I want a ppt about salt water electricity generation

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Can you please give me? I want it for information

The new device, developed by researchers at Stanford University, consists of an electrode that attracts positive sodium ions and one that attracts chlorine negative ions. When electrodes are immersed in salty water, they draw out sodium and chlorine ions from the water, and the movement of the ions creates an electric current. The electrodes are recharged by draining the salt water, replacing it with fresh water, and applying a relatively low voltage electrical current, which pulls the ions back from the electrodes. When fresh water is drained, the electrodes are ready to attract more ions from the next batch of salt water.

"It's the opposite process of water desalination, where it gets into energy and try to generate fresh water and more concentrated salt water," says Yi Cui, a professor of materials science and engineering at Stanford University and Lead author of the study. "Here they begin with fresh water and concentrated salt water, and then generate energy."

The Cui group converted electricity to 74 percent of the potential energy that exists between salt water and fresh water, without decreasing in operation over 100 cycles. Placing the electrodes close, Cui says, could allow the battery to reach 85 percent efficiency.

A power plant using this technology would be based near a river delta where fresh water meets the sea. Drawing 50 cubic meters of river water per second, Cui says, a power plant could produce up to 100 megawatts of power. He estimates that if all the fresh water of all the world's coastal rivers were tapped, its salinity gradient process could generate 2 terawatts, or about 13 percent of the energy currently used around the world.

This large-scale use, however, could seriously disrupt sensitive aquatic environments. "I think we would only be able to use a very small fraction of this or it would be an ecological disaster," says Menachem Elimelech, director of Yale University's Environmental Engineering Program. Elimelech says it would be necessary to pre-treat the water to remove suspended material including living organisms. Such processing would require energy, add costs, and seriously harm the ecosystem if it were to be done on a large scale.

Earlier efforts to collect energy from the salinity differential between saltwater and freshwater have focused primarily on a process known as pressure-delayed osmosis. In this approach, fresh water and salt water are housed in separate chambers, which are divided by an artificial membrane. Higher saltwater salinity attracts fresh water through the membrane, increasing pressure on the saltwater side. Pressurized water is then used to power a turbine and generate electricity.

Norwegian power company Statkraft is currently testing pressure-delayed osmosis at a pilot plant outside Oslo and is also working to develop more efficient and durable membranes. Statkraft officials say their goal is to convert 80 percent of available chemical energy into electricity. Cui says he doubts that the approach will be able to overcome an efficiency of 40 percent. "In terms of efficiency, we are certainly much better off," he says.

To achieve high efficiency, the Cui group used manganese dioxide nanorods for the positive electrode of their battery. The material gives sodium ions about 100 times more surface area to interact than conventional electrode materials. And the nanostructure allows the ions to quickly connect and separate from the electrode, making the whole battery more efficient.

The Cui team used a silver electrode to bond with negatively charged chlorine ions. Silver, however, is prohibitively expensive for large-scale deployments, and is also toxic, capable of causing environmental damage if it dissolves in the water circulating through the battery. Cui says his group is looking for a substitute, but an alternative can be difficult to find.