For many different reasons there is a great potential for a system capable of storing and using waste motor heat of cars to provide heating or cooling. If such a system has a high storage density application in electrical and hybrid vehicles may be interesting.The SWEAT system, in which SWEAT stands for Salt Water Energy Accumulation and Transformation, has led to a new heat storage and cooling system for automotive applications. The system can best be discribed as a thermochemical heat storage system which stores low temperature heat for instance waste heat from car motors. At a later stage heat or cold can be produced by using the thermochemical heat pump function.The basic problems with comparable systems in the past were: Poor stability and side reactions of the materials used. Low power output per kg Low storage capacity Low efficiency Research conducted by a team of De Beijer RTB B.V. in cooperation with the Delft University of technology in the Netherlands and some industrial companies improved the system considerably.The possibility of using waste motor heat of motor vehicles for cooling and heating of the passengers' compartment is being investigated in cooperation with a German automotive supplying company. A research project and a prototype for testing purposes have already been completed of which the results are promising.