Harnessing sunlight to make fresh drinking water from sea water, The fully passive solar desalination system developed by researchers at MIT and in China can provide more than 1.5 gallons of fresh drinking water per hour per square meter of solar collector area.

Such a system can supply potentially dry offshore areas to provide an efficient and inexpensive source of water.

This system uses several layers of evaporator and flat solar condenser, arranged vertically and covered with transparent air insulation.

The key to system efficiency is the way each stage of water desalination is used. At each stage, the heat released by the previous stage is used instead of being wasted. Harnessing sunlight to make fresh drinking water from sea water.

In this way, the team’s demonstration device achieved an overall efficiency of 385 percent in converting solar energy into water evaporation energy.

This device is basically a multi-layer solar system with a number of evaporation and condensation components, such as those used to filter liquids. He uses a flat plate to absorb heat and then transfer heat to the water layer so that it starts to evaporate. The steam is then condensed on the next plate.

This water is collected when heat from condensation of steam reaches the next layer.

Every time steam condenses on the surface, heat is released. In a typical condenser system, this heat just disappears into the environment. With this multi-layer evaporator, the heat released goes to the next evaporation layer, which means that solar heat is returned and overall efficiency is increased.

Adding more layers increases the conversion efficiency of drinking water production, but each layer also increases the system cost and volume. The team chose a 10-tier detection system that was tested on the roof of the MIT building. This system provides clean water that exceeds city drinking water standards at a rate of 5.78 liters per square meter (about 1.52 gallons per 11 square feet) of solar collector area. Harnessing sunlight to make fresh drinking water from sea water.

This is more than double the record number previously produced as a passive solar desalination system, the researchers said.

In theory, such a system with more desalination and further optimization stages can reach an overall performance level of up to 700 or 800 percent, according to the researchers.

Unlike some desalination systems, there is no accumulation of concentrated salt or saline that needs to be removed. According to the free-floating configuration, any salt that accumulates during the day is only transported through sediment and returned to sea water overnight, according to the researchers. Harnessing sunlight to make fresh drinking water from sea water.

Your demonstration unit consists mostly of materials that are cheap and available, such as. B. Commercially available black sun absorber and capillary paper towels with which water is brought into contact with the solar absorber.

In most other efforts on passive desalination systems, solar energy absorbers and washing agents are the single components that require special and expensive materials, the researchers said.

The most expensive prototype component is the transparent airgel layer, which is used as an insulator on a pile. However, the team suggested using other, more expensive insulators as alternatives. (Airgel itself is made from inexpensive silica powder, but special drying equipment is needed to make it.)

Wang emphasized that the team’s main contribution was a framework for understanding how to optimize such a multi-stage passive system, which they called thermally localized multi-stage desalination.

The formula they developed might be applicable to different materials and device architectures to further optimize the system based on different work scales or local conditions and materials.

Possible configurations are floating panels on salt water bodies, for example retention tanks. They can passively and passively send fresh water through pipes to the beach as long as the sun shines every day.

Other systems can be designed for households, for example with flat screens in large flat sea water tanks that are being pumped or transported. The team estimates that a system with around 1 square meter of solar collector area can meet a person’s daily drinking water needs.

They believe that a system can be built in their production that will meet family needs for around $ 100.

Researchers are planning further experiments to further optimize material selection and configuration and to test system robustness under realistic conditions. They will also work to change the design of their laboratory equipment into something that is easy to use.

The hope is that this will ultimately help reduce water shortages in some developing countries where reliable electricity is scarce but sea water and sunlight are abundant.