Electricity generated at estuaries using osmosis and light

October 16, 2019
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Osmotic energy is a source of power that’s naturally available at estuaries where fresh water comes in contact with seawater. The energy is now being tapped by researchers to develop a technology that would exploit the osmotic power (also known as blue energy).

In a laboratory experiment, researchers from EPFL’s Laboratory of Nanoscale Biology (LBEN), which is headed by Professor Aleksandra Radenovic at the School of Engineering, have highlighted that it was possible to optimize electricity production. They reproduced the real-world conditions normally occurring where rivers meet the sea (that is pH and salt concentration). And they showed that by shining light on a system inclusive of water, salt, and a membrane three atoms thick, it was possible to optimize the generation of electricity. Their findings have also reportedly been published in the journal Joule.

** Ions pass through a nanopore
The technology is now closer to real-world application with the addition of light. The system is inclusive of two liquid-filled compartments, at different salt concentrations, and separated by a molybdenum disulfide (MoS2) membrane. A nanopore (a tiny hole between three and ten nanometres in diameter) is in the middle of the membrane.

So, an electric current is generated, every time a salt ion passed through the hole from the high to the low concentration solution, and an electron is transferred to an electrode. The system is dependent on a number of factors and the nanopore and the membrane have to be highly charged with the presence of multiple identically-sized nanopores, which is a technically challenging process.

** Power of sunlight harnessed
The researchers used low-intensity laser light, so, as the light releases embedded electrons, they accumulate at the surface of the membrane, which increases the surface charge of the material. In this process, the nanopore is more selective and the current flow increases. In the context, Martina Lihter, a researcher at LBEN stated that they didn’t have to worry about the size of the nanopores and added that it was good news for large-scale production.

The research team will reportedly explore possibilities to scale up production of the membrane and also address a range of challenges including optimal pore density. A lot of work is still to be achieved before the technology can be used for real-world applications.