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Fuel economy-maximizing behaviors
Fuel economy-maximizing behaviors describe techniques that drivers can use to optimize their automobile fuel economy, and varies considerably from car to car. The behavior of drivers can have a significant impact on their fuel mileage, as most energy used by automobiles does not go toward acceleration of the vehicle and is, in that sense, wasted. In a frictionless world, no energy would be lost in travel. In reality, energy is lost in many ways, including engine inefficiency, aerodynamic drag, rolling friction, potential energy required to climb hills, and kinetic energy lost to braking (absent regenerative braking). The city mileage of conventional cars is much lower than highway mileage due to: 1) a high proportion of idling time, 2)operation mostly at very inefficient (grams fuel per kWh) low output regions of engine output map, 3) braking.[citation needed] TerminologyVarious government organizations encourage drivers to utilize fuel economy-maximizing driving techniques using various marketing labels. A few of these are:
Techniques used to maximize fuel economyPeople who maximize fuel economy have reported to use some of the following techniques:
One of the best ways to optimize mileage (both hybrid and non-hybrid) is to keep up with vehicle maintenance.[1] Key parameters to maintain are tire pressure, tire balance, and proper motor oil weight and level. Inflating tires to the maximum recommended air pressure ensures that less energy is required to move the car. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires per gas tank.[citation needed] Equally important is the proper maintenance of the Engine Control Module and all sensors it relies on to control engine operation such as oxygen sensors.
Beyond purchasing smaller vehicles, drivers can also increase fuel economy by minimizing the amount of luggage, tools, and equipment carried in the car, including such things as unneeded snow chains in the summer and outdoor sporting equipment in the winter.
This method is a trick that can be used with some hybrids to minimize internal combustion engine waste. The idea is to optimize acceleration in order to reach the optimal threshold of the hybrid engine. At this point, some vehicles (when the accelerator is minimally pressed) will glide consuming almost no power from gas or electric motors.[4]
Maintaining an efficient speed is also very effective in keeping mileage up.[1] Optimal efficiency can be expected while cruising with no stops, at minimal throttle and with the transmission in the highest gear. Every car has a different optimum speed, although it is usually reported to be in the range of 50-80mph. If your car has a fuel economy readout on the dashboard you can check your own car by cruising at different speeds (if safe and prudent to do so) and checking the readout. Acceleration should be quite gentle. Brakes are designed to dissipate energy and should be avoided whenever possible.
It is commonly believed that efficiency of a gasoline engine is related to the fuel's octane level, however this is not true in most situations. Octane is only a measure of the fuel's propensity to cause an engine to "ping", this ping is due to pre-detonation, pre-detonation is caused by the fuel burning too rapidly (before the piston reaches top dead center). Higher octane fuels burn more uniformly at high pressures (instead of burning nearly instantaneously across the mass, which is equivalent to "exploding"), thus produce less ping. For the vast majority of vehicles (i.e. vehicles with "standard" compression ratios), standard octane fuel will work fine and not cause pinging. Using high octane fuel in a vehicle that does not need it is simply wasting money. The only time high octane fuel is usually needed is for high compression performance cars. Even some performance cars have sensors that will automatically adjust the timing, when ping is detected, so low octane fuel can be used. In this limited situation, higher octane fuel will result in higher performance (with full-open throttle), but not necessarily fuel cost savings, since the high-octane is only needed with the throttle fully open. For other cars that have problems with ping, it may be due to a maintenance problem, such as carbon buildup inside the cylinder or incorrect spark plug tip length. In such cases, higher octane fuel may help, but this is an expensive fix, proper repair might make more long term sense. There is NO more energy in a gallon of high octane fuel, than low octane. Ping is very bad for an engine and if this condition exists, it will decrease fuel economy and will damage the engine in the long term.
While modern hybrids come with built-in trip computers which display real-time MPG, which helps the driver adjust driving habits, most gasoline powered vehicles do not have this as a standard option (although some luxury cars do). However, this information is available with an add-on device that connects to the car's onboard computer (post 1996 for most vehicles), such as the ScanGauge.[5]. This information is helpful in allowing the driver to see in real-time how driving techniques affect gas mileage.[1]
Autostop, forced stop, and draft-assisted forced stopSome hybrids must keep the engine running whenever the vehicle is in motion and the transmission engaged, although they still have an "auto-stop" feature which engages when the vehicle stops, avoiding waste. Maximizing use of autostop is critical on these vehicles because idling causes a severe drop in accumulated mileage (0 miles per gallon). In addition, many hypermilers will actually turn off their cars entirely (a "forced stop") or put them into neutral when going down hills or in other situations when momentum will carry the car on its own.[1] Draft-assisted forced stop, a variation of the forced (auto)stop (sometimes abbreviated as D-FAS), involves turning off the engine and gliding in neutral while tailgating a larger vehicle, in order to take advantage of the reduced wind resistance in its immediate wake (This practice is illegal in some areas due to its danger); while tailgating itself is inherently risky, the danger of collision is increased with D-FAS as power for power brakes can be lost after a few applications of the brake pedal and the pressure that causes power steering to function can be lost as well.[6]
Hybrid and electric enginesThe most effective commonly available hybrid vehicles in the hypermilage marathons are the Honda Insight Hybrid, the Toyota Prius Hybrid, and the Honda Civic Hybrid. Other hybrids have also done very well. Some historical non-hybrid vehicles such as the Honda Civic CR-X HF and the Smart Fortwo have also done remarkably well on mileage. The Toyota and Ford hybrids use two motor generators called a series-parallel hybrid with unique characteristics different from the single motor generators of the Honda and GM hybrids (as of January 2007). The Honda motor generator is integrated with the engine, the integrated motor assist (IMA) that enhances the low-end torque of the engine. The current GM hybrids turn-off the engine at a stop and restart it when ready to leave. The Toyota and Ford hybrids have a threshold speed—around 42 mph in the case of the Prius—above which the engine must run to protect the transmission system. Below this model-dependent speed, the car will automatically switch between either battery-powered mode or engine power with battery recharge. These hybrids typically get their best fuel efficiency below this model dependent threshold speed. Coasting can be achieved by using Neutral transmission range. The Honda IMA vehicles have a limited, battery-only, powered capability, although after-market modding has made the Insight capable of running in electric only-mode [1]. They achieve higher fuel economy [2]. Another way to save fuel includes turning off the engine on manual transmission vehicles when coasting. The GM hybrids have an engine auto-stop when halted. As of January 2007, they have no battery-only, powered capability. In late 2007, GM will introduce two two-mode hybrid, full-size SUVs, which can be powered by electric motors, V8 engines, or a combination of both. |
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HypermilingThis morning, while listening to NPR, I heard something about keeping your gas tank mostly full to avoid ethanol debris...or something like that. I didn't catch much of the report, so I went online searching for it. Instead, I got sidetracked by this fascinating story about hypermiler Wayne Gerdes. Here's a glimpse at his world of mileage efficiency:
Gerdes is no greener-than-thou rock star -- he commutes two hours to work -- but his efforts at getting 59 miles from his 2005 Honda Accord is admirable. Comical, too; his teenage son says he has to give Dad a 30-minute buffer to get him anywhere on time. I'm not saying we need to completely emulate Gerdes, especially when it comes to no A/C in a Houston summer and the illegal manuevering. But maybe following the speed limit wouldn't hurt. |
3
Getting more mileage is an art form
There are a lot of ways to ease up on the amount of gas you consume. Some people just prefer to do it by tailgaiting behind an 18-wheeler. Francesca Segre reports on the art of hypermiling. Hypermiler Wayne Gerdes (Marketplace Money)
TESS VIGELAND: This is Marketplace Money from American Public Media. I'm Tess Vigeland. Conventional wisdom says we'll soon hit four bucks a gallon for gas. Conventional wisdom has said that before, and been wrong. But even if we do cross that barrier, what are the odds we'll change our collective habits? Maybe we'll buy more hybrid cars. Maybe we'll carpool a little more. But here's another gas-saving idea that, frankly, I'd never heard of: Become a hypermiler. From the Marketplace Sustainability desk, Francesca Segre tells us it works -- even if you end up a little hyper yourself. FRANCESCA SEGRE: Wayne Gerdes makes a point of driving exactly the posted speed limit -- or slower. [SOUND: Horns honking] SEGRE: How often do you get the middle finger? WAYNE GERDES: Oh, maybe once every three days. But Gerdes isn't just slow, he's deliberate. And he's the best hypermiler in the world. Hypermiling? What's that you ask? It's the art of getting the most mileage out of every drop of gas in your tank. Gerdes never uses airconditioning, he takes alternative routes to avoid red lights -- stepping on the brakes just wastes gas in his estimation -- and he's known to tailgait 18-wheelers and let them pull him along. We just had a semi-pullaround, and I'm just using a little bit of his draft with my motor off as he's slowly backing away. I'm gonna move into the right lane, I'm gonna go into a ridge ride so I don't impede anybody. And we're going to get the maximum distance we can with the engine off in neutral, before we have to pulse up. Pulse up is his word for stepping on the gas, something else he tries to avoid. Seems like an awful lot of trouble to save a little fuel. But Gerdes saves more than a little. He says he's managed to get 59 miles-per-gallon out of his regular 2005 Honda Accord. Honda itself expects the Accord to get about 34 miles-per-gallon at best. Put Gerdes in a Prius, and he once recorded 127 miles-per-gallon. He squeezed 200 miles-per-gallon out of a Honda Insight hybrid. Gerdes says most American drive 15,000 miles per year - and that's some significant wear-and-tear on the pocketbook. SEGRE: Well the average driver, driving the average amount of miles, spends about $2,000 a year. And I think that with some of the basic techniques, they can increase that by almost 50 percent. So they'll be saving about $50 a month. Gerdes uses a fuel consumption display. That's a gadget he bought for 150 bucks. It's attached to his dash board to monitor his gas usage. He takes pictures of this fuel consumption display and posts those shots online to cleanmpg.com and other hypermiling websites. There, hundreds of other hypermiling enthusiasts brag about their fuel efficiency and swap ideas about improving technique. But Gerdes hasn't always been a slow-poke. He used to drive 75 miles per hour in the far left lane. Well, it had to do with when the World Trade Centers came down. That woke me up, and I'm surprised it didn't wake more of the people that were driving with today up. There is a direct correlation between our addiction to oil in the US and the world trade centers coming down through Osama Bin Laden and his group of Al-Qaeda. 19 seconds. America imports about 60 percent of its oil, and Gerdes didn't want to use any more gas than absolutely necessary. And he became more focused on reducing emissions, as he learned more about global warming. But then how exactly can he justify his two-hour commute to work? GERDES: Unfortunately I worked at nuclear plant that closed down, and I was offered another position that was 90 miles away. And my wife didn't want to move, so that forced me into driving a crazy amount of distance, unfortunately. I guess you could call me a hypocrite because I do burn a lot of gas, but I'm doing what I can to save and I'm trying teach others and reduce their carbon footprint. Gerdes's wife, Marian, admits hypermiling is a noble cause, that doesn't mean she likes driving with him. MARIAN GERDES: Now I just kinda shut my eyes and don't look. And the hypermiling tests his 14-year-old son's patience too. WAYNE'S SON: If I ask Dad to drive, I tell him I have to be there like 30 minutes earlier than I do or something. Illinois State Police Trooper Clare Pfotenhauer says hypermiling techniques can also be illegal. CLARE PFOTENHAUER: I think he's insane. And if he's caught doing one of his daredevil moves - like drafting behind an 18-wheeler - he could get charged with three moving violations. Including impeding the flow of traffic. Trooper Pfotenhauer says convictions come with hefty fines - and he could lose his license for a year. PFOTENHAUER: Now that money that you tried to save in gas, it just cost you, it maybe even cost you a little bit more. In fact, Gerdes says he's been pulled over a couple of times. The first time it was during a hypermiling road race. GERDES: We got pulled over in Ohio for goin too slow. And I think that he thought we were drunk. But Gerdes is not deterred. He encourages everyone to drive at the speed limit Increase their tire pressure and use their brakes as little as possible He says that alone can improve your fuel economy by 20 to 25 percent. He insists anyone can do it, you just gotta slow down. |
