The Dynamics of Team Tennessee’s Energy Storage System

With the EcoCAR 2 Year Two competition rapidly approaching, the University of Tennessee’s EcoCAR 2 team continues to work on their 2013 Chevrolet Malibu at a feverish pace. As the key elements of the vehicle fall into place, perhaps none are more important than the integration of the energy storage system (ESS). An important part of the ESS is the cooling system that is to be integrated into the design.

A cooling loop for the ESS was designed in order to maintain the seven integrated A123 Systems lithium-ion batteries at an optimum operating temperature range.  This loop consists of several aluminum cooling plates in a series. An ethylene glycol and water mixture pumped through the plates at a target flow rate of 15 L/min. These plates are placed on either side of the battery modules with a layer of thermally conductive material compressed between the cooling plate and battery module in order to improve heat transfer.

The ESS is crucial to the improved performance of Team Tennessee’s Malibu. In order for it to be maintained with minimal degradation, it must be operated between a certain temperature. This temperature will be attained using a dual core radiator as a heat exchanger in conjunction with an air conditioning chiller (which is also utilized in the Chevrolet Volt). The chiller acts as the main cooling component within the ESS cooling loop. A two-way bypass valve will act as a cutoff for the chiller so that when additional cooling is not needed it can be bypassed entirely, conserving energy and saving the system from operation at less than ideal conditions.

All of the components of the cooling loop work in conjunction to keep the ESS operating at ideal temperatures. This makes it essential to not only the operation of the ESS, but the entire vehicle.