From Brand New Guest Blogger Megan Nichols: Can Osmosis Pave the Way for Clean Energy?

Water has long been a form a renewable energy through massive dams that provide hydroelectric power. Now it can become a new form of water power with a natural process of using salt water known as osmosis.

How Osmosis Works

Osmosis is the movement of molecules in a solvent through a semi-permeable membrane. The molecules move from a high-concentrated solution to a low-concentrated solution on the other side of the membrane. Osmosis is often performed with water as the solvent, although there are some misconceptions about the process as water isn’t the single driving factor behind osmosis —other liquids and gases can act as solvents.

The ions created by the dissolved salt in saltwater need some force to pass through the membrane. Brownian motion — the random movement of particles — as well as the pressure differential help provide the momentum to pull water through the membrane.

Membrane Power

The movement of ions is what serves as the central part of the process. Ions are atoms with an electrical charge, so they can be a potential source of energy. That is what interested researchers at the Ecole Polytechnique Fédérale de Lausanne (EPFL) Nanoscale Biology division. They developed an energy generator system that uses an incredibly thin — three atoms thick — molybdenum disulfide membrane.

The ions that pass through the membrane’s nano-sized pore convert into the electrodes used to generate an electric current. The membrane’s properties make it so that positive ions pass through while the negative ions stay, creating voltage. To reach the best level of electrical current, the researchers made the membrane atom-thin to increase the strength of the current. The current system developed at EPFL runs on a nano-transistor.

The History of Osmotic Power

The actual concept of osmotic power is not entirely new. Its theoretical foundation started in the late 19^th century, but since then, scientists have continued research of membranes and processes that would produce power.

Now that there are more inexpensive materials available, it is possible to produce the theoretical synthetic membranes necessary for the process chemical engineer Sidney Loeb called practical reverse osmosis, or PRO.

PRO: Re-energizing the Green Energy Landscape

The impact osmotic power can have to renewable energy is significant. Both solar and wind power have their own drawbacks. While solar panel technology and infrastructure has become more inexpensive, there is no constant exposure of sunlight. The same goes with wind power — it isn’t always blowing into the turbines.

Water can serve as a year-long source that is cost-effective and persistent as it flows from the river into the sea. The osmotic power from PRO we can make systems that, with membranes of 1m² covered with 30 percent of nanopores, can produce 1MW of electricity. That is enough to power 50,000 standard energy-saving light bulbs. With the proper expansion of membrane, it can power thousands of households.

Alternative Benefits of Osmosis Energy

Energy produce via PRO also has the potential to help with our water consumption needs. According to estimates, though our planet is 70 percent water, freshwater only makes up 2.5 percent. Additionally, only one percent is accessible — the rest exists as glaciers or remains deep underground. Our growing population requires better sources of clean water.

Desalination of seawater has the potential of becoming a great provider of clean water. Desalination plants normally work through reverse osmosis, but the process is expensive. With PRO, it finally harnesses the energy and applies it as a productive part of the desalination process. The power that osmosis generates may be enough to cut down on the high costs of producing freshwater from saltwater or brackish water.

A Riverbed of Beginnings

The first attempts at making osmotic power a practical reality is starting in estuaries. Their natural flow of the freshwater of the river into the sea makes them the best candidates for osmotic power system. There are pilot projects created by Norway, Japan and the US, among other nations. Scientists are also working on ways to increase the scale of their projects by finding a way to make the pores as uniform as they can.

These estuary projects are currently small in scope. However, they come with the hope of bringing the steps in producing electricity that will one day power millions of homes.