Investigation of fuel cell technology for long-haul

trucks

SUMMARY

Cezary Misiopecki

______________________________________________________

The Master Thesis was supported by a grant from Iceland, Liechtenstein and Norway through the EEA

Financial Mechanism - Project PL0460.

Investigation of fuel cell technology for long-haul

trucks

Cezary Misiopecki

A 30 ECTS credit units Master´s thesis

Supervisors

Prof. Aleksandar Subic

Prof. John Andrews

A Master´s thesis done at RES | The School for Renewable Energy Science

in affiliation with University of Iceland, University of Akureyri &

SAMME, RMIT University

The Master Thesis was supported by a grant from Iceland, Liechtenstein and Norway through the EEA Financial Mechanism - Project PL0460.

Akureyri, February 2011

Introduction

Air pollution is currently considered to be one of the most important problems of 20th

and 21st

centuries. Major pollutants produced in the process of human activities are: carbon dioxide, carbon

monoxide, nitrogen oxides, sulphur oxides and particles. Their production is attributed to the usage of

fossil fuels. According to some surveys (CDIAC 2008) the carbon dioxide concentration increased from

325 ppm to 380 ppm between 1958 and 2008 and it is most likely to increase in the future. This could

implicate rapid global climate changes with drastic consequences for humanity.

Moreover, reserves of fossil fuels are limited and future shortage of oil is unavoidable. Because of

depleted resources and constantly growing consumption of fossils we can expect raises in oil prices.

Another disadvantage of the wide usage of convectional liquid hydrocarbons is that the world depends

on countries which have oil deposits. For all these reasons alternative energy sources and carriers are

subjects of growing interest and development.

Almost 95% of the transportation sector uses liquid hydrocarbons made from fossils as primary fuel. This

sector is responsible for 21% of the CO2 emission in the European Union (Eurostat 2004) and for 21% of

the greenhouse gas emissions in Australia (Tasman 2004).On one hand it is possible to reduce the

emissions of SOx, NOx and particles by special systems assembled on vehicles but on the other hand it is

extremely difficult because of the scale and complexity of implementing such sophisticated systems in

order to reduce the CO2 emission to zero.

Figure 1 - CO2 emissions from road transportation in EU and Australia

Many ways of improving the quality of exhaust have been invented and tested, however most of them

lower the overall system efficiency of a powertrain (IEA 2009). Since the oil shortage seems to be

inevitable and chances to improve the overall system efficiency and to lower the gas emission seem to

be weak engineers have started their search for new solutions.

Using hydrogen as an energy carrier is considered to be one of the most feasible and suitable ways of

transportation. Instead of using hydrogen as a fuel for internal combustion engines, where efficiency is

still constrained by Carnot’s law, this energy carrier can be converted directly to electricity by an

electrochemical reaction conducted in a device called fuel cell (FC). It is highly efficient and does not

generate any tailpipe CO2 emission or other pollutants.

That kind of technology has been implemented in passenger cars and city busses. There were many

demonstration projects which proved that this technology works well there. (E-traction 2010).

There are also projects and research focusing on implementation of the fuel cell technology in trucks. At

first conventional diesel generators were replaced with a small fuel cell unit which provided electricity

for truck auxiliaries during stops.

In early 2010, in the US, Vision Corporation released its “Tyrano” truck which was claimed to be the

world’s first short and medium range haul fuel cell truck with zero tailpipe emissions (Vision

Corporation, 2010). The truck is powered by a combination of hydrogen fuel cells and lithium-ion

batteries. Thanks to 33 kg of stored hydrogen it has a range of 400 miles. According to its manufacturer

the Tyrano truck is 35% cheaper in operation than current trucks powered by diesel engines and 50%

cheaper than trucks using liquefied natural gas. The torque and the peak power output of the Tyrano

equals respectively 4500 Nm (a value approximately twice higher than for an average diesel-powered

truck) and 400 kW.

Analysis of different technologies for fuel cell truck

As far as the feasibility of fully operational heavy duty truck powered by hydrogen is concerned the

thesis study has been completed. The most suitable technologies of powertrain components are being

investigated in order to create a preliminary design of a full-scale hydrogen fuel cell truck and using the

following criteria:

• Performance

• Complexity of unit

• Size

• Price

• Durability

• Sustainability of the production

• Availability of raw materials for the component production

The research that was conducted pointed out that the most suitable technology for electrochemical

conversion of hydrogen is the high temperature PEM fuel cell technology. To fulfill power requirements

the maximum power of electrochemical electricity generator should be at the level of 350 kW. An

assumption was made that the performance of hydrogen fuel cell powertrain would be at least the

same. According to the state of the art a fuel cell available on the market in 2009 (Ahluwalia & Wang

2010) was characterised as follows: the content of platinum estimated at 150 – 200 g (content of Pt in

FC 0.57 - 0.42g/kW), the mass of the stack - 200 kg (power density for the stack 1.77 kW/kg, power

density of the system estimated at 0.5 kW/kg).

A technology chosen for the hydrogen storage was the one that compresses the hydrogen at 35MPa. To

obtain a rough estimation of the hydrogen storage quantity it was assumed that the conventional truck

average consumption is about 35 liters per 100 kg. Another assumption was that the fuel cell

powertrain has the same efficiency as the conventional one. Energy content of 1l of diesel fuel is

approximately 10 kW. In order to provide the range of 500km, the energy stored in hydrogen must be

equal to 1750 kWh (53 kg of H2). As far as the gravimetric and volumetric energy densities are concerned

the mass and the volume of the compressed hydrogen tanks are respectively equal 1000 kg and 2.6 m3.

.

For propulsion purposes two SM700/3 wheel motor units were chosen. According to Błąd! Nie można

odnaleźć źródła odwołania.. the mass of each device equals 725 kg.

The investigation indicated that supercapacitors are probably the most suitable technology for buffer.

To guarantee good operation of system buffer should be rated at least 20% of fuel cell power which is

70kW. To obtain such power estimated weight of pseudocapatiors is about 12 kg. However, to maintain

reasonable energy buffer (equal to energy produced of full power by in fuel cell in 2 min) the quantity of

supercapacitors must be increased then estimated weight will be 400 kg.

The preliminary hydrogen fuel cell truck design is shown on the Figure 2.

Figure 2 - Preliminary design of full-scale hydrogen fuel cell truck

Comparative evaluation of a hydrogen fuel cell truck and a diesel truck

Applications of suitable components for hydrogen fuel cell truck powertrain that are listed above, make

the design comparable with a conventional diesel truck in terms of gravimetric power density.

A calculation proved that the total weight of a concept powertrain is 400 kg greater than the weight of a

conventional truck. A difference in mass between the two objects is relatively not important in

comparison to the total mass of the truck which on average is 18 tons.

The volumetric energy density factors reveal weaknesses of the hydrogen fuel cell powertrain. However,

investigation shows that there are some spaces in the truck in which system elements can be

accommodated.

Advantages of the unconventional hydrogen fuel cell solution for a truck powertrain are as follows: no

tailpipe emission of gases like CO2, NOX, SOX, a possibility of better energy management which can lead

to an increase in efficiency and energy savings. Of course the challenges of high prices and the durability

of the technology should still be considered. .

Non fossil fuel refrigerated semi-trailer designs

Another focus of this thesis was to choose the best technology for a semi-trailer refrigeration unit which

would cooperate with the hydrogen fuel cell powertrain system. Two approaches were considered: the

design with an electric chiller and the design with an absorption chiller. Advantages and disadvantages

of both solutions are presented below:

Refrigeration unit powered by electricity:

• Electricity can be taken from the main fuel cell

• Can work separately from the truck

• Well-known technology

• Relatively cheap

Refrigeration unit with an absorption chiller:

• Uses waste heat

• Cannot work without truck

• Complicated and expensive system

Investigations confirmed that the refrigeration unit with a compressor and an electric motor would be a

better solution. The energy needed to power it can be provided from the fuel cell which gives electricity

for propulsion. This solution leads to retaining the quality of products’ storage at the same level.

A small-scale model of a hydrogen fuel cell truck

This thesis also includes a comprehensive design of a small-scale model of a fuel cell hydrogen truck.

The small-scale model has been designed and partially constructed so that we can:

• become familiar with the fuel cell technology

• gain more experience in system controlling and optimizing

• expose biggest challenges of the proposed design

• collect experimental data which can be later used for scaling up

The comprehensive design of a small-scale model of a hydrogen fuel cell truck has been completed as a

part of this project. System components have been ordered.

Figure 3 - Design of small-scale hydrogen fuel cell truck model

Originally the small-scale truck model has not been designed to be powered by a fuel cell. To

accommodate fuel cell and other devices involved in the project some originally placed components of

the model have been changed, removed or relocated. It has been decided that the assembly power

system should be placed under the cabin of the truck. The data acquisition system has been situated in

the trailer.

The polarization curve describes the relationship between the voltage and the current of the stack over

time. The polarization curve of all the PEM fuel cell has a similar shape, which is caused by loses occuring

in particular intervals. In order to check if a particular device provided by the manufacturer performs as

it is expected a suitable survey stand has been created.

Figure 4 - Electric circuit diagram for polarization curve measurement (Horizon 2010)

Polarization curve measurement of the H30 Horizon fuel cell has been done. Figure 5. below compares

the polarization curve which was obtained from the conducted measurement with the polarization

curve with was obtained from the manufacturer’s data.

Figure 5 - Comparison of polarization curves obtained from measurement and the ones from manufacturer’s data

Furthermore, software modeling has been used to find out the best layout for the system elements. The

fuel cell and other canisters elements of driveline must be placed under the cabin like the control unit

for fuel cell, the pressure regulator and elements for the data acquisition system (e.gl the pressure

transducer and the hydrogen flow meter). When the fuel cell operates in a cabin compartment the

temperature rises up to 50oC. The air humidity is relatively high because of exhaust products of the

electrochemical reaction. Those conditions can have some negative impact on electronic components

placed nearby the fuel cell. In order to solve the problems a special cage has been designed. It separates

the control unit humidity from the measurement unit humidity.. Moreover, according to the

manufacturer’s advice after operation the fuel cell must be stored in an air tight container to prevent

drying of the membranes. Cage assembling makes easer remove stack out of model truck to storage.

Figure 6 - Cage assembly of fuel cell system for model truck

To provide sufficient ventilation some of the cage walls can be made of metal net. The space between

metal plates above the fuel cell is designed to supply stacks with fresh air and to cool down the

electronic elements mounted to the upper surface. The truck cabin will be modified in order to separate

the fuel cell from the electronic compartment.

Figure 7 - Air flows through the cage assembly

Assessment of the possibility of introducing the fuel cell technology to heavy duty trucks in Poland

The final section focuses on refueling the infrastructure and on the possibility of direct introduction of

the hydrogen fuel cell truck technology in Poland. Some obstacles are pointed out and some solutions

are proposed.

One of the greatest barriers to introducing the hydrogen technologies in Poland is the lack of interest in

popularization of this kind of energy carriers on the government’s side. Without public support it is not

possible to start any demonstrative project which would be very important in recommending this

technology to potential users. Moreover, without such a support no hydrogen refueling station can be

built. The lack of hydrogen infrastructure leads to the lack of users’ interest in buying hydrogen

powered vehicles.

So far in Poland there has been no hydrogen infrastructure at all. Poland’s hydro and wind potentials

make it possible to use these two sources to produce hydrogen without any associated emission.

Furthermore, it is also possible to use biomass for this purpose since the government strongly opts for it,

although this solution does not seem to be an ideal as it was stated in this thesis before. Since electricity

production in Poland comes mostly from coal-fired power plants and electricity prices differ during peak

on and peak off hours, it is possible to use surplus electricity at night to produce some cheap hydrogen.

Poland has a unique possibility of using salt caverns located in the south of the country for mass storage

of hydrogen. Currently similar cavers are used in Poland to store natural gas and liquid fuels.

These are the reasons for searching some alternative drivetrain designs especially in countries like

Poland. The alternative solutions should be used before the hydrogen refueling infrastructure is ready.

They should focus on the most efficient usage of currently available fuels including implementation of

hydrogen technologies.

One of the most feasible solutions is an application of an on-board fuel reforming system. However, this

solution does not lead to cutting down on fossil fuels. Furthermore, the possible reforming does not give

much hope for any substantial improvement in efficiency.

Among currently available methods of reforming two were considered as the most suitable for

automotive applications: partial oxidation and auto-thermal reforming. For the auto-thermal reforming

water - converted to steam and oxygen - is required (what creates a need for an additional water tank).

Despite this fact auto thermal reformers are considered to be the best solution for reforming diesel oil

for automotive applications. According to Karatzasa and Nilssona (2008) this method seems very

promising because of its high efficiency (up to 75%), low system complexity and relatively quick start-up.

The biggest disadvantage of this type of conversion is insufficient hydrogen purity which is not suitable

for direct use in a PEM fuel cell. Some purification system needs to be implemented, which will make

the system more complex and more expensive.

Due to the above-mentioned facts full-scale fuel cells in heavy duty trucks powered by diesel oil are

feasible but such a design doesn’t bring any profits in terms of energy use and pollution emissions.

Setting up demonstration projects and investing in refueling infrastructure seem to be best solutions for

Poland.

Conclusions

It has been proved that the design of a hydrogen fuel cell truck is feasible. The investigation reveals the

most suitable technologies for a zero emission hydrogen heavy duty truck:

• High temperature PEM fuel cells for electricity production

• Compressed hydrogen tanks for energy storage

• Wheel motors used for propulsion instead of classic drivelines

• Supercapacitors as a technology for energy buffer

Usage of those components for a powertrain makes this design comparable with a conventional truck in

terms of gravimetric power density.

Advantages of the unconventional hydrogen fuel cell solution for a truck powertrain are as follows: zero

tailpipe emission of gases like CO2, NOX, SOX, potentially better energy management which can lead to a

rise of efficiency and to energy savings. Still, the challenges of high prices and the durability of the

technology should be considered. .

Refrigeration semi-trailers can operate with fuel cell trucks. Instead of producing energy which powers

the compressor in a separate generator the energy can be provided by a fuel cell which supplies

electricity for propulsion. This solution leads to retaining the quality of products’ storage at the same

level but with better efficiency since bigger units are always more efficient than small ones.

Absence of refueling infrastructure in Poland poses an obstacle to direct introduction of the hydrogen

fuel cell truck technology. So, in order to make the introduction possible an on-board reforming system

must be implemented. Use of a fuel conversion system leads to dramatic losses in efficiency and does

not stop pollutions coming form haul trucks. For implementing this technology in Poland some

governmental support is needed, because the refueling infrastructure elements should be built in the

country’s strategic points.

A comprehensive design of a small-scale truck model with data acquisition has been completed. All

components have been ordered. The model has not been assembled because of delays in delivery of the

components.