Operation and Control of Renewable Energy Systems

Chapter 6Photovoltaic Systems

6.1 PV Solar Cells and Solar Module

In photovoltaic energy systems, the solar energy (mainly sunlight) is directly converted to electric energy using photovoltaic solar cell modules. They have no moving parts, therefore require little maintenance. The basic principle of photovoltaic effect was discovered by Becquerel in 1839 using selenium. He discovered photovoltaic effect at a junction between a semiconductor (selenium) and an electrolyte. But it was not considered for power generation until 1954 when silicon semiconductors became available, and PV solar cells based on semiconductor technology were developed. Selenium and silicon are both semiconductor materials, but it was only when the three researchers, Gerald Pearson, Daryl Chapin and Calvin Fuller, at Bell Laboratories discovered a silicon solar cell, which was the first material to directly convert enough sunlight into electricity to run electrical devices. The efficiency of the silicon solar cell, which was produced at Bell Laboratories, was only 4%.

In most of today's solar cells, the absorption of photons, which results in the generation of the charge carriers, and the subsequent separation of the photo-generated charge carriers take place in semiconductor materials. A semiconductor is a material that has an electrical property which lies in between that of a conductor and an insulator. The semiconductor materials commonly used now are silicon and germanium. However, the availability ...