An introduction by the U.S. Department of Energy to commercially available advanced vehicle technologies

OFFICE

OF ENERGY EFFICIENCY RENEWABLE ENERGY

featuring the

Toyota Prius

Whats Inside.

What Is a Hybrid Electric Vehicle? Why the Prius? How Does the Prius Compare with Conventional Vehicles?
U.S. Department of Energy Technology Snapshot Featuring the Toyota Prius
Welcome to the Clean Cities Advanced Vehicle Information Series
Dear Reader, Twenty-first century transportation is not just a vision for the future its here today. Clean, fuel-efficient hybrid electric vehicles (HEVs) are now available, joining the alternative fuel vehicles already on the road. You may have seen HEVs in the news, at your local dealership, and even in your neighborhood. This brochure is the first of the U.S. Department of Energys (DOEs) Technology Snapshots, a suite of publications in the Clean Cities Advanced Vehicle Information Series that is designed to introduce the latest commercially available vehicle technologies to consumers across the country. Each Snapshot features a different vehicle and offers an objective, plain English explanation of how it works and how it differs from conventional vehicles. The web sites listed on the back cover of this brochure provide additional information about advanced transportation technology programs. Although nothing can compare to sitting behind the wheel, each Snapshot gives you a feel for the featured vehicle by highlighting performance, vehicle safety, and the benefits the new technology delivers to you and your community. Are you ready to drive a cleaner, greener and more fuel-efficient vehicle?
What Is a Hybrid Electric Vehicle?
A hybrid is any vehicle that uses two or more sources of power in todays HEVs, the two sources are electricity (from batteries) and mechanical power (from a small internal combustion engine). HEVs can offer the very low emissions of electric vehicles with the power and range of gasoline vehicles. They also offer up to 30 more miles per gallon, perform as well as or better than, and are just as safe as any comparable gasoline-powered car and they never have to be plugged in for recharging. Widespread use of HEVs would help reduce our nations growing dependence on foreign oil and cut greenhouse gas emissions by one-third to one-half.

How Do HEVs Work?

Hybrids can offer tremendous fuel economy and emissions benefits because they operate differently than conventional gasoline-fueled vehicles. Gasoline Vehicle: The heat energy obtained by burning gasoline powers the engine, which drives the transmission that turns the wheels. Electric Vehicle: A set of batteries provides electricity to a motor, which drives the wheels. Hybrid Electric Vehicle: Not all hybrids are alike. There are many ways to combine the engine, motor/generator, and battery. Three basic hybrid configurations are the series, parallel, and split (or through-the-road) designs. Series. The engine never directly powers the car. Instead, the engine drives the generator, and the generator can either charge the batteries or power an electric motor that drives the wheels. Parallel. The engine connects to the transmission, as do the batteries and the electric motor. So both the engine and the generator/motor can supply power to the wheels, switching back and forth as driving conditions vary. Split. The engine drives one axle and the electric motor drives the other. There is no connection between the engine and the electric components except through the road.
Thomas J. Gross Deputy Assistant Secretary for Transportation Technologies Energy Efficiency and Renewable Energy U.S. Department of Energy
Introducing the Toyota Prius

A New Type of Car

Toyotas Prius combines features of both a series and parallel hybrid electric vehicle, and it is the worlds first mass-produced HEV. The Prius is a breakthrough in many ways, combining an efficient gasolinefueled internal combustion engine with a clean, quiet electric motor powered by a battery. Like other HEVs, the Prius has many innovative features:

That Drives Like Any Other Car
The Prius means more than just impressive fuel economy and lower emissions. It is a real car that does not have to be plugged in or fed expensive or hard-to-find fuels. It drives and accelerates like other gasoline-powered vehicles, and it feels like a comfortable fivepassenger sedan.
HEVs Out of the Lab and onto the Road
What started out as a short-term solution to extend the range of electric cars may turn out to be one of the best options for increasing fuel economy and cutting greenhouse gas emissions on American roads. When automakers installed an onboard generator powered by an internal combustion engine in an electric car to make the car capable of longer trips, many viewed it as a temporary measure until better batteries were developed. But HEVs caught on in the auto industry and, after 20 years of study, a new generation of hybrids is taking center stage in the quest for cleaner, more efficient cars and trucks.
8Regenerative braking: The motor
recovers energy from the brakes when they slow down or stop the vehicle and uses it to recharge the battery.

Only Better.

Toyotas claims for the Prius are supported by independent laboratory testing by both DOE and the U.S. Environmental Protection Agency (EPA). Hybrids may be the cars that convince the American public that advanced technology can be both affordable and convenient. The next few pages offer more details on the technology used in these vehicles and illustrate how HEVs can deliver a cleaner, comfortable drive today.
8Lighter, smaller engine: To
improve efficiency, the Prius engine is sized to accommodate its average power load, not its peak load. Most gasoline engines are sized for peak power requirements, yet most drivers need peak power only 1% of the time.
8Better fuel efficiency: The Prius
consumes less fuel than vehicles powered by gasoline alone partly because the engine is turned off when its not needed. Conventional gasoline engines run constantly, regardless of power requirements.

Engine

Power to W

Power to G enerator

8Lower emissions: The Prius
reduces regulated tailpipe emissions by up to 90% and greenhouse gas emissions by about 50% compared with Tier 2 standards.
Generator Motor Batteries
Mechanica l Power Electrical Power

In Parallel

8More aerodynamic: The
streamlined Prius exterior (0.29 coefficient of drag) reduces drag by about 14% compared with the typical family sedan.
The Toyot a (THS) (left Hybrid System ) of both th combines feature s e series a nd paralle systems (d l The key to escribed opposite). t electronic he THS is an ally contro splitter t lled power ha from the t directs power en wheels an gine to both the d the gen erator. Compare th conventio e THS to a nal gasolin e engine powertrain few more (below); it has a componen ts, uses them more effic but it iently.

