{
    "title": "Solar Vapor Generator",
    "inventor_name": "George Ni",
    "publication_year": 2016,
    "device_name": "Solar vapor generator (floating solar receiver)",
    "goal": "Generate steam from water using ambient sunlight without optical concentration for applications such as desalination, water heating, wastewater treatment, and sterilization.",
    "problem_addressed": "High cost and complexity of conventional solar steam systems that rely on mirrors or lenses for optical concentration.",
    "concept_summary": "A low-tech floating structure consisting of a sponge-like porous carbon/graphite absorber coated with a spectrally-selective metallic film, a copper heat-spreading layer, and an insulating bubble-wrap covering. Sunlight is absorbed, heat is localized and trapped, and capillary action draws water to a heated channel where it vaporizes at 100  deg C.",
    "detailed_description": "The device uses a porous carbon/graphite sponge that draws water upward by capillarity. A thin copper sheet coated with a spectrally-selective absorber (visible-absorbing, infrared-reflecting) captures solar radiation and conducts heat to a single evaporation channel. The whole assembly floats on a thermally insulating foam and is wrapped in clear bubble-wrap, which lets light in while reducing convective heat loss. Experiments showed the structure could heat water to its boiling point and convert ~20 % of incident sunlight into steam under ambient, even overcast, conditions. Earlier versions achieved 85 % conversion under 10-sun simulated illumination.",
    "category": "Thermal Systems",
    "principles": [
        "Solar thermal absorption",
        "Thermal concentration and localization",
        "Capillary water transport",
        "Convective heat loss reduction",
        "Spectral selectivity (visible absorption, infrared reflection)"
    ],
    "scientific_domains": [
        "Thermal Engineering",
        "Materials Science",
        "Mechanical Engineering",
        "Fluid Mechanics"
    ],
    "mechanisms_of_action": [
        "Solar photon absorption by spectrally-selective coating",
        "Heat spreading through copper layer",
        "Insulation via bubble-wrap and low-conductivity foam",
        "Capillary rise of water through porous sponge",
        "Phase change to steam at heated channel"
    ],
    "materials": [
        "Graphite",
        "Carbon foam",
        "Copper sheet",
        "Spectrally-selective metallic coating",
        "Polyethylene bubble-wrap",
        "Thermally insulating foam (e.g., polystyrene)",
        "Porous carbon sponge"
    ],
    "energy_sources": [
        "Sunlight"
    ],
    "inputs": [
        "Water",
        "Sunlight"
    ],
    "outputs": [
        "Steam"
    ],
    "claimed_performance": "Steam generation at 100  deg C under ambient sunlight; ~20 % solar-to-steam conversion efficiency; earlier prototype achieved 85 % conversion under simulated 10-sun illumination.",
    "experimental_evidence": "The authors placed the solar sponge on a roof and on a floating platform, observing water heating to boiling temperature and steam production even on overcast days. Efficiency was measured as 20 % of incident sunlight converted to steam.",
    "replication_status": null,
    "keywords": [
        "solar steam",
        "thermal concentration",
        "capillary water transport",
        "spectrally selective absorber",
        "floating solar receiver",
        "desalination"
    ],
    "related_technologies": [
        "Solar stills",
        "Solar thermal collectors",
        "Photothermal membranes"
    ],
    "controversy_level": "low",
    "confidence_score": 0.9,
    "practicability_score": 0.8,
    "fringe_score": 0.2,
    "evidence_strength": 0.7,
    "risk_score": 0.1,
    "trl_estimate": 6,
    "source_urls": [
        "http://www.nature.com/articles/doi:10.1038/nenergy.2016.126",
        "http://rexresearch.com/",
        "http://rexresearch1.com/"
    ],
    "organizations": [
        "Massachusetts Institute of Technology (MIT)",
        "Masdar Institute of Science and Technology"
    ],
    "applications": [
        "Desalination",
        "Residential water heating",
        "Wastewater treatment",
        "Medical tool sterilization"
    ],
    "limitations": [
        "Short operational lifespan (1-2 years before replacement)",
        "Performance drops with low solar intensity",
        "Convective heat loss still present despite insulation",
        "Scalability of bubble-wrap insulation for large-area devices"
    ],
    "open_questions": [
        "How to extend device lifetime while maintaining low cost?",
        "Can the design be scaled to industrial-size desalination plants?",
        "What are the long-term durability effects of UV exposure on bubble-wrap and selective coating?",
        "Can alternative, more durable selective absorbers improve efficiency?"
    ],
    "red_flags": [],
    "evidence_quotes": [
        "The structure heated water to its boiling temperature of 100 degrees Celsius, even on relatively cool, overcast days.",
        "The sponge also converted 20 percent of the incoming sunlight to steam.",
        "In ambient sunlight, the researchers found that, while the black graphite structure absorbed sunlight well, it also tended to radiate heat back out into the environment.",
        "The bubble wrap, combined with the selective absorber, kept heat from escaping the surface of the sponge.",
        "This low-tech design could operate for one to two years before needing to be replaced."
    ]
}