The sensible heat of molten salt is also used for storing solar energy at a high temperature. It is termed molten-salt technology or molten-salt energy storage (MSES). Molten salts can be employed as a thermal energy storage method to retain thermal energy. Presently, this is a commercially used technology to store the heat collected by concentrated solar power (e.g., from a solar tower or solar trough). The heat can later be converted into superheated steam to power conventional steam turbines and generate electricity in bad weather or at night. It was demonstrated in the Solar Two project from 1995–1999. Estimates in 2006 predicted an annual efficiency of 99%, a reference to the energy retained by storing heat before turning it into electricity, versus converting heat directly into electricity. Various eutectic mixtures of different salts are used (e.g., sodium nitrate, potassium nitrate and calcium nitrate). Experience with such systems exists in non-solar applications in the chemical and metals industries as a heat-transport fluid.