Preparation and Characterization of a Selective Polymer-Based Solar Absorber for Building Integration

Source

Cekon, M.; Struhala, K.; Kopkane, D. “Preparation and Characterization of a Selective Polymer-Based Solar Absorber for Building Integration.” Applied Sciences 10, no. 21 (2020): 7861. Published 6 November 2020 by MDPI. Open access (CC BY 4.0).

Institutional affiliation: Brno University of Technology (VUT), Czech Republic.

Key Findings

Performance Measurements

• Solar absorptance: 0.95
• Thermal emittance: approximately 0.3
• Selectivity ratio (alpha/epsilon): 3.2
• Temperature limit: designed for applications not exceeding 100 C

Manufacturing

• Produced on a mass-production roll-to-roll line
• Polymer-based foil construction (the absorber itself is polymeric, not just a polymer substrate with a metal coating)
• The polyethylene layer is identified as the source of higher emittance compared to metal-based references

Comparison with Commercial Metal Absorbers

• The prototype’s emittance (~0.3) is approximately 25% worse than three commercial metal-based reference absorbers
• Metal-based selective surfaces typically achieve emittance of 0.05-0.10
• The polymer foil trades some thermal performance for dramatically lower environmental impact and manufacturing cost

Life-Cycle Assessment

• Environmental impacts up to 98% lower than commercial metal-based selective absorbers
• Significant reduction in embodied energy and material toxicity

Durability Concerns

• Authors note polymer foil expected to be less durable than metal-based products
• Needs protection from dust, mechanical damage, and UV radiation
• Future durability testing called for
• Intended for building-integrated use at moderate temperatures (sub-100 C)

Relevance to Tank Application

The study demonstrates that polymer-based selective absorbers are feasible at low temperatures (sub-100 C), which aligns with the operating range of water storage tanks. Key considerations:

1. The polyethylene layer contributes to elevated emittance — this is the same material family as HDPE tanks
2. A selectivity ratio of 3.2 is modest but meaningful compared to flat black paint (selectivity ~1.0)
3. Roll-to-roll manufacturing suggests potential for wrapping or laminating onto tank surfaces
4. The sub-100 C temperature limit is not a constraint for water heating applications
5. UV and mechanical protection would be needed for outdoor tank installations