Basic knowledge of solar cells

About 30% of the sunlight emitted by the sun into the earth’s atmosphere is reflected back to space, about 24% is absorbed by the atmosphere, and about 46% is absorbed by the ground. According to research calculations, about 157W of solar radiation is received per square meter of ground every day. The energy provided by solar energy to the earth every day is beyond the reach of any energy on the earth, and solar energy will be an inexhaustible and inexhaustible energy source. Since the solar energy was applied to cars in the 1970s, there have been many solar electric car competitions in the world.

Figure 1 shows the basic structure of a solar cell. A P-type semiconductor is formed on the surface of an N-type semiconductor to form a PN junction, that is, a solar cell is formed. The formed P-type layer is only 1~3μm. Sunlight irradiates its surface and reaches the PN junction of the N-type layer through the P-type layer. The electromotive force can be generated, and the generated voltage is about 0.5V. The current of the solar cell is directly proportional to the intensity of sunlight and the area of ​​the solar cell.

Basic knowledge of solar cells
Figure 1 Solar cell structure
Basic knowledge of solar cells
Figure2 Solar cell panel

The shapes of solar cells are round and square. Many solar cells are arranged and combined into solar panels to generate the required high voltage and large current. The conversion efficiency of solar cells is about 10%. Due to the low energy conversion efficiency of solar cells, it is necessary to further adopt new materials and new technologies to improve it. The beaches in California, USA, are sunny and equipped with solar charging stations, which can charge seven electric cars at the same time. Solar charging stations have been widely promoted. In addition to solar cells, solar-powered electric cars need to be equipped with battery packs, motors, controllers, and automatic sunlight tracking systems.

Solar cells include amorphous silicon, monocrystalline silicon and polycrystalline silicon. Generally, a monocrystalline silicon battery panel group with strong conversion capability is installed on the roof of a solar electric car. The photoelectric conversion rate of the battery panel group can reach 14.9%~15.2%, which can generate a voltage of 166~175V, a current of 2.3~2.5A and 360~380W power. According to 8 hours of sunshine every day, solar electric cars can obtain 2.5~3kW·h of electric energy, which can be used for solar electric cars to drive 40~60km, and the maximum speed can reach 60~80km/h.

The titanium dioxide solar cell researched by Mikhail Gretzell of the Federal Institute of Technology in Zurich is to coat a photosensitive layer on a titanium dioxide film. The electrolyte outputs current.

The key technical equipment of solar electric cars is solar panels. At present, because the conversion efficiency of silicon crystal solar cells is relatively low, the electric energy that can be provided is relatively small, so solar panels occupy a large area and must be installed in solar electric cars. The top of the car is shown in Figure 3, and most solar-powered electric cars can only carry one driver. Since the energy of solar cells is small and affected by the weather, the conversion efficiency of solar cells decreases or stops conversion at night, cloudy, or rainy. Therefore, solar electric cars and batteries form a solar hybrid electric car.

Basic knowledge of solar cells
Figure 3 Solar electric car

Solar hybrid electric cars convert solar energy into electricity by solar panels, and then charge the power battery pack through a charger. The solar panels can also provide electricity directly. This method has the highest efficiency, and then the current is delivered through a current converter. The drive motor drives the drive system to drive the solar hybrid electric car. Its drive mode is equivalent to a series hybrid electric car, and an intelligent control system is generally used to control its operation.

As long as the solar panels of solar-powered electric cars can be illuminated by the sun, they can continuously convert solar energy into electrical energy and continuously charge the battery to obtain electrical energy free of charge. It is a kind of low price, zero pollution, and no choice The ideal energy for exhaustion. Solar panels have high cost, low energy conversion efficiency, and occupy a large area. It is difficult to install the whole car, which are the shortcomings of current solar electric cars.