Halderman J.D., Linder J. Automotive Fuel and Emissions Control Systems

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HYBRID SAFETY AND SERVICE PROCEDURES 401

TOWING If a disabled vehicle needs to be moved a short

distance (to the side of the road, for example) and the vehicle can

still roll on the ground, the easiest way is to shift the transmission

into neutral and manually push the vehicle. To transport a vehicle

NOTE: The high-voltage HV battery pack cannot be jump

started on most HEVs. One exception is the Ford Escape/

Mercury Mariner hybrids that use a special “jump-start”

button located behind the left kick panel. When this but-

ton is pushed, the auxiliary battery is used to boost the

HV battery through a DC-DC converter.

FIGURE 31–8 The underhood 12-volt jump-start terminal

on this 2004 Toyota Prius has a red plastic cover with a “”

sign. The positive booster cable clamp will attach directly to

the vertical metal bracket.

RESCUE VEHICLE

FIGURE 31–7 Jump-starting a 2001–2003 Toyota Prius using a

12-volt supply to boost the 12-volt auxiliary battery in the trunk.

COLLISION AND REPAIR

INDUSTRY ISSUES

JUMP-STARTING The 12-volt auxiliary battery may be

jump-started if the vehicle does not start. The 12-volt auxiliary

battery is located under the hood or in the cargo (trunk) area of

some HEVs. Using a jump box or jumper cable from another

vehicle, make the connections to the positive and negative bat-

tery terminals.

 SEE FIGURE 31–7 .

On the 2004 Toyota Prius vehicles, there is a stud lo-

cated under the hood that can be used to jump-start the aux-

iliary battery, which is located in the truck. The trunk has an

electric latch and cannot be opened if the auxiliary battery is

dead.

 SEE FIGURE 31–8 .

Even if all of the above steps are followed, there is

still a risk for electrical shock at the high-voltage

batteries. Always follow the vehicle manufacturer’s

instructions exactly and wear high-voltage gloves

and other specified personal protective equipment

(PPE).

WARNING

MOVING AND TOWING

A HYBRID

However, if work is going to be performed on any of the following

components, then service information procedures must be fol-

lowed to prevent possible electrical shock and personal injury:



The high-voltage (HV) battery pack



Any of the electronic controllers that use orange cables

such as the inverter and converters



The air-conditioning compressor if electrically driven and

has orange cables attached

To safely depower the vehicle always follow the instructions

found in service information for the exact vehicle being ser-

viced. The steps usually include the following:

STEP 1 Turn the ignition off and remove the key (if equipped)

from the ignition.

CAUTION: If a push-button start is used, remove

the key fob at least 15 feet (5 m) from the vehicle

to prevent the vehicle from being powered up.

STEP 2 Remove the 12-volt power source to the HV controller.

This step could involve the following:

•

Removing a fuse or a relay

•

Disconnecting the negative battery cable from the

auxiliary 12-volt battery

STEP 3 Remove the high-voltage (HV) fuse or service plug or

switch.

402 CHAPTER 31

PRECAUTIONS The HV battery box should always be

removed as an assembly, placed on a rubber-covered work bench,

and handled carefully. Every other part, especially the capacitors,

should be checked for voltage reading while wearing HV rubber

gloves. Always check for voltage as the components become

accessible before proceeding. When removing high-voltage com-

ponents, it is wise to use insulated tools.

 SEE FIGURE 31–11 .

STORING THE HIGH-VOLTAGE BATTERIES If a hybrid is

to be stored for any length of time, the state of charge of the HV

batteries must be maintained. If possible, start the vehicle every

month and run it for at least 30 minutes to help recharge the HV

batteries. This is necessary because NiMH batteries suffer from

self-discharge over time. High-voltage battery chargers are expen-

sive and may be hard to find. If the HV battery SOC was over 60%

when it was put into storage, the batteries may be stored for about

a month without a problem. If, however, the SOC is less than 60%,

a problem with a discharged HV battery may result.

HOISTING A HYBRID VEHICLE When hoisting or using

a floor jack, pay attention to the lift points. Orange cables run

under the vehicle just inside the fame rails on most hybrids.

 SEE FIGURE 31–12 .

Some Honda hybrid vehicles use an aluminum pipe painted

orange that includes three HV cables for the starter/generator

and also three more cables for the HV air-conditioning com-

pressor. If any damage occurs to any high-voltage cables, the

MIL will light up, and a no-start will result if the PCM senses

a fault. The cables are not repairable and are expensive. The

cables can be identified by an orange outer casing, but in some

cases, the orange casing is not exposed until a black plastic

underbelly shield is removed first.

HV BATTERY DISPOSAL The hybrid electric vehicle man-

ufacturers are set up to ship NiMH battery packs to a recycling

FIGURE 31–9 Using a warning cover over the steering wheel

helps others realize that work is being performed on the high-

voltage system and that no one is to attempt to start or move the

vehicle.

FIGURE 31–10 A lock box is a safe location to keep the

ignition keys of a hybrid electric vehicle while it is being serviced.

When Do I Need to DePower the High-Voltage

System?

During routine service work, there is no need for a tech-

nician to depower the high-voltage system. The only

time when this process is needed is if service repairs or

testing is being performed on any circuit that has an or-

ange cable attached. These include the following:

• AC compressor if electrically powered

• High-voltage battery pack or electronic controllers

The electric power steering system usually operates

on 12 volts or 42 volts, and neither is a shock haz-

ard. However, an arc will be maintained if a 42-volt

circuit is opened. Always refer to service information

if servicing the electric power steering system or any

other system that may contain high voltage.

FREQUENTLY ASKED QUESTION

REMOVING THE HIGH-

VOLTAGE BATTERIES

away from an emergency location, a flatbed truck should be used

if the vehicle might be repaired. If a flatbed is not available, the

vehicle should be towed by wheel-lift equipment with the front

wheels off the ground (FWD hybrid electric vehicles only). Do not

use sling-type towing equipment. In the case of 4WD HEVs such

as the Toyota Highlander, only a flatbed vehicle should be used.

MOVING THE HYBRID VEHICLE IN THE SHOP After an

HEV has been serviced, it may be necessary to push the vehicle

to another part of the shop or outside as parts are ordered. Make

sure to tape any orange cable ends that were disconnected dur-

ing the repair procedure. Permanent magnets are used in all the

drive motors and generators, and it is possible that a high-voltage

arc could occur as the wheels turn and produce voltage. Another

way to prevent this is to use wheel dollies. A sign that says “HIGH

VOLTAGE—DO NOT TOUCH” could also be added to the roof of

the vehicle. Remove the keys from the vehicle and keep in a safe

location.

 SEE FIGURES 31–9 AND 31–10 .

HYBRID SAFETY AND SERVICE PROCEDURES 403

center. There is an 800 number located under the hood or on the

HV battery pack that can be used to gain information on how to

recycle these batteries.

Always follow the proper safety procedures, and then mi-

nor service to hybrid vehicles can be done with a reasonable

level of safety.

FIGURE 31–12 The high-voltage wiring on this Honda hybrid

is colored orange for easy identification.

Will the Heat from Paint Ovens Hurt

the High-Voltage Batteries?

Nickel-metal hydride ( NiMH ) batteries may be dam-

aged if exposed to high temperatures, such as in a paint

oven. The warning labels on hybrid vehicles specify that

the battery temperature not exceed 146°F (63°C). There-

fore, be sure to check the temperature of any paint oven

before allowing a hybrid electric vehicle into one that

may be hotter than specified. Check service information

for details on the vehicle being repaired.

FREQUENTLY ASKED QUESTION

High-Voltage Battery SOC

Considerations

NiMH batteries do not store well for long lengths of

time. After a repair job or when the HV system has

been powered down by a technician and powered up

again, do not be surprised if a warning lamp lights,

diagnostic trouble codes are set, and the MIL are

illuminated. If everything was done correctly, a couple

road tests may be all that is required to reset the MIL.

The HV battery indicator on the dash may also read

zero charge level. After a road test, the HV battery

level indicator will most likely display the proper

voltage level.

TECH TIP

DIAGNOSIS PROCEDURES Hybrid electric vehicles should be

diagnosed the same as any other type of vehicle. This means follow-

ing a diagnostic routine, which usually includes the following steps:

STEP 1 Verify the customer concern.

STEP 2 Check for diagnostic trouble codes (DTCs). An en-

hanced or factory level scan tool may be needed to get

access to codes and subcodes.

ROUTINE SERVICE

PROCEDURES

FIGURE 31–11 Insulated tools, such as this socket set, would

provide an additional margin of safety to the service technician

when working around high-voltage components and systems.

STEP 3 Perform a thorough visual inspection. If a DTC is

stored, carefully inspect those areas that might be the

cause of the trouble code.

STEP 4 Check for technical service bulletins (TSBs) that may

relate to the customer concern.

STEP 5 Follow service information specified steps and pro-

cedures. This could include checking scan tool data

for sensors or values that are not within normal

range.

STEP 6 Determine and repair the root cause of the problem.

STEP 7 Verify the repair and clear any stored diagnostic trou-

ble codes unless in an emission testing area. If in an

emission test area, drive the vehicle until the power-

train control module (PCM) passes the fault and turns

off the malfunction indicator lamp (MIL), thereby allow-

ing the vehicle to pass the inspection.

STEP 8 Complete the work order and record the “three Cs”

(complaint, cause, and correction).

404 CHAPTER 31

1. Always follow the service information recommended air

filter replacement interval.

2. For best results use the factory type and quality air filter.

CAUTION: Using a “high-performance” cotton-type

air filter that uses oil on the cotton to trap dirt can

cause problems with the mass airflow sensor. If a

MAF sensor diagnostic trouble code (DTC) is set,

check to see if an aftermarket air filter that has

been over oiled could be the cause.

3. Double-check that all of the air ducts are securely fastened

after checking or replacing the air filter.

AIR-CONDITIONING SERVICE Performing air-conditioning

system service is similar to performing this service in any vehicle

equipped with an internal combustion engine. However, there are

several items to know when servicing the air-conditioning system

on a hybrid electric vehicle, including the following:

1. Many hybrid electric vehicles use an air-conditioning com-

pressor that uses high voltage from the high-voltage (HV)

battery pack to operate the compressor either all of the

time, such as many Toyota/Lexus models, or during idle

stop periods, such as on Honda hybrids.

2. If the system is electrically driven, then special refrigerant oil

is used that is nonconductive. This means that a separate

recovery machine should be used to avoid the possibility of

mixing regular refrigerant oils in with the oil used in hybrids.

3. Always read, understand, and follow all of the service in-

formation instructions when servicing the air-conditioning

system on a hybrid electric vehicle.

OIL CHANGE Performing an oil change is similar to chang-

ing oil in any vehicle equipped with an internal combustion

engine. However, there are several items to know when chang-

ing oil in a hybrid electric vehicle, including the following:



Use vehicle manufacturer’s recommended hoisting

locations. Use caution when hoisting a hybrid electric

vehicle and avoid placing the pads on or close to the

orange high-voltage cables that are usually located

under the vehicle.



Always use the specified oil viscosity. Most hybrid

electric vehicles require either of the following:

SAE 0W-20

SAE 5W-20

Using the specified oil viscosity is important because

the engine stops and starts many times, and using the

incorrect viscosity not only can cause a decrease in fuel

economy but also could cause engine damage.



Always follow the specified procedures. Be sure that

the internal combustion engine (ICE) is off and that the

“READY” lamp is off. If there is a smart key or the vehicle

has a push-button start, be sure that the key fob is at

least 15 feet (5 m) away from the vehicle to help

prevent

the engine from starting accidentally.

COOLING SYSTEM SERVICE Performing cooling sys-

tem service is similar to performing this service in any vehicle

equipped with an internal combustion engine. However, there

are several items to know when servicing the cooling system on

a hybrid electric vehicle, including the following:



Always check service information for the exact

procedure to follow. The procedure will include

the following:

1. The specified coolant. Most vehicle manufacturers

will recommend using premixed coolant because using

water (half of the coolant) that has minerals could cause

corrosion issues.

2. The specified coolant replacement interval. While

this may be similar to the coolant replacement interval

for a conventional vehicle, always check to be sure that

this service is being performed at the specified time or

mileage interval.

3. The specified precautions. Some Toyota Prius HEVs

use a coolant storage bottle that keeps the coolant hot

for up to three days. Opening a coolant hose could

cause the release of this hot coolant and can cause

serious burns to the technician.

4. Always read, understand, and follow all of the serv-

ice information instructions when servicing the cooling

system on a hybrid electric vehicle.

AIR FILTER SERVICE Performing air filter service is similar to

performing this service in any vehicle equipped with an internal com-

bustion engine. However, there are several items to know when ser-

vicing the air filter on a hybrid electric vehicle, including the following:

A Bad Day Changing Oil

A shop owner was asked by a regular customer who

had just bought a Prius if the oil could be changed

there. The owner opened the hood, made sure the

filter was in stock (it is a standard Toyota filter used on

other models), and said yes. A technician with no prior

knowledge of hybrids drove the warmed-up vehicle

into the service bay. The internal combustion engine

never started, as it was in electric (stealth) mode at the

time. Not hearing the engine running, the technician

hoisted the vehicle into the air, removed the drain bolt,

and drained the oil into the oil drain unit. When the

filter was removed, oil started to fly around the shop.

The engine was in “standby” mode during the first part

of the oil change. When the voltage level dropped, the

onboard computer started the engine so that the HV

battery could recharge. The technician should have

removed the key to keep this from happening. Be sure

that the “ready” light is off before changing the oil or

doing any other service work that may cause personal

harm or harm to the vehicle if the engine starts.

REAL WORLD FIX

HYBRID SAFETY AND SERVICE PROCEDURES 405

5. Always read, understand, and follow all of the service in-

formation instructions when servicing the braking system

on a hybrid electric vehicle.

TIRES Performing tire-related service is similar to performing

this service in any vehicle equipped with an internal combustion

engine. However, there are several items to know when servicing

tires on a hybrid electric vehicle, including the following:

1. Tire pressure is very important to not only the fuel econ-

omy but also on the life of the tire. Lower inflation pressure

increases rolling resistance and reduces load carrying ca-

pacity and tire life. Always inflate the tires to the pressure

indicated on the door jamb sticker or found in service

information or the owner’s manual.

2. All tires create less rolling resistance as they wear. This means

that even if the same identical tire is used as a replacement,

the owner may experience a drop in fuel economy.

3. Tires can have a big effect on fuel economy. It is best to

warn the owner that replacement of the tires can and often

will cause a drop in fuel economy, even if low rolling resis-

tance tires are selected.

4. Try to avoid using tires that are larger than used from the

factory. The larger the tire, the heavier it is and it takes more

energy to rotate, resulting in a decrease in fuel economy.

5. Follow normal tire inspections and tire rotation intervals as

specified by the vehicle manufacturer.

AUXILIARY BATTERY TESTING AND SERVICE

Performing auxiliary battery service is similar to performing this

service in any vehicle equipped with an internal combustion

engine. However, there are several items to know when servic-

ing the auxiliary battery on a hybrid electric vehicle, including

the following:

1. Auxiliary 12-volt batteries used in hybrid electric vehicles

are located in one of two general locations.



Under the hood. If the 12-volt auxiliary battery is un-

der the hood it is generally a flooded-type lead-acid

battery and should be serviced the same as any con-

ventional battery.



In the passenger or trunk area. If the battery is lo-

cated in the passenger or truck area of the vehicle, it is

usually of the absorbed glass mat (AGM) design. This

type of battery requires that a special battery charger

that limits the charging voltage be used.

2. The auxiliary 12-volt battery is usually smaller than a bat-

tery used in a conventional vehicle because it is not used

to actually start the engine unless under extreme condi-

tions on Honda hybrids only.

3. The 12-volt auxiliary battery can be tested and serviced

the same as any battery used in a conventional vehicle.

4. Always read, understand, and follow all of the service in-

formation instructions when servicing the auxiliary battery

on a hybrid electric vehicle.

STEERING SYSTEM SERVICE Performing steering sys-

tem service is similar to performing this service in any vehicle

equipped with an internal combustion engine. However, there

are several items to know when servicing the steering system

on a hybrid electric vehicle, including the following:

1. Check service information for any precautions that are

specified to be followed when servicing the steering sys-

tem on a hybrid electric vehicle.

2. Most hybrid electric vehicles use an electric power steer-

ing system. These can be powered by one of two voltages:



12 volts. These systems can be identified by the red

or black wiring conduit and often use an inverter that

increases the voltage to operate the actuator motor

(usually to 42 volts). While this higher voltage is con-

tained in the controller and should not create a shock

hazard, always follow the specified safety precautions

and wear protective high-voltage gloves as needed.



42 volts. These systems use a yellow or blue plastic

conduit over the wires to help identify the possible

hazards from this voltage level. This voltage level is not

a shock hazard but can maintain an arc if a circuit car-

rying 42 volts is opened.

3. Always read, understand, and follow all of the service in-

formation instructions when servicing the steering system

on a hybrid electric vehicle.

BRAKING SYSTEM SERVICE Performing braking sys-

tem service is similar to performing this service in any vehicle

equipped with an internal combustion engine. However, there

are several items to know when servicing the braking system on

a hybrid electric vehicle, including the following:

1. Check service information for any precautions that are

specified to be followed when servicing the braking sys-

tem on a hybrid electric vehicle.

2. All hybrid electric vehicles use a regenerative braking sys-

tem, which captures the kinetic energy of the moving

vehicle and converts it to electrical energy and is sent

to the high-voltage battery pack. The amount of current

produced during hard braking can exceed 100 amperes.

This current is stored in the high-voltage battery pack and

is then used as needed to help power the vehicle.

3. The base brakes used on hybrid electric vehicles are the

same as any other conventional vehicle except for the

master cylinder and related control systems. There is no

high-voltage circuits associated with the braking system,

as the regeneration occurs inside the electric drive (trac-

tion) motors and is controlled by the motor controller.

4. The base brakes on many hybrid vehicles are often found

to be stuck or not functioning correctly because the brakes

are not doing much work and can rust.

NOTE: Always check the base brakes whenever there

is a poor fuel economy complaint heard from an owner

of a hybrid vehicle. Often when a disc brake caliper

sticks, the brakes drag but the driver is not aware of

any performance problems but the fuel economy drops.

406 CHAPTER 31

The cuff of the rubber glove should extend at least

1/2 inch beyond the cuff of the leather protector.

To determine correct glove size, use a soft tape to

measure around the palm of the hand. A measurement

of 9 inches would correspond with a glove size of 9.

The glove rating and the date of the last test should be

stamped on the glove cuff.

Start with a visual inspection of the glove fingertips,

making sure that no cuts or other damage is present.

The damage on this glove was easily detected with a

simple visual inspection. Note that the rubber glove mate-

rial can be damaged by petroleum products, detergents,

certain hand soaps, and talcum powder.

Manually inflate the glove to inspect for pinhole leaks.

Starting at the cuff, roll up the glove and trap air at the

finger end. Listen and watch carefully for deflation of the

glove. If a leak is detected, the glove must be discarded.

HV GLOVE USE

HYBRID SAFETY AND SERVICE PROCEDURES 407

STEP BY STEP

Petroleum on the leather protector’s surfaces will

damage the rubber glove underneath.

Glove powder (glove dust) should be used to absorb

moisture and reduce friction.

Put on the gloves and tighten the straps on the back of

the leather protectors.

Technicians MUST wear HV gloves and leather pro-

tectors whenever working around the high-voltage

areas of a hybrid electric vehicle.

HV gloves and leather protectors should be placed

in a canvas storage bag when not in use. Note the

ventilation hole at the bottom of this bag.

Make sure that the rubber gloves are not folded

when placed in the canvas bag. Folding increases

mechanical stress on the rubber and can lead to

premature failure of the glove material.

408 CHAPTER 31

4. The high-voltage system can be shut off at the battery

pack by simply being certain that the ignition is off. Discon-

necting the 12-volt battery is additional security that the

high-voltage circuits are depowered.

5. When servicing a hybrid electric vehicle, always observe

safety procedures.

1. Personal protective equipment (PPE) for work on hybrid

electric vehicles includes the wearing of high-voltage rub-

ber gloves rated at 1,000 volts or more worn with outer

leather gloves to help protect the rubber gloves.

2. A digital meter that meets CAT III standards should be

used when working around the high-voltage section of a

hybrid electric vehicle.

3. Safety glasses and a face shield should be worn whenever

working around the high-voltage circuits of a hybrid elec-

tric vehicle.

SUMMARY

3. What are the precautions that service technicians should

adhere to when servicing hybrid electric vehicles?

1. What are the recommended items that should be used

when working with the high-voltage circuits of a hybrid

electric vehicle?

2. What actions are needed to disable the high-voltage

circuit?

REVIEW QUESTIONS

4. If the engine is not running, Technician A says that the

high-voltage circuits are depowered. Technician B says

that all high-voltage wiring is orange-colored. Which tech-

nician is correct?

a. Technician A only

b. Technician B only

c. Both Technicians A and B

d. Neither Technician A nor B

5. Which statement is false about high-voltage wiring?

a. Connects the battery pack to the electric controller

b. Connects the controller to the motor/generator

c. Is electrically grounded to the frame (body) of the

vehicle

d. Is controlled by a relay that opens if the ignition is off

6. What routine service procedure could result in lower fuel

economy, which the owner may discover?

a. Using the wrong viscosity engine oil

b. Replacing tires

c. Replacing the air filter

d. Either a or b

1. Rubber gloves should be worn whenever working on or

near the high-voltage circuits or components of a hybrid

electric vehicle. Technician A says that the rubber gloves

should be rated at 1,000 volts or higher. Technician B says

that leather gloves should be worn over the high-voltage

rubber gloves. Which technician is correct?

a. Technician A only

b. Technician B only

c. Both Technicians A and B

d. Neither Technician A nor B

2. A CAT III-certified DMM should be used whenever measur-

ing high-voltage circuits or components. The CAT III rating

relates to ______________ .

a. High voltage

b. High energy

c. High electrical resistance

d. Both a and b

3. All of the following will shut off the high voltage to compo-

nents and circuits, except ______________ .

a. Opening the driver’s door

b. Turning the ignition off

c. Disconnecting the 12-volt auxiliary battery

d. Removing the main fuse, relay, or HV plug

CHAPTER QUIZ

HYBRID SAFETY AND SERVICE PROCEDURES 409

9. Nickel-metal hydride (NiMH) batteries can be damaged if ex-

posed to temperatures higher than about ______________ .

a. 150°F (66°C)

b. 175°F (79°C)

c. 200°F (93°C)

d. 225°F (107°C)

10. How should NiMH batteries be disposed?

a. In regular trash

b. Call an 800 number shown under the hood of the

vehicle for information

c. Submerged in water and then disposed of in regular

trash

d. Burned at an EPA-certified plant

7. Two technicians are discussing jump starting a hybrid elec-

tric vehicle. Technician A says that the high-voltage bat-

teries can be jumped on some HEV models. TechnicianB

says that the 12-volt auxiliary battery can be jumped using

a conventional jump box or jumper Which technician is

correct?

a. Technician A only

b. Technician B only

c. Both Technicians A and B

d. Neither Technician A nor B

8. What can occur if a hybrid electric vehicle is pushed in the

shop?

a. The high-voltage battery pack can be damaged

b. The tires will be locked unless the ignition is on

c. Damage to the electronic controller can occur

d. High voltage will be generated by the motor/generator

410 CHAPTER 32

chapter

OBJECTIVES: After studying Chapter 32 , the reader should be able to: • Explain how a fuel cell generates electricity.

• Describe the advantages and disadvantages of electric vehicles. • Discuss the advantages and disadvantages of fuel cells.

• List the types of fuel cells. • Explain how ultracapacitors work. • Discuss alternative energy sources.

KEY TERMS: Double-layer technology 415 • Electrolysis 410 • Electrolyte 412 • Energy carrier 410 • Energy density 413

• Farads 415 • Fuel cell 410 • Fuel-cell hybrid vehicle (FCHV) 411 • Fuel-cell stack 412 • Fuel-cell vehicle (FCV) 411

• Homogeneous charge compression ignition (HCCI) 419 • Hydraulic power assist (HPA) 419 • Inverter 416 • Low-grade

heat 414 • Membrane electrode assembly (MEA) 412 • NEDRA 422 • Plug-in hybrid electric vehicle (PHEV) 420 • Polymer

electrolyte fuel cell (PEFC) 412 •

Proton exchange membrane (PEM) 412 • Range 421 • Specific energy 410

• Ultracapacitor 414 • Wheel motors 416 • Wind farms 422

such as natural gas or crude oil. In order to store hydrogen for

use as a fuel, processes must be undertaken to separate it from

these materials.

 SEE FIGURE 32–2 .

BENEFITS OF A FUEL CELL A fuel cell can be used

to move a vehicle by generating electricity to power electric

drive motors as well as powering the remainder of the vehicle’s

FUEL CELLS AND

ADVANCED TECHNOLOGIES

HYDROGEN

FUEL CE

LL ELECTRIC

HYDROGEN

FUEL CEL

ECTR

FIGURE 32–1 Ford Motor Company has produced a number

of demonstration fuel-cell vehicles based on the Ford Focus.

HYDROGEN

WATER

BIOMASS

COAL

NATURAL GAS

PETROLEUM

ELECTROLYSIS

SOLAR POWER

WIND POWER

WATER POWER

OTHERS

FIGURE 32–2 Hydrogen does not exist by itself in nature.

Energy must be expended to separate it from other, more

complex materials.

FUEL-CELL TECHNOLOGY

WHAT IS A FUEL CELL? A fuel cell is an electrochemical

device in which the chemical energy of hydrogen and oxygen

is converted into electrical energy. The principle of the fuel

cell was first discovered in 1839 by Sir William Grove, a Welsh

physician. In the 1950s, NASA put this principle to work in

building devices for powering space exploration vehicles. In

the present day, fuel cells are being developed to power homes

and vehicles while producing low or zero emissions.

 SEE

FIGURE 32–1 .

The chemical reaction in a fuel cell is the opposite of elec-

trolysis. Electrolysis is the process in which electrical current is

passed through water in order to break it into its components,

hydrogen and oxygen. While energy is required to bring about

electrolysis, this same energy can be retrieved by allowing hy-

drogen and oxygen to reunite in a fuel cell. It is important to note

that while hydrogen can be used as a fuel, it is not an energy

source. Instead, hydrogen is only an energy carrier, as energy

must be expended to generate the hydrogen and store it so it

can be used as a fuel.

In simple terms, a fuel cell is a hydrogen-powered bat-

tery. Hydrogen is an excellent fuel because it has a very high

specific energy when compared to an equivalent amount of

fossil fuel. One kilogram (kg) of hydrogen has three times the

energy content as one kilogram of gasoline. Hydrogen is the

most abundant element on earth, but it does not exist by itself

in nature. This is because its natural tendency is to react with

oxygen in the atmosphere to form water (H

O). Hydrogen is also

found in many other compounds, most notably hydrocarbons,