1.2.1. A Step towards Greener Earth: More Renewable Energy, Less Fossil Fuel On Grid Areas

The variability in the output of renewable sources makes it challenging to regulate the frequency of the system, and if the frequency deviation is too great, system performance may suffer [14].

Thermal generators are not operated at full capacity but rather with a positive and negative output margin (i.e., output increases and decreases) that is utilized to change frequency. If EES can reduce output variation, thermal generator margins can be decreased, and they can run more efficiently [6].

**Figure 1.** EES: Sustainable option towards greener earth.
