ABSTRACT
A direct connection between a photovoltaic (PV) cell and a battery, a portable, or a wearable invites trouble. Instead, PV cells must be arranged in series-connected strings that provide the proper voltage to charge a battery or other energy storage device. These strings must also be connected in parallel to provide the necessary current and power required of the wearables and portables they support. In an ideal world, all PV cells in the resulting array would march in lock stop, operating seamlessly and identically. In reality, however, PV cells operate differently by virtue of both mismatches introduced in the manufacturing process and variations in operating conditions caused by partial shading, soiling, bending, aging, temperature changes, and many other factors. In order to operate successfully in these real-world conditions, maximum power points must be maintained in real-time, and fail-safe mechanisms for mitigating damage from heavily shaded or anomalous cells must be included in PV array designs. This chapter takes a look at many possible approaches to optimizing the size and distribution of PV cells in an array as well as strategies for controlling the arrays to improve power production, particularly in wearable solar cell systems.
