Principles of Solar Energy

Solar energy refers to the radiant energy of sunlight. There are two ways to use solar energy: passive utilization (photothermal conversion) and photoelectric conversion. Solar power generation is an emerging way of using renewable energy. Solar energy in a broad sense is the source of many energies on the earth, such as wind energy, chemical energy, water potential energy and so on.

The main methods of using solar energy are:

* Use solar cells to convert the energy contained in sunlight into electrical energy through photoelectric conversion

* Use solar water heater to heat water by sunlight

* Use the heat of sunlight to heat water, and use hot water to generate electricity

* Desalination of seawater using solar energy

The principle of solar energy is very complicated. Generally, semiconductors can be used to realize photoelectric conversion. And now the conversion efficiency is getting higher and higher.

At present, the use of solar energy is not very popular. The use of solar power to generate electricity still has the problems of high cost and low conversion efficiency, but solar cells have been used in providing energy for artificial satellites.

At present, the world's largest rooftop solar panel system is located in Buerstadt, southern Germany, with an area of ​​40,000 square meters and an annual power generation of 4.5 million kilowatts.

The system that generates electricity using the principle of solar energy is composed of a solar battery pack, a solar controller, and a storage battery (group). If the output power is 220V or 110V, you need to configure an inverter. The role of each part is:

(1) Solar panel: The solar panel is the core part of the solar power generation system and the most valuable part of the solar power generation system. Its role is to convert the sun's radiation capacity into electrical energy, or send it to the storage battery to store it, or promote the load to work. The quality and cost of solar panels will directly determine the quality and cost of the entire system;

(2) Solar controller: The role of the solar controller is to control the working state of the entire system, and play the role of overcharge protection and overdischarge protection for the battery. Where the temperature difference is large, a qualified controller should also have the function of temperature compensation. Other additional functions such as Light control switch and time control switch should be optional for the controller;

(3) Accumulators: Generally lead-acid batteries. In small and micro systems, nickel-metal hydride batteries, nickel-cadmium batteries, or lithium batteries can also be used. Its role is to store the electrical energy emitted by the solar panel when there is light, and then release it when needed.

(4) Inverter: In many occasions, it is necessary to provide 220VAC, 110VAC AC power. Because the direct output of solar energy is generally 12VDC, 24VDC, 48VDC. In order to provide power to 220VAC appliances, it is necessary to convert the DC power generated by the solar power generation system into AC power, so it is necessary to use a DC-AC inverter. In some occasions, when a load with multiple voltages needs to be used, a DC-DC inverter is also used, such as converting 24VDC power into 5VDC power (note that it is not a simple step-down)

The principle of solar energy can be divided into 2 types:

1. Solar photovoltaic

A photovoltaic panel assembly is a power generation device that generates direct current when exposed to sunlight. It consists of thin solid photovoltaic cells made almost entirely of semiconductor materials (such as silicon). Since there is no active part, it can operate for a long time without causing any loss. Simple photovoltaic cells can provide energy for watches and computers. More complex photovoltaic systems can light houses and power the grid. Photovoltaic panel components can be made in different shapes, and the components can be connected to generate more power. In recent years, photovoltaic panels have been used on rooftops and building surfaces, and even as part of windows, skylights, or shielding devices. These photovoltaic installations are often referred to as photovoltaic systems attached to buildings.

2. Solar thermal energy

Modern solar thermal technology aggregates sunlight and uses its energy to produce hot water, steam, and electricity. In addition to using appropriate technology to collect solar energy, buildings can also use the light and heat of the sun by adding appropriate equipment, such as huge south-facing windows or using construction materials that can absorb and slowly release the solar heat. .