Generating electricity is a relatively simple thing, but it is made very complex by the fact that the world needs a massive amount of it and it is important to do it in as green a way as possible, without making it to expensive. Today, the bulk of the world’s energy still comes from burning fossil fuels like coal, but as new technologies are developed, an existing ones are improved, we are slowly moving in a greener direction.

One method of power generation that is quite new on the commercial scene is known as Osmotic power generation. In 2023, the first ever osmotic power plant came online in Denmark, and just recently the second one was brought active in Japan.

This method of power generation has some real potential because it doesn’t use any fossil fuels, and it is not reliant on the weather like wind and solar are. Instead, it can provide a steady stream of electricity all the time.

It works by harnessing the power of osmosis between fresh water and seawater. Water molecules naturally flow from places with high water concentration (fresh water) to places where there is low concentrations of water (salt-water). This is a very well-understood phenomena that is seen throughout nature.

For the purpose of generating electricity, the movement of water is used to spin turbines, which can be used to generate electricity. The plant sets up a thin barrier between fresh water and salt-water, and the pressure created spins the turbine without having to burn anything in the process, making it an emissions-free source of electricity.

Osmotic power generation is a great because it is clean and reliable, but it isn’t ideal in all places. First, it requires a reliable source of both fresh water and salt water. Next, it needs to use pumps (in most situations) to bring the water to the locations where it is needed. The electrical use of these pumps reduces the net output of the turbines. This was explained by Professor Sandra Kentish from the Department of Chemical Engineering at the University of Melbourne in The Guardian:

“While energy is released when the salt water is mixed with fresh water, a lot of energy is lost in pumping the two streams into the power plant and from the frictional loss across the membranes. This means that the net energy that can be gained is small.”

In some locations, however, the net energy gains can be optimized by various things. At this Japanese location, for example, the power plant is using concentrated seawater that is available from a nearby water desalination plant. The desalination plant removes water from the seawater, leaving it with high levels of salt. The fresh water comes from a water treatment center, so it is also readily available and it would be there whether this power plant existed or not.

Having the highly salty water and the fresh water available makes this power plant more efficient than it could otherwise be. The plant will yield a net power output of about 110 kilowatts, with a maximum annual production of 880,000 kilowatt hours. This is similar to what could be achieved with about two soccer fields covered with solar panels. The biggest benefit, however, is that the power is generated night and day, which is a big advantage over solar.

Having this method of power generation available to offset the shortcomings of solar and wind may be very effective in some areas of the world. Many in the power industry agree that the long-term solution to the world’s power needs won’t likely come from one single source, but rather from a balance of different electricity production technologies.

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