Welcome to our Energy Storage Laboratory at the National Renewable Energy Laboratory (NREL) in Golden, Colorado. Much of our testing is conducted at this state-of-the-art laboratory, where researchers use cutting-edge modeling and analysis tools to focus on thermal management systems—from the cell level to the battery pack or ultracapacitor stack—for electric, hybrid electric, and fuel cell vehicles (EVs, HEVs, and FCVs). In 2010, we received $2 million in funding from the U.S. Department of Energy under the American Recovery and Reinvestment Act of 2009 (ARRA) to enhance and upgrade the NREL Battery Thermal and Life Test Facility.
The Energy Storage Laboratory houses two unique calorimeters, along with several battery testers, to measure heat generation from batteries and ultracapacitors over a wide range of temperatures, power profiles, and sizes. Engineers use infrared equipment to capture a battery's or ultracapacitor's thermal imaging fingerprint to diagnose its behavior. In addition, the facility has many energy storage testers with power capabilities from milliwatts to kilowatts (more than 120 channels are available). Our capabilities enable world-class research in energy storage thermal management, battery and vehicle modeling and simulation, and energy storage from a vehicle systems perspective.
The largest and most accurate device of its kind, NREL's Large-Volume Battery Calorimeter (LVBC) can determine the exact amount of heat generated by battery cells, modules, sub-packs, and even some full-size packs as they are charged and discharged. No other battery calorimeter can match its size, temperature range, thermal isolation and control, current-load capacities, and precision measurements. One of its unique features is the ability to test liquid-cooled modules.
A predecessor to the Large-Volume Battery Calorimeter, the Battery Module Conduction Calorimeter features a smaller test chamber (about one-sixth the volume of the LVBC) and is used to measure heat generated from cells and modules under various temperature ranges and power profiles. Over the years, this unit has provided battery developers with valuable information about the heat generation of many battery chemistries, and today it continues to provide critical heat generation data for cells and modules.
The Bitrode cyclers in the lab are designed specifically for hybrid electric, electric, and fuel cell vehicle battery and ultracapacitor pack testing. Their voltages range from 0-420 volts with a maximum current output of 530 amps. These cyclers can meet the most demanding drive-cycle profiles. They are integrated with the calorimeter to measure heat generation under various charge/discharge cycles and for power profiles from vehicles. As a result of ARRA funding, we added seven new battery testers with more than 100 channels.
Accurate temperature measurement and control are critical for testing energy storage systems. Our environmental chambers and isothermal baths can control temperature from -35°C to 100°C with an accuracy of 0.1°C. With ARRA funding, we added five new environmental chambers with large volumes and excellent temperature control.
Check out these time-lapse battery thermal images (AVI 4.5 MB)!
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Engineers use thermal imaging equipment to capture an energy storage device's infrared fingerprint to evaluate and diagnose the behavior of energy storage systems in advanced vehicles.
This unique, custom-made alternating current (AC) power amplifier enables us to test energy storage preheating concepts for vehicles that operate in cold climates, and to evaluate the effects of high-frequency harmonics on battery life.
Differential Scanning Calorimeter
This device measures the thermal properties of materials used in batteries, particularly lithium-ion electrolytes, cathodes, and anodes. This capability is particularly useful in providing material data for input to the 3-D thermal abuse model developed by NREL's Energy Storage Team.
Extended-Volume Accelerating Rate Calorimeter
This device measures exothermal onset of reacting materials and batteries with exceptional sensitivity at various heating rates (up to 100°C/min). The battery heat output, temperature, and pressure can be measured while the battery is shorted, over-charged, over-discharged, or abused. The base unit can test small samples of 5 mg to laptop cells (.70" D x 2.56" H). The EV extension unit measures samples as large as HEV batteries (9.8" D x 19.68" H).
Electrochemical Impedance Spectroscopy (EIS) System
AC-impedance spectroscopy, an important and powerful method for studying surface processes, involves the measurement of the frequency dispersion of the impedance or admittance of a system. One advantage of measurements in the frequency domain is that the frequency dispersion of the complex impedance may be analyzed by modeling the interface as a collection of ideal circuit elements comprising a simple equivalent circuit. The various circuit elements can then be related to features of the system under study such as ionic conductivity, solution resistance, double layer capacitance, and Warburg diffusion.
Xenon Flash Thermal Conductivity Meter for Thin Films
Knowledge of the thermal characteristics of materials is critical to the material development and design of battery systems. The xenon flash thermal conductivity meter provides the thermal diffusivity, thermal conductivity, and heat capacity of battery materials, which feed into our multi-scale multi-dimensional life and thermal abuse models. The xenon flash thermal conductivity meter also allows for mapping the in-plane thermal conductivity of samples as large as 50 mm x 50 mm.
Thermal Conductivity Meter for Bulk Materials
The bulk thermal conductivity meter provides the in-plane thermal conductivity and thermal diffusivity of battery materials. It mimics the capabilities of the xenon flash thermal conductivity meter but is designed for larger and thicker sample sizes.