Superconductors are substances that exhibit zero electrical resistance, allowing for the uninterrupted flow of electric current and eliminating energy loss. This phenomena is of a quantum origin and occurs at temperatures usually below -150°C. However, the interest in these materials extends much beyond mere scientific curiosity. Superconducting technology plays a crucial role in applications that have significant social implications, such as high-resolution medical imaging and drug research spectroscopy. It has a crucial function in major scientific investigations, such as the Large Hadron Collider (LHC) at CERN. As we move towards achieving more sustainability, the potential of superconductors to have a substantial influence on clean energy, zero-emission mobility, and quantum computing is becoming more attractive.
Superconductors, Healthcare and Biomedical Research
Superconductivity in Medical Imaging
Superconductivity has its primary commercial application in high-field magnets, which are essential components of medical Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) spectroscopy. This technology, based on magnetic resonance, provides detailed insights into the molecular structures and chemical characteristics of substances, revolutionizing medical diagnostics and research. MRI, since its development in the 1970s, has become a leading method for generating detailed images of organs and tissues. With over 40,000 superconducting MRI scanners in hospitals worldwide, the MRI technology market is expected to reach $11.7 billion by 2025. The resolution of these systems, determined by their magnetic field strength (measured in Tesla), varies, with many systems operating between 1.5 to 3 terabytes and some reaching 7 terabytes or more. The ongoing advancements in superconductor technology aim to achieve magnetic field strengths of up to 20T, potentially unlocking significant scientific breakthroughs in understanding the human brain and improving diagnosis and treatment of neurological and mental disorders.
NMR spectroscopy is crucial for understanding the structure, dynamics, and function of complex proteins like enzymes and receptors. Commercial NMR systems, utilizing advanced superconducting magnets, can achieve magnetic fields up to 28.2T. Efforts continue to develop even stronger magnetic fields to study more complex molecules, pivotal in biomedical research for a deeper understanding of virus functions and identifying therapeutic targets. These developments play a key role in advancing treatments for diseases like HIV, influenza, tuberculosis, and cancer. However, the complexity and cost of MRI and NMR technologies pose significant challenges for smaller healthcare providers and research institutes, especially in less affluent countries. Therefore, there is a drive to create more efficient and cost-effective systems, with advancements in superconductor technology being central to improving accessibility and availability.
Clean Energy from Nuclear Fusion
Superconductors hold the potential to enable nuclear fusion, a promising source of clean energy generation. Nuclear fusion, contrasting with the current nuclear fission-based power generation, mimics the energy production process of stars by merging light elements to create a heavier element, converting mass into energy. This process is environmentally friendly, producing minimal radioactive waste and almost no carbon emissions. To harness fusion energy, plasma must be heated to temperatures much higher than the sun's core. Magnetic confinement, which uses powerful magnetic fields generated by superconductors to confine the hot plasma, is a key method to achieve this. The International Thermonuclear Experimental Reactor (ITER) project, involving collaboration from 35 countries, is a significant step towards realizing fusion power. It aims to demonstrate the feasibility of fusion energy and prepare for the construction of a Demonstration Power Plant (DEMO) that could generate electricity on a large scale by 2050. The development of new superconductors capable of producing stronger magnetic fields has raised hopes for more compact fusion reactors. The Fusion Industry Association reports growing confidence among investors and executives that net-gain fusion reactions are achievable, with commercial fusion expected to integrate into the electrical grid by the 2030s.
A Key Element of Particle Accelerators
Superconductors are instrumental in particle accelerators, impacting a wide range of applications from cancer treatment to space exploration. Particle accelerators like the Large Hadron Collider (LHC) at CERN, the largest scientific apparatus ever built, rely heavily on superconductors. These accelerators use superconducting magnets to guide and focus proton beams, and superconducting radiofrequency cavities accelerate protons for collision. The discovery of the Higgs boson particle at the LHC was a significant achievement, enhancing our understanding of fundamental physics. However, much of the universe, including dark matter, dark energy, and the imbalance between matter and antimatter, remains unexplained. To explore these mysteries, CERN is planning the Future Circular Collider (FCC) to conduct experiments with energy levels far exceeding the LHC. This project requires an unprecedented amount of high-efficiency superconducting magnets, stimulating research with implications beyond particle physics. In healthcare, hadron therapy uses particle accelerators for precise cancer treatment, targeting tumors with minimal damage to surrounding healthy tissue. However, the current limited availability and high cost of medical accelerators restrict access to this treatment. Advances in superconducting magnet technology are leading to smaller, more efficient, and affordable accelerators, expanding their therapeutic applications. Additionally, superconductors derived from accelerator technology are being explored for protecting astronauts from cosmic radiation during deep-space missions, crucial for future exploration of Mars and beyond.
The Need for Cryogenic Temperatures
Superconductors, despite their significant technological potential, require operation at very low, cryogenic temperatures. Typically, these temperatures range between -269°C and -196°C, varying based on the application. Liquid helium, with a boiling point of -269°C at atmospheric pressure, is commonly used as a cryogenic coolant in superconductor applications. However, helium production is limited to a few natural gas-producing countries, making it a critical resource. The recent geopolitical tensions, such as Russia's incursion into Ukraine, have significantly impacted the global helium supply, leading to price hikes and availability issues. Cryocoolers offer an alternative solution. These electrically powered refrigeration systems use cryogenic fluids, usually helium, to achieve temperatures suitable for cooling superconducting components. Cryocooler technology is versatile, applicable to small-scale applications like satellite sensors and larger ones like accelerator magnets or wind turbines. Additionally, the liquefaction of gases like hydrogen, a promising alternative to fossil fuels, is facilitated by cryocoolers. Liquid hydrogen, maintained at -253°C under atmospheric pressure, is being explored as a cooling method for superconducting electronics. The use of liquefied natural gas, which stays at -160°C under normal pressure, could enhance the implementation of superconductor applications, particularly in cooling superconducting cables for power transmission, increasing their efficiency and reducing cooling costs.