Petroleum electric hybrid vehicle
A Petroleum Electric Hybrid Vehicle (PEHV) is a
vehicle using an on-board
rechargeable energy storage system (RESS) and a fueled power source
for vehicle
propulsion. The HV pollutes less and uses less fuel during its useful
life. The different propulsion power systems may have common subsystems or
components. The HV provides better fuel economy than a conventional
vehicle because the engine is smaller and may be run at speeds providing
more efficiency. Other techniques may be used to recover or reduce waste
energy (such as regenerative braking and shutting down the combustion
engine). PHEVs most commonly use internal combustion engines and electric batteries to power electric motors. Modern mass-produced hybrids prolong the charge on their batteries by capturing kinetic energy via regenerative braking. As well, when cruising or in other situations where just light thrust is needed, "full" hybrids can use the combustion engine to generate electricity by spinning an electrical generator (often a second electric motor[1]) to either recharge the battery or directly feed power to an electric motor that drives the vehicle. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrids still require gasoline and diesel as their sole fuel source though other fuels such as ethanol or plant based oils have also seen occasional use. The term hybrid when used in relation with cars also has other uses. Prior to its modern meaning of hybrid propulsion, the word hybrid was used in the United States to mean a vehicle of mixed national origin; generally, a European car fitted with American mechanical components. This meaning has fallen out of use. In the import scene, hybrid was often used to describe an engine swap. Some have also referred to flexible-fuel vehicles as hybrids because they can use a mixture of different fuels — typically gasoline and ethanol alcohol fuel.
HistoryIn 1898 Ferdinand Porsche designed the Lohner-Porsche carriage, a series-hybrid vehicle that broke several Austrian speed records, and also won the Exelberg Rally in 1901 with Porsche himself driving. Over 300 of the Lohner-Porsche carriages were sold to the public. However this is more an example of electrical transmission than a hybrid vehicle. The 1915 Dual Power made by the Woods Motor Vehicle electric car maker had a four cylinder internal combustion engine and an electric motor. Below 15 mph (25 km/h) the electric motor alone drove the vehicle and above this speed the "main" engine cut in to take the car up to its 35 mph (55 km/h) top speed. About 600 were made up to 1918. [2] There have also been air engine hybrids where a small petrol engine powered a compressor. Several types of air engines also increased the range between fill-ups with up to 60% by absorbing ambient heat from its surroundings.[3] In 1959 the development of the first transistor-based electric car—the Henney Kilowatt—heralded the development of the electronic speed control that paved the way for modern hybrid electric cars. The Henney Kilowatt was the first modern production electric vehicle and was developed by a cooperative effort between National Union Electric Company, Henney Coachworks, Renault, and the Eureka Williams Company. Although sales of the Kilowatt were dismal, the development of the Kilowatt served was a historical "who's who" of electric propulsion technology. A more recent working prototype of the electric-hybrid vehicle was built by Victor Wouk (one of the scientists involved with the Henney Kilowatt and also brother of author Herman Wouk ). Wouk's work with electric hybrid vehicles in the 1960s and 1970s earned him the title as the "Godfather of the Hybrid"[4]). Wouk installed a prototype electric-hybrid drivetrain into a 1972 Buick Skylark provided by GM for the 1970 Federal Clean Car Incentive Program, but the program was killed by the EPA in 1976 while Eric Stork, the head of the EPA at the time, was accused of a prejudicial coverup[5]. Since then, hobbyists have continued to build hybrids but none was put into mass production by a major manufacturer until the waning years of the twentieth century. The regenerative-braking hybrid, the core design concept of most production hybrids, was developed by Electrical Engineer David Arthurs around 1978 using off-the shelf components and an Opel GT. However the voltage controller to link the batteries, motor (a jet-engine starter motor), and DC generator was Mr. Arthurs'. The vehicle exhibited ~75 mpg fuel efficiency and plans for it (as well as somewhat updated versions) are still available through the Mother Earth News web site. The Mother Earth News' own 1980 version claimed nearly 84 mpg. The Bill Clinton administration initiated the Partnership for a New Generation of Vehicles (PNGV)[6] program in September 29, 1993 that involved Chrysler, Ford, General Motors, USCAR, the DoE, and other various governmental agencies to engineer the next efficient and clean vehicle. The NRC cited automakers’ moves to produce hybrid electric vehicles as evidence that technologies developed under PNGV were being rapidly adopted on production lines, as called for under Goal 2. Based on information received from automakers, NRC reviewers questioned whether the “Big Three” would be able to move from the concept phase to cost effective, pre-production prototype vehicles by 2004, as set out in Goal 3.[7] The program was replaced by the hydrogen focused FreedomCAR initiative[8] of George W. Bush's administration in 2001. The focus of the FreedomCAR initiative being to fund research too high risk for the private sector to engage in with the long term goal of developing emission / petroleum free vehicles. In the intervening period, the widest use of hybrid technology was actually in diesel-electric locomotives. It is also used in diesel-electric submarines, which operate in essentially the same manner as hybrid electric cars. However, in this case the goal was to allow operation underwater without consuming large amounts of oxygen, rather than economizing on fuel. Since then, many submarines have moved to nuclear power, which can operate underwater indefinitely, though a number of nations continue to rely on diesel-electric fleets. Automotive hybrid technology became successful in the 1990s when the Honda Insight and Toyota Prius became available. These vehicles have a direct linkage from the internal combustion engine to the driven wheels, so the engine can provide acceleration power. The 2000s saw development of plug-in hybrid electric vehicles (PHEVs), which can be recharged from the electrical power grid and do not require conventional fuel for short trips. The Renault Kangoo was the first production model of this design, released in France in 2003. However, the environmental benefits of plug-in hybrids depend somewhat on the source of the electrical power. In particular, electricity generated with wind would be cleaner than electricity generated with coal, the most polluting source. On the other hand, electricity generated with coal in a central power plant is still much cleaner than pure gasoline propulsion, due to the much greater efficiencies of a central plant. Furthermore, coal is only one source of centrally generated power, and in some places such as California is only a minor contributor, overshadowed by natural gas and other cleaner sources. The Prius has been in high demand since its introduction. Newer designs have more conventional appearance and are less expensive, often appearing and performing identically to their non-hybrid counterparts while delivering 50% better fuel efficiency. The Honda Civic Hybrid appears identical to the non-hybrid version, for instance, but delivers about 50 US mpg (4.7 L/100km). The redesigned 2004 Toyota Prius improved passenger room, cargo area, and power output, while increasing energy efficiency and reducing emissions. The Honda Insight, while not matching the demand of the Prius, is still being produced and has a devoted base of owners. Honda has also released a hybrid version of the Accord. 2005 saw the first hybrid sport utility vehicle (SUV) released, Ford Motor Company's Ford Escape Hybrid. Toyota and Ford entered into a licensing agreement in March 2004 allowing Ford to use 20 patents from Toyota related to hybrid technology, although Ford's engine was independently designed and built. In exchange for the hybrid licences, Ford licensed patents involving their European diesel engines to Toyota. Toyota announced model year 2005 hybrid versions of the Toyota Highlander and Lexus RX 400h with 4WD-i which uses a rear electric motor to power the rear wheels negating the need for a differential. Toyota also plans to add hybrid drivetrains to every model it sells in the coming decade. For 2007 Lexus offers a hybrid version of their GS sport sedan dubbed the GS450h with "well in excess of 300hp". The 2007 Camry Hybrid becomes available starting Summer 2006 in USA and Canada. The initial batch of Camry Hybrids are built in Japan; starting October 2006, Toyota Motor Manufacturing, Kentucky (TMMK) will also produce these hybrids. Also, Nissan announced the release of the Altima hybrid (technology supplied by Toyota) around 2007. An R.L. Polk survey of 2003 model year cars showed that hybrid car registrations in the United States rose to 43,435 cars, a 25.8% increase from 2002 numbers. California, the nation's most populous state at one-eighth of the total population, had the most hybrid cars registered: 11,425. The proportionally high number may be partially due to the state's higher gasoline prices and stricter emissions rules, which hybrids generally have little trouble passing. Honda, which offers Insight, Civic and Accord hybrids, sold 26,773 hybrids in the first 11 months of 2004. Toyota has sold a cumulative 306,862 hybrids between 1997 and November 2004, and Honda has sold a total of 81,867 hybrids between 1999 and November 2004.[9] Hybrids currently available
