Senior Design team builds on Smith’s battery research

06/14/2017
 
Assistant Professor Kyle Smith.
Assistant Professor Kyle Smith.
Battery research involves electrochemistry, materials science, and transport of ions and electrons – not typical topics of study for mechanical engineers especially at the undergraduate level. However, MechSE Assistant Professor Kyle Smith believes that mechanical engineers have skills and knowledge to engineer the next generation of redox flow batteries, particularly in their training with design, mechanics, and transport phenomena. 
 
This includes recent work done by a Senior Design group advised by Smith. The group, made up of ME seniors Wiley Jones, Jonathan Libock, Michael Bettinardi, and Alexander Notton, designed a device that solved several problems associated with redox flow batteries. They based their work on a paper written by Smith and his PhD student Pavan Nemani, which is currently being reviewed for publication.   
 
As part of the Joint Center for Energy Storage Research (JCESR), funded by the U.S. Department of Energy, Smith and his research group are developing batteries to store energy on the electric grid to enable efficient use of renewable energy resources. These redox flow batteries (RFBs) use two separate liquids that store charge in molecules at different potentials. When charge is exchanged between these liquids inside a reactor, energy is either stored or released. 
 
Smith and his group are working on how to improve the performance of these batteries. 
 
In his research, Nemani found that processes occurring within the tanks – rather than in the reactor of the battery – was leading to energy losses. 
 
“The essential principle of what we wanted to do is to somehow separate the liquid going into the reactor from what’s coming out,” Nemani said.
 
Although having two tanks could be an effective solution for separation, it is not cost-effective or realistic if the batteries are to be used on a large-scale grid. 
 
That’s where the Senior Design team came in. Working with Smith, the team developed a passive system to keep the two liquids separated in the tank—increasing efficiency and keeping costs down. 
 
“Ultimately, we needed to provide a tank design that would improve mixing suppression without increasing the cost of the whole RFB system past a point where it was no longer feasible to produce,” Jones said. “We could have recommended an active strategy that would ensure great mixing suppression, but the costly design rendered the system useless because it would have been too expensive in a real-world implementation.”
 
The team's CAD model (left) and their solution for the mixing suppression tank.
The team's CAD model (left) and their solution for the mixing suppression tank.
Their passive system was a single tank with baffles set up on the sides to suppress mixing.  Less mixing means that the entire battery can achieve high levels of energy storage while operating at low flow rates, which translates to lower pumping costs. 
 
“We were very surprised by how our most simple design ideas proved the most effective,” Jones said. “Early on in the project the fact that ‘simpler is better’ wasn't clear, but the more research and investigation we did we came to realize that we were overthinking certain parts of the problem. The best idea was laid out in our objective, which was to make a cost-effective design.”
 
This design, coupled with Nemani’s research, could allow for different types of redox active liquids to be used in flow batteries, including redox-active polymers that Smith’s group is researching within JCESR.
 
“The potential impact of the device is that it could help to enable integration of new types of redox active fluids in flow batteries that could reduce the cost of the flow battery overall, increase its rate of charge and discharge, and increase its longevity,” Smith said. 
 
This potential impact is what drew the group to the project. 
 
“RFBs are becoming increasingly more cost-effective and we hope that our design proposal could help continue increasing their viability in grid-scale energy storage applications,” Jones said. 
 
Nemani and Smith’s paper is currently in review for publication, but can be accessed freely here. The Senior Design team was sponsored in part by Shell.