Highly Selective Black Solar Absorbing Coating: The Core Technology For Improving The Efficiency Of Solar Panelsintroduction

In the field of solar thermal utilization, the performance of the absorption coating directly determines the energy conversion efficiency of the entire system.As the core material of photothermal technology, the highly selective black solar absorbing coating realizes the efficient absorption of solar radiation and effective suppression of thermal radiation through its unique optical characteristics, and becomes a key factor to improve the performance of solar collectors.This coating not only has a deep black appearance, but more importantly its excellent optical selectivity, which makes it play an irreplaceable role in the solar thermal utilization system.

I. Technical Principles and Characteristics

The highly selective black solar absorbing coating is a kind of functional material with special optical properties. Its core principle is to have a high absorption rate in the solar radiation band (0.3-2.5μm), while maintaining a low emissivity in the thermal radiation band (2.5-25μm). This selective absorption characteristic is achieved through meticulous material selection and structural design.

Optical performance characteristics

The absorption rate (α) of high-quality, highly selective black absorption coating can reach 0.95-0.97, the emissivity (ε) can be as low as 0.05-0.07, and the optical performance ratio (α/ε) can exceed 15. Under the AM1.5 standard solar spectrum, its photothermal conversion efficiency exceeds 90%, which is 25-35% higher than that of ordinary coatings. The deep black appearance of the coating is not only aesthetically pleasing, but more importantly, this color feature reflects its excellent optical absorption properties.

Thermal stability performance

After 1,500 hours of high-temperature aging test at 300℃, the performance degradation rate was less than 4%. After being tested for 2000 hours in a humid and hot environment of 85℃ and 85% relative humidity, the coating showed no peeling or discoloration, demonstrating outstanding environmental adaptability. The salt spray resistance reaches 1200 hours without corrosion, making it suitable for use in various climatic conditions.

Ii. Preparation Process and Technological Progress

Magnetron sputtering technology

The most advanced preparation process at present is magnetron sputtering technology. By precisely controlling the sputtering parameters in a highly vacuum environment, it achieves film deposition with nanometer-level precision. This process can prepare multi-layer film structures with uniform thickness and precise composition, ensuring the consistency and repeatability of coating performance.

Electrochemical deposition technology

For some application scenarios, electrochemical deposition remains an important preparation method. By optimizing the electrolyte formula and deposition parameters, selective absorption coatings with excellent performance can be obtained. This method has a relatively low cost and is suitable for large-scale production.

Sol-gel method

The emerging sol-gel preparation technology is developing rapidly. This method can prepare selective absorption coatings with nanostructures at relatively low temperatures. It is particularly suitable for substrates of special shapes, providing new possibilities for coating applications.

Iii. Performance Advantage Analysis

Outstanding photothermal conversion efficiency

Compared with traditional coatings, the thermal efficiency of highly selective black absorption coatings is increased by more than 20%. Under the same lighting conditions, the outlet water temperature of the collector with this coating increases by 8-12℃, and the heat gain of the system increases by more than 25%. Especially in medium and high-temperature application fields, its performance advantages are even more obvious.

Long-lasting durability

Accelerated aging tests show that the service life of the highly selective black absorption coating can reach more than 25 years. In the actual usage environment, after 10 years of outdoor exposure testing, the absorption rate of the coating only decreased by 2.8%, the emissivity increased by 1.1%, and the performance degradation rate was far lower than the industry standard requirements.

Good economic benefits

Although the initial investment is 40-60% higher than that of ordinary coatings, due to its higher efficiency and longer service life, the payback period is shortened by 2-3 years. Throughout its entire life cycle, it can generate over 30% more thermal energy and increase the comprehensive economic benefits by more than 50%.

Iv. Application Fields and Case Analysis

Application of flat-plate collectors

In the field of flat-plate collectors, highly selective black absorption coatings have become a standard configuration for high-end products. After a well-known brand of flat-plate collectors adopted this coating, the instantaneous efficiency was increased to 82%, which was 18% higher than that of ordinary products.

