{
    "title": "Low-Energy Desalination",
    "inventor_name": "Nagamany NIRMALAKAHANDAN et al",
    "publication_year": 2007,
    "device_name": "Low-Energy Desalination System",
    "goal": "Convert saline water into potable water using low-grade thermal energy with minimal electricity consumption.",
    "problem_addressed": "High energy demand and cost of conventional desalination methods such as reverse osmosis and multi-effect flash distillation.",
    "concept_summary": "The system uses gravity-driven barometric pressure columns to create a near-vacuum headspace, allowing water to evaporate at low temperatures (~=40-50  deg C) and condense on the opposite side. Low-grade heat from solar collectors, waste heat, or absorption refrigeration is stored in a thermal energy storage tank to maintain the required temperature differential, enabling continuous desalination with virtually no moving parts.",
    "detailed_description": "A prototype consists of three vertical columns (~=10-11 m tall) - a saline water column, a brine withdrawal column, and a desalinated water column - connected by a horizontal tube. The height creates a pressure head that generates a vacuum in the headspace. By heating the headspace of the saline column 10-15  deg C above the desalinated column, water evaporates from the saline side and condenses as fresh water on the opposite side. A thermal energy storage (TES) unit stores low-grade heat supplied by solar panels or waste heat from an absorption refrigeration system (using LiBr-H_2O refrigerant). The system operates continuously, requiring only an initial start-up pump and no other mechanical moving parts.",
    "principles": [
        "vacuum distillation",
        "gravity-driven barometric pressure head",
        "low-grade thermal energy utilization",
        "thermal energy storage",
        "absorption refrigeration"
    ],
    "scientific_domains": [
        "Thermodynamics",
        "Chemical Engineering",
        "Environmental Engineering"
    ],
    "mechanisms_of_action": [
        "evaporation under near-vacuum",
        "condensation of vapor on cooler column",
        "heat exchange between brine and feed water",
        "thermal storage to maintain temperature differential"
    ],
    "materials": [
        "water",
        "saline water",
        "brine",
        "LiBr-H_2O refrigerant"
    ],
    "energy_sources": [
        "low-grade waste heat",
        "solar thermal energy",
        "heat from absorption refrigeration"
    ],
    "inputs": [
        "saline water feed",
        "low-grade heat (~=40-50  deg C)",
        "solar energy (optional)"
    ],
    "outputs": [
        "desalinated (potable) water",
        "brine concentrate"
    ],
    "claimed_performance": "Prototype can continuously supply a four-person household; feasibility study reports ~4.5 kg hr^-^1 desalinated water using ~208 kJ kg^-^1 of water (~=3.25 kW heat input).",
    "experimental_evidence": "A 30-ft tall NMSU prototype powered by a solar panel produced continuous fresh water for a four-person household; simulation and bench-scale tests showed 4.5 kg hr^-^1 desalination at 40-50  deg C with a 3.25 kW heat source.",
    "replication_status": "Prototype built and demonstrated at New Mexico State University; no independent third-party replication reported.",
    "keywords": [
        "low-grade heat",
        "vacuum distillation",
        "thermal energy storage",
        "desalination",
        "gravity-driven pressure head",
        "absorption refrigeration"
    ],
    "related_technologies": [
        "solar still",
        "multi-effect flash distillation",
        "absorption refrigeration system"
    ],
    "controversy_level": "low",
    "confidence_score": 0.9,
    "practicability_score": 0.8,
    "fringe_score": 0.2,
    "evidence_strength": 0.6,
    "risk_score": 0.1,
    "trl_estimate": 5,
    "source_urls": [
        "http://www.lcsun-news.com/news/ci_5998479",
        "https://patents.google.com/patent/US2012085108"
    ],
    "organizations": [
        "New Mexico State University",
        "New Mexico Water Resources Research Institute"
    ],
    "applications": [
        "household water supply",
        "remote or off-grid communities",
        "brine waste-heat recovery"
    ],
    "limitations": [
        "System height (~=10 m) may limit installation sites",
        "Requires a source of low-grade heat or solar collector",
        "Brine disposal still required"
    ],
    "open_questions": [
        "Long-term durability of the vacuum columns",
        "Cost and scalability for commercial deployment",
        "Performance under varying ambient temperature and humidity"
    ],
    "red_flags": [],
    "evidence_quotes": [
        "A prototype built on the NMSU campus in Las Cruces can produce enough pure water continuously to supply a four-person household.",
        "The system utilizes the natural effects of gravity and atmospheric pressure to create a vacuum in which water can evaporate and condense at near-ambient temperatures.",
        "A temperature increase of only 10 to 15 degrees is needed to drive the flow in the desired direction.",
        "Results of this feasibility study show that the thermal energy rejected by an ARS of cooling capacity of approximately 3.25 kW along with an additional energy input of approximately 208 kJ/kg of desalinated water is adequate to produce desalinated water at an average rate of approximately 4.5 kg/hr.",
        "The desalination system does not have a pump except for an initial starting pump. In addition, the system does not have any other moving parts."
    ],
    "category": "Thermal Systems"
}