Energy from soil
doi:10.1038/nindia.2016.89 Published online 15 July 2016
Researchers from Sardar Patel University in Gujarat have reported a method to generate energy from sunlight by using a compound abundantly found in the soil1.
They explored the soil component called humic acid (HA), a natural polymer that they was absorbing a broad range of light in the visible region of the electromagnetic spectrum. They looked at using HA as a photo-sensitizer in a new class of solar cells — dye-sensitized solar cells or DSSCs — known for their high theoretical efficiency, easy fabrication and low manufacturing cost.
The major components of DSSCs are photo-electrodes, sensitizers, electrolytes, and counter electrodes. In their study, the scientists employed HA as a sensitizer by binding it onto the surface of photo-electrode titanium oxide (TiO2), which has been successfully employed as a light harvesting agent. The efficiency of such a device with HA-sensitized electrode "is better than that of devices with other natural sensitizers reported so far," the researchers say.
Unlike other natural sensitizers, HA, found in soil, wood, coal and seawater, shows longer stability, they say. Natural sensitizers are ideal candidates for environmentally friendly DSSCs because they are nontoxic, low in cost, renewable, and abundant in nature. DSSCs work even in low-light conditions and are attractive as a replacement for existing technologies in "low density" applications like rooftop solar," the report says.
1. Vekariya, R. L. et al. Humic acid as a sensitizer in highly stable dye solar cells: energy from an abundant natural polymer soil component. A C S Omega, 1, 14-18 (2016) doi: 10.1021/acsomega.6b00010