Part 1: Reliable Testing of Cooling Water Flow Rate and Temperature in Monocrystalline Silicon Production
The photovoltaic (PV) industry chain comprises six segments: silicon material, ingot casting (rod pulling), wafer slicing, solar cells, solar modules, and application systems. It is mainly divided into upstream, midstream, and downstream: upstream consists of silicon material and wafers; midstream consists of solar cells and modules; and downstream consists of power generation systems. In the upstream industry, due to the high conversion efficiency of monocrystalline solar cells, monocrystalline silicon wafers are the most common type on the market. This industry chain utilizes numerous IFM (Information Technology Management) products, including flow, pressure, and photoelectric sensors, as well as RFID, IO-Link, and AS-i products. Below, we will mainly share how to reliably detect the flow rate and temperature of cooling water in monocrystalline silicon production, as shown in Figure 1.
Figure 1 Photovoltaic manufacturing industry chain
Photovoltaic manufacturing industry chain
1. Reliable flow detection ensures cooling requirements for production equipment.
ifm flow sensors are mainly used in the production of silicon wafers and solar cells, such as equipment like single crystal furnaces, slicing machines, and diffusion furnaces. These devices require stable cooling water systems to meet their cooling needs.
For example, the monocrystalline silicon furnace equipment has a complex internal structure, and the production environment for monocrystalline silicon has extremely stringent requirements, such as furnace temperature. If the cooling water supply is not timely, it may cause the furnace to deform, resulting in unqualified silicon crystal products and damage to the equipment. Therefore, it is necessary to reliably monitor the flow rate of water on the main and branch pipelines of the cooling water.
The ifm SV vortex flow sensor is highly favored by users in the photovoltaic industry. When the flow rate is below or above the set switching point, the LED clearly indicates the switching status, facilitating observation by on-site personnel. It features a color display screen that intuitively shows the detected data, and the display direction is rotatable for easy on-site adjustment and installation, as shown in Figure 2.
Figure 2SV vortex flow sensor
This flow sensor can simultaneously detect flow rate and medium temperature, monitoring flow rates up to 100 L/min and fluid temperatures up to 90°C, offering multiple functions and excellent cost-effectiveness. Through IO-Link, engineers can remotely configure parameters for this series of sensors via software, ensuring lossless digital signal transmission. Simultaneously, data can be collected by a computer, bridging the gap to Industry 4.0.
After connecting the ifm SV vortex flow sensor to the IIoT platform moneo, the sensor data can be configured on the platform, such as setting the switching point and configuring the PNP or NPN output mode. The control panel also displays the flow rate, temperature, and switching status of the flow sensor, providing transparency throughout the production process.
Demonstration of the new IIoT platform moneo (as shown in Figure 3)
2. Product characteristics of ifm SV vortex flow sensor
• Integrates flow and temperature detection, offering exceptional value for money;
• Rotatable color display screen for easy on-site adjustment and installation;
• Suitable for water with or without conductivity (deionization);
• LEDs clearly indicate the switch status;
• Remote parameter configuration and lossless digital signal transmission are possible via IO-Link.
Figure 3. Demonstration of the new IIoT platform moneo
Part 2: Tracking and Traceability in Solar Cell Production
With rapid economic growth, energy demand is constantly increasing, making the development and utilization of new energy sources increasingly prominent. Photovoltaics, as a safe, clean, and green energy source, has received close attention and importance. Because the overall production process of the photovoltaic industry is quite complex, reliable and intelligent RFID solutions are needed to achieve efficient operation. Here, we will reveal the tracking and tracing solutions in the solar cell production process.
The production process of solar cells includes: silicon wafer inspection, surface texturing and acid washing, diffusion junction formation, dephosphosilicate glass, etching and acid washing, anti-reflective coating, screen printing and rapid sintering, etc.
1. Split-type RFID products
Ifm's modular RFID products are primarily used in etching and pickling processes. They are installed at both the loading and unloading stations of the etching and pickling equipment. The tags are encapsulated in Teflon baskets containing silicon wafers to be etched and pickled. During loading and unloading, the processing technology and on-site processing data of the tags within the baskets need to be read and written, enabling real-time tracking and tracing, and facilitating visualization of subsequent processing flows.
Because etching and pickling equipment contains pickling tanks that can easily react chemically with metal products, we recommend users use RFID products with all-plastic housings, such as the ifm LF/HF DTE series RFID estimation units shown in Figure 4. All-plastic housing RFID products are more corrosion-resistant and have a high protection level, meeting the requirements of harsh industrial environments.
