Exhaust gas energy recovery system comprising - an exhaust line system for guiding exhaust gases from a combustion engine, - a motor/generator unit configured to be driven by exhaust energy to generate electrical energy, - a first line arm to the motor/generator unit for guiding exhaust gases to the motor/generator unit, - the motor/generator unit comprises a motor which is arranged to be driven by a pressure of passing exhaust gases, characterized in that - the motor is a rotary engine comprising - a housing defining an inner room, - at least two rotary pistons (20, 30) arranged in the inner room, - an inlet opening which is connected with the exhaust line system for introducing the exhaust gases into the inner room, and - an outlet opening for the exhaust gas defined at the inner room at a side opposite to the inlet opening, - each rotary piston (20, 30) comprises at least two sealing strips (25, 26, 35, 36) and at least two recesses (27, 28, 37, 38) at its outer circumference, the shapes of the recesses (27, 28, 37, 38) and the sealing strips (25, 26, 35, 36) are chosen for sealing engagement of the sealing strips (25, 26, 35, 36) of each one of the rotary pistons (20, 30) with the recesses (27, 28, 37, 38) of the respective other rotary piston (20, 30), - the sealing strips (25, 26, 35, 36) are sized to sealingly contact a housing inner surface in a radial direction, - the sealing strips (25, 26, 35, 36) comprise a deformable material such that the sealing strips (25, 26, 35, 36) can be pressed against the housing inner surface by incoming exhaust gases, - wherein each of the sealing strips (25, 26, 35, 36) comprises an exhaust gas contact surface facing inflowing exhaust gas when the respective rotary piston (20, 30) is at a rotation angle position at which said sealing strip (25, 26, 35, 36) contacts the housing inner surface, - each of the sealing strips (25, 26, 35, 36) has a rear side which is opposite the exhaust gas contact surface and which does not face inflowing exhaust gas when the respective rotary piston (20, 30) is at a rotation angle position in which said sealing strip (25, 26, 35, 36) contacts the housing inner surface, - the exhaust gas contact surface has a concave shape and/or the rear side has a convex shape. - an exhaust line system for guiding exhaust gases from a combustion engine, - a motor/generator unit configured to be driven by exhaust energy to generate electrical energy, - a first line arm to the motor/generator unit for guiding exhaust gases to the motor/generator unit, - the motor/generator unit comprises a motor which is arranged to be driven by a pressure of passing exhaust gases, characterized in that - the motor is a rotary engine comprising - a housing defining an inner room, - at least two rotary pistons (20, 30) arranged in the inner room, - an inlet opening which is connected with the exhaust line system for introducing the exhaust gases into the inner room, and - an outlet opening for the exhaust gas defined at the inner room at a side opposite to the inlet opening, - a housing defining an inner room, - at least two rotary pistons (20, 30) arranged in the inner room, - an inlet opening which is connected with the exhaust line system for introducing the exhaust gases into the inner room, and - an outlet opening for the exhaust gas defined at the inner room at a side opposite to the inlet opening, - each rotary piston (20, 30) comprises at least two sealing strips (25, 26, 35, 36) and at least two recesses (27, 28, 37, 38) at its outer circumference, the shapes of the recesses (27, 28, 37, 38) and the sealing strips (25, 26, 35, 36) are chosen for sealing engagement of the sealing strips (25, 26, 35, 36) of each one of the rotary pistons (20, 30) with the recesses (27, 28, 37, 38) of the respective other rotary piston (20, 30), - the sealing strips (25, 26, 35, 36) are sized to sealingly contact a housing inner surface in a radial direction, - the sealing strips (25, 26, 35, 36) comprise a deformable material such that the sealing strips (25, 26, 35, 36) can be pressed against the housing inner surface by incoming exhaust gases, - wherein each of the sealing strips (25, 26, 35, 36) comprises an exhaust gas contact surface facing inflowing exhaust gas when the respective rotary piston (20, 30) is at a rotation angle position at which said sealing strip (25, 26, 35, 36) contacts the housing inner surface, - each of the sealing strips (25, 26, 35, 36) has a rear side which is opposite the exhaust gas contact surface and which does not face inflowing exhaust gas when the respective rotary piston (20, 30) is at a rotation angle position in which said sealing strip (25, 26, 35, 36) contacts the housing inner surface, - the exhaust gas contact surface has a concave shape and/or the rear side has a convex shape.