Radiative imbalance with the sky → Chemical fuel

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.29 · Radiative imbalance with the sky × Thermochemicalfamily: Thermochemical

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

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→ Thermochemical redox cycleestablishedclaim record

   thermal → chemical · loss to thermal

   • a redox-active metal oxide (ceria, ferrites) reduced at 1400–1800 K, typically in a solar receiver, and re-oxidised by H₂O or CO₂ at 800–1200 K

   above ~700 K

   refs [5] [6]
4. 04
   Thermochemical redox cycle —produces→ Chemical fuel (H₂, CO, syngas)establishedclaim record

   chemical → chemical

   refs [6]
5. 05
   Chemical fuel (H₂, CO, syngas) —converts into→ Chemical fuelestablishedclaim record

   chemical → chemical

   refs [5]

Evidence for the complete composition · 0

No source on record for this exact composition. The sources below support the individual steps, not the route as a whole.

Evidence for the constituent relations · 6

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]
   A. Steinfeld. Solar thermochemical production of hydrogen––a review (2005)

   Solar Energy 78, 603-615 · doi:10.1016/j.solener.2003.12.012 · crossref ✓ 2026-09-20 · record
6. [6]
   S. Abanades. Redox Cycles, Active Materials, and Reactors Applied to Water and Carbon Dioxide Splitting for Solar Thermochemical Fuel Production: A Review (2022)

   Energies 15, 7061 · doi:10.3390/en15197061 · crossref ✓ 2026-09-20 · record