Day 2- August 7th
Day 2 AM - Battery and LED Cooling Session Track
9:00 am - 11:30 am CST
9:00 am CST
The Role of Temperature in Lithium-ion Battery Failure
Keith Beers, Principal Engineer • Exponent
When properly designed, manufactured, and handled, lithium-ion batteries provide safe and reliable portable energy storage. Unfortunately, both individual lithium-ion cells and assembled battery packs can fail in diverse ways, and the effort required by product designers and manufacturers to produce a high-quality, safe final product is substantial. Numerous issues related to lithium-ion battery reliability and safety can be caused or exacerbated by temperature.
In this presentation, we will provide a brief review of the fundamentals of lithium-ion battery technology to discuss the various mechanisms through which cells experience performance and / or safety issues. Where relevant, the topics chosen will focus on issues caused or exacerbated by temperature. Mechanisms will be discussed alongside test data, recreation scenarios, or through the review of case studies. The implications of cell form factor and chemistry will also be covered. The talk will conclude with a discussion of strategies for mitigating the risk of such failures. The contents of this talk will draw heavily from the collective experience of a leading failure analysis firm that has been involved with numerous investigations into lithium-ion battery failures and recalls, and the talk will be relevant across many different product types, from wearables to consumer electronics, automotive applications, and stationary storage.
9:45 am CST
Mitigating Cell-to-Cell Thermal Communication during Thermal Runaway Events in Batteries
Kevin B. Roth, Project Manager and Senior Research Engineer • ADA Technologies
Lithium ion (Li-ion) batteries are ubiquitous in space and military applications, allowing for development of more efficient and effective systems. The increase in Li-ion cell usage corresponds to an increase in risk associated with cell failure. Electrical short, overcharge, over-discharge, physical damage, and manufacturer defects can each result in cells undergoing thermal runaway. During thermal runaway, an individual cell overheats and can violently deflagrate, resulting in mission failure and personnel injury. Moreover, due to the proximity of cells in most battery systems, such a runaway event can cause overheating and subsequent thermal runaway of adjacent cells, resulting in a cascading failure event.
To address this potential failure mode, especially for high-rate and high-energy battery chemistries, a passive protection system as been developed, dubbed a cell isolation material (CIM), in which a blend of proprietary, protective materials on a metal substrate that is subsequently wrapped around each cell. The CIM material acts as an insulator and refractory material preventing flame and thermal energy propagation to adjacent cells. Simultaneously, the metal substrate works as a heat spreader, dissipating heat away from the wrapped cell to ensure no negative impact on normal/healthy cell operation. Currently, we have demonstrated effective protection of multiple cell formats; in particular, cylindrical cells and pouch cells ranging from 3 to 15Ah ratings, with plans to implement our safety solution into battery packs comprised of larger (prismatic), 72Ah cells. We have teamed with leading battery manufacturers and power systems integrators to appropriately design our system for functionality and performance in space and military environments.
10:30 am CST
Discussion on Thermosyphon’s Design for Passive Cooling of HighPower LED Panels
Dr. Sohail Zaidi, Senior Research Scientist • San Jose St. University
High-power LED panels are actively cooled to keep the operational temperature down as high temperatures can deteriorate LEDs efficiency. Current work at San Jose State University is investigating passive cooling techniques that may replace active cooling hardware, which is highly susceptible to malfunctioning causing irreparable damage to LED panels. The main objective of this work is to design a passive cooling system that will match or exceed the heat transfer effectiveness of other active cooling techniques being used in commercial LED panels.
For this work, a commercially available LED panel (200 W 192 LEDs) was selected. The LED panel uses two fans to cool its surface. In order to replace these fans, a heat sink was machined that fits LED panel and at the same time, accommodate ten in-house built thermosyphons. Thermosyphons were filled with R134a (𝑃𝑠𝑎𝑡@95°𝐶 500psi) at a lower pressure and were sealed. It seems that heat sink along with attached thermosyphons was able to replace both fans by bringing the operating temperatures below 40°C. To investigate further, a new heatsink is designed where its fins have multiple embedded thermosyphons. This design simplifies the previous design as each fin has multiple 3 mm diameter holes that open to a base plate where R134a is filled at a lower pressure to activate thermosyphon’s process at elevated temperatures. New experiments are being performed and comprehensive results will be presented in the conference.
11:15 am - 1:00 pm CST
Day 2 PM - Advances in Liquid Cooling and Materials
1:00 pm - 3:30 pm CST
1:00 pm CST
Liquid Cooling of a 17 kW Artificial Intelligence Supercomputer
Guy R. Wagner, Director • Electronic Cooling Solutions, Inc.
In the development of a deep learning supercomputer, the 17 kW heat dissipation of the artificial intelligence module consisting of neural networks far exceeded the limits of air cooling. To keep the neural network processor cores below their maximum operating temperature, a liquid cooling system was developed using computational fluid dynamics simulations to optimize the design of the manifold and cold plate in contact with the neural network sites. A 30% propylene glycol coolant pumped through the cold plate at the rate of 76 liters per minute keeps the temperature difference across all the cores to less than 6.2°C.
1:45 pm CST
Points of Connection: Critical Considerations in Liquid Cooling
Beth Langer, Lead Technical Engineer in the Thermal Management Business Unit • CPC
With the expanded use of liquid cooling in technology and energy equipment, fluid handling components are often incorporated right alongside critical electronic equipment or components. As designers embrace liquid cooling, attention to thermodynamics in combination with flow rate is critical -- whether the liquid cooling application is for HPC, electric vehicle charging, data centers or laser diode cooling.
System components and their respective designs matter. Individual component design delivers performance characteristics and combined create system efficiency (or inefficiency.) Flow rate, temperature and pressure requirements, side load, chemical compatibility, seal and valve types, and overall quick disconnect structure and material (e.g., stainless steel, brass and newer high-performance engineered polymers) all have significant impact on liquid cooling system functionality.
This presentation will refresh the audience on calculations to apply, suggest pitfalls to avoid in designing a system and highlight technical considerations for facilitating connection, disconnection and rerouting of fluid though equipment; supporting 100% uptime during installation, reconfiguration and maintenance; and specifying the appropriate connectors to meet performance requirements across liquid cooling systems in a variety of applications.
2:15 pm CST
Novel High-Performance Thermal Pads Utilizing Non-Silicone High Temperature Resin System
YongJoon Lee, R&D Director Polymer Composite Materials • Nanoramic Laboratories
The most commonly used methods for extracting heat from a high-power CPU or a SOC (system on chip) are thermal paste or grease. While these solutions offer high performance, they come with disadvantages. They can be messy, time consuming, and can have poor long-term reliability. Additionally, conventional high conductive (>20W/mK) Thermal Interface Materials (TIMs) are known to have high cost and manufacturing difficulties and challenges.
Utilizing TIM pads with carbon-based fillers and non-silicone high temperature resistance elastomer-based resins end-users can overcome these challenges. They are soft (Shore Hardness 00 : 60-65) and have a thermal conductivity of >40 W/mK. These TIM pads have thickness options from 0.3 to >5 mm and can be used in thin bond line applications and can perform well not only at low force (below 10 psi) to achieve low contact resistance like that of high-end thermal pastes but also at high pressure (>50 psi) to achieve great reliability under high stress, high power, high temperature environment.
Also, we have developed electrically insulating TIM pads utilizing ceramic based fillers with the same resin system. We have achieved very high thermal conductivity (>20W/mK) by overcoming the packing limit of ceramic fillers. Electrically insulating TIM pads show 1x1014 ohms volume resistivity and dielectric loss of <0.01 at 1MHz.
2:45 pm CST
N.I.S.T announces New Infrared Reflectance Standard
David Epner, President • Epner Technology
Thanks to the generous cooperation of Leonard Hanssen at the National Institute of Standards and Technology, this presentation will describe NIST’s methods and instruments used to calibrate a new gold electroplated Infrared reflectance standard. Shown will be reflectance data and examples of this ultra-high reflective coating on a variety of space craft substates including beryllium, titanium, tantalum and dielectrics.
3:30 pm CST