Photovoltaic Systems Engineering SEC598 Photovoltaic Systems Engineering (SEC501 Solar Engineering and Commercialization, I) Session 04 Solar Cells, Part 1 August 29, 2018

Session 04 Components PV System Components Overview Solar cells

Learning Outcomes Introduction to solar energy system components Introduction to operation of solar cells

PV System: Definition A photovoltaic system (or PV system) is an engineered system that carries out these operations: Absorption of incident solar radiation Conversion of the absorbed solar energy to DC electrical energy Controlled transfer of the DC electrical energy to a storage device (such as an array of batteries) OR Controlled inversion of the DC electrical energy to AC electrical energy Controlled transfer of the electrical energy to electrical loads or to the electrical grid

PV System Configurations A simplified version of a “stand-alone” system that transfers DC electrical energy to a storage device

PV System Configurations A simplified version of a “grid-tied”system that inverts the DC electrical energy to AC electrical energy and transmits that energy to the national grid

Solar Energy Conversion Optical Energy is the energy contained in light; Optical Power is the rate at which optical energy is delivered Electrical Energy is the energy contained in electrons and other charged particles; Electrical Power is the rate at which electrical energy is delivered to an “electrical load” Electrical Power is calculated by multiplying the Electrical Current and the Electrical Voltage in the electrical device Current is a measure of the flow of electrons (amperes) Voltage is a measure of the potential energy (volts)

PV System Components - Solar Cells The electrical “device” that converts optical energy to electrical energy is the Solar Cell. The solar cell is a semiconductor device invented in 1954 at Bell Telephone Laboratories by Russell Ohl: The vast majority of solar cells are made from silicon. And this is remarkable good fortune, since silicon is the third most abundant element on earth!!

PE vs PV

Key Points for Photovoltaic Operation The solar cell absorbs optical radiation The absorption produces energetic charged particles The particles can be transported through the Solar Cell and into an external circuit before they are lost

Elements and Crystallinity

The Bonding Model Pierret

The Band Model Pierret

A simplified picture of the band model Pierret

Electrons and Holes Pierret

Another look at the Periodic Table

The Doping Model Pierret

Resources Jenny Nelson, The Physics of Solar Cells, Imperial College Press, 2003 Robert F. Pierret, Semiconductor Fundamentals, V.1., Modular Series on Solid State Devices, Addison-Wesley, 1988 Gerold W. Neudeck, The PN Junction Diode, V.2., Modular Series on Solid State Devices, Addison-Wesley, 1989