Converting and storing energy in the borehole

During a drilling operation energy can be saved, to be converted and generated. An example method includes receiving power from a fluid flow of drilling fluid (115) in a wellbore (105). The received fluid energy can be stored as mechanical energy in an energy storage device (205) in the wellbore (105). In addition, electric power from the mechanical energy can be generated by using a generator which is mechanically or magnetically coupled to the energy storage device.