Back in 2008 when I started podcasting, I discussed a new story about Sumitomo releasing a prototype of an electric car using a superconducting motor. This was hailed as a world first. The benefit of using such a motor was to provide greater torque from a lower voltage. Sumitomo had plans to test it in larger vehicles such as buses and trucks. At the time Sumitomo had built a prototype using a Toyota Crown to prove the technology could work. I thought it would be good to check in and see what has happened over the past ten years.
The idea behind a superconductor is that it uses less power to drive a motor. An electric motor – just like a traditional internal combustion engine – loses some of its power in the creation of movement. For electric cars, it is slightly worse – the conducting of the energy from the battery to the motor also loses some of the available power to drive the motor which in turn rotates the wheels. Superconducting provides almost lossless resistance which means that more of the charge is sent to the motor.
Sumitomo’s research was based around removing the copper coils from inside the motor – copper heats up and when it does, it has a limit to the size of the current it can carry and as such this limits the torque generated by the motor. Torque is the ability to power the driving wheels. Sumitomo’s superconducting motor can carry a much higher current and therefore can produce much higher torque using different conductive materials.
Their first development motor produced a mere 30Kw and 120Nm of torque and they looked to upsize the motor to provide much higher figures. The Toyota it was fitted to certainly proved a point and they are still developing the concept further. In 2012 they showed a bus prototype that had a 365Kw motor, however it had to be cooled by liquid nitrogen – a byproduct of the technology. Some of the power was lost in managing the heat exchanger though. The heat would have damaged the copper wires of a typical electric motor.
The company is still developing the motors and expect to have something on the market within about 5 years and it will be interesting to see if they have managed to deal with the high temperatures that are being produced although recent reports that I read suggested that the first commercially available motors would be fitted to heavy trucks and other non passenger vehicles. I suspect that in reality we will never see a production car with this technology as it seems to be a dangerous combination for personal transportation.