Methods of operating a volumetric expander and a closed cycle plant including a volumetric expander

A method of operating a closed circuit plant comprising:

• a volumetric expander which comprises:
• a casing having a general inlet configured to enable introduction of a working fluid inside the casing and a general outlet configured to enable expulsion of the working fluid from said casing,
• a piston inside the casing defining a variable volume expansion chamber,
• a main shaft kinematically connected to the piston,
• a valve configured to selectively open and close an inlet and an outlet of said expansion chamber to enable:
• an introduction condition, in which the working fluid is introduced into the expansion chamber,
• an expansion condition, in which the working fluid expands in the expansion chamber, and
• a discharge condition, in which the working fluid is discharged from said expansion chamber,
• wherein the casing internally defines a discharge chamber in fluid communication with the general outlet, the discharge chamber being further configured to be put in fluid communication with the outlet of the expansion chamber during the discharge condition,
• wherein the casing comprises an auxiliary inlet in communication with the discharge chamber, the auxiliary input also in fluid communication with the general outlet through the discharge chamber;
• and an electric energy generator connected to the main shaft of the volumetric expander and configured to generate electric energy upon rotation of the main shaft;
• said method comprising:
• introducing the working fluid into the discharge chamber of the casing through the auxiliary inlet for pre-heating at least one of the casing and the valve,
• then introducing the working fluid through the general inlet and starting operation of the volumetric expander.