Compare & Contrast Stand Alone PV Systems ----->Direct-Coupled vs. Self-Regulating<-----
Stand-Alone PV Systems
Stand-alone PV systems are designed to operate independent of the electric utility grid, and are generally designed and sized to supply certain DC and/or AC electrical loads. Stand-alone systems may be powered by a PV array only, or may use wind, an engine-generator or utility power as a backup power source in what is called a PV-hybrid system. Stand-alone systems are most commonly used to meet small to mid-sized electrical loads. A stand-alone system is sized and designed to power a specific energy load using the solar resources available to its specific location. Stand-alone systems for AC loads must include an inverter, which will draw DC power from the battery bank and changes it to AC power for distribution.
DIRECT-COUPLED STAND ALONE SYSTEM
. DC LOAD
DC ARRAY DC LOAD
Direct–Coupled PV System The simplest type of stand-alone PV system is a direct-coupled system, where the DC output of a PV module or array is directly connected to a DC load. Since there is no electrical energy storage, such as batteries, in direct-coupled systems, the load only operates during sunlight hours. The limited power supply makes this design regularly suitable only for applications such as ventilation fans, water pumps, and for small circulation pumps on solar thermal water heating systems. Matching the impedance of the electrical load to the maximum power output of the PV array is a critical part of properly designed direct-coupled system. The limited control over...