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:

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.