It is best not to buy those that are too cheap. The polyurethane insulation of the solar thermal insulation bucket is made of high-density foam, so that it can play a thermal insulation role. It depends on the thickness of the material. foam and if it is firm when pressed with your hands, some are not molded in one go, but are painted on the surface again. It will look very dense and smooth when you look at it, so you need to press it with your. hands. You also need to look at the thickness of the stainless steel water tank. It's not easy to see. You have to compare the overall weight. You also need to look at the thickness and surface area of the support. There are many types of vacuum tubes, ordinary solar tubes, three-high tubes and purple gold tubes. Three high tubes and purple gold tubes are good, but it is not easy to judge whether they are good or bad. threehigh "solar core" vacuum tubes and ordinary tubes is that the heat-absorbing film layer is different (the heat-absorbing film layer is a key part of the vacuum tube). The three tubes are interference films and the ordinary tubes are degraded films. Their difference is mainly reflected in the difference between the interference film and the degraded film. 1. Fundamental difference: The structure of the film is different, which results in different principles of absorption of solar rays. The gradient film is a multi-layer film. Its absorption layer is generally composed of 9 layers. It absorbs solar rays layer by layer, and its light absorption performance gradually increases. Due to this gradient structure, the emission rate continues to increase as the temperature increases, so that when the operating temperature is between 300 and 500 °C, the emission rateion increases considerably. In addition, the activity of aluminum ions in the absorption layer is significantly enhanced and drifts at high temperatures. In this way, the internal structure of the film layer becomes disordered, causing the film layer to age. When exposed to this high temperature for a long time, the film layer will fall off, affecting the heat collection efficiency and life of the vacuum tube. The interference film has a total of two absorption layers. Due to the different ratios of metal components between the two films, interference occurs, which increases the absorption rate and decreases the emission rate. Coupled with the effect of the anti-reflective layer on reducing reflection, a higher absorption rate and lower emission rate are achieved, significantly improving the heat collection efficiency. 2. Characteristics: the rate ofThe absorption of the three-tube tube is increased by 12%, the emission rate is reduced by 30%-40%, it is super absorbent, has less heat loss and heats up quickly. High efficiency tubes have super absorption, high thermal efficiency and rapid heating. Under the same lighting conditions, they can produce more hot water at a higher temperature than very cold tubes, because the copper ion emission rate is 0.2 lower; than that of aluminum ions, therefore, the heat loss is very low and it can still work normally in very cold environments. Hot water can still be produced at -30°C, thanks to the special effect, high temperature tubes. the ions in the film layer are resistant to high temperatures and exposure to air, the film layer does not age at 400°C, no attenuation, no fading. Under the same lighting conditions, the thermal absorption of the tubOrdinary tubes are not as high as that of three-dimensional tubes, and they cannot even meet the bathing requirements when the temperature is low, the heat loss is greater, and the heat collection efficiency is greater ; decreases, affecting normal use, especially when air drying exceeds 270°C. The film begins to age and fall off, the absorption rate decreases rapidly, and the service life is significantly shortened. 3. Technology: High-temperature special effects tubes, high-temperature tubes and high-efficiency tubes use three-target, double-target and single-target magnetron sputtering processes, respectively. Ordinary tubes typically use single-target magnetron sputtering processes; 4. Appearance: A. Pipe mouth When the film layer is sealed here at a high temperature above 800°C, it is inevitable that some part will fall off. THEhigh temperature special effects tube is only about 1 centimeter long without film layer because it is resistant to high temperatures, while other tubes are not resistant to high temperatures and are about 2.5 centimeters long when the film layer falls off. B. Inner tube color: Observed by naked eye, the inner tube color of high temperature and high cold tubes is dark red (because the bottom layer of the film layer is copper while high-efficiency tube and ordinary tube are); white (because the bottom layer of the film layer is aluminum).
It should be used for voltage limiting protection. When the solar cell is operating normally, it produces electrical energy. However, if it receives a reverse voltage for any reason (bad wiring, malfunction, lightning strike, etc.), its reverse withstand voltage is very low andit is easy to break down. , so add a parallel diode to limit its reverse voltage so as not to exceed the forward voltage drop of the diode (about 0.7 V), so that the solar cell is not damaged by a breakdown.