ABB, a Swiss-based engineering company, has presented a prototype of their innovative superconducting magnetic energy storage (SMES), at a DOE ARPA-E conference which took place in Washigton D.C. at the beginning of this month. Their 3.3 kWh proof-of-concept SMES is not very cost-effective for the moment, but may one day provide cleaner storage solutions for excess alternative energy.
For the matter of storing energy for medium to large institutions, flywheels, pumped hydro or compressed air are generally being used nowadays. ABB’s SMES sits between flywheels and the latter two regarding its price, but has a longer lifespan than any of them, which may result in big financial advantages in some cases.
So, how does the SMES work? It stores energy in the form of an electromagnetic field generated by direct current that circulates through high-temperature superconducting coils. Their geometry is the one that make the entire assembly contain the electromagnetic field. For keeping the field alive, only a small relative amount of energy is needed. When needed, the coils can be discharged and the stored energy used.
Flywheels do the same but they “encapsulate” the energy in their rotation momentum, at some 65,000 rpm. Pumped hydro does what it says: it pumps water uphill and then re-harvests the energy of the falling stream with a water turbine. Compressed air is also simple to understand, because it uses air pressure to store the energy.
One issue that united all of the three conventional methods used so far is that they rely on mechanical systems, whose failure rate is higher than the one of a magnet’s. Batteries, on the other hand, offer an industry-standard method for that matter, but they’re also expensive and need frequent maintenance.
Superconducting magnets seem at this point the perfect solution for storing the energy produced at times when wind blows too hard and there are no consumers to buy the energy, or when the Sun doesn’t shine and there’s a big need for electricity for a short time.
A 1-to-2 megawatt-hour SMES is envisioned by ABB, but some say this still wouldn’t be enough to outprice lead acid batteries. Only for capacities reaching several tens of megawatts would such a system make sense financially, said Cesar Luongo, the senior magnet-division coordinator for the International Thermonuclear Experimental Reactor project in Cadarache, France, not involved with the project.
The lifetime of an SMES could reach up to 20 years, just like compressed air and pumped hydro systems’, but these two require special building conditions, no matter how little they may cost compared to an SMES.
ABB stated that they strongly believe in the outcomes of their technologies and have invested wisely in developing it: “If we didn’t think this had potential, we would not have gone after this,” says ABB project manager V.R. Ramanan.