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AggiE-‐Challenge Sustainable Electricity Genera2on with Zero-‐Pollutant from Fuel Cells
John Pia>a, Josh Newmannb, Logan Mertzb, Rebekah Taylorb, Deepak Bha2ac, Jonathan Bryantc, Taylor Chambersc and Nathan Kudlatyc
a. Department of Chemical Engineering, b. Department of Mechanical Engineering, c. Department of Electrical & Computer Engineering
Abstract The objec2ve was to design and build an improved fuel cell system based on the prototype currently used by Dr. Yu’s research team for the tes2ng of novel carbon nanotube (CNT) based catalyst layers. The goals included designing and building a larger fuel cell with op2mized flow field channel pa>erns; new satura2on heaters to replace the current water boiler; and op2mize a new fuel cell system as a whole that would be semi-‐portable, more convenient to use, and deliver improved power density. Each of the three components was built into a func2oning PEM fuel cell system which was demonstrated capable of powering a small fan.
The Approach The fuel cell and its adjoining system were designed primarily for the research of high performance carbon nanotube (CNT) based electrodes, to provide an improved tes2ng apparatus over the Nano-‐energy lab’s exis2ng prototype. To meet this demand the following specifica2ons were met:
• Self-‐contained, single unit, semi-‐portable system housing the following components: PEM fuel cell, gas bubblers, pressure gauges, flow meters/controllers, and temperature controllers
• Improved bubbler design to deliver wet gas to the electrodes at 80oC
• Increased membrane and electrode surface area ( 25 cm2 )
The PEM fuel cell is constructed from two graphite bipolar plates each heated by an aluminum endplate block. A CNT based catalyst layer is placed adjacent to the channels on each of the bipolar plates. For the PEM a nafion membrane is placed between each catalyst layer. The construc2on is represented in figure 3.
Bipolar Plate Design The objec2ve of the bipolar plate design was to maximize the effec2ve area, limit condensed water vapor, and provide the most consistent concentra2on profile across the catalyst layer. To meet these requirements, a mirrored set of serpen2ne channels were machined into each of the graphite plates, where three channels were machined per serpen2ne path to allow the most efficient use of the area. In theory the shortened flow paths decrease the chance of a large concentra2on drop along the graphite plates or development of water condensa2on, this should allow more hydrogen and oxygen to interact with their respec2ve catalysts to help maintain the electrochemical reac2on rate.
Performance Tes9ng Aber the PEM fuel cell system was built it underwent mul2ple performance tests. The fuel cell and system were shown capable of holding the required pressure, and the controllers ran accurately. The system can be seen func2oning in Figure 4, powering a small fan. Figure 5 shows the condi2ons under which the fuel cell was operated for its power performance test.
The objec2ve in con2nuing this project into the future will be to increase number of individual cells within the system for great poten2al power output and improve the portability of the system, crea2ng a system design capable of powering a small vehicle, such as a golf cart.
While developing new fuel cell technologies, an important factor is to be able to quickly characterize a large number of various electrodes to accelerate research and development in fuel cell electrode development. A mul2channel impedance spectroscope is being developed to accomplish this goal. A block diagram for the “Lock-‐In” amplifier topology used in this spectroscope is shown in Figure 6. The individual blocks of this system have already been developed and tested. Proof of concept has been shown for all of the subparts of this system. Currently integra2on and func2onality tes2ng is being worked on. This system will enhance the tes2ng and characteriza2on of electrodes for easier development for fuel cell technologies.
Figure 6: Block Diagram of Impedance Spectroscope
Impedance Spectroscopy