A method and system for efficiently cooling a fluid is provided. A cooling system includes a first chamber containing a first fluid, and a second chamber connected to the first chamber and containing a second fluid. The cooling system further includes one or more thermoelectric devices for cooling the second fluid in the second chamber, and a first body that acts as a thermal diode. The first body enables unidirectional transfer of heat from the thermoelectric devices to the first fluid. Further, the cooling system can be installed with one or more phase change materials or heat pipes that enhance the cooling efficiency of the cooling system. The thermoelectric devices are switched on for a certain time period, after which they are switched off and on repeatedly in cycles, depending on the temperature of the second fluid.