Nowadays solar power is doing more than ever to help meet energy demands for local power and for feeding power back to the electric grid, and the inverter is one of the most important pieces of equipment in solar power plants. Ventilation cooling can affect inverter efficiency, and then affect the photovoltaic power plant reliability.
What Does a Solar Inverter Do?
With the goal of carbon dioxide emissions, carbon-neutral, and “building a new power system with new energy as the main body”, as the key technology of the sustainable development strategy of renewable energy, the photovoltaic power generation industry has ushered in a leap-forward development opportunity and is gaining unprecedented development. Most countries have successively issued a series of policies to actively support the expansion of the photovoltaic industry. By the end of 2021, the installed capacity of solar power generation on the grid will reach 306 million kilowatts, breaking the 300 million kilowatt mark, and the industry has developed rapidly.
The solar inverter is an inverter dedicated to the field of solar photovoltaic power generation, which converts the direct current generated by the photovoltaic power generation system into the alternating current required for life. The reliability and safety of PV inverters are directly related to the overall smooth operation of the solar power generation system, its conversion efficiency directly affects the power generation efficiency of the solar photovoltaic power generation system, and its service life is directly related to the service life of the photovoltaic power generation system, which ultimately affects the photovoltaic power station project’s return on investment.
At present, the market is mainly dominated by central inverters and string inverters. The power range of central inverters is about 500kW-3MW. They are mainly used in large-scale projects such as ground solar power stations with good lighting conditions; string inverters The inverter is a 20kW-350kW, distributed inverter product type, mainly used in small and medium-sized PV power generation systems which are used for industrial, commercial, and household sectors. In recent years, the voltage of photovoltaic power plants has been developed from a 1,000V system to 1,500V. More photovoltaic modules are connected in series, which greatly reduces equipment, cable, and construction costs, and increases power generation.
The solar inverter is the essential equipment of the PV system. Its main function is to convert the DC from the PV modules into AC that is required by the grid. But in fact, the inverter is not only the inverter but also the safety housekeeper of the photovoltaic power station. The inverter also undertakes the monitoring and protection of the photovoltaic array and the power grid, as well as system-level functions such as protection of the external environment and human-computer interaction.
Do Solar Inverters Need Cooling?
The components in the solar inverter have a rated working temperature. If the heat dissipation performance of the solar inverter is relatively poor, when the solar inverter continues to work, the heat of the components will always be collected inside the inverter, and the temperature will get higher and higher. Excessive heat will reduce the performance and life of components, and then cause the machine to failure.
The solar inverter generates heat during operation, and power loss is unavoidable. Let’s take a 5kW inverter for example, the system heat loss of it is about 75-125W, which impacts the power generation. It is necessary to optimize the solar inverter cooling system design to reduce the power loss.
How To Cool Down The Solar Inverter?
At present, the cooling technologies of inverters include natural cooling, forced air cooling, and liquid cooling. The main application forms are natural cooling and forced air cooling.
- Natural heat dissipation: Natural heat dissipation refers to letting the local heating device ventilate heat to the surrounding environment without using any external auxiliary energy, thereby achieving temperature control, which usually includes three main heat transfer methods: heat conduction, convection and radiation, among which natural convection is the main method, and natural heat ventilation or cooling is often suitable for low-power devices and components that do not require strict temperature control, the heat flow density of the device is not high, and the devices that are sealed or densely assembled are not suitable (or not required) to use other in the case of cooling technology. At present, most of the mainstream single-phase inverters and three-phase inverters below 20kW on the market use the natural cooling method.
- Forced air cooling is mainly a method of forcing the air around the device to flow by means of a solar inverter cooling fan, so as to take away the heat emitted by the device. This method is a simple and effective way to ventilate the heat . This cooling method is best used if the space between components within the part is suitable for airflow or for the installation of local heat sinks. The method of improving the forced convection heat transfer capacity increases the heat ventilation area, and generates a relatively large forced convection heat transfer coefficient on the heat ventilation surface. Increasing the heat dissipation area on the surface of the radiator to enhance the heat dissipation of electronic components has been widely used in practical engineering. In the solar inverter cooling system, heat sinks are mainly used to expand the heat dissipation area of the radiator surface to achieve the purpose of strengthening heat transfer. The choice of the material of the radiator itself has a direct relationship with its heat dissipation performance. At present, the material of the radiator is mainly made of copper or aluminum, and its extended heat exchange surface is made by folding fins/stamping thin fins, and other processes.
In general, the allowable operating temperature rise of electronic devices is between 40-60 °C. In the case of a temperature rise of 60°C, the natural cooling can bear the maximum heat flux density of 0.05W/cm2. When the thermal flux density is larger than 0.05W/cm2, the forced air cooling method by means of a cooling fan is a good choice in terms of both cost and performance. If the thermal flux density continues to rise, other heat ventilation methods such as liquid cooling are required.
Therefore, for wind energy converters of several MW, liquid cooling is generally used;
for centralized photovoltaic inverters of 100KW-1MW, forced air cooling is generally used; for string inverters with power less than 20KW, The best price/performance ratio is the use of natural cooling. When more than 25KW, forced air cooling is the more economical way
What Is The Purpose Of a Fan In Inverter?
Uninterruptible power supply (UPS) cooling fans are essential in keeping electronic components such as the inverter and rectifier cool enough to operate safely. If the internal solar inverter cooling fans don’t work properly, these components run at much higher temperatures, which makes them deteriorate far quicker.
Solar inverter cooling fans are found throughout the inverter in specific places to maintain effective component cooling. In general, the bigger the solar inverter system, the more (and bigger) cooling fans you’ll find.
Solar inverter cooling fans are mechanical by nature and subject to wear and tear. Sealed bearings inside the BLDC cooling fans contain grease which dissipates over time, slowing the fan speed, which in turn creates additional heat and noise. Dust in the atmosphere forces the BLDC cooling fans to work harder to keep air flowing, while component switching inside the solar inverter system generates significant amounts of heat too.
How To Make The Solar Inverter Last Longer?
As a power electronic device, the solar inverter, like all electronic products, faces challenges brought about by temperature. A survey report from the US Air Force Avionics Overall Research Program shows (Figure 2): Among all electronic product failure cases, up to 55% of it is caused by heat. The electronic components inside the solar inverter are also very sensitive to heat. According to the 10-degree rule of reliability theory, from room temperature, the service life is halved for every 10-degree increase in temperature, so the solar inverter cooling system design is very important. There are several tips to efficiently cool a solar inverter:
- The solar inverter itself is a heat source, all the heat must be ventilated in time and cannot be placed in a closed space, otherwise, the temperature will rise even higher. The inverter should be placed in a well-ventilated space and avoid direct sunlight as much as possible.
- When multiple solar inverters are installed together, in order to avoid mutual influence, there should be enough distance between the solar inverters.
- Cavity management: the electronic components most sensible to heat in the solar inverter are op-amps, sensors, electrolytic capacitors, etc. Electronic components like inductors, cables, power switch tubes, etc are relatively resistant to high temperature, and the heat-generating components can be isolated by the method of dividing the cavity. Place the power of heat-generating components, such as inductors, on the outside of the inverter to reduce the heat inside the chassis. In the meantime, an integral shell structure can be adopted, and the radiator and the shell are closely connected, so that the aluminum alloy shell can ventilate heat through two paths, so as to achieve the effect of reducing the temperature of the components and the internal temperature of the inverter, ensuring the reliable performance of the electronic components and the inverter. The longer service life of the inverter.
- Simulation technology of heat ventilation: The thermal condition of the system can be simulated more realistically by using simulation software, and the operating temperature value of each component can be predicted during the cooling system design process, so that the unfeasible inverter structure design can be modified, thereby shortening the design time, reducing the product cost and improving the first-time success rate of the product.
- Application of new heat ventilation materials for radiators: such as steel radiator, aluminum alloy radiator, copper radiator, copper-aluminum composite radiator, steel-aluminum composite radiator, stainless steel radiator, etc.
- New heat pipe cooling technology: Heat pipe is a new type of heat transfer element with extremely high thermal conductivity. It transfers heat through the evaporation and condensation of liquid in a fully enclosed vacuum tube. It uses fluid principles such as capillary suction to play a good role. cooling effect. It has the characteristics of extremely high thermal conductivity, good isothermal performance, heat transfer area on both sides of cold and hot can be changed arbitrarily, long-distance heat transfer, temperature controllable, and so on.
The PV inverter cooling fan is one of the critical auxiliary equipment in the photovoltaic power generation system. Given the large power of the current centralized solar inverter, forced air cooling is usually used. The IP rating of the solar inverters is relatively high, and most solar inverter cooling fans need a high IP rating as well, at the same time, try to ensure a compact structure, energy-saving, and environmental protection. Here are some suitable cooling fans which mostly chosen by solar manufacturers for the solar inverter cooling:
The inverter adopts an excellent cooling system design in terms of heat dissipation to ensure low loss and long service life of the inverter. Among them, the method of natural heat ventilation is used below 17KW, and the heat ventilation method of forced air cooling is used for 17KW and above. The solar inverter cooling fan with protection level IP68 will be used.
The solar power system’s current inverter determines the amount of AC watts that can be distributed for use, e.g. to a power grid. Many of these large solar inverter systems have tailored cooling solutions that can differ from each other (e.g. air cooling vs. liquid cooling) but all methods have their origins in cooling electronics
For cooling the inverter, many factors need to be considered, like meteorological data, environment influence, operation room, etc. After determining the proper scheme to meet the cooling requirement, improvements should be taken to keep a better working condition, Ventilation with cooing fans can reduce the energy cost and ensures the photovoltaic power plant reliability; it is recommended to choose this ventilation scheme.
Shenzhen Minxin Industrial Co., Ltd is an experienced compact cooling fan and blower manufacturer, whose cooling fans and blowers have been widely used for PV inverters worldwide. Our team of professional experts comes with years of experience in cooling fan manufacturing and engineering, which enable us to provide solutions for various applications.
Our fans and blowers have been used a lot as alternatives to models from EBM Papst, Nidec, Delta, Sunon or Sanyo Denki brands, they are widely used by customers in North America and Europe, we are confident that we can help with your projects.
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We provide a bundle of fan cooling system solutions for your PV inverter applications, contact us if you need fast supply of cost-competitive cooling fans.