Device for energy extraction from fluid (air or water) is investigated. The device consists of a one central rotor with energy generator and several plane blades. All blades are connected to the central rotor with gear system which allows automatically change the orientation of their working surfaces to the direction of the incoming fluid flow. It is considered task that axis of the rotor and blades are perpendicular to fluid flow. System has one degree of freedom as rotation angle of central rotor. Theoretical analysis of the one blade interaction with the fluid flow is given. Calculation of system with one blade is done with Math CAD.