1.The principle of solar photovoltaic power generation
Voltaic power generation is a form of power generation where semiconductor materials and devices are exposed to sunlight, and light energy can be converted into electrical energy. The history of solar photovoltaic power generation can be traced back to the late 1830s. French scientist Becquerel discovered that direct sunlight on semiconductor materials can cause potential differences between different parts of the semiconductor. Later, scientists used experimental methods to convert this potential difference into usable electricity. This phenomenon is known as the “Photovoltaic effect”, which we refer to as the “photovoltaic effect” in this article. The technology of using this effect to generate electricity emerged based on the continuous exploration of scientists. In 1839, scientists began to develop solar photovoltaic cells, using silicon as the first semiconductor material. Silicon photovoltaic cells were born in 1954 at Bell Laboratories in the United States, which means that solar photovoltaic power generation technology, which converts solar energy into electricity, was born. The basic principle of solar photovoltaic power generation is relatively simple, summarized as follows:
Under normal conditions, the diffusion of most charge carriers occurs on both sides of the PN junction in semiconductors. The specific action is for electrons in the N region and holes in the P region to expand towards each other’s positions. The result of this action is the generation of a relatively narrow space charge region near the PN junction of the semiconductor and the generation of its own electric field. Next, the electric field will exert a force on the charge, which will block the diffusion of electrons and holes. At the same time, a few charge carriers will use the presence of the space electric field to generate a traction action, quickly transferring to the corresponding region to achieve dynamic equilibrium of the force. However, due to the small number of charge carriers that do not generate sustained current, there is no available electrical energy; But when sunlight shines on semiconductor materials, photons collide with atomic valence electrons at the PN junction, causing electron hole pairs to lose balance. As a result, photo generated non-equilibrium carriers continue to diffuse under the influence of the spatial electric field – non-equilibrium electrons in the P region diffuse to the N region, and non-equilibrium holes in the N region transfer to the P region, resulting in excess carriers in both P and N regions, Furthermore, a photo generated electric field will be formed near the PN junction in the opposite direction to the original spatial electric field. The generated photo generated electric field not only cancels out the original electric field, but also establishes a new electric field, which is manifested in the positive charge in the P region and negative charge in the N region of the semiconductor material, which is the potential difference mentioned earlier. By connecting the semiconductor with an external circuit through experimental methods, a circuit will be formed to output electrical energy. The application of solar photovoltaic cells in production is achieved through the series and parallel connection of multiple battery units, which converts solar energy into electrical energy.
2. Household solar photovoltaic power supply system
The household solar photovoltaic power supply system is a specific application of household solar photovoltaic power generation technology. At present, household solar photovoltaic power systems generally refer to off grid solar photovoltaic power systems, mainly composed of solar panels, battery packs, controllers, related controllers, current inverters, circuit protection parts, and other components. The common household solar photovoltaic power sources in the market include “solar power household version” and “portable photovoltaic power supply”. The specific application of these two types of solar power sources depends on the characteristics of the power source usage. The household version is used in areas with strict power requirements and high electricity consumption levels. Portable solar photovoltaic power sources are mainly used in mobile work environments. The use of solar photovoltaic power can effectively reduce carbon emissions, which is also in line with relevant national policies on the use of new energy and should be vigorously promoted.
3. Main components of household solar photovoltaic power supply systems
3.1 Solar cell modules
Solar cell modules are composed of multiple solar photovoltaic cell units combined in series and parallel, and they are the main component of all solar power sources. Solar cell units cannot directly provide electricity because: single solar photovoltaic cells have lower mechanical strength and are prone to damage; Single solar cells that come into direct contact with air are prone to corrosion; Due to the limitations of semiconductor materials, the output power of individual batteries is relatively low, which cannot meet the production applications of daily life. The above reasons require us to connect and package individual cells when producing solar photovoltaic household power supplies, so that the solar photovoltaic power supply battery pack produced can not only effectively prevent corrosion and damage, but also provide sufficient electrical power.
Based on the specific characteristics of the household environment, the corresponding power components should have the following characteristics:
(1) The mechanical strength must be guaranteed, able to withstand certain impacts and vibrations, and avoid malfunctions during installation.
(2) Has a certain adaptability to external natural conditions such as temperature, humidity, etc.
