Development of new energy sources and renewable clean energy sources is one of the five major technical fields in the economic development of the 21st century. Full utilization of the solar energy is a strategic policy for the sustained development of all countries the world over with the solar power generation attracting even more attention. Solar power generation will be applied in large scales in the long term and can meet the needs of some special fields in the short term. By the year 2030, the aggregate photovoltaic power generation will make 5~20% of the total power of the world. The solar cell has many advantages in power generation. For example, it is safe, reliable, noise free, pollution free, not limited by different regions, and does not consume any fuel or have any moving parts. The malfunction rate is low; the maintenance and servicing is easy and simple; it does not require any person on duty. The construction period is short. The scale and size can be whichever as you want. It does not require the use of electric lines and can be easily combined with buildings and structures. All these merits are incomparable for the conventional power generation and other means of power generation.

• The sketching of a grid-connected PV system

  

• The sketching of a off-grid PV system

  

Off-grid solar-energy photovoltaic power generation refers to the mode of power generation that is not connected to the electric grid. The typical feature is that it has the storage battery for storing the electric energy for use in the night. In the civilian field, the off- grid system is mainly used in the remote villages, farming areas, sea islands, plateaus and deserts for the purpose of lighting, TV, radio and other basic needs of life; in the industrial fields, it is mainly used for communication, relay of satellite broadcast and TV, solar-energy water pumps, navigation marks, anode protection of oil pipelines, weather stations, highways and check points at borders. In the regions where wind power generation and small-sized hydraulic power generation are available, combined power generation system can be set up, e.g. wind power generation and solar power generation.