The basic PV or solar cell (for example: Goal Zero Nomad 20 ) typically produces only a small amount of power. To produce more power, solar cells (about 40) can be interconnected to form panels or modules. PV modules range in output from 10 to 300 Watts. If more power is needed, several modules can be installed on a building or at ground-level in a rack to form a PV array.
Energy performance ratings for PV modules include the following:
Home Solar Electric System Arrays
For home solar electric systems, the most common array design uses flat-plate PV modules or panels. These panels can either be fixed in place or allowed to track the movement of the sun.
The simplest PV array consists of flat-plate PV modules in a fixed position. These are some advantages of fixed arrays:
These features make them suitable for many locations, including most residential roofs. Because the panels are fixed in place, their orientation to the sun is usually at an angle that is less than optimal. Therefore, less energy per unit area of array is collected compared with that from a tracking array. This drawback, however, must be balanced against the higher cost of the tracking system.
Solar arrays are designed to provide specified amounts of electricity under certain conditions. The following factors are usually considered when determining array energy performance:
The amount of electricity required may be defined by any one or a combination of the following performance criteria:
This last parameter is often given as a power efficiency, equal to "power output from array" ÷ "power input from sun" × 100%. Power is typically given in units of Watts (W), and energy is typically in units of Wh, or the power in Watts supplied during an hour.
To ensure the consistency and quality of PV systems and increase consumer confidence in system performance, various groups -- such as the Institute of Electrical and Electronics Engineers (IEEE), the International Electrotechnical Commission (IEC), and the American Society for Testing and Materials (ASTM) -- are working on standards and performance criteria for PV systems.
Home Solar Electric Components
A typical home solar electric system consists of these components:
The balance-of-system equipment required depends on whether the system is a stand-alone system, connected to the electric grid, or a hybrid system. Balance-of-system equipment can include: