Hydrogen Fuel-Cell Vehicles The Future of Transportation

Sam Glidden

Jared Delahanty

Project Advisor: Mike Mangini

June 2004

Table of Contents Introduction......................................................................................................................... 3 A Hydrogen Future ............................................................................................................. 4 System Overview................................................................................................................ 8 The Fuel Cell..................................................................................................................... 12 The Hydrogen Storage Tanks ........................................................................................... 23 The Motor ......................................................................................................................... 30 AC Motor Controller......................................................................................................... 34 Regenerative Braking........................................................................................................ 36 Intermediate Energy Storage............................................................................................. 38 Platform Vehicle and Modifications................................................................................. 46 Cooling.............................................................................................................................. 50 Performance Analysis ....................................................................................................... 51 Costs.................................................................................................................................. 60 Appendix 1: Sources of Hydrogen.................................................................................... 62 Appendix 2: How Safe is Hydrogen? ............................................................................... 64 Appendix 3: References.................................................................................................... 66

Special Thanks to:

The project received a generous donation from New York State Electric and Gas Co.

(NYSEG) to help with research and design.

We would like to thank Mike Mangini for donating countless hours answering our

questions, managing the administrative details of our project, and editing the final work.

We would also like to thank:

Charles Hanley, Mr. Engel, Mr. During, Mrs. Michaels, Mrs. Bustamante, Dryden High

School, Steve Glidden, Nancy Tomlinson, Scott Warren, Cathryn Ourtel.

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Introduction

We began this project as two seniors at our local high school looking for something extra

to do. Jared was interested in cars in general and was currently rebuilding an old Jaguar. I

have always been fascinated by the latest technology, and I was really interested in the

future of vehicular technology, especially because gas-electric hybrid cars were making

their debut. We both wanted to do something in that area and we had heard of cars

powered by hydrogen. This sounded perfect, because it was futuristic enough to be

exciting but practical enough to be possible. In fact, a little research showed us that

current automotive companies were building hydrogen car prototypes and that hydrogen

cars had a lot of potential. They could improve both the performance and environmental-

friendliness of vehicles. We were sold, and decided to turn our interest into something

real. After a little thought we went to Mike Mangini, our physics instructor, to propose an

independent study project through our school to design a hydrogen vehicle. We knew it

would be challenging but that it would also be possible; after all, hydrogen cars already

existed. The independent study project would give us motivation to see the project

through to the end and would give us a little extra credit. When the administrative details

were out of the way, we began to research and design.

Our project has two main goals. First we wish to learn more about fuel cells and

hydrogen technology with respect to automobiles. Secondly we want to educate to

community about the benefits and feasibility of hydrogen cars. We hope to dispel any

myths about the possibility that they would be underpowered, dangerous, or too

expensive. We want to encourage to adoption of hydrogen vehicle technology because it

can benefit all. By completing our project, we can show that it is possible to create an

efficient and practical vehicle.

This booklet is the attempt to complete those objectives. The further we delved into the

project, the more we realized how complex the situation really is. Every section of this

book could be many times as long as it is. The motor section alone could encompass

hundreds of pages discussing types, functions, efficiencies, powers, manufacturers, etc.,

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but we had neither the time nor the inclination to go that deeply into a specific topic. Will

our design create the best, most efficient vehicle? No – but it is a working vehicle, and

we did take into account everything we could. This car could be built, driven and used to

prove the technology.

A Hydrogen Future

As everyone knows, current vehicles are powered by an internal combustion engine that

runs off gasoline or diesel (fossil fuels). Current vehicles are also capable of nearly

everything we ask of them, whether it is reaching high speeds, pulling heavy loads or

undergoing rapid acceleration. However, the internal combustion engine is also a

century-old invention. Internal combustion engines are beginning to show signs of age.

Running off fossil fuels, they require a giant supply of oil. Without going into the politics

of it, securing this supply of oil has cost the United States and many other countries

billions of dollars, required compromising our values, and weakened the US

economically as we become increasingly dependant on foreign importation. The

dependence has, at the time of this writing, become particularly obvious as gas prices

soar past the $2 dollar a gallon mark. And because many people believe that we have

either reached or will soon reach the peak in the world’s supply of oil, prices will only

rise. The increasing scarcity of oil points to the imminent doom of the internal

combustion engine.

There is a second price to gasoline vehicles: pollution. Ignore it as some might, clouds of

smog hang over many of the country’s cities. This problem can be even worse in other

nations around the world. It is not fully known at this point what this smog does to our

health and how responsible it is for causing various cancers, leading to the national

increase in allergies and asthma, and creating other health problems. Burning oil in our

cars dumps an estimated 302 million metric tons of carbon dioxide into the atmosphere

each year. Many other greenhouse gases are also released. It is gradually becoming clear

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that global warming is a real problem, and at this point the only people who deny this are

people who don’t want to bother fixing it.

The gasoline engine is not something the planet can sustain for much longer, both in

terms of providing fuel and in terms of keeping the environment hospitable. The

development and adoption of alternative options now would enable the use of gasoline

engines for the next several hundred years at least. However, keeping and continuing to

expand the number of internal combustion engine vehicles will only hasten their

cataclysmic end when fuel supplies run out. We do not advocate abandoning oil power,

but we do feel that in order to preserve the technology for uses where it is required,

critical, or essential, we must stop wasting fuel in applications where other alternatives

exist. A gradual shift to alternative energy sources, beginning now, could reduce or

possibly even eliminate any economic plight that would be caused by the sudden

expiration of internal

combustion engines as a

usable technology.

The most obvious

alternatives to gasoline

engines are electric

motors. Electric motors

are, actually, far more

suited to a transportation

application than internal

combustion engines.

Electric motors sport far

higher efficiencies, lower

weights, and higher torques than their gasoline equivalents. Motors can also provide

adequate power over a large range of engine speeds, potentially eliminating the need for a

transmission in a vehicle. However, an electric motor system has one fatal downfall:

energy storage. A well-made internal combustion engine can propel a car for 30 or more

Figure 1: Under the hood of an electric car. The large metal box is the motor controller. Image from http://auto.howstuffworks.com/electric-car1.htm.

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miles per gallon of gasoline. Vehicular ranges average around 300 miles on a tank, with a

lot of variation depending on the vehicle. Hybrid vehicles, which feature the marriage of

internal combustion engines and electric motors, get even better mileage, still consuming

only oil. The best electric cars, however, can barely travel 100 miles on a full battery

charge. Unfortunately, the current generation of batteries is unable to hold enough energy

to power an electric car any further. The batteries are heavy, consume a lot of space and

take several hours to recharge. Consequently, electric vehicles have never become

practical alternatives to conventional cars. Also unfortunate is that in effort to squeeze the

highest possible mileage out of an electric vehicle, the electric motors have been

minimized to a size unable to match today’s standards of performance and power in

gasoline engines. This has fostered the myth that electric vehicles are not and cannot be

as powerful as conventional cars.

Dispelling this myth brings us to the topic of this booklet: hydrogen power. Hydrogen-

powered vehicles come in two types: hydrogen combustion engines and hydrogen fuel

cells. Through combustion, a hydrogen engine acts like an ordinary engine, except

hydrogen is burned in

the cylinders instead of

gasoline. However, this

requires the use of a

modified combustion

engine that still results

in the inefficiency

inherent of any

exothermic reaction.

The other option, using hydrogen fuel cells, is far better. Hydrogen fuel cells take

hydrogen and combine it with oxygen. This generates electricity. The electricity is then

used to power an electric motor, using the same technology as today’s electric vehicles.

Because the energy is stored in the form of hydrogen, and not in a battery, this enables

electric vehicles to carry significantly more energy. This allows for vehicles with larger

motors and longer ranges. In fact, with development, the average hydrogen vehicle

Figure 2: Honda’s FCX Fuel cell vehicle. Image from http://hondacorporate.com/?onload=fcx.

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should be able to go further and be more powerful than the average gasoline vehicle. The

use of hydrogen fuel cells will allow us to advance automotive technology to levels

unreachable in past times.

Hydrogen fuel cells overcome the two major flaws of internal combustion engines. First,

hydrogen is the universe’s most common element. There is no risk of ever running out.

As hydrogen can be produced from the

electrolysis of water, it can be made in any

county anywhere. The issue of importing

hydrogen will not exist. And because fuel cells

output water, there is no need to worry about

consuming the world’s water supply.

Essentially, the hydrogen can be manufactured

anywhere in large quantities by breaking down

water into oxygen and hydrogen. The hydrogen

is then distributed to the “gas” stations of the

future to fill your car. The car will be powered

by the fuel cells, which recombine the hydrogen with oxygen in the ambient air to form

all the water originally used. For more information on the manufacturing process of

creating hydrogen, see Appendix 1: Sources of Hydrogen.

Figure 3: A hydrogen fueling station that recently opened in Iceland. Image from Renewable Energy World at http://www.jxj.com/magsandj/rew/news/2003_04_04.html.

Secondly, hydrogen vehicle will not pollute. The fuel cell potentially enables a hydrogen

car to be completely environmentally friendly. Because a fuel cell needs only hydrogen

and oxygen, no carbon, greenhouse, or other harmful gases are produced. Oxygen is

already found freely in the air. The hydrogen involved is also not environmentally

damaging for two reasons. First, the pure hydrogen will be completely contained at all

times during the process, and will not come in contact with the outside world. Second,

even if any hydrogen does leak into the atmosphere, it will immediately combine with

atmospheric oxygen to form H2O (water). Water does not damage the environment.

Appendix 1: Sources of Hydrogen deals with the possible methods of obtaining the

necessary pure hydrogen and their various environmental impacts.

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Hydrogen vehicles have the potential to revolutionize the transportation industry.

However, the massive size of the automotive business makes it slow to change and

hesitant to adopt new technology. Only through public and political pressure will

hydrogen vehicles be developed within a reasonable time frame. Hydrogen could very

likely be the future. The sooner we reach that future, the sooner we decrease pollution of

the planet and cure the economic and political woes caused by a dependency on foreign

oil. This booklet is an effort to explain just how easy that future is to construct.

System Overview

Before we go into the details of a hydrogen vehicle, it is important to get a sense of how

the components work together. This overview shows each component and what it does to

power the car. The specific details concerning each component, such as manufacturing

and user specs, how we chose it, and what it does, can be found in the following sections

of this booklet.

The simple diagram on the following page shows the flow of energy through the vehicle.

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Hydrogen from the tanks and oxygen from the air combine in the fuel cells to generate

electricity. The fuel cell is the primary source of power in the vehicle. Running at a

maximum of 80 kW, it sends power to the motor controller. The more the driver pushes

down on the accelerator pedal (calling it a “gas” pedal is no longer accurate), the more

energy the controller asks for and the more energy the fuel cell puts out. Because the

preferred car motor is AC, not DC like the fuel cells and the rest of the system, the

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controller will convert the DC power from the fuel cells to AC of the correct frequency

and power to drive the motor. The motor outputs a maximum of 100 kW, powering a

fixed gearbox and the drivetrain. The car does not require a multi-gear transmission

because unlike internal combustion engines, electric motors can be made to yield high

torque over a wide RPM range. Gasoline engines operate best over a very small RPM

band and so a complex transmission is necessary to keep the engine running efficiently.

