Ee 361 Project Report
EE 361 PROJECT REPORT
INTRODUCTION:
When we first found out about the EE 361 project, we immediately thought that we should do this project, because we know that doing projects increases our practical knowledge tremendously. The aim of the project is to suspend a magnetic material using electromagnetic fields.
We first had to find a solution. As future engineers we thought that the solution should be intelligent and up-to-date, so we came up with the idea of using superconductors .
We are not familiar with calculations related to superconductivity at the moment but I am sure that we will learn a lot during the project. So in this preliminary report we will not be able to present you with any calculations but will give some brief information about superconductivity, its history and uses. Hopefully we will be able to give the calculations related to the project in the final report.
About Superconductivity
Superconductivity is the ability of certain materials to conduct electrical current with no resistance and extremely low losses. This ability to carry large amounts of current can be applied to electric power devices such as motors and generators, and to electricity transmission in power lines. For example, superconductors can carry as much as 100 times the amount of electricity of ordinary copper or aluminum wires of the same size.
Scientists had been intrigued with the concept of superconductivity since its discovery in the early 1900s, but the extreme low temperatures the phenomenon required was a barrier to practical and low-cost applications. This all changed in 1986, when a new class of ceramic superconductors was discovered that "superconducted" at higher temperatures. The science of high-temperature superconductivity (HTS) was born, and along with it came the prospect for an elegant technology that promises to "supercharge" the way energy is generated, delivered, and used.
History of Superconductivity
Early in the 20th century, Dutch physicist Heike Kamerlingh Onnes observed that mercury displayed no electrical resistance when cooled to very low temperatures. With this observation, the study of superconductivity was born.
For the next several decades, superconductors remained a scientific curiosity with few practical applications. Then in the 1960s a practical superconducting metal wire made of niobium and tin was developed. That wire, later made of a niobium and titanium alloy, became the basis for the first applications of superconductors.
The niobium and titanium alloy, still in use today, is among the materials called low-temperature superconductors. Low-temperature superconductors must be cooled to below 20 Kelvin (K) (-253o Celsius [C]) in order to become superconducting. They are now widely used in magnetic resonance imaging, or MRI, machines, and in the fields of high-energy physics and nuclear fusion. Additional commercial use has been limited largely by the high refrigeration costs associated with liquid helium, which is needed to cool the materials to such low temperatures.
The hope for low-cost superconductivity was ignited by two significant discoveries in the 1980s. In 1986, two IBM scientists in Zurich, Alex Müller and Georg Bednorz, discovered a new class of superconductors. Unlike the low-temperature superconductors, which were metallic or semimetallic, these new compounds were ceramic and were superconducting up to 35 K (-238oC). Müller and Bednorz won a Nobel Prize for their discovery. Then in 1987, Paul Chu at the University of Houston took the discovery one step further and announced a compound that became superconducting at 94 K (-179oC). This discovery was particularly significant because this compound could be cooled with cheap and readily available liquid nitrogen. These new materials were dubbed high-temperature superconductors.
Today’s high-temperature superconductors are moving out of the laboratory and into the marketplace. Bismuth-based compounds are being fashioned into superconducting wires and coils, which are essential to electric power uses. Thallium- and yttrium-based compounds are being formed into the thin films used in electronic devices. And, as superconductivity moves into the 21st century, products such as superconducting motors, generators, fault-current limiters, energy storage systems, and power cables promise to change forever the way electricity is generated, delivered, and used.
Superconductor Uses
Transmission lines that carry power without resistance, medical diagnostic tools that eliminate the need for surgery, "levitating" trains that speed along the tracks—these are not visions of the future, but examples of what superconductors are doing today.
Superconductors conduct electricity without losing energy to electrical resistance, as most conductors do. Certain materials become superconductors when they are cooled to very low temperatures. Low-temperature superconductors exhibit superconductivity at temperatures near 0 Kelvin (K) (or -273o Celsius [C]). Recently discovered high-temperature superconductors (HTS) can function at temperatures as high as 140 K (-133oC). This is an exciting discovery because these high-temperature superconductors can be cooled more economically and efficiently than can low-temperature superconductors.
Superconductors also repel surrounding magnetic fields. This phenomenon is demonstrated when we levitate a magnet above a cooled superconductor, and it is the force at work in Japan’s famous Maglev train.
Superconductors help us use energy more efficiently and reduce the cost of electricity production, storage, transmission, and use, and the costs of transportation and medical equipment. Some current uses, and some that hold the most promise for the near future, are these:
Power transmission cables that carry current without energy losses will increase the capacity of the transmission system, saving money, space, and energy. Prototype power transmission cables have been developed and are being tested by teams led by Pirelli Cable Company and Southwire Company .
Motors made with superconducting wire will be smaller and more efficient. A 1,000-horsepower motor has been constructed and is undergoing testing by an SPI team led by Rockwell Automation/Reliance Electric Company.
Generators will use superconducting wire in place of iron magnets, making them smaller and lighter. New generators also may get more power from less fuel. An SPI team led by General Electric has developed a design for a 100-megavolt-ampere generator.
Current controllers (i.e., fault-current limiters) help utilities deliver reliable power to their customers. HTS fault-current limiters detect abnormally high current in the utility grid (caused by lightning strikes or downed utility poles, for example). They then reduce the fault current so the system equipment can handle it. An SPI team led by General Atomics recently produced a successful HTS fault-current limiter that will soon be ready to market.
Energy storage in flywheel systems will ensure the quality and reliability of the power transmitted to utility customers. In addition, energy storage provides utilities with cost savings by allowing them to store energy when the demand for electricity is low and generating the power is cheap. This stored energy is then dispensed when demand is high and power production is more expensive.
Magnetic resonance imaging (MRI) machines enhance medical diagnostics by imaging internal organs—often eliminating the need for invasive surgeries. MRIs, which currently are made with low-temperature superconductors, will be smaller and less expensive when made with HTS.
Maglev trains seem to float on air as a result of using superconducting magnets. These trains have been under development in Japan for two decades; the newest prototype may exceed 547 kilometers (340 miles) per hour.
These are only a few of the many possible uses for superconductors. Research and development of HTS may still yield many more uses for materials that can carry electricity without resistance. And as today’s new technologies move into the marketplace, they will have a great effect on the way we generate, deliver, and use electricity, and on the medical and transportation technologies of tomorrow.