Electrochemical energy storage Batteries were the first energy storage systems to be integrated with low energy harvesting technologies [, , ], and the most used power storage system in conventional portable electronic devices . 3.1.1.
When investigating any energy storage systems' technical potential, the common factors that are mainly considered are the energy density, power density, self-discharge, lifetime, discharge durations, and response time . Table 3 shows each technical features of different available energy storage systems used for micro/small-scale devices.
Energy storage systems, and in particular batteries, are emerging as one of the potential solutions to increase system flexibility, due to their unique capability to quickly absorb, hold and then reinject electricity.
Also, the study confirmed that the proposed design could be utilized in low power applications, including sensors and monitoring systems. The main limitation of this technology is low thermal conductivity in the transition of the phase change process. 3.2.4. Mechanical energy storage
Each of the available energy storage devices is suitable for a specific application range. CAES and thermal energy storage are suitable for energy management implementations. While capacitors, supercapacitors, and batteries are more suitable for a short duration and power quality. Also, batteries are a more promising system for power distribution.
Electrical energy storage is considered a reinforcing technology for solving issues with impedance mismatch for distribution networks wherein energy is stored in a particular state and transformed into electrical energy. Capacitor and supercapacitor are an example of these systems .