Today and in the future the demand on freshwater increases and not only in sunny countries, but also in a lot of other parts of the world. Right now a lot of people do not have enough freshwater for their daily life and in the future it grows more acute. One reason is the global warming and another reason is the rise of the worldwide population. Additional the available freshwater resources are polluted more and more. Therefore possibilities must be found to produce a huge amount of freshwater without producing a lot of carbon dioxide. Only with this combination the future freshwater demand and the problem of global warming can be tackled. One possibility to produce freshwater was shown in the Sunwater project, which was undertaken between 2009 and 2011. This project was a cooperation between Germany and Egypt and was initialized by this author. During this project it was researched if solar energy can directly be used to convert saltwater into freshwater without producing electrical energy, but this is just one possibility to produce usable freshwater for the daily life in an environmental friendly way. Another possibility is to use other waste heat sources for the desalination of saltwater or brackish water. The used desalination unit can be operated with in wide range available waste heat sources. These waste heat sources can come for example from power stations like gas power stations or nuclear power stations, from air conditioners or usable thermal waste heat from the steel industry. At the moment a lot of waste heat is produced with this installations, which is unused and released to the environment. With different technology combinations the already available thermal energy can be used for the operation of the desalination unit. If the waste heat comes from an environmental friendly energy source like nuclear power stations, geo thermal or solar thermal, the freshwater is also produced complete in an environmental friendly way. This great chance of using was- - te heat will be discussed in this paper.
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