motherland, rows of photovoltaic panels are often seen. There is a lot of energy in their small bodies. After being illuminated by
sunlight, photovoltaic panels can generate a steady stream of electricity to light the lights of millions of households.
Nowadays, you can see them in many places. For example: on the roof, on the lake, on the hillside, even … In space!
In 2021, China's first space solar power station experimental base was launched in Bishan, Chongqing. It plans to build a "space Three Gorges" at an altitude of 36000 kilometers. Some small partners suggested that power grid enterprises open a "space power supply company".
On the other hand, what is the principle of photovoltaic power generation? How does the electricity generated enter thousands of households?
As early as 1839, French scientist Becquerel discovered that light can cause potential differences between different parts of semiconductor materials, which is called photovoltaic effect . That is to say, photons (light waves) are converted into electrons, light energy is converted into electrical energy, and voltage is formed. Solar panels in
photovoltaic power generation systems produce photovoltaic effect in the presence of light. The accumulation of charges of opposite sign at the two ends of the battery can convert light energy into DC electric energy. In addition to how photovoltaic power generation, there are also small partners who are curious about what is under the photovoltaic panel. What's under this photovoltaic panel?
It is said that there are thick green shade, fish enjoying the cool water, and even sheep grazing in groups of three or five. The wisdom of the people will always burst out with amazing power. In recent years, we have opened the era of "photovoltaic plus" by brainstorming.
Photovoltaic + agriculture, forestry, animal husbandry and fishery constructs a three-dimensional pattern of power generation above and cultivation and breeding below. Fields, mountains, grasslands, ponds, the land of Shenzhou is more green. Talatan, Gonghe County, Hainan Prefecture,
Qinghai Province, has the largest photovoltaic power generation base in China, covering an area of 609 square kilometers, which is close to Singapore's land area. Here, electricity is generated on the board and sheep are herded under the board. "Photovoltaic sheep" eat the weeds that grow luxuriantly under the photovoltaic panels. Photovoltaic parks do not need to hire people to remove weeds, herdsmen also save sheep's "rations", photovoltaic enterprises and farmers and herdsmen win-win!
In addition to "photovoltaic sheep", there are "photovoltaic fish". In Honglin Town, Xuancheng City, Anhui Province, the 100 MW photovoltaic composite project generates photovoltaic power on the board, and the vast water surface under the board is used for breeding fish and shrimp, planting aquatic crops and "fishing-light complementary" operation mode, which greatly improves the value of land use! The direct current generated by
photovoltaic panels can not be directly used by ordinary people, and it needs to be converted into alternating current. How to turn? This requires a device called an inverter. The inverter can invert the direct current generated by the solar panel into 220 volts of alternating current. The next step is how electricity enters the grid.
One is to enter the power grid directly. The electricity generated by photovoltaic power stations with a capacity of less than 8 kilowatts is converted into alternating current by single-phase inverters and then directly enters the 220 volt power grid.
The second is to enter the power grid after boosting. The electricity generated by a small collective photovoltaic power station of 8 kilowatts to 400 kilowatts is converted into alternating current by a three-phase inverter and then enters a 0.4 kilovolt power grid. The power generated by medium-sized photovoltaic power stations of 400 kW ~ 20 MW mostly enters the 10 ~ 35 kV power grid; the power generated by large-scale photovoltaic power stations of more than 20 MW generally enters the power grid of 66 kV and above. In all three cases, the current needs to be boosted to the corresponding grid-connected voltage through the step-up transformer. The boosted AC flows to the substation through the grid-connected point to complete the "Internet access" process, which can be used by millions of households.
But how to make good use of photovoltaic power is also very important. Photovoltaic power generation seems to be inexhaustible. However, it is greatly affected by the weather and is very unstable. In order to consume as much photovoltaic power as possible, our power dispatchers have to put a lot of thought into it. They incarnate as "weathermen" to predict weather changes and make dynamic scheduling plans. For example, when it is sunny in spring and autumn, there is more photovoltaic power generation at noon, so they have to dispatch thermal power to generate less electricity. In rainy weather, when photovoltaic power generation is less, they have to dispatch thermal power units to rush up.
Doing a good job of power dispatching is like playing a big chess game. Power dispatchers should not only be good "weathermen", but also "planners". According to the actual situation, we need to co-ordinate the "exchange of needs" of power grids around the country, and even act as "custodians" to dispatch energy storage power stations to temporarily store photovoltaic power and release it at peak load of power grids.
In the northwest, North China and other places, there are more photovoltaic power, which can not be fully absorbed locally. The dispatcher had to make a big move and make a "big shift of the universe". Photovoltaic power is sent thousands of miles away through the "big country heavy equipment" UHV.
Sunshine and green electricity are infinitely good, and it takes a lot of thought to dispatch online. Behind the continuous flow of green electricity, it is inseparable from the hard work of electric power workers. Please cherish every kilowatt hour and every beam of light!
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