**3. Literature review: wireless power transfer (WPT) using solar energy**

Only few relevant papers which highlight solar energy based wireless power transfer are briefly discussed here. Zambari et al., investigated the development of wireless energy transfer module for solar energy harvesting [11]. They studied the module of wireless energy transfer (WET) for interaction with the ambient solar energy. The main objective was to distribute the collected electrical energy from a solar panel module to in house loads appliances wirelessly. The investigations were carried out on the solar panel module with 240 W, 30 V, Poly Crystalline Silicon Photovoltaic solar panel. The design of the WET module was based on magnetic resonance technology. This technology uses two sub-unit modules development;

driving circuit and two coils mutually inducted to transfer energy in a suitable resonant frequency. With the advantage of nearly 99% efficiency theoretically, class-D RF power amplifier was used as the driving circuit for transmitted coil switching [11].

Fareq et al., studied the wireless power transfer by using solar energy [12]. They developed the project based on electrical power without any wires, with a small-scale by using solar energy. The power is transferred wirelessly through an inductive coupling as an antenna. The experiments were conducted and the wireless power transfer can be transfer energy up to 10 cm. with efficiency 0–10 cm; 98.87% -40% [12]. Ojha et al., investigated solar energy based wireless power transfer [13]. They reviewed on wireless power transfer (WPT) using renewable source i.e. solar energy. The principle behind WPT used was inductive coupling wherein an electric field is generated thus transmitting power from transmitter to receiver. The paper has highlighted the important use of components like a solar panel, rechargeable battery, booster circuitry, and load. Wireless transmission of power to work up a load was highlighted in the paper [13]. Lakshmi M. K., et al. investigated wireless power transmission through solar power generation [14]. The phenomenon of transfer power using a renewable source, without using wired medium. This paper mainly focused on combining both wireless and solar technologies together with use of the principle through coupled resonant objects for the transferring electricity. The overall goal of this paper is to design and implement a clean power generation and wireless power transmission system which can be used as a standard means for charging any electronic gadget [14].

Maqsood et al., investigated wireless power transmission using solar based power satellite technology [15]. The wireless electricity (Power) transmission (WET) was focal point of their research and they presented the concept of transmitting power wirelessly to reduce transmission and distribution losses. The wired distribution losses are 70–75% efficient. The paper also highlighted the benefits of using WET technology specially by using Solar based Power satellites (SBPS) and also focused on how we make electric system cost effective, optimized and well organized [15]. Keerthana et al., investigated Wireless Power Transfer Using Rectenna [16]. The Radio frequency (RF) harvesting technologies were highlighted in the paper. The RF harvesting technologies receive and convert the useful DC energy and can further be used to charge electrical devices which need low power consumption. The paper investigated a microstrip square patch antenna operating at 2.45 GHz. It was fabricated on a low-cost FR4 substrate having a dielectric constant of 4.4 with a thickness of about 1.2 mm. The L-shaped matching network was designed for maximum power transfer between the antenna and the rectifier. The HSMS-2850 zero bias Schottky diode was used as a rectifier. The RF-DC rectification was done with an efficiency of 42.8% at -7 dBm at 2.45 GHz [16].
