What is the main source of energy

Evaporation as a renewable energy

Promising potential: Similar to the sun and wind, evaporating water can also be used as an energy source. Researchers have now calculated how much energy the use of this ubiquitous natural phenomenon could theoretically generate in the future. According to this, evaporation has the potential to produce comparable amounts of energy as other renewable resources. The decisive advantage: Their availability is subject to significantly lower fluctuations.

Evaporation is a ubiquitous phenomenon. The process in which water gradually turns into a gaseous state influences water resources, weather and climate - and is an important source of energy in nature: Many plants use the power of evaporation to move their spore capsules and stomata, and hygroscopic, Hydrophilic materials convert a moisture gradient into mechanical energy.

However, the evaporation energy of water can also be used on a larger scale, as the latest research results show. Two years ago, scientists succeeded in using the power of evaporation as a source of electricity: They developed a nano-material that, when the humidity changes, expands and contracts like a muscle and thus functions as a motor and, for example, drives a generator can.

Unknown potential

Evaporation seems to have a previously unused force. Could another form of renewable energy soon be available to mankind in addition to solar energy, wind power and geothermal energy? In principle, that would be conceivable. How great the potential of evaporation as an energy source of the future really is, however, has so far been a matter of uncertainty.

Researchers led by Ozgur Sahin from Columbia University in New York have now investigated this question. They wanted to know: how much energy could evaporation, which is omnipresent in nature, ideally produce with the help of such evaporation machines? They calculated this on the basis of weather data and model simulations using the example of the USA.

325 gigawatts of energy

The results sound promising: Theoretically, evaporation from lakes and large water reservoirs alone could generate up to 325 gigawatts of energy on the surface of the USA - according to the team, that is more than 69 percent of the electrical power that the USA generated in 2015 have produced.

The simplified model does not yet include evaporation over the Great Lakes region. The conditions there would have made the model calculations too complicated and error-prone - but the five large contiguous freshwater lakes in North America are of course also an important source of evaporation.

More constantly available than wind and co

Overall, Sahin and his colleagues come to the conclusion that the resource evaporation could generate as much energy as wind and sun - with one crucial difference: sun and wind are often rare in many regions. Because the availability of these energies fluctuates greatly, they have to be stored at great expense. Evaporation, on the other hand, is more constantly available. “It could therefore be used as the main source of energy and supplemented with solar and wind energy,” says co-author Ahmet-Hamdi Cavusoglu.

And the use of water vapor has another advantage: around 50 percent of the water that normally evaporates into the atmosphere and is thus lost, could be captured during the energy generation process and made available for other uses. The scientists predict that particularly dry states such as California, Arizona or Nevada could benefit from this.

The team hopes that their study will stimulate research into new machines that use the power of evaporation to generate energy. Because so that one day we can really generate as much electricity from the evaporation process as the researchers' calculations have shown, the technology must first develop further. It is still in its infancy. (Nature Communications, 2017; doi: 10.1038 / s41467-017-00581-w)

(Columbia University, 09/27/2017 - DAL)

27th September 2017