New Superconductivity Technology: Explore Superconductivity
Discover new superconductivity technology in your life, from renewable energy and land mine detection to kaolin clay and the LHC at The Emergent Universe, an online interactive science museum about emergence.
Where in Your Life?
Superconductors are materials in which electricity can flow without energy loss. In 1987, materials were discovered that could superconduct at the "high" temperature of liquid nitrogen (-196º C), re-igniting excitement over superconductors' technological promise.
Come on in and see for yourself how superconductors are impacting our lives.
Cell phone tower filters
The next time you make a call from your cell phone, you could be using a superconductor. Filters in the cell-phone towers that process your calls block out signals that aren’t in your carrier’s designated frequency range. Filtering with high selectivity is important for call quality, especially with the number of active cell phones, which was 5 billion in 2010, increasing by 25% annually. But as conventional filters are made more selective, the signal loss due to resistance gets worse. Because a thin film of high-temperature superconducting material has essentially no resistance, filters made from such films can simultaneously be more selective and handle weaker incoming signals, thus improving call quality and reducing dropped calls. The first superconducting filters were installed in commercial cell-phone towers in 1997, and by 2010 their numbers had grown to 10,000 units.
When the human body is placed in a magnetic field, the response of hydrogen in the body’s water molecules to radio frequencies depends upon the surrounding tissue type. This tissue-type-dependent response is the basis of MRI (Magnetic Resonance Imaging) technology, the advent of which has reduced the need for exploratory surgeries by a factor of two. But obtaining good MRI images requires generating high-strength magnetic fields. Maintaining the currents needed to create such high fields with conventional electromagnets would require prohibitive amounts of electric power. Superconducting magnets, which are made from closed loops of superconducting wire in which current can flow indefinitely without adding energy, eliminate this power cost. Liquid-helium cooled superconducting magnets have remained the most commonly used type of magnet in MRIs since the commercial introduction of these instruments in 1980.
Magnetoencephalography and Magnetocardiography
The neurons in your brain generate tiny magnetic fields. These fields are over a billion times weaker than even the earth’s magnetic field, yet superconducting devices called SQUIDS can measure them in real time. In MEG (for magnetoencephalography), an array of SQUIDs generates a spatial map of measured brain activity and follows it over time. MEG is providing new insights into brain disorders from autism to PTSD, and, when combined with MRI brain images, it helps to locate the brain areas responsible for epileptic fits and to find the least damaging surgical routes for tumor removal. SQUIDs can also detect magnetic signals from the heart, a technique called MCG (for magnetocardiography). As of 2010, MEG and MCG machines are both commercially available, and MEG is becoming more widely adopted in clinical medicine.
Electrically-powered, floating “MagLev” trains, which are kept aloft and propelled by magnets, have been around since 1972. Although there are both superconducting and conventional magnet MagLev designs, the superconducting designs are lighter, faster, and more energy efficient: Japanese superconducting MagLev trains have held the world train-speed record since 1979 (through at least 2010), and in 2003 attained a speed of 581 km/h (361 mph). The superconducting designs are also self-correcting. For example, if the train magnets were to get too close to the track, the repulsion between the magnets and the track would increase, pushing them back apart. Unfortunately, commercialization has been limited, largely by the cost of the specialized track. Nevertheless, a commercial superconducting MagLev line between Osaka and Tokyo is planned, with the Osaka-Nagoya segment to open in 2027.
Particle accelerator magnets
In order to recreate the trillion-degree temperatures and thus the quark-gluon plasma that followed the big bang, lead ions that are smashed into each other at CERN’s Large Hadron Collider (LHC) must be moving at nearly the speed of light. But the faster these ions are moving, the harder it is to steer them around the accelerator, so the LHC uses superconducting magnets with field strengths above 8 tesla for this task. Why superconducting? Because at about 2 tesla, iron-based magnets max out, and higher field conventional electromagnets become impractical due to their resistance losses. These losses can be avoided by constructing the magnet from loops of superconducting wire, within which currents can persist indefinitely. Superconducting magnets have been used in particle accelerators since 1983, when they were used in Fermilab’s Tevatron accelerator.
