A solar-hybrid coal-fired power plant can use solar heat at <300 degrees C to replace steam extracted from a turbine to heat feed water. Through this process, the steam to be extracted can efficiently expand in the steam turbine to generate electricity. The advantages of a solar-hybrid coal-fired power plant in terms of design have been discussed by many researchers. However, solar-field performance under varied solar irradiation intensities has not yet been elucidated. In this study, a rotatable-axis tracking parabolic-trough collector was proposed by utilizing a partial rotatable device to drive the parabolic-trough collector. Energy losses (including cosine, end, and lateral shading losses) on four typical days were evaluated and compared with single-axis tracking method. The importance of improving the solar-field efficiency of rotatable-axis tracking system was discussed. Consequently, the solar-field area of a solar-hybrid coal-fired power plant would decreased by 4% if the rotatable-axis tracking system was utilized. (C) 2013 Elsevier Ltd. All rights reserved.