How much heat a material can store is called thermal mass or heat capacity. One of materials that can store the most heat per kilogram happens to be regular old water.
I wonder if anyone here could do the math of how many kilograms of water would be needed to absorb the day/night temperature changes of a desert and keep a human body inside at an acceptably stable temperature.
I'm kinda afraid the weight would be more than enough to crush any human into a bloody pulp?
The most effective way to store a whole lot of heat in very little mass is to use phase changes - some materials take an enormous amount of energy to transition from solid to liquid and vice versa. This can be used to pack a lot of thermal energy into very little volume with very little temperature change.
