The research, involving scientists from Almería, Germany, Valencia, and Nottingham, explores the potential of heating solar salt, a material used in thermoelectric solar plants, using electromagnetic radiation at high temperatures.
Solar salt, a mixture of sodium nitrate and potassium nitrate, typically operates in a liquid state between 290 and 565 degrees Celsius. Its function is to store thermal energy for later recovery in Power-to-Heat-to-Power systems, also known as Carnot batteries.
The study addresses the challenge of efficiently introducing heat into molten salt, as its low thermal conductivity can cause local overheating. Microwaves are being considered as an alternative for more uniform heating, but experiments reveal that their penetration into molten salt is very limited, only a few millimeters.
Researchers have measured the electromagnetic properties of the salt at frequencies of 2.45 GHz and 912 MHz, observing a drastic change in its behavior when transitioning from solid to liquid state, where it becomes highly conductive.
In response to this limitation, solutions such as using ceramic structures transparent to microwaves are proposed to increase the interaction depth and improve heat distribution. One idea involves circulating the liquid salt through tubes within a microwave cavity, incorporating honeycomb or foam-like ceramic structures.
This advancement, published in the journal Energy Conversion and Management, represents an essential experimental step towards determining the viability of new methods for storing surplus renewable electricity, which is key to better harnessing solar energy.
