Green Communication for Next-Generation Wireless Systems: Optimization Strategies, Challenges, Solutions, and Future Aspects

Table 1

Power density of various energy harvesting schemes [14].

Source of energy	Classification	Energy harvesting methodology	Power density
Mechanical energy	Motion	Electromechanical	330 μW/cm^3
	Acoustic noise	Piezoelectric	960 nW/cm^3
	Hydro & flow of wind		16.2 μW/cm^3
Thermal energy	Heat from body	Thermoelectric	40 μW/cm^2
Energy from radiation	Solar energy	Solar cells	(Indoor) <10 μW/cm^2; (Outdoor) 15 μW/cm^2
	RF	Electromagnetic conversion	(GSM) .1 μW/cm^2; (Wi-Fi) 0.01 μW/cm^2