Superconductors and Quantum Computing
Superconductors could play a pivotal role in increasing the energy efficiency of electronic devices and facilitating high-speed computing capabilities. The digital transformation has led to a significant increase in energy consumption, with information technology accounting for a large portion of global electricity use. Enhancing the energy efficiency of electronics could yield considerable benefits. Traditional digital electronics, based on CMOS transistor technology, expend most energy in charging and discharging circuit interconnections. Although transistor miniaturization is approaching physical limits, advanced production techniques like three-dimensional integration will continue to increase transistor density. However, this also leads to higher power density and heat production, impacting component performance and reliability.
Superconductors, by contrast, could address these issues. Superconductor digital electronics use magnetic-flux quantization for information processing, offering improved power efficiency compared to CMOS. With no electrical resistance, superconductors consume significantly less energy for information transfer, facilitating ultrafast CPU operation at frequencies far exceeding traditional semiconductor processors. However, their practical applications are limited by the need to operate at temperatures around -269°C. Superconductors are particularly suited for high-computational power tasks, with considerable research directed towards developing energy-efficient exascale supercomputers and advancing quantum computing. Many newly developed quantum processing units (QPUs) use superconducting qubits, requiring cryogenic temperatures for optimal performance. Superconductivity is currently the only technology capable of operating at such low temperatures, enabling the creation of qubits and the essential digital circuits to control them. Several private companies are extensively researching superconducting quantum computing.
Superconductors in Mobility and Aviation
Superconductors are set to revolutionize mobility and aviation, from superconducting motors to hydrogen-powered aircraft and levitating trains. The push towards electric mobility, aimed at reducing emissions and dependence on fossil fuels, can benefit from superconductors in developing more efficient propulsion systems. Superconductors can significantly reduce energy losses and generate strong magnetic fields, leading to more powerful and lighter electric propulsion systems. Superconducting electric machines could address geopolitical challenges posed by the reliance on rare earth elements for traditional electric motors, predominantly sourced from China. The aviation industry, responsible for a substantial portion of greenhouse gas emissions, is actively seeking ways to reduce its environmental impact. The International Civil Aviation Organization (ICAO) has committed to achieving carbon-neutral growth and reducing net CO2 emissions by 50% compared to 2005 levels by 2050.
Industry leaders are pursuing the development of electric or hydrogen-fueled aircraft, with Airbus aiming to introduce the world's first hydrogen-fueled commercial aircraft by 2035. Hydrogen, with an energy density three times that of conventional jet fuel, can be converted into electrical energy using fuel cells. Maintaining hydrogen in its liquid state at cryogenic temperatures of -253°C can be used to cool superconducting engines, enabling the production of necessary energy while maintaining a lightweight propulsion system. Replacing traditional cables with superconductors could significantly reduce the weight of an aircraft's electrical distribution system. Superconducting propulsion is being explored for various transportation modes, including marine and rail, to improve energy efficiency and reduce emissions. Projects like the Central Japan Railway's Chūō Shinkansen Maglev Line, which uses superconducting magnets for levitation, aim to enhance high-speed rail travel by eliminating wheel friction.
Superconductors and Renewable Energy
The electric power sector is undergoing a significant transformation due to the growing acceptance of renewable energy and the increased utilization of distributed generation. Superconductors can contribute to the modernization of grids, hence enhancing energy security. Advanced superconducting generators and high-capacity cables have the potential to enhance the efficiency and dependability of energy generation, transmission, and distribution. Regarding wind technology, onshore turbines generally have power capacities ranging from 2 MW to 5 MW, whilst offshore turbines have power ratings ranging from 5 MW to 10 MW. The ongoing quest for higher power ratings requires the creation of progressively larger turbines, resulting in a larger physical size, especially for land-based turbines. These circumstances pose difficulties because to the increased weight and the requirement for larger structures. As an illustration, a standard 5 MW wind turbine's nacelle, which houses gearboxes and generators, has a weight exceeding 170 tons. It necessitates the use of specialist cranes to hoist it onto towers that surpass a height of 100 meters. Superconducting wind turbines allow for the replacement of ordinary permanent magnets, which are constructed from rare earth elements, with superconducting coils. This substitution permits the production of much stronger magnetic fields, leading to a notable decrease in the weight of the nacelle for a given power rating.
The EcoSwing project, financed by the European Union, effectively showcased this idea through the creation and practical testing of a wind turbine that utilizes superconductivity. The testing took place on the coast of the Danish North Sea. The technology achieved a 40% reduction in generator weight, resulting in increased cost-effectiveness in the construction of wind turbines. General Electric is currently developing the integration of superconducting magnets into high-capacity offshore wind turbine generators. This initiative capitalizes on the company's extensive knowledge of superconductors, which has been acquired through various applications such as Magnetic Resonance Imaging (MRI). An important benefit of superconducting cables is their ability to achieve a high level of power density. In future smart cities, the widespread use of electric vehicles will require a substantial increase in electric power supply. To address this, superconducting cables, which can carry much more current than regular conductors of the same size, can be installed in existing infrastructure in crowded urban areas. This utilization of superconducting technology will contribute to promoting sustainable mobility. Europe, the United States, China, and South Korea have implemented power distribution networks in urban areas that utilize superconducting wires. Furthermore, various proof-of-concept initiatives worldwide have showcased the efficacy of incorporating superconducting cables into transmission networks to tackle significant power transmission obstacles, notably for large-scale power transfer from renewable sources located both on land and at sea.