NOVELTY - The method involves circulating a working medium (AM) in a waste heat recovery device (3) formed as a closed joule circuit (JK), where pressure level of the working medium is varied in the joule circuit. Process of supplying compressed air from a compressed air compressor (15) to the working medium in the joule circuit is controlled and/or regulated by a valve (16) i.e. three-way valve. A pressure sensor (21) and/or a temperature sensor (20) are arranged in the joule circuit and electrically connected to a control unit (22) that controls and/or regulates the valve based on sensor signals.    USE - Method for recovering energy from an exhaust stream of an internal combustion engine e.g. four-cylinder combustion engine, diesel engine and petrol engine, for a vehicle e.g. motor car and commercial vehicle.    ADVANTAGE - The method allows recovering increased amount of energy from the exhaust stream. The energy recovering device has a simple design and reduced weight, and requires a compact installation space, thus reducing the cost of the energy recovering device. The pressure level of the working medium is varied in the joule circuit, so that power output of the waste heat recovering device is controlled and/or regulated and adapted to power requirements of energy consumers in the vehicle and/or an amount of waste heat in the exhaust stream in a simple and cost-effective manner. The method allows saving fuel and achieving higher efficiency in the combustion engine.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a device for recovering energy from exhaust stream of internal combustion engine for a vehicle, comprising an air supply line.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic pneumatic circuit diagram of a device for recovering energy from an exhaust stream of an internal combustion engine, in which power output of a waste heat recovery device is controllable.    Working medium (AM)    Closed joule circuit (JK)    Waste heat recovery device (3)    Compressed air compressor (15)    Valve (16)    Temperature sensor (20)    Pressure sensor (21)    Control unit (22)