Prospects for the development of international solar photovoltaic power generation technology

As early as 1839, French scientist Becqurel discovered that light can cause a potential difference between different parts of semiconductor materials. This phenomenon was later called the “photovoltaic effect”, or “photovoltaic effect” for short. In 1954, American scientists Chapin (Chapin) and others made practical monocrystalline silicon solar cells for the first time at Bell Labs in the United States, giving birth to a practical photovoltaic power generation technology that converts sunlight energy into electrical energy.

After the 1970s, with the development of modern industry, the global energy crisis and air pollution problems have become increasingly prominent, traditional fuel energy is decreasing day by day, and the harm to the environment has become increasingly prominent. normal energy supply. At this time, the whole world has turned its attention to renewable energy, hoping that renewable energy can change the energy structure of human beings and maintain long-term sustainable development. Solar energy has become the focus of attention due to its unique advantages. Abundant solar radiation energy is an important energy source, which is inexhaustible, non-polluting, cheap, and freely usable by human beings. Broad and market size is also gradually expanding.

After the 1990s, photovoltaic power generation technology developed rapidly. In 2006, more than 10 MW-level photovoltaic power stations have been built in the world. The United States was the first country to formulate a development plan for photovoltaic power generation. In 1997, it proposed the “Million Roofs” plan. Japan launched the New Sunshine Project in 1992. In 2003, Japan’s photovoltaic module production accounted for 50% of the world’s total, and 4 of the world’s top ten manufacturers were in Japan. Germany’s new renewable energy law stipulates the on-grid tariff for photovoltaic power generation, which greatly promotes the development of the photovoltaic power generation market and industry, making Germany the country with the fastest development of photovoltaic power generation in the world after Japan. Switzerland, France, Italy, Spain, Finland and other countries have also formulated photovoltaic power generation development plans, and invested heavily in technology development and accelerated industrialization.

In the late 1990s, photovoltaic power generation developed more rapidly. From 1990 to 2005, the average annual growth rate of photovoltaic modules in the world was about 15%. In 1999, the production of photovoltaic modules reached 200 MW. The efficiency of commercial solar cells has increased from 10% to 13% to 13% to 15%, and the production scale has grown from 1 to 5 MW/a to 5 to 25 MW/a, and is expanding to 50 MW/a or even 100 MW/a; The production cost of PV modules has fallen below $3/W.

Internationally, it is difficult to determine which solar cell to choose. Although crystalline silicon cells have the largest sales volume, it is recognized that thin-film cells have the greatest potential in the future. In addition, different solar cells have different characteristics and have different application fields in the photovoltaic market. For example, amorphous silicon cells are mainly used in commercial electronics, polycrystalline silicon cells are mainly used in photovoltaic roofs, and monocrystalline silicon cells are mainly used in high-power applications. In recent years, the international research on polycrystalline silicon thin film batteries has been active, but it is still difficult to determine which process scheme is better. In recent years, the efficiency of organic nano-solar cells has been greatly improved, which has attracted certain attention. If you want to know more about the battery you can click here to open

The main market developed by developed countries in recent years is the rooftop grid-connected solar photovoltaic power generation system. The electricity price of photovoltaic power generation in good areas is close to the commodity electricity price. It is predicted that the rooftop grid-connected solar photovoltaic power generation system will be popularized and applied on a large scale in 10 years.

Schematic diagram of solar photovoltaic power generation
Schematic diagram of solar photovoltaic power generation

The application of grid-connected solar photovoltaic power generation systems began in the early 1980s, and the United States, Japan, Germany, Italy and other countries have made efforts for this. They range from 1 MW, and they are all experimental power plants invested and constructed by the government. But the test results were not very satisfactory, because solar cells were expensive at the time, and it was difficult for power companies to accept them.

Since the 1990s, developed countries in foreign countries have once again set off a climax of developing grid-connected solar photovoltaic power generation systems. This time, instead of building large-scale grid-connected solar photovoltaic power plants, they are developing rooftop grid-connected solar photovoltaic power generation systems. The rooftop grid-connected solar photovoltaic power generation system makes full use of the dispersive characteristics of sunlight, and installs solar cells on the roofs of existing buildings. Its flexibility and economy are much better than large-scale grid-connected solar photovoltaic power stations. Pay attention to.

In 1993, Germany first began to implement the 1,000-roof plan supported by government investment and recognized by power companies, and then expanded to the 2,000-roof plan. Now more than 5,000 rooftop grid-connected solar photovoltaic power generation systems have actually been built. These rooftop grid-connected solar photovoltaic power generation systems do not have batteries, and power companies purchase electricity from grid-connected photovoltaic power generation systems, which greatly stimulates the commercial development and technical improvement in this field. The German government began to implement 100,000 sets of solar roofs (about 3~5kW per household) plan in 1999. The government gave users about 35% of subsidies and 10-year interest-free loans.

Japan has made efforts in the combination of solar photovoltaic power generation and buildings for more than ten years, especially after 1996, it has made rapid progress. Every year, tens of thousands of new rooftop grid-connected solar photovoltaic power generation systems are built. One of the characteristics of the development of rooftop grid-connected solar photovoltaic power generation systems in Japan is that solar cell components are made into the form of building materials, such as tiles and glass, so that solar cells can be easily installed on buildings and can easily be constructed by buildings. The company accepts.
In the early 1980s, the United States had already begun efforts to connect solar photovoltaic power generation to the grid, and formulated the PV-USA plan, that is, the large-scale application of solar photovoltaic power generation, mainly to establish large-scale grid-connected solar photovoltaic power generation systems of more than 100kW. The system is planned to reach 10MW, but due to the high cost, the power cannot be dispatched and is not welcomed by the power company. In 1996, with the support of the US Department of Energy, another “Photovoltaic Buildings Program (PV-BONUS)” was started, with a planned investment of 2 billion US dollars. Two-thirds of the current electricity in the United States is used to supply power to various buildings including residential buildings. The goal of the photovoltaic building plan is to use solar photovoltaic power generation to alleviate the peak load of buildings and to explore a clean building power supply in the future. This plan will help to develop new photovoltaic building materials, including glass, skylights, walls, etc., help to develop modules for rooftop grid-connected solar photovoltaic power generation systems and photovoltaic peak-shaving power modules that can be easily installed by the power sector. . The plan is implemented in three steps: concept development, product development and market development. The program is very rich, and typical development projects include the following points.

(1) DsM system (a system that arranges power generation according to demand), that is, a photovoltaic power generation system in which power with batteries can be dispatched. This grid-connected solar photovoltaic power generation system will have a market of 300MW in the United States and China alone in the next few years. At present, the power generation cost of such a system is 40 cents/kW·h, while the peak electricity price in some parts of the United States has reached as high as 2030 cents/kW·h (generally, the electricity price in winter is 3~4 cents/kW·h, and in summer it is 2,030 cents/kW·h). 7~8 cents/kW h). It is estimated that this kind of peak-shaving solar photovoltaic power generation system can enter the market soon.

(2) Photovoltaic and photothermal systems composed of solar water heaters and amorphous silicon solar cells can provide users with electricity and hot water at the same time. Amorphous silicon solar cells are particularly suitable for this type of system because their output power is not reduced as the temperature rises like crystalline silicon solar cells.

(3) Photovoltaic roof building materials (flexible and non-flexible), such as transparent photovoltaic glass, concentrating battery-powered water supply systems, photovoltaic walls, photovoltaic smart curtains, etc. In addition to rooftop grid-connected solar photovoltaic power generation systems, some developed countries have also done a lot of work in other photovoltaic technology applications, mainly in the following aspects:
(1) Wind-solar diesel hybrid power generation system. In order to further reduce the power generation cost of renewable energy, foreign countries have done a lot of demonstration work and economic comparison on the wind-solar-diesel hybrid power generation system. The optimization software for the hybrid power generation system has also been developed, with which the most reasonable and economical power supply scheme can be designed according to local resources.

(2) Solar photovoltaic power generation system supporting automobiles in the future. The solar photovoltaic power generation system has a large potential market in the automobile industry. The more successful solar fast charging systems, solar car air conditioning panels, solar car ventilation fans, solar air conditioners and cold drink boxes that can charge electric car batteries have been developed abroad.

(3) The regenerative power generation system of solar hydrogen production and fuel cell. Finland’s NAPs have completed demonstration projects for this power generation system. The solar cell converts solar energy into electricity, and through the electrolysis of water, hydrogen and oxygen are produced, the oxygen is discharged into the air, and the hydrogen is stored in a hydrogen storage tank. When in use, the hydrogen and oxygen in the air pass through the fuel cell to generate electricity, and the hydrogen and oxygen are converted into water during the power generation process. This system belongs to the cleanest renewable energy power generation system and will have a huge market in the future, especially for high latitude regions where solar radiation varies greatly in winter and summer, and the use of batteries is extremely uneconomical. Using solar energy in this way will be very effective. In addition, with the development of electric vehicles, this power generation system will also become more important.

(4) Renewable energy island power supply system. The island is a special environment, because of its lack of fresh water and expensive fuel, which makes renewable energy useful. A large number of demonstration projects have been done abroad for the application of wind-solar-diesel hybrid power generation systems on islands to supply electricity and fresh water to the islands. In addition, because the island’s fishermen need to use ice to store and transport fresh fish and shrimp, the island’s renewable energy ice-making system has also been promoted and applied.

(5) Special DC load for solar power generation. In order to improve the efficiency of the solar photovoltaic power generation system and reduce the failure links, many foreign countries have developed many DC loads that do not require inverters and can be directly powered by solar cells and batteries, including DC TVs, DC refrigerators, DC air conditioners, etc. The load is especially suitable for vehicles, boats and mobile units such as tour groups, geological teams, troops, etc.

Read more: How is a solar photovoltaic system constructed?