valve 24 to the extent necessary to hold backpressure within conpartment 12 the preferred pressure in compartment 12 for example is in the order of 150 psi and in any event a pressure of sufficient magnitude to exceed the bubble point pressure of the water in compartment 12 the frasch mine water enters the coupling heat exchanger 11 at a temperature of for example 190 u00b0 f and exits at a temperature of for example 330 u00b0 f the rate of flow of the frasch mine water through compartment 12 is regulated with due regard for the residence time required to absorb the heat necessary to raise the temperature to the desired level preferably before the frasch mine water reaches the coupling heat exchanger 11 it has been circulated through an economizer not shown that raises the temperature of the water from ambient to approximately 190 u00b0 f the economizer which in itself is a heat exchanger is located preferably in the exit gas stream of the products of combustion from the steam electric generating station wherein a portion of the sensible heat is transferred to the circulating frasch mine water before the products of combustion are vented to the atmosphere as an alternate the frasch mine water may be directed to the coupling heat exchanger 11 at ambient temperature preferably the steam injected into compartment 13 is distributed at a variety of locations within the compartment and at a variety of pressures within the range of pressures between the maximum inlet pressure of the steam and the.