Flow Battery

From Cell to Stack to System

Flow batteries separate the storage of electrical energy from the charge/discharge process; power and energy can be scaled independently of each other to meet the needs of many different applications. Very few technologies are realistically applicable to utility-scale electrical energy storage (EES); flow batteries are in an elite category. But they are also scalable to home and building applications for peak shaving or peak shifting, or for emergency backup power.

In a flow battery, energy storage is accomplished in arbitrarily large tanks full of electrolytes, while separate stacks of cells convert electricity into and out of different electrochemical (redox) states of those electrolytes. The tank on the left contains the catholyte, and the tank on the right contains the anolyte.


By Nick B, benboy00 - https://commons.wikimedia.org/wiki/File%3ARedox_Flow_Zelle_Deutsch_Farbverlauf.png, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=35143999

Of course, the single cell in the above diagram is actually a stack of about 14-19 cells in a real battery, a few of which are shown expanded below with both the membrane (typically DuPont NafionTM 117) and the porous graphite fiber electrode pads visible.

The charge collector plates also contain a serpertine "flow field" in the picture below, which is used to assure uniform distribution of electrolyte within the cell for minimum overpotential and reduced pumping losses.

There are many such plates in a stack, and many stacks are then plumbed in parallel in a battery. Time scales within a cell are on the order of fractions of a second, but any simulation of a flow battery must cover many days of charge/discharge scenarios.

This means that the complexities of modeling a realistic flow battery involve more than just combining fluid flow, thermal energy, electrical networks, and electrochemical treatment of redox reactions. They must also involve handling multiple time and distance scales simultaneously: you need to be able to zoom in on the fast time-scale multiphysics within a cell, while at the same time zooming out to the full system as it moves through its daily operational cycle.

Vanadium Redox Flow Batteries (VRFB) represent the current state-of-the-art, with 20+ years of reliable and safe operation demonstrated. Many research projects are underway to find alternate electrochemistries or membranes, or to reduce the cost and increase the performance of VRFBs.

Or just enjoy the diurnal variations of temperature gradients within a single cell of a 17-cell stack in a 6-stack battery over the course of a typical day:

 

Click here to fetch the VRFB case study on our User Forum

 

Advanced Pipes in FloCAD
Thursday November 14, 9-10am MT (8-9am PT, 11am-noon ET)
This webinar introduces advanced features for FloCAD pipes in addition to working with complex geometry. Complex geometry includes interior fins and surfaces for heat transfer, flow around enclosed objects, annular flow, concentric pipes, and more. FK Locators and TEEs as modeling objects will also be introduced.
Custom Heat Transfer and Pressure Drops
Tuesday November 19, 2-3pm MT (1-2pm PT, 4-5pm ET)
Do you know what the default assumptions are in FloCAD, and whether or not they apply in your situation? Do you know how far you can go past that starting point? The answer: pretty far. There are numerous mechanisms in FloCAD for adjusting factors, scaling uncertainties, and applying different or supplemental correlations. This webinar summarizes the options available to you to customize your flow models to make sure that they apply to each new situation you encounter.
Heat Exchangers: Detailed and System-level
Thursday November 21, 2-3pm MT (1-2pm PT, 4-5pm ET)
This is two webinars in one. The first explains the use and assumptions behind the FloCAD HX system-level modeling object. The second webinar describes detailed-level modeling of complex heat exchanger passages, including application of Compact Heat Exchanger (CHX) methods.
Starting in 2020, we will begin offering Introduction to Thermal Desktop and Introduction to RadCAD as either in-person training or online training, alternating between online and in-person every three months. The training uses lectures and demonstrations to introduce you to basic Thermal Desktop and RadCAD usage. Hands-on tutorials provide practice building models and interpreting results (tutorials are completed by students outside of the online class time).
 
The next training class will be an online format in January 2020:
  • Introduction to Thermal Desktop (and SINDA) - A three-part series on January 14, 16, and 21 from 9am to 12pm, Mountain time
  • Introduction to RadCAD - January 23 from 9am to 12pm, Mountain time
For up-to-date schedules, fees, and policies, visit our Product Training page. To register for the class above, complete our registration form and select "Online" for the Training Format.
 
If you are interested in product training for your company based on your schedule, please contact us to obtain a quote for training between 8-12 attendees. We can come to your facility or the lectures can be presented online. Descriptions of the available classes can be found in our course catalog.
 
To keep up with our training opportunities, take a look at our new Events and Training Calendar.