30-05-2010, 11:57 PM
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Power
Power sources include:
On-board or out-board rechargeable energy storage system (RESS)
Gasoline or Diesel fuel
Hydrogen
Compressed air
Liquid nitrogen
Human powered e.g. pedaling or rowing
Wind
Compressed or liquefied natural gas
Solar
Waste heat from internal combustion engine. This can be converted to steam or electricity to increase vehicle propulsion. The extra power may also be used for supplemental systems
Coal, wood, Bio char or other solid combustibles
Electromagnetic fields, Radio waves
History
Hybrid vehicles were produced as early as 1899 by Lohner-Porsche. Early hybrids could be charged from an external source before operation. However, the term "plug-in hybrid" has come to mean a hybrid vehicle that can be charged from a standard electrical wall socket. The July 1969 issue of Popular Science featured an article on the General Motors XP-883 plug-in hybrid. The concept computer vehicle housed six 12-volt lead-acid batteries in the trunk area and a transverse-mounted DC electric motor turning a front-wheel drive. The car could be plugged into a standard North American 120 volt AC outlet for recharging.
In 2003, Renault began selling the Electric road, a plug-in series hybrid version of their popular Kangoo, in Europe. It was sold alongside Renault's "electricity" electric-drive Kangoo battery electric van. The Electric road had a 150 km (93 mi) range using a nickel-cadmium battery pack and a 500 cc (31 cu in), 16 kilowatt liquid-cooled gasoline "range-extender" engine. It powered two high voltage/high output/low volume alternators, each of which supplied up to 5.5 kW at 132 volts at 5000 rpm. The operating speed of the internal combustion engineâ€and therefore the output delivered by the generatorsâ€varied according to demand. The fuel tank had a capacity of 10 litres (2.6 US gal; 2.2 imp gal) and was housed within the right rear wheel arch. The range extender function was activated by a switch on the dashboard. The on-board 3.5 kilowatt charger could charge a depleted battery pack to 95% charge in about four hours from a 240 volts supply. Passenger compartment heating was powered by the battery pack as well as an auxiliary coolant circuit that was supplied by the range extender engine. After selling about 500 vehicles, primarily in France, Norway and the UK, at a price of about ‚¬25,000, the Electric road was redesigned in 2007.
Lithium-ion battery pack, with cover removed, in a Call Cars "PRIUS+" plug-in hybrid converted Toyota Prius converted by EnergyCS.
In September 2004, Call Cars converted a 2004 Toyota Prius into a prototype of what it called the PRIUS+. With the addition of 130 kg (300 lb) of lead-acid batteries, the PRIUS+ achieved roughly double the fuel economy of a standard Prius and could make trips of up to 15 km (9 mi) using only electric power. The vehicle, which is owned by Call Cars technical lead Ron Gremban, is used in daily driving, as well as a test bed for various improvements to the system.
On July 18, 2006, Toyota announced that it "plans to develop a hybrid vehicle that will run locally on batteries charged by a household electrical outlet before switching over to a gasoline engine for longer hauls." Toyota has said it plans to migrate to lithium-ion batteries in future hybrid models, but not in the next-generation Prius, expected in fall 2008. Lithium-ion batteries are expected to significantly improve fuel economy, and have a higher energy-to-weight ratio, but cost more to produce, and raise safety concerns due to high operating temperatures.
On November 29, 2006, GM announced plans to introduce a production plug-in hybrid version of Saturn's Greenline Vue SUV with an all-electric range of 10 mi (16 km). The model's sale is anticipated by fall 2009, and GM announced in january 2007 that contracts had been awarded to two companies to design and test lithium-ion batteries for the vehicle. GM has said that they plan on introducing plug-in and other hybrids "For the next several years".
In january 2007, GM unveiled the Chevrolet Volt, which is expected to initially feature a plug-in capable, battery-dominant series hybrid architecture which they are calling E-Flex. Future E-Flex plug-in hybrid vehicles may use gasoline, diesel, or hydrogen fuel cell power to supplement the vehicle's battery. General Motors envisions an eventual progression of E-Flex vehicles from plug-in hybrids to pure electric vehicles, as battery technology improves. General Motors presented the Volt as a PHEV-40 that starts its engine when 40% of the battery charge remains, and which can achieve a fuel economy of 50 mpg-US (4.7 L/100 km; 60 mpg-imp), even if the vehicle's batteries are not charged.
On July 9, 2007, Ford Motor Company CEO Alan Mutally said he expects Ford to sell plug-in hybrids in five to ten years, the launch date depending on advances in lithium-ion battery technology. Ford will provide Southern California Edison with 20 Ford Escape Hybrid sport utility vehicles reconfigured to work as plug-ins by 2009, with the first by the end of 2007.
On July 25, Japan's Ministry of Land, Infrastructure and Transport certified Toyota's plug-in hybrid for use on public roads, making it the first automobile to attain such approval. Toyota plans to conduct road tests to verify its all-electric range. The plug-in Prius was said to have an all-electric range of 13 km (8 mi). But later prototypes shown at the 2008 Paris Auto Show had an electric-only range of "just a little over six miles."
Technology
Series hybrids use an internal combustion engine (ICE) to turn a generator, which in turn supplies current to an electric motor, which then rotates the vehicleâ„¢s drive wheels. A battery or super capacitor pack, or a combination of the two, can be used to store excess charge. Examples of series hybrids include the Renault Kangoo Electric Road, Toyota's Japan-only Coaster light-duty passenger bus, Daimler AG's hybrid Orion bus, the Chevrolet Volt production car, the Opel Flex treme concept car, and many diesel-electric locomotives. With an appropriate balance of components this type can operate over a substantial distance with its full range of power without engaging the ICE. As is the case for other architectures, series hybrids can operate without recharging as long as there is liquid fuel in the tank.
Parallel hybrids, such as Honda's Insight, Civic, and Accord hybrids, can simultaneously transmit power to their drive wheels from two distinct sourcesâ€for example, an internal combustion engine and a battery-powered electric drive. Although most parallel hybrids incorporate an electric motor between the vehicle's engine and transmission, a parallel hybrid can also use its engine to drive one of the vehicle's axles, while its electric motor drives the other axle and/or a generator used for recharging the batteries. (This type is called a road-coupled hybrid). The Audi Duo plug-in hybrid concept car is an example of this type of parallel hybrid architecture. Parallel hybrids can be programmed to use the electric motor to substitute for the ICE at lower power demands as well as to substantially increase the power available to a smaller ICE, both of which substantially increase fuel economy compared to a simple ICE vehicle.
Series-parallel hybrids have the flexibility to operate in either series or parallel mode. Hybrid power trains currently used by Ford, Lexus, Nissan, and Toyota, which some refer to as series-parallel with power-split, can operate in both series and parallel mode at the same time. As of 2007, most plug-in hybrid conversions of conventional hybrids utilize this architecture.
Modes of operation
Regardless of its architecture, a plug-in hybrid may be capable of charge-depleting and charge-sustaining modes. Combinations of these two modes are termed blended mode or mixed-mode. These vehicles can be designed to drive for an extended range in all-electric mode, either at low speeds only or at all speeds. These modes manage the vehicle's battery discharge strategy, and their use has a direct effect on the size and type of battery required:
Charge-depleting mode allows a fully charged PHEV to operate exclusively (or depending on the vehicle, almost exclusively, except during hard acceleration) on electric power until its battery state of charge is depleted to a predetermined level, at which time the vehicle's internal combustion engine or fuel cell will be engaged. This period is the vehicle's all-electric range. This is the only mode that a battery electric vehicle can operate in, hence their limited range.
Blended mode is a kind of charge-depleting mode. It is normally employed by vehicles which do not have enough electric power to sustain high speeds without the help of the internal combustion portion of the power train. A blended control strategy typically increases the distance from stored grid electricity compared to a charge-depleting strategy. The Renault Kangoo and some Toyota Prius conversions are examples of vehicles that use this mode of operation. The Electricity and Electric road versions of the Kangoo were charge-depleting battery electric vehicles: the Electric road had a modest internal combustion engine which extended its range somewhat. Conversions of 2004 and later model Toyota Prius can only run without using the ICE at speeds of less than about 42 mph (68 km/h) due to the limits dictated by the vehicle's power train control software. However, at faster speeds electric power can still be used to displace gasoline, thus improving the fuel economy in blended mode and generally doubling the fuel efficiency.
Charge-sustaining mode is used by production hybrid vehicles (HEVs) today, and combines the operation of the vehicle's two power sources in such a manner that the vehicle is operating as efficiently as possible without allowing the battery state of charge to move outside a predetermined narrow band. Over the course of a trip in a HEV the state of charge may fluctuate but will have no net change. The battery in a HEV can thus be thought of as an energy accumulator rather than a fuel storage device. Once a plug-in hybrid has exhausted its all-electric range in charge-depleting mode, it can switch into charge sustaining mode automatically.
