Recent advances in solar thermal selective coatings (review)

Source: Applied Sciences (MDPI), 2024 review. Credibility: High (peer-reviewed review). Confidence: high.

Key points

• Spectrally-selective coatings: α ≥ 0.95, ε ≈ 0.05-0.10 — high absorptance with low re-radiation loss, simultaneously.
• Flat black paint: α 0.82-0.95 but ε ≈ 0.85-0.9 (non-selective, high IR loss).
• Sub-µm textured surfaces can achieve selectivity geometrically (absorb solar, mirror-like in IR) but have corrosion/durability problems limiting commercialization.
• A macroscopic V-groove raises absorptance AND emittance together (not selective) — so it underperforms a selective coating on net retained heat.

Relevance

The dominant alternative to geometric blackness for geometric-blackness-solar-adsorption-bed-face: a selective coating beats a macro V-groove on the optical lever (higher α, far lower ε) without soiling/self-shading penalties. The 1991 patent (CN2091433U) already paired the groove WITH a selective coating, not relied on geometry alone.