China has abundant solar energy resources, and in some places, the radiation intensity reaches 4kWh/m2/day. Remote areas of western China have high levels of solar radiation and are sparsely populated, while the possibility of the main grid extending to the region in the short term is slim. Solar-photovoltaic power generation technology (PV) can provide both small “solar household systems” SHS (peak power 20-50W) for single-family households, and larger village-level systems (about 5kW). So the technology can be used as a technology option in the short term to provide basic energy services to households, small businesses, and communities in rural and remote areas of China.
In China’s northwestern provinces, about two million households still do not have access to electricity. China’s total photovoltaic power generation is 10MWp, of which only 40-50 SHS systems, about 200,000 RMB.
Technology Photovoltaic power generation technology can directly convert light energy into electrical energy. Photovoltaic generators have no moving parts and therefore require minimal maintenance. Of course, the batteries of many systems need to be replaced every 2-5 years. Photovoltaic power generation does not produce greenhouse gases and other substances that pollute the environment. At the same time, the photovoltaic generator operates without noise.
Photovoltaic cells typically consist of two or more semiconductor sheets, and the semiconductor material is usually silicon. When light is illuminated, an electric current can be generated inside the battery and conducted by a metal conductor in the form of a direct current (DC).
The power generation of a single cell is very small, typically only about 1.5W at 0.5V. So multiple batteries are always connected together and encapsulated in a glass shell to form a module battery (battery plate). Such a module battery is not affected by weather conditions and is resistant to wind and rain. Under the condition of 12V DC voltage, the single module battery can completely generate 10-80Wp of electrical energy output.
The current and power output of the module battery is roughly linear with the received sunlight intensity, but the operating voltage decreases with the increase of the battery temperature. Therefore, the module battery reaches its maximum power output around noon when the sun is shining and the temperature is low. Of course, even in cloudy weather where lighting conditions are not very good, there will still be a certain amount of electrical energy output. According to the performance test in the 1000W/m2, 25°C standard test environment, the output power of the module battery is usually expressed in the form of peak power (Wp, Watts Peak). It should be noted that because the actual light level is usually not up to the level at the time of the test, the actual output power of the module battery is not large enough to be rated for most of the time. In western China, module batteries operate at an average of 25% of their rated power throughout the year.
The photovoltaic cell module is the basic unit for building photovoltaic power generation systems. Any number of module batteries can be connected to achieve the required electrical energy output. This is a major advantage of photovoltaic power generation systems. When the existing system capacity needs to be expanded, only the number of module batteries needs to be increased.
Module batteries or arrays of module batteries must be installed at heights to ensure adequate sunlight exposure and no obstructions. Obstruction occlusion will severely affect the power output of the module battery.
The standalone SHS consists of a small 10-20Wp module battery and is equipped with a distribution box and transmission cable. It is suitable for areas not covered by the transmission grid. The simplest SHS provides electrical energy that can make 1 to 2 low-pressure mercury lamps work 2 hours a day. Larger SHSs can provide electrical energy for TV or radio work.
A centralized optical volt system can power an entire village through a small transmission grid. A standard photovoltaic array system can not only provide lighting and television electricity for 100 homes but also supply the electricity needed for street lights and public buildings. Such systems are often equipped with converters to ensure that the standard currency of the trunk is distributed to the various end-users.
Village-level light-volt systems are usually also equipped with backup power sources, such as diesel generators. This improves the stability and practicality of the system and reduces the need for large-capacity batteries. Such systems are often referred to as photovoltaic/diesel power generation complementary systems.
China’s photovoltaic power generation industry and market conditions
In 1998, China’s solar cell output reached 2.1MWp, equivalent to 1.3% of the world’s total output. In the same year, the total installed capacity of photovoltaic power generation reached 12MWp, equivalent to 1.5% of the world.
China’s current solar cell production capacity is only 0.4-0.6MWp/ year, less than the rest of the world’s 5-20MWp / year average production capacity of 1/10.
The average battery efficiency in China is between 10% and 13%, which is equivalent to 98% of the same level in other countries. The quality of photovoltaic cell raw materials such as silver salt and packaging glass needs to be improved urgently.
The production cost of battery components in China is still very high, the unit power generation cost is about 35 yuan / Wp (4.2 US dollars / Wp), and the average sales price is 44 yuan / Wp (5.3 US dollars / Wp).
China has 70 million people living in areas without electricity, and the energy demand of this part of the population has formed a huge potential market for photovoltaic power generation. However, the development of the photovoltaic power generation market is still rarely supported by policies and regulations.
The future development trend
from 1987 to 1997, China’s photovoltaic power generation industry annual growth rate reached 15%. By 1998 reached a maximum annual growth rate of 30-40%. It is estimated that with the introduction of various incentive policies such as tax relief policies, fiscal preferential policies, and green lighting electricity prices, China’s photovoltaic power generation will continue to maintain strong momentum of growth.
The average construction cost of a photovoltaic system in 1996 was $7/Wp, which is expected to fall to $3/Wp in 2010. At the same time, the unit generation cost will be reduced to $0.11/kWh. By 2010, system construction costs will continue to fall to $1.7/Wp and power generation costs to 6 cents/kWh.
After entering the 21st century, the production scale of photovoltaic power generation system components will be 5-20MW/year to 100MW/year, or even higher. The efficiency of monocrystalline silicon cells will be increased by 18%-20%, while the efficiency of polycrystalline silicon cells will be increased by 16%-18%.
The construction of photovoltaic power generation facilities will become an aspect of architectural design in the future. At the same time, the pace of grid-connected power generation will increase rapidly.