Goal
Produce fresh water from saline sources using only solar energy
Problem
High energy consumption of conventional desalination and salt fouling of solar-steam surfaces
Concept Summary
A disc made from super-hydrophilic filter paper coated with carbon nanotubes absorbs sunlight and converts it to heat. Water is delivered to the centre of the disc via a cotton thread; the heated water evaporates, producing steam while the salt is transported to the disc edge where it crystallises and can be harvested. The system achieves near-100 % salt removal and generates several litres of clean water per square metre per day.
Detailed Description
The device consists of a circular evaporation disc fabricated from a super-hydrophilic filter-paper substrate that attracts water. One side of the paper is coated with a thin layer of carbon nanotubes that provides broadband solar absorption (~94 % across the solar spectrum). A 1 mm-diameter cotton thread supplies saline water to the centre of the disc by capillary action. When illuminated, the nanotube layer heats the paper, raising its temperature from ~25 deg C to 50 deg C (dry) or from 17.5 deg C to 30 deg C (wet) within one minute, causing rapid evaporation. The generated steam condenses on a cooler surface to yield fresh water, while the dissolved salts are pushed outward by the capillary flow and crystallise at the disc edge, where they can be collected.
Principles
- Photothermal conversion
- Capillary water transport
- Edge-preferential salt crystallisation
- Gravity-assisted salt harvesting
Scientific Domains
Materials
- Super-hydrophilic filter paper
- Carbon nanotubes
- Cotton thread
Mechanisms of Action
- Solar absorption by carbon nanotubes
- Localized heating of water
- Evaporation of water
- Condensation of steam to fresh water
- Capillary-driven salt migration to disc edge
Energy Sources
Applications
- Provision of clean drinking water to remote communities
- Industrial wastewater treatment
- Mining tailings management
- Agricultural irrigation
Claimed Performance
6-8 L of clean water per m^2 per day; 94 % solar light absorption; near-100 % salt removal; 1.64 L m^-^2 h^-^1 water production in multistage membrane-distillation variant
Experimental Evidence
Tested with seawater from Lacepede Bay (South Australia); temperature rise from 25 deg C to 50 deg C (dry) and 17.5 deg C to 30 deg C (wet) within one minute; measured 94 % broadband light absorbance; produced 6-8 L m^-^2 day^-^1 of fresh water; MSMD version produced up to 1.64 L m^-^2 h^-^1 with no loss of solar-panel efficiency
Replication Status
Prototype tested in laboratory conditions; no independent third-party replication reported
Limitations
- Scale-up of the disc geometry and uniform sunlight exposure
- Long-term durability of the carbon-nanotube coating
- Handling and collection of edge-crystallised salt at large scale
