Parabolic trough collector (PTC) is the most mature concentrating solar thermal technology. Limited by the cosine effect, annual thermal efficiency of FTC is only 50%. To show the limitations of performance of PTC and find corresponding solutions, an irreversibility analysis of FTC is experimentally conducted. Global exergy destruction is divided into exergy destructions in concentrator and receiver according to process analysis. Experimental results shows that the exergy destruction in concentrator accounts for the largest share. It indicates the process that sunlight being concentrated onto receiver is the key limitation of the performance of FTC. Experiments of the PTC with rotatable axis tracking show that rotatable axis tracking could decrease the exergy destruction in concentrator obviously. The annual exergy efficiency would be expected to be improved by 3% points according to the experimental results. This indicates that rotatable axis tracking is a practical method to improve the performance of PTCs. The influences of azimuth angle of FTC and heat transfer fluid temperature on exergy destruction are also analysed based on experimental data. In this study, the key limitation of the performance of the FTC is revealed and practical methods to decrease the exergy destruction of the FTC are provided. (C) 2018 Published by Elsevier Ltd.