Performance improvement of dry cooled advanced concentrating solar power plants using daytime radiative cooling Mehdi Zeyghami ⇑ , Fardin Khalili Department of Mechanical Engineering, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620, USA article info Article history: Received 14 May 2015 Accepted 6 September 2015 Keywords: Concentrating solar power Dry cooling Radiative cooling Central receiver tower Supercritical carbon dioxide cycle abstract In this study, utilization of daytime radiative cooling to enhance the performance of air-cooled concen- trating solar thermal power plants is investigated. Water scarcity and environmental concerns are the driving forces for solar thermal power plants to use dry cooling systems. In order to overcome the energy conversion efficiency penalties associated with using air cooled technologies various supplemental cool- ing techniques have been proposed. Recent advancements in manufacturing structures with selective radiative properties have made the daytime radiative cooling to the cold outer space practical. In this work, the efficiency improvement of the air-cooled advanced supercritical carbon dioxide power cycles coupled with a radiative cooler is explored. It is shown that for the simple supercritical carbon dioxide cycle operating at hot source temperature equal 550 °C by employing 14.02 m 2 /kW e radiative cooler, it is possible to overcome the efficiency losses due to air cooling and the net output of the cycle improves by 5.0%. At hot source temperature equal 800 °C, the required radiative cooler area is 4.38 m 2 /kW e and respective performance improvement is equal 3.1%. For the recompression supercritical carbon dioxide cycle operating at hot source temperature equal 550 °C by employing 18.26 m 2 /kW e radiative cooler, it is possible to overcome the efficiency losses due to air cooling and the net output of the cycle improves by 7.5%. At hot source temperature equal 800 °C, the required radiative cooler area is 10.46 m 2 /kW e and respective performance improvement is equal 4.9%. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Of all renewable power generation technologies available today, Concentrating Solar Power (CSP) stations are moving to the fore- front and might become the technology of choice to supply the future electricity demands of the world. It has been estimated that CSP could satisfy 11% of global electricity demand by the year 2050 [1]. CSP plants equipped with thermal energy storage can produce dispatchable power with high capacity factors even with a cloudy sky or after sunset, which makes them suitable candidates for base load power supply [2]. Research and development programs to improve the performance of CSP plants are undergoing by numer- ous research entities around the world. As an example, in 2011, ‘SunShot Concentrating Solar Power R&D’ initiated by US Department of Energy [3] to develop more efficient and reliable technologies with lower cost than existing CSP plants. Central Receiver Systems (CRS) are currently attracting a lot of attention amongst researchers. The high achievable operating temperature (up to 800 °C) in a CRS would result in higher thermal efficiency and makes more efficient thermal storage possible [4]. Dostal et al. [5] showed that the super-critical carbon dioxide (S-CO 2 ) cycle can reach higher thermal efficiency than super-heated steam cycle at temperatures above 470 °C, making it suitable for high-temperature heat sources available by CRS plants. In order to meet the targets proposed by ‘SunShot’, several configurations of S-CO 2 power cycle have been investigated as candidates for power cycle in advanced CRS plants by several researchers. Turchi et al. [6] showed, thermal efficiencies higher than 50% for recom- pression and partial cooling S-CO 2 cycle configurations under dry cooled conditions. Temperature of the heat sink is an important factor for high efficiency thermal power cycles. Lower the heat rejection temperature, higher the energy conversion efficiency. Besarati and Goswami [7] investigated the performance improve- ment of the S-CO 2 cycles by adding an organic Rankine cycle as a bottoming cycle to the system. Neises and Turchi [8] performed a detailed study on the integration of S-SO 2 cycles with direct solar receiver and sensible heat storage into CSP plants. Furthermore, Sarkar [9] conducted the second law analysis of recompression S-CO 2 cycle for heat sources up to 750 °C. He showed the effect http://dx.doi.org/10.1016/j.enconman.2015.09.016 0196-8904/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: mzeyghami@mail.usf.edu (M. Zeyghami). Energy Conversion and Management 106 (2015) 10–20 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman