Hybrid Synergy Drive and Hybrid electric vehicle
Toyota is one of the largest companies to push hybrid vehicles in the market and the first to commercially mass-produce and sell such vehicles, an example being the Toyota Prius. The company eventually began providing this option on the main smaller cars such as Camry and later with the Lexus divisions, producing some hybrid luxury vehicles. It labeled such technology in Toyota cars as "Hybrid Synergy Drive" and in Lexus versions as "Lexus Hybrid Drive."
The Prius has become the top selling hybrid car in America. Toyota, as a brand, now has three hybrid vehicles in its lineup: the Prius, Highlander, and Camry. The popular minivan Toyota Sienna is scheduled to join the hybrid lineup by 2010, and by 2030 Toyota plans to offer its entire lineup of cars, trucks, and SUVs with a Hybrid Synergy Drive option.
The Hybrid Synergy drive is the most widely rolled-out environment-friendly system in the automotive industry to date. More than 1,000,000 units have been sold. Toyota's CEO has committed to eventually making every car of the company a hybrid vehicle. .
Lexus LS 600h hybrid sedan.
Lexus also has their own hybrid lineup, consisting of the GS 450h, RX 400h, and launched in 2007, the LS 600h/LS 600h L.
Toyota has said it plans to make a hybrid-electric system available on every vehicle it sells worldwide sometime in the 2010s.
Toyota and Honda have already said they've halved the incremental cost of electric hybrids and see cost parity in the future (even without incentives).
After General Motors announced it would produce the Chevrolet Volt plug-in hybrid, Toyota announced that it, too, would make one. Toyota is currently testing its "Toyota Plug-in HV" in Japan, the United States, and Europe. Like GM's Volt, it uses a lithium-ion battery pack. The PHEV (plug-in hybrid electric vehicle) could have a lower environmental impact than existing hybrids.
On June 5, 2008, A123Systems announced that its Hymotion plug-in hybrid conversion kits for the Prius would be installed by six dealers, including four Toyota dealerships: Westboro Toyota in Boston, Fitzgerald Toyota in Washington D.C., Toyota of Hollywood in Los Angeles, and the Minneapolis-based Denny Hecker Automotive Group, which sells multiple brands.
Toyota is speeding up the development of vehicles that run only on electricity with the aim of mass-producing them in the early part of next decade. Road tests for the current prototype, called "e-com", had ended in 2006.[43]
Toyota Prius
Toyota might create a separate brand for Prius hybrids and is considering adding larger and smaller Prius models. Such Prius brand would be similar to Scion. Toyota is not planning separate dealerships for Prius.
Design and technology
The Prius is a combined hybrid (sometimes referred to as series-parallel), a vehicle that can be propelled by gasoline (petrol) and/or electric power. Components of the system include:
1. Regenerative braking, using motor-generators, which converts kinetic energy of motion into electrical energy that is stored in the traction battery and reduces wear on the brake pads;
2. A 1NZ-FXE internal combustion engine (ICE) using Atkinson cycle which is 12-14% more efficient than the more powerful Otto cycle. The gasoline engine normally shuts off during traffic stops and the accessories (including the air conditioning) are powered by the battery pack. The engine is used both to propel the vehicle and to recharge the batteries. Because of the availability of extra power from the electric motors for rapid acceleration the engine is sized smaller than usual for increased fuel efficiency and lowered emissions with acceptable acceleration; The penalty of the Atkinson cycle is low specific power, so the battery and generator is needed to give extra power when accelerating, whilst allowing the vehicle to cruise on the low powered engine, [49]
3. Two electric motor/generators: MG1 and MG2. MG1, reversible and up to 10,000 rpm, starts the engine and provides counter torque for the Continuously Variable Transmission (CVT). MG2 provides 50 kW (67 hp) between 1,200 to 1,540 rpm and 400 N·m (295 lb·ft) torque between 0 to 1,200 rpm, contributing to performance and economy. These motor-generators are used as generators when used for regenerative braking, and as motors are capable of starting the vehicle (and gas engine if needed) and low speed (<~30 mph (48 km/h), 41 mph (66 km/h) in NHW20) travel;
4. A Hybrid Synergy Drive (HSD) unit that combines a planetary gearset that behaves like a Continuously Variable Transmission (CVT) called the Power Split Device[50] to increase efficiency. The computer controlled HSD transaxle adjusts and blends the amount of power from the gasoline engine and electric motor-generator(s) as needed by the front drive wheels and rechargeable batteries;
5. A sealed 38-module nickel metal hydride (NiMH) battery pack providing 273.6 volts, 6.5 A·h capacity and weighing 53.3 kg (118 lb)[51] is supplied by Japan's Panasonic. They are normally charged to 40–60% of maximum capacity to prolong battery life as well as provide a reserve for regenerative braking;
6. Wind resistance is reduced by a drag coefficient of 0.26 (0.29 for 2000 model) with a Kammback design to reduce air resistance. Lower rolling-resistance tires are used to reduce road friction;
7. A vacuum flask for storing hot coolant when the vehicle is powered off for reuse so as to reduce warm-up time (US market);
8. An EV mode (or stealth mode) that allows drivers to operate on electric power only under low-power conditions for a limited duration of time (Europe and Asian markets, aftermarket in the US). Advocates for the blind warn that the Prius is silent, and that it could be hazardous to blind pedestrians and others accustomed to engine noise to warn of a nearby vehicle;
9. Vehicle weight is reduced by the use of a flexible resin gasoline tank and by the use of aluminum instead of steel for the engine bay hood and hatchback.
