CNT bundle material for flywheels 40 times better than batteries

In the lab, China has small quantities of carbon nanotube bundles 20 times stronger than Kevlar. These are ultralong (several centimeters) carbon nanotube fibers have been made into stronger bundles. The tensile strength of CNTBs (Carbon nanotube bundles) is at least 9–45 times that of other materials. If a more rigorous engineering definition is used, the tensile strength of macroscale CNTBs is still 5–24 times that of any other types of engineering fiber, indicating the extraordinary advantages of ultralong Carbon nanotubes in fabricating superstrong fibers.

A synchronous tightening and relaxing (STR) strategy improves the alignment of the carbon nanotubes to increase the strength.

Tsinghua University researchers are trying to get the fiber into mass production for use in military or other areas.

The material would be very useful for sports equipment, ballistic armor, aeronautics, astronautics and even space elevator.

Ultimate Flywheels with twenty times the energy density 10,000 Watt hours per kilogram

If the material could be used in flywheels for energy storage the energy density would 40 times more than lithium-ion batteries. Electric cars with carbon nanotube bundle flywheels would have a range of 10,000 miles.

Super carbon nanotube bundle flywheels would likely first be used to provide bursts of power for railguns and combat lasers.

The fiber would need to be several kilometers long to make a useful energy storage device.

Flywheels were used in formula one races to provide extra power on turns and for overtaking other race cars. There was some use in 2008 to 2010 and then they were banned in 2011.

Flywheels have been shown to have excellent aging characteristics, with cycle lifetimes in excess of 1,000,000 cycles, regardless of charge rate and depth of discharge.

Superconducting carbon nanotube flywheels

Boeing and Japanese companies have been working on superconducting bearing flywheels for several years. In 2012, Boeing flywheel tip speed was 800 m/sec. World record on small test rotor in 2012 was about 1,405 m/sec. FW tip speed is limited by material properties.

The Boeing plan was trying to develop new materials that would allow speed to reach 3,000 m/sec. The carbon nanotube bundles would allow tip speeds that were twenty or forty times faster.

Boeing has the vision of combining advanced fiber technology and superconducting bearings to enable the development of a low-cost, extremely high energy-density, highefficiency flywheel energy-storage system. The superconducting bearings enable high efficiency and high spin rates. The new proprietary fiber enables high rotor tip speeds resulting in high energy density, with a projected cost of $100/kWh for the flywheel system at utility scale and large-rate factory production. The prototype flywheel will be small enough (7 kWh/5kW) to facilitate rapid development with a design that is easily scalable to a utility-size unit (~100 kWh) and amenable to factory production to achieve low cost. The vision for commercial production is that individual 100-kWh flywheels will be arrayed in a transportable container with a total storage of 2 MWh for utility applications. The Boeing vision is with current weaker materials.

Full strength utility flywheels with the new materials could provide individual flywheels with tens of megawatt hours in power.



Power-thru uses magnetic levitation with no bearings.

All-composite rotors — versus steel hub and composite overlay — offer lighter weight and reportedly improve safety. The lighter weight also improves energy storage, as POWERTHRU explains: “Kinetic energy is roughly equal to mass times velocity squared. So doubling mass doubles energy storage, but doubling the rotational speed quadruples energy storage.” Thus, today’s all-composite rotors allow faster rotational speed (40,000 to 60,000 rpm), which increases short-term energy storage capacity.