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Considering the daily increase of consumption and expense of nonrenewable energies such as natural gas and electricity, application of clean and renewable energies such as solar thermal energy nowadays has been highly taken into consideration. In this research, at first, simple steam Rankine cycle and two different configurations of combined steam and organic Rankine cycles with parabolic trough solar collector as heat source are simulated from energetic and exergetic point of view. First configuration was basic steam rankine cycle with parabolic trough solar collector (PTSC) as heat source, and other configurations of the combined cycle worked as follows: In the second configuration (combined cycle with intermediate heat exchanger), with the increase of steam condenser pressure, heat dissipation in condenser is used as heat source for bottoming organic Rankine cycle and in the third configuration (combined cycle without intermediate heat exchanger), reduced-temperature solar fluid moving output of steam rankine cycle acted as the organic Rankine cycle heat source. Simulation results in the basic input state show that third configuration has the maximum amount of work and irreversibility and second configuration has the minimum amount of work and irreversibility which in this case, increase in the steam cycle condenser pressure leads to the reduction of work of combined cycle with intermediate heat exchanger, even lower than the simple steam cycle. On the other hand, second configuration has the maximum solar energy and exergy efficiency among three configurations which is due to the reduction of collector area required in this configuration.

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