Regenerative braking systems with torsional springs made of carbon nanotube yarn

[摘要] The demonstration of large stroke, high energy density and high power density torsional springs based on carbon nanotube (CNT) yarns is reported, as well as their application as an energy-storing actuator for regenerative braking systems. Originally untwisted CNT yarn is cyclically loaded and unloaded in torsion, with the maximum rotation angle increasing until failure. The maximum extractable energy density is measured to be as high as 6.13 kJ/kg. The tests also reveal structural reorganization and hysteresis in the torsional loading curves. A regenerative braking system is built to capture the kinetic energy of a wheel and store it as elastic energy in twisted CNT yarns. When the yam's twist is released, the stored energy reaccelerates the wheel. The measured energy and mean power densities of the CNT yarns in the simple regenerative braking system are up to 4.69 kJ/kg and 1.21 kW/kg, respectively. A slightly lower energy density of up to 1.23 kJ/kg and a 0.29 kW/kg mean power density are measured for the CNT yarns in a more complex system that mimics a unidirectional rotating regenerative braking mechanism. The lower energy densities for CNT yarns in the regenerative braking systems as compared with the yarns themselves reflect the frictional losses of the regenerative systems.

[发布机构] Mechanical and Industrial Engineering Department, Northeastern University, Boston; MA; 02115, United States^1;College of Engineering and Physical Sciences, University of New Hampshire, Durham; NH; 03824-2222, United States^2;Nanocomp Technologies Inc., Merrimack; NH; 03054, United States^3

[效力级别] 能源学

[关键词] Carbon nanotube yarns;High energy densities;High power density;Regenerative braking systems;Regenerative system;Structural reorganization;Torsional loadings;Torsional springs