Welcome again to JJNN for Monday June 16th, 2008. Today I want to talk about a new electric car prototype that was produced in Japan.
The original article about the car is here. The company Sumitomo produced an electric car prototype with a secret under the hood. You may think that the secret is a new type of battery, but actually the battery is just one of the same old lead based storage batteries we use now. The secret is actually much more interesting. The engine of the car was made with coils of superconducting wires.
I want to go over superconductivity just a little bit before I got back to talking about the car. Superconductivity happens in certain special metals when they are cooled to extremely low temperatures. When the metal is cooled its resistance goes to zero, and when the resistance finally reaches zero it is than superconducting. The superconducting metal shows an interesting effect called that Meissner effect in which the metal actually repels magnetic fields. This can be seen in the famous experiments with a magnet levitating over a cooled superconductor. The Meissner effect has nothing to do with these cars, so I will get back on topic. The important thing to remember is that superconductors have basically 0 resistance at low temperatures.
Now onto the car. The picture of the car can be seen above. There is something you should be wondering about the car. It has superconducting parts, right? That means that parts of the car have to be cooled to extremely low temperatures. So how do you think they do this? Well it's not by going to a corner store and getting a bag of ice. The car actually has a 4 liter tank that is for liquid nitrogen. That much liquid nitrogen will keep the superconducting wires, which are made from an bismuth amalgam, cool for about 2 hours. In case of accidents passengers don't have to worry about the gas tank exploding, but now they have to worry about the new problem, low temperature burns.
So, you may be wondering why this company decided make their electric engine with superconducting wires. It's not the official answer, but probably "Because a superconducting motor is just damn cool." is up there somewhere on the list. The real reason the company gives is the fact that a large current can run in superconducting wires. A large current in an electric engine leads to a huge torque from the engine. The other reason given is that a lower conductivity in an electric engine leads to a higher gas milage. I don't think that gas milage is the right word, but I don't know what to say for electric cars.
This may be great for a prototype, but I wonder if we will be seeing a lot of superconducting vehicles in the future. The company's plan for the next ten years is to improve on the technology and get a superconducting bus, with a cooling tank big enough for a day of driving, on the road. Also, if a version of a fuel-celled car with liquid hydrogen ever gets invented, the engine can get its cooling from that liquid hydrogen instead of the liquid nitrogen that the prototype is using.
I don't know what I think about this. It seems a little bit too ahead of its time. The tank and the coolant together must weigh a lot. This weight along with the weight of the batteries and the engine can not make this car very practical. But, if they put more time and money into the project it may end up being a good idea. We shall see some time.
Any way, it is now time for the word of the day. Today's word is 液体窒素(えきたいちっそ). It is pronounced ekitai-chisso and means liquid nitrogen. Liquid nitrogen brings me back my undergrad days in the basement of the physics department filling up the nitrogen dewars on detectors. I had to do that every day, and even to this day I don't like liquid nitrogen.
That's it for today. See you next time at JJNN.