In which stage of the calvin cycle does the plant cell produce energy for storage?

I believe the answer is the Regeneration stage.
A this stage of the Calvin Cycle, only one of the G3P molecules leaves the cycle and is sent to the cytoplasm to contribute to the formation of other compounds needed by the plant. Because the G3P exported from the chloroplast has three carbon atoms, it takes three "turns" of the Calvin cycle to fix enough net carbon to export one G3P. Each turn makes two G3Ps, therefore three turns make six G3Ps. 

For anyone who believes that the answer is "regeneration," that's incorrect.

They both determine the exact age of rocks.