An electric motor is not so limited.

A hydrogen fuel-cell car should also have integrated regenerative braking. This

complicates the system somewhat. When the driver brakes, instead of conventional

brakes slowing the car through friction, the motor begins to act as a generator. Regulated

by the controller, which receives information the brake petal, the motor slows the car at

the desired rate. At the same time this generates electricity, which goes through the

controller, is converted from the AC of the motor to DC, and charges the ultracapacitors.

Hence, when the car brakes the ultracapacitors gather electricity. This increases vehicular

efficiency. The amount of heat generated when a conventional 2500 lb car brakes from

60 mph to rest is enough to light a 100 W bulb for an hour. This energy is normally

vented off to the atmosphere providing no useful function.

When the driver accelerates again, the ultracapacitors are drained to power the car.

During times of high acceleration, both the ultracapacitors and the fuel cell will be

powering the motor. Running the fuel cell at 80 kW and the ultracapacitors at 20 kW, the

motor can run at maximum output for 11.25 seconds before the ultracapacitors are

drained. The car should be able to reach 60 mph in that time. Additionally, if the car is

completely stopped, and the ultracapacitors are not fully charged, the fuel cell will turn

on and charge them. This assures the driver will have maximum acceleration when he or

she wants it.

To actually build the car, a more detailed electric schematic is needed. Voltages need to

match and current needs to fall within limits of the components. The result is a slightly

more complicated system.

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As you can see, a DC-to-DC converter is needed to up the voltage of the ultracapacitors

to match that of the fuel cell. Heavy gauge wiring will also be needed for most of the

circuit where the current reaches several hundred amps. The power output of the motor

during regenerative braking will vary on the rate at which the vehicle brakes. Therefore,

the power rate between the controller and the ultracapacitors will also vary. However, it

is important that it does not exceed 100 volts and 450 amps (45 kW) or it may overload

the ultracapacitors, destroying them. The controller can be set to prevent this problem.

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The diode and switch system between the ultracapacitors and fuel cell tie the

ultracapacitors into the system. The diode allows the ultracapacitors to power the

controller without current flowing from the fuel cells towards the ultracapacitors. As

such, the switch is open during normal driving. However, when the car comes to a

complete stop, the switch will close. The ultracapacitors can then be refilled by the fuel

cell is they are not already full from regenerative braking. The driver will thereby have

fully charged ultracaps to assure he or she has maximum power for the next acceleration.

Most of the remainder of this book is intended to describe each individual component and

how we arrived at the various specifications for them. Details on the physical locations of

various components can be found in the Platform Vehicle and Modifications section.

The Fuel Cell

The fuel cell is the heart of a hydrogen-powered vehicle. A fuel cell uses the combination

of hydrogen and oxygen to generate electricity. The side effect of this process is the

generation of water and heat. The electricity can then be used to power the car. The fuel

cell is the primary device that turns ordinary electrical vehicles into a practical,

competitive alternative.

An Extremely Brief History

Fuel cells were first invented back in 1839. However, it was not until the 1960s that

NASA demonstrated the first practical use of fuel cells in space flight. From there the

technology has grown. In the 1990s fuel cells began to become a viable option for

powering a car. The late 1990s and the 2000s saw the first prototype hydrogen vehicles.

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Types of Fuel Cells

There are multiple types of fuel cells. Each has different operating conditions and some

use a fuel other than pure hydrogen. For example, methanol fuel cells are commonly

used. They break down methanol into hydrogen and carbon, and then combine the

hydrogen with oxygen to produce water and energy. However, they release the carbon

into the atmosphere, thereby polluting. The only practical type of fuel cell for a clean,

efficient vehicle is a Proton Exchange Membrane cell (PEM). PEMs are the most suitable

type of fuel cell for vehicular applications because of their lower operating temperature.

(They operate at the lowest temperature, around 80 degrees Celsius. Other cells require

higher temperatures, which makes them unsuitable for a vehicular application.) PEM fuel

cells rely on the simple combination of hydrogen and oxygen to produce electricity. At

all points in this book, whenever “fuel cell” is mentioned, we are talking about PEM fuel

cells.

How Fuel Cells Work

The basic concept behind how a fuel cell works is very simple. The following illustration

from Ballard Power Systems provides an excellent view into the workings of a fuel cell.

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On the left side of this illustration, hydrogen enters the fuel cell. On the right, oxygen is

provided. Hydrogen is a reactive element, and will combine with oxygen given the

opportunity. Each hydrogen molecule, H2, has two hydrogen atoms each with one

electron. The oxygen has 6 valence electrons. The rules of chemistry tell us that each

atom is in its most stable state when it has a full outer shell of electrons, which for

hydrogen is 2 electrons and for oxygen is 8. Each atom tries to move towards this optimal

quantity and arrangement of electrons by binding with other atoms. In this case, each

oxygen atom needs two more electrons. Each hydrogen atom needs one. The oxygen will

therefore pull in two hydrogen atoms to fill its valence electron shell to a total of eight

electrons. Each hydrogen atom, in return, shares one of the oxygen’s electrons, resulting

in a full shell of 2 electrons to stabilize the hydrogen.

This process requires the hydrogen and oxygen to bind together, and in the above

illustration, they are on opposite sides of the fuel cell. The hydrogen, being the smaller

atom, is more mobile and is pulled to the right. To reach the oxygen atom the hydrogen

Figure 4: Fuel Cell Illustration from Ballard Power System – http://www.ballard.com

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must pass though the Proton Exchange Membrane. The PEM membrane, as its name

suggests, allows only the passage of a proton, which happens to be the nucleus of a

hydrogen atom. As the hydrogen atom passes through the membrane the hydrogen’s

electron is left behind. Upon reaching the oxygen, the hydrogen nucleus is joined by

another which also crossed the membrane, and both bond to the oxygen. However, the

oxygen-hydrogen complex (which is H20 – water) is missing the two electrons that the

two hydrogen atoms left behind when they crossed the PEM membrane. The oxygen is

not yet satisfied because it still only has 6 valance electrons as the hydrogen arrived

without any. The hydrogen-oxygen complex is therefore positively charged, because

electrons carry a negative charge and the hydrogen-oxygen complex is missing two.

Meanwhile, the left side of the fuel cell, where the hydrogen originally was, now has two

extra electrons.

An electric circuit connects the two sides of the cell. The electrons (negatively charged)

he output of the fuel cell is obviously electricity, and also water (the hydrogen-oxygen

are drawn around the circuit, attracted to the hydrogen-oxygen complex because it is

positively charge. The only path to the oxygen is along the electric circuit. The potential

difference in charges (positive and negative) between each side of the cell creates

voltage, generally in the range of 1 to 2 volts for a PEM cell. If the electric circuit is

closed, the electrons are allowed to cross over to the hydrogen-oxygen complex,

generating current. There is now electricity that can be used to turn a motor and power a

car. To produce enough electricity to do this, many of the single cells illustrated above

are connected together in series to generate higher voltage.

T

complex with the two electrons) and heat. The fuel cell therefore needs to dissipate this

heat into either the ambient air or a water system; more details on this can be found in the

Cooling section.

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Development

urrent hydrogen fuel cells need further development before they will be able to replace

ydrogen fuel cells also face several other issues that are rapidly being solved. The first

C

internal combustion engines. The present generation of fuel cells requires expensive

metals such as platinum, which is required as a catalyst to speed the reaction between the

hydrogen and oxygen. Additionally, fuel cells today require very pure hydrogen gas.

Hydrogen gas with small amounts (even fractions of a percent) of sulfur or carbon in it

will cause degradation of the fuel cell by binding to the platinum catalyst. This decreases

both efficiency and lifetime. Obtaining hydrogen without any impurities is difficult and

expensive. Therefore, current fuel cells are not cost-effective. However, research is

underway at Cornell University, other universities, and the private sector to solve these

problems. While today’s fuel cells cost tens of thousands of dollars, tomorrow’s could be

far cheaper.

H

concerns temperature. To operate, a PEM fuel cell must run at 80 degrees Celsius to

perform the hydrogen-oxygen combination. Fuel cells consequently have trouble in lower

temperatures. However, this issue can simply be solved by proper thermal management

and providing the cell with a heater when necessary. The other major issue concerns

start-up times; many fuel cells take several minutes to warm up before a car can begin

driving. However, this has recently improved – a fuel cell system by the manufacturer

Ballard Power Systems can start in less than 40 seconds. Most people give their cars a

few seconds to warm up when they first start them, and so this amount of time is not

unreasonable. It should also improve even further in the future. The final issue is weight;

a current 80 kW fuel cells weighs nearly 500 lbs (220 kg). This is a significant fraction

of the total weight of a vehicle and consequently degrades the vehicle’s performance.

However, this issue can be solved hand in hand with the cost issue – a cheaper fuel cell

would by necessity use lesser amounts of platinum and would therefore weigh less.

Additionally, clever designing of the car can decrease the weight of other systems so the

fuel cell’s weight becomes less onerous.

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Fuel Cell Size

he size (i.e. power output) of the fuel cell depends on the desired performance of the

s noted in both the sections on Intermediate Power Storage and Regenerative Braking

here are several things to consider when determining the size of the fuel cell.

1. A higher number of ultracapacitors will decrease the required size of the fuel cell.

, but

T

vehicle. Because the fuel cell is the most costly component of a hydrogen car, it is

important to keep its size to a minimum. What this booklet refers to as the “fuel cell”

actually consists of numerous small fuel cells stacked together to generate the necessary

voltage and current. Therefore, minimizing the required kW output of the overall cell will

decrease its size more or less proportionally.

A

the main way to decrease the output requirements of the fuel cell in a car is by

augmenting it with ultracapacitors. The ultracapacitors provide extra power during cases

of high acceleration. This power comes from either of two sources: first, regenerative

braking will charge the car whenever it decelerates; and second, in the event that

regenerative braking doesn’t provide the necessary power, the fuel cell will charge the

ultracapacitors when the vehicle is at a complete stop. Therefore, when the driver wants

the maximum amount of power the motor can provide (which is 100 kW – see the Motor

section), the fuel cells need not provide all that power because a portion of it can come

from the charged ultracapacitors. The key to this strategy is finding the balance between

fuel cells and ultracapacitors. Draining the ultracapacitors at their maximum rate will

empty them quickly, leaving the fuels cell to provide the remaining power to finish the

acceleration. However, the alternative is to increase the size of the fuel cell, thereby

increasing the weight and cost of the vehicle.

T

2. The combination of fuel cell and ultracapacitors should not exceed 100 kW.

3. Running the ultracaps at maximum power will allow for the smallest fuel cell

the ultracaps will most likely be drained before the driver finishes accelerating.

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The driver will then have to finish the acceleration using only a smaller fuel cell.

This will greatly decrease the vehicle’s performance on a 0 to 60 speed test.

4. As vehicle weight can vary several hundreds pounds depending on the car model,

equipment, etc., the estimated performance relies on the optimism or pessimism

of the designer. This makes choosing the optimal balance between fuel cells and

ultracapacitors difficult.

In light of all this, we have chosen to present several fuel cell solutions. Given an

unlimited budget, we would obviously choose the most powerful combination. However,

the car can be made more economical by sacrificing some performance.

We propose three possible solutions: Maximizing the fuel cell so the ultracapacitors will

be guaranteed to last for more than the duration of any given acceleration; minimizing the

fuel cell to reduce the cost of the powerplant, but causing the car’s 0 to 60 mph time to

increase; or finding an intermediate solution preserving some performance and some

economy between the two.

This data comes from other sections of this booklet:

Ultracapacitor Max Output 45 kW

Ultracapacitor Total Storage 225,000 Joules

Estimated Vehicle Weight 1350 – 1590

(3000 – 3500 lbs)

Max Motor/Controller Power 100 kW

Solution 1: Large Fuel Cell

Either of the two motors we selected in the Motor section should enable the vehicle to

reach 60 mph in around 10 seconds. This will be considered the basis for a conservative

fuel cell estimate; the sum of the ultracapacitors’ and the fuel cell’s power output should

equal 100 kW for a duration exceeding 10 seconds.

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The ultracapacitors store 225,000 joules,

225,000 J / 10 sec = 22.5 kW

Because this is the high performance option and to assure the ultracaps will last more

than the necessary 10 seconds, we will rely on the ultracapacitors to store about 90% of

their rated capacity, or 20 kW instead of 22.5 kW. This will allow the ultracaps to run for

11.25 seconds before being drained.

100 kW – 20 kW = 80 kW fuel cell

Therefore, a high performance car would need an 80 kW fuel cell.

Solution 2: Minimal Fuel Cell

It is slightly harder to determine the minimum size the fuel cell can be. Theoretically a

car could get by with a fuel cell only large enough to overcome wind resistance and

friction at the max cruising speed. Depending on the car body, this will be less than 20

kW. In this situation, however, acceleration would be terrible. Because the ultracaps

maximum output is 45 kW, the motor would never have enough power to reach its full

potential. Therefore, without redesigning the entire vehicle, the smallest the fuel cell

should be is 55 kW.

225,000 J / 45 kW = 5 seconds

Because the ultracapacitors will be emptied after 5 seconds, it will only be possible to run

the motor at full power for 5 seconds. However, these five seconds would enable the

vehicle to reach a speed of around 40 mph. After that, the motor will run off only the 55

kW fuel cell. Any remaining acceleration after the initial 5 seconds will be poor.

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On the other hand, the decrease in weight resulting from the drop in fuel cell size would

help compensate for the lower power which the motor would run at. In fact, going with a

smaller fuel cell would make sense if the motor power was also decreased by 20 or 30

kW.

However, the goal of this project has always been to create a high performance hydrogen

vehicle that could compete directly with most consumer gasoline cars. While minimizing

the fuel cell size would result in an economical, slightly more efficient vehicle, it would

also have poor acceleration. A poor performing vehicle would lead to the public

perception that hydrogen electric vehicles are sluggish performers as compared to

combustion vehicles. This is a myth we are trying to dispel. Minimizing the fuel cell size

is not the option we would choose for our vehicle.

Solution 3: A Compromise

The final option involves meeting a compromise between performance and economy.

Having an 80 kW fuel cell could be considered by some to be overkill. In standard

driving, most drivers do not push their vehicle to the limit. A 15 to 20 second acceleration

from 0 to 60 mph is perfectly acceptable most of the time. Decreasing the fuel cell

somewhat would still provide decent performance by allowing the ultracapacitors to last a

reasonable duration. If the fuel cell was decreased from 80 kW to 70 kW, that would

require running the ultracaps at 30 kW to achieve maximum acceleration.

225,000 / 30 kW = 7.5 seconds

The driver would therefore have 7.5 seconds of full acceleration before the ultracaps gave

out. This would enable the driver to make a rapid acceleration into heavy traffic on a

freeway, for instance. While it is unlikely the driver could go from 0 to 60 in that time, it

would provide the opportunity to get up to 45 or 50 before acceleration slowed. Finally,

because the performance estimates are based around a heavier car with an 80 kW cell,

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acceleration would improve simply because the vehicle weighs less. Those 7.5 seconds of

full acceleration would get a 70 kW vehicle going faster than it would an 80 kW one.

Specs Solution 1 Solution 2 Solution 3

Fuel Cell Size 80 kW 55 kW 70 kW

Ultracap Power Rate 20 kW 45 kW 30 kW

Duration of 100 kW power 11.25 seconds 5 seconds 7.5 seconds

0 to 60 mph time

(see the Performance section)

~10 seconds

For our vehicle, Solution 1 would be the best. Because our goals are to maximize

performance, the largest fuel cell is the most appropriate. However, Solution 3 would

make a good compromise; acceleration would still be reasonable, and weight would be

decreased. If a 70 kW fuel cell were much cheaper or easier to produce, Solution 3 would

make sense. For Solution 2 to be practical, a redesign of the vehicle, with an emphasis on

economy and efficiency, is needed. Various elements, such as the motor size, should be

changed.

Fuel Cell Control

There are several aspects to the support systems for hydrogen fuel cells. This system

obviously varies by manufacturer. The primary need is to regulate the flow of hydrogen

from the fuel tank and oxygen from the air to the fuel cell. The delivery rate of these

gases will need to vary with the instantaneous power output of the fuel cell. The control

system will therefore need to communicate with the motor controller to provide the

correct amount of power at the required times. There will also need to be some sort of

control to regulate the cooling system.

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Ballard Fuel Cell System

As mentioned, Ballard Power Systems is the leading manufacturer of fuel cells for

vehicles. The majority of prototype hydrogen vehicles made by the major car

manufacturers (Ford,

GM, Honda, Toyota,

etc) use a Ballard Fuel

Cell. Ballard provides

a fuel cell and control

system, which is

likely what we would

use in our car.

Figure 5: Ballard Mark 902 Fuel Cell from http://www. ballard.com

The fuel cells can be

built to output a wide

range of different

power levels. An 80

kW fuel cell is near the norm for light transportation vehicle applications. Along with the

basic cell, called a Mark 902, Ballard provides the Xcellsis HY-80 system. It includes all

the necessary support systems. The control unit communicates with the motor controller

via a CAN bus, the standard for vehicle systems and found on our chosen controllers. No

doubt a little programming will be necessary to get the controller and control unit to

communicate properly, but it shouldn’t be too difficult. The fuel cell control unit tells the

system module to send hydrogen and oxygen to the fuel cell. The system module also

humidifies, heats, and compresses ambient air containing the oxygen to the correct levels

necessary for the fuel cells. A power distribution module measures and regulates the

output power of the cell. The Xcellsis also includes a cooling pump. Another useful

feature is a built-in 12 volt output so that 12 V car systems can easily be integrated.

Finally, the entire system can be configured in different packages to fit into various

chassis types. The Xcellsis is designed to output only 68 kW, but a slight variation of the

system to include a larger fuel cell should not be difficult.

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Ballard Fuel Cell Mark 902 (no control system)

Rated net power 85 kW continuous

Current (maximum) 300 Amps

DC voltage (minimum) 284 Volts

Weight 96 kg (212 lbs)

Volume 75 liters (2.7 cubic ft)

Xcellsis HY-80 system (customizable; includes fuel cell such as Mark 902)

Max efficiency 48%

Start-up time < 40 seconds

Operating temperature < 85 degrees C

Weight 220 kg (485 lbs)

Volume 220 liters

Hydrogen Interface Pressure 10–13 bara (130–175 psig)

Max Power output 68 kW

The Hydrogen Storage Tanks

A hydrogen car needs hydrogen, obviously. The car is powered by the energy given off

by the combination of hydrogen and oxygen into water. Oxygen is readily available from

the air, but hydrogen must be supplied by a separate source.

The traditional method for storing hydrogen (or any other gas) is in a pressurized tank.

This is the storage method we have opted for here, but it does, however, have several

disadvantages. Hydrogen is a very low-density gas, and so to store the necessary quantity

to provide adequate driving range to a car, very large or high-pressure tanks are required.

This is obviously not all that desirable because high pressures can be dangerous and

difficult to use and larger tanks consume a lot of vehicle space and weight. However, as

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hydrogen storage tanks increase in pressure – the latest are available at pressures up to

10,000 psi – vehicle range rivals that of conventional gasoline vehicles.

There are several other methods of storing hydrogen that

look promising for the future. None have reached a point

where they can be integrated into our car, but ten years

from now they may well have replaced compressed

hydrogen tanks. The first option involves storing

hydrogen by binding it in a metal. The metal compound is

heated, and it absorbs hydrogen. Done correctly, this

allows for the storage of more hydrogen molecules per

volume than with pressurized tanks. However, the total

weight per mole of hydrogen is more than with

conventional pressurized tanks. The process is also more

complicated; the metal has to be heated when hydrogen is

being pumped in, and heated again to get the hydrogen

out. This would create an additional drain on a fuel cell in

a car, decreasing the overall efficiency slightly. This

system also has another advantage: even if the tank is broken open, the hydrogen cannot

leak out because it is bound to the metal. The car becomes even safer in an accident

because a hydrogen fire would be extremely unlikely.

Figure 6: A seemly ordinary hydrogen tank, the BL-400 can actually store up to 400 liters of H2 by compressing it into a metal. Image from fuelcellstore.com.

Another option is storing hydrogen as a liquid instead of a gas. However, to liquefy,

hydrogen must decrease to a temperature only 20 K above absolute zero. This requires

quite a lot of energy, and it is difficult to maintain such a low temperature in a car. While

a few prototype vehicles exist that store hydrogen as a liquid, it is unlikely this technique

will become a practical option given our current technology.

Other schemes are also in development. One of the more promising options involves

storing hydrogen in carbon nanotubes. Like metal storage, this increases the number of

24

hydrogen molecules per volume, thus creating smaller fuel tanks and longer vehicle

range. This option is still too new to be considered at this point.

Consequently, the most viable plan at this time is to use hydrogen storage tanks with

5000 psi compression capabilities, which is the current industry standard for such

applications.

Vehicular Hydrogen Requirements

The size of the tanks used will depend on the amount of hydrogen the vehicle needs. The

car requires a range of around 250 miles per tank to be competitive.

250 miles = about 400 kilometers

It would be extremely difficult to calculate the average number of joules a car expends

going 250 miles. However, a rough estimate can be done by calculating air resistance of a

vehicle going 60 mph for 250 miles. Rolling resistance is less significant than air

resistance, and can vary widely depending on a number of factors concerning the vehicle,

tires, and road surface. It will be left out of this estimate. Because we have regenerative

braking, much of the excess energy used in acceleration during this hypothetical trip will

be regained during braking. For the sake of simplicity, acceleration will be ignored; it

will be assumed that the car begins and ends the 250 mile trip going 60 mph. These

assumptions will doubtlessly cause the fuel estimation to be optimistically low.

The proposed vehicle (see Performance Calculations) loses approximates 6.3 kW of

power to air resistance during a 250 mile trip at 60 mph.

250 miles / 60 mph = 4.17 hours

6.3 kW * 4.17 hours = 26.271 kWh (9.5 x 107 joules)

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Therefore, it takes 9.5 x 107 joules to move a car 250 miles at 60 mph.

Hydrogen holds 118,800 kJ (33 kWh) of energy per kilogram. This turns out to be

remarkably similar to the amount of energy per gallon of gas. Like a combustion engine,

however, a fuel cell is not 100 % efficient. Some of the energy is converted into heat.

Then, of course, there are further inefficiencies within the vehicle which need to be taken

into account.

50% Fuel Cell * 90% Controller * 90% Motor * 90% Drivetrain = 36% total efficiency

These estimates are slightly conservative; a well designed AC motor can reach

efficiencies of over 95%, and the drivetrain, if a fixed gearbox is used instead of a

transmission, should also be better. PEM fuel cells theoretically max out at an efficiency

of 83%, a number yielded from calculating the resulting energy from the combustion of

oxygen and hydrogen. In the future, there is no reason to suspect fuel cells will not move

closer towards their maximum theoretical efficiency. For the record, gasoline engines are

about 15% efficient, with those in larger SUVs and trucks obviously even less.

118,800 J * 36% = 42,768 J of usable energy / kg of H2

9.5 x 107 J / 4.28 x 104 J/kg = 2.2 kg of hydrogen

A way to check this estimation is by looking at current prototype vehicles.

Prototype Vehicle Year Range Hydrogen (kg)

Honda FCX 2002 220 miles 3.75 kg

Toyota FCHV-4 2001 155 miles ~ 3 kg

GM Hy-Wire ? 80 miles 2 kg

Ford Focus FCV-Hybrid 2004 160-200 miles 4 kg ?

26

As you can see, there is quite a lot of variation in vehicle range. The range depends just

as much on other factors as it does on the amount of hydrogen fuel the vehicle has at its

disposal. However, it can be seen that the estimation reached earlier is optimistic. This

makes sense, considering that rolling resistance and acceleration were both ignored.

Nevertheless, by looking at our estimation and the real-world prototypes, the H2 quantity

necessary can be realistically estimated. The car should be able to hold at least 3 kg of

hydrogen and closer to 3.5 kg if possible. This will hopefully enable around 250 miles

per tank at highway driving speeds. City driving will probably cut down on the range;

however, regenerative braking will make up a portion of the potential losses.

While 3 kg of hydrogen may not sound like a lot, it is considerable when you calculate

the volume it would occupy at standard pressure. H2 has a molar mass of 2, and so 3000

grams (3 kg = 3000 g) equals 1500 moles. At STP (standard temperature – 25 degrees C,

and pressure – sea level) an ideal gas such as hydrogen occupies 22.4 liters of space per

mole.

22.4 * 1,500 = 33,600 liters

As 3 kg of hydrogen could fill 33,600 liters of space, you can see why extreme pressures

are needed to compress it to a practical volume.

The Tanks

One manufacturer of hydrogen tanks is Dynetek Industries Ltd. They build 5000 psi

hydrogen tanks specifically for vehicular applications that are lightweight and have fast-

filling capabilities. This is important, because filling a tank to 5000 psi suddenly creates a

lot of friction and heat. Dynetek’s tanks are designed to handle this, enabling refueling

times on the order of minutes.

The tanks are still rather large and heavy compared to the amount of hydrogen they store.

Dynetek’s largest tanks are nearly 7 feet long, and unless the chassis has been specifically

designed to accommodate this, the tank is impractical due to its weight and size.

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However, smaller tanks do not hold more than 2 kg. In a smaller car, therefore, the only

reasonable option is to use two or more smaller tanks. This will complicate the fuel

system, but may be necessary to provide the vehicle with a range comparable to

combustion vehicles.

Model Size Weight Capacity per tank

V 74 (x2) 399 x 900 mm (15.7 x 35.4”) 35.4 kg (78 lbs) 1.79 kg

W 150 413 x 1534 mm (16.3x60.4”) 65.6 kg (144.5 lbs) 3.63 kg

Either option above would work. One model W 150 would be sufficient; however, it is

over 5 feet long. If it could fit in the vehicle, it would allow for the simplest refueling and

hydrogen gas line plumbing.

The other option, two V 74s, would provide a total storage of 3.58 kg of hydrogen.

However, additional fuel lines would be necessary to connect the two tanks.

Unfortunately, while the simplest method would be to connect the two tanks together

with a gas line and treat them as a single tank, it is not a good idea to have a thin fuel line

pumped at 5000 psi. The line should be able to handle it, but it is dangerous to have a fuel

line at such a high pressure when driving. The tanks are specifically designed to resist

breaking in a collision to minimize the amount of hydrogen that could leak into the

atmosphere. Having a 5000 psi line connecting the two tanks would cancel out some of

this built-in safety. Consequently, the pressure will need to be stepped down by valves at

the exit of each tank to the lower pressure used by the fuel cell. Only then can the two

tanks be merged into one fuel line, going to the fuel cell. It may also be necessary to fill

each tank independently when refueling the car, although clever designing could get

around this.

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Hydrogen Fuel Lines

The two schemes for fuel lines depend on the tanks chosen above. A W 150 would need

only a connection to the outside of the car and to the fuel cell. Two V74s would also need

to be connected together. The two diagrams on the next page illustrate the two schemes.

Figure 7: A single tank (W150) system. As you can see, it is extremely simple.

Figure 8: A double tank (two V 74s) system. It is only slightly more complicated.

The hydrogen gas lines themselves would be fairly simple. They could be made out of

thin flexible metal pipe as the hydrogen flow rate is small. Ideally, the hydrogen tanks

would be located next to the fuel cell, so the length of the fuel lines and the consequent

29

risk they would pose in an accident would be minimized. The tanks also need to be

located so they can be conveniently refilled.

The Motor

In place of the combustion engine powering modern automobiles, a fuel cell vehicle

receives its mechanical power from an electric motor. As mentioned in the Hydrogen

Future section of this booklet, electric motors are particularly well suited to powering

vehicles as they have relatively high torque outputs and wide rpm operating ranges when

compared to standard combustion engines. Both DC and AC motors can be used in conjunction with fuel cell systems; however,

there are several fundamental and significant differences to consider when selecting a

motor. DC motors are much simpler to install and control and for this reason they are

historically found in earlier or homemade

electric vehicles. A DC motor system is

also less expensive, particularly because

the DC motor controllers are much less

complex than AC controllers. Also of

note, most DC motors can be driven far

above their rated limits for short amounts

of time. This allows for added power in

acceleration, which is ideal for automotive

applications. Despite being inexpensive

and simple to control there are many

drawbacks to DC motors. DC motors of

the size needed to power a vehicle are not commonly mass manufactured and can be hard

to find. They also require more maintenance and the motor itself is more complicated

Figure 9: A NetGain WarP 9" DC motor. We were seriously considering this motor before we decided to go AC. Image from http://www.go-ev.com/misc/Motor.pdf.

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than a comparable AC motor. Finally, one of the most grievous downfalls of DC motors

is that they are inefficient when used as a generator and are seldom used in conjunction

with regenerative braking systems.

AC motors have numerous disadvantages as well. AC motors require an AC power

source, and since the rest of the electrical systems run on DC power, this requires at least

one and possibly several DC to AC power converters. However, many AC motor

controllers include built in power converters, which could reduce or eliminate the use of

separate power converters. Unfortunately AC motor controllers are very expensive due to

the complex nature of controlling an AC motor, another downfall of an AC motor system.

In our design we decided an AC motor would best fit our needs due to the great

efficiency of the motor when used in regenerative braking, the simplicity and reliability

of AC motors, the low cost of the motor, and because AC motors are widely

manufactured in the size, weight, and power, requirements we anticipate for use in

powering an automobile.

The following table outlines the motor specifications we find necessary. These were

determined both by calculating the power required to accelerate a vehicle at the pace we

want, and by looking at currently available motors on the market for electric vehicles.

The following specs match what most electric-vehicle manufacturers consider

“performance” components.

Average Power 20 kW

Maximum Power 100 kW

Maximum Torque 100+ ft/lbs

Maximum Weight 200 lbs

The average desired power is the energy needed to overcome rolling friction and wind

resistance. Most of the time a vehicle is not accelerating, and so the only thing the motor

is overcoming is friction. Consequently, the average power requirement is low. Both the

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maximum power and torque need to be high, however, because we want the vehicle to

have competitive performance. Torque is the primary determinate for acceleration

whereas maximum power determines top speed. We wanted a maximum torque of at least

100 lb-ft, and more if we can get it. Acceleration is critical to the success of a vehicle.

However, few motors currently designed for electric vehicles have torques much higher

than 100 lb-ft without having excessive weight and maximum power. Weight needs to be

kept down for obvious reasons; the lighter the car, the better the performance.

Such motors are not exceedingly hard to come by, and we have found two motors that

meet our requirements and that we are considering for our design. Both the MES 200-

250 and the Siemens 1PV5133-4WS18 are feasible..

The following is a chart of the specifications of both the MES 200-250 and the Siemens

1PV5133-4WS18.

Specification MES 200-250 Siemens 1PV5133-4WS18

Average Power 30 kW (40.8 hp) 30 kW (40.8 hp)

Maximum Power 94.8 kW (123 hp) 78.4 kW (106.6 hp)

Weight 61 kg (134 lb) 68 kg (150 lb)

Rated Torque 100 Nm (73.8 ft-lb) 85 Nm (62 ft-lb)

Maximum Torque n/a (estimated 250 Nm) 175 Nm (129 ft-lb)

Rated RPM 2,850 RPM 3,500 RPM

Maximum RPM 9,000 RPM 9,700 RPM

The MES 200-250 is our preferred motor as it has specifications that are slightly more

favorable to our project. The MES unit weighs 134 lb, which is a reasonably low weight.

The power, RPM and torque are all reasonable, and the engine can be bought with an

attached gearbox, which is extremely useful for our design. The Siemens 1PV5133-

4WS18 is similar; however, its rpm range is slightly higher, max at 9,700. It is slightly

less powerful, max power of 78.4 kW and 106.6 hp. And it weighs 150 lb. Additionally

the Siemens motor does not have a gearbox available; because of this we would need a

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custom designed and manufactured

gearbox that might be fairly

expensive. Ideally we would like to

have a higher torque, lower weight

motor that has a very wide rpm band

and a straighter torque curve. While

the motors we selected aren’t prefect

in these aspects they are a much

closer fit than the combustion

engines currently being used in the

automotive industry. Figure 10: The MES 200-250 AC motor. Image from metricmind.com.

For information on specific performance of these two motors, see the section on

Vehicular Performance.

The Transmission

A transmission is not necessary in a hydrogen car because of the superior nature of

electric motors. Electric motor’s wide RPM range allows them to power the car through a

direct gear ratio and stay efficient over the full spectrum of speeds. Electric motors create

the highest torque at lower

RPMs, which is when the

majority of vehicles need it the

most. At higher speeds the torque

decreases (as it does in a gasoline

engine with a transmission) and

consequently acceleration at high

speeds will not be as effective as

at low speeds. This, however, is

similar to performance of

vehicles today. In the future,

Figure 11: MES-DEA Carraro gear box. Image from metricmind.com.

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motors may be mass-produced and perfected to deliver higher torque over even wider

ranges, thus making acceleration at all speeds excellent. Skipping a transmission is yet

one more way in which hydrogen cars can be more efficient and simpler than internal

combustion vehicles.

An electric motor will still need a fixed gear box to provide the most efficient use of the

motor’s torque. The MES 200-250 comes with a fixed gear transmission designed to fit

the motor.

AC Motor Controller

An AC motor will need an AC controller. The car will need some way for signals from

the driver’s foot pressing on the accelerator petal to reach the motor and tell it to

accelerate. Compared to the simpler DC motor, an AC motor is trickier to control – with

DC, these signals could directly control the current running the motor. An AC motor,

however, requires a controller that can read the amount that the driver has pushed down

on the petal and then transform the DC power coming from the fuel cells to the correct

amount and frequency of AC power. This is primarily why AC controllers are more

expensive. Additionally, there may be slightly more power

losses in an AC controller, but this is balanced by the fact

that the average AC motor is more efficient.

Figure 12: A Bosch potentiometer designed to be attached to the accelerator petal. Image from metricmind.com.

The AC controller behaves in response to the petal, which in

this case is connected to a potentiometer. A waterproof

potentiometer designed to work with these controllers via a

RS232 interface is made by Bosch. It can easily be attached

to a foot petal.

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The AC controller also makes regenerative braking possible. Most commercial AC

controllers (designed for conventional electric vehicles) have regenerative braking built

in, as it is not very difficult to integrate. Most DC controllers, on the other hand, lack this

important feature. This was considered in the Motor section.

The choice of AC controller depends largely on the AC motor used. Each manufacturer

(Siemens and MES-DEA) produces a motor controller designed specifically for their

motor. Matching the manufacture’s controller with the manufacture’s motor will result in

the greatest efficiency and the easiest setup. Therefore, the final decision on the controller

will go hand in hand

with the motor.

The Siemens Simotion

or the MES-DEA

TIM-600

The two controllers are

rather similar.

Both are water-cooled

and feature regenerative

braking capabilities. Both handle the conversion from DC to AC because this is an

integral part of controlling the vehicle’s acceleration. Both max out at 100 kW, perfect

for our application.

Figure 13: MES-DEA TIM-600 (photo from metricmind.com)

Siemens Simotion

Input voltage max 380 V

Input current max 282 A

Weight 17 kg (30.8 lbs)

Dimensions 47 cm x 20 cm x 18 cm (18.5” x 7.9” x 7.1”)

Total Volume 9,900 cubic cm (650 cubic inches)

35

MES-DEA TIM-600

Input voltage max 400 V

Input current max 325 A

Weight 10 kg (22 lbs)

Dimensions 33 cm x 25 cm x 12 cm (13” x 10” x 5”)

Total Volume 9,900 cubic cm (650 cubic inches)

The MES-DEA appears to be slightly better than the Siemens in terms of higher power

input, size, and weight. However, the difference is slight enough that the controller

should not be the determining factor in the decision between manufacturers.

Regenerative Braking

Regenerative braking has greatly benefited hybrid cars, increasing both their range and

efficiency. Regenerative braking requires an electrical power system, and so is

impossible to incorporate into a conventional internal combustion vehicle. With electric

and hydrogen cars, it is easy to implement.

Regenerative braking recaptures the kinetic energy of a vehicle when it brakes. A car

traveling at 30 mph has significant kinetic energy; it used a lot of fuel to get its mass

going that fast. When a normal car brakes, all that energy is transformed to heat in the

brakes and is essentially wasted. With regenerative braking, that energy is used to turn a

generator and charge up a battery, or in our case, a bank of ultracapacitors. The generator

is often the very same motor that powers the car – one advantage of electric motors is that

while putting electricity in turns the motor, turning the motor also sends electricity out.

Regenerative braking can therefore be incorporated into the system with little addition to

the vehicle’s weight.

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In practical terms, regenerative braking is handled by the motor controller. The brake

petal will be attached to the controller. When the driver wants to brake, he or she will

push down on the petal in the normal fashion. This will send a signal to the controller to

open up the connection to the ultracapacitors, which will effectively put a load on the

generator (the motor). Because the motor is connected to the wheels, it will be spinning

with the wheels. Adding a load (the ultracaps) will force the motor to generate electricity.

Because the energy comes form the kinetic energy of the vehicle, the motor will slow

down as it charges the ultracaps, slowing the wheels and thereby the car. The rate at

which the motor slows the vehicle will be determined by the controller and in turn by the

amount the driver pushes down on the brake petal. All this happens in real time, and

many drivers would not notice the difference between regenerative and conventional

braking.

For normal braking situations, regenerative braking is all that is necessary. However, it

would be wise to include regular friction brakes in case of an emergency. Also, long

downward hills would generate more electricity than the ultracapacitors could hold. After

the capacitors filled up, regenerative braking would no longer slow the car. Friction

brakes would be necessary to allow the driver to maintain control of his or her vehicle.

For that reason, in a hydrogen vehicle conventional brakes would also be connected to

the brake petal, albeit at a level where they would not engage until the petal was pressed

most of the way down. If a driver slammed on the brakes, both the regenerative and

conventional brakes would go on, giving the car maximum braking power. Otherwise

only regenerative braking would come into play, as long as the ultracapacitors are not

fully charged.

For more information the specific energy involved in regenerative braking, see the

section on Ultracapacitors. In summary, our car will contain enough ultracapacitors to

store 225,000 Joules of energy, which is the approximate amount that a car, given some

internal inefficiency, can gain from a 44 mph deceleration to zero. Ideally, for

regenerative braking to be most effective, the ultracaps should be able to store all the

power generated from any deceleration. However, having that quantity of ultracapacitors

37

is not feasible at this point in time. Regenerative braking can still be very effective,

especially in city driving, even if it can capture the energy from only a 44 mph speed

decrease.

Because regenerative braking reclaims energy, it can provide the car with an extra boost

of power during acceleration. Not only will the energy allow for the fuel cell to spend

less time running, and therefore consume hydrogen at a slower rate, but it can also be

used to augment the fuel cell and provide the motor with more power. If the driver “puts

the petal to the metal,” both the fuel cell and the ultracaps power the motor. Because the

motor tops out at 100 kW, this means that the total power provided by the fuel cell and

ultracaps should not exceed 100 kW. Therefore, instead of needing a 100 kW fuel cell to

completely take advantage of the motor, the car can now have only an 80 kW fuel cell

and 20 kW of ultracaps. Other combinations for further decreasing the fuel cell size are

possible – see the section on the Fuel Cells for more details.

Finally, regenerative braking will reduce pollution caused by ordinary brakes.

Surprisingly, brake pad dust is the second largest cause of pollution among some urban

highways. Regenerative braking will greatly decrease the rate at which standard brakes

are used, thereby decrease pollution from brake pad dust.

Intermediate Energy Storage

It is possible to run a hydrogen car directly off the fuel cell. The fuel cell would burn

hydrogen as needed to directly power the controller and motor. This solution has merit

because it is simpler and cheaper. However, for this application it is not the best solution.

Adding an intermediate energy storage system will have multiple benefits:

1. Allow for the addition of regenerative braking to the system, thereby increasing

efficiency

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2. Provide additional power to augment the fuel cells during acceleration

Regenerative braking has been of great benefit to hybrid gas-electric vehicles by storing

energy normally lost during braking to be reused during acceleration. This further

increases the efficiency and range of the vehicle. Regenerative braking can easily be

integrated into a hydrogen vehicle because the system is completely electrical. However,

regenerative braking requires intermediate energy storage to store the energy captured

during braking.

Having temporarily stored power will be useful during acceleration. The energy storage

devices can be charged by either regenerative braking or by the fuel cell when it is not

already running at peak power, such as when the vehicle is maintaining a constant speed.

This stored energy can then be added to the max output of the fuel cells to increase

acceleration. Because acceleration uses the most power, it determines the size of the fuel

cell. Adding intermediate energy storage devices allow the fuel cell to decrease in size

while maintaining the same potential rate of acceleration, thereby decreasing the weight

of the fuel cell. This will in turn decrease the weight of the vehicle, because the power

density of an intermediate storage device (if ultracapacitors are used, anyway) is higher

than that of a fuel cell.

Therefore, any fully developed hydrogen vehicle will have a form of temporary energy

storage.

Batteries or Ultracapacitors?

There are currently two forms of energy storage solutions that exist in the market today.

The first is the tried-and-true battery, which currently serves to capture energy from

regenerative braking in most hybrid vehicles. The second is a newer technology,

ultracapacitors, which have several benefits and drawbacks compared to batteries.

Ultracapacitors are a type of capacitor and so do not store energy in a chemical reaction

as batteries do. The major relevant difference between ultracapacitors and batteries has to

39

do with their energy storage capabilities. Batteries can hold ten times or more watt-hours

per kilograms than ultracapacitors, and can therefore store more energy. However,

ultracapacitors have a much higher power density, at around 10 times more watts per

kilograms than batteries. Also, ultracapacitors can charge and discharge much faster than

batteries, in the order of seconds, not hours. The have a much longer life, in excess of

500,000 cycles.

Figure 14: Two batteries suitable for electric vehicles. Image from Electro Automotive at http://electroauto.com/catalog/battery.shtml.

For a hydrogen car, the energy must be stored and

surrendered quickly. Braking from 60 mph down to

zero happens in seconds. Similarly, the car will

accelerate to cruising speed in less than a minute,

depending on the tendencies of the driver.

Ultracapacitors, with a higher power density, are

better suited to this. In an electric vehicle, which is

similar to a hydrogen car, large amounts of power

needs to be stored to maximize the vehicle’s range,

so batteries are used. In a hydrogen car, however,

range will depend only on amount of H2 stored. The

temporary energy storage devices need to hold little

relative energy but be able to move that energy

quickly. Ultracapacitors are better suited to this

application.

The application also involves completely cycling the energy storage device from empty

to full to empty. This would decrease the lifetime of batteries further, but have little

detrimental effect of ultracapacitors. Batteries in a hydrogen car would probably have to

be replaced at least once, while ultracapacitors would last the lifetime of the car. Finally,

the fact that ultracapacitors are lighter is no small benefit. Therefore, we have decided to

incorporate ultracapacitors instead of batteries into our vehicle design.

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Ultracapacitor Details

The decision regarding the amount of ultracapacitors is based primarily on regenerative

braking. We originally wanted to be able to capture all the energy theatrically generated

by a vehicle decelerating from 60 mph to 0 mph. This is dependant on the weight, and

because that is not finalized we used an estimate of 3500 lbs. It will hopefully be less.

The energy gathered from a deceleration to zero is as follows:

Kinetic Energy = ½ (mass) (velocity)2

3,500 lbs = 1,589 kg 60 mph = 26.817 m/s

½ (1589) (26.817)2 = 571,365 joules

A decent car can decelerate from 60 to 0 in around 7 seconds.

571,365 / 7 = 81,623 watts or 82 kW

These numbers represent the absolute maximum energy you could extract from a moving

car. This, as you can see, is quite a lot of energy. Ultracapacitors are not designed to store

this volume of energy. Batteries would fail to deliver the 82 kW rate of power in a

reasonable weight. Therefore, storing this amount of energy is not feasible. Even after the

consideration of inefficiencies due to friction and the electrical components, this number

is simply too large. An alternative solution is needed.

All things considered, a car does not go directly from 60 to 0 all that regularly. Often the

vehicle goes only from 30 to 0 when, say, the driver pulls off a town road and into his or

her driveway. Or perhaps the vehicle brakes from 45 on a country road to 0. In either

situation, far fewer ultracapacitors are needed. It should be reasonable to incorporate

enough ultracapacitors to be able to capture all the energy in many braking situations

where the speed change is not so great. For a 60 to 0 deceleration, the majority of the

energy will be still be regained. If that 60 to 0 deceleration does not occur all at once, it

41

may still be possible to capture all the energy. If, for instance, the vehicle brakes from 60

to 45 when it enters a developed area, the ultracapacitors can store all that power. The car

may than drive for a little while, draining the ultracaps, and thereby enabling them to

store the energy from any subsequent deceleration.

Analyzing the kinetic energy of a moving car at various velocities shows that a decrease

in speed corresponds with a decrease in energy as an inverse square (as you would expect

from the KE equation). The nature of the physics will enable the vehicle to be able to

handle all the energy from a deceleration of nearly 60 to 0 while having significantly

fewer ultracapacitors.

∆v to 0 (mph) ∆v (m/s) Mass (kg) Resultant max kinetic energy

30 13.4 1589 142,660 J

40 17.9 1589 254,566 J

45 20.1 1589 320,986 J

50 22.4 1589 398,648 J

60 26.8 1589 571,365 J

We would like to keep the total weight of the ultracaps below 50 lbs and the total volume

inside a cubic foot. Cost is also an issue, but the price of ultracapacitors has decreased in

recent years and would continue to do so if they were implemented in a mass-produced

vehicle. Cost, therefore, will only be considered in extreme cases (such as when buying

enough ultracaps to handle the 60-0 mph speed change).

Before the number of ultracapacitors is decided, inefficiency of the system must be taken

into account. The efficiency of charging the ultracapacitors via regenerative braking will

not exceed the net controller, motor, and drivetrain efficiency. This is:

Motor Efficiency * Drivetrain Efficiency * Controller Efficiency = Net Efficiency

90% * 90% * 90% = 73%

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Finally, it is important to take into account the other function of ultracapacitors besides

that of regenerative braking. The ultracapacitors are also used to increase vehicular

acceleration by augmenting the fuel cells. In this case, the more ultracaps, the better. The

motor and controller max out at 100 kW (see the sections on Motors and Controllers), so

the net power provided by both the fuel cells and the ultracaps should not exceed this

value. The motor will probably not be run at 100 kW for more than 10 seconds, the

approximate time it will take to go from 0 to 60 mph. While the fuel cells will have to do

most of the work during these 10 seconds, the ultracaps should be able to contribute. If

the ultracapacitors are going to have any reasonable impact, they should run at 20 kW or

more. Running the ultracaps at 20 kW for ten seconds will require them to have at least

200,000 joules of stored power.

Desired Ultracapacitor Characteristics:

Maximum Weight: 50 lbs (22.7 kg)

Maximum Volume: 1 cubic foot (28.3 liters)

Minimum Stored Power: 200,000 J

Power Rate: 20 kW

Example Solution: Maxwell Ultracapacitors

There are several manufacturers of ultracapacitors, and

ideally one would go with the cheapest solution. Any

type of ultracapacitors that meet the specs will do. For

the purposes of this booklet, we have chosen to go with

Maxwell’s BCAP0008 ultracapacitors. The analysis,

using specific ultracapacitors, will give us good

estimates in terms of weight, cost and viability. If we

were to actually build the car, we would go with

Figure 15: Maxwell BCAP0008 ultracapacitor (from http://www.maxwell.com)

43

whatever was available.

The BCAP0008 Ultracapacitors last several hundred thousand cycles and are shock and

vibration proof.

A single BCAP0008 ultracapacitor has the following specs:

Capacitance: 1,800 Farads

Voltage: 2.5 V

Max Current: 450 A

Stored Energy: 5625 Joules

Weight: 400 g

Volume: .3 liters

Using the BCAP0008 specs, around 55 ultracaps would total 50 lbs. A volume of 1 cubic

foot would hold up to 90 capacitors.

The minimum number required to hold 200,000 joules is

200,000 J / 5625 J = 36 ultracaps

The capacitors can handle up to 450 A, so running at 20 kW requires

20 kW / 450 A = 44 V

44 V / 2.5 V per cap = 18 ultracaps

Therefore, we want a number of ultracaps somewhere between 36 and 55. To keep cost,

weight and volume down, the number of caps should be closer to 36. We have decided to

go with 40.

Having determined this, a few quick calculations will yield exact data:

44

40 * 5256 J = 225,000 J total storage

225,000 J / 73% efficiency = 308,220 J

√ [308,220 / (½ * 1589 kg)] = 19.7 m/s = 44 mph

Therefore, the ultracapacitors can handle all the power generated from a 44 mph

deceleration. Energy from a single deceleration of any more than that will be wasted as

heat.

To keep the amperage down, the capacitors would be connected in series.

40 * 2.5 V = 100 V total

100 V * 450 A = 45 kW max

225,000 J / 45 kW = 5 seconds

Therefore, if the car brakes from 44 mph down to 0 in less than 5 seconds, the

ultracapacitors will not be able to absorb all the energy. This is perfectly reasonably as it

is unlikely that a driver will slow the car that rapidly during normal driving. Additionally,

in the case where a driver needs to stop extremely quickly and stomps on the brake petal,

both conventional and regenerative brakes will come into play (see the section on

Regenerative Braking). During acceleration, it is likely that the caps would be run at only

20 kW, thus reducing the amperage and the time to drain them.

225,000 / 20 kW = 11.25 seconds until empty

A DC-DC converter will most likely be required at some point to step the 100V

capacitors up to the higher voltage that the motor controller requires.

And for physical characteristics:

40 * 400 g = 16 kg

45

40 * .3 L = 12 L

It should be noted that while the volume of each ultracapacitor is .3 L, they are

cylindrical, so it would be impossible to fit them in only a 12 liter space. However,

because each ultracap is a separate device, it should be feasible to pack them around other

components, thereby maximizing space usage.

Final Results: BCAP0008 Quantity: 40

Total Storage: 225,000 Joules

Net Voltage: 100 V

Total Power Rate: 45 kW

Total Weight: 16 kg (35 lbs)

Minimum Volume: 12 L (.4 cubic feet)

Platform Vehicle and Modifications

As the primary goal of our project and of fuel cell vehicles is to limit the use of fuel and

to increase the efficiency of automobiles it would be ideal to build the vehicle on an

extremely lightweight and aerodynamic chassis. This in mind the most effective chassis

for our project would be a chassis and body constructed of aluminum or carbon fiber and

having an aerodynamic drag coefficient of less than .30. As weight is a very important

factor in the construction of an efficient high-performance vehicle, a smaller chassis and

body is more desirable. A two-door sport car type body is the most attractive solution to

the design. However, it may be difficult to fit the necessary components into a small car.

For this reason a rear-wheel type drive train may be beneficial as it allows the drive train

components to be spread down the length of the car, providing more room under the hood

and in the trunk of the car. While a custom-designed and built body and chassis would be

most desirable, it is at this point out of reach of our project. A custom-built body and

46

chassis would be very expensive and require an extremely high amount of work and time.

Using a custom frame and body, we would also be forced to incorporate all other

components of standard automobiles into our design (steering, braking, suspension, and

electronic systems). Additionally, it would be exceedingly difficult to obtain the proper

authorization to make the car street-legal. For these reasons we will simply redesign an

existing vehicle to meet the requirements of the fuel cell systems. The following is a list

of traits desired for the platform vehicle:

• Low Weight

• Low Drag Design

• Large Area Under Hood

• Large Storage Area

• Even Weight Distribution

• Well Designed Factory Steering, Suspension, and Braking Systems

• Two Wheel Drive Type – Rear

• Easily Redesigned / Removed Drive Train.

There are several cars that meet with our requirements and are not difficult to obtain. Of

these, a second generation Mazda RX-7 meets almost every desired trait while offering

outstanding performance with respect to steering, suspension, and braking. These cars

also offer low weight, low drag, plenty of room under the hood and in the back of the car,

and a nearly perfect front to back weight distribution. The low weight and drag as well as

the higher performance factory components are especially important to our project as we

wish to promote the value of fuel cell vehicles not only as a clean and efficient alternative

to combustion engine vehicles, but also as vehicles that can rival combustion powered

cars in performance on the street. As mentioned above weight is one of the most critical

aspects of building an efficient high performing vehicle. The RX-7 weighs only 2,800

lbs from the factory and many of the heavier components of the car, such as the engine,

transmission, and gas tank, can be removed as they will be replaced by the fuel cell

system. (See the Performance Analysis section for a chart detailing the weights of

components for the fuel cell system.) Despite the fact that many heavy components can

47

be removed the final weight of the fuel cell vehicle will likely be larger than the weight

of the platform vehicle as the fuel cell stack and fuel tanks can be quite heavy.

Figure 16: A Mazda RX-7. Image from http://www.mazda.co.jp/history/rx7/Java/Catarog/img/85 2.jpg.

In addition to removing many gasoline components several other modifications must be

made to the platform vehicle. As a general rule we have found that it is best to use

existing systems to the largest extent possible and to modify the factory systems only

when required. Many of the components being added as parts of the fuel cell system will

require redesigned mounts. The engine in particular will need to have quite stable mounts

and these must be fitted exactly to the motor. Such strong mounts are required as a large

amount of torque will be exerted on the engine during acceleration. As these mounts must

be extremely stable it seems the best solution is to simply design a sub frame that would

attach to the existing engine mounts and to the electric motor. This approach is much

simpler than welding a completely separate mounting system to the frame and should be

much less expensive.

The mounting and powering of the vehicle’s subsystem compressors and pumps must

also be modified. In modern vehicles the pumps and compressors for systems such as the

cooling, power steering, air conditioning, power braking, and vacuum systems are all

powered by a belt-pulley system connected to the crank pulley located at the front of the

48

engine. As the electric motors that we are considering in our design do not have both

front and rear drive shafts this technique is not possible. To power the pumps and

compressors of the accessory systems the crank pulley of a combustion engine must be

replaced with a small electric motor that can power the subsystems through the original

technique of belts and pulleys. This requires a very small amount of modification to

these systems thus providing for a cost and time-effective solution. However, several

other considerations must be made. As these components mount to the engine block in

the original design, new mounts must be made. If the accessories requiring new mounts

are light enough it would be possible, and most logical, to construct a mounting system

that would secure the pumps and compressors to the side of the engine compartment. If,

however, the components are heavier and the engine compartment walls do not provide

adequate strength a system for mounting the accessories to either the frame, engine

mounts or suspension crossbeam should be implemented. In addition to considering new

engine mounts the matter of engine vacuum must also be taken into account. In most

modern cars numerous systems are powered or controlled by engine vacuum. As electric

motors do not create this vacuum, a small electric air pump must be installed as a

replacement. This pump may need a basic controller in order to properly mimic the

pressure created by a combustion engine.

A final modification that should be made to the vehicle is the replacement of the tires.

While this may seem rather insignificant, a set of harder, high-pressure tires can increase

the efficiency and performance of the vehicle quite appreciably by reducing the amount

of deformation of the tires during driving. As this deformation creates heat and requires

mechanical energy itself it is clearly inefficiency and a waste of energy. This problem

can be minimized with addition of the aforementioned tires.

Also of importance when discussing the platform vehicle is the location of the fuel cell

components. Ideally all components would be located in close proximity to each other.

Extremely high amounts of electric power, as well as pressurized hydrogen gas, must be

transported between fuel cell components, which can be rather difficult. Unfortunately,

there is not enough room either under the hood or in the back of the car to accommodate

49

all of the components. For this reason the fuel cell stack as well as the hydrogen tanks

will be located in the back of the car, while the motor, controllers, ultracapacitors, and

gearbox will be located under the hood. This design minimizes the distance the high-

power electric cables and hydrogen lines will have to travel. The hydrogen lines will be

limited to the distance from the tanks to the fuel cells; the tanks and fuel cells will be in

close proximity to each other, both units being located in the back of the car. This

location is also desirable for the hydrogen containing components, as it does not require

the hydrogen lines to run under the passenger compartment, thus avoiding serious safety

issues due to a hydrogen leak. Unfortunately, high power electric lines must be run the

length of the car to supply power from the fuel cells to the motor and ultracapacitors.

However, the majority of the lines will be running between components in the engine

compartment such as the motor, controller, and ultracapacitors. These lines, while

numerous, will be quite short, thusly reducing the amount of energy lost to the resistance

of the wires. The wires that will be installed to carry the electricity from the fuel cells to

the motor must be quite heavy in gauge and very low in resistance. It would be best to

have braided cables, and an effort must be made to run the wires along the shortest path

possible from the cells to the motor.

Cooling

Many elements of a hydrogen car require cooling. The motor, controller and fuel cells

will all need water cooling. The water cooling system can probably be integrated together

so that only one circulation method is needed. Additionally, these systems will be used to

heat the cabin when the driver requires it. The water can also be circulated through the

radiator in the same manner as in a conventional car, venting the heat out into the air.

Because both the motor and controller are far more efficient than the internal combustion

engine in a regular vehicle, they do not need such a large radiator and cooling system.

This will decrease the cost and complicity of a hydrogen vehicle as compared to a

50

conventional car. However, when converting a car to run off hydrogen, it is simply

easiest to use the radiator and cooling system already there.

It is important to ensure the motor in particular receives adequate cooling. As the wires in

the circuitry of the motor heat up, they become more resistant. A higher resistance

decreases the current flowing to motor (as given by the equation V = I * R), and so the

motor becomes less powerful. Besides preventing the components from burning out,

system cooling assures you will have maximum power.

The specifics of the cooling system will be determined primarily by the final location of

each component. As it is impossible to say at this point in time where the fuel cell will be

located in the chassis, it is impossible to describe exactly how it will be cooled. If it is

under the hood, cooling lines can simply be run over to the radiator. If it is under the

vehicle, however, a different solution may be needed depending on how the cooling

hoses can be run. Additionally, the fuel cell may (in the case of Ballard’s) have a cooling

system already built in, and until the details on that system is fully determined, it is

impossible to say if and how that system would tie into the rest of the car.

Performance Analysis

Now that the various components have been determined, it is possible to perform some

rough estimates on the vehicle’s performance.

Before the vehicle’s acceleration can be estimated, the total weight of the car must be

found. It is impossible at this stage to provide a perfect estimate of the vehicle’s weight,

but a likely range can be determined.

51

a conservative estimate: an optimistic estimate:

mass kg lbs kg lbs

h2 tank 110 242 110 242

fuel cell stack 220 484 96 211.2

motor 61 134.2 61 134.2

controller 20 44 20 44

ultracapacitors 16 35.2 16 35.2

cooling 20 44 20 44

body and frame 1000 2200 900 1980

transmission 90 198 20 44

hydrogen 5.4 11.88 5.4 11.88

misc. components 50 110 100 220

total vehicular weight 1592.4 3503.28 1348.4 2966.48

There are two different ways to determine the vehicle’s potential acceleration. First, we

ran a few quick calculations based on the simple laws of physics and kinetic energy. It is

possible to calculate how long it takes a 3500 lbs mass to accelerate to various speeds

when 100 kW of power (from the motor) is poured into it.

weight mass v v KE =

1/2 mv^2

max power of

motor

theoretical time until velocity is

reached

lbs kg mph m/s joules kilojoules kW seconds

3500 1588 30 13.4 142570.64 142.6 100 1.4

3500 1588 60 26.8 570282.56 570.3 100 5.7

3500 1588 100 44.7 1586483.46 1586.5 100 15.9

This estimation seems to indicate that our car should 60 mph in under 6 seconds, which

would be extremely good. However, this estimation is a poor one because simply running

a motor at 100 kW does not add 100 kW of mechanical energy to the car. Power is

52

wasted as heat because the motor simply can not accelerate the car at the maximum rate

with no losses.

A better way to estimate vehicular performance is through the motor’s torque (as torque

is the key determinant of acceleration, not horsepower). We determined what torque is

needed to accelerate the car from 0 to 60 mph in 10 seconds. The calculation can be done

all at once (i.e. from 0 mph to 60 mph), but this yields a torque requirement higher than is

really necessary, because it assumes a constant acceleration from 0 all the way to 60. No

car is actually like this; the time in which it reaches 30 mph is significantly less than half

the time it takes to reach 60 mph. Consequently, the best way to make this torque

calculation is to use many short steps of speed change (we chose 5 mph steps) to reach

60. Each step takes a different amount of time, as a vehicle goes from 0 to 5 in far less

time than it does from 55 to 60. We first determined the time that a 100 kW motor should

need to accelerate the car each 5 mph step, and then calculated how much torque that

would require. When considering weight, we erred on the heavy side, using an estimate

of 3500 lbs. Note that these calculations do not yet provide an indication of how well the

car will perform; they simply indicate the torque we need to aim for.

53

54

Using these rough estimates of the torque the motor needs to output, we chose our two

motor options. Now, working backwards through the process above, we can find how fast

each specific motor actually will accelerate the car.

The Siemens motor is calculated on the following page.

The Siemens can reach 60 mph in 12 seconds, a little below our hopes, but still perfectly

reasonable.

55

56

Unfortunately, we were unable to acquire torque/rpm specs for the MES-DEA 200-250

motor. However, we did find a torque curve for a 21 kW version of the motor, and were

able to calculate performance based on it. The next page details the calculations.

The MES 200-175 can reach 60 mph in around 18 seconds. Our motor of choice, the

MES 200-250, is approximately 150% as powerful. A direct proportion of the motors’

two powers (although this is not good science, it is the only method of approximation we

have) indicates that the MES 200-250 should reach 60 mph in 12 seconds. This is a little

longer than we had hoped, but considering that our estimation technique is poor we

should not throw out the motor yet. Also important to consider is that the MES motor is

slightly more powerful than the Siemens, which reached 60 mph in 12 seconds, and so

the MES should in fact perform better than this.

57

58

Some other interesting calculations include air drag. Based on a Mazda RX7 body (see

the Platform Vehicle and Modifications section), our car will have an air resistance at

various speeds as described by the following table: AIR DRAG P=ACV^3D/2

Vehicle frontal area m^2

Coefficient of drag

speed mph m/s

air density kg/m^3 P= (kW lost)

1.784 0.31 10 4.47 1.18 29.14279 0.0

1.784 0.31 20 8.94 1.18 233.1423 0.2

1.784 0.31 30 13.41 1.18 786.8553 0.8

1.784 0.31 40 17.88 1.18 1865.139 1.9

1.784 0.31 50 22.35 1.18 3642.849 3.6

1.784 0.31 60 26.82 1.18 6294.843 6.3

1.784 0.31 70 31.29 1.18 9995.977 10.0

1.784 0.31 80 35.76 1.18 14921.11 14.9

1.784 0.31 90 40.23 1.18 21245.09 21.2

1.784 0.31 100 44.7 1.18 29142.79 29.1

1.784 0.31 110 49.17 1.18 38789.05 38.8

1.784 0.31 120 53.64 1.18 50358.74 50.4

1.784 0.31 130 58.11 1.18 64026.71 64.0

1.784 0.31 140 62.58 1.18 79967.82 80.0

1.784 0.31 150 67.05 1.18 98356.92 98.4

kW of Air Resistance

0.0

20.0

40.0

60.0

80.0

100.0

120.0

4.47 8.94 13.41 17.88 22.35 26.82 31.29 35.76 40.23 44.7 49.17 53.64 58.11 62.58 67.05

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Speed (m/s and mph)

59

Until the vehicle gets going above 60, the air resistance is very small. This is due in part

to our choice in vehicular chassis; the RX-7’s coefficient of drag (how aerodynamically

streamlined it is) is a low .31 and the car’s frontal area is also small. One of the

interesting conclusions from this graph concerns top speed – with an 80 kW fuel cell

running at max, the car would top out at a respectable 140 mph before air drag became

too great. Driving at this speed, however, would quickly burn through the vehicle’s fuel

supply.

Costs

This section is here for curiosity’s sake only. Most of the prices listed here represent the

cost of components bought off the shelf. Other components do not have “list” prices, and

we could only estimate their cost at this time. In any case, these components are not

mass-produced in nearly the volume they would be if hydrogen cars were built to replace

gasoline vehicles. Their prices are several multiples higher than they could be given

large-scale production. These estimates are not meant to scare people away from the

technology; they merely represent how significant the economy of scale can be. It is

impossible to say at this point how a fully developed hydrogen vehicle would compare in

cost to today’s cars, but the major car companies would not be pursuing the technology if

it could not be made cost effective.

The chart on the following page describes the cost of each component.

60

Category Component cost $ Fuel Cell estimated at $3,000 per kW output 80 kW fuel cell $240,000Hydrogen Tanks these prices are pure speculation DyneCell W 150 $2,000 DyneCell V 74 (x2) $2,000 gas lines $200AC Motor and Controller (Siemens) quotes from metricmind.com 1PV5135 WS14 $5,581 Simovert 6SV-1 AC inverter $3,996AC Motor and Controller (MES-DEA) quotes from metricmind.com MES 200-250 $3,820 MES DEA TIM 600 ac inverter $4,694Ultracapacitors price is outdated; should be cheaper Maxwell BCAP0008 (x40) $5,480Platform Vehicle these prices could vary a lot, and are relevant only to our specific design Mazda RX-7 (used) $1,000 High Pressure tires $500 Motor Mounts $500 Modification to the suspension $1,000Gear Box supplied with MES 200-250 $1,194Misc Electronics - needed to replace conventional systems previously powered by gasoline engine Vacuum pump, water pump $500- other, such as wiring other $500Other more speculation cooling system $1,000 drivetrain adaptors $500 misc frame modifications $1,000 vehicle total $265,888(assumes MES-DEA motor system is used)

It is noteworthy that the vast majority of this ridiculous price tag comes from the fuel

cell; as discussed in the Fuel Cell section, it is currently made from rare metals. Again,

the future will hopefully be brighter and provide cheaper fuel cells.

61

Appendix 1: Sources of Hydrogen

To be truly environmentally friendly, a hydrogen car must run off hydrogen produced in

ways that do not pollute. Unfortunately, most of the cheap and common ways of

producing hydrogen do lead to pollution. Hydrogen is easily gathered from fossil fuels.

Fossil fuels are hydrocarbons composed of hydrogen and carbon. Most hydrogen today is

produced from breaking down fossil fuels into their components and collecting the

hydrogen. The remaining carbon is dumped into the atmosphere where it combines with

oxygen to create carbon dioxide, the infamous greenhouse gas. Because fossil fuels are

currently plentiful, this method for generating hydrogen is the cheapest.

However, this strategy undermines the principle behind hydrogen vehicles – the idea that

we can avoid harming the environment while we go about our daily business. This

technique also will not eliminate all our energy problems, because we will still need large

quantities of fossil fuels which may not be available in sufficient amounts in this country.

For example, 48% of hydrogen produced today comes from natural gas, and 30% from

oil. Because fossil fuels are not infinite, using them to generate hydrogen can only be a

temporary solution.

There is a cleaner way to create hydrogen. Through the process of electrolysis, water is

broken down into its components, hydrogen and oxygen. The hydrogen can be stored for

use in vehicles and the oxygen can be released into the atmosphere. The atmosphere is

already approximately 21% oxygen, so the additional amount will not be foreign. There

is no need to worry about changing the environment by increasing oxygen levels and

damaging plant life. A hydrogen vehicle with a running fuel cell will draw oxygen back

out of the air in the same quantity as was added during electrolysis. Using electrolysis of

water to generate hydrogen creates a nearly perfect balance.

62

Figure 17: A balance is achieved. All water destroyed to create hydrogen and oxygen for the car is recreated in the fuel cell as the vehicle is driven. There are no environmental changes in the levels of any compounds.

Unfortunately, electrolysis of water is expensive. A lot of electricity is needed to break

down water into its components. Essentially, this process is the reverse of running a fuel

cell, so the high potential output of fuel cells per quantity of hydrogen now means that a

large amount of energy is needed to break down water. Because electrolysis requires

electricity, and most electricity if made in fossil fuel power plants, this strategy, if

implemented today, does not reach a perfect “zero-emission” goal. The only way to have

a completely pollution-free supply chain is to generate electricity for electrolysis from

renewable sources. Perhaps in the future large arrays of solar panels will work to break

down water to extract the necessary hydrogen. Harnessing wind and water power is also

something we should be working towards today, regardless of the future of hydrogen

vehicles. In the far future perhaps hydrogen fusion will become a viable way of

63

generating electricity, and our energy needs will be taken care of. There will be plenty of

electricity to generate hydrogen cleanly and cheaply.

Iceland is the perfect example of how hydrogen can be generated cleanly. The nation has

decided to move towards a hydrogen-powered economy. Iceland has the natural

advantage (in this case) of being located on the boundary of two tectonic plates.

Consequently, there is a significant amount of geothermal activity that can be used to

generate cheap electricity. By capping off geysers and using superheated water provided

by the earth, Iceland can produce large amounts of electricity without harming the

environment. This can be used in turn to produce hydrogen via electrolysis, effectively

making hydrogen vehicles one-hundred percent green.

Regardless of which method is used to generate hydrogen, it is estimated the vehicle fuel

costs will either match or fall below that of current prices for gasoline vehicles. The

possible higher cost per kg of hydrogen over gallon of gasoline is offset by the fact that

hydrogen vehicles are far more efficient. A kilogram of hydrogen, although holding

nearly the same amount of energy as a gallon of gasoline, can propel a vehicle far further.

Hydrogen cars will be cheaper to drive.

Appendix 2: How Safe is Hydrogen?

Hydrogen is a flammable gas, so safety must be a concern. However, hydrogen’s

flammability must not prohibit its use; after all, gasoline is also highly combustible.

Hydrogen nevertheless can be considered slightly more dangerous because unlike carbon-

based fuels, it will combust in the presence of oxygen with little or no cause – no spark is

necessary. However, several properties also make hydrogen safer. In a vehicle, hydrogen

gas is by necessity stored in a very strong tank. A weaker tank could not handle the

pressures (in excess of 5000 psi) that the hydrogen is stored at. In a collision, it is very

unlikely that the tanks will rupture, especially when they are designed specifically for

64

automotive applications. A gasoline tank, on the other hand, can break open easily. It is

also very unlikely that the hydrogen would cause an explosion, even given a leak in the

tanks, because only a very rich and concentrated mixture is unstable. As hydrogen is

literally the lightest element in the universe, it will quickly rise and disperse into the

atmosphere. The chance that conditions for explosion would be met is extremely slim.

Additionally, in

the event that

the hydrogen

tank or the

hydrogen fuel

lines broke, the

worst that the

hydrogen might

do is ignite. In

this situation, it

is unlikely that

anyone would

be burned because a hydrogen flame radiates little heat. The result would be somewhat

like a Bunsen burner – a small flame where the hydrogen met the atmosphere. There

would be no risk of the flame following the hydrogen down into a tank or along a fuel

line, because like a Bunsen burner, hydrogen needs oxygen to burn. Inside the tanks there

is no oxygen, and therefore there can be no fire. Finally, unlike gasoline fires, hydrogen

combustion does not produce any smoke (the result of hydrogen combustion is water).

Smoke inhalation is the number one cause of death in gasoline fires.

Figure 18: A demonstration of a hydrogen and a gasoline fire in a vehicle. The hydrogen fire burns upward, and is unlikely to ignite other parts of the car. The gasoline fire, on the other hand, spreads around the entire vehicle and is an obvious danger to anyone in it. This simulation was performed by DaimlerChrysler and the image comes from Scientific American Frontiers at PBS.org.

One event many skeptics point to is the Hindenburg disaster, where a large zeppelin

caught fire and resulted in many fatalities. Because the Hindenburg was filled with

hydrogen, some people believe that the hydrogen was responsible for the fire. It has been

demonstrated that the fire was actually a result of flammable cloth surrounding the

65

hydrogen and electricity in the atmosphere. When the Hindenburg burned, the hydrogen

that did ignite burned above the passengers. The 65% of the people who survived were

able to avoid falling out of the gondola or getting burned by the flammable cloth or diesel

fuel. They rode the flaming gondola down to earth. The accident could have happened

just as easily if the Hindenburg had been filled with non-reactive helium.

Finally, the fuel used in hydrogen vehicles bears little resemblance to that of hydrogen

bombs – in the case of a hydrogen bomb an isotope of hydrogen (usually deuterium) is

used. Even so, the only way to create fusion in H-bombs is through the use of several

coordinated uranium A-bombs, forcing the deuterium to fuse. There is absolutely no way

this is possible in a car.

Hydrogen cars should match or surpass current gasoline vehicles with regard to safety.

Appendix 3: References

Hydrogen Storage

Brooks, Alec. “Fuel Cell Disruptor”. 7 Dec. 2002. EV World. May 2004

<http://www.evworld.com/view.cfm?section=article&archive=1&storyid=464>.

Dynetek Industries Ltd. June 2004 <http://www.dynetek.com/>.

Fuel Cells

Ballard Power Systems. May 2004 <http://www.ballard.com/>.

Fuel Cells – Green Power. Thomas, Sharon and Marcia Zalbowitz. Los Alamos National

Laboratory. May 2004 <http://education.lanl.gov/resources/fuelcells/>.

“The Online Fuel Cell Information Resource.” Fuel Cells 2000. June 2004

<http://fuelcells.org/>.

FuelCellStore.com. 2004. June 2004 <http://www.fuelcellstore.com/>.

66

Motors and Controllers

Metric Mind Engineering. 2004. May 2004 <http://metricmind.com/>.

"Direct Current Traction Motor Systems.” Railway Technical Web Pages. Trainweb.org.

11 Dec 2000. June 2004 <http://trainweb.org/railwaytechnical/tract-01.html>.

“AC Induction motor drive.” MES DEA. June 2004 <http://www.know-it-web.de/cebi-

internet/ProductVariantCar/32>.

“Induction motors.” MES DEA. June 2004 <http://www.know-it-web.de/cebi-

internet/ProductVariantCar/25>.

“Vehicle Systems.” Solectria. 2004. June 2004

<http://www.solectria.com/products/vsystems.html>.

“AC-150 EV Power System.” AC Propulsion. 2001. June 2004

<http://www.acpropulsion.com/Products/AC_150.htm>.

“NetGain Motors.” NetGain Technologies, LLC. June 2004 <http://www.go-

ev.com/motors.html>.

“D.C. Motors.” Advanced DC Motors Inc. June 2004

<http://www.adcmotors.com/prod01.htm>.

Ultracapacitors

“BCAP0008 Ultracapacitor Product Information.” Maxwell Technologies. June 2004

<http://maxwell.com/ultracapacitors/products/BCAP0008.html>.

“Cell Balancing in Low Duty Cycle Applications.” Maxwell Technologies. June 2004

<http://maxwell.com/ultracapacitors/support/app_notes/cell_balancing.html>.

Misc.

Lovins, Amory B. “Twenty Hydrogen Myths.” Rocky Mountain Institute. 2 Sept. 2003.

29 May 2004 <http://www.rmi.org/images/other/E-20HydrogenMyths.pdf>.

“Honda FCX.” Honda Corporate. May 2004 <http://hondacorporate.com/?onload=fcx>.

Plugitin.co.uk - Tomorrow’s Transport Today. June 2004 <http://www.plugitin.co.uk/>.

Electro Automotive. 2004. June 2004 <http://www.electroauto.com/>.

Cloud Electric Vehicles. June 2004 <http://www.cloudelectric.com/>.

EV Parts. 2002. June 2004 <http://www.evparts.com/>.

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“Jerry’s Electric Car Conversion.” 2004. June 2004 <http://jerryrig.com/convert/>.

“Fuel Cell Grade Hydrogen.” Praxiar Technology, Inc. 2004. June 2004

<http://praxair.com/praxair.nsf/AllContent/B2973104A60BF94685256CE3007B

BAEF?OpenDocument&Menu=&ThemeId=339999&View=LeftNavMenu&Expa

nd=>.

“HEVA Manual – Appendix A: Energy Balances.” Power and Propulsion Office, NASA

Glenn Research Center. 03 May 2003. June 2004 <http://space-

power.grc.nasa.gov/ppo/projects/heva/appx_a.html>.

Mangini, Mike. Personal Interview. Sept 2003 – June 2004.

Glidden, Steve. Personal Interview. Sept 2003 – June 2004.

“Future Car.” Scientific American Frontiers. PBS. WCNY, Syracuse. 19 May 2004.

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