Photovoltaic power generation-principle and application

The development of photovoltaic power generation

In 1839, it was discovered that current increases when two metal electrodes in a conductive liquid are illuminated with light.

In 1930, it was proposed to use the “photovoltaic effect” to make solar cells turn solar energy into electricity.

In 1932, the first “cadmium sulfide” solar cell was built.

In 1941, the photovoltaic effect was discovered on silicon.

In 1954, monocrystalline silicon solar cells with an efficiency of 6% were developed, which was the world’s first practical solar cell. In the same year, nickel arsenide was discovered to have a photovoltaic effect, and nickel sulfide films were deposited on glass to make solar cells. Solar practical photovoltaic power generation technology was born and developed.

The average annual growth rate of photovoltaic modules in the world from 1990 to 2005 was about 15%. In the late 90s of the 20th century, the development was more rapid, and in 1999 the production of photovoltaic modules reached 200 MW.

The efficiency of commercial cells has increased from 10%~13% to 13%~15%, and the production scale has developed from 1~5MW/year to 5~25MW/year, and is expanding to 50MW or even 100MW. The production cost of PV modules has fallen below $3/W.

In 2011, the global installed capacity of photovoltaics increased by 52%, and the cumulative global installed capacity exceeded 67GW.

China is the fastest growing country in the world in terms of photovoltaic power generation facilities. China’s photovoltaic power generation market, with active and stable policy support, will usher in a new round of rapid growth, and will attract more strategic investors to integrate into the industry.

A brief introduction of solar photovoltaic power

Solar photovoltaic effect, referred to as “photovoltaic”. Simply put, as long as there is sunlight, it can generate electricity. This is a project promoted by the government, the trend of new energy development in the future, and a favorable project that can alleviate poverty and get rich.

Classification of photovoltaic power generation

Photovoltaic power plants are mainly divided into two categories: centralized power stations and distributed power stations. Because photovoltaic power plant installation has the characteristics of high flexibility compared to wind power.

Therefore, compared with traditional large-scale wind power plants, photovoltaic power plants can not only be installed on a large scale, but also distributed in multiple scenarios such as building surfaces and outdoors.

● Centralized photovoltaic power station

It refers to the installation of photovoltaic arrays in mountains, water surfaces, deserts and other wide areas. After sunlight, photovoltaic arrays can generate direct current. The inverter then converts direct current into alternating current, which is connected to the grid through a booster station.

The scale of centralized photovoltaic power plants is generally large, generally more than 10MW, and the current super-large photovoltaic power plants of more than 100MW are gradually increasing.

● Distributed photovoltaic power generation

Distributed photovoltaic power generation refers to photovoltaic power generation facilities built near the user site, and the operation mode is characterized by spontaneous self-consumption on the user side, excess electricity on the Internet, and balanced regulation in the power distribution system.

Distributed photovoltaic power generation follows the principles of local conditions, clean and efficient, decentralized layout and nearby utilization, makes full use of local solar energy resources, and replaces and reduces fossil energy consumption.

It advocates the principle of nearby power generation, nearby grid connection, nearby conversion, and nearby use, which effectively solves the problem of power loss in boost and long-distance transportation.

Principle of photovoltaic power generation

Photovoltaic power generation is based on the principle of photovoltaic effect, using solar cells to directly convert solar energy into electrical energy. Whether used independently or connected to the grid, the photovoltaic power generation system is mainly composed of three parts: solar panels (components), controllers and inverters.

They consist mainly of electronic components and do not involve mechanical components. Therefore, photovoltaic power generation equipment is extremely refined, reliable and stable, long life and easy to install and maintain.

Theoretically, photovoltaic power generation technology can be used in any occasion where power is needed. The most basic components of solar photovoltaic power generation are solar cells (sheets), including monocrystalline silicon, polysilicon, amorphous silicon and thin film cells.

Solar photovoltaic power generation system is mainly composed of solar photovoltaic battery pack, photovoltaic system battery controller, battery and AC and DC inverter are its main components. The core components are the photovoltaic cell pack and controller. The role of each component in the system is:

● Photovoltaic cells

Photoelectric conversion. Converting light energy into electrical energy for use, many of the top 10 photovoltaic cell manufacturers in China have owned this technology.

● Controller

Process control over the entire system. There are many types of controllers used in photovoltaic power generation systems, such as two-point controllers, multi-channel sequential controllers, intelligent controllers, high-power tracking charge controllers, etc. Most of the controllers currently used in China are simple designs, and intelligent controllers are only used in communication systems and larger photovoltaic power plants.

● Accumulator

Batteries are key components in photovoltaic power generation systems and are used to store electricity converted from photovoltaic cells. At present, there is no special battery for photovoltaic systems in China, but conventional lead-acid batteries are used.

● AC and DC inverter

Since its function is AC/DC conversion, the most important indicators of this component are reliability and conversion efficiency. The grid-connected inverter adopts maximum power tracking technology to maximize the power converted by photovoltaic cells into the grid.

Photovoltaic power generation mode

● Mode 1: All spontaneous and self-use

The popular understanding is that the user’s photovoltaic system generates all its own power consumption. Mostly used in off-grid systems.

● Mode 2: Spontaneous self-consumption, surplus electricity for sale

The electricity generated by the user’s photovoltaic system is first used by itself, and the excess electricity is sold to the grid. This mode is the most widely accepted mode of application at present, and it is also the main mode promoted everywhere.

● Mode 3: Sell the electric all

All electricity generated by the user’s photovoltaic system is sold to the grid. This pattern was more common earlier and is now gradually decreasing.

Application field of photovoltaic power generation system

● User solar power supply

Used for remote areas without electricity such as plateaus, islands, pastoral areas and other domestic electricity. Such as lighting, TV, tape recorder and other power generation systems connected to the home grid.

● Photovoltaic water pump
Solves the problem of drinking and irrigation of deep water wells in areas without electricity.

● Communication field

Broadcasting, communication system, telephone photovoltaic system, small communication machine, etc.

● Home lights

It can be used for home energy storage. Such as garden lights, street lights, portable lights, camping lights, mountain lights, fishing lights, energy-saving lights and so on.

● Photovoltaic power station

10KW-50MW independent photovoltaic power station, wind power and photovoltaic complementary power station, various large-scale parking charging stations, etc.

● Other fields

Solar cars, electric vehicles, battery charging equipment and so on. Regenerative power generation system for solar hydrogen production and fuel cells.

Advantages and disadvantages of photovoltaic power generation

Advantages of photovoltaic power generation

● Economic and energy saving

Generally, self-consumption, excess electricity can be sold to power companies through the national grid. When it is insufficient, it is supplied by the grid, so that it can save electricity bills and get subsidies;

● Heat insulation and cooling

In summer, it can be insulated and cooled by 3-6 degrees, and heat transfer can be reduced in winter.

● Green environmental protection

In the process of power generation, there will be no light pollution in the distributed photovoltaic power generation project, which is static power generation with zero emissions and zero pollution in the true sense.

● Aesthetic personality

The perfect combination of architecture oraesthetics and photovoltaic technology , so that the entire roof looks beautiful and atmospheric, has a strong sense of technology, and enhances the value of the property itself.

● Safe and reliable

The grid-connected voltage is generally below 220 volts, there is no noise, no pollution discharge, and it is clean. It is not limited by the geographical distribution of resources, and you can take advantage of the advantages of building roofs. There is no need to consume fuel and erect transmission lines to generate electricity locally.

The disadvantages of photovoltaic power generation

● The energy distribution density of irradiation is small and occupies a large area.

● High cost of power generation.

● The energy obtained is related to the four seasons, day and night, and sunny weather conditions.