Energy and exergy analysis and optimization of low-flux direct absorption solar collectors (DASCs): Balancing power- and temperature-gain

Omar Z. Sharaf, Ashraf N. Al-Khateeb, Dimitrios C. Kyritsis, Eiyad Abu-Nada*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)

Abstract

The objective of this work is to determine the balance between power gain and temperature gain in nanofluid-based direct absorption solar collectors (DASCs). The radiative transfer and energy conservation equations were numerically coupled and solved. It was observed that, despite the low exergy efficiency in low-flux DASCs, the design point at which exergy efficiency is maximized provides a compromise between power- and temperature-gain. The trade-off between power gain and temperature gain was investigated where it was observed that a collector efficiency of up to 55% can be obtained without sacrificing temperature gain. Beyond that, the trade-off between power- and temperature-gain dominates. Moreover, by expanding the parameter space, some seemingly contradictory results reported in the literature have been examined and justified regarding the effects of collector length on energy efficiency and flow velocity on exergy efficiency. Finally, the effect of nanofluid thermal conductivity on collector performance was found to be a function of the dominant solar radiation absorption mechanism. Comparing different base fluids, it was found that for water the energy efficiency was less sensitive to changes in nanofluid thermal conductivity when compared to oil.

Original languageEnglish
Pages (from-to)861-872
Number of pages12
JournalRenewable Energy
Volume133
DOIs
Publication statusPublished - Apr 2019

Keywords

  • DASC
  • Exergy
  • Nanofluid
  • Optimization
  • Solar thermal
  • Volumetric absorption

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment

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