The energy harvester is the key component of an energy harvesting wireless communications system. Firstly, the harvester is the interface between the energy source in the natural environment and the circuit in the communications device. Thus, its design has a significant impact on the performance of the communications device. Any changes in the natural environment could be passed on to the communications device via the harvester. Secondly, the harvester supplies energy to the wireless device. Hence, the design of the wireless device also relies heavily on the characteristics of the energy harvester for efficient operation. For example, data transmission is only possible when enough energy is harvested. This necessitates the study of the conversion efficiency of the energy harvester.
In the previous chapter, we discussed some commonly used energy sources in energy harvesting wireless communications. These different energy sources will require different energy harvesters. These energy harvesters serve as transducers to convert non‐electrical energy into electricity.
In this chapter, we will first discuss the principles and efficiencies of different energy harvesters. We will focus on two main harvesters that have been widely used in energy harvesting wireless communications systems: the radio frequency (RF) energy harvester and the photovoltaic (PV) panel, which convert the RF power and solar/light power into electricity, respectively.