System for energy conversion, comprising: - a support structure which defines at least one guide channel; - at least a plurality of extensible elements switchable between a compressed configuration and a dilated configuration, and vice versa, and configured to move a volume of a fluid in which they can be immersed, the volume being equal to the predetermined volume difference between the dilated configuration and the compressed configuration of each extensible element in which said extensible elements contains a volume of air, said plurality of extensible elements being arranged into a pile of extensible elements interconnected between each other to allow the displacement of the volume of air from an extensible element to another, preferably water-tight and laying in said fluid at a predetermined depth, each extensible element being individually and reversibly bound to the support structure by means of locking devices, wherein said fluid is water; - a moving assembly of said plurality of extensible elements operably linked to said support structure, wherein said moving assembly is configured to switch said pile of extensible elements from said compressed configuration to said dilated configuration by a tensile force acting on at least one extensible element of said pile; wherein said extensible elements are configured to slide along said guide channel during a switching of said extensible elements from said compressed configuration to said dilated configuration, and vice versa; wherein, as a result of said switching of said extensible elements from the compressed configuration to the dilated configuration, said system determines a conversion of potential energy to a useful energy, whose value is proportional to a total volume of said fluid displaced by said extensible elements in the dilated configuration and at a depth reached by the extensible element of said pile with respect to a free surface of said fluid. - a support structure which defines at least one guide channel; - at least a plurality of extensible elements switchable between a compressed configuration and a dilated configuration, and vice versa, and configured to move a volume of a fluid in which they can be immersed, the volume being equal to the predetermined volume difference between the dilated configuration and the compressed configuration of each extensible element in which said extensible elements contains a volume of air, said plurality of extensible elements being arranged into a pile of extensible elements interconnected between each other to allow the displacement of the volume of air from an extensible element to another, preferably water-tight and laying in said fluid at a predetermined depth, each extensible element being individually and reversibly bound to the support structure by means of locking devices, wherein said fluid is water; - a moving assembly of said plurality of extensible elements operably linked to said support structure, wherein said moving assembly is configured to switch said pile of extensible elements from said compressed configuration to said dilated configuration by a tensile force acting on at least one extensible element of said pile; wherein said extensible elements are configured to slide along said guide channel during a switching of said extensible elements from said compressed configuration to said dilated configuration, and vice versa; wherein, as a result of said switching of said extensible elements from the compressed configuration to the dilated configuration, said system determines a conversion of potential energy to a useful energy, whose value is proportional to a total volume of said fluid displaced by said extensible elements in the dilated configuration and at a depth reached by the extensible element of said pile with respect to a free surface of said fluid.