Cruel irony – the surface of the Earth is covered with water, but most of it is undrinkable. If scientists could find a way to remove the salt, compounds, and bacteria that make water unfit for drinking, humanity would get rid of one of the fundamental problems.
One of the simplest ways to do this is to use the fundamentals of the physics of evaporation and re-condensation of water. Researchers at the Dalian Maritime University in China have developed a new desalination plant that can float on the surface of seawater, efficiently absorb solar energy, and use that heat to evaporate water.
The block itself consists of three layers: the main part is polyethylene foam, which helps it float and acts as a heat insulator. Outside, the foam is wrapped in special paper – an absorbent material used in disposable diapers. It draws water up to the surface. The upper surface is coated with titanium nitride oxide (TiNO).
In the solar field, TiNO is a common commercial solar absorbing coating. It is widely used in solar hot water systems and photovoltaic installations. Titanium nitride oxide has high solar absorption and low thermal emissivity. This means that it efficiently converts solar energy into thermal energy.
This unit is then placed in a solar distiller – a transparent plastic container with a tilted lid that captures condensed fresh water and directs it to a “collection point”. In tests, the team found that the new solar cell has a 46% efficiency in converting solar energy to water. In general, for single installations of this type, 30 to 40 percent are expected.
It is important to note that the device avoids one major mistake – contamination due to the accumulation of salts on the surface. Over time, this reduces its effectiveness. During testing, the team found that no salt layer had formed. This indicates that special pores on the block’s coating drain the salt and dump it back into the seawater. Another benefit, the team said, is that the paper material can be reused more than 30 times.
Scientists note the low cost and high efficiency of the development.