Solar Absorber Panel Core: The Efficient "Heart" Of Flat-Plate Collectors

In the interior of the flat panel solar collector, there is a core component that determines the performance of the whole system, the Absorber Plate. This metal plate, which is usually deep blue, is the "heart" of solar thermal conversion. Its performance directly determines the efficiency, lifespan and reliability of the collector.This paper will deeply analyze the structure design, material technology, performance index and the key impact on the system efficiency.

I. Function and Status: Why is the Core Board So Important?

The absorption board core undertakes three core missions: 

1. Maximize solar energy capture: Absorb solar radiation energy through a special surface coating 

2. Efficient conversion of heat energy: the light energy is converted into heat energy and transferred to the heat transfer medium

3. Minimize heat loss: Reduce heat loss through structural design and material selection

The performance of the core board directly determines the instantaneous efficiency curve and total heat of the collector, and is a key factor affecting the return on investment of the system.

Ii. Core Structure and Working Principle

Modern high efficiency absorber core usually adopts laminated composite structure:

1. Heat-absorbing film layer (upper layer 

Magnetron sputtering technology on preparation of selective absorbing coating

Absorption rate α > 0.95, emissivity ε < 0.05 

It has strong weather resistance and can withstand temperatures above 200℃ 

2. Flow channel System (middle layer 

It is formed by laser welding of copper tubes/copper strips or aluminum tubes/aluminum strips 

The flow channel design optimizes heat transfer efficiency and flow resistance 

The pipe spacing and diameter have been optimized through thermodynamic calculations 

3. Substrate material (lower layer) 

Commonly used are 1060 or 3003 aluminum alloy plates 

The thickness is usually 0.3 to 0.5mm 

It has good thermal conductivity and corrosion resistance 

Working process: Sunlight → Selective absorption coating → Thermal energy → Substrate → Flow channel → heat transfer medium

Iii. Key Technical Parameters and Performance Indicators

1. Optical performance 

Absorption rate: > 0.95 (AM1.5 standard spectrum) 

Emissivity: < 0.05 (at 80℃) 

2. Thermal performance 

Heat transfer efficiency: > 0.78 (under critical temperature conditions) 

Heat loss coefficient: < 3.5W/m²K 

3. Mechanical properties 

Pressure resistance capacity: ≥1.0MPa 

Bonding strength: ≥30N/cm² 

Fatigue resistance cycle: > 5000 thermal cycles

Iv. Comparison of Mainstream Technology Types

1. Tube sheet structure (mainstream) 

Copper tube-copper plate structure: ultrasonic welding or laser welding

Copper tube - aluminum plate structure: Utilizing hot-rolled composite or explosive composite processes 

Aluminum tube - aluminum plate structure: Fully aluminum welded, with a relatively low cost 

2. Serpentine tube structure 

Bending and forming of a single metal pipe 

The flow resistance is small, but the efficiency is slightly lower 

3. Embossed panel structure 

The runner is pressed onto the metal plate through a mold 

It has a low cost but poor pressure resistance 

4. Performance comparison table 

Type, thermal efficiency, pressure-bearing capacity, cost, applicable scenarios

Copper tube - copper plate height (0.78-0.82) height (1.0MPa) high-end engineering

Copper tube - aluminum plate medium height (0.75-0.78) medium height (0.8MPa) general engineering

All-aluminum structure medium (0.70-0.75) medium (0.6MPa) low household system

V. Manufacturing Process and Quality Control

1. Welding process 

Laser welding: High precision, small heat-affected zone 

Ultrasonic welding: No penetration depth, no deformation 

Hot-rolled lamination: High bonding strength 

2. Coating process 

Magnetron sputtering: The best performance, but high cost 

Anodizing: Good weather resistance, medium efficiency 

Electroplating treatment: Gradually phased out 

3. Quality inspection 

Helium mass spectrometry leak detection: Ensure welding sealing 

Thermal performance test: Measured efficiency curve 

Durability tests: damp heat and salt spray tests 

Vi. Application Scenarios and Selection Guide

1. Household hot water system 

Recommendation: Copper tube - aluminum plate structure 

Area: 2-4 square meters 

Applicable to families of 3 to 5 people 

2. Engineering hot water system 

Recommendation: Copper tube - copper plate structure 

Area: 20-200 square meters 

Applicable: Hotels, schools, factories 

3. Heating system 

Recommendation: High-efficiency copper tube - copper plate structure 

Requirement: High efficiency in low-temperature working conditions 

4. Industrial heat utilization 

Recommendation: Special stainless steel structure 

Requirements: High-temperature resistant and corrosion-resistant

Vii. Maintenance and Life Cycle

1. Normal maintenance requirements 

Check the pH value of the system every year 

Check the antifreeze concentration every 2 to 3 years 

Conduct system pressure testing every five years 

2. Life expectancy 

High-quality copper tube - copper plate structure: over 20 years 

Copper tube - aluminum plate structure: 15-20 years 

All-aluminum structure: 10-15 years

Viii. Technological Development Trends

1. Material innovation 

Nano-coating materials: Enhance selective absorption ratio 

Composite substrate material: Enhance heat conduction and reduce weight 

2. Structural optimization 

Microchannel design: Enhance heat transfer efficiency 

3D channel design: Optimizing flow distribution 

3. Intelligent manufacturing 

Automated welding production line 

Machine vision quality inspection 

Conclusion

As the core component of flat-plate solar collectors, the technical level and manufacturing quality of the absorption plate core directly determine the performance of the entire system. With the advancement of materials science and manufacturing technology, modern absorption board cores are evolving towards higher efficiency, longer lifespan and lower cost. 

When choosing a flat-plate collector, a thorough understanding of the technical details and process level of its "heart" - the absorption plate core - is the key to ensuring the long-term efficient operation of the system. Investing in high-quality and efficient absorption board cores not only means higher heat gain and faster return on investment, but also guarantees reliable service for decades. 

With the advancement of the carbon neutrality goal and the acceleration of energy transition, efficient and reliable absorption board core technology will continue to play a crucial role in the field of solar thermal utilization, providing core technical support for building energy conservation and industrial thermal substitution.