We chose salt as the core material for our battery because it is cheap, safe, and very good at storing heat. Ordinary salt is abundantly available, non toxic and easy to transport, which makes it suitable for use in normal households. When heated, salt can hold a large amount of thermal energy for a long time and release it slowly and predictably when needed. It is also stable at high temperatures and can be reused many times without losing its properties. This makes salt a sustainable and cost effective choice for storing excess solar energy as heat.