Early-Stage Research & Development
This is the July 2017 issue of the Transportation and Hydrogen Newsletter.
July 10, 2017
Anisotropic Thermal Measurement Study Points the Way to Better Electric Vehicle Motor Design
A recently completed NREL study of the anisotropic thermal conductivity of packed copper wire used in electric-drive vehicle motor applications provides a baseline for assessment of new materials and winding structures. Successful thermal management in copper-wound electric motors makes it possible to maximize operational efficiency and longevity, allowing manufacturers to meet consumer demand for high-performance, reliable, and long-lasting electric vehicles.
NREL Pioneers Ultrathin Coating Application to Improve Performance of Lithium-Ion Batteries
NREL researchers collaborated with the University of Colorado to create a breakthrough method for applying ultrathin coatings directly to electrodes and battery materials. This surface modification technique—using atomic layer deposition and molecular layer deposition—allows new high-capacity, high-density materials, such as silicon, to be stabilized, resulting in lighter-weight batteries with improved battery cycling, enhanced lifespan, and higher abuse tolerance. This discovery opens the door for future studies in electro-chemo-mechanics to improve the overall charge capacity and stability of lithium-ion batteries.
Future Standard for Pyrolysis Bio-Oils Based on NREL-Developed Procedures
Pyrolysis bio-oil R&D currently lacks common characterization techniques and quality metrics, which presents a challenge to realizing its potential as an alternative to petroleum. NREL researchers, along with partners at other national labs, are advancing one solution: standardization of procedures through ASTM International Committee E48. The standard will be based on recently developed laboratory analytical procedures for determining bio-oil composition and quality including quantifying carbonyl compounds and acids by titration, determining hydroxyl functional groups with nuclear magnetic resonance, and quantifying semi-volatile oxygenated compounds by gas chromatography/mass spectrometry.
New Class of Thermal Interface Materials Delivers Ultralow Thermal Resistance for Compact Electronics
As consumers demand ever smaller, more efficient electric vehicles and electronic devices, the challenge is to find new ways to diffuse the heat generated within these compact systems. NREL researchers have characterized a new class of thermal interface materials (TIMs) involving the chemical integration of boron nitride nanosheets, soft organic linkers, and a copper matrix. Findings indicate potential for thermal resistance one-third lower than any other state-of-the-art TIM, which will be critical in creating more compact, high-power-density electronic components for EVs.
Life Balancing Offers New Way to Improve Battery Pack Longevity and Affordability
Individual cells within battery packs can weaken and lose their charging capacity over time, thus shortening the overall life of a battery. Life balancing technology has been developed that takes a variable amount of current from each cell or small groups of cells and converts it to current for the low voltage system that supplies vehicle 12V auxiliary loads. A battery with this technology can maximize the usable energy and power of the pack by reducing capacity degradation, resulting in more uniform cell capacities. This could provide more usable energy to a vehicle for a longer period of time, potentially at a lower cost.
Analysis to Shape Direction of Future Electric Bus Grid Integration Research
Through its partnership with Prospect Silicon Valley and the Santa Clara Valley Transportation Authority (VTA) in California on an Advanced Transit Bus Vehicle Grid Integration Project, NREL will conduct performance evaluations and associated analytics to help VTA optimize the use of electric buses while also pinpointing areas in need of further development in the realm of vehicle grid integration. NREL will use innovative analysis tools—Fleet DNA, Future Automotive Systems Technology Simulator (FASTSim), and Drive Cycle Rapid Investigation, Visualization, and Evaluation (DRIVE)—to determine the direction for subsequent research.