Seawater Batteries as Sustainable Energy Storage Systems for the Future Renewables-based Grids

Sodium seawater batteries (SWBs) can represent a promising technology to be integrated in future renewable-based grids to face with renewable energy sources variability. SWBs employ the sodium, contained in seawater salt, as the active element and store it at the anode. Moreover, SWBs can also provide ancillary services in the view of socio-environmental sustainability, as carbon capture and seawater desalination. The present study investigates the case of SWB integration to wave energy converters to perform output power smoothing. SWB is here coupled with supercapacitors to enhance the power capability of the system. It is highlighted as the hybrid energy storage system provides additional flexibility reducing fluctuation at the point of common coupling with the grid of over 90% with respect to the generated wave power profile. Moreover, a focus on the SWB ancillary services is provided. Electric and water infrastructures can become interdependent by means of SWBs, since 20 L of desalinized water can be produced during battery charge for each charged kWh. Finally, SWBs are able to perform carbon capture (at a rate of up to 180 g CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> per kWh released) through neutralization of sodium hydroxide produced by the sodium seawater battery during discharge.