The Sun is the closest star to Earth and the one with the most intimate relationship to it, serving as a natural source of energy. Every living organism on Earth owes its ability to function, and even its very survival, to energy directly or indirectly derived from the Sun.
As a new energy source, solar energy has three major advantages compared to conventional energy sources:
First, it is the most abundant energy source available to humankind. It is estimated that the sun has consumed 2% of its own energy over the past 1.1 billion years, making it virtually inexhaustible.
Secondly, solar energy exists everywhere on Earth and can be developed and utilized locally without transportation issues. This is especially valuable for rural areas, islands, and remote regions with underdeveloped transportation.
Third, solar energy is a clean energy source. Its development and utilization will not produce waste residue, wastewater, or exhaust gas, nor will it generate noise or affect the ecological balance.
Our Earth is located approximately 100 million miles from the sun. The amount of radiant energy it intercepts is incredibly small (about three ten-millionths), yet this tiny amount of energy is actually 100,000 times greater than the world's current power generation capacity. Currently, the world, especially industrialized countries, is beginning to feel energy shortages, and therefore, people are turning to solar energy to solve the energy crisis.
Solar energy is a form of radiative energy that we cannot directly utilize. Therefore, sunlight must be converted before it can be used.
The technological fields of solar energy utilization: Humans utilize solar energy in three main technological fields: photothermal conversion, photoelectric conversion, and photochemical conversion, in addition to energy storage technology. Photoelectric conversion mainly involves various types of solar panels and power supply systems. A solar cell is a device that directly converts sunlight into electrical energy. The photoelectric efficiency of solar cells is approximately 10-18%, and their product types mainly include monocrystalline silicon, polycrystalline silicon, and amorphous silicon. Solar cells have a wide range of applications, such as artificial satellites, unmanned weather stations, communication stations, television relay stations, solar clocks, electric fences, black lights, navigation lights, and railway signal lights. Photothermal conversion technology has the most products, such as water heaters, water boilers, dryers, heating and cooling systems, greenhouses and solar houses, solar cookers and high-temperature furnaces, seawater desalination plants, water pumps, thermal power generation devices, and solar-powered medical devices.
Currently, the most widely used application is the conversion of solar energy into electrical energy. The process of directly converting light energy into electrical energy is more accurately called the photovoltaic effect. Without the need for any other mechanical parts, the energy in light is captured by electrons in semiconductor devices, thus generating electrical energy. This energy converter that transforms light energy into electrical energy is the solar cell. Like transistors, solar cells are composed of semiconductors. Their main material is silicon, with some other alloys. The high-purity silicon used to manufacture solar cells undergoes special purification processes. When exposed to sunlight or artificial light, a solar cell can convert light energy into electrical energy, allowing current to flow from one source to another, typically generating electricity equivalent to 10% to 20% of the received light energy.
Combining LED streetlights with solar cells is a prime example of this application. During the day, the solar panels absorb sunlight and store electrical energy; at night or in low-light conditions, they automatically sense the external environment and begin illumination. This eliminates the need for cables and wires required for traditional streetlight installations and utilizes natural energy, eliminating the need for generators. In today's context of sustainable development and low-carbon environmental protection, its significance is profound.
Currently, solar cells have expanded from military and aerospace applications to industries such as manufacturing, commerce, agriculture, communications, home appliances, and public utilities. They are particularly useful in decentralized applications in remote areas, mountains, deserts, islands, and rural areas, saving on the cost of expensive power transmission lines. However, at present, their cost remains high; generating one kilowatt of electricity requires an investment of tens of thousands of US dollars, thus large-scale use is still economically limited.
In the long run, with the improvement of solar cell manufacturing technology and the invention of new photoelectric conversion devices, coupled with the huge demand for environmental protection and renewable clean energy in various countries, solar cells will remain a more practical method for utilizing solar radiation energy, opening up broad prospects for the large-scale utilization of solar energy by mankind in the future.
