In 2018, professor Anshu Pandey of Bengaluru’s Indian Institute of Science (IISc) and his doctoral student Dev Kumar Thapa claimed in a research paper posted on the Cornell University’s arXiv repository that they had found superconducting behaviour at room temperature in a material prepared from gold and silver. As superconductivity at ambient temperature has eluded scientists for about a century, this discovery was groundbreaking, but was soon called into question.
A year later, The Hindu reports, the professor-student duo has answered the questions raised on their research, putting to rest all doubts and criticism.
Superconductivity is a Holy Grail in Physics. A material that, unlike ordinary metallic conductors commonly used in wires, offers zero resistance to the flow of electrons through it, is a superconductor. When current is passed through an ordinary conductor, such as copper, a part of it is lost to the surroundings in the form of heat energy generated due to the resistance offered to its flow by the material. Low resistance means more of the supplied power gets to its intended destination. With the use of superconductors, this loss can be cut down.
But until now, researchers could achieve superconductivity in most materials only in an extremely low-energy state, that is at frosty temperatures (a class of ceramic materials, cuprates, being an exception). In 1911, Dutch scientist Heike Onnes found superconductivity in Mercury at nearly -269º Celsius.
This all but rules them out for most practical uses. Maintaining such low temperatures are energy intensive and, thus, expensive. Achieving this state at low temperatures was also inconvenient as liquid helium is required in most cases and storing it is a problem because it boils at -269º C.
Some materials, such as a mercury-barium-calcium-copper-oxide, are known to have achieved superconductivity at a temperature little higher than that required for Mercury (-269º C). But in most cases, researchers had to increase pressure to achieve superconductivity, and the temperature at which superconductivity was achieved still remained much below room temperature.
This is why superconductivity at ambient temperature and pressure is revolutionary. And, if validated, it can have a lot of applications, such as these:
One, unlike conventional batteries, which degrade over time, semiconductors which have zero loss of energy can be used to store power. With more and more energy being produced from renewable sources, which needs to be stored, the power sector is looking for options which have minimum losses.
“The more appealing use of this technology is in power storage. Superconductors are the closest thing to perpetual motion that exist in nature. Current in a loop of superconducting cable will cycle forever. Loops like these could replace conventional chemical batteries, which are surprisingly inefficient. Lithium ion batteries have, on average, a charge/discharge efficiency of about 90 per cent. As energy production shifts more and more to renewables, energy storage is increasingly more important. A high-Tc superconductor would allow for efficient storage (and transport) of power. Batteries are also much easier to keep refrigerated if necessary, and there are greater efficiency gains to be had. Superconducting batteries are the real energy gain from high-Tc superconductors,” Stanford University’s Sean McLaughlin explains.
Two, trains running on magnetic levitation (maglev) has the potential to revolutionary transportation. But currently, the magnets used for the purpose of levitation are required to be cooled down to around -269º C in some cases, which not only increases complication but also the cost involved.
For example, the material used on Japan's magnetic levitation trains is required to stay at a temperature of around -270 C to remain in superconducting state, and this is achieved through liquid helium cooling. In China’s case, the material is cooled to around -180º C using liquid hydrogen. While helium is very expensive, use of hydrogen also adds significantly to the cost.
If superconductivity can be achieved at or around room temperature, the cost involved in cooling can be cut down, and complication reduced.
Three, currently, power transmission lines use ordinary conductors. The use of high-temperature superconductors can potentially transform the electricity grid. With current travelling long distances in a grid, a lot of it is lost in the form of heat energy. Although transmission of electricity through a grid takes place at high voltage, reducing the loss, there is some dissipation in the form of heat nonetheless. Losses can be minimised using high-temperature semiconductors.
Prakhar Gupta is a senior editor at Swarajya. He tweets @prakharkgupta.
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