In this study, solar field sizing and overall performance of different vapor cycles are examined. The
systems considered are parabolic trough solar collectors integrated with either a binary vapor cycle or a
steam Rankine cycle (SRC). The binary vapor cycle consists of an SRC as a topping cycle and an organic
Rankine cycle as a bottoming cycle. Seven refrigerants are examined for the bottoming cycle: R600,
R600a, R134a, R152a, R290, R407c, and ammonia. This study reveals that significant reduction in the
solar field size is gained due to the performance improvement when the binary vapor cycle is considered
as compared to a steam Rankine cycle with atmospheric condensing pressure; however, SRC with vacuum
pressure has the best performance and smallest solar field size. It further reveals that the R134a
binary vapor cycle has the best performance among the binary vapor cycles considered and, thus, requires
the smallest solar field size while the R600a binary vapor cycle has the lowest performance.
Finally, optimization shows that lowering the mass flow rate of the heat transfer fluid (HTF) per each
solar collector row, within the range considered, results in a reduction of the required number of solar
collector rows and, thus, in savings.