Salt water can generate 1,000 times more electricity than a solar battery

It is possible to generate energy from the difference between saltwater and fresh water. When saltwater and fresh water are separated by a membrane of certain types of ions, there is a force that pushes fresh water into saltwater. And that power can be used to produce energy, the researchers named them "osmotic energy."

But the production of this type of energy depends very much on the speed at which an ion travels through the membrane: the thicker the membrane is, the slower it will flow. In theory, osmotic energy can be generated automatically with a thin diaphragm. But can this theory-based system be achieved in practice?

In theory, osmotic energy can be generated automatically with a thin diaphragm.

Recently, scientists have answered this question, using a thin diaphragm at the atomic level, made up of molybdenum-disulfide chemical compound (MoS2). In the resulting report, they describe a MoS ₂ membrane with a small nano-level filter hole (0.000000001m), which is used to prevent two large blocks containing two types of water with different salt concentrations, the purpose to create osmotic energy.

First, understand what is osmosis flow?

Not all ions can penetrate nano holes of MoS ₂ films. Surface charges at the nanofiltration limit ion rotation, so only certain ions can pass through the nano-hole, thereby creating a permeable ion stream. The size of the ion flow will be determined by the surface charges at the nanofiltration hole.

Examples of holes with nanometer size.

Analysis of the experimental results at pH 5 shows a negative surface charge exists at the nanofiltration hole. And as the size of the filter hole increases, the negative charge is accumulated more on the surface. This will cause negative ions to be unable to pass through the nanofilter hole (they will be bounced off) and allow positive ions to pass through. The result is a positive ion current passing through the diaphragm.

The researchers also found that the increase in the conductivity of the nanofiltration is directly proportional to the pH. They argue that this may be due to an increase in negative surface charge at this filter hole. Similarly, increasing the pH of the current increases the voltage and the current itself. All showed the importance of the amount of surface charge at the nanofiltration hole to the motion of the ion.

Effect of thickness and magnitude

To better understand this problem, the researchers wanted to test more about the effect of nanofiltration size on ion paths as well as affect the results of the amount of electricity produced. They found that ion selection of this filter hole decreases as the size of this filter hole increases. This is understandable, because the farther away the nano filter hole is, the less effects they will bring to the point between the filter hole.

The thickness of the diaphragm is also an important element in the amount of electricity that can be generated by this method.

According to the theory, the thinner the membrane, the greater the amount of electricity. A simulator is created, to test this problem and as expected, the amount of electricity generated is less when the number of layers increases. However, this is just a simulated experiment, the actual tests have not yet been conducted.

Only a simulated experiment, actual tests have not yet been conducted.

Another big question is how much energy is generated with a system that seems so simple? Scientists performed calculations by experimenting on a simulator consisting of a MoS ₂ layer of the thickness of one atom, 30% of the surface of the diaphragm containing 10-nanometer diameter holes (0.00000001). m). With a standard salt salt, you can obtain an energy density of 1,000,000 W / m ² . If you haven't figured it out yet, this is the amount of energy that we get from the solar cell that falls around 1,000 W / m2.

From that huge number, we see the potential of a huge source of renewable energy from the MoS ₂ membrane along with nanofiltration holes. Although there are still certain difficulties in creating a membrane at an atomic level large enough to produce a large amount of electricity, it is still possible to see the use of this technology, which is to generate electricity. power for electronic devices.