During off-peak operation of a power plant operating on a thermodynamic cycle wherein heat is rejected to an ambient fluid, heat is removed from a cold temperature storage medium. The cold temperature storage medium is stored until the power plant is experiencing a peak period. During the peak period, the stored cold temperature storage medium is used to absorb heat from the ambient fluid prior to heat rejection from the thermodynamic cycle to the ambient fluid, to improve performance of the thermodynamic cycle. In another aspect, the stored cold temperature storage medium is mixed with the ambient fluid prior to heat rejection from the thermodynamic cycle to the ambient fluid. Corresponding systems, apparatuses, retrofit methods, design and control techniques are also disclosed.