Calculation of the specific and volumetric enthalpies of Ge-Si alloys

A procedure is developed for the calculation of specific and volumetric enthalpies of Ge-Si alloys as an initial step in the evaluation of these materials for heat storage in solar dynamic power systems. The calculation is based on the thermodynamics of non-ideal solutions and the reported regular nature of liquid and solid Ge-Si solutions. With only minor modifications, all of the other thermodynamic properties of this alloy system may additionally be evaluated. Use of Ge-Si alloys for heat storage purposes in solar receivers entails both negative and positive aspects. The negative aspects relate largely to the non-congruent nature of the phase change process which precludes isothermal heat delivery. However, on the positive side are high thermal conductance, low volume change on melting, and the availability of a range of heat delivery temperatures by modification of only the alloy composition.