Transition-edge sensors sensitive gamma ray detectors
The Infamous Kitty Litter Problem
Conventional radiation detectors can’t tell the difference between gamma rays emitted from uranium-235, which can be used to make nuclear weapons, and those from naturally occurring radon-226, which is found in cat litter. Hence, when cargos are scanned for nuclear weapons materials at border crossings, cat litter shipments generate false alarms. Superconductors could eliminate this problem. When a superconductor at the midpoint temperature of its transition to the normal state absorbs the energy of a gamma ray, its temperature increases, reducing the number of superconducting electrons and increasing its resistance. Measuring this resistance increase tells us the energy of the incoming gamma rays very precisely, thus distinguishing those from uranium-235 and from radon-226. As of 2009, such superconducting sensors were under development for use by the nuclear security industry. They are also being used extensively by cosmologists for studying cosmic background radiation and in the search for dark matter.
SQUID detectors for locating unexploded ordnance
There are millions of unexploded bombs, mines and other munitions worldwide. This unexploded ordnance (UXO) poses an enormous threat, killing or injuring an estimated 40,000 people annually. Removing UXOs requires finding them, a tedious process that involves scanning the ground with handheld “gradiometers.” Flying airborne gradiometers above existing vegetation could speed this process, but conventional gradiometers, which detect distortions of the earth’s magnetic field caused by steel objects, can only detect UXOs at close range. They also have difficulty distinguishing UXOs from other steel objects. Constructing gradiometers from SQUIDS – superconducting devices that can measure tiny magnetic fields – could increase both the range and accuracy of these devices, enabling airborne use while reducing false positives. Although there are still technical challenges as of 2010, airborne SQUID gradiometers for UXO detection are being pursued vigorously at the R&D level.
Geo-prospecting SQUID detectors
To find new ore deposits, mining companies send magnetic pulses into the ground and evaluate the returning magnetic field over time. Metal ores can be detected because their magnetic response decays more slowly than those of other rocks and soils, called the “overburden.” Because conventional survey devices detect only how quickly the returning magnetic field changes, the rapidly changing field from the overburden creates a big signal that can mask the ore’s smaller signal, preventing deeply buried ore from being detected. In contrast, SQUIDs– superconducting devices that can detect tiny magnetic fields – measure the magnetic field directly, and thus more easily distinguish the ore from the overburden. Portable, SQUID sensors constructed from HTS have detected billions of dollars worth of previously undiscovered silver and nickel ore deposits since they became commercially available in 2003.
Nondestructive evaluation of welds/circuit chips (SQUID)
New silicon chip designs, which involve multiple circuit layers surrounded by extremely dense wiring, defeat conventional quality control methods. SQUID microscopes – superconducting devices that can detect tiny magnetic fields – are coming to the rescue. When a tiny current passed through the chip encounters a defect, it creates an undesired “fault” current. By detecting associated changes in the magnetic field, a SQUID microscope can locate the position of the fault current, thus enabling manufacturers to identify the source of the failure. SQUID microscopes for such non-destructive evaluation of silicon chips are commercially available. These microscopes have also been shown to be useful for non-destructive evaluation of deeply buried cracks and hidden corrosion in models of aluminum airplane parts, but as of 2010 there had not yet been commercial demonstrations of this application.
Industrial magnetic separators for kaolin clay
The production of Kaolin clay is a 3 billion dollar worldwide industry. This bright white clay is used to make paper, porcelain and cosmetics. Many lower-grade Kaolin deposits contain tiny, magnetic, iron-ore particles that discolor the clay and must be removed by magnetic separation. The Kaolin industry has used magnetic separators that rely on low temperature superconducting magnets since 1986. These superconducting separators use as little as 10% of the power of conventional separators, thus lowering costs. They can also produce magnetic fields that are 2.5 times stronger, thus enabling either faster throughputs or the separation of smaller, more weakly magnetic, particles.
