Effect of substrate on graphite and other solar selective surfaces

Area of Science:

• Materials Science
• Solar Energy Engineering
• Surface Physics

Background:

• Solar selective surfaces are crucial for efficient solar thermal energy conversion.
• Optimizing substrate and coating materials is key to enhancing collector performance and durability.

Purpose of the Study:

• To compare the performance of different metal substrates (copper, silver, nickel) for solar selective surfaces.
• To evaluate the absorptance and emittance properties of graphite films on various substrates.
• To investigate the aging effects on these films at elevated temperatures.

Main Methods:

• Comparative analysis of solar selective surfaces based on maximum available power criterion.
• Characterization of absorptance and emittance of graphite films on copper, silver, nickel, and titanium.
• Investigation of film aging through thermal exposure up to 400°C and diffusion analysis.

Main Results:

• Copper and silver substrates slightly outperform nickel at 200°C.
• All three metals (copper, silver, nickel) perform comparably as substrates at 100°C and below.
• Graphite films on copper and silver demonstrate suitability for high-temperature evacuated collectors after aging.

Conclusions:

• Copper and silver are preferred substrates for high-temperature solar selective surfaces.
• Graphite films exhibit good thermal stability and optical properties, making them suitable for advanced solar collectors.
• Understanding diffusion mechanisms is vital for predicting the long-term performance of solar selective surfaces.