroleum vehicles

Hybrid New Flyer Metrobus

File:Optare Solo Hybrid.jpg

Hybrid Optare Solo

Main article: Hybrid electric vehicle

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 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.

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 get as much as 75MPG and plans are still sold to this original design, and the "Mother Earth News" modified version on their website. The (PEV)plug-in-electric-vehicle is becoming more and more popular. It has the distance that we need in America and other locations with wide expanses with no services. You can plug in and charge the batteries as well as charge them when your on the go from the engine.

Continuously outboard recharged battery electric vehicle (CORBEV)

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 currassent 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, unfortunately 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)

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 (petroleum and biofuels) in one tank — typically gasoline and bioethanol or biobutanol, though diesel-biodiesel vehicles would also qualify.
• Dual mode: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.

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 . Under tests done by the EPA, a hydraulic hybrid Ford Expedition returned Template:Mpg City, and Template:Mpg highway. UPS currently has two trucks in service with this technology.

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 units and how they work

Parallel hybrid; electric & petroleum engine drive

Here, an electric motor and an internal combustion engine are installed so that they can both individually or together power the vehicle. Typical passenger car installations such as those from Toyota and Lexus use electric power for reversing, and low speed low throttle opening work because it uses less energy and does not require any energy while the car is idle, making hybrid vehicles ideal for urban and suburban environments. As the vehicle speed increases or the acceleration demanded is higher, the internal combustion engine starts and both power units work together in parallel (hence the name). Internal combustion engines deliver more power for a given motor weight, making them better suited for higher speeds. The installed electric motors and battery capacity may offer a range of 3-5km in pure electric mode, at speeds of up to 40km/h. Beyond this, the internal combustion engine is needed to either provide increased power or to re-charge the batteries.

The Toyota Prius and the Ford Escape Hybrid are examples of vehicles falling into this category.

On the open road, the primary power source is the internal combustion engine (partly to maximise the life of the batteries), but when maximum power is required, for example to overtake, the electric motor is used to maximise the available power for a short time, giving the effect of having a larger engine than that actually installed.

The fuel consumption benefits of a hybrid electric vehicle against an internal combustion vehicle of similar performance come through the recovery of braking energy, stored in the battery by the motor/generator for use at the next start which in a conventional vehicle would have been dissipated as heat from the brakes. Additionally, the ability to shut off the engine while the electic motor is running brings further savings. The larger the motor, and the battery, the more braking energy it can recover before conventional brakes are necessary to achieve the required retardation. However, a weight/space compromise determines the limits of energy recovery possible in a given installation.

Mild hybrid, electric assist

The second type uses a generally smaller electric motor only to assist the gasoline engine when it needs extra boost, again during brisk acceleration or when going up a hill. The Honda Civic Hybrid and Honda Insight fall into the second category. Futher examples are the recently announced Mercedes S and BMW 7-Series mild hybrids.

The main improvement in fuel consumption over a conventional vehicle with the same performance is possible by the installation of a smaller internal combustion engine, with smaller internal losses and lower weight. There are also savings through energy recovery through the motor/generator on the overrun and while decelerating. This electrical energy may be used to drive the a/c, power steering, and other auxiliaries electrically as and when needed as opposed to continuously with traditional belt-driven pumps, reducing mechanical losses and so improve the fuel consumption.

Manufacturers claim savings of approximately 15% fuel consumption against a conventional vehicle of similar performance.

The Smart Hybrid is a recently introduced city-car mild-hybrid.

Plug-in hybrid electrical vehicle (PHEV)

Main article: Plug-in hybrid

An addition to the hybrid market is the Plug-in Hybrid Electric Vehicle (PHEV). The PHEV usually consists of a gasoline-electric 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.

This concept is attractive to those seeking to minimise on-road emissions by avoiding - or at least minimising - 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 régimes 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 he/she 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.

Series Hybrid

A [series hybrid] uses electric drives powered by a single-speed internal combustion engine. While operating at its most efficient single speed, the combustion engine drives an electric generator instead of directly driving the wheels. This engine can do any combination of the following: charge a battery, charge a capacitor, directly power the electric motor. When large amounts of power and torque are required, the electric motor can draw electricity from a combination of batteries, capacitors, and the generator. A series hybrid does not require batteries in its design as a capacitor can act as a storage device.

There are three main options for series hybrid electric motors: Permanent Magnet, 3-Phase AC Induction, Multi-Phase AC Induction. Permament Magnet motors, like those found in the Prius, degrade in performance at higher temperatures and require a cooling system in the design. They allow for regenerative braking, and this comes with a safety trade off as any time there is motion by the magnets, they produce voltage. Permanent magnets also require rare earth which are expensive and difficult to source.

In contrast, 3-Phase AC Induction motors can be air cooled and therefore have better stamina, but have less power density which means that the weight saved from removing the cooling system is replaced with heavier and more complex gearing for the drivetrain. This more complex transmission gearing is also needed to compensate for the fact that a standard 3-Phase AC Induction motor can be either low-speed high-torque (like a standrd vehicles starter) or a high-speed low-torque (like a standrd vehicles alternator) but not both.

