Solar Engineering of Thermal Processes, 4th Edition

Chapter 23

Design of Photovoltaic Systems

This chapter is an anomaly in that the processes it treats are not primarily thermal in nature. However, the equations that are encountered in design of many photovoltaic (PV) systems are very similar to those describing passive heating processes, and design methods based on utilizability concepts have been developed that are analogous to those in Chapter 22 for passive heating. Radiation calculations developed for thermal processes are directly applicable to PV converters. This chapter includes a brief description of PV converters (solar cells), models that describe their electrical and thermal characteristics, a short treatment of models of batteries and other components in the systems, and notes on applications. These serve as introductions to the design method and to comments on simulation of PV systems.

Photovoltaic converters are semiconductor devices that convert part of the incident solar radiation directly into electrical energy. A brief history of photovoltaics is presented by Wolf (1981). An early public demonstration of solar cells occurred in 1955 in Americus, Georgia, where a small panel of experimental silicon cells provided energy to charge a battery and power telephone equipment. Since then, tremendous progress has been made in the development of cell technology and applications. Early hand-made cells were 5% efficient, were 1 or in area, and had outputs of a few milliwatts. In recent years laboratory cells have been reported ...