**6.1 Battery energy storage system (BESS)**

A battery is an electrochemical cell that transforms chemical energy right into electricity. While the battery is filled, the direct current is transformed into chemical energy; when the chemical energy is discharged, it is converted back into the flow of electrons in a direct current form [36]. Batteries are the most common storage devices for electricity. However, the term battery consists of a variety of technologies applying various operating concepts and materials. It is necessary to differentiate between two essential principles of battery: electrochemical and redox flow [36].

**Figure 3.** *Energy storage types and their discharge time [38].*

Battery-storage growths have mainly focused on transportation systems as well as smaller systems for portable power or periodic backup power, although system dimension and volume are less crucial for grid storage than portable or transport applications [39]. Future utility applications of batteries could be focused on providing peak distribution capability deferral as well as top shaving at the substation along with reliability improvement [40]. Study into battery storage at the grid range is concentrated on longevity for multitudes of charge/discharge cycles and life time, high round-trip-efficiency, capability to react rapidly to adjustments in lots or input, and practical capital costs [41]. Utility packages of batteries in future might be targeted on supplying distribution ability deferral and peak shaving on the substation in addition to reliability enhancement [40]. Batteries are regularly compared to supercapacitors for various energy applications, and it is predicted that exploiting their features (i.e., frequent electricity storage functionality without sacrificing their cycle) by means of integration should help cope with future electric-storage demanding situations. For big-scale electrical storage (e.g., strength from renewable strength sources), the use of flow batteries seems to be the most appropriate option, even though charges and development continue to be a challenge [42]. Attributes of battery storage system are:

Rated power capacity—the overall viable rapid discharge functionality (in kilowatts [kW] or megawatts [MW]) of the BESS, or the maximum rate of discharge that the BESS can obtain, starting from a completely charged position [43].


#### *Energy Storage Efficiency DOI: http://dx.doi.org/10.5772/intechopen.109851*

Cycle lifestyle/lifetime—the period of time or cycles that a battery storage unit can deliver daily charging and unloading earlier than loss or full-size deterioration. Self-discharge occurs while the accumulated charge (or energy) of the battery is depleted by internal chemical reactions or when it is not discharged to do work for the grid or the consumer. Self-discharge, calculated as a percentage of the rate misplaced for a given period of time, decreases the amount of energy needed for discharge and is a significant criterion that is not to be ignored in batteries designed for longer-lasting programs [43].

BESSs account for around 5% of worldwide energy storage capacity, far less than pumped-storage hydropower. According to Fortune Business Insights, the global battery energy storage market is estimated to reach €19.74 billion by 2027, growing at a 20.4% compound annual growth rate (CAGR). Given its availability, efficiency, and recent developments in electrochemical storage technology, a BESS is expected to be a leader in energy storage in the next years. Alternatively, on the other hand, it can compete with battery power storage systems, gaining the upper hand in some situations.
