By Steven Shackell
Despite new efficiencies, worldwide electricity consumption continues to increase. Energy generation and storage infrastructure must also grow. Energy storage methodologies like pumped hydroelectric, batteries, capacitor banks, and flywheels are currently used at a grid level to store energy. Each technology has varying benefits and restrictions related to capacity, speed, efficiency, and cost.
Another emerging technology, Superconducting Magnetic Energy Storage (SMES), shows promise in advancing energy storage. SMES could revolutionize how we transfer and store electrical energy. This article explores SMES technology to identify what it is, how it works, how it can be used, and how it compares to other energy storage technologies.
What is Superconducting Magnetic Energy Storage?
SMES is an advanced energy storage technology that, at the highest level, stores energy similarly to a battery. External power charges the SMES system where it will be stored; when needed, that same power can be discharged and used externally. However, SMES systems store electrical energy in the form of a magnetic field via the flow of DC in a coil. This coil is comprised of a superconducting material with zero electrical resistance, making the creation of the magnetic field perfectly efficient. Once the superconducting coil is charged, the DC in the coil will continuously run without any energy loss, allowing the energy to be perfectly stored indefinitely until the SMES system is intentionally discharged. This high efficiency allows SMES systems to boast end-to-end efficiencies of over 95%.
How does a Superconducting Magnetic Energy Storage system work?
SMES technology relies on the principles of superconductivity and electromagnetic induction to provide a state-of-the-art electrical energy storage solution. Storing AC power from an external power source requires an SMES system to first convert all AC power to DC power. Interestingly, the conversion of power is the only portion of an SMES that is not perfectly efficient, accounting for all total system loss.
The DC power is then passed through the superconducting wire to generate a large electromagnetic field, which is ultimately used to store this energy. Superconducting materials have zero electrical resistance when cooled below their critical temperature—this is why SMES systems have no energy storage decay or storage loss, unlike other storage methods.
Demonstration of a solenoid geometry generating an electromagnetic field
The superconducting wire is precisely wound in a toroidal or solenoid geometry, like other common induction devices, to generate the storage magnetic field. As the amount of energy that needs to be stored by the SMES system grows, so must the size and amount of superconducting wire. For example, a large North American SMES project was conceptually introduced with 2400MW storage capacity and featuring a storage ring tens of kilometers in diameter, buried underground.
The advantage of Superconducting Magnetic Energy Storage (SMES) systems
The defining feature of SMES systems is their unbeatable efficiency. Minimal energy is wasted in the process of storing energy. SMES systems have an end-to-end efficiency nearing 100%, while lithium-ion batteries range from 80% to 90%, and pumped hydroelectric storage sees a system efficiency range from 70% to 85%. In applications where energy may be intermittent or sparse, such as a rural microgrid or a large satellite, energy conservation may be paramount, and maximizing storage efficiency may be necessary, even if it costs more upfront.
Moreover, SMES systems exhibit rapid response times for both charging and discharging, making them ideal candidates for applications requiring swift and precise power delivery and stabilization. For example, semiconductor manufacturing or medical facilities greatly benefit from SMES systems as their equipment can generate large power surges that can easily be serviced by an SMES system, even compared to high-performance Li-Ion battery systems.
The disadvantages of Superconducting Magnetic Energy Storage systems
SMES systems have very high upfront costs compared to other energy storage solutions. Superconducting materials are expensive to manufacture and require a cryogenic cooling system to achieve and maintain a superconducting state of the coil material.
Superconductors such as yttrium barium copper oxide (YBCO) and bismuth strontium calcium copper oxide (BSCCO) are created via intricate synthesis techniques using high-purity raw materials, making them far more costly to manufacture than everyday wire. Additionally, YBCO and BSCCO have critical points at 93K (-292.3F) and 110K (-261F) at atmospheric pressure, meaning they are only superconductive when kept at extremely low temperatures and require complex cryogenic systems to create such environments.
Additionally, SMES systems are limited in their scalability. Aside from unscalable upfront costs, SMES systems have high maintenance requirements, and storage capacity cannot be easily increased. In contrast, lithium-ion battery storage systems can easily be connected, while combining SMES devices requires scaling the cryogenic cooling infrastructure in kind.
Is Superconducting Magnetic Energy Storage the future of energy infrastructure?
While SMES offers an incredibly unique advantage over other energy storage applications and is truly state-of-the-art technology, SMES is unlikely to be widely adopted in most energy storage applications in the near future. Currently, superconducting materials are limited in their capabilities and supply. Current technologies require cryogenic temperatures to exhibit superconductivity and bulk, grid-capable superconductor production has not yet been achieved.
However, physicists are working to discover new, high-temperature superconductor materials that may one day allow for room-temperature superconductivity. If this is achieved, and the material could be mass-produced, the efficiency and performance of SMES will likely propel market adoption ahead of other technologies. Advancements in superconducting materials, cryogenic technologies, and cost reduction strategies could dramatically enhance the competitiveness of SMES systems, but today, they are restricted to research and niche energy infrastructures.
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