Automobiles and light trucksA number of manufacturers currently produce hybrid automobiles and light trucks, including Ford, General Motors, Honda, Mazda, Nissan, Peugeot, Renault and Toyota. For a more complete list, see Production hybrid vehicles (organized by manufacturer). Trains, trucks and busesIn May 2003 JR East started test runs with the so called NE (new energy) train and validated the system's operability (series hybrid with lithium ion battery) in cold regions. In 2004, RailPower 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[1],[2],[3]. Also in 2005 GE introduced its hybrid shifters on the market. Toyota claims to have started with the Coaster Hybrid Bus in 1997 on the Japanese market. In May 2003 GM started to tour with hybrid buses developed together with Allison. Several hundreds of those buses have entered into daily operation in the US. The Blue Ribbon City Hybrid bus was presented by Hino, a Toyota affiliate, in January 2005. In 2003 GM introduced a diesel hybrid military (light) truck, equipped with a diesel electric and a fuel cell auxiliary power unit. Hybrid light trucks were introduced 2004 by Mercedes (Hybrid 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. New Flyer and Gillig produce hybrid buses using either ISE Corporation ThunderVolt or Allison's electric drive system. The Whispering Wheel bus is another hybrid. A promising but as-yet unseen application for hybrid vehicle technology would be in garbage trucks, since these vehicles do stop-start driving and often stand idling. LocomotivesRailpower[10] offers hybrid road switchers, as does GE.[11] Diesel-electric locomotives may not always be considered hybrids, 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. Other military vehiclesThe 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. TaxicabsHybrid technology may be particularly appropriate for use as taxicabs, as in many locations they are used in predominantly urban environments; have intensive operating schedules, maximizing fuel savings over the life of the vehicle; and may spend considerable periods of time at idle, where the hybrid engine may allow for the combustion engine to be shut off (while retaining use of electrical accessories). Hybrid taxicabs are primarily based on production passenger vehicles, with modifications (often aftermarket) to meet specialized usage requirements and/or local regulations (security features, for example). Since vehicles in taxicab service may operate for 10-20 hours per day, the reduction in local pollution and noxious emissions may be more significant than that achieved by hybrids in private vehicle use. In 2005, New York City added six Ford Escape Hybrids to their taxi fleet and city officials said the entire fleet of 13,000 vehicles could be converted within five years.[12] Types
Series hybrid vehicle 
Parallel hybrid vehicle There are many ways to create an electric-internal combustion hybrid. The variety of electric-ICE designs can be differentiated by the structure of the powertrain, the degree of hybridization and the mode of operation. The main categories are series hybrids and parallel hybrids, with combined hybrids having common characteristics of series and parallel designs. Hybrids other than electric-internal combustion exist, for example hydraulic and pneumatic hybrids, where compressed fluids and compressed air, respectively, are used for energy storage with regenerative braking. Engines and fuel sourcesGasolineGasoline engines are used in most hybrid 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, hybrids can typically use up to about 15% bioethanol. Manufacturers may move to flexible fuel engines, which would increase allowable ratios, but no plans are in place at present. Nowadays petroleum gasoline engines can use directly biobutanol (see direct biofuel). DieselOne potentially interesting hybrid vehicle combination uses 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 performance in a car of over 100 mpg US (2.35 litres/100 km). Most diesel vehicles can use 100% pure biofuels (biodiesel), so they can use but do not need petroleum at all; if diesel-electric hybrids were in use, this benefit would likely also apply. Diesel-electric hybrids with parallel drivetrains like the Prius may have a substantial cost disadvantage to other options. Diesel engines are generally more expensive than gasoline equivalents, due to the demands for higher compression (although this also makes diesels more durable). If this "diesel premium" is added to any additional expense for the hybrid, the diesel-electric combination may make the payback period for such vehicles even longer and less feasible for many consumers. In