Evaporation is the process by which a substance passes from a liquid state to a gaseous state. As a rule, evaporation is the result of heating the substance to a certain temperature. It is thanks to evaporation that the water cycle is maintained on the Earth, and the Sun in this case acts as the evaporator. The scale of energy that is spent on the process of evaporation on the whole planet is in fact very great, although we do not notice it in our daily life.
According to Ozgur Sahin and his colleagues from Columbia University, water that evaporates from all rivers, lakes and dams in the territory of the modern US (excluding the Great Lakes) can provide up to 2.85 million megawatt hours of electricity per year. For comparison, this is equivalent to two-thirds of the electricity produced in all US states in 2015! And this despite the fact that in 15 out of 47 states the potential capacity of power plants exceeds the real demand for energy.
The engines of the future: everything is in the water
Researchers propose to install engines on freshwater reservoirs that would not only generate electricity, but also halve the intensity of the evaporation itself, which in many situations would save huge amounts of drinking water. However, this technology assumes that the water body will be covered with absorbing panels – which is highly undesirable. For starters, however, it is necessary to build the evaporation engine itself, but here the scientists have already demonstrated the full power of science and created several miniature but quite working prototype installations.
Test engines are based on materials that shrink when dried – for example, a ribbon covered with bacterial spores is involved in the design. Losing water, the spores shrink and contract, reducing the tape. Sahin compares the principle of this design with the muscular system, explaining that microscopic spores can stretch the tape with a rather large force. To avoid soil contamination due to repeated soaking and an abundance of chemicals, the prototypes regulate their work, depending on the change in the overall moisture level. For example, in one version of the engine, the “muscle” is located just above the water layer. When the evaporating moisture rises, the belts stretched according to the principle of the blinds are straightened and create slots due to which air enters into them and helps the tapes to dry up again and avoid overmoistening.
Advantages and Disadvantages of the Invention
The scientific community agrees that the potential of this invention is enormous. To date, the main problems are its use. Ken Caldeira of the Carnegie Institution for Science in Stanford, California, doubts that it is possible to effectively convert the energy of evaporation into electrical energy. In his opinion, industrial development of engines to the extent that their production will become massive, and the use of ubiquitous, is an extremely laborious task.
The main competitor of new engines are well known to all solar panels, since it is increasingly common for floating solar farms to be located in reservoirs. However, evaporative engines can be made from cheap biomaterials, which are easier to dispose of than solar batteries – and this is important.
If the technology gets spread, then its use will affect the local climate by changing the degree of evaporation of water. But this will have at least some significance only if the area of the closed surface is 250,000 km2 or more. However, when it comes to such a scale, any energy installation, no matter how environmentally friendly it is, will have an impact on the environment. Moreover, in rainy areas where frequent precipitation causes a lot of problems, reducing the intensity of evaporation of water will be extremely useful.