raw · papers · ingested 2026-06-19
CoolSkin: A Novel Façade Design for Sustainable Solar Cooling by Adsorption
Source: https://doi.org/10.47982/jfde.2022.powerskin.3
Read from local Zotero full-text PDF (group 5183627 / Joule Heist).
Key findings
- Concept: a decentralized, façade-integrated closed-adsorption cooling façade (ACF) developed in CRC/SFB 1244 (Univ. Stuttgart). Three components — adsorber + condenser in the façade, evaporator below the storey ceiling — coupled by water vapor. Two daily phases: solar-driven regeneration (desorption) by day, then cooling (adsorption/evaporation) which lowers evaporator pressure and chills the building.
- Working pair: zeolite + water in a vacuum adsorber chamber (Fig. 6 labels “vacuum chamber with zeolite”); water is the refrigerant.
- Cooling performance: reference-case simulation yields ~54 W per m² of adsorber façade, sustainable for 12 hours; a parameter-optimized best-case configuration reaches up to 150 W/m² (Böckmann et al. 2022). Adsorber temperature reaches ~100 °C at the end of the regeneration phase. Continuous all-day cooling needs adsorbers on opposite façades.
- Reference adsorber design: based on a flat-plate collector but needs high regeneration-vs-cooling temperature swing, so uses double insulating glazing (U=0.3 W/m²K shown, ~1.1 W/m²K equivalent) + highly selective PVD/CVD coated aluminium absorber sheet (~90.2-96% solar absorption). A 10 mm ventilated air gap with top/bottom flaps enables switchable heat release (vertical convection) for fast cool-down; vertical fins boost heat dissipation.
- Folded absorber sheet (Layer 1): origami folding gives ~50% more surface area than a flat sheet, shifts solar gain into morning hours, and saves material — but solar-gain improvement is small (SSE: 4214 Wh/m² flat-RD vs 4146 Wh/m² optimized-fold; east orientation +10% over non-optimized). Folding slightly raises solar gain yet reduces cooling rate due to less fin-driven heat release.
- ETFE glazing substitution (Layer 2): replacing glass with ETFE cushion (U≈3 W/m²K) or a novel 2-layer ETFE vacuum panel (EVP) cuts weight and adds design freedom (transmittance ~91%, ETFE melts ~280 °C). But EVP solar gain drops to 2880-3091 Wh/m² (vs 4214 for RD-T83%), lowering adsorber temperature and cooling power.
- Conclusion / trade-off: every geometric/material surface modification reduces total cooling power; the plain reference design (with fins) gives the highest cooling rate (~100 W/m² peak in Fig. 20). Rough target cooling demand is ~60 W/m² residential, ~100 W/m² commercial — ETFE variants only meet 60 W/m² briefly. Folded sheet is the most balanced aesthetic+functional option; ETFE vacuum panel offers most visual flexibility but poor function.