Figure 4. LF/HF RFID Estimation Unit DTE Series
In the diffusion and knotting stage of the production process, where automation is high and equipment is sophisticated, all-metal products with an ifm M18 interface, such as the HF RFID reader/writer ANT420, can be used. This reader/writer is small in size, making it convenient for customers to install within space-constrained equipment. Furthermore, the all-metal material of the reader/writer provides stronger anti-interference capabilities; even with surrounding metal enclosures, it effectively resists interference, ensuring the reliability of the read and written tag data.
When it is necessary to screen monocrystalline silicon and polycrystalline silicon solar cells, a sorting machine is required. It is a sorting device that uses the principle of air suspension to separate mixed powdery materials into light and heavy components.
During the sorting process, if m provides HF square RFID reader/writer heads, such as ANT513 or ANT600. These can be used to store production data or quality parameters on ID tags, making them ideal for long-distance read/write applications, as shown in Figure 5.
Figure 5. HF RFID Reader/Writer Head ANF513 Series
2. Application Advantages of IO-Link RFID Reader Heads
As technology evolves, IO-Link has gradually integrated into factory automation, greatly simplifying the manufacturing process. It eliminates clutter in control cabinets, employs a plug-and-play design, and ensures lossless signal transmission. The advantages of using IO-Link RFID readers include:
• Multiple device versions suitable for different applications;
• High cost-performance ratio, no additional controller required;
• Enables flexible parameter setting, diagnostics, and data processing via IO-Link;
• Ideal for completing rapid identification tasks with small amounts of data;
• Antenna parameters can be easily read on the IO-Link master station through simple visualization via IODD.
Finally, both split-type RFID and IO-Link RFID will use the same RFID tag. Due to the increasing volume of data in the photovoltaic industry, ifm provides the high-capacity, compact RFID tag E80370 to meet user needs. This tag can store parameters from various stages of the field, offering simplicity and flexibility, as shown in Figure 6.
Figure 6. Small size, high capacity RFID tag
Part 3: Assembling Solar Cells
In the final stage of solar cell manufacturing—the assembly of solar cells—the conveyor line is the most crucial piece of equipment on the automated production line. By connecting different assembly processes of the entire solar panel assembly line in series, the assembly efficiency of solar cells is significantly improved. This allows for the production of large quantities of solar panels, meeting the green energy needs of various industries. These conveyor lines extensively utilize ifm's AS-i bus technology: hundreds or even thousands of I/O signals on the conveyor line are conveniently and quickly connected together and transmitted to the control cabinet via ifm's AS-i bus system.
1. AS-i bus efficiently acquires scattered signals from the transmission line.
The biggest advantage of the AS-i bus is its simple wiring. A single bus serves as both a power line and a signal line, organically connecting the scattered I/O signals on the transmission line. At the same time, this technology also has fault diagnosis capabilities, enabling accurate fault location.
ifm offers a full range of AS-i products, including AS-i gateways, AS-i power supplies, various types and specifications of AS-i field modules, cables, and alarm indicators, to meet diverse field signal acquisition needs and help users eliminate messy cables, simplifying the process. Each AS-i module is a distributed I/O slave station, requiring no additional hardware and can be placed anywhere on the AS-i network for convenient signal acquisition.
It's worth mentioning that all ifm AS-i master stations are equipped with color displays, allowing for direct visual operation via buttons. The display clearly shows the status of all AS-i network signals. This enables direct monitoring of the entire AS-i network signal status in the field via the gateway. This facilitates efficient routine equipment maintenance and accurate fault location.
For field applications, ifm offers various product types. For example, the pneumatic unit module with integrated solenoid valve directly outputs compressed air to control the actuator.
For field transmission lines, ifm also offers compact cabinet modules that are highly favored in the photovoltaic industry. For example, ifm's AC2267 control cabinet module not only saves space but also allows for simple and quick wiring via cage-type spring clips, enabling the acquisition of field signals and their transmission to the control system through the AS-i network.
Figure 7 AS-Interface Control Cabinet Module AC2267
2. Advantages of AS-i bus applications
• Used in control cabinets;
• Simple and quick wiring using cage-type spring clips;
• Specially space-saving design;
• Dual terminals for power cycling;
• A powerful LED display clearly shows the operation, on/off status, and function.
More and more users are integrating AS-i products into their field equipment, which is strongly promoting the automation upgrade of the photovoltaic industry. In addition to the AS-i bus, ifm, with its many years of experience in automation, also provides a wide range of other products for the photovoltaic industry chain, including flow, temperature, photoelectric sensors, RFID, and IO-Link products, to meet the needs of various production stages.
