Photovoltaic system types

PV systems can be very simple, just a PV module and load, as in the direct poweringof a water pump motor, or more complex, as in a system to power a house. While awater pump may only need to operate when the sunshines, the house system willneed to operate day and night. It also may have to run both AC and DC loads, havereserve power and may include a back-up generator. Depending on the systemconfiguration, we can distinguish three main types of PV systems: stand-alone, grid connected,and hybrid. In either case, basic PV system principles and elements remainthe same. Systems are adapted to meet particular energy requirements by varying thetype and quantity of the basic elements. Ads as systems are modular; they can always be expanded, as power demands increases

Stand-alone systems

Stand-alone systems rely on PV power only. These systems can comprise only PVmodules and a load or can include batteries for energy storage. When using batteriescharge regulators are included, which switch off the PV modules when batteries arefully charged, and switch off the load in case batteries become discharged below acertain limit. The batteries must have enough capacity to store the energy producedduring the day to be used at night and during periods of poor weather

Diagram of stand-alone PV system with battery storage powering DC

Grid-connected systems

Grid-connected PV systems have become increasingly popular as building integratedapplication. They are connected to the grid through inverters, and do not requirebatteries because the grid can accept all of the electricity that a PV generator cansupply. Alternatively, they are used as power stations. A grid-connected PV system is schematically presented in figure 

Diagram of grid-connected photovoltaic system

Hybrid systems

Hybrid systems consist of combination of PV modules and a complementary means ofelectricity generation such as a diesel, gas or wind generator. Schematically is a hybrid system shown in figure 2.28in order to optimize the operations of the twogenerators, hybrid systems typically require more sophisticated controls than standalonePV systems. For example, in the case of PV/diesel systems, the diesel enginemust be started when battery reaches a given discharge level and stopped again whenbattery reaches an adequate state of charge

 Diagram of photovoltaic hybrid system