10. Starting with the 2010 model year (3rd generation), the gasoline engine uses an electric water pump, permitting an engine design with no serpentine belts, improving efficiency.
THS inverter unit (from NHW11)
The computer program used in the Prius shuts off the engine when the car is stopped, is reversing, or is descending hills, thereby dramatically decreasing fuel consumption in city driving . The HSD's on-board computer program determines when and how to use the engine, motor, or both to power the car and recharge the battery so as to maximize efficiency. Typically, a gasoline engine runs inefficiently at half-throttle, creating a choking condition called pumping loss, a major reason for the inefficiency of gasoline engines compared to diesels. The Prius minimizes pumping loss by using a high torque range as much as possible with the throttle fully open. Drive-by-wire throttle control technology and Toyota's Hybrid Synergy Drive (a torque combiner, electric drive, and computer control) are essential to this engine control. In addition to the immediate benefit of reducing fuel consumption and emissions, stopping the gasoline engine also improves the performance of the catalytic converter, as the exhaust gases from an idling engine tend to cool the catalyst below its optimal temperature.
Energy monitor on the 2005 Prius multi-function display (MFD), showing energy flow to/from the engine, battery, and from the regenerative braking, as well as battery charge level.
Hybrid Synergy Drive
Typical gasoline- or diesel-engined vehicles consume fuel when the vehicle is stopped, as is common in city driving. The Prius typically shuts down the gasoline engine and runs solely off the battery pack at low speeds and when stopped. A non-hybrid car also gets worse fuel consumption in city driving because its engine is continually used to accelerate the car to driving speed and then this energy is lost to friction brakes during stop-and-go driving. The Prius recaptures some of this energy by using regenerative braking to charge its battery pack while slowing down with its motor-generators in generator mode. For acceptable acceleration the IC engine on a "standard" car typically is much larger than needed for constant-speed travel, and is a relatively high power to rate weight ratio Otto cycle engine. By using both an Atkinson cycle gasoline engine, which whilst more efficient, has a much poorer power to weight ratio and an electric motors for acceleration the Prius engine can nevertheless be a smaller size and still provide acceptable acceleration [53]. This means such a hybrid are can have high fuel efficiency when cruising on the Atkinson cycle engine, and in city driving, though factors including driving style, air conditioning use, and short trips may offset some of this advantage. The frequent starting and stopping of the Prius engine does not cause noticeable additional wear and tear or emission problems because the electric drive motors have enough power to quickly spin the engine to optimal speed (around 1,000 rpm) before fuel is admitted.
Energy screen on the 2003 Prius
For any car, aerodynamic losses, which vary roughly as the velocity squared due to air drag are much greater on the highway than in low speed city driving. The Prius hybrid has less of an advantage in higher speed open road driving, typical of intercity driving. Nevertheless, the Prius still obtains improved fuel consumption under these circumstances since it can use a smaller and more efficient engine than would otherwise be required. The electric motor(s), powered by the battery pack, can provide the extra peak power needed for acceleration, passing and limited hill climbing. The lower weight, cross sectional area and lowest drag coefficient of a production car in the U.S. market make the Prius a very efficient highway traveler, getting 45 miles per US gallon (5.2 L/100 km; 54 mpg-imp) on the highway according to the U.S. EPA.
