Night-time radiative-cooling thermoelectric generator

Matrix context

D = disequilibrium row · C = coupling family column. A cell reads the state of the atlas for that pair.

D.12 × C.20 · Radiative imbalance with the sky × Photothermalfamily: PhotothermalD.12 × C.01 · Radiative imbalance with the sky × Thermoelectricfamily: Thermoelectric

Measured or reported performance

1. electrical power density25 mW/m²device2019
   clear-night rooftop experiment at Stanford, CA, late December 2017, dew point −1 to −3 °C, device 1 m above roof level; a 200 mm aluminium disk painted black (ε ≈ 0.95) as the sky-facing emitter on the cold side of a Marlow TG12-4 module (ZT = 0.71) inside a polystyrene enclosure with a 12.5 µm polyethylene wind cover; the hot side coupled to a finned 200 mm aluminium disk in ambient air — read on the Cell Press page in the owner's Chrome (the article carries the PII S2542-4351(19)30412-X); the paper's 'pathways to improving performance … to 0.5 W/m²' is a projection with stated component improvements and is not recorded as a physical datum
   refs [4]

best recorded power density (derived)

25 mW/m² per radiative cooler area — electrical power density, device, 2019; maximum-power-point thermoelectric electrical output (nearly 0.8 mW; J_sc 44 mA, V_oc 79 mV) normalised to the area of the 200 mm radiative-cooler disk

Typed bounds on this route

Every limit the atlas holds for this route, as constraint records: reached through bounded_by claims on the route's own entities. Hard bounds (an upper bound or a formula) decide the thermodynamic-bound check above; benchmarks, constitutive relations and resource limits are listed and never decisive. No prose limit exists anywhere (pass 42).

• Radiative cooling power bound · resource-bound · listed, never decisive
  net cooling power ≲ 100–150 W/m² under a clear sky
• Carnot limit · formula-bound · hard, applies to this route
  η ≤ 1 − T_c/T_h for any heat engine between reservoirs at T_h and T_c
• Thermoelectric figure-of-merit bound · formula-bound · hard, applies to this route
  η = η_Carnot · (√(1+ZT) − 1)/(√(1+ZT) + T_c/T_h)
• Onsager–Casimir reciprocity · constitutive-relation · listed, never decisive
  L_ij(B) = ε_i ε_j L_ji(−B): the cross-coefficients of coupled linear transport are equal up to the time-reversal parities ε of the variables and reversal of the magnetic field; L_ij = L_ji is the zero-field, even-parity case

Steps

1. 01
   Radiative imbalance with the sky —drives→ Radiative sky coolingreplicatedclaim record

   radiative → thermal

   • an emitter with high emissivity in the 8–13 µm window and high solar reflectance
   • a clear sky; humidity and cloud close the window

   refs [1] [2] [3]
2. 02
   Radiative sky cooling —produces→ Temperature gradientreplicatedclaim record

   thermal → thermal

   • the cooled surface sits a few kelvin below ambient air

   refs [1] [4] [3]
3. 03
   Temperature gradient —drives→ Seebeck effectestablishedclaim record

   thermal → electrical · loss to thermal

   ΔV = S · ΔT · Seebeck coefficient S [V/K]

   Open-circuit voltage between the ends of one conductor (absolute S) or across a couple of two conductors (S_A − S_B); ΔV and ΔT measured from the same reference end; S < 0 for electron-dominated transport, S > 0 for hole-dominated, so the polarity is material- and convention-dependent.

   • a spatial temperature difference across a conductor or semiconductor
   • a closed circuit of dissimilar materials, or a single material with ends at different temperatures

   solid · conductor required · temperature gradient required

   refs [5] [6] [7]
4. 04
   Seebeck effect —produces→ Charge carriersestablishedclaim record

   electrical → electrical · loss to thermal

   • carriers diffuse from the hot end and accumulate at the cold end

   refs [6] [8]
5. 05
   Charge carriers —converts into→ Electrical workestablishedclaim record

   electrical → electrical · loss to thermal

   • carriers driven through an external load at the potential difference the source maintains

   refs [9]

Evidence for the complete composition · 1

1. [4]
   A. P. Raman, W. Li, S. Fan. Generating light from darkness (2019)

   Joule 3, 2679–2686 · doi:10.1016/j.joule.2019.08.009 · crossref ✓ 2026-09-19 · record

Evidence for the constituent relations · 9

1. [1]
   A. P. Raman et al.. Passive radiative cooling below ambient air temperature under direct sunlight (2014)

   Nature 515, 540–544 · doi:10.1038/nature13883 · crossref ✓ 2026-09-19 · record
2. [2]
   Y. Zhai et al.. Scalable-manufactured randomized glass-polymer hybrid metamaterial for daytime radiative cooling (2017)

   Science 355, 1062–1066 · doi:10.1126/science.aai7899 · crossref ✓ 2026-09-19 · record
3. [3]
   J.-l. Kou et al.. Daytime radiative cooling using near-black infrared emitters (2017)

   ACS Photonics 4, 626–630 · doi:10.1021/acsphotonics.6b00991 · crossref ✓ 2026-09-19 · record
4. [4]
   A. P. Raman, W. Li, S. Fan. Generating light from darkness (2019)

   Joule 3, 2679–2686 · doi:10.1016/j.joule.2019.08.009 · crossref ✓ 2026-09-19 · record
5. [5]
   T. J. Seebeck. Ueber die magnetische Polarisation der Metalle und Erze durch Temperatur-Differenz (1826)

   Annalen der Physik 82(2), 133–160 · doi:10.1002/andp.18260820202 · crossref ✓ 2026-09-19 · record
6. [6]
   H. J. Goldsmid. Introduction to Thermoelectricity (2nd ed.) (2016)

   Springer Series in Materials Science 121 · doi:10.1007/978-3-662-49256-7 · crossref ✓ 2026-09-19 · record
7. [7]
   H. B. Callen. The application of Onsager's reciprocal relations to thermoelectric, thermomagnetic, and galvanomagnetic effects (1948)

   Physical Review 73, 1349 · doi:10.1103/PhysRev.73.1349 · crossref ✓ 2026-09-19 · record
8. [8]
   C. Herring. Theory of the thermoelectric power of semiconductors (1954)

   Physical Review 96, 1163 · doi:10.1103/PhysRev.96.1163 · crossref ✓ 2026-09-19 · record
9. [9]
   N. W. Ashcroft, N. D. Mermin. Solid State Physics (1976)

   Holt, Rinehart and Winston · book, no DOI · record