Evaluation of an Integrated PTSC/Thermal Energy Storage System Using Nano-Fluid Particles

Abstract

Daily increase in the use of electricity and fossil fuels in the world raises the need for a renewable source of energy to accommodate the needs and power requirements for different sectors. Concentrated Solar Power (CSP) is the leading technology in harvesting the solar radiation, which paves the way for a sustainable energy production that can replace conventional power generation methods. Parabolic Trough Solar Collