7/30/2019 Diesel vs Hydrogen

1/2

INDIVIDUAL ASSIGNMENT Engineering Sustainable Development 201

Due Date : 13/09/2013

Scenario 1 TransBus, PerthThis is a hypothetical example that we have developed for you to carry out the task

More than 95% of Australias transport energy comes from fossil oils. There is anincreasing awareness of health effects and environmental impacts due to emissions

from the combustion of these oils.

TransBus is one of the Perths largest bus companies having a fleet of 450 diesel-

powered buses covering 33 million route kilometres and transporting more than 26

million passengers annually. It employs 850 staff to manage the operations. The

company is planning to use hydrogen fuel in their new buses. The company is

committed to reduce GHG emissions and so they will use clean fuel. They have

identified Hydrogen as a clean transport fuel because the combustion of hydrogen

produces no pollutants; the only emissions are water and heat. The company will makethe decision on the basis of carbon and cost saving benefits associated with the

substitution of diesel with hydrogen fuel in TransBus buses.

Your task is to compare economic and environmental benefits associated with the

replacement of diesel with hydrogen fuel following the procedure stated in the handout

of week 1.

Please follow the steps below to the calculate functional unit:

Calculate the GHG emissions from the production and use of hydrogen fuel inthe internal combustion where the hydrogen was produced from steam methanereforming process. The functional unit is the number of kilometres travelled by a

hydrogen powered bus. The functional unit is calculated by multiplying 50 by

the sum of the last two digits of the student ID numbers of all students in your

group. (i.e. if ID numbers of all group members are 1432510, 1432528,

1432587, 1432506 and 1432593, the total kilometres travelled is calculated as

50x(10+28+87+06+93) = 11,200 kilometres).

Similarly, calculate the GHG emissions from the diesel run vehicle for the samefunctional unit.

Once carbon footprints of buses powered by diesel and hydrogen arecalculated, calculate the carbon saving benefits of this substitution for a carbon

tax of $ 20.00 per tonne of CO2 e-. Following this, please calculate the total

profit, which includes carbon saving benefits and operational benefits.

Data to be used for comparison purposesPre-combustion takes in to account all GHG emissions released during exploration,

production, refining and delivery of the fuel while combustion emissions are the

exhaust pipe emissions produced when the fuel is burnt in the vehicles engine.

7/30/2019 Diesel vs Hydrogen

2/2

INDIVIDUAL ASSIGNMENT Engineering Sustainable Development 201

Due Date : 13/09/2013

Economic/Technical Specification and Life Cycle Impact for the Average Diesel -Powered BusBus maintenance cost $ 0.50/km

$ 50,000 for replacing engine at every 1,000,000 km

Energy consumption 19.3 MJ/km (2.00 km/l diesel) - $ 0.78/km @ $ 1.57/lEmissions (g/km) Fuel Production Stage Combustion StageCO

2emissions 0.014 kg CO2 e- / MJ

73.25 g/MJ

Economic/Technical Specification for the Hydrogen/Fuel Cell BusBus Maintenance cost $ 0.60/km

$12,000 for replacing fuel cell stack at every 5,000 hrsEnergy consumption 11.99 MJ/km costing @ $ 6.5/kgStage of Steam Methane Reforming Method

0.5667 kWh electricity is consumed to extract 1 kg Natural gas, where 141 m3 ofnatural gas is required to obtain 1 kg of hydrogen.

6.556 kWh electricity per kg of hydrogen are consumed for the process at 20bar

0.894 kWh electricity is consumed for Compression of hydrogen into largetransport trailers at 165 bar

0.45 L/km diesel is consumed for hydrogen distribution to fuel station via Dieseltanker truck, where an average distance between hydrogen plant and fuel tank

is 100km.

0.236 kWh electricity is consumed for compression of the hydrogen intomedium-term storage tanks at fuel station at 300 bar

0.0538 kWh electricity is consumed for compression of hydrogen into buses at350 bar

Density of hydrogen 0.0899 kg/m3, calorific value of hydrogen 121,000

kJ/kg.density of natural gas is 0.9 kg/m3.

\ Density of Diesel 0.84 kg/litre, heating value of diesel is 38MJ/litre

Emission factors

Electricity 1.032 kg CO2 e- /kWh Diesel production 0.014 kg CO2 e- / MJ Emissions from the combustion of diesel - 73.25 g/MJ