It uses phase change (solid to liquid) to store heat at about 200 kJ/kg. Compare this to heating water in a boiler from 10c to 60c - stores 209 kJ/kg.
So we already have an effective way to store heat which can work for decades without servicing and is also cheap to produce (in terms of money and energy consumption).
So we already have an effective way to store heat which can work for decades without servicing and is also cheap to produce (in terms of money and energy consumption).