# What is Superconducivity?

Every year the United States produces about 4 trillion kilowatt hours of electricity. Unfortunately about 10% of this will be lost in transmission according to the US Office of Electricity Delivery and Energy Reliability (http://www.oe.energy.gov.) The same way your stove top gets hot when electricity is passed through it’s coils, electrical transmission lines heat up and lose energy energy as electricity flows through them. Now you might think that a 10% loss doesn’t sound so bad, but at \$.10 per kilowatt hour this amounts to an equivalent yearly loss of \$40 billion! Wouldn’t it be nice if scientists and engineers could discover a way of transmitting electricity without any loss? Wouldn’t it be nice to save US citizens \$40 billion per year? As a matter of fact, a way of transmitting electricity without any losses has been well known for almost 100 years.

The History of Superconductivity

In 1911, a Dutch physicist named Kamerlingh Onnes was studying the resistivity of different materials at very low temperatures. Resistivity1 is a measure of how difficult it is for electricity to flow through something. The higher the resistivity, the greater the amount of power which will be lost. At the time, it was well known that the resistivity of metals is much smaller at lower temperatures than at room temperature. Onnes had just discovered a way to produce temperatures as cold as 1 Kelvin (-458 degrees Fahrenheit) using liquid helium and he was excited to see just how low the resistivity of different metals could get.

Onnes was a professor at the University of Lieden and had assigned one of his graduate students to the task of studying the resistivity of different metals at these low temperatures. While testing various metals his student noticed that the resistivity of mercury dropped to zero when its temperature was below 4.2 Kelvin (-452 degrees F.) Onnes assumed that his student had made an error and decided to try the experiment himself. Much to his astonishment, Onnes realized his grad student had been correct and that mercury indeed had no electrical resistance below this critical temperature. Mercury was therefore the first material discovered to exhibit superconducitivity2 and soon other metals were discovered to be superconductors. Lead was found to be a superconductor below 7 Kelvin in 1913 and soon after it was discovered that niobium superconducts below 9.3 Kelvin. Kamerlingh won the Nobel Prize in 1913.

In subsequent years, superconductors with much higher transition temperatures have been found. In 1987, yttrium-barium-copper-oxide (nicknamed Y.B.C.O.) was discovered to superconduct below 93 Kelvin. YBCO was the first superconductor discovered to have a transition temperature which could be reached with liquid nitrogen which is about ten times cheaper than liquid helium. Then in 2006 another superconductor, mercury-thallium-barium-calicium-copper-oxide, was discovered to superconduct below 138 Kelvin (-211 degrees F.) To date this is the highest temperature superconductor at ambient pressure.

By now the reason why we have not implemented superconductors for electrical transmission should be obvious. We would need to keep our powerlines at more than 200 degrees below zero and the cost of doing so would be far greater than the \$40 billion of electricity lost in transmission. This is why superconductivity one of the hottest topics in the physics world today. Scientists are working to try to find ways to increase the temperature at which superconductivity can occur. If we can find a superconducting material which works at room temperature, we will have an immediate way to reduce our nation’s energy consumption and save billions of dollars in the process.

Still not convinced that superconductors are one of the most important technologies of the future? Read on…

Other Valuable Uses for Superconductor Technology

Computers

Superconducting electronics can allow computers to run faster. If you know anything about overclocking computers, you know that one of the biggest issues you face is heating. As you push the electronics in a computer to higher and higher frequencies the heat produced by overclocked components also gets higher and higher. Where does all that heat come from? The same place heat from your electric stove top comes from: resistance. As you know from reading above, superconductors have no resistance and therefore don’t produce any heat when electricity is passed through them. For this reason superconducting electronics can be pushed to much higher frequencies than present electronics allowing for faster computing.

Medicine

Most people don’t realize that superconductors are responsible for many medical imaging technologies we have available today. The most powerful electromagnets are made from superconducting wires. Superconducting magnets are found in MRI’s. With the developement of superconductors with higher operating temperatures MRI’s and other medical imagining techniques will not only be cheaper, but will allow imaging to be done with stronger magnetic fields. The resolution of MRI’s gets better as the magnetic fields they use become stronger. I don’t know about you, but I would much rather get an ultra high resolution MRI than having invasive and frightening exploratory surgery if possible.

Space Exploration

Suppose your building a space ship that’s going to be making a long journey, perhaps to Pluto or even a nearby star such as Alpha Centauri. Even flying to Pluto would take years and you’re going to need power for all those years! The average intensity of sunlight at Pluto’s orbit is about 1/1600 as intense as it is at Earth’s distance from the sun. So you can forget about using solar panels for any manned space exploration unless you can use your energy very very efficiently. The other option is to use batteries, but again you have limited space so you need high efficency. This is where superconductors again save the day. Since superconductors have no power loss, they can operate with far less energy consumption than current electronics. Space utilizations also have an advantage that deep space is already about 3 Kelvin and so we don’t even need worry about developing room temperature superconductors. We simply need to start building superconducting electronics.

Notes From Above:

1) Resistivity is the the resistance per unit length, measured in ohms per meter or sometimes ohms per centimeter. Resistivity is a more useful term because unlike resistance, resistivity doesn’t depend on the size of the supercondutor.

2) Resistivity is a measure of how hard it is for electricity to flow through some, conductivity on the other hand is a measure of how easy it is for electricity to flow through something. Superconductors got their name because they are perfect conductors.