Process and system for recovery of energy from geothermal brines and other water containing or hot water sources, which comprises direct contact heat exchange between the brine or hot water, and a working fluid, e.g. n-butane, in a heat transfer column, the heat transfer column being operated in the subcritical pressure region of the working fluid, close to or approaching the apex of the saturated vapor curve for such working fluid on the Mollier enthalpy-entropy diagram for such fluid. The heated working fluid exiting the top of the heat transfer column is expanded through an expander to produce work. The discharge from the expander is cooled to condense working fluid which is separated in an accumulator, from condensed water vapor present in the working fluid, and the condensed working fluid is pressurized and fed back to the heat transfer column.Cooled brine or water from the bottom of the heat transfer column and water from the accumulator are fed to a flashing device such as a flash drum operated at a pressure less than that in the accumulator, and the working fluid flashed off is compressed and returned to the cooler at the expander discharge, for condensation and recovery. Uncondensible gases plus working fluid losses are vented from the accumulator. Cold brine or water is discharged from the flashing means such as the flash drum, and any scale formed in the heat transfer column is discharged from the bottom thereof.