Rear Whee Transmiss io n Drive Shaft l

Focus on Technology

Prius Engine Helps Recharge the Battery
Why doesnt the Prius ever need to be plugged in for recharging? Because the car recharges its batteries primarily by using its own gasoline engine, in addition to regenerative braking. Some of the power from the engine is split off and stored in the cars battery pack. This self-charging system greatly enhances driving range to more than 600 miles on a tank of gas in the city.
THS Transmission Provides Seamless Shifting
The THS transmission is not a conventional automatic transmission. There is only one gear set, with no clutch, starter, alternator, or torque converter. The system fluidly adjusts the operation of the gasoline engine, generator, and electric motor to match driving conditions. The key to this system is a planetary gear power-split device that allocates power from the gasoline engine to both the final drive and the generator. The generator produces the electrical power that is used to recharge the high-voltage battery pack and to power the electric motor. The generator also functions as a starter for the gasoline engine no other starter is needed.
The result is a quiet and seamless system in fact, the only way to know what mode the car is operating in is by checking the liquid crystal display (LCD) on the dashboard.
Innovative Battery Holds a Bigger Charge
The battery pack in the Prius is a nickel-metal hydride (NiMH) pack that operates at 274 volts. The Prius features a prismatic battery, in which the positive and negative plates are stacked rather than rolled (as in a typical cylindrical battery). The resulting surface area is larger, so the battery delivers more power and is more durable.
Prius Constantly Talks to Itself
The Prius has an electronic control system that talks to the cars key components and ensures that the car always operates in its most efficient mode for lower fuel consumption and power output that instantly adjusts to driving conditions. The engine even shuts off when it isnt needed for acceleration or to recharge the battery.
When engine demand is low, such as when starting, traveling at a light load, or stopping, the Prius is driven only by its electric motor, using battery power.
During normal travel, the gasoline engine engages as needed to (1) drive the wheels and/or (2) recharge the battery.
Battery Pack Inverter Electric Motor Engine

Generator

Inverter Extends Battery Life
An inverter changes the batterys DC power into AC power for use by the electric motor, and it also changes the generators AC power into DC power to recharge the battery pack. It regulates the power from regenerative braking and extends battery life by always maintaining the proper charge.

Technical Specifications

Powertrain: Toyota Hybrid System (THS), including: 8Gasoline engine: 1.5-L, 16-valve, 4-cylinder, cast-aluminum block and head, EFI Atkinsoncycle VVTi (Variable Valve Timing with intelligence), 13:0:1 compression ratio, 70 hp at 4,500 rpm, 82 lb-ft of torque at 4,200 rpm 8Electric motor: Three-phase AC permanent magnet with peak power of 33 kW/44 hp at 1,0405,600 rpm, peak torque of 350.0 N-m/258 lb/ft (0400 rpm) 8Battery: Sealed nickel-metal hydride battery, 274 volts Transmission: Electronically controlled, continuously variable, power-split transaxle 100 mph 060 miles per hour in 12.7 seconds 52 mpg city/45 mpg highway* Fuel tank: Max. range: Passengers: Length: Width: Height: Wheelbase: Weight: Cargo: Braking: 11.9 gallons 619 mi (city)/ 535 mi (highway)** 5 169.6 in. 66.7 in. 57.6 in. 100.4 in. 2,765 lb 10 ft3 Front disc/rear drum (hydraulic with power assist) with integrated regenerative system, ABS Rack and pinion, with power assist Front: MacPherson strut Rear: torsion beam
Braking System Helps Improve Fuel Economy
When a driver slows down or steps on the brake in the Prius, the regenerative braking system converts kinetic energy from the motion of the wheels normally dissipated as heat in the brakes into electric current to help recharge the battery. About 20% of the total energy consumed by the Prius comes from regenerative braking, which contributes to the cars excellent fuel economy.
Max. speed: Acceleration: Fuel efficiency:

Steering: Suspension:

Turning circle: 31.6 ft
Coefficient of drag: 0.29 (drag for 5-passenger car is typically 0.355) Emissions: Meets California Super Ultra Low Emissions Vehicle (SULEV) standards
* EPA label values ** Based on 11.9-gal fuel tank and 52 mpg city/ 45 mpg highway.
At full acceleration, the battery adds its power to the mix, which provides a very smooth and powerful response.
When decelerating or braking, the regenerative braking system acts as a generator to help recharge the battery.
The engine shuts off when the car is idling or if engine demand is low. The gasoline engine runs only as needed to recharge the battery or run the air conditioner, which is why the Prius never has to be plugged in for recharging.
Independently Tested by the DOE and EPA
DOE Focuses on Prius Performance
Starting in March 1999, DOE conducted independent testing of the Prius at Argonne National Laboratory and the National Renewable Energy Laboratory (NREL). The testing goals included determining the operating performance of the hybrid technology and collecting data to determine the overall energy management performance of the entire vehicle and its individual components, including the batteries. Argonne researchers focused primarily on the powertrain control and energy management systems, measuring numerous system functions: engine speed and mass airflow; exhaust gas and coolant temperature; generator and motor speeds; accumulated ampere-hours; battery voltage; battery, motor, and generator current; vehicle speed; carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbon (HC) emissions; and fuel efficiency. NREL researchers focused on battery thermal management performance. Work at DOE laboratories included developing an engine map the set of data that relates an engines fuel consumption, power output, and emissions; examining the vehicles hybrid control strategy; collecting data on powertrain operation; outfitting a car for mobile testing during on-road city and highway driving; and extensive battery testing.

EPA Takes a Closeup Look at THS
In 1998, the U.S. Environmental Protection Agency evaluated the Prius THS technology over two test sequences involving the Federal Urban Dynamometer Driving Schedule and the Highway Fuel Economy Test (HFET). The results of these tests are provided in the EPA report Evaluation of a Toyota Prius Hybrid System, EPA420-R-98-006, August 1998, on the EPA website: www.epa.gov
Why Drive a Hybrid Electric Vehicle?
As the information in this brochure illustrates, the Prius and other HEVs are mechanically innovative, sophisticated vehicles. Many people might ask why they should drive these technological marvels when their current car does everything they want it to do. The two best reasons are (1) to improve mileage and (2) to reduce emissions.

Air Emissions

Growing scientific evidence suggests that greenhouse gas emissions could contribute to a change in the earth's climate and transportation, specifically the combustion of fossil fuels in our vehicles, accounts for a large portion of greenhouse gases. Moreover, EPA considers a number of other pollutants in vehicle emissions to be harmful to public health and the environment. Despite the substantial reductions in individual vehicle emissions over the last few decades, the millions of vehicles on our roads which burn thousands of gallons of petroleum every second account for a third of the country's air emissions.

The Outlook on Oil

Most people dislike having to pay $20 or $30 or more for a tank of gas. Yet, the United States depends on petroleum for nearly 95% of its transportation energy about 8 million barrels per day of petroleum products are used to fuel light trucks and cars. More than half of our petroleum is imported, and this percentage is growing, which is why oil imports represent one of the largest components of the U.S. trade deficit. And the demand for oil used for transportation will grow as the number of people and the number of miles they drive increase.

Fuel Economy

Prius (Actual 2000 EPA Test Results) SULEV (California's Most Stringent LightDuty Vehicle Standard Starting 2004) TIER 2 (Federal Light-Duty Fleet Average Standard Starting 2004)

Emissions Comparison

New Car Requirements

Prius Corolla Camry

25.3 31.6

0.009 0.02 0.07

Fuel Economy (miles per gallon)
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 Oxides of Nitrogen (NOx) (grams/mile)

Acceleration (060 mph)

Handling (Slalom)
11 Time (seconds) 12 11.4 12.2

11.5 12.1 11.5

11.4 11.6 11.8 Time (seconds)
Picture-Perfect Performance
DOE took its testing efforts on the road in September 2000. At the Route 66 Motor Speedway near Chicago, Argonne engineers tested the model year 2001 Prius against a similarly equipped 2001 Toyota Camry and 2001 Corolla to see how they compared in terms of fuel economy, acceleration, handling, and braking. The results are shown in the charts above and in the table at right.

The Prius truly appeals to people who want a car with excellent performance that is also friendly to the environment. The "Emissions Comparison" chart above illustrates how Prius almost eliminates harmful emissions it already meets California Super Ultra Low Emission Vehicle (SULEV) standards that take effect in 2004 without sacrificing performance (see table below). Prius reduces hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxides (NOx) emissions by up to 90% and carbon dioxide (CO2) and other GHG emissions by up to 50% relative to those of a comparable gasoline-fueled vehicle. But the vehicle can still handle as well as or better than comparable 5-passenger cars (see slalom and skid pad test results below), accelerate from 0 to 60 mph in under 13 seconds, and achieve fuel economy as high as 52 miles per gallon.
Prius On-Road Fuel Economy (mpg) EPA Fuel Economy (city/highway) (mpg) Acceleration (sec) 060 mph Slalom (sec) Skid Pad (G) Braking (ft from 600 mph) Passenger/Luggage Volume (ft3) 46.0 52/45 12.69 11.45 0.654 135.1 89/12 Corolla LE 31.6 29/33 11.41 12.10 0.667 173.6 * 88/12 Camry LE 25.3 23/32 12.15 11.46 0.651 198.2 97/14 7
*Not equipped with anti-lock brakes.
The U.S. Department of Energys mission is to enhance our nations energy security, national security, and environmental quality, and to contribute to a better quality of life for all Americans. The widespread availability and use of alternative fuels and clean, energy-efficient, advanced technology vehicles (like those profiled in the Technology Snapshots) will help reduce U.S. dependence on foreign petroleum and promote clean air and healthier living in communities nationwide.
Prius Cleans Up with 5 Environmental Awards
8United Nations Environmental

Protection Award

Related Web Sites
http://www.ott.doe.gov/ The U.S. Department of Energys Office of Transportation Technologies (OTT) develops and promotes advanced transportation and alternative fuel vehicles and technologies. http://www.ccities.doe.gov/ OTTs Clean Cities Program supports the deployment of alternative fuel vehicles and supporting infrastructure. http://www.ott.doe.gov/hev/ OTTs Hybrid Electric Vehicle Program. http://www.eren.doe.gov/EE/transportation_related.html Related sites from government, educational, commercial, and organizational sources. http://www.toyota.com Toyota Motor Corporation web site. http://www.fueleconomy.gov The web-based version of the DOE/EPA Fuel Economy Guide.
8EPAs First Annual Global Climate
8Sierra Clubs Excellence in
Environmental Engineering Award
8Clean Car Salute from the Clean Car
Coalition, a group composed of state, regional, and national environmental organizations in the U.S.

8Exhibited at the Museum of Modern
Art, Different Roads: Automobiles for the Next Century
This document highlights work sponsored by agencies of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.
Publishing services provided by Argonne National Laboratory

INEEL/EXT-01-01522 December 2001
Field Operations Program Toyota Prius Hybrid Electric Vehicle Performance Characterization Report
J. Francfort N. Nguyen J. Phung J. Smith M. Wehrey

INEEL/EXT-01-01522

J. Francfort1 N. Nguyen2 J. Phung2 J. Smith2 M. Wehrey2

Published December 2001

Idaho National Engineering and Environmental Laboratory Transportation Technology and Infrastructure Department Idaho Falls, Idaho 83415
Prepared for the U.S. Department of Energy Assistant Secretary for Energy Efficiency and Renewable Energy Under DOE Idaho Operations Office Contract No. DE-AC07-99ID13727
INEEL/Bechtel BWXT Idaho, LLC. Southern California Edison

Disclaimer

This document highlights work sponsored by agencies of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.

EXECUTIVE SUMMARY

The U.S. Department of Energys Field Operations Program evaluates advanced technology vehicles in real-world applications and environments. Advanced technology vehicles include pure electric, hybrid electric, hydrogen, and other vehicles that use emerging technologies such as fuel cells. Information generated by the Program is targeted to fleet managers and others considering the deployment of advanced technology vehicles. As part of the above activities, the Field Operations Program has initiated the testing of the Toyota Prius hybrid electric vehicle (HEV), a technology increasingly being considered for use in fleet applications. This report describes the Pomona Loop testing of the Prius, providing not only initial operational and performance information, but also a better understanding of HEV testing issues. The Pomona Loop testing includes both Urban and Freeway drive cycles, each conducted at four operating scenarios that mix minimum and maximum payloads with different auxiliary (e.g., lights, air conditioning) load levels. The five passenger Prius is powered by a 70-hp, 1.5-liter, 4-cylinder gasoline engine and a 44-hp electric motor. The Prius also has a 274-volt nickel metal-hydride battery comprising 228 1.2-volt cells. The Prius exhibited test results of 35.7 to 55.6 miles per gallon (mpg) during the four types of Urban Loop testing; the EPA estimate for city driving is 52 mpg. During the four types of Freeway Loop testing, the Prius got 40.0 to 45.4 mpg; the EPA estimate for highway driving is 45 mpg. Even though the EPA tests are conducted on a dynamometer and the Pomona Loop tests are conducted as on-road driving tests, when tested with a minimum payload and no auxiliary loads, the mpg test results are the same for the Freeway Loop testing and the EPA highway testing. Under the same operating scenario, the Urban Loop results are 3.6 mpg higher than the EPA estimate for city driving. The Pomona Loop testing of the Prius demonstrated the difficulty of accurately measuring fuel economy without physically modifying a vehicle. Unlike electric vehicles, where a kilowatthour meter can accurately measure energy flows, the energy use of a Prius type of HEV (non-grid connected) is determined by measuring how much gasoline was used; so a void must now be accurately measured. One option is to apply a known amount of fuel to the vehicle and run it until it stops. However, rarely will a perfectly uniform amount of fuel remain and even more rarely will the vehicle run out of fuel where it started, so this method is not practical for on-road testing. Another issue is that variables such as driver behavior (the lead foot), the use of air conditioning and other auxiliary loads, or the type of driving cycle used can result in significant energy efficiency variations. For instance, the eight individual Urban Loop test results ranged from 35.2 to 57.6 mpg, a 64% difference. The Prius testing not only provided an initial performance benchmark, but also highlighted HEV-specific testing issues. The lessons learned from this testing will be used to prepare for expanded HEV testing, ensuring accurate fuel-use measurements are used and that the testing applications are meaningful and applicable to fleet managers.

CONTENTS

EXECUTIVE SUMMARY... iii ACRONYMS..... vi 1. INTRODUCTION..... 1 1.1 2. 3. Southern California Edisons Testing Interests... 2
MANUFACTURERS SPECIFICATIONS... 3 RANGE AND FUEL ECONOMY TEST RESULTS... 4 3.1 3.2 3.3 Urban Loop Test Results.... 5 Freeway Loop Test Results.... 6 Fuel Usage Measurement.... 7
VEHICLE PERFORMANCE TESTS... 8 4.1 4.2 4.3 4.4 Vehicle Acceleration Testing... 8 Vehicle Braking Testing... 9 Sound Measurements... 10 Weight Certification... 11

CONCLUSIONS..... 11

FIGURES
1. Average mph for each operating scenario used for the Urban and Freeway Pomona Loops. 7 2. Fuel usage measurement equipment... 8 3. Tank filling operation.... 8 4. Zero to 60 mph acceleration test results... 9 5. Urban Loop sound measurement results... 10 6. Freeway Loop sound measurement results... 10

TABLES

1. Toyota Prius manufacturer specifications. Source - http://prius.toyota.com/details/specs.html. 3 2. Pomona Loop operating scenarios for test vehicles... 4 3. Toyota Prius miles driven and fuel use results from the Urban Loop testing.. 5 4. Toyota Prius miles driven and fuel use results from the Freeway Loop testing.. 6 5. Prius acceleration test results in seconds... 9 6. Quarter-mile acceleration test results... 9 7. Prius braking test results from 25 mph... 10 8. Measured Vehicle Weight.... 11

ACRONYMS

ATV DOE EV EVTC HEV INEEL kWh MPG NiMH QVTs SCE SOC Advanced Technology Vehicle U.S. Department of Energy Electric Vehicle Electric Vehicle Technical Center Hybrid Electric Vehicle Idaho National Engineering and Environmental Laboratory kilowatt-hour Miles per Gallon Nickel metal hydride (battery) Qualified Vehicle Testers Southern California Edison Company state-of-charge

1. INTRODUCTION

The U.S. Department of Energys Field Operations Program provides fleet managers and other potential advanced technology vehicle (ATV) users with accurate and unbiased information on vehicle performance. This allows the purchaser to make informed decisions about acquiring and operating ATVs. Vehicle information is obtained by testing ATVs in conjunction with industry partners and disseminating the testing results. The ATVs are tested using three methods Baseline Performance Testing, Accelerated Reliability Testing, and Fleet Testing. The testing results are disseminated via the Programs Website in the form of vehicle fact sheets, summary reports, and survey results (http://ev.inel.gov/fop). Additional information on the Website includes testing specifications and procedures as well as general information about ATVs, such as how they work and their histories. The Field Operations Program signed a 5-year testing agreement in 2000 with the following group of Qualified Vehicle Testers (QVTs):

Electric Transportation Applications (lead partner) American Red Cross Arizona Public Service Bank One of Arizona Potomac Electric Power Company Salt River Project Southern California Edison Southwest Airlines Virginia Power.
As part of the Field Operations Program testing activities and as a compliment to the more controlled EVAmerica Baseline Performance testing, Southern California Edison (SCE) performed Pomona Loop testing on a Toyota Prius hybrid electric vehicle (HEV). The Pomona Loop testing of the Prius was conducted not only to gather its operational and performance information, but also to better understand HEV testing issues. For instance, what testing variables are unique to HEVs and can these variables significantly affect the accuracy of the test results? Another question is how should HEVs be tested so the results are meaningful to fleet managers and other potential HEV users? Informal conversations with other HEV testers indicate that some test methods do not always accurately reflect the performance of HEVs when they are used in fleet applications. Program personnel and the testing partners recognized that new test procedures and controls could be required for HEV testing. In an effort to determine whether past electric vehicle (EV) testing experience was applicable to HEV testing and not be presumptuous that they fully
understood all of the HEV testing issues, it was decided to apply a lessons-learned approach to the first HEV tests. For example, when EVs are range tested, the distance traveled per charge was rarely greater than 100 miles and the energy used was usually 20 to 30 kilowatt-hours (kWh). Electric energy use is easy to measure with kWh meters, and the mathematics of distance traveled versus energy units used make range calculations very accurate. However, when testing gasoline use in HEVs, more miles must be accumulated to accurately measure either energy use per distance traveled or distance traveled per energy unit. Pomona Loop testing is a relatively fast and inexpensive method to identify these and other issues such as the significant variations in fuel consumption that can occur in HEVs when driver behavior is variable. This can include not only the aggressiveness in how the test driver drives the HEV, but also what on-board vehicle accessories are turned on during the drive. For instance, air conditioning can have a significant energy use impact, especially with the smaller gasoline engines used in HEVs. To more fully understand the above and other issues, as well as to prepare for more complex (and expensive) testing, the Field Operations Program partnered with SCE to Pomona Loop test the Prius. SCE also has their own organizational interests that compelled them to want to test the Prius. These are briefly discussed below. The Prius testing results discussed in this report are based on the SCE Prius testing report (TC-01-138-TR02). This report summarizes the results.

Southern California Edisons Testing Interests
Over the years, new technologies have evolved that promise to have a significant impact in the transportation industry. One such technology is the hybrid power train. It is important that these early market entrants be evaluated and understood in terms of performance, energy efficiency, and emissions. Once different models have been tested, an evaluation of the benefits of the different hybrid configurations, including plug-in hybrids, will be possible. To this end, SCE partnered with the Field Operations Program to conduct a performance characterization of a Toyota Prius. The purpose of SCEs evaluation of EVs, HEVs, EV chargers, batteries, and related items is to support their safe and efficient use and to minimize potential utility system impacts. The following facts support this purpose: As a fleet operator and an electric utility, SCE uses EVs to conduct business. SCE must evaluate EVs, HEVs, batteries, and charging equipment in order to make informed purchase decisions. SCE must determine if there are any safety issues with EV equipment and their usage. SCE has a responsibility to educate and advise its customers about the efficient and safe operation of EVs and HEVs.
Tests performed were: weight certification, range, fuel efficiency, performance (acceleration, maximum speed, and braking), and sound measurements. They were conducted at 2
SCEs Electric Vehicle Technical Center (EVTC) and on the Urban and the Freeway Pomona Loops. Testing was conducted in accordance with the SCE HEV test procedure.
MANUFACTURERS SPECIFICATIONS
Table 1. Toyota Prius (2001 model) manufacturer specifications.a Gasoline Engine Type: Aluminum double overhead cam (DOHC) Displacement (cc) 1497 Horsepower @ rpm 70 @ 4500 Torque @ rpm 82 @ 4200 Compression Ratio 13.0:1 Valvetrain: 16-Valve with Variable Valve Timing with intelligence (VVT-i) Fuel System: Multi-Point EFI w/ Electronic Throttle Control System w/ Intelligence (ETCS-i) Ignition System: Electronic w/ Toyota Direct Ignition system (TDI) Emission Rating: Super Ultra Low Emission Vehicle (SULEV) Electric Motor/ Generator Motor Type Power Output Electric Power Storage Battery Type Output Drivetrain Type: Transmission: Body/Suspension/Chassis Body Type: Front Suspension: Rear Suspension: Electric Power Steering (EPS) Turning Diameter, Curb-to-Curb (ft.) Brakes: Wheels: Tires: Interior Dimensions Head room (in., front/rear) Leg room (in., front/rear) Shoulder Room (in., front/rear) Hip room (in., front/rear) Cargo Volume (cu. ft.) Passenger Volume (cu. ft.) Exterior Dimensions Wheelbase (in.) Length (in.) Height (in.) Permanent Magnet 33 kW/44 hp @ 1040 - 5600 rpm Sealed Nickel-Metal Hydride (NiMH) 273.6 V (228 1.2-V Cells) Front-Wheel Drive Electronically Controlled CVT Aluminum monocoque MacPherson Strut w/ stabilizer bar Torsion Beam w/ stabilizer bar Rack-and-Pinion w/ electric power-assist 31.6 Power-Assisted Ventilated Front Disc/Rear Drum 4-Wheel Anti-Lock Braking System (ABS) 14-in. Alloy P175/65 R14 Low Rolling-Resistance 38.8/37.1 41.2/35.4 52.8/52.2 50.7/51.9 11.8 88.6 100.4 169.6 57.6 3

Width (in.) Track (in., front/rear) Curb Weight (lbs.)

66.7 58.1/58.2 2765

EPA Mileage Estimates/Fuel Capacity City/Highway/Combined 52/45/48 Fuel (gal.) 11.9 Fuel Required Regular Unleaded Final EPA mileage estimate. Actual mileage may vary. a. Source http://prius.toyota.com/details/specs.html
RANGE AND FUEL ECONOMY TEST RESULTS
The Pomona Loop Testing consists of two types of on-road drive cycles: 1. The Urban Loop is 19.3 miles long with approximately 50 stop signs and traffic lights, and the elevation ranges from about 900 to 1,500 feet above sea-level (Appendix A). The Urban Loop is located in the greater Pomona, California area and it consists of city and residential area streets. The Freeway Loop is 37.2 miles long with elevation ranges from about 700 to 1,150 feet above sea-level (Appendix A). The Freeway Loop is also located in the greater Pomona, California area and it consists of Southern California freeways.
Four vehicle-operating scenarios are used for each of the Pomona Loops, including operating the test vehicles with minimum or maximum payloads and either no auxiliary or auxiliary loads (Table 2). The Prius was tested twice at each of the four operating scenarios for both the Urban and Freeway Loops, so that a total of 16 drive cycles were performed. The testing was designed to not necessarily complete a set number of Loops per drive cycle, rather, it was designed to accumulate approximately 100 miles during each of the 16 drive cycles. A total of 1645 miles were driven during the fuel economy testing. Table 2. Pomona Loop operating scenarios for test vehicles. Pomona Urban Loop Vehicle Operating Scenarios UR-1 UR-2 UR-3 UR-4 FW-1 FW-2 FW-3 FW-4 Urban Range Test, Min Payload, No Auxiliary Loads Urban Range Test, Min Payload, A/C on High, Headlights on Low, Radio On Urban Range Test, Max Payload, No Auxiliary Loads Urban Range Test, Max Payload, A/C on High, Headlights on Low, Radio On Freeway Range Test, Min Payload, No Auxiliary Loads Freeway Range Test, Min Payload, A/C on High, Headlights on Low, Radio On Freeway Range Test, Max Payload, No Auxiliary Loads Freeway Range Test, Max Payload, A/C on High, Headlights on Low, Radio On
Pomona Freeway Loop Vehicle Operating Scenarios
For a full discussion of the Urban and Freeway Pomona Loop testing, the Southern California Edison Pomona Loop Test Procedures Report can be accessed at the following address http://ev.inel.gov/fop

Urban Loop Test Results

The Prius was tested twice for each of four operating scenarios on the Urban Pomona Loop (Table 3). For urban driving with a minimum payload and no auxiliaries used (UR-1), the average fuel economy was 55.6 mpg. With a minimum payload and the auxiliary loads turned on (UR-2), the fuel economy dropped to an average of 49.5 mpg. With the maximum payload and no auxiliaries on (UR-3), the fuel economy was 47.5 mpg. With the maximum payload and the auxiliary loads turned on (UR-4), the fuel economy dropped to 35.7 mpg. It should be noted that while the driver was not supposed to play the radio during the no-auxiliary load tests, the radio was played during all of the mileage tests, including the no-auxiliary load tests (Loops UR-1 and UR-3). Table 3. Toyota Prius Urban Loop testing results.

