Superconducting Magnetic Energy Storage Systems

The power generation stations are often heavily loaded during the peak load hours and run on much less than their capacity during the night hours. So, is it somehow possible to store the additional energy generated during the night hours and then use it as per need during peak hours?

Superconducting Magnetic Energy Storage or SMES provides this facility. One of such systems consists of a conducting coil, power electronic modulators (rectifiers and inverters) and a cryogenically cooled refrigerator. When DC current flows through a normal coil, it soon dies out due to the resistance of the coil. But u make a DC current flow though a superconducting coil and it will never die out, thus storing energy in magnetic form indefinitely. It can be later on tapped as per requirement and converted into AC with the help of inverters. This arrangement is very efficient with overall efficiency of above 95%.

The systems are already used, though on a small scale, almost all over the world. Majority SMES are used to maintain the quality of power delivered to certain plants which require extremely proper power waveforms like microchip fabrication plants. The systems are also used to maintain the stability of the power distribution grids. One of such system is installed in northern Wisconsin. Due to the operation of paper mills in the proximity, the transmission was prone to voltage fluctuations and collapse due to sudden load changes. Thus, to fortify the grid against this, SMES was installed.



Advantages of SMES –

[*]The SMES has several advantages over other power storage methods. The loss of power taking place is very less compared to other systems.
[*]The other storage methods have a considerable time delay with the conversion of stored energy into electrical energy. But SMES provides instantaneous power as per the demand.
[*]Majority of the parts used in these systems do not move and hence less maintenance is required making the systems more reliable.

Limitations of SMES –

[*]The energy capacity of presently available systems in very less. Any attempt to increase the energy capacity, makes the units too large to handle.
[*]The current capacity of the system can not be increased beyond a limit because of the breakdown of superconductors at higher values of currents than their critical current.
[*]A more number of limitations are involved pertaining to drawing extended lengths of delicate superconducting coils and health hazards arising due to constant exposure to very high magnetic fields.

However, much research is going on, on how to provide buffer zones and to obtain a long stable coil. Hence, with the advancement in material science, we can hope that these systems become more viable and serve the purpose they are built for at a much affordable cost.