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16-06 2025
Heating and Insulation Technical Solutions for Intelligent Photovoltaic DC Combiner Boxes in Extremely Cold Regions
Abstract
1. Introduction
2. Challenges Posed by Cold Environments
2.1 Electrical Component Performance Degradation
2.2 Battery - Related Issues
2.3 Material Integrity Problems
3. Heating Technical Solutions
3.1 Electric Trace Heating
Principle: Electric trace heating systems consist of self - regulating or constant - wattage heating cables installed on the exterior or interior surfaces of the DC combiner box. Self - regulating cables automatically adjust their power output based on temperature changes, providing more heat when it is colder and reducing power consumption as the temperature rises. Constant - wattage cables, on the other hand, deliver a fixed amount of heat and require external thermostats for control.
Installation: The heating cables are typically wrapped around the box's body, focusing on areas with critical components such as busbars, connectors, and battery compartments. They are secured with heat - resistant adhesive tapes or cable ties and connected to a power supply and control unit.
Advantages: High flexibility in installation, precise temperature control (especially with self - regulating cables), and relatively low power consumption compared to traditional heating methods. It can be easily integrated into existing combiner box designs.
Disadvantages: Initial investment cost for cable installation and control equipment. There is also a risk of cable damage during installation or operation, which may require maintenance.
3.2 PTC Heating Elements
Principle: Positive Temperature Coefficient (PTC) heating elements are semiconductor devices that increase their electrical resistance with rising temperature, thereby limiting the heating power and preventing overheating. When powered, they generate heat and can maintain a relatively stable temperature range.
Application: PTC heating elements are installed inside the DC combiner box, often near sensitive components. They can be embedded in heat - conducting plates or attached directly to the surfaces of components that require heating.
Advantages: Self - regulating temperature control, high safety due to the inherent overheating protection mechanism, and long service life. They are compact and can be easily customized for different box sizes.
Disadvantages: Limited heating capacity compared to some other methods, and the heating performance may be affected by the ambient temperature and ventilation conditions inside the box.
3.3 Waste Heat Recovery Heating
Principle: In PV power plants, some components such as inverters generate waste heat during operation. This waste heat can be recovered and used to warm the DC combiner boxes through a heat - transfer system, such as a closed - loop fluid circulation or heat pipes.
Implementation: A heat exchanger is installed near the heat - generating component (e.g., inverter). The heat - transfer medium (e.g., glycol - water mixture) absorbs the waste heat and circulates to the DC combiner box, where it releases the heat through another heat exchanger.
Advantages: Energy - efficient as it utilizes otherwise wasted heat, reducing overall energy consumption. It is an environmentally friendly solution with lower operating costs in the long run.
Disadvantages: Complex system design and installation, requiring careful integration with existing plant components. There may be heat - transfer losses, and the system's performance depends on the continuous operation of the heat - generating source.
4. Insulation Technical Solutions
4.1 Insulation Material Selection
Polyurethane Foam: With a low thermal conductivity (around 0.02 - 0.03 W/(m·K)), polyurethane foam offers excellent insulation performance. It can be spray - applied or pre - formed into panels for easy installation around the DC combiner box. Its closed - cell structure also provides good protection against moisture and dust.
Mineral Wool: Mineral wool insulation has a thermal conductivity of approximately 0.03 - 0.04 W/(m·K) and is highly resistant to high temperatures. It is suitable for areas where there may be a risk of heat generation from internal components, providing both insulation and fire protection.
Vacuum Insulation Panels (VIPs): VIPs have an extremely low thermal conductivity (less than 0.005 W/(m·K)). Although they are more expensive, their thin profile allows for space - efficient insulation, making them ideal for compact DC combiner boxes where space is limited.
4.2 Insulation Structure Design
Double - Layer Insulation: A double - layer insulation structure can be adopted, with an inner layer of high - performance insulation material (e.g., VIPs) and an outer layer of more robust material (e.g., polyurethane foam) for mechanical protection. This design maximizes insulation efficiency while safeguarding the inner insulation layer.
Sealing and Joint Treatment: All joints, openings, and penetrations in the insulation layer must be carefully sealed using weather - resistant sealants and insulation tapes. This prevents cold air infiltration and heat leakage, ensuring the integrity of the insulation system.
5. Intelligent Control Systems
5.1 Temperature Monitoring and Control
Sensor Deployment: Temperature sensors (e.g., thermocouples or digital temperature sensors) are strategically placed inside the DC combiner box, especially near critical components. These sensors continuously monitor the internal temperature and transmit data to a central control unit.
Adaptive Heating Control: The control unit uses pre - set temperature thresholds to activate or deactivate the heating systems. For example, when the temperature drops below -20°C, the electric trace heating or PTC elements are turned on, and as the temperature rises above -10°C, they are gradually turned off to maintain an optimal temperature range.
5.2 Energy Management
Smart Power Allocation: The intelligent control system can optimize the power consumption of the heating systems based on real - time weather forecasts, ambient temperature data, and the overall power generation status of the PV plant. During periods of high solar irradiance and relatively mild temperatures, the heating power can be reduced or even turned off to save energy.
Remote Monitoring and Diagnosis: Through a wireless communication module (e.g., 4G, LoRa), the control system can transmit temperature data, heating system status, and any fault alerts to a remote monitoring center. This enables operators to quickly detect and address issues, improving the maintenance efficiency of the DC combiner boxes.
