A modular assembly comprising several adjacent modules joined together by means for circulating a flow and which each contain at least one volume wherein there is a refrigerant fluid or coolant circulating in the said volumes under the action of circulation means and elements for storing and restoring a thermal energy.At least one first layer comprising at least one MCP material is disposed at the periphery of at least some of the modules, including on one side wherein two adjacent modules face each other and wherein at least a portion of at least one second layer comprising a thermally insulating material is also interposed.