Vehicle type
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 in 1975. In 1994 Bernie McDonalds 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 proto type SH tricycles and quadri cycles.
Gasoline
Gasoline engines are used in most hybrid electric designs, and will likely remain dominant for the foreseeable future. While petroleum-derived gasoline is the primary fuel, it is possible to mix in varying levels of ethanol created from renewable energy sources. Like most modern ICE-powered vehicles, HEVs can typically use up to about 15% bio ethanol.
Manufacturers may move to flexible fuel engines, which would increase allowable ratios, but no plans are in place at present.
Hydrogen
Hydrogen fuel cells create electricity which is fed into an electric motor that drives the wheels. Adding regenerative breaking to increase efficiency is a no-brainer so all modern Hydrogen fuel cell vehicles are hybrids.
Bio fuels
Hybrid vehicles might use an internal combustion engine running on bio fuels, such as ethanol fuel or biodiesel. The Chevrolet Volt plug-in hybrid electric vehicle would be the first commercially available flex-fuel plug-in hybrid capable of adapting the propulsion to the bio fuels used in several world markets such as the ethanol blend E85 in the US, or E100 in Brazil, or biodiesel in Sweden.
Diesel
Diesel-electric HEVs use a diesel engine for power generation. Diesels have advantages when delivering constant power for long periods of time, suffering less wear while operating at higher efficiency. The diesel engine's high torque, combined with hybrid technology, may offer substantially improved mileage.
Most diesel vehicles can use 100% pure bio fuels (biodiesel), so they can use but do not need petroleum at all for fuel (although mixes of bio fuel and petroleum are more common, and petroleum may be needed for lubrication). If diesel-electric HEVs were in use, this benefit would likely also apply. Diesel-electric hybrid drive trains have begun to appear in commercial vehicles (particularly buses); as of 2007, no light duty diesel-electric hybrid passenger cars are currently available, although prototypes exist. Peugeot is expected to produce a diesel-electric hybrid version of its 308 in late 2008 for the European market.
At the Frankfurt Motor Show in September 2009 both Mercedes and BMW displayed diesel-electric hybrids
Robert Bosch GmbH is supplying hybrid diesel-electric technology to diverse automakers and models, including the Peugeot 308.
Electric machines
In split path vehicles (Toyota, Ford, GM, Chysler) there are two electical machines, one of which functions as a motor primarily, and the second functions as a generator primarily.
One of the primary requirements of these machines is that they are very efficient, as the electrical portion of the energy must be converted from the engine to the generator, through two inverters, through the motor again and then to the wheels. Therefore, any efficiency losses in the electric machines and inverters have a multiplication effect on the efficiency of the system.
Most of the electric machines used in hybrid vehicles are brushless DC motors (BLDC). Specifically, they are of a type called an interior permanent magnet (IPM) machine (or motor). These machines are wound similarly to induction machines found in a typical home, but use very strong rare earth magnets in the rotor. These magnets contain neodymium, iron and boron, and are therefore called NdFeB magnets. The magnet material is extremely expensive, and its cost is one of the limiting factors in the use of these machines.
Design considerations
In some cases, manufacturers are producing HEVs that use the added energy provided by the hybrid systems to give vehicles a power boost, rather than significantly improved fuel efficiency compared to their traditional counterparts.
The trade-off between added performance and improved fuel efficiency is partly controlled by the software within the hybrid system and partly the result of the engine, battery and motor size. In the future, manufacturers may provide HEV owners with the ability to partially control this balance (fuel efficiency vs. added performance) as they wish, through a user-controlled setting.
Fuel consumption
Current HEVs reduce petroleum consumption under certain circumstances, compared to otherwise similar conventional vehicles, primarily by using three mechanisms:
1. Reducing wasted energy during idle/low output, generally by turning the ICE off .
2. Recapturing waste energy (i.e. regenerative braking) .
3. Reducing the size and power of the ICE, and hence inefficiencies from under-utilization, by using the added power from the electric motor to compensate for the loss in peak power output from the smaller ICE.
Any combination of these three primary hybrid advantages may be used in different vehicles to realize different fuel usage, power, emissions, weight and cost profiles.
The ICE in an HEV can be smaller, lighter, and more efficient than the one in a conventional vehicle, because the combustion engine can be sized for slightly above average power demand rather than peak power demand. The drive system in a vehicle is required to operate over a range of speed and power, but an ICE's highest efficiency is in a narrow range of operation, making conventional vehicles inefficient. On the contrary, in most HEV designs, the ICE operates closer to its range of highest efficiency more frequently.
The power curve of electric motors is better suited to variable speeds and can provide substantially greater torque at low speeds compared with internal-combustion engines. The greater fuel economy of HEVs has implication for reduced petroleum consumption and vehicle air pollution emissions worldwide
Pollution
Reduced air pollution emissions, due to lower fuel consumption, lead improved human health with regard to respiratory problems and other illnesses. Pollution reduction in urban environments may be particularly significant due to elimination of idle-at-rest.
Battery toxicity is a concern, although today's hybrids use NiMH batteries, not the environmentally problematic rechargeable nickel cadmium. "Nickel metal hydride batteries are benign. They can be fully recycled," says Ron Cogan, editor of the Green Car Journal. Toyota and Honda say that they will recycle dead batteries and that disposal will pose no toxic hazards. Toyota puts a phone number on each battery, and they pay a $200 "bounty" for each battery to help ensure that it will be properly recycled.
Noise
Reduced noise emissions resulting from substantial use of the electric motor at idling and low speeds, leading to roadway noise reduction, in comparison to conventional gasoline or diesel powered engine vehicles, resulting in beneficial noise health effects (although road noise from tires and wind, the loudest noises at highway speeds from the interior of most vehicles, are not affected by the hybrid design alone).
Reduced noise may not be beneficial for all road users, as blind people or the visually-impaired consider the noise of combustion engines a helpful aid while crossing streets and feel quiet hybrids could pose an unexpected hazard. The U.S. Congress and the European Commission are exploring legislation to establish a minimum level of sound for electric and hybrid electric vehicles when operating in electric mode, so that blind people and other pedestrians and cyclists can hear them coming and detect from which direction they are approaching. Tests have shown that vehicles operating in electric mode can be particularly hard to hear below 20 mph (32 km/h).
Motorcycles
Companies such as Zero Motorcycles and Vectrix have market-ready all-electric motorcycles available now, but the pairing of electrical components and an internal combustion engine (ICE) has made packaging cumbersome, especially for niche brands .
Cycle Inc produces series diesel-electric motorcycles, with a top speed of 80 mph (130 km/h) and a target retail price of $5500.
Peugeot HYmotion3 compressor, a hybrid scooter is a three-wheeler that uses two separate power sources to power the front and back wheels. The back wheel is powered by a single cylinder 125 cc, 20 bhp (15 kW) single cylinder r motor while the front wheels are each driven by their own electric motor. When the bike is moving up to 10 km/h only the electric motors are used on a stop-start basis reducing the amount of carbon emissions.
SEMA has announced that Yamaha is going to launch one in 2010, with Honda following a year later, fueling a competition to reign in new customers and set new standards for mobility. Each company hopes to provide the capability to reach 60 miles (97 km) per charge by adopting advanced lithium-ion batteries to accomplish their claims.
These proposed hybrid motorcycles could incorporate components from the upcoming Honda Insight car and its hybrid power train.
Buses
Hybrid technology for buses has seen increased attention since recent battery developments decreased battery weight significantly. Drive trains consist of conventional diesel engines and gas turbines. Some designs concentrate on using car engines, recent designs have focused on using conventional diesel engines already used in bus designs, to save on engineering and training costs. Several manufacturers are currently working on new hybrid designs, or hybrid drive trains that fit into existing chassis offerings without major re-design. A challenge to hybrid buses may still come from cheaper lightweight imports from the former Eastern block countries or China, where national operators are looking at fuel consumption issues surrounding the weight of the bus, which has increased with recent bus technology innovations such as glazing, air conditioning and electrical systems. A hybrid bus can also deliver fuel economy though through the hybrid drive train. Hybrid technology is also being promoted by environmentally concerned transit authorities.
Trucks
In 2003, GM introduced a hybrid diesel-electric military (light) truck, equipped with a diesel electric and a fuel cell auxiliary power unit. Hybrid electric light trucks were introduced in 2004 by Mercedes Benz (Sprinter) and Micro-Vett SPA (Daily Bimodale). International Truck and Engine Corp. and Eaton Corp. have been selected to manufacture diesel-electric hybrid trucks for a US pilot program serving the utility industry in 2004. In mid 2005 Isuzu introduced the Elf Diesel Hybrid Truck on the Japanese Market.
They claim that approximately 300 vehicles, mostly route buses are using Hinos HIMR (Hybrid Inverter Controlled Motor & Retarder) system.