addition, the higher torque of diesel engines may obviate one of the advantages of the electric motors. As with regular diesel engines, diesel-electric hybrids may be more appropriate for high-mileage, intensive-use applications, such as buses, trucks, and delivery vehicles, and less appropriate for passenger vehicles. In addition, regular diesel vehicles may get similar mileage to gasoline-electric hybrids, for a smaller premium, and the marginal benefit of "hybridization" may not be viable. Diesels are not widely used for passenger cars in the United States, as US diesel fuel has long been considered very "dirty", with relatively high levels of sulfur and other contaminants in comparison to the Eurodiesel fuel in Europe, where greater restrictions have been in place for many years. Despite the dirtier fuel at the pump, the US has tough restrictions on exhaust, and it has been difficult for car manufacturers to meet emissions levels as higher sulfur levels are damaging to catalytic converters and other emission control systems. However, ultra-low sulfur diesel was mandated and became widely available in the U.S. in October 2006 for highway vehicles, which will allow the use of newer emissions control systems. Diesel-electric motors are common for use as locomotives, but using a serial hybrid design. In locomotives, the diesel engine is used to generate electricity for the electric drivetrain. This configuration allows the internal combustion engine to be operated at more efficient operating parameters, while removing the need for a separate transmission for the ICE unit and allowing the efficient delivery of torque from the electric motors. Such a system may need a smaller diesel engine and allow for better emissions controls, since the operating range of the diesel engine would be optimized for electric generation rather than power delivery through the mechanical transmission and wheels. There have been studies of this type of diesel-electric hybrid, but there are no confirmed attempts to commercialize such a vehicle for passenger use. PSA Peugeot Citroën has unveiled two demonstrator vehicles featuring a diesel-electric hybrid powertrain: the Peugeot 307 and Citroën C4 Hybride HDi (PDF). VW made a prototype diesel-electric hybrid car that achieved 2 litres/100 km (118 mpg US) fuel economy, but has yet to sell a hybrid vehicle. General Motors has been testing the Opel Astra Diesel Hybrid. There have been no concrete dates suggested for these vehicles, but press statements have suggested production vehicles would not appear before 2009. 
Hybrid Orion VI Metrobus So far, production diesel-electric engines have mostly just appeared in mass transit buses. Current manufacturers of diesel-electric hybrid buses include New Flyer Industries, Gillig, Orion Bus Industries, and North American Bus Industries. In 2008, NovaBus will add a diesel-electric hybrid option as well. Benefits
Median mpg (US) with boxplot from GreenHybrid.com This image has an uncertain copyright status and is pending deletion. You can comment on the removal. Benefits of the hybrid design include:
IncentivesIn order to encourage the purchase of hybrid vehicles, several incentives have been made into law: United States
Canada
United Kingdom
Trade-offsIn some cases, manufacturers are producing hybrid vehicles 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.[16] The trade-off between added performance and improved fuel efficiency is mainly something controlled by the software within the hybrid system. In the future, manufacturers may provide hybrid-owners with the ability to set this balance (fuel efficiency vs. added performance) as they wish, through a user-controlled setting.[17] Toyota announced in January, 2006 that it was considering a "high-efficiency" button. It has been observed that the success of the hybrid systems comes despite the need to carry two complete power systems. In a poorly designed car this might increase the weight and size and therefore greater losses in acceleration and aerodynamic drag, although the Prius is lighter and more aerodynamic than many other cars. In fact, the relative desirability of this concept rests on the deficiencies of the two underlying systems: the unfavorable torque curve of the internal combustion engine, referred to above, and the lack of a system of storing and delivering electrical power with anything near the energy density of combustible liquid fuels, so that a fuel tank, internal combustion engine, and generator together still represent a better source of electrical power than the equivalent weight and volume of batteries. In the event of relatively large leaps forward in battery or fuel cell technology, the internal combustion portion of the hybrid will become superfluous. Somewhat less likely is the possibility of a change in the general popular mode of automobile use largely supplanting short trips by use |