An Assessment of Reverse Electrodialysis for Application to Small-Scale Aquatic Systems
Total Page:16
File Type:pdf, Size:1020Kb
An Assessment of Reverse Electrodialysis for Application to Small-Scale Aquatic Systems by Marc C. Samland B.S. Mechanical Engineering United States Military Academy, 2016 Submitted to the Department of Mechanical Engineering in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering at the Massachusetts Institute of Technology June 2018 © 2018 Massachusetts Institute of Technology. All rights reserved. The author hereby grants to MIT permission to reproduce and to distribute publicly paper and electronic copies of this thesis document in whole or in part in any medium now known or hereafter created. Signature of Author: Department of Mechanical Engineering May 25, 2018 Certified by: Douglas P. Hart Professor of Mechanical Engineering Thesis Supervisor Accepted by: Rohan Abeyaratne Professor of Mechanical Engineering Chairman, Committee for Graduate Students THIS PAGE INTENTIONALLY LEFT BLANK 2 An Assessment of Reverse Electrodialysis for Application to Small-Scale Aquatic Systems by Marc C. Samland Submitted to the Department of Mechanical Engineering on May 25, 2018 in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering ABSTRACT Reverse electrodialysis (RED) is a means by which to produce electrical power through the flow of Na+ and Cl− ions from seawater to fresh water across ion selective membranes. While current research has largely focused on utilizing RED for large-scale commercial power, this thesis explores the feasibility of using RED as a power source for remote sensing devices and unmanned underwater vehicles, with a specific focus on the Arctic Ocean. A parameter sweep is developed using MATLAB in order to estimate the ideal dimensions and flow rates for an RED stack with respect to its volumetric power density. Unlike previous models, this model accounts for considerations unique to RED’s application to unmanned underwater vehicles and remote sensing devices in variable environmental conditions. The model maintains broad generality for use with a variety of RED design configurations, while also demonstrating agreement with empirical data collected from specific experimental tests. The computational model is validated by empirical data from three previous studies and used to find a specific and volumetric power −3 3 density for RED of 2.35 W/kg and 206 × 10 W/cm at 298K with salt concentrations of 0.7 and 35 g NaCl/ kg H2O. This thesis then compares RED to other environmental energy harvesting systems and determines RED to be a competitive power source within the environmental constraints of the Artic. Regarding the use of RED as a secondary power source to charge lithium ion batteries, it is found that it would require an RED stack over four days to recharge a lithium ion battery of equal mass and over thirteen days for a battery of equal volume. For use with low power systems requiring constant power, an RED stack could supply more power than a lithium ion battery of equivalent mass for durations longer than three days and ten days for one of equivalent volume. Thesis Supervisor: Douglas P. Hart Title: Professor of Mechanical Engineering 3 THIS PAGE INTENTIONALLY LEFT BLANK 4 Acknowledgments I would like to thank all my friends and family for their encouragement and constant support in the midst of this endeavor! Without you I am certain that I never would have come this far. Your love and friendship have helped me persevere as I have been molded into the officer and engineer that I am today. To my parents, Jim and Debbie, you guys have always been a source of encouragement and wisdom, even when I didn’t care for it at the time. Thank you for your unconditional love and support through thick and thin. You have always been there to help me achieve my dreams from attending USMA to now studying at MIT. Dad, I owe you special thanks for acting as the ultimate grammar check for all of my written work. Your last minute proofreading has been such a boon during my academic career! To my siblings, Alex and Anna, your encouragement never ceases to put a smile on my face. You continue to play a huge role in my life, even as we are scattered across the world. To Chris Swanson and Chris Lawson, the instrumentality of your discipleship and mentorship on my life here at MIT cannot be adequately expressed in words. You have made my learning experience at MIT so much more than merely academic, teaching me how godly men navigate life. I hope I can emulate the character and steadfastness that you have shown me. To Eric Morgan, thank you for your mentorship and guidance these past two years. I’m certain that without your encouragement, guidance, and understanding in the midst of difficult times that I would never have made it. My only regret is that I never got to writing this thesis in LaTeX for you. 5 To Doug Hart, thank you for adopting me into your lab family and for teaching me all about the world of academia. Your insight and stories taught me so much! Thank you again for your flexibility in helping me to finish this thesis. To all of those in Doug’s Fun House, thank you for making the lab a fun place to be and for all your advice and insight over the last two years. To Mark, I never get tired of hearing about your adventures around the globe. Maybe one day I will even catch up to your country count. To Brandon, your help and patience with my research can’t be quantified. To Thanasi, thank you for your mentorship and not blinding me with your laser. To Alban, without you our lab group would be a mess. To Peter, I wish I could cross match my socks and spend Doug’s money as well as you. To Jason, I hope your enthusiasm for research never fades! Finally, to that old Annapolis grad, thank you for teaching me the ropes of how to survive MIT as an Academy grad. Too bad Navy can’t seem to pull it together… Go Army, Beat Navy! To Vicki Dydek and the members of Group 73 at Lincoln Laboratory, thank you for your assistance these past two years. Your feedback, advice, and support have played a significant role in making this research possible. To Jason Vincent, and Jake, you guys introduced me to MIT and ensured I stuck around with Cru. Your friendship has been huge and I’ve missed you guys. To Jasper and Rich, you guys have helped me survive these past two years, holding me accountable and devising activities to give me a break from research. Your loyal friendship has meant a lot. Finally, to SWAT, I love you guys and can’t wait to hear about the impact you’ll make these next few years. Soli Deo Gloria. 6 THIS PAGE INTENTIONALLY LEFT BLANK 7 Contents INTRODUCTION AND BACKGROUND............................................................................... 17 1.1 SALINITY GRADIENT POWER ................................................................................................ 18 1.1.1 Gibbs Free Energy of Mixing ....................................................................................... 18 1.1.2. Capacitive Mixing (CapMix) ....................................................................................... 19 1.1.3 Pressure Retarded Osmosis (PRO) .............................................................................. 21 1.1.4 Reverse Electrodialysis (RED) ..................................................................................... 24 1.2. RED APPLICATIONS ............................................................................................................ 28 1.2.1 Geographic Areas of Interest ....................................................................................... 28 1.2.2 Application to the Arctic ............................................................................................... 29 1.2.3 Applications to Small Mobile Platforms ....................................................................... 32 COMPUTATIONAL MODELING .......................................................................................... 35 2.1 GOVERNING EQUATIONS AND ASSUMPTIONS ....................................................................... 36 2.1.1 Key Assumptions ........................................................................................................... 36 2.1.2 Fundamental Equations ................................................................................................ 37 2.2 MODEL IMPLEMENTATION .................................................................................................... 42 2.3 MODEL VALIDATION ............................................................................................................ 43 2.3.1 Validation for Spacer-Filled Channels......................................................................... 43 2.3.2 Validation for Profiled Membranes .............................................................................. 47 COMPUTATIONAL RESULTS ............................................................................................... 53 3.1 RED STACK DESIGN OPTIMIZATION .................................................................................... 53 3.2 PREDICTED PERFORMANCE CHARACTERISTICS .................................................................... 60 3.3 COMPARISION TO ALTERNATIVE POWER SOURCES .............................................................. 63 FUTURE OUTLOOK AND CONCLUSIONS ........................................................................ 69 4.1 FUTURE OUTLOOK AND RESEARCH ...................................................................................... 69