Contactless Photovoltaic Cell Power Transfer

Abstract

One of the main reasons that the efficiency drops from cell to module is the conduction losses. To increase the efficiency of the PV module, the produced charge carriers in the semiconductor materials should be transferred to the PV module terminals with minimum conduction losses. As an alternative to the conventional cells and modules interconnections, in this thesis project, efficient ways to incorporate Wireless Power Transfer (WPT) techniques into PV cell and module architecture are being sought.

The main objectives of this research are to understand how WPT techniques can be efficiently incorporated into PV devices, such as PV cells and modules, find out whether these techniques in theory and in practice are efficient enough and suggest the best design approach as a guideline for near future prototyping.
Many different WPT methods were studied in theoretical level, such as the Capacitive Power Transfer (CPT), the Inductive Power Transfer (IPT) and the Magnetic Resonant Coupling (MRC). Based on the main advantages and disadvantages of these methods, the most efficient seems to be the MRC, which eventually was used as the main method of transferring power wirelessly in the systems of this thesis project.

The systems that were developed and studied consist of a PV generator made of a single IBC solar cell or a PV generator that consists of 16 connected in series IBC solar cells, an inverter that converts the direct current (DC) of the generators into alternating current (AC) and two resonant circuits, the primary and the secondary one. Between these circuits, the power is transferred wirelessly from the primary to the secondary one, through the magnetic field that is created.

During this project, the main mathematical models were developed and were used for simulations in both Matlab and Simulink. The main goals of these simulations were to find out which type of coils, as far as the shape, the cross section and the values of turn width, turn spacing, distance between the coils and number of turns are concerned, and which compensation topology would help the systems to develop higher efficiencies.

According to the results, when ideal DC to AC conversion at the primary side of the system is assumed, the most ideal option seems to be the Series-Series compensation topology with planar coils of circular shape and rectangular cross-section, for which the systems developed efficiencies higher than 85% when the circuits were connected with one solar cell and above 98% when the circuits were connected with one module of 16 solar cells.