Energy storage plays an important role in a more flexible and reliable grid system. When there is more supply than demand, such as during the night when low-cost power plants continue to operate, excess generation can charge storage devices. Renewable energy (PV, wind, geothermal) produces the energy, and the battery stores it for times of low or no production.
Most batteries employed in renewable energy systems use the same electro-chemical with which we are familiar in our vehicles and devices.