A method and a system with which the buyer can modify the specifications of a product so as to make it satisfy the needs of the buyer, while allowing mass production and maintaining the marketability of the product. Cold storage units may further include systems for using the refrigerant of the refrigeration system to defrost one or more components of the cold storage unit, and for using the refrigerant to facilitate maintaining a desired internal temperature of the interior space of the cold storage unit. to produce a composite catalyst.