Arpita Adhikari, Joydip Sengupta 

The depletion of natural energy sources demands non-conventional efficient alternatives with sustainable utility. The outstanding performance of nanomaterials resolves the energy scarcity issue through the introduction of small-scale, energy-harvesting devices, called nanogenerators. A nanogenerator is an ambient energy-harvester with exotic features of being a lightweight, sustainable and stand-alone device which promises efficient utilization of energy. Conversion of mechanical/thermal energy into electricity is the basic working principle of a nanogenerator. The nanogenerators employ piezoelectric or triboelectric properties of a material to harvest electrical energy from mechanical energy whereas for the generation of electrical energy from thermal energy the pyroelectric or thermoelectric properties are utilized. The unique and variant range of applicability of nanogenerators makes them increasingly popular among the scientific communities having interdisciplinary research interests. Nanogenerators are employed successfully in different energy sectors such as solar energy, water (blue) energy, wind energy and many more. The present chapter will summarize the fundamentals of different types of nanogenerators along with their applicability in harvesting blue energy.