Application of vacuum tube collectors

In vacuum tube collectors, a highly selective black absorption coating is applied to the outer surface of the heat-absorbing tubes, significantly enhancing the heat collection efficiency. The vacuum tube collector with this coating adopted in a certain project achieved a system efficiency of 68%, which is 20% higher than that of traditional products.

Integrated Building application

In BIPV/T systems, highly selective black absorption coatings are used to enhance heat absorption efficiency, while architectural aesthetic requirements are ensured through optimized design. Data from a certain demonstration project shows that the system using this coating has an overall efficiency of 75%.

V. Installation and Maintenance Guide

Installation technical requirements

Special attention should be paid to protecting the surface of the coating during the installation process to avoid scratches and contamination. The installation tools should use dedicated equipment to ensure that the coating is not damaged. The installation Angle should be precisely adjusted to ensure the optimal sunlight Angle.

Daily maintenance specifications

Clean the surface of the collector regularly. It is recommended to clean it once every quarter. Use soft materials and neutral cleaners. Avoid using strong acid or strong alkali cleaners. Check the surface condition of the coating and deal with any abnormalities in a timely manner.

Performance monitoring method

Establish a complete performance monitoring system and regularly test the efficiency of the collector. The uniformity of the coating was detected by infrared thermal imager, and the changes in optical properties were measured by spectrophotometer. Establish equipment files to record maintenance history and performance data.

Vi. Technological Development Trends

Material innovation direction

Researchers are developing new types of nanocomposites, such as carbon nanotubes, graphene and other new carbon materials, as well as metal oxide nanostructured materials. These new materials are expected to increase the absorption rate to above 0.98 and reduce the emissivity to below 0.04.

Structural design optimization

The design of multilayer film systems is evolving towards a greater number of layers and more precise thickness control. Better spectral selectivity is achieved through computational optical optimization design. New concepts such as gradient refractive index structure and photonic crystal structure are being explored and applied.

Innovation in preparation process

New processes such as low-temperature preparation technology and roll-to-roll continuous production technology are developing rapidly. These processes can reduce production costs, enhance production efficiency, and minimize environmental impact at the same time.

Vii. Quality Standards and Testing Methods

International standard system

The performance testing and evaluation of highly selective black solar absorption coatings have formed a complete international standard system. It mainly includes ISO 22975 series standards, EN 12975 standards, etc.

Performance testing method

Absorption rate testing usually employs a spectrophotometer with an integrating sphere, while emissivity testing uses a Fourier transform infrared spectrometer. Durability tests include accelerated aging tests such as high-temperature aging tests, damp heat tests, and salt spray tests.

Quality certification system

The Solar Keymark certification is a globally recognized quality certification for solar products. Products that have passed this certification mean that their performance and quality have reached the international advanced level.

Viii. Market Prospects and Opportunities

Policy support intensity

Governments around the world are vigorously promoting the utilization of renewable energy. Solar thermal utilization has been incorporated into the mandatory standards for building energy conservation. Provide tax incentives and subsidy policies.

Market Demand analysis

There is a strong demand for energy-saving renovations in the industrial sector. Promotion of green building standards in the construction industry. There is huge potential for clean energy substitution in rural areas.

Conclusion

High-selectivity black solar absorption coatings, as the core material of solar thermal utilization technology, are driving the entire industry towards high efficiency and long-term effectiveness. Its outstanding performance and significant economic benefits make it the preferred technology for upgrading and replacing solar collectors. With the continuous advancement of material technology and the constant optimization of preparation processes, this coating is bound to play an important role in a wider range of fields. 

We suggest that investors and users pay close attention to the performance parameters and quality certification of the coating when choosing a solar thermal collection system, and select high-efficiency collectors with highly selective black absorption coatings to ensure the best investment return and user experience. For more technical details or product information, please feel free to contact our professional technical team.