Phase change material container device for storing an amount of a storage material consisting of a phase change material (PCM) for acting as a heat collector element, consisting of a packaging capsule which comprises an enveloping shell that is constituted by a rigid housing having an outer surface and enclosing a fillable inner space , for storing said phase change material (PCM) therein, wherein the outer surface of said housing is provided with a heat exchanger device , wherein said capsule has a toroidal ring shape with a longitudinal axis (l), said packaging capsule is filled with said phase-change material (PCM) forming a filling that is encapsulated therein and made of a different material than said housing , both chemically and physically distinct from said PCM material stored inside said capsule characterized in that said heat exchanger device consists of a set of grooves arranged in said outer surface of said housing , in that said set of grooves comprises a first subset of grooves each of which is arranged in closed loop as single convolution extending transversely around said longitudinal axis (l) and continuously over the whole cross-sectional perimeter of said toroidal housing , in a radial plane passing through the geometrical center of said capsule , wherein said capsule has a tubular profile with a circular cross section, on which the first grooves extend as successive circles orthogonally on said longitudinal axis (l), esp. spaced equidistantly, and in that said set of grooves comprises an additional subset of grooves consisting of partial grooves , which are each arranged in open loop as a non-convolutional, limited groove between successive convolutional grooves , in an alternating arrangement, extending equidistantly at the outer perimeter of the capsule , orthogonally on said longitudinal axis (l), over a circular fraction. said capsule has a toroidal ring shape with a longitudinal axis (l), said packaging capsule is filled with said phase-change material (PCM) forming a filling that is encapsulated therein and made of a different material than said housing , both chemically and physically distinct from said PCM material stored inside said capsule characterized in that said heat exchanger device consists of a set of grooves arranged in said outer surface of said housing , in that said set of grooves comprises a first subset of grooves each of which is arranged in closed loop as single convolution extending transversely around said longitudinal axis (l) and continuously over the whole cross-sectional perimeter of said toroidal housing , in a radial plane passing through the geometrical center of said capsule , wherein said capsule has a tubular profile with a circular cross section, on which the first grooves extend as successive circles orthogonally on said longitudinal axis (l), esp. spaced equidistantly, and in that said set of grooves comprises an additional subset of grooves consisting of partial grooves , which are each arranged in open loop as a non-convolutional, limited groove between successive convolutional grooves , in an alternating arrangement, extending equidistantly at the outer perimeter of the capsule , orthogonally on said longitudinal axis (l), over a circular fraction. <EOS>