In 2007, high petroleum price means a hard sell for hybrid trucks and appears the first U.S. production hybrid truck (International Dura Star Hybrid).
Other vehicles are:
¢ Big mining machines like the Liebherr T 282B dump truck or Keaton Vandersteen Le Tourneau L-2350 wheel loader are powered that way. Also there was several models of BelAZ (7530 and 7560 series) in USSR (now in Belarus) since the middle of 1970th
¢ NASA's huge Crawler-Transporters are diesel-electric.
¢ Mitsubishi Fuso Canter Eco Hybrid is a diesel-electric commercial truck.
¢ Hino Motors (a Toyota subsidiary) has the world's first production hybrid electric truck in Australia (110 kW/150 hp diesel engine plus a 23 kW/31 hp electric motor).
Other hybrid petroleum-electric truck makers are DAF Trucks, MAN AG with MAN TGL Series, Nissan Motors and Renault Trucks with Renault Puncher.
Coca-Cola Enterprises has the largest hybrid electric trucks in North America. The hybrid electric tractors are the standard bulk delivery truck the company uses for large deliveries. CCE plans to incrementally deploy 185 of the hybrid electric trucks across the United States and Canada in 2009, bringing their total number of hybrid electric delivery trucks to 327, the largest such fleet in North America. The company already has 142 smaller hybrid electric delivery vehicles on the road. The trucks are powered by Eaton Corporation's hybrid electric drive train systems.
By a voice vote, the US Federal House approved H.R. 445, the Heavy Duty Hybrid Vehicle Research, Development, and Demonstration Act of 2009, authored by Rep. James Sensenbrenner.
Electric power storage
PHEVs typically require deeper battery charging and discharging cycles than conventional hybrids. Because the number of full cycles influences battery life, this may be less than in traditional HEVs which do not deplete their batteries as fully
. However, some authors argue that PHEVs will soon become standard in the automobile industry. Design issues and trade-offs against battery life, capacity, heat dissipation, weight, costs, and safety need to be solved. Advanced battery technology is under development, promising greater energy densities by both mass and volume, and battery life expectancy is expected to increase.
The cathodes of some early 2007 lithium-ion batteries are made from lithium-cobalt metal oxide. This material is expensive, and cells made with it can release oxygen if overcharged. If the cobalt is replaced with iron phosphates, the cells will not burn or release oxygen under any charge. The price premium for early 2007 conventional hybrids is about US$5000, some US$3000 of which is for their NiMH battery packs. At early 2007 gasoline and electricity prices, that would mean a break-even point after six to ten years of operation. The conventional hybrid premium could fall to US$2000 in five years, with US$1200 or more of that being cost of lithium-ion batteries, providing for a three-year payback. The payback period may be longer for plug-in hybrids, because of their larger, more expensive batteries.
Nickel-metal hydride and lithium-ion batteries can be recycled; Toyota, for example, has a recycling program in place under which dealers are paid a US$200 credit for each battery returned. However, plug-in hybrids typically use larger battery packs than comparable conventional hybrids, and thus require more resources. Pacific Gas and Electric Company (PG&E) has suggested that utilities could purchase used batteries for backup and load leveling purposes. They state that while these used batteries may be no longer usable in vehicles, their residual capacity still has significant value. More recently, General Motors (GM) has said it has been "approached by utilities interested in using recycled Volt batteries as a power storage system, a secondary market that could bring down the cost of the Volt and other plug-in vehicles for consumers."
Lithium iron phosphate (LiMPO4) is a class of cathode materials used in lithium iron phosphate batteries that is getting attention from the auto industry. Valence Technologies produce a Lithium Iron Manganese Phosphate (LiFeMgPO4) battery with LG Chem selling lithium iron phospate (LiFePO4) batteries for the Chevy Volt and A123 producing a Lithium Nano-phosphate battery.
In France, Électricité de France (EDF) and Toyota are installing charging stations for PHEVs on roads, streets and parking lots. EDF is also partnering with Elektromotive, Ltd. to install 250 new charging points over six months from October 2007 in London and elsewhere in the UK. Recharging points also can be installed for specific uses, as in taxicab stands.
Project Better Place began in October 2007 and is working with Renault on development of exchangeable batteries (battery swapping).
