Thermal energy is the internal energy present in a system due to its temperature and ‘thermal energy storage systems’ allow for excess thermal energy to be stored for days or even months later. With most practical solar heating systems providing storage for only a few hours to days, seasonal thermal energy storage (STES) systems provide a better solution. These storage systems enable solar energy to be stored in summer for space heating use during the winter.  The STES systems also work in conjunction with molten salts (a mixture of potassium Nitrate, calcium nitrate, sodium nitrate, lithium nitrate, etc.)  that have the ability to absorb and store the heat energy that is released into water for transfer when needed.

These devices require complex pumps, pipelines, and heat transfer fluids to create electricity making them expensive and susceptible to safety issues. Along with this, they are not built with particularly abundant materials (materials listed in first paragraph). This is why scientists and researchers all over the world are looking for cheaper and more abundant materials (Science Daily).

At the Universidad Polytechnic de Madrid they may have done just that! A team at the universidad has proposed a silicon-based solution.  The proposed new thermal energy storage system involves heating the silicon in a container using concentrated sunlight on surplus electricity generated by renewable power. The molten silicon can reach temperatures of 1,400° C or 2,552° F and its unique properties allow it to store more than 1 MWh of energy in a cubic meter which is ten times more energy than the current salt solution (New Atlas).

The key component to make the new systems work is thermophotovoltaic cells that are a relatively new technology creating energy from heat as well as light. Thermophotovoltaic cells can reach higher efficiency, produce more electrical power, and operate at extreme temperatures compared to conventional solar cells. The new system uses abundant and inexpensive materials (silicon), stores more energy, is compact and quiet, and has no moving parts making it safer.  This will dramatically reduce the cost of storing and producing energy in this sector.

Hats off to scientists and researchers who continue to better our world through inventions and creations such as this!