(3) It can prevent the influence of radiation and other conditions, and has good insulation performance.
(4) Simple operation and long working life.
(5) Capable of outputting power through simple operations and adapting to different voltage requirements.
In addition to the many characteristics mentioned above, from a production perspective, while ensuring production quality, the packaging and other aspects of the power pack should not consume too much capital investment.
3.2 Battery
If the electricity generated by solar photovoltaic modules is directly used for production, unstable situations such as current and power will occur, which will cause great damage to production equipment. Given this situation, batteries are used in conjunction with household solar photovoltaic power systems. A battery is a device that stores the electrical energy converted from solar photovoltaic modules in the form of chemical energy. When electrical energy is needed, the chemical energy is released, and the battery can deliver stable electrical energy to the electrical circuit. In household environments, batteries are often subjected to frequent charging and discharging processes, which can have a certain impact on their lifespan. In addition, batteries in household solar photovoltaic power sources will not completely discharge, which poses new requirements for batteries.
Summarize the characteristics of batteries in household solar power systems as follows:
(1) Capable of adapting to frequent charging and discharging situations in household environments, with good cyclic electricity performance.
(2) Has a longer cycle life.
(3) Easy to maintain.
(4) Not sensitive to high temperatures, able to charge and discharge normally under low temperature conditions.
(5) High energy utilization rate and high cost-effectiveness.
3.3 Controller
The function of the controller is to control the charging and discharging points of the battery in the solar photovoltaic power supply, which plays an important role in the operation and lifespan of the battery. Secondly, the controller also plays a role in controlling the voltage, current distribution, and power size of the entire solar cell system. In household solar power systems, the controller should have corresponding protection functions, summarized as follows:
(1) Provide short circuit protection for load circuits in solar powered household power supplies.
(2) Effectively protect the stability of the internal circuits of the entire system.
(3) Has a certain degree of reverse protection capability.
(4) Protect the stability of the entire system under special conditions, such as lightning weather and polarity reversal.
(5) Can display the storage status of energy in the battery.
3.4 Inverter
Most devices in daily life use 220V, 50Hz AC power, and the current generated by solar photovoltaic power generation technology is DC power. Therefore, inverters are added to household solar power systems. The function of the inverter is to convert the DC power provided by the battery into AC power for household use, thereby widely applying solar power systems in practice. When selecting an inverter, in addition to considering that the battery can generally only provide voltages of 12V, 24V, and 48V, it should also consider the requirements for output voltage and current power in practical applications. In addition, as the most direct part of the power system and load circuit, the inverter should also have certain load carrying capacity, protection ability, and insulation ability. When dealing with different working environments, inverters should also have certain adaptability to ensure the stability of solar photovoltaic power supply.
4. Prospects for the application of solar photovoltaic power generation technology
As mentioned earlier, the application of solar photovoltaic cells belongs to the category of new energy, which is strongly advocated in our country. Solar energy, as a clean energy source, has been highly valued and has made some progress in the power industry, and solar photovoltaic power generation technology has also received special attention. Since the 20th century, the country has focused on developing solar power generation technology as a key project. Since 1997, global solar cells have increased at an annual growth rate of 30%. In the new century, with the rapid development of various industries, the demand for electricity is also increasing day by day, and solar photovoltaic cell products are beginning to experience a shortage of supply. Of course, the development progress of solar photovoltaic power generation varies in each country and region, but overall it maintains a rapid development state. We have reason to believe that the application of solar photovoltaic power generation technology will be more widespread in the future.
China strongly advocates solar photovoltaic power generation, partly because the country’s resource situation is not optimistic. Traditional energy sources such as coal and oil alone cannot meet China’s development needs. In addition, fossil fuels will bring huge pressure to the environment and affect human quality of life. New energy is the best choice for China’s development. As a representative of new energy, solar energy resources have undoubtedly gained development first.
5. Conclusion
The application of household solar photovoltaic power generation technology will become increasingly widespread, which is certain. However, there are still many problems that need to be solved in the development process of solar photovoltaic power generation technology, and there are still many aspects that need to be improved. In addition, China’s development urgently needs more perfect solar photovoltaic power generation technology. Therefore, relevant personnel in our country still need to make efforts to explore and research, so that solar energy resources can better serve humanity.