Solar Adsorption Cooling
Solar Adsorption Cooling
The most on-brand application of Adsorption Cooling: use sunlight as the desorption heat, so peak supply (midday sun) roughly coincides with peak cooling demand. This article maps the design space — from intermittent single-bed solar ice makers (the collector is the adsorber) to two-bed continuous silica-gel/water chillers with thermal storage — and the measured/simulated performance across climates. The recurring lessons: cyclic COP ~0.35–0.5, solar COP ~0.17–0.3, and collector area + cost dominate the economics. See Solar Thermal for the collectors themselves.
The two architectures
Intermittent (single-bed) solar ice makers. The simplest form: a flat-plate collector whose absorber plate is the adsorbent bed. By day the sun desorbs the refrigerant (condensed and stored); by night the bed cools and re-adsorbs, producing the cooling effect — one cycle per day. Working pairs are usually activated carbon/methanol or activated carbon/ammonia. Examples: a coconut-shell activated-carbon/methanol valveless ice maker with a 1 m² stainless bed holding ~19 kg carbon regenerated at 90–100 °C (Dhokane); BSc-scale AC/methanol solar ice makers (Hlail); and hybrid charcoal/methanol + charcoal/R-11 prototypes reaching minimum evaporator temperatures of 16–17 °C (Rahman). Cheap and unpowered, but low COP and once-daily.
Continuous two-bed chillers. Two sorbent beds alternate adsorption/desorption so cooling is continuous, driven by hot water from collectors (often silica-gel/water). These are the building-scale machines — and the same hardware sold commercially (see Commercial Adsorption Chillers), just solar-fed.
Measured & simulated performance
| Study | System | Climate | Key numbers |
|---|---|---|---|
| Alahmer (Perth) | Two-bed silica-gel/water + CPC collectors | Temperate, high-DNI | ~11 kW peak; cyclic COP ~0.5, solar COP ~0.3; ~38 m², ~11 yr payback |
| Bawazir (Riyadh) | TRNSYS, 80-villa silica-gel/water | Hot desert | 96 % solar fraction at 5500 m² ETC + 350–400 m³ storage; 74 % energy-cost cut, ~75 % CO₂ cut vs vapor compression |
| Najeh (Nancy) | Two-bed silica-gel/water (ENERBAT) | Continental | daily COP 0.35–0.37; a geothermal-cooled adsorber roughly halves cycle time vs ambient-air cooling |
| Yuan | SAPO-34 vs ZSM-5, parabolic-trough tubular bed | — | max COP 0.169, SCP up to 169.7 W·kg⁻¹ |
| Dias | Silica-gel RD2060/water, 50-tube cylindrical bed (model) | — | COP 0.5, SCP 44 W·kg⁻¹ |
The pattern: two-bed silica-gel/water lands around cyclic COP 0.35–0.5; solar COP (which folds in collector efficiency) is lower, ~0.17–0.3; and concentrating/intermittent variants trade COP for simplicity or higher drive temperature. The hot-day condenser derating from Limitations & Mitigations applies directly — Najeh’s geothermal-cooled adsorber is one mitigation, halving cycle time.
Economics: collector area is the lever
Across the reviews and techno-economic studies the same conclusion recurs: the solar collector field dominates both cost and footprint. A particle-swarm-optimized design found the optimum ~13 % cheaper than a baseline, best at 5–10 kW, with collector cost the bottleneck and ~50 m²/10 kW avoiding ~15.7 t CO₂ (Motamedi). Jordan and large-scale energetic/economic/environmental assessments (Saidi; Bawazir) show favorable cases concentrate in high-DNI, high-cooling-load climates — the San Antonio / Gulf profile. Reviews (Bhargav; Al-Yasiri) frame solar adsorption (SADS) against solar absorption (SABS) and solid-desiccant (SDS) cooling: adsorption wins on lower regeneration temperature and no moving/corrosive parts, at the cost of lower COP and larger footprint.
See Also
- Adsorption Cooling — the underlying cycle and working pairs
- Solar Thermal — the collectors that supply the desorption heat
- Performance & Numbers — the COP/SCP envelope these systems operate in
- Commercial Adsorption Chillers — the two-bed hardware, solar-fed
- Geothermal — ground-cooled adsorbers/condensers that fight hot-day derating
- Absorption Cooling — the solar ammonia absorption parallel (liquid sorbent)
Sources
- Bhargav — solar silica-gel/water adsorption chiller review
- Al-Yasiri — solar-powered cooling for buildings (SABS/SADS/SDS)
- Alahmer — two-bed silica-gel/water chiller, Perth
- Bawazir — large-scale solar adsorption, Riyadh (TRNSYS)
- Najeh — two-bed silica-gel/water, Nancy
- Yuan — SAPO-34/ZSM-5 concentrated-collector system
- Rahman — solar hybrid charcoal/methanol + R-11
- Motamedi — techno-economic optimization
- Dias — silica-gel/water cooler design & modeling
- Dhokane — intermittent AC/methanol solar ice maker
- Hlail — solar adsorption refrigeration cycle (design)
- Saidi — economic study, Jordan