Hydrogen Storage and Delivery System for Automotive Application

You have been asked by your supervisor, the Director of Engineering Development, to explore the possibility of using a hydrogen fuel cell in place of the batteries in an electric vehicle. Your specific assignment is to provide the design calculations for the on-board hydrogen storage and delivery system for a specific car. The intent is to replace the existing batteries with a high pressure cylinder with no more than 75% the weight of the batteries. Other specific calculations will provide data for design of the piping system. Report your results to the Director in a technical memo, with an attached spreadsheet showing the requested information. Present your chosen design for the storage vessel with your rationale for the choice. Remember that the Director is very busy; she will expect to see the most important results of your work summarized in the introductory paragraph.

To help design the hydrogen flow system, please provide the following hydrogen flow information:

Hydrogen properties at fuel cell conditions: density (kg/m3), specific volume (Liter/mole)
Hydrogen flowrate at peak and average engine power in mol/s, std liter/min, actual L/min
Hydrogen velocity and Reynolds Number at peak engine power in pipes ranging from 2 to 6 cm inside diameter (table of results).
Plot of hydrogen velocity and Reynolds Number vs pipe diameter on a single chart, using separate vertical axes for the two dependent variables

Recommend a hydrogen storage cylinder by considering the storage volume requirements and the mass of the storage vessel. The hydrogen storage capacity and weight should be similar to the specifications for the battery that is being replaced. Determine the hydrogen storage volume needed at several storage pressures and for several operating times, as indicated below:

Storage Volume Needed for Vehicle, liter
Operating time, hours / Required pressure of storage tank, atm
125 / 150 / 175 / 200
5 /
4
3
2

Assume the vehicle operates at the average engine power level for each period of time. Relevant specifications for the electric vehicle are the following:

Peak engine power - 235 hp (175 kW) (assume 100% efficiency for fuel cell)

Average engine power – 17.5 kW

Battery energy storage – 40 kWh

Battery mass –320 kg (specific energy of 125 Wh/kg)

From the results in your spreadsheet model, select a compatible storage tank from the available storage cylinders shown in the Design and Safety Handbook for Specialty Gas Delivery Systems (pages 46 – 48). Determine how many tanks of this type can be used without exceeding the weight limit given above. Then calculate the actual operating time for this storage option using the total volume of the tanks. Repeat this process to identify 3 possible tank storage options (tank type and number of tanks). From these options, select one to recommend. Discuss your storage tank selection in your memo, explaining why you chose the particular design.

This project is due Wednesday 3/4/2013 prior to your class. You should submit a one to two page spreadsheet printout (no reduced printing) as well as a cover memo that briefly discusses your work and presents your chosen tank and your reason for its selection. In your memo, also address the following reflection question: What have I learned while doing this project (about using Excel, about engineering design, hydrogen technology, about yourself, etc). Follow the guidelines for a technical memo in the posted document.

Submit your spreadsheet file via Blackboard (click on the “Project 1” item in assignments to submit your files) prior to class, using a file name: EAS112Proj1_yourName.xlsx.

Useful Links:

Design and Safety Handbook for Specialty Gas Delivery Systems, Air Liquide Company,

copy available on Blackboard site for EAS112.

Specifications for Tesla:

Project 1 Report Requirements and Calculation Procedures

In setting up the worksheet, follow the assignment format guidelines for calculation, layout and documentation.Be certain to use cell references for all data so that your results will instantly update if you change an input variable. For example, if the engine power requirement is changed from 17.5 kW to 20 kW, all calculations should immediately change with no intervention on your part. In setting up the table of storage volumes, use absolute and relative addressing schemes so that the formula entered into the first cell can be copied across and down to correctly reference the times and pressures. Set up named cells for constants.

Heading to identify author, course, project, date, etc.
Brief problem statement and diagram to document what is being done
Documentation of calculations (major equations used, list of assumptions made, etc.)
Table of inputs parameters, variables and constants, including units
Textbox giving a brief interpretation of the results and reasons for the choice of cylinder(s)

Equations for use in Hydrogen Storage Project:

Hydrogen usage is related to power produced by the following equation:

NH2 = moles H2/sec,Pe = electric power, watts, Vc = voltage per cell, 0.65 volts

F = Faraday's Constant, 9.65 * 104 Coulombs/mole of electrons

unitsnote: P (Watts) = V (volts) * I (amperes), and 1 ampere = 1 Coulomb / sec

Volume and gas density: from the ideal gas equation:

R= 0.08206 liter-atm/gmol-K n = moles of hydrogen

T = absolute temperature, K, V =ideal gasvolume, liters

P = pressure, atm.Ρ = density, g/liter, kg/m3

Flowrates: ideal gas equations can be used to relate molar flow rate to volumetric flowrate – moles per unit time replace moles in the equation to yield liters per unit time, etc.

M=mass flowrate in g/s = N * Mw,Mw = molar mass in grams/mol

standard volumetric flowrate (std liters/s) = N * 22.4

[note: standard volume is the volume for this number of moles at 0oC, 1.0 atm]

Vflow= actual volumetric flowrate in liters/s, divide by 1000 to get m3/s

v=velocity, meters/sec – note that volume must first be converted to m3

A = inside area of tube or pipe, m2, area = Π D2/4

D = pipe inside diameter, m

Reynold's Number:a dimensionless number used to determine the degree of turbulence for a fluid flowing in a pipe,

μ = viscosity, = 8.80x10-6Pascal-sec ( kg/m- s )