Drive Cycle UR-1 UR-1 UR-2 UR-2 UR-3 UR-3 UR-4 UR-4
Test Date 07/31/01 08/22/01 08/01/01 08/20/01 08/07/01 08/15/01 08/09/01 08/14/01
Average Ambient Temp (F) 79.0 75.0 79.0 85.0 90.0 100.0 84.0 92.0
Total fuel usage (gal) 1.76 1.89 1.99 2.15 2.15 2.17 2.91 2.86
Miles driven 101.3 101.5 102.5 102.3 103.1 102.1 102.2 103.9
Calculated MPG 57.6 53.7 51.4 47.6 47.9 47.1 35.2 36.3
Average MPG 55.6 49.5 47.5 35.7
Manufacturer MPG1 54.4 54.0 52.4 43.5 49.1 47.8 35.3 36.9
Fuel Economy Meter MPG is the average of 21 readings recorded during each drive cycle.
The estimated range calculation is based on the nominal 11.9 gallon fuel tank and the above testing results. The average estimated ranges are listed by operating scenarios: UR-1, minimum payload and no auxiliaries 662 miles UR-2, minimum payload and auxiliaries on 589 miles UR-3, maximum payload and no auxiliaries 565 miles UR-4, maximum payload and auxiliaries 425 miles
The total mileage driven during the eight urban drive cycles (four types of urban tests, each driven twice) was 818.9 miles and the total fuel used was 17.88 gallons. Therefore, the overall fuel economy during the eight urban drive cycles was 45.8 mpg, and based on the 11.9-gallon fuel tank, the estimated maximum range under mixed urban driving conditions would be 545 miles.
Freeway Loop Test Results
The Prius was also tested twice for each of the four operating scenarios on the Freeway Pomona Loop (Table 4). For freeway driving with a minimum payload and no auxiliaries used (FW-1), the average fuel economy was 45.4 mpg. With a minimum payload and the auxiliaries turned on (FW-2), the fuel economy dropped to an average of 42.6 mpg. With maximum payload and no auxiliaries on (FW-3), the fuel economy was 44.5 mpg. Again, with maximum payload and the auxiliary load on (FW-4), the fuel economy dropped to 40.0 mpg. It should be noted that while the driver was not supposed to play the radio during the no-auxiliary load tests, the radio was played during all of the mileage tests, including the no-auxiliary load tests (Loops FW-1 and FW-3). Table 4. Toyota Prius miles driven and fuel economy results from the Freeway Loop testing.

Drive Cycle

FW-1 FW-1 FW-2 FW-2 FW-3 FW-3 FW-4 FW-4

Test Date

08/02/01 08/16/01 08/03/01 08/21/01 08/06/01 08/10/01 08/08/01 08/13/01

Average Ambient Temp (F)

79.5 87.0 79.0 78.0 89.0 83.0 89.0 87.0

Total fuel usage (gal)

2.28 2.22 2.52 2.37 2.33 2.37 2.54 2.58

Miles driven

103.2 100.9 106.5 102.0 104.2 104.8 103.5 101.0

Calculated MPG

45.2 45.5 42.3 42.9 44.8 44.2 40.8 39.1

Average MPG

Manufacturer MPG1
47.4 51.8 43.1 41.5 44.4 46.1 42.7 41.6
Fuel Economy Meter MPG is average of 21 readings.
The estimated range calculation was based on the 11.9-gallon fuel tank and the above testing results. The average estimated freeway ranges are listed by operating scenarios: FW-1, minimum payload and no auxiliaries 540 miles FW-2, minimum payload and auxiliaries on 507 miles FW-3, maximum payload and no auxiliaries 530 miles FW-4, maximum payload and auxiliaries 476 miles.
The total mileage driven during the eight freeway drive cycles (four types of freeway tests, each driven twice) was 826.1 miles and the total fuel used was 19.21 gallons. Therefore, the overall fuel economy during the eight freeway drive cycles was 43.0 mpg, and based on the 11.9 gallon fuel tank, the estimated maximum range under mixed freeway driving was 512 miles. The overall fuel economy for all 16 tests averaged 44.4 mpg (UR&FW Average in Figure 1). Figure 1 also shows the average mpg results for the two tests performed for each operating scenario as well as the average mpg results for all eight urban tests (UR-Average) and all eight freeway tests (FW-Average). (See Table 2 for an explanation of the operating scenarios).
Average Prius MPG Results for Urban & Freeway Loops
-4 -A ve ra U R ge &F W Av er ag e FW U R -1 U R -2 U R -3 U R -4 -1 -2 R -A ve ra ge FW -3 FW FW FW

Miles per Gallon

Figure 1. Average miles per gallon (mpg) for each operating scenario used for the Urban and Freeway Pomona Loops.
As mentioned in the introduction, this initial round of Pomona Loop HEV Testing was not envisioned to be the most rigorous of quantitative tests of fuel economy. The Prius was leased, which limited the fuel economy measurement options to nonintrusive methods both because of the lease agreement and the desire to minimize testing (and vehicle repair) costs. Given these constraints, three low-cost, nonintrusive (or quasinonintrusive) fuel economy measurement methods were considered, the first two of which were discarded. One method would have relied on gas pump readings to determine the quantity of fuel used for a given test. When the vehicle tank was refilled, the first click of the pump nozzle would be accepted as indication of a full tank and the fuel quantity displayed by the pump would be read. However, the variability of this method is well known to anyone that has successfully added gasoline after the first click. To improve the accuracy of the tests, a second method was considered and attempted. It relied on draining the vehicle tank with the fuel system pump (by temporarily disconnecting the fuel supply line and activating the pump with the ignition key on) and subsequently filling it with a known quantity of fuel. Using up all of the known quantity of fuel would have yielded fuel usage. Unfortunately, it was not possible to get a consistent empty tank condition; successive reactivation of the fuel pump always drained an additional amount of fuel. The third method relied on carefully refilling the vehicle tank in the EVTC lab, early in the morning (to minimize ambient temperature swings and gasoline expansion during driving), before each drive cycle with a lab-quality calibrated graduated cylinder (Figures 2 and 3). A notch in the tank filler tube was giving the necessary liquid level reference. This method was used and it met the criteria of being nonintrusive and low cost, while elucidating HEV testing variables and issues. 7

