Solar energy, as an "inexhaustible, inexhaustible" source of energy, is universal, safe, harmless, immense, and long-lasting. It is now widely used in people's lives, such as solar water heaters, solar air conditioners, Solar lighting, etc., and these also need another solar energy product - solar cells, as a kind of electrical equipment that can convert solar energy from light energy into electrical energy and preserve it, and other battery devices have the following advantages:
(1) The sun shines on the earth. There are no geographical restrictions. Irrespective of land or sea, mountains or islands are everywhere, and they can be directly developed and used without the need for mining and transportation. Solar cells can directly convert solar energy into electricity.
(2) The use of solar energy to generate electricity will not be like firepower and hydroelectricity, it will not pollute the environment, and it will not block rivers. It is one of the cleanest energy sources. Today, as environmental pollution and water scarcity become more and more serious, this One point is extremely valuable, and solar cells can effectively convert solar energy into electrical energy to preserve it.
(3) The annual solar radiation reaching the Earth's surface is equivalent to about 130 trillion tons of coal, which is the largest amount of energy that can be developed in the world today. This provides solar cells with sufficient energy power.
(4) According to the current estimate of the nuclear energy rate produced by the sun, the hydrogen reserves are sufficient for the maintenance of billions of years, and the life span of the earth is also several billion years. In this sense, it can be said that the energy of the sun is not used. Exhausted, can develop a broad and long-term space for solar cells.
The growth of the solar industry has increased the demand for solar cell test and measurement solutions, and as the size of solar cells increases and the efficiency increases, battery testing requires the use of higher currents and higher power levels, which requires the use of more Flexible test equipment.
It is usually necessary to measure several key parameters of solar cells. These parameters are mainly:
â— Open circuit voltage. The battery voltage when the current is equal to zero.
â— Short-circuit current. When the load resistance is equal to 0, the current flowing from the battery.
â— The maximum power output of the battery. The battery output voltage and current value at maximum power.
â— The battery voltage.
â— The current value of the battery.
â— Battery series resistance.
â— Battery shunt resistance (or shunt resistance).
Common solutions
Currently, there are two main forms of solar cell test solutions: a complete turnkey system and a universal test instrument.
If you need to test when the solar cell's maximum output power, many research laboratories have a low-power four-quadrant power supply (sometimes called SMU), and have the following features:
â— Provide accurate positive and negative voltages ("provided" may also be referred to as "application").
â— Provides accurate forward and reverse currents (providing reverse current is also referred to as current flowing into the power supply).
â— Accurately measure the voltage and current of the device under test (DUT) (measurement is also called detection).
Most high-precision four-quadrant power supplies can only provide 3A of current or 20W of continuous power.
These maximum currents and powers are acceptable when testing a single, smaller cell, but as the cell technology advances toward greater efficiency, greater current density, and larger cell size, the cell's power output will be very fast. It will exceed the maximum ratings of these four-quadrant power supplies. The output of solar modules typically exceeds 50W and may climb to 300W or higher, which means that many tests for modules cannot be completed using four-quadrant power supplies.
In these cases, engineers should rely on off-the-shelf electronic loads, DC power supplies, DMMs, and data acquisition equipment, including temperature measurement, scanning, conversion, and data logging equipment, to allow for flexible and unique testing within a wide operating range, and Achieve the desired test accuracy. For example, a data acquisition system can be used to scan the environment and the temperature of the device under test, the voltage of the calibrated reference battery, and various other test parameters that need to be captured in the test.
For solar cell testing, the standard electronic load can be used to test solar cells.
Considering that solar cells generate energy, when using a four-quadrant power supply to test it, the actual operating mode of the power supply is: The solar cell applies a positive voltage at the terminals of the power supply. At the same time, current flows from the solar cells into the terminals of the four-quadrant power supply, which means that the four-quadrant power supply sees a reverse current (in terms of its terminals). Under these conditions, the four-quadrant power supply can also be referred to as the "power sink."
Electrically speaking, an instrument that has a positive voltage across it and current inflow (ie, reverse current) is called an electronic load. Therefore, for most solar cell tests that have light and solar cells generate energy, the four-quadrant power supply actually acts as an electronic load.
The advantage of using an electronic load is that this load can be used at various current and power levels. The 3A, 20W limit imposed by a four-quadrant power supply can be easily overcome with an electronic load rated at 50W or as high as several kilowatts and hundreds of amps.
The electronic load can work on solar cells under constant voltage, constant current, constant resistance, and constant power modes. For example, in the constant voltage mode, the electronic load can adjust the current flowing through itself to adjust the voltage across it to maintain a constant voltage value. Therefore, constant voltage mode can be used to create a voltage sweep, use the load to control the voltage at the output of the solar cell, and then measure the resulting current.
Some loads (such as Fission's FT6600A series) can quickly perform a series of CV positioning points to scan the output voltage in CV mode to quickly delineate the IV curve. At the same time, the load can digitize the current waveform flowing from the solar cell into the load, similar to capturing oscilloscope curves.
The Fischer FT6600A can perform long-term test record calculations for solar cells, such as battery charge and discharge test records, internal resistance calculations, and capacity calculations; electronic loads have strong program control functions and human-machine interfaces, usually with a color graphic display interface and GPIB interface
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