TERMS AND DEFINITIONS USED IN SOLAR PV TECHNOLOGY

There are some basic terms that we have been using that should be carefully defined.  So we all speak the same language.  Often people not familiar with the technology may use the terms incorrectly.  Specifically, we want to be clear on the difference between modules and panels.

The basic terms used in solar PV technology are listed below:

1.    The Cell

The cell is the basic building block of a manufacture of solar modules.  The fundamental physics of the materials used determines the voltage of a cell, and the size determines the current.   Usually manufactures settle on one or two basic sizes and designs for their cells and then proceed to make millions of them.  They can be packaged and exported to other module manufacturing facilities, and built info specialized products such as lanterns, radios and garden lights.  Think of the cell as the smallest unit to work with.  But it is fragile, and its voltage is low (typically ½ volt).  For use in the real world, it must be protected and connected to other cells to give useful voltage.

2.    The Module

The module is really the basic building block for real-world remote power systems.  It is a collection of cells interconnected by usually flat wire, and includes encapsulation to protect the cells and interconnecting wires from corrosion and impact.  It usually includes a frame to allow easy mounting, and a junction box to allow wiring to other modules or to the battery and loads.  The number of cells connected on series determines the final voltage of the module.  Usually module is a 30-36 silicon cells to give a particular voltage, which is suitable for use in utility power systems.  A photovoltaic power system can be a needed, and then modules must be connected together.

3.    The Panel

A panel is a collection of modules physically and electrically grouped together on a structure.  This would be the building block for larger power systems.  Usually, the modules are wired together on the panel to give the final system voltage (for example 12, 24, 48 volts or higher) and the panels are wired together or individually through field junction boxes and then on the system controls and batteries.  Individual panels can be disassembled or maintained while the other panels are operational.

4.    The Array

An array is the full collection of all solar photovoltaic generators.  Sometimes an array is so large that it is grouped into sub-arrays, for easier installation and power management.  An array can be as small as one module (for a simple home lighting system) or as large as 100,000 modules or more for very large utility connected systems (form kW to MW).