DRY CLOUD (Adiabatic Evaporative Air Cooling)

Overview

DRY CLOUD lowers air temperature by atomizing water into an ultra-fine aerosol (~5 µm) under ~6 bar of compressed air. The droplets evaporate completely within fractions of a second, absorbing heat from the air (latent heat ~2.4 MJ per liter) without leaving visible droplets, wet surfaces, or puddles — hence the name "dry cloud." Unlike a conventional air conditioner, there is no compressor refrigeration cycle and no freon: cooling comes directly from the water phase change, so energy use is a small fraction of a comparable AC. The technology is most effective in dry, hot climates and in enclosed or semi-enclosed sunlit spaces, where it delivers real comfort cooling at very low operating cost.

Applications

Primary use cases:

• Enclosed spaces — cafés, tents, kiosks, cabins, small rooms (up to ~150 m³)

• Transport — aircraft cabins on the ground, train and bus interiors, reefer/cargo holds

• Semi-enclosed sunlit venues — stadium lower bowl, covered stands, atriums, terraces, covered markets, fan zones

Typical scenarios:

• Rapid spot cooling where conventional AC is impossible or uneconomic

• Comfort zones under direct sun

• Venues without fixed cooling infrastructure

Scale:

• Portable single module (<10 kg) for enclosed volumes

• Stationary multi-module systems with mains water for venue-scale zones

Operating Principle

Water is pressurized (~6 bar) and dispersed through fine nozzles into a ~5 µm aerosol. At this size each droplet fully evaporates in 0.025–0.25 s (d²-law) and settles less than 0.2 mm before vanishing (Stokes' law), so no wetting occurs. Evaporation removes sensible heat from the surrounding air, dropping its temperature along a constant-enthalpy (adiabatic saturation) path. Cooling stops at the wet-bulb temperature, so performance is governed by ambient humidity. Compressed air serves as the atomization and mixing medium; about 99% of the cooling comes from water evaporation, not from air expansion.

Key steps:

1. Water + compressed air feed
2. Atomization to ~5 µm aerosol
3. Near-instant evaporation, latent heat absorption
4. Air temperature drop toward wet-bulb limit
5. Brief venting to manage indoor humidity

Limitations:

• Effective only down to the wet-bulb limit

• Works in dry air (RH < ~20–25%)

• Indoor humidity must be vented periodically

Key Parameters

|Parameter|Conventional AC|DRY CLOUD|

|---|---|---|

|Cooling mechanism|Freon compression cycle|Water evaporation (latent 2.4 MJ/L)|

|Power (comparable effect)|1–1.2 kW|~0.1–0.2 kW (portable module)|

|Refrigerant / consumables|Freon, filters|Water only|

|ΔT achievable (dry climate, +45 °C)|to set point|15–24 °C (to +24…+28 °C)|

|ΔT in humid climate (RH 40–60%)|unaffected|only 7–12 °C, reduced comfort|

|Water use|none|~2–3 L per ~150 m³ (one-shot); 4–10 L/h to hold a café|

|Emissions / noise|medium|near-zero|

Physics note: the marketed "+45 → +12…+15 °C" lies below the wet-bulb floor; the honest, defensible figure is a 15–24 °C drop in dry climates.

Architecture and Components

Core components:

• Water reservoir

• Compressed-air source (~6 bar)

• Micro-nozzle dispenser / atomizer

• Control unit (cycle and temperature)

Portable version: <10 kg, battery-powered (~100–200 W), 1–3 h autonomy.

Stationary version: nozzle array along the upper edge of the target zone, mains/tank water supply, optional dew-prevention control.

The system is modular — venue zones scale by adding emitters and modules.

Advantages

Technical:

• Full evaporation, no wetting or puddles

• Instant effect (1–5 min)

• No moving refrigeration parts

Economic:

• Cooling energy comes "free" from the phase change — power a fraction of AC

• Water is the only consumable

• Minimal CAPEX vs trying to air-condition open venues

Environmental / regulatory:

• No freon (banned/quota-limited in the EU)

• No consumables, water only

• ESG-friendly

Strategic:

• Cools spaces where AC is impossible (open/semi-open under sun)

• Portable and infrastructure-free

• Strong fit for hot dry-climate markets (Gulf dry season, MENA, southern Europe, Central Asia, Australia)

Integrations

Compatible with venue water supply (mains, technical water, stormwater/drainage reuse), standard electrical supply or batteries/solar, and venue climate control with simple sensor/automation (temperature, humidity, timed cycles).

Deployment & Operation

Portable: fill water, switch on, effect in 1–5 min; vent briefly to manage humidity.

Stationary venue zone: site assessment (geometry, wind rose), emitter placement on the windward/upper edge so cool air flows onto people, water-supply connection.

Operating conditions:

• Best in still air (< 1–2 m/s)

• Dry climate (RH < ~20–25%)

Operation is simple, low-skill, and low-maintenance.

TRL

TRL 4 (confirmed by Michael). Validated in lab: adiabatic evaporation principle confirmed, ~5 µm aerosol dispersion validated, latent-heat calculations verified (2.4 MJ/L), prototype modules tested for enclosed/cabin applications. (Legacy document claimed TRL 4–6; adjusted to TRL 4 per Michael — field validation and certification pending.)

TRL scale:

• TRL 1 — basic principles observed
• TRL 2 — technology concept formulated
• TRL 3 — experimental proof-of-concept
• TRL 4 — validated in lab ← DRY CLOUD
• TRL 5 — validated in relevant environment
• TRL 6 — demonstrated in relevant environment
• TRL 7 — prototype in operational environment
• TRL 8 — system complete and qualified
• TRL 9 — proven in operational environment

Market Potential

Target segments: HoReCa terraces, sports and event venues, transport interiors, outdoor public spaces in hot dry regions.

The global evaporative / spot-cooling and outdoor-comfort market is large and growing with rising heat extremes and the freon phase-out. DRY CLOUD's realistic niche is dry-climate enclosed and semi-enclosed sunlit spaces.

Typical Project Economics

Portable module: low CAPEX, water only, ~0.1–0.2 kWh/h.

Café (150–300 m³): one-shot 0.7–2.2 L; continuous hold 4–10 L/h — a small tank.

Venue sector (~8 000 m³): 30–50 modules, 2–5 m³ water/h — far below the cost of air-conditioning an open bowl.

Payback driven by avoided AC energy and equipment.

Risk Factors

• Climate dependence — effective only in dry air; humid climates underperform

• Marketing-vs-physics gap — "+45 → +15 anywhere" and "2–3 L for a stadium" are not defensible and invite expert pushback

• Open-space deployment needs continuous water (m³/h) and many modules — not a single portable unit

• Indoor humidity management; outdoor wind drift

• Conservative adoption and certification timelines

Related Technologies

ARBOK-CoolTower — closed-loop industrial cooling

ARBOK MedZWD — vacuum phase separation

SNOWQUEEN — climate / precipitation engineering