Passive Daytime Radiative Cooling
Also known as: PDRC
PDRC surfaces reflect almost all incoming sunlight and simultaneously emit thermal infrared radiation through the atmosphere and into the cold of deep space. The result is a surface that can be several degrees cooler than the surrounding air — during the day, in full sun, using no electricity.
Scientific detail
PDRC materials combine near-unity solar reflectance (≈0.95–0.98 across 0.3–2.5 μm) with high thermal emittance in the 8–13 μm atmospheric window. Because the sky at those wavelengths acts as an effective radiative sink at roughly 3 K, a surface with these optical properties experiences a net radiative heat loss even at solar noon, producing sub-ambient equilibrium temperatures under clear-sky conditions.
Related terms
Radiative Cooling
Heat loss from any object by emitting thermal infrared radiation.
Atmospheric Window
A range of infrared wavelengths (roughly 8–13 μm) where the atmosphere absorbs relatively little of Earth's outgoing thermal radiation.
Solar Reflectance
The fraction of incoming solar energy a surface reflects across the sun's spectrum.
Thermal Emittance
How efficiently a surface releases heat as infrared radiation.
Albedo
The fraction of sunlight a surface reflects — 0 is black, 1 is a perfect mirror.
Reflective Cooling
Cooling by bouncing sunlight away from a surface before it can be absorbed as heat.
Where this concept shows up on MEER
Related projects
- Freetown, Sierra Leone
Reflective rooftops across informal settlements.
- California, USA
Rooftop mirror arrays measuring cooling potential.
- Pune, India
Rooftop reflective installations in dense urban housing.
Related publications
Related MEERTalks
- MEERTalks
Recorded conversations with scientists and partners.
Explore in topic hubs
Curated collections of MEER research, projects, publications and stories that feature this term.
Passive Cooling
Everything MEER publishes on passive cooling — reflective roofs, PDRC materials, canopies, reservoir systems, projects, publications and stories, gathered in one place.
Radiative Cooling & PDRC
PDRC materials, the atmospheric window, thermal emittance and the practical engineering of surfaces that radiate heat directly to deep space.