Energy efficiency for future Electric vehicles

Introduction

Achieving high energy efficiency is a primary objective for future Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs). This is a goal which is closely intertwined with thermal efficiency and design considerations. Future research demands deeper exploration into lubricant behavior under applied electric fields and dynamic EV/HEV conditions. Additionally, understanding the impacts of lubricants on wear and corrosion of EV/HEV components is essential. Understanding this impact of electric and magnetic fields on lubrication systems in electric vehicles is vital for scientific and industrial progress. Research should focus on minimizing electric fields, enhancing bearing insulation, and controlling lubricant conductivity to prevent issues like current leakage or static charge build-up. Additionally, developing self-lubricating materials and studying emulsion formation are key areas for future exploration. Collaboration between industry and academia is essential to address these challenges effectively.

Lubricant design

Aiming for thermal and energy-efficient EV) and HEV lubricants involves various considerations. Such as using low-viscosity fluids which reduces film thickness, although this may lead to higher operating temperatures and reduced bearing fatigue life. Designing lubricants with longer-chain organic molecules can enhance heat transfer through intermolecular collisions. Additives like dialkyldithiophosphates, though effective should be avoided in future formulations due to their potential harm to components. Understanding grease lubrication mechanisms and developing predictive tools for performance assessment are crucial, especially as greases dominate in EV/HEV applications. New grease formulations must withstand high temperature fluctuations and high shear, with an increasing demand for eco-friendly and biodegradable options. Specific properties such as grease lifespan, water resistance, load-bearing capacity, corrosion resistance, and performance at low temperatures are paramount for EV/HEV greases. Improved grease formulations should reduce torque while maintaining electrical and mechanical component properties. Polyurea-based greases may see increased demand for their seal-for-life function, while lithium-based greases face uncertainties in future EVs.

System design

Around 57% of an EV’s energy is consumed by friction, offering significant opportunities for energy reduction across various vehicle systems. Lubricants will be pivotal in minimizing Noise, Vibration, and Harshness levels as EVs prioritize torque transfer. Research focus will encompass high-speed rotor dynamics, control systems, and lubrication for high-speed air compressors. Future EVs may adopt spray cooling methods, utilizing runoff for bearing lubrication. Lower hydrodynamic loads on journal bearings necessitate a shift in the lubricant’s role from load bearing to torque transfer. Addressing excessive oil aeration and enhancing lubrication system durability are crucial for mitigating bearing fatigue. Transmission fluids must excel in heat transfer to cool the motor, while advanced coatings counter surface adhesion and thin film effects from low-viscosity lubricants. Extended lubricant drain intervals require smart oil monitoring systems and high-quality sensors for maintenance. Advanced cooling designs, like direct pin-fin-based liquid cooling, are vital for enhancing component reliability in future EV designs.

Reference

[1] Chen, Y., Jha, S., Raut, A., Zhang, W. and Liang, H., 2020. Performance characteristics of lubricants in electric and hybrid vehicles: a review of current and future needs. Frontiers in Mechanical Engineering, 6, p.571464.

[2] https://www.emobilitysimplified.com/2019/10/what-is-e-mobility-all-you-need-to-know.html

[3] https://www.q8oils.com/automotive/hybrid-electrical-vehicles-lubrication/

[4] https://www.tilleydistribution.com/electric-vehicles-impact-on-lubricant-demand/