We are transiting from a fossil fuel-based economy to a renewable energy-based economy. Also, India has set ambitious targets for setting up 175GW of installed renewable energy capacity by 2022. Fossil fuel based thermal power plants can run for 24 hours with high loading factors, whereas renewable energy generation is intermittent and dependent on both the time of the day and the season of the year. Hence, it is important to store energy/electricity in batteries, so that it can be used in the off-season period. Moreover, in remote places such as mountains and islands, solar energy can be harnessed only if we provide battery backup. Also, many Indian villages still lack grid connectivity.
The government has realized that the setting up of solar power plant alone is not the solution to the energy needs, but it has to also add sufficient energy storage capacities in order to harness the benefits of the former. Solar Energy Corporation of India (SECI) released tenders for 300MW of solar capacity with 15GWh battery storage in Karnataka and Andhra Pradesh. India’s largest generation utility NTPC Ltd is going to set up 50MW solar power plant with battery storage systems in the main island of Port Blair as part of the Narendra Modi government’s bid to rid the tourist hotspot of polluting diesel generators, its main source of power at present.
One of the most common batteries used for stand-alone renewable energy systems is flow batteries. Flow batteries are flexible, scalable and cheaper when compared to solid state batteries. Flow batteries store energy in liquid form in external tanks and release power when those liquids exchange ions through a special membrane. They are flexible as their capacity can be tweaked by changing the size of the tanks and their power output can be changed by adjusting the area of the membrane. They can also remain idle for a long time without losing charge and are not affected by temperature extremes. The main problem with flow batteries is the need for pumping the electrolyte from storage tanks to the inside of the power stack. This step consumes a substantial amount of energy. Thankfully some scientists led by Yi Cui, Professor at Stanford University, have published a paper on the new magnetically controlled battery in which magnetic field is used to control the flow of the electrolyte.
This battery uses the concepts of nanotechnology for moving the electrolyte in a particular direction with the use of a magnetic field. The key to the new battery design is the composition of the electrolyte, which contains lithium polysulfide mixed with magnetic iron oxide nanoparticles. When a magnetic field is applied, the nanoparticle colloids can be pulled in the desired direction. Due to the strong binding between the iron oxide nanoparticles and the lithium polysulfide, the lithium polysulfide could be pulled along with the nanoparticles. This creates a biphasic magnetic solution, with a high concentration of polysulfide on one side of the container and a low concentration on the other.
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Tests showed that the new magnetic fluid containing the iron oxide nanoparticles leads to improvements in several areas compared to an electrolyte without the nanoparticles, including a higher capacity, high volumetric energy density as well as better capacity retention and efficiency. The researchers attribute these improvements to the magnetic field’s ability to transport more polysulfide molecules. The scientists are also planning to extend the idea to other energy systems for portable electronics, transportation, etc.
Scientists and researchers are continuously developing newer batteries that overcome the limitations of older ones. The ultimate goal is to make renewable energy more accessible and affordable to all.