Because local weather might create short-term changes in wind and solar output, generating timings may vary from demand times. For instance, solar power often produces at its highest level in the middle of the day, yet peak demand is frequently observed in the evening.
Different solutions are therefore needed as a result. Energy storage systems can range from immediate responses for daily and near-real-time network management to longer-term options for uncertain weekly supply and demand fluctuations and more predictable seasonal fluctuations.
The different energy storage solutions can be classified into five key technical categories:
Batteries are an electrochemical device made up of one or more cells with a positive terminal known as a cathode and a negative terminal known as an anode. Batteries are the oldest, most well-liked, and most accessible kind of storage.
Different chemistries are employed by batteries. The most popular and widely used batteries in portable electronic devices and automobiles are lead acid and lithium-ion. Nickel-cadmium, sodium-sulfur, and zinc-air are some more solid battery types.
Another type is flow batteries that use liquid electrolyte solutions, like vanadium redox, iron-chromium, and zinc-bromine chemistries.
Supercapacitors, while not a battery, can be categorized as an electrochemical technology, with the majority of its uses in sub-minute level response.
In addition to potential changes in the storage medium’s state, such as from gas to liquid or from solid to liquid and vice versa, thermal storage involves the absorption and release of heat or cold in a solid, liquid, or air.
Cryogenic storage, as well as molten salt and liquid air storage, are all forms of energy storage. Molten salt has become an economically viable heat storage alternative thanks to concentrated solar power, but the need for enormous subsurface storage caverns may limit its use and that of other heat storage techniques.
Perhaps mechanical energy storage systems are the simplest ones, which store energy using the kinetic forces of rotation or gravity. Modern grid applications, however, demand the utilization of cutting-edge technologies in order to be feasible.
Flywheels and compressed air energy storage systems are the main solutions, and there are also a number of new technologies for gravitational energy.
For much of the previous century, utility-scale energy storage with pumped hydro systems based on large water reservoirs has been the most popular type worldwide.
The ‘energy storage’ in the upper reservoir must be released when the water is delivered to the lower reservoir, requiring a water cycle between two reservoirs with varying water levels.
A still-in-development hydrogen energy storage system would electrolyze electricity to create hydrogen, which would then be stored in tanks. Then, as a replacement or addition to gas, it can be re-electrified or supplied to new uses in transportation, industry, or residential buildings.