Engine apparatus and method for operation

A system for energy conversion, the system comprising:

• a closed cycle engine containing a working fluid, the closed cycle engine comprising;
• a first chamber defining an expansion chamber;
• a second chamber defining a compression chamber each separated by a piston attached to a connection member of a piston assembly;
• a heater body in thermal communication with the first chamber;
• a cold side heat exchanger in thermal communication with the second chamber;
• a third chamber defined within the piston, wherein the third chamber is in selective flow communication with the first chamber, the second chamber, or both,
• wherein the piston comprises a folded cross-sectional member positioned within the third chamber,
• wherein the piston comprises a first monolithic piece and a second monolithic piece, the second monolithic piece comprising the folded cross-sectional member, and
• wherein the first monolithic piece is positioned proximate to the first chamber, and wherein the first monolithic piece separates the first chamber and the third chamber within the piston.