**6. Energy storage technologies**

Energy storage technology is often classified on the basis of its use in large- or small-scale applications. Flywheels, pumped energy storage, and compressed air storage are among the forms of storage typically used in large scales. Battery systems are expected to have a significant impact on the small-scale installation of clean energy resources in commercial and residential buildings [35]. Some technologies provide short-term energy storage; others can endure for much longer. In short-term response energy storage devices as a short-term duration applications whose big advantage is quick discharging, we identify flywheels or supercapacitors. Moreover, their application prevents the collapse of power systems, and use of short-term response energy system is more practical in terms of renewable energy like wind [36]. Use of longterm energy storage devices is expected to be functional even more in the upcoming years, and these devices are compressed air technology, batteries, or pumping hydro storage. Energy storage contains technologies such as flywheels or flow batteries that are part of a so-called "distributed" storage, and technologies such as PHES or CAES are very important in "bulk" storage [37]. **Figure 3** shows these technologies divided into categories:

**Figure 1.** *Schematic of a typical binary cycle geothermal power plant [33].*

**Figure 2.** *Storage types and applications [34].*