A Multi-Phase AC Induction motor (called a Chorus Motor) co-opts the harmonics that limit motor performance, which means a that it can smoothly change from behaving like a high-torque low-speed motor to behaving like a low-torque high-speed motor, without the need for efficiency robbing physical gearing that would be required to compensate for a 3-Phase AC Induction motors lower power density. The January 2009 issue of Motor Trend magazine discusses this third choice and its use in planes and vehicles. [5] Furthermore, by co-opting the harmonics that limit standard motor performance, greater torque can be generated by this motor; up to 10 times the torque of a standard motor. This extra torque can be generated for short 'burst' or 'startup' torque requirements, which means that the Chorus Motor used in a series hybrid can both be smaller and be sized for its 'average' torque requirements while still providing the acceleration torque needed for occasional circumstances like joining a highway from a dead stop. This motor is presently only being used in WheelTug™ and it's use turns an airplane into a series hybrid with a turbine in the APU generating the electricity needed to power the Chorus Motor in the WheelTug™

There are currently no series production plug-in hybrids, but GM, for example, with the Chevrolet Volt is pushing forward towards a series product introduction in 2-3 years.

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 gasoline (or diesel engine) and the electric motors for peak power needs resulting in a smaller gasoline or diesel engine sized more for average usage rather than peak power usage.
2. having significant battery storage capacity to store and reuse recaptured energy, especially in stop-and-go traffic.
3. recapturing significant amounts of energy normally wasted during braking etc. (regenerative braking) This is a mechanism that reduces vehicle speed by converting some of its kinetic energy into another useful form of energy, dependent upon the power rating of the motor/generator;

other techniques that are not necessarily 'hybrid' features, but that are frequently found fuel saving measures on hybrid vehicles include;

1. shutting down the gasoline or diesel engine during traffic stops or while coasting or other idle periods;
2. improving aerodynamics ; (part of the reason that SUVs get such bad gas mileage 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 gas mileage 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 carcase structure and rubber compound have lower rolling resistance while retaining acceptable grip, and so improving fuel economy whatever the power source.

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 gasoline or diesel powered 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 monoxide emissions.

Environmental impact of hybrid car battery

Main article: Electric vehicle battery

Though hybrid cars take in substantially 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). "Jim Kliesch, author of the 'Green Book: The Environmental Guide to Cars and Trucks' told HybridCars.com, '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.'"[6].Though substantially less toxic than conventional car batteries, nickel-based batteries are known carcinogens, and have been shown to cause a variety of teratogenic effects..

Although companies are funding research to use these safer less toxic batteries, the fact of the matter is lead is so cheap, and money always plays a factor when dealing with mass production of an item. According to a 2003 report entitled, "Getting the Lead Out," by Environmental Defense and the Ecology Center of Ann Arbor, Mich., an estimated 2.6 million metric tons of lead can be found in the batteries of vehicles on the road today. There's little argument that lead is extremely toxic. Scientific studies show that long-term exposure to even tiny amounts of lead can cause brain and kidney damage, hearing impairment, and learning problems in children. The auto industry uses over one million metric tons of lead every year, with 90% going to conventional lead-acid vehicle batteries. While lead recycling is a mature industry, it's impossible to rescue every car battery from the dump. More than 40,000 metric tons of lead are lost to landfills every year. According to the federal Toxic Release Inventory, another 70,000 metric tons are released in the lead mining and manufacturing process. [Jim Kliesch, author of the Green Book: The Environmental Guide to Cars and Trucks]

Raw materials shortage

There is an impeding shortage 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 [7]

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

Main article: Green vehicle § Types

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

List of hybrid vehicles Hybrid Locomotive Hybrid Vehicle Drivetrains Hybrid electric vehicle Global Hybrid Cooperation Plug-in hybrid Human-Electric Hybrid Vehicle Tribrid vehicle Hybrid buses Hybrid trucks

Alternative propulsion Bivalent (engine) Diesel-electric Efficient energy use Electric vehicle Global warming PNGV Solid oxide fuel cell

External links

• How Hydraulic Hybrids Work at HowStuffWorks
• Hybridization of Diesel powertrain in passenger cars
• Hybrids are now a smart buy on cost alone
• Information on Hydrogen Kits and how to convert your current vehicle to semi-hybrid one
• Research & Compare Hybrid Cars
• GM Hybrid Technology
• Lexus Hybrid Cars
• Toyota Hybrid Technology
• Ford Hybrid Car Technology
• Honda Hybrid Technology Site
• Plug-In Electric Hybrids and the Smart Grid
• Information Resource For Hybrid Cars
• Hybrids a wise choice, constantly improving

Hybrid airplanes

• The Future of Flight (Obese Pelicans to Shape-Shifting Switchblades)