The environmental impact of the car's batteries has been questioned. To encourage battery recycling, dealers are paid a $200 fee for return of the car's batteries.[56] Toyota has laboratory reports that some Prius battery packs have lasted the equivalent of 180,000 miles (290,000 km). As the cars start to age, early reports have shown that in at least some cases the batteries can last in excess of 250,000 miles (400,000 km). Individual battery longevity will vary depending upon the treatment and use history of the battery pack. A degraded battery pack will reduce performance and fuel economy, but not leave the car inoperable.
[edit] Fuel consumption, CO2 emission, and airborne emissions
Monitor on a 2005 Toyota Prius MFD, displaying accumulative fuel economy for 59 miles (95 km) since last gas fill-up.
Fuel consumption, or fuel-efficiency in cars is generally measured as distance travelled per unit volume of fuel, as in miles per gallon (mpg), or as the volume of fuel required to cover a given distance, as in litres per 100 kilometres (L/100 km). Diesel fuel does have about an 11% higher energy density than gasoline (petrol), so that needs to be taken into account in pure energy-efficiency calculations and comparisons. Fuel-price-efficiency calculations will vary between various parts of the world, with diesel fuel pump prices being higher than gasoline prices in some countries, whilst in others it is less expensive than gasoline.
In the United States, the Environmental Protection Agency (EPA) test results must be posted on new vehicle windows, and are the only fuel consumption figures that can be advertised. EPA testing procedures for all vehicles were revised in 2007 in an attempt to better match what the average driver would achieve.[59] The following data is taken from these figures:
2008 Prius:
* 48 miles per US gallon (4.9 L/100 km; 58 mpg-imp) for city driving
* 45 miles per US gallon (5.2 L/100 km; 54 mpg-imp) for highway driving
* 46 miles per US gallon (5.1 L/100 km; 55 mpg-imp) combined
2001 Prius:
* 42 miles per US gallon (5.6 L/100 km; 50 mpg-imp) city driving
* 41 miles per US gallon (5.7 L/100 km; 49 mpg-imp) highway driving
The Prius is the most efficient car available in the U.S. in 2008, based on the official rating.
The official fuel consumption data, provided by the Department for Transport, rates the Prius as: 56.5 miles per imperial gallon (5.00 L/100 km; 47.0 mpg-US) urban, 67.3 miles per imperial gallon (4.20 L/100 km; 56.0 mpg-US) extra urban and 65.7 miles per imperial gallon (4.30 L/100 km; 54.7 mpg-US) combined. Eleven diesel-powered cars, some of them smaller, have a better fuel-efficiency (by fuel volume) than the Prius for combined use.
According to the Department for Transport, the Prius is tied with the MINI Cooper D as the third least CO2-emitting vehicles at 104 g/km, behind the tied Volkswagen Polo 1.4 TDI and SEAT Ibiza 1.4 TDI at 99 g/km - it is the least CO2-emitting petrol-powered car, the Polo and the Ibiza being diesel (being these city cars).
Independent test data and comparisons with other vehicles
Several organizations have tested the fuel economy of the Prius and compared it directly with other cars.
Consumer tests have shown that petrol-electric hybrid cars in general are a little more fuel-efficient (by fuel volume) than top of the range manual transmission diesels.[64] However, diesel fuel has a significantly higher energy density than the gasoline used by the Prius, and in some countries diesel is less expensive than gasoline, so overall diesel with manual transmission may be competitive with hybrid technology in some cases.
* January 2009: Edmunds.com compared the 2009 Prius to the all new 2010 Honda Insight. The Prius returned 54.4 MPG compared to the Insight's 51.5 MPG.
* September 2008: A Popular Mechanics comparison shows that the 2009 Volkswagen Jetta TDi diesel has slightly better highway fuel economy than the 2008 Prius with 45.4 MPG compared to 44.8 MPG. The Prius beats the Jetta in city fuel economy, however: 44.7 MPG compared to 32 MPG.
* August 2008: Edmunds.com test of Prius and Honda Fit, resulted in the Prius averaging 42 miles per US gallon (5.6 L/100 km; 50 mpg-imp). While the non-hybrid Fit averaged 28 miles per US gallon (8.4 L/100 km; 34 mpg-imp). The Honda Fit was priced $8,425 less in this test. Considering all vehicle factors, Edmunds.com awarded the overall win in this comparison by a narrow margin to the Honda Fit.
* June 2008: The Prius is the most fuel efficient car that Consumer Reports has tested[68] since the discontinuation of the 3-door Honda Insight. Consumer Reports gave a real-world fuel consumption rating of 44 miles per US gallon (5.3 L/100 km; 53 mpg-imp) for the Prius.
* May 2008: The Prius was the overall winner of the Edmunds.com "Gas-Sipper Smackdown" fuel economy test, winning three of the five tests. The 2005 VW Jetta TDI won the remaining two tests, but due to the higher cost of diesel the Jetta ranked third in fuel costs behind both the Prius and Smart Fortwo. The other car tested was the North American Ford Focus.
* March 2008: The UK's Sunday Times did a comparison of the Prius with another car in long distance town and country driving. The results showed that the other car, a BMW 520d SE with a 177 bhp (132 kW) diesel engine and regenerative braking, averaged 50.3 miles per imperial gallon (5.62 L/100 km; 41.9 mpg-US) whilst the Prius averaged 48.1 miles per imperial gallon (5.87 L/100 km; 40.1 mpg-US) over exactly the same route. The comparison was performed on a journey of 545 miles (877 km) from London to Geneva, including 100 miles (160 km) of urban driving, about 200 miles (320 km) of driving on rural roads, and about 200 miles (320 km) of motorway driving at speeds of up to 78 miles per hour (126 km/h) on one French autoroute.
* August 2007: UK's Auto Express magazine performed independent fuel efficiency tests, on public roads, on a number of hatchbacks, and in August 2007 published their list of the ten most efficient. The Prius achieved 10th place in the list, returning 41.5 miles per imperial gallon (6.81 L/100 km; 34.6 mpg-US). A Citroën C4 Coupé 1.6 HDi got 1st place with 49.6 miles per imperial gallon (5.70 L/100 km; 41.3 mpg-US).
* December 2005: Edmunds.com test of the Prius and Honda Civic Hybrid resulted in the Prius outperforming its competitor by an additional 4.5 mpg–U.S. (0.50 L/100 km / 5.4 mpg–imp) at 48.3 miles per US gallon (4.87 L/100 km; 58.0 mpg-imp).
* February 2005: In a Popular Mechanics magazine diesel versus hybrid comparison, the Prius outperformed the Volkswagen Jetta GL TDI diesel in both city and highway fuel economy.
* September 2004: Car and Driver tested the Prius along with the Honda Civic Hybrid, Toyota Echo, and Volkswagen Jetta TDI over three separate routes. The Prius yielded the best mileage on the highway and town routes, while tying the Echo for top spot on the suburban route.
* Motor Trend conducted a test comparing the Prius with a Honda Civic Hybrid. The Prius had the better fuel economy with 43.8 miles per US gallon (5.37 L/100 km; 52.6 mpg-imp) compared to 39.9 miles per US gallon (5.90 L/100 km; 47.9 mpg-imp) for the Civic.
Air Pollution
While CO2 emission is theorized to cause climate change, it does not pose a threat to health or create smog. In the United States the EPA measures a vehicle's air-borne pollution based on hydrocarbons, nitrogen oxides, carbon monoxide, particulate matter and formaldehyde before assigning them a score. In most states the NHW20 Prius is rated Tier II Bin 3. CARB also does its own emission scoring, the NHW20 Prius meets AT-PZEV certification in California and states that adopted CARB emission rules.
CO2 advertising claims
In the UK, the Advertising Standards Authority, an independent body charged with policing the rules of the advertising industry, ruled that a television advert for the Toyota Prius should not be broadcast again in the same form, having breached rules concerning misleading advertising. The advert claimed the Prius "emits up to one tonne less CO2 per year," while on-screen text included: "1 tonne of CO2 less than an equivalent family vehicle with a diesel engine. Average calculated on 20,000 km a year." Points of contention were the vehicles chosen for comparison, whether "up to one tonne less" adequately communicated that reductions could be lower, and whether the distance used was appropriate: 20,000 km per year is around a U.S. car's average annual driving distance, while a UK car's is 13,440 km.
An earlier complaint to the New Zealand Advertising Standards Authority, decision 03/360 2003 was also upheld. It was ruled that Toyota was in breach of the New Zealand advertising standards code of ethics, by claiming "up to 89% fewer smog forming emissions”. The figure was based on comparison with Euro 3 standards, which most new cars also met comfortably at the time.[citation needed]
Lifetime energy usage
The British Government and British media have requested Toyota release detailed figures for the energy use and CO2 emissions resulting from the building and disposal of the Prius. The UK Government Car Service runs 130 Priuses. Toyota has not supplied the detailed data they requested to support claims that the lifetime energy usage of the Prius (including the increased environmental cost of manufacture and disposal of the nickel-metal hydride battery) are outweighed by lower lifetime fuel consumption.[83] Toyota states that lifetime CO2 saving is 43 percent.
