[Sea Water Desalination] Preliminary Research and Documentation

The following research and documentation is meant to get this project started. Please consider this a work in progress. Significant work is needed to move this project forward.

Evaporating and Condensing Sea Water using Peltier module.

A Peltier module is an electronic device that has a unique property of heating up on one side and cooling down on the other side when a DC current is passed through it. It uses very little power and can last anywhere between 3 to 5 years depending on the manufacturer. It's a low cost electronic device - a matchbox-sized DIY costs about USD 3.00. 

Components required

The following components are required to set up the Peltier module method:

• Peltier module devices - connected in series.
• Heating chamber - An aluminum or copper container that can hold sea water. The inlet of this container must be controlled using a tap/faucet/stopper
• Cooling chamber - An aluminum or copper container. The insides of this container must be insulated with an insulation material. The base, however is not insulated - it must touch the cooling surface of the Peltier module.
• Connecting tubes - The connecting tubes conduct water vapor from the heating chamber to the cooling chamber.
• Fan - A fan is needed to pull air from atmosphere and push it towards the cooling surface of the Peltier module. 
• Collection chamber - A chamber that collects pure water from the cooling chamber.
• Solar electricity source - An electricity source that can power the Peltier module and the fan.

The following is a schematic diagram of the Peltier module system to evaporate salt water and collect pure water in the collection chamber.

Figure 1 - Schematic diagram of the Peltier module system for desalination of sea water.

The system consists of a heating chamber and a cooling chamber that are built on each side of the Peltier module. Sea water is pumped in into the heating chamber. The heating side evaporates the sea water. The water vapor is then conducted into the cooling chamber. The cooling chamber consists of a fan that sucks in air from the environment and pushes it on to the cooling side of the Peltier module. When the water vapor and the air mix and come in contact with the cooling side, they condense and form water droplets. These droplets are then collected in a fresh water chamber and pumped up into tanks and can be used for drinking or transportation. 

The fan and the Peltier module unit can operate on solar energy.

Solar Desalination Dome

A solar desalination dome is a variant of other solar desalination devices. It maintains a steady supply of sea water by gravity and water pressure and creates water vapor constantly. This can be collected in a collection chamber and used for drinking purposes. This method is slower than reverse osmosis or the Peltier method, and uses no electrical energy to desalinate sea water.

Components:

The following components are needed to build the solar desalination unit:

• Glass dome
• Heat absorption basin
• Collection chamber
• Hydraulic ram pump

Figure - Schematic diagram of the solar desalination unit.

The entire unit is placed at a position where there is maximum exposure to sunlight. A pipe is connected to the heat absorption basin in such a way that there is always sea water at the optimal level. This can be achieved by using a hydraulic ram pump. Alternatively you can use a small pump to pump the water into the heat absorption basin.

The sea water in the heat absorption basin is constantly exposed to sunshine. The carbon-coated heat absorption material absorbs heat from the sunshine and heats up the sea water. Due to the heat, water molecules in the sea water vaporize to form water vapor and settle on the insides of the glass dome as water droplets. 

Note: In this process, the salt saturation is constantly being reset as new salt water keeps entering the heat absorption basin. Concentration of brine is negligible and is automatically released in small amounts in the sea water. 

As the water droplets join one another, their weight increases, and they start trickling along the inner side of the glass dome to a channel that runs along the diameter of the glass dome. This channel has an outlet where fresh water is collected.

Mixing water from both methods

Licensing

This project is being developed as an open-source project with the following licensing: