- Sun Simulation Tester
Solar simulation testers (also known as solar simulators, or I-V test systems) are mainly used to test the electrical properties of solar cells or components. By testing the volt-ampere characteristic curve of the solar cell or module, and performing analysis and calculation, the maximum power Pmax, the maximum power point current lmpp, the maximum power point voltage Vmpp, the short-circuit current ISC open-circuit voltage VOC, the fill factor FF (Fill factor), Photoelectric conversion efficiency Eff, series resistance Rs, parallel resistance Rsh and other parameters, these parameters can reflect the electrical properties of solar cells or modules, not only can be used for the production process research of solar cells or modules, but also for the power of solar cells or modules. rating. Therefore, a reliable solar simulator not only has guiding significance for the improvement of the production process, but also relates to the quality of the product and the profit and reputation of the manufacturing enterprise.
- Test principle of solar simulator
The solar simulator is used to test the I-V curve of photovoltaic modules or cells. It mainly records the relationship between the output current and the output voltage when the load changes under the determined operating temperature, the determined incident spectrum and the irradiation intensity of the tested sample. , the equivalent schematic diagram of the test principle is shown in Figure 1. The common IV test system is mainly composed of optical system, electronic load, control circuit, computer, data acquisition system and other functional modules. The structure of a typical I-V test system is shown in Figure 2.
A typical IV curve is shown in Figure 3. The key test parameter is short circuit current IISC. , the open circuit voltage Voc peak power PMAX, the best operating point current Impp, the best operating point voltage Vmpp, other filling factor FF, conversion efficiency η, series resistance R, and parallel resistance Rsh and so on.
The optical system of the solar simulator is mainly composed of a light source, a concentrating system, an optical integrator, a collimation system, and a matching filter for solar spectral irradiance distribution. The light source (xenon lamp or metal halide lamp) emits light, which is collected by the ellipsoid condenser to the incident end of the optical integrator to form an irradiance distribution, which is symmetrically divided by each channel of the optical integrator, superimposed and then imaged, and then passed through the collimation system and filter to remove stray light to obtain a spectral distribution very close to natural sunlight. Seen from the front of the collimating mirror, the radiation beam comes from a circular field of view located on the focal plane of the collimating mirror, and the diaphragm is like the sun coming from infinity, thus realizing the simulation of sunlight with uniform irradiation. The schematic diagram of the optical system structure of the solar simulator is shown in Fig.
- The light source of the solar simulator
The light source of the solar simulator can be said to be the heart of the simulator, which directly affects the irradiance, spectral range and stability. The light source is generally artificially simulated sunlight. The closer the spectrum is to natural sunlight, the better. The solar simulator is mainly divided into steady light source and pulsed light source according to the type of light source. When the steady-state light source is working, it can output solar simulated light with stable irradiance, which is convenient for the stable measurement work. Therefore, it can also be used in light aging test and hot spot durability test. It is easily affected by temperature during the test. In order to obtain a large irradiation area, a very large optical system and power supply system are required. Therefore, the steady-state light source is generally not used for component testing, but is usually only used for small area testing, such as solar cell simulation. tester.
The pulsed light source can emit light in the form of continuous pulses in a very short period of time (usually milliseconds). The advantage is that the instantaneous power is very strong, and the average power is very small. The requirements for the data acquisition system are relatively high. For high-efficiency solar cell modules, such as PERC cell modules, due to the large capacitance effect, the use of pulsed light sources will bring large test errors.
Two common pulsed light sources are metal halide and xenon lamps. Metal halide lamps are quite different from the solar spectrum in spectral energy distribution, and are generally rarely used. The xenon lamp is a light source that uses xenon discharge to emit light. The continuity of the spectrum is very strong, and the spectral distribution is similar to the solar spectrum, but there are many peaks in the range of 800~1000m, which are several times larger than sunlight, and need to be filtered out with a filter. At present, both solar simulators and large-scale concentrating solar simulators of aerospace systems use xenon lamps as light sources.
At present, some companies are developing LED solar simulators. LED solar simulators are generally of the downward lighting type. There are multiple LED light sources evenly distributed in the light emission area under the component test glass table. For example, 112 LED light sources can be distributed on the simulator test area of 1000mm and 2000mm. But such simulators are technically immature, and only a handful of companies are developing them.
With the rapid development of double-sided cell double-glass modules, some tester manufacturers are also developing double-sided lighting solar simulators to simultaneously apply light sources on the front and back of the modules.
In general, the future development trends of solar simulator light sources mainly include the following aspects: ① The spectral distribution is closer to the standard solar spectrum; ② The uniformity of irradiance is better; ③ The total energy of the irradiance intensity is as close to the real as possible. Solar energy; ④ Continuously adjustable power can be realized. The ultimate goal is to achieve a light source that is closest to the real sun.
According to the position of the light source, the solar simulator can be divided into three types: horizontal side lighting, vertical upward lighting and vertical downward lighting. The components need to be tested in a vertical state, and a long distance is required, so a long darkroom is required. Typical products are PASAN3B, PASAN3C, Delasike products, etc. When vertical downlighting is used, the components need to be tested in a horizontal state. Typical vertical downlighting solar simulator products include single-pulse 4600SLP and 5600SLP from American SPIRE Company and 9A+ from Shaanxi Zhongsen. The vertical lighting simulator has a high requirement on the building height of the test darkroom, which is greater than 8 meters. It is not convenient to replace the lamp tube and maintain it, so it is rarely used.
At present, continuous pulsed lighting solar simulators are usually used in large-scale photovoltaic module testing. If it is used for high-precision laboratory testing, horizontal side lighting solar simulators are used to obtain higher light levels. Intensity uniformity and adjustment to achieve different irradiance.