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Freshwater and Electricity Through Osmosis


waterRobert McGinnis, Yale doctoral student and Menachem Elimelech, Chair of Chemical and Environmental Engineering, have developed systems that can harness the power of osmosis to transform non-potable water sources like seawater to freshwater and generate in the same time electricity. Conventional desalination process and reuse of water have high energy consumption. Desalination and reuse are the only options to increase water supply around the globe. Bad water management could have a huge impact later in the history of mankind.

The technology made by the two Yale engineers has only one-tenth energy consumption than the conventional methods. Their process uses low temperature heat sources such as waste heat from conventional power plants.

“The cost of producing electricity by this method could be competitive with existing means of power production” says Elimelech.

The technology uses “forward osmosis”, making water pass through a semi-permeable membrane. Pure water is drawn from its contaminants to a salted solution, which can easily be removed with low heat treatment.

Using the same principle, the team has also designed a device to generate electricity from lower-temperature heat sources, using pressure-retarded osmosis. The “draw” solution is kept under high hydraulic pressure. When water moves into the solution, the pressure of the expanded volume is released through a turbine which generates electricity. The applied hydraulic pressure can be recovered by a pressure exchanger like the ones used in the modern reverse osmosis desalination plants, making this process to be a closed loop process.

Water management issues have been highlighted by the European Environment Agency as one of the areas that will dominate policy discussions in the coming year.

Yale scientists are doing research also to make an osmotic heat engine.

[via eurekalert.org]

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  1. Great post. I have a question though, if traditional methods are already in place, what would be the cost of modifying to your methods. Also what would be the average cost of installation for a moderate sized community, or can this be adapted for single use and therefore impact of infrastructure is not worn by the whole community.

  2. Does this suggest that the entire process is not only energy neutral, but in fact nets a positive energy outcome? That’s amazing. I wonder what’s happened with this method since this original writing.


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