Converting Heat Into Electricity
A team of engineers turned a piece of wood into a flexible membrane that converts heat energy into electricity, even with slight temperature changes.
It is easy enough to generate charge between two environments with very different temperatures, but with minimal differences it is a difficult task. However, a research team from the University of Maryland found a solution using the natural unique structure of wood. Each tree has special channels through which the plant moves water between roots and leaves. They, in turn, consist of fractally smaller channels, and at the cellular level their cross section can be less than one nanometer. It was this feature of the material that scientists used in their invention..
For this they Linden has been specially treated by removing two components from it: lignin, which makes the wood brown and gives strength, and hemicellulose entwining and binding cell layers. This process made the material flexible and transformed the structure of the remaining cellulose from type I to type II, which significantly affects increasing ionic conductivity.
Next, the membrane obtained from a thin piece of wood, the engineers impregnated with a sodium-based electrolyte and edged with platinum electrodes. In cellulose under the influence of temperature, an electric field arises on the nanofibers of the channel walls, which helps to regulate the movement of ions.
According to scientists, after the penetration of the electrolyte into the cellulose membrane and the application of an axial temperature gradient, the ionic conductor exhibits a thermal gradient coefficient (similar to the Seebeck coefficient in thermoelements) equal to 24 mV K-1. Sodium ions of the electrolyte penetrate into the channels due to the formation of the crystalline structure of cellulose and dissociation of the surface of functional groups.
The invention can be used as a highly efficient ion-selective membrane for biocompatible and environmentally friendly devices that convert heat into electricity. In perspective, they someday will be able to use the heat of the human body to generate electricity.
Recall that another group of engineers from Maryland found a way make wood more than ten times stronger, creating an inexpensive and lightweight alternative to most metals and alloys.
text: Ilya Bauer, photo: University of Maryland, inhabitat, chemistryprofession