Ultra capacitors (or "super capacitors") are used in some plug-in hybrids, such as AFS Trinity's concept prototype, to store rapidly available energy with their high power density, in order to keep batteries within safe resistive heating limits and extend battery life. The Ultra Battery combines a super capacitor and a battery in a single unit, creating a hybrid car battery that lasts longer, costs less and is more powerful than current technologies used in plug-in hybrid electric vehicles (PHEVs).
The optimum battery size varies depending on whether the aim is to reduce oil consumption, running costs, or emissions, but a recent study concluded that "The best choice of PHEV battery capacity depends critically on the distance that the vehicle will be driven between charges. Our results suggest that for urban driving conditions and frequent charges every 10 miles or less, a low-capacity PHEV sized with an AER (all electric range) of about 7 miles would be a robust choice for minimizing gasoline consumption, cost, and greenhouse gas emissions. For less frequent charging, every 20-100 miles, PHEVs release fewer GHGs, but HEVs are more cost effective. "
Advantages
Energy resilience and petroleum displacement
Each kilowatt hour of battery capacity in use will displace up to 50 US gallons (190 l; 42 imp gal) of petroleum fuels per year (gasoline or diesel fuels). Also, electricity is multi-sourced and, as a result, it gives the greatest degree of energy resilience.
Fuel efficiency
Claimed fuel economy for PHEVs depends on the amount of driving between recharges. If no gasoline is used the MPG equivalent depends only on the efficiency of the electric system. A 120 km (70 mi) range PHEV-70 may annually require only about 25% as much gasoline as a similarly designed PHEV-0, depending on how it will be driven and the trips for which it will be used. The furthest all-electric range in a PHEV planned for mass production is the PHEV-60 BYD F6e.
A further advantage of PHEVs is that they have potential to be even more efficient than conventional hybrids because a more limited use of the PHEV's internal combustion engine may allow the engine to be used at closer to its maximum efficiency. While a Prius is likely to convert fuel to motive energy on average at about 30% efficiency (well below the engine's 38% peak efficiency) the engine of a PHEV-70 would be likely to operate far more often near its peak efficiency because the batteries can serve the modest power needs at times when the combustion engine would be forced to run well below its peak efficiency. The actual efficiency achieved depends on losses from electricity generation, inversion, battery charging/discharging, the motor controller and motor itself, the way a vehicle is used (its duty cycle), and the opportunities to recharge by connecting to the electrical grid.
The Society of Automotive Engineers (SAE) developed their recommended practice in 1999 for testing and reporting the fuel economy of hybrid vehicles and included language to address PHEVs. An SAE committee is currently working to review procedures for testing and reporting the fuel economy of PHEVs. The Toronto Atmospheric Fund tested ten retrofitted plug-in hybrid vehicles that achieved an average of 5.8 litres per 100 kilometre or 40.6 miles per gallon over six months in 2008, which was considered below the technology's potential.
In "real world" testing using normal drivers, some Prius PHEV conversions may not achieve much better fuel economy than HEVs. For example, a plug-in Prius fleet, each with a 30 miles (48 km) all-electric range, averaged only 51 mpg-US (4.6 L/100 km; 61 mpg-imp) in a 17,000-mile (27,000 km) test in Seattle, and similar results with the same kind of conversion battery models at Google.org. Moreover, the additional battery pack costs $10,000-11,000.
Military vehicles
The United States Army's manned ground vehicles of the Future Combat System all use a hybrid electric drive consisting of a diesel engine to generate electrical power for mobility and all other vehicle subsystems. However, with the current 2010 DOD budget all FCS land vehicles have been put on hold. Other military hybrid prototypes include the Millen works Light Utility Vehicle, the International FTTS, HEMTT model A3,and the Shadow RST-V.
Locomotives
In May 2003, JR East started test runs with the so called NE (new energy) train and validated the system's functionality (series hybrid with lithium ion battery) in cold regions.
In 2004, Rail power Technologies had been running pilots in the US with the so called Green Goats, which led to orders by the Union Pacific and Canadian Pacific Railways starting in early 2005.
Rail power offers hybrid electric road switchers, as does GE Diesel-electric locomotives may not always be considered HEVs, not having energy storage on board, unless they are fed with electricity via a collector for short distances (for example, in tunnels with emission limits), in which case they are better classified as dual-mode vehicles.
Battery technology
Main article: Patent encumbrance of large automotive NiMH batteries
Some battery formats and chemistries (NiMH batteries) suitable for use in PHEVs are tightly patented and have not been licensed for use by PHEV manufacturers, thereby slowing the development of new models. In any case, other NiMH[citation needed] and lithium ion-based batteries can be used instead.
