Plug-in hybrid electric vehicle

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The number of US survey respondents willing to pay $4,000 more for a plug-in hybrid car increased from 17% in 2005 to 26% in 2006.

A plug-in hybrid electric vehicle (PHEV) is a hybrid which has additional battery capacity and the ability to be recharged from an external electrical outlet. In addition, modifications are made to the vehicle's control software. The vehicle can be used for short trips of moderate speed without needing the internal combustion engine (ICE) component of the vehicle, thereby saving fuel costs. In this mode of operation the vehicle operates as a pure battery electric vehicle with a weight penalty (the ICE). The long range and additional power of the ICE power train is available when needed.

PHEVs are commonly called "grid-connected hybrids," "gas-optional hybrids" (GO-HEVs), "full hybrids," and are sometimes called HEV-30 (for instance, to denote a hybrid with a 30-mile (50 km) electric range, compared to a HEV-0 (a non-plug-in hybrid). However, Ford, GM, and Toyota have all used the term "Full Hybrid Technology" to describe configurations that allow electric-only operation at low speeds (yet not PHEVs). Two other PHEV names used by a major U.S. automotive supplier and in a 1999 SAE paper are "energy hybrids" and "true hybrids." PHEVs can also operate in a mixed-mode where both gas and external electricity are used simultaneously to increase gas mileage for a particular range, usually at least double that of its electric-only range, but highly dependant upon the stage length between rechargings.

1 Types
2 Stranglehold on battery technology?
3 Advantages and disadvantages
4 Issues for wide-scale commercialization
5 Production models, prototypes and conversions
6 Battery electric vehicle
7 Vehicle-to-grid
8 External links
- 8.1 News
- 8.2 Related Groups
9 References

[edit] Types

Lithium-ion battery pack in the California Cars Initiative plug-in hybrid converted Toyota Prius, the PRIUS+

Some early non-production plug-in hybrid electric vehicle conversions have been based on the version of Hybrid Synergy Drive (HSD) found in the 2004+ model year Toyota Prius. Early Pba conversions by CalCars have demonstrated 10 miles (15 km) of EV-only and 20 miles (30 km) of double mileage mixed-mode range. A company offering conversions to consumers named Hybrids Plus is using A123 Li-ion batteries and has 15 or 30 miles of electric range. A company planning to offer conversions to consumers named EDrive systems will be using Valence Li-ion batteries and have 40-50 miles of electric range. Another company offering a plug-in module for the Toyota Prius is Hymotion. All of these systems replace the original battery and its ECU (Electronic Control Unit), while leaving the existing HSD system unchanged. This technology would be fairly simple to apply to other hybrid configurations. A conversion to plug-in mode involves increasing the capacity of the battery pack (in some cases the stock NiMH battery is retained), and adding an on-board AC powered charger to recharge the larger pack from mains power. Additionally, a method is required to encourage the vehicle to make full use the greater available electrical energy.

The cost of electricity for a Prius PHEV is about $0.03/mi ($0.019/km), based on 0.262 kWh / mile and a cost of electricity of 0.10 $ / kWh. Though the Honda Integrated Motor Assist (IMA) system does not have low-speed electric-only capability, mixed-mode mileage could be greatly enhanced while displacing some of their gasoline consumption with electricity from external sources. The Advanced Hybrid System 2 (AHS2) could be offered with additional battery capacity and charging capabilities as an option, costing about $3000 if offered by the manufacturer. Although it would likely be a substantial near-term financial burden, General Motors or DaimlerChrysler could potentially change the hybrid landscape by introducing a versatile and fuel-efficient PHEV. Meanwhile, Ford's chief engineers have suggested PHEVs are in their view technically suboptimal in that they use two complete powertrains.^{[citation needed]}

Current PHEV conversions install a higher capacity battery than common hybrids like the Toyota Prius in order to extend the range. This additional cost is offset by fuel operating cost savings because just $1.00 worth of electricity from the wall (at $0.09/kW·h) is sufficient to drive the same distance as a gallon of gasoline. During the year 2006, many government and industry researchers will focus on determining what level of all-electric range is economically optimum for the design.

While PHEV concepts and research have been neglected for many years by industry and government, strong interest is budding in 2006 to such a level that the architecture has even been included as an area of research in President George W. Bush's Advanced Energy Initiative. The "addiction to oil" mentioned in his 2006 State of the Union Address could be largely eliminated by PHEVs and this fact is the most dramatic advantage of the architecture. Although the technology exists today it is often classified by many to be in the initial research phases and likely to not be available for several years (largely due to patent protection to keep modern battery technology from use). ^{[citation needed]}

[edit] Stranglehold on battery technology?

