{
    "title": "RadiCold -- Metamaterial Thermosiphon Cooling System",
    "inventor_name": "Ronggui Yang",
    "publication_year": 2017,
    "device_name": "RadiCold",
    "goal": "Provide passive, zero-energy cooling for structures and thermoelectric power-plant condensers.",
    "problem_addressed": "High water and electricity consumption of conventional wet-cooling systems for buildings and power plants.",
    "concept_summary": "A 50-um-thick glass-polymer hybrid metamaterial film coated with a thin silver layer reflects most solar radiation while emitting strong infrared radiation through the atmospheric window, enabling daytime radiative cooling without electricity or water.",
    "detailed_description": "The metamaterial consists of visibly-scattering glass microspheres embedded in a polymer matrix; a silver backing enhances solar reflectivity. The roll-to-roll manufactured film can be applied to roofs, solar panels, or as the top layer of a thermosiphon cold-storage module. Under direct sunlight it achieves a radiative cooling power of about 93 W/m^2 (and >100 W/m^2 in the Radicold system) and can reduce building temperatures and improve solar-panel efficiency by 1-2 %. A 200-m^2 prototype is planned for 2017.",
    "category": "Thermal Systems",
    "principles": [
        "Passive radiative cooling",
        "Solar reflectivity",
        "Infrared emissivity"
    ],
    "scientific_domains": [
        "Materials Science",
        "Thermodynamics",
        "Optics"
    ],
    "mechanisms_of_action": [
        "Reflect incoming solar radiation",
        "Emit infrared radiation through atmospheric window",
        "Create temperature gradient that drives thermosiphon water flow"
    ],
    "materials": [
        "Glass microspheres",
        "Polymer matrix",
        "Silver coating"
    ],
    "energy_sources": [],
    "inputs": [
        "Solar radiation",
        "Ambient heat"
    ],
    "outputs": [
        "Infrared thermal radiation to space",
        "Cool water in thermosiphon"
    ],
    "claimed_performance": "Noon-time radiative cooling power of 93 W/m^2 under direct sunshine; heat flux >100 W/m^2 day-and-night; 10-20 m^2 can cool a single-family house; 1-2 % solar-panel efficiency recovery.",
    "experimental_evidence": "Demonstrated 93 W/m^2 cooling power in laboratory tests; roll-to-roll manufacturing demonstrated; prototype of 200 m^2 planned.",
    "replication_status": "Patented; prototype planned; no independent third-party replication reported.",
    "keywords": [
        "radiative cooling",
        "metamaterial",
        "glass-polymer hybrid",
        "passive cooling",
        "thermal management",
        "thermosiphon"
    ],
    "related_technologies": [
        "Radiative cooling paints",
        "Thermoelectric cooling",
        "Passive roof cooling systems"
    ],
    "controversy_level": "low",
    "confidence_score": 0.9,
    "practicability_score": 0.8,
    "fringe_score": 0.1,
    "evidence_strength": 0.6,
    "risk_score": 0.1,
    "trl_estimate": 6,
    "source_urls": [
        "http://www.colorado.edu/today/2017/02/09/newly-engineered-material-can-cool-roofs-structures-zero-energy-consumption",
        "http://science.sciencemag.org/content/early/2017/02/08/science.aai7899",
        "http://www.colorado.edu/today/2015/08/25/cu-boulder-awarded-3-million-transformational-power-plant-cooling-technology",
        "https://arpa-e.energy.gov/?q=slick-sheet-project/radiative-cooling-and-cold-storage"
    ],
    "organizations": [
        "University of Colorado Boulder",
        "ARPA-E (U.S. Department of Energy)",
        "CU Boulder Technology Transfer Office"
    ],
    "applications": [
        "Building roof and ceiling cooling",
        "Thermoelectric power-plant condenser cooling",
        "Solar panel temperature management"
    ],
    "limitations": [
        "Performance depends on clear sky and atmospheric transparency",
        "Scaling roll-to-roll production to large commercial volumes",
        "Cooling power limited to ~100 W/m^2, may be insufficient for high-load applications"
    ],
    "open_questions": [
        "Long-term durability of the glass-polymer-silver stack under UV exposure",
        "Cost competitiveness versus conventional HVAC and dry-cooling systems",
        "Effectiveness in humid or cloudy climates"
    ],
    "red_flags": [],
    "evidence_quotes": [
        "The metamaterial film cools the object underneath by efficiently reflecting incoming solar energy back into space while simultaneously allowing the surface to shed its own heat in the form of infrared thermal radiation.",
        "When backed with silver coating, the metamaterial shows a noon-time radiative cooling power of 93 W/m^2 under direct sunshine.",
        "Just 10 to 20 square meters of this material on the rooftop could nicely cool down a single-family house in summer.",
        "We can cool the panel and recover an additional one to two percent of solar efficiency.",
        "Roll-to-roll manufacturing technology will enable effective radiative cooling at a low cost."
    ]
}