A team of researchers has developed a stable battery cell that can directly convert heat into electricity, providing a way to use geothermal energy in a sustainable way.
According to a recent study, while currently used renewable energy sources such as wind and solar energy have their merits, there is a gigantic, permanent, and untapped energy source under our noses: geothermal energy.
Generating electricity from geothermal energy requires devices that can somehow make use of the heat within the Earth's crust.
Findings were published in the Journal of Materials Chemistry A.
Researchers have made great progress in the understanding and development of sensitized thermal cells (STCs), a kind of battery that can generate electric power at 100 degC or less.
Several methods for converting heat into electric power exist, however, their large-scale application is not feasible. For example, hot-and-cold redox batteries and devices based on the Seebeck effect are not possible to simply bury them inside a heat source and exploit them.
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The team of researchers had previously reported the use of STCs as a new method for converting heat directly into electric power using dye-sensitized solar cells. They also replaced the dye with a semiconductor to allow the system to operate using heat instead of light.
Electrons go from a low-energy state to a high-energy state in the semiconductor by becoming thermally excited and then get transferred naturally to the electron transport layer (ETM).
Afterward, they leave through the electrode, go through an external circuit, pass through the counter electrode, and then reach the electrolyte. Oxidation and reduction reactions involving copper ions take place at both interfaces of the electrolyte, resulting in low-energy electrons being transferred to the semiconductor layer so that the process can begin anew, thus completing an electric circuit.
After testing, the team observed that electricity indeed stopped flowing after a certain time and proposed a mechanism explaining this phenomenon. Basically, current stops because the redox reactions at the electrolyte layer stop owing to the relocation of the different types of copper ions.
Most importantly, and also surprisingly, they found out that the battery can revert this situation itself in the presence of heat by simply opening the external circuit for some time; in other words, by using a simple switch.