There are two kind of solar photovoltaic (PV) power generation systems, grid-tied system and stand-alone systems.

In general, the solar PV grid-tied power generation systems consist mainly of two parts:

PV Array: A number of PV modules are connected in series and/or in parallel, giving a DC output under the sunlight. Orientation and tilt of these modules are important design parameters, as well as avoiding the shadows from surrounding obstructions.

 

Grid-tied inverter: converts the DC power from the PV array into AC power with suitable phase, voltage and frequency.

The electricity generated by the PV array is direct current (DC), and then the DC power is converted into alternative current (AC) by the grid-tied inverter. The electricity generated by the solar PV grid-tied power systems will be fed into the utility grid. According to the feeding style, grid-tied PV systems are divided into small utility interactive PV-systems and utility scale. The former can be used by private owners for their own consumption. Energy surplus will be fed into the grid, while in times of shortage (such as at night) electricity will be consumed from the grid. The latter also calls central station PV fields, managed by the utilities in the same way as other electric power plants. All DC output of the PV array, which is generally of megawatt range, is converted to AC and fed into the central utility grid, then it is distributed to the customers. In a grid-tied power system the grid acts like a battery with an unlimited storage capacity. Therefore, the total efficiency of a grid-tied PV power system will be better than the efficiency of a stand-alone system as there is virtually no limit to the storage capacity, the generated electricity can always be stored, whereas in stand-alone applications the batteries of the PV system will be sometimes fully loaded, and therefore the generated electricity needs to be "thrown away".

 

The stand alone PV power system is independent from the utility grid, especially, in the remote area where the utility is hard to access, and in the urban area, the stand alone system will be used to avoid the possibility of losing power when the grid goes down. Electricity from stand-alone systems can be stored in batteries and used at night or on sunless days. A generator may also be used for back-up.

 

System includes:

PV Array: as same as in grid-tied system

Recharge controller: controls battery bank recharge and discharge.

Inverter: inverts the DC power from the PV modules into AC power.

Battery bank: multiple batteries connected together in series and/or in parallel to create essentially one large battery of the required voltage and amp-hour capacity. In some ways the battery configuration and capacity are the most important electrical power decision to make, and a wise choice can help guarantee a steady supply of electrical power as well as a system that is simple to operate and maintain.

Loads: various electrical appliances.