It is usual practice to connect PV systems to the local electricity network. This means that, during the sunny hours, the electricity generated by the PV system can either be used immediately (which is normal for systems installed in offices, other commercial buildings, and industrial applications) or be sold to the authorized electricity supply companies (which is more common for domestic systems, where the occupier may be out during the day). In the evening, when the solar system is unable to provide the electricity required, power can be bought back from the network.
IStand-alone PV systems are used in areas that are not easily accessible or have no access to an electric grid. A stand-alone system is independent of the electricity grid, with the energy produced normally being stored in a deep cycle solar batteries. A typical stand-alone system would consist of a PV module or modules, batteries, and a charge controller. An inverter may also be included in the system to convert the direct current generated by the PV modules to the alternating current form required by normal appliances.
In a direct coupled PV system, the PV array is connected directly to the load. Therefore, the load, pump, can operate only whenever there is solar radiation, so such a system has very limited applications. A typical application of this type of system is for water pumping, i.e., the system operates as long as sunshine is available, and instead of storing electrical energy, water is usually stored. As the irrigation process mainly occurs in sunny hours, this solution is feasible for rural areas, with a hard place topology.
A solar water heater consists of a solar collector that absorbs solar radiation and generates usable thermal energy. The thermal energy or heat is then transferred to a fluid medium, such as water, another heat transfer fluid, or air, which flows through the collector. The thermal energy can also be stored for night time use or other times when solar radiation is not available. A major application of solar water heating systems is to provide hot water to individual homes.