The oil company Chevron controls key battery technologies and battery manufacturing facilities, through its subsidiary, Cobasys. According to the website ev1.org, during the development of the battery-electric vehicle (BEV) EV1, General Motors made a controlling investment in Ovonics's battery development and manufacturing, with particular interest in the patents and trade secrets controlling the manufacturing of large nickel-metal hydride (NiMH) batteries. This interest was subsequently sold to the oil company Texaco, which was acquired in its entirety by another oil company, Chevron. The "large format" NiMH batteries are no longer available to U.S. electric vehicle converters or lightweight BEV manufactures. The manufacturing unit, Cobasys, is currently declining to manufacture and market these batteries for battery electric automotive use in the US and has shut down (through patent control) Panasonic's large format battery importation to the US. The Cobasys web page concerning transportation applications addresses only large multi-passenger hybrid vehicles. In order to use NiMH batteries without violating Chevron's patents, hybrid automobile manufacturers are required to design vehicles which are at least 50% powered by gasoline; otherwise, they are limited to the use of "D" cell-sized NiMH ("small format") batteries. ^{[citation needed]}

[edit] Advantages and disadvantages

A 70-mile range HEV-70 may annually require only about 25% as much gasoline as a similarly designed HEV-0, depending on how it will be driven and the trips for which will be used. A further advantage of PHEVs is that they have potential to be even more efficient than their HEV-0 cousins because more limited use of the PHEV's internal combustion engines 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 likely operate far more often near its peak efficiency because it is not needed during transient operation conditions. These architectures would be highly likely to employ a parallel hybrid configuration whereby mechanical engine power is allowed to transfer most efficiently directly to the wheels (when the engine is activated).

PHEV and fully electric cars may allow for more efficient use of existing electric production capacity, much of which sits idle as operating reserve most of the time. This assumes that vehicles are charged primarily during off-peak periods (i.e., at night), or equipped with technology to shut off charging during periods of peak demand. There is debate about whether or not PHEV or electric vehicle technology reduces pollution or simply "shifts" the pollution to another physical location. The net effect on pollution is dependent on the fuel source of the electrical grid (fossil or renewable, for example) and the pollution profile of the powerplants themselves. Identifying, regulating and upgrading "single point" pollution source such as a powerplant -- or replacing a plant altogether -- may also be more practical. From a human health perspective, "shifting" pollution away from large urban areas may be considered a significant advantage.

Another advantage of the PHEV architecture is the synergy it offers with biofuels. It has long been understood that crop production in most countries is not sufficient to supply all of the biofuel needs of society, especially when food production is the obvious primary purpose. However, PHEVs dramatically reduce the requirement for liquid fuel to as little as 20% of an equivalent HEV-0. This produces a synergy between PHEVs and biofuels whereby extreme reductions in petroleum usage are possible. For example, E85 which is composed of 85% ethanol stretches petroleum by a factor of about 2.5 today. Combining E85 as the liquid fuel with a PHEV-70 results in a petroleum stetch factor of 10 (2.5 x 4). If an HEV-0 achieves 50 mpg U.S. (4.7 L/100 km), the similar PHEV-70 would develop 500 mpgp (0.47 L/100 km) (petroleum consumption) if fueled by E85.

Disadvantages include the weight and cost of a larger battery pack. The cost of a battery pack is especially relevant because with current technology battery packs are likely to need to be replaced before the car itself is replaced. Additionally, the mileage gain from a PHEV are highly dependent upon the way a vehicle is used, and the opportunities to recharge by plug. In the most extreme of circumstances a PHEV might get worse mileage than an HEV. For example, in a vehicle being used 24 hours a day for commercial purposes the larger battery capacity (as compared to an HEV) might lack any advantage, while the greater battery weight (than in a corresponding HEV) would reduce mileage.

[edit] Issues for wide-scale commercialization

Unlike a conventional hybrid electric vehicle current PHEV implementations use the full charge cycle of its battery, which reduces the life of the battery. Mass-produced Hybrid electric vehicles by design avoid a complete or near complete discharge of the battery. Some argue that current PHEV implementations aren't practical on a large scale because of reduced battery life, which is not true of commercial hybrids. However, see "Hybrid Vehicles Gain Traction", in the April 2006 issue of Scientific American, in which the authors argue that PHEVs will soon become standard in the automobile industry.

Here are the design issues and trade-offs that need to be solved:

Battery life, which should be sufficient to maintain at least 85 to 90 percent of initial operational capabilty for at least 150,000 miles (240,000 km)
Capacity to store electric energy. Affects vehicle weight, range, acceleration, and top speed. Energy density by weight for gasoline is 60-85 times higher than for a Lithium Ion battery so a 50 litre tank of gasoline (40 kg) carries as much energy as a Lithium Ion battery weighing 2400 kg or more. However internal combustion engines are vastly inefficient compared to electric motors.
Heat dissipation of larger capacity batteries, especially when batteries are fast charged, which may require active liquid cooling devices (these devices may double for cabin air cooling and heating)
Weight issues with increased batteries: slower acceleration, reduced gas mileage when used for long trips, increased strain on system components such as brakes, etc..., many of which can be addressed by appropriate system design such as increased regeneration capability (to save brakes), and larger electric motor (for acceleration).
Costs
Safety[1], owing to the greater total energy storage, but not significantly beyond that imposed by a conventional hybrid vehicle

For example, if the current Prius were made plug-in capable using its existing small battery pack its range would only be a few miles with low acceleration and low top speed. Alternately, using unsophisticated technology, a very heavy battery would be required which would cause other design problems. These limitations are expected to be resolved within a few years by employing modern batteries. To solve this one can:

Increase the number of batteries of the type currently use: Adds weight and only increases range mildly
Use the full charge/discharge of a battery: Reduces the life of the existing battery
Use alternative battery technology: Currently expensive, but under heavy research[2] [3] [4]. Life expectancy unknown but expected to be greater[5]. For lithium-ion (Li-ion) batteries Toyota reports a heat dissipation issue.[6][7]

The next major update to the Prius, perhaps in 2008 or later, is rumored to use Li-ion batteries[8]. This Guardian article suggests it will have a 15 km (9 mile) electric only range.[9]

[edit] Production models, prototypes and conversions

One production PHEV has gone on sale, the Renault Kangoo, in France in 2003. In addition, DaimlerChrysler is currently building PHEVs based on the Mercedes-Benz Sprinter van. Light Trucks are also offered by Micro-Vett SPA^[1] the so called Daily Bimodale.

A number of prototypes have been created. At the UC Davis Hybrid Center, a team led by Prof. Andy Frank (interview). have designed a working prototype that is currently being installed into a GM Equinox for the Challenge X competition. Team Fate. UC-Davis Hybrid Electric Vehicles Group. Retrieved on January 11, 2006. Some independent researchers have demonstrated conversions of vehicles such as the Toyota Prius, while leaving the majority of the stock Hybrid Synergy Drive intact and unchanged by simply adding battery capacity and a grid charger.

Press reports on Nov 29, 2006, indicate GM's plans to introduce a production plug-in hybrid version of Saturn's Greenline Vue SUV in 2009[10]to be a HEV-10 [11].

The California Cars Initiative, a non-profit advocacy and technology development group in California, has converted the '04 and newer Toyota Prius to become a prototype of what it calls the PRIUS+. With the addition of 130 kg (300 lb) of lead-acid batteries, the PRIUS+ achieves roughly double the gasoline mileage of a standard Prius and can make trips of up to 15 km (10 miles) using only electric power.^[2] It is now working with EDrive Systems, a new Southern California company that plans to install aftermarket conversions for Priuses with a target fuel efficiency of 1.0 L/100 km (230 mpg).

The Electric Power Research Institute of Palo Alto, along with a number of utilities and government agencies, is working with DaimlerChrysler to deliver three plug-in hybrids built on the Mercedes Sprinter platform (a 15-passenger van). The Electric Auto Association is sponsoring the EAA-PHEV project, a "Do-It-Yourself" approach to enable those who are comfortable working with high wattage DC systems to do their own conversion. Hymotion, a Canadian company, introduced plug-in hybrid upgrade kits in February 2006. Designed for the Toyota Prius and the Ford Escape and Mariner Hybrids, these kits will be offered to fleet buyers at first and should be available to the general public in 2007.

Motorcycle and small car manufacturer Suzuki has produced several prototype light sports cars capable of operation in this mode. The first of these used a 400 cc motorcycle engine to give a primarily electric vehicle a "limp home" capability. A subsequent model was more capable of general operation over a wide range of conditions and ranges.

[edit] Battery electric vehicle

A battery electric vehicle with a range extending trailer called a hybrid adapter might also be considered a plug-in hybrid. The pusher trailers or genset trailers are two working examples of this concept. About 15 kW of power is required to maintain freeway speeds in a lightweight EV. This is about one third the power output of the Honda Insight's 1 L three cylinder ICE. One advantage of this configuration is that the ICE or other energy conversion device can be tuned to maximize efficiency by running at an ideal constant power level.

[edit] Vehicle-to-grid

Another advantage of a gridable vehicle is their potential ability to load balance or help the grid during peak loads. By using excess battery capacity to send power back into the grid and then recharge during off peak using cheaper power such vehicles are actually advantageous to utilities as well as their owners. This is accomplished with what is known as V2G or Vehicle to Grid technology. Even if such vehicles just led to an increase in the use of night time electricity they would even out electricity demand (which is typically higher in the day time) and provide a greater return on capital for electricity infastructure.