Bruce Lin - Conceptual Design and Modeling of a Fuel Cell Scooter for Urban Asia

CONCEPTUAL DESIGN AND MODELING OF
A FUEL CELL SCOOTER FOR URBAN ASIA
by
Bruce Lin

Princeton University
School of Engineering and Applied Sciences
Department of Mechanical and Aerospace Engineering

Submitted in partial fulfillment of the requirements for the degree
of Master of Science in Engineering from Princeton University, 1999

Prepared by:

(Author’s signature)

Approved by:

Professor Robert H. Socolow
Thesis Advisor

Professor Enoch Durbin
Thesis Reader

November, 1999

© Copyright by Bruce Lin, 1999. All rights reserved

abstract
Air pollution is of serious concern in many Asian countries, especially in densely-populated cities
with many highly-polluting two-stroke engine vehicles.The present value of health effects have
been estimated at hundreds of dollars or more, over each vehicle’s lifetime, for a reasonably
wealthy country like Taiwan. Four-stroke engines and electric battery-powered scooters are often
proposed as alternatives, but a fuel cell scooter would be superior to both by offering both zero
tailpipe emissions and combustion-scooter class range (200 km).

Unlike 50 kW automobile-sized fuel cell stacks, the vehicular 5 kW fuel cell needed here has not
received much attention. This niche is examined here with a conceptual design and consideration of
the issues of water, heat, and gas management. The application is extremely sensitive to size,
weight, and cost, so a proton exchange membrane fuel cell using hydrogen stored in a metal
hydride is best. Hydrides also act as sinks for waste heat due to the endothermic hydrogen
desorption process. Pressurized operation is found to be ineffective due to high parasitic power
demands and low efficiencies at the low powers involved.

A computer simulation is developed to examine overall vehicle design. Vehicle characteristics
(weight, drag, rolling resistance), fuel cell polarization curves, and a Taiwanese urban driving
cycle are specified as inputs. Transient power requirements reach 5.9 kW due to the rapid
accelerations, suggesting a large fuel cell. However, average power is only 600 W: a hybrid vehicle
with a small fuel cell and peaking batteries could also handle the load. Results show that hybrid
vehicles do not significantly improve mileage, but are certain to precede pure fuel cell scooters
while fuel cells are still more expensive than peaking batteries.

i

System size is approximately the same as current electric scooters, at 43 L and 61 kg for the fuel
cell, hydrogen storage, and electric motor / controller. Manufacturing costs of fuel cell scooters are
expected to decrease to under $1,300 in the long term, with per-km fuel costs half of those for
gasoline scooters. Hybrid zinc-air scooters offer similar performance at slightly lower vehicle
price, but the fuel infrastructure costs may be prohibitive.

ii

acknowledgments
With periods of hard acceleration, rapid decelerations, and occasional stalls in the course of writing
this thesis, sometimes I felt that I was on the Taipei Motorcycle Driving Cycle myself. Thanks to
everyone who had a part in this effort.

Thanks to my advisors Robert Socolow, Bob Williams, and Joan Ogden, and my thesis reader
Enoch Durbin.

Thanks to the many people from various research groups, companies, and academic institutions
who helped with guidance, hard data, and advice.

Thanks also to my family and friends and colleagues who supported me in the past twelve months,
and for many, much longer than that.

Support for this research came from the Center for Energy and Environmental Studies, the
Mechanical and Aerospace Engineering Department (including a Daniel and Florence Guggenheim
Fellowship and a Sayre Prize), the United States Department of Energy, and the Energy
Foundation.

This thesis carries 3055-T in the records of the Department of Mechanical and Aerospace
Engineering.

iii

table of contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Table of contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
List of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
List of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Transportation Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.1 Why Taiwan? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.2 Taiwan vehicle fleet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.1.3 Taiwan Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2 Air pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.2.1 The internal combustion engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.2.1.1 The four-stroke spark-ignition cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.2.1.2 The two-stroke spark-ignition cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.2.1.3 Advantages and disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
1.2.2 Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.2.3 Vehicle emissions standards and the reality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.2.4 Air pollution sources in Taiwan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1.2.5 Cleaner combustion technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
1.2.5.1 Exhaust gas recirculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
1.2.5.2 Superchargers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
1.2.5.3 Fuel injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
1.2.5.4 Catalysis of exhaust gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1.2.5.5 Replacement by four-stroke engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

iv

1.2.5.6 Relative costs and benefits of various technologies

. . . . . . . . . . . . . . . . . . . . . 34

1.2.6 Assessing the damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.2.6.1 Reduction estimate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
1.2.6.2 Externality damage estimate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1.2.7 Government Policy Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
1.2.7.1 Taiwan policy history: tighter emissions standards . . . . . . . . . . . . . . . . . . . . . . 40
1.2.7.2 Later years: inspection and maintenance . --">