**2.4 Chemical point of view**

PCMs should be reversible freeze/melt cycle. PCMs should be chemical stability i.e. functional groups contained in PCMs does not change after repeated thermal cycle. PCMs should be non-toxic, non-flammable and non-explosive materials for safety and Non-corrosiveness to the construction materials.

#### **2.5 Economic point of view**

PCMs should be easily available and low cost owing to minimize total cost of solar energy system.