The rapid increase in electricity use worldwide – it has doubled in 25 years — is causing problems in dense urban areas where space to add new power lines is scarce. Using liquid-nitrogen-cooled high-temperature superconductor (HTS) cables can help ease this congestion, because HTS cables are very compact, carrying up to10 times the power as the same size copper cables. HTS cables also produce no external electromagnetic fields or heat. As of 2010, numerous successful alternating current (AC) HTS demonstration cables were in place in working power grids, and commercial utility use was beginning. Also, high capacity direct current (DC) HTS cables, which can carry enough power for 5 million homes in a 3ft-wide pipe, are slated for use in the Korean Jeju Smartgrid project and in the U.S. Tres Amigas project (which will connect the 3 isolated US power grids).
Superconducting generators in wind turbines
Plans for slowing global warming rely heavily on green energy sources. For example, the European Union projects increasing wind power generation by 150 times its 2010 capacity, with much of this via offshore wind farms. The high cost of offshore tower structures makes it important to increase the power output per tower to 10MW (enough to power 3000 homes), which is twice the highest current capacities. Limitations on turbine power come from (1) generator weight and (2) poor reliability of drive-train gear-boxes. The 100-fold current carrying enhancement of high temperature superconducting (HTS) wire over copper wire enables high power generation at half the weight, even at the low speeds of wind turbine blades, thus eliminating the need for gears. As of 2010, HTS generator technology had already been demonstrated (in a 36.5 MW ship motor), and prototype 10MW wind turbines were expected within a few years.
Superconducting fault current limiters/and FCL-HTS cable
The Northeast Blackout of 2003, which caused an estimated $6 billion dollar loss, was initiated in part by power transmission lines sagging into trees and short-circuiting. Such short-circuits produce large current surges, known as fault currents, that can cause extensive damage. Because superconductors switch into their normal, resistive state when the current exceeds a critical value, they make ideal switches for fault-current-limiting devices. Specifically, when the fault current flowing through a superconducting wire exceeds a critical value, the wire’s resistance will increase, blocking the flow of current and directing it instead through a current limiting device. As of 2011, a number of different superconducting fault-current-limiter designs were operating in in-grid demonstration projects worldwide. These devices are advantageous because they trip and reset automatically and introduce minimal power losses during normal operation.
On hot summer afternoons, idling power plants are brought online to meet increased demands. Although such demands occur only 5% of the time, meeting them can require 40% more power generating capacity, usually supplied by high-emission, low-efficiency, natural gas plants. Daily energy storage could help reduce the need for these plants. It would also support the adoption of intermittent renewable power sources like solar and wind. One possible zero-emission energy-storage technology, flywheels, store electrical energy by converting it to rotational energy. By using high temperature superconducting (HTS) bearings to levitate the rotating flywheel element, losses of stored energy can be reduced from 50% to 2% per day, opening the possibility that HTS flywheels could be used for daily energy storage. An in-grid development and demonstration project for a utility-scale HTS flywheel system was funded in 2010.
Naval applications: SC degaussing system/SC Electric Motors
Sea mines account for more naval ship casualties than all other causes combined. And this threat is increasing further as naval strategies focus on shallow coastal waters. Advanced degaussing systems, which mask the ship’s magnetic field by passing electricity through cables on the ship’s perimeter, can protect ships from magnetically triggered mines. But today’s copper-cable degaussing systems are extremely heavy. Replacing the copper cable with superconducting (HTS) cable can reduce the weight by a factor of 5, potentially saving over 100 tons. The first such HTS degaussing system was successfully tested aboard the USS Higgins in 2010. As another weight saving measure, ships’ copper-coil-based propulsion motors can be replaced by HTS-wire-based motors that are 3 times smaller and lighter. Such HTS motors, two of which were successfully land-tested by 2010, are more fuel efficient and would reduce emissions.