Systems for producing renewable energy, such as photovoltaic panels, wind turbines, geothermal and hydraulic power plants, could soon be enhanced by a new device: hydrovoltaic panels. In development for several years, cells exploiting the phenomenon of water evaporation could well experience significant growth in the near future, in particular thanks to the advances made in this area by a Chinese team.
In the race for renewable energies, photovoltaic panels have been a revolution by making it possible to produce electricity from solar light. A technology which, however, is not applicable in all environments, particularly at night. To overcome these limitations, scientists have been developing for several years a new system which exploits not solar energy, but another omnipresent natural phenomenon: evaporation.
The hydrovoltaic effect: enormous potential for the production of renewable energy
Exploiting this energy exchange which takes place everywhere on the planet, even without the addition of light, immediately presented enormous potential in terms of electricity production. Theoretically, the natural evaporation which affects lakes and other water reservoirs in the United States could thus produce 325 GW! The first prototypes of hydrovoltaic cells have therefore begun to appear. Several strategies were tested first using highly purified water, circulating in devices composed of silica nanofibers, which showed promising results for transforming the phenomenon of evaporation into electricity. Recently, the device has been improved to allow the use of sea water.
Hydrovoltaic devices were inspired by the passive pumping of plants, where the transport of water takes place thanks to the differential pressure established at the level of the microcapillaries by evaporation. On this model, engineers have constructed nanochannels embedded in a carbon film, in which a fluid circulates. By evaporating through these nanofibers, the fluid generates a sustained electrical voltage. An ingenious and innovative system which, however, requires a minimal supply of energy (solar), a continuous supply of water and low ambient humidity to function optimally. Conditions that are still too restrictive and that researchers from the Chinese Academy of Sciences have managed to lift.
A closed circuit that allows you to free yourself from external constraints
In order to free themselves as much as possible from external environmental conditions and allow the use of hydrovoltaic cells in any climate, scientists have in fact constructed airtight cells inside which units made of tissue paper have been placed. and carbon black. The production of electricity is then ensured by the closed circuit circulation of a small quantity of water within the capillaries of the tissue paper.
This new device, called hermetic hydrovoltaic cell (HHC), was presented in an article published by the journal Nature Communications. It promises the use of hydrovoltaic systems in any environment, whether dry or humid, without the contribution of sunlight. These cells in fact only use ambient heat as an energy source, allowing the production of steam inside the hermetic cells.
Tests have revealed the effectiveness of this system, with autonomous production of electricity for more than 160 hours. But the researchers believe the cells could function as long as desired, as long as a heat source is available. By eliminating the need for water, this device could easily be implemented in extreme environments such as deserts or tropical zones, or to ensure electricity production in very isolated regions.
Power generation day and night
Furthermore, temperature fluctuations do not seem to negatively affect electrical efficiency here, quite the contrary. These variations would make it possible to strengthen the circulation of water within the hermetic cells, maintaining the hydrovoltaic effect and therefore continuous production of electricity.
Compared to photovoltaics, this new device therefore has the advantage of being able to operate day and night, without being affected by external climatic conditions (wind, variations in brightness, temperature and humidity). Use in much more specific environments is also envisaged, such as during work in underground environments (mines, tunnels, etc.).
The researchers highlight the ease of implementation and especially the low cost of this type of device. So many characteristics which should ensure a bright future for future hydrovoltaic panels, thus making it possible to complete and diversify the offer of renewable energy solutions.
