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In-Progress Project WorkspaceExperimental work beginning (Unpublished workspace)

YSRN Research Output · Open Protocol

Radiative Cooling Surface Coating: Experimental Protocol & Thermal Characterisation

An independent experimental inquiry into high solar reflectance and mid-infrared atmospheric window thermal emittance using polymer-particle composite coatings.

Lead: Erencan Yılmaz August 2026 Planned protocol · not yet validated

1. Abstract & Scope

Passive daytime radiative cooling (PDRC) aims to reflect incident solar irradiance while emitting thermal radiation through the atmospheric window. This unpublished workspace documents a planned, reproducible comparison protocol; it does not yet report a validated cooling result.

2. Bounded Research Question & Hypotheses

Primary Protocol Question:

How does the volume loading fraction of inorganic micro-particles (e.g. BaSO4 / CaCO3) in an acrylic matrix affect surface temperature depression relative to ambient air under direct midday sunlight (>800 W/m²)?

  • Independent Variable: Particle-to-binder mass ratio (0%, 20%, 40%, 60% w/w) and coating thickness (100–300 μm).
  • Dependent Variable: Continuous substrate temperature (°C) measured via calibrated K-type thermocouples in an insulated chamber.
  • Controlled Variables: Wind convection shield (PE film), chamber insulation thickness (aerogel/expanded polystyrene), ambient solar irradiance (pyranometer / lux meter calibration).

3. Materials, 5 µm BaSO₄ Metal Coupons & Measurement Setup

The research protocol investigates accessible, sub-ambient passive radiative cooling using 5 µm particle-size Barium Sulphate (BaSO₄) as the primary optical scattering and infrared-emitting pigment, synthesized in an acrylic/silicone matrix and coated directly onto standardized metallic coupon substrates:

Metal Coupon Substrates

Standardized 50 mm × 50 mm × 1.5 mm aluminium and galvanized steel test coupons coated with 150–250 µm controlled film applicator passes to evaluate substrate adhesion and thermal conduction.

Optical & Thermal Properties

Targeting >95% solar reflectance (0.3–2.5 µm) and >0.93 selective thermal emittance across the atmospheric transparency window (8–13 µm) benchmarked against Purdue University (Xiulin Ruan, 2021) optical baselines.

Calibrated Thermocouple Logging

Paired Type-K thermocouples affixed to coupon undersides with thermally conductive paste, logging differential temperatures (T_coupon - T_ambient) under real-world midday solar conditions (>800 W/m²).

Wind & Parasitic Heat Shield

Low-density polyethylene (LDPE) windshield (>85% mid-IR transmissive) mounted over an aerogel/polystyrene insulated chamber to isolate radiative cooling from ambient convective heating.

4. Stated Limitations & Reproducibility Boundaries

  • Humidity Sensitivity: Atmospheric water vapour absorption heavily attenuates the 8–13 μm window. Results in high relative humidity (>70%) will show diminished cooling power.
  • No Commercial or Production Claim: This is an educational and student research protocol. No claim of commercial cooling efficiency or patent validity is asserted.
  • Thermal Boundary Uncertainty: Parasitic heat gain through chamber walls introduces a ±0.8°C systematic uncertainty unless differential calibration against a silver-coated mirror reference is conducted.

5. Authorship, Review & Ethics

Conducted under the YSRN Research Standards and Contribution Policy. Contributions are attributed based on experimental execution, data curation, and protocol derivation.