Fuel Usage Measurement

Figure 2. Fuel usage measurement equipment.
Figure 3. Tank filling operation.
VEHICLE PERFORMANCE TESTS
Performance testing was conducted at the Los Angeles County Fairplex drag strip in Pomona, California on August 27, 2001. The tests were started at 11:00 AM and completed by 12:30 PM. The ambient temperature was 9293F and wind speeds were 35 mph from the Northwest; the track runs north/south. Tire pressures were 34 psi (front wheels) and 36 psi (rear wheels), as specified by the manufacturer.
Vehicle Acceleration Testing
Table 5 shows the results from the acceleration tests. The results for 0 to 30 mph and 0 to 60 mph were obtained with a performance computer. The average acceleration time for 0 to 30 mph was 4.5 seconds and for 0 to 60 mph it was 13.1 seconds. The 30 to 55 mph accelerations were hand timed; the average time was 7.0 seconds. Speed and distance versus time for one of the 0 to 60 mph acceleration tests is shown Figure 4. Table 6 shows the results of quarter-mile acceleration results. The average time was 19.4 seconds, with an average speed of 74.1 mph. In separate tests, the maximum recorded speeds were 87.9 mph (southbound) and 82.8 mph (northbound).
Table 5. Prius acceleration test results in seconds. Sequence Direction mph (s) S N S N Average (s) 4.3 4.7 4.4 4.5 4.5
mph (s) 12.2 14.4 12.6 13.3 13.1
mph (s) 6.5 7.2 6.7 7.6 7.0
Speed (mph) Speed 15 Time (s) 30 Distance

2000 Distance (ft)

Figure 4. Zero to 60 mph acceleration test results. Table 6. Quarter-mile acceleration test results Sequence Direction Time (seconds) S N S N Average 18.9 20.0 19.2 19.6 19.4 Speed (mph) 77.1 70.5 75.9 72.8 74.1

Vehicle Braking Testing

Table 7 shows the results of the 25-mph braking tests. The results were obtained with a performance computer. The average stopping distance adjusted for 25 mph was 27.16 feet.
Table 7. Prius braking test results from 25 mph. Sequence Direction S N S N Speed (mph) 28.41 25.91 29.16 26.93 Time (seconds) 2.09 2.08 1.90 1.81 Distance (feet) 35.55 35.44 34.90 31.mph Adjusted Distance (ft) 25.722 32.714 24.139 26.066

Average (ft) 27.160

Sound Measurements
These measurements were made with a Sound Level Meter placed at head level in the front passenger seat area. The sound tests were conducted for approximately 47 minutes during the Urban Loop (Figure 5) and 33 minutes during the Freeway Loop (Figure 6). The sound averaged 60 decibels during the Urban loop and between 65 and 70 decibels during the Freeway Loop.

70 Sound Intensity (dBA) 25 Time (m) 50 This data looks like heavy traffic driving.
Figure 5. Urban Loop sound measurement results.
Time (m) Transition Exit Freeway Change
Figure 6. Freeway Loop sound measurement results. The left axis is the sound intensity in dBA.

Weight Certification

When weighed at a certified scale, the Prius was found to have a total available payload of 885 pounds (Table 8). Table 8. Measured vehicle weight. Front Axle Sticker GVWR (lb) Measured Weight (lb) Available Payload (lb) 1,970 1,Rear Axle 1,685 1,Total Weight 3,655 2,770 885

CONCLUSIONS

The Pomona Urban Loop test most similar to the EPA test that estimates City mileage is the UR-1 scenario (minimum payload and no air conditioning). The UR-1 results averaged 55.6 mpg, or 3.6 mpg better than the 52 mpg EPA result. Overall, the Urban Loop mpg results ranged from 35.7 to 55.6 mpg for the five-passenger Prius. The EPA highway estimate for the Prius is 45 mpg. The FW-1 loop results, which are closest to the EPA test conditions, were slightly higher at 45.4 mph. The overall Freeway test results ranged from 40 to 45.4 mpg. With the exception of the UR-1 and FW-1 operating scenarios, the other six operating scenarios all place greater energy requirements on the Prius than the EPA testing scenarios, so the fuel economy results are not unexpected. Overall, the Prius performed well in these initial tests and the ability to carry five passengers should be attractive for fleet applications. The testing did highlight that future range and fuel economy on-road testing should include test distances that are much longer than traditionally used for the Pomona Loop testing (and other testing) due to the stingy fuel use rates and fuel use must be measured more accurately. Accelerated reliability testing, under which 100,000 miles are placed on individual vehicles, will provide representative fuel economy rates. The EVAmerica type of Baseline Performance testing will provide accurate fuel economy rates as it allows for the use of more intrusive fuel measurement methods. The EVAmerica testing will also provide very accurate vehicle performance data given the controlled testing possible when using a dynamometer and a closed track. Two Prius are currently undergoing Accelerated Reliability testing, under which 100,000 miles are accumulated per Prius in 2 years. The results of this testing will document any long-term operational issues, including the performance and life of the hybrid battery back.
Appendix A: Urban and Freeway Pomona Loop Maps

URBAN POMONA LOOP

4.7 miles

Monte Vista

Baseline / 16th

EV Technical Center 265 N. East End Ave. Pomona, CA 91767

0.6 mi

6.1 miles

1.0 mile

Elevation Profile
1600 Orange Grove Foothill Elevation (feet, msl) Vineyard 1300 Mills/Holt Euclid Monte Vista Arrow Hwy 1500 Baseline Euclid

Vineyard

4.1 miles

Mills/Holt 20

Tow ne 35 37.5 Indian Hills & 10 37.2

Distance (miles)

FREEWAY POMONA LOOP
2000 Ele vation (fe e t, m s l) Philips Ranc h

600 400

Euclid

R e s ervo ir

Mountain

Indian Hills & 10

& 10

57 & 60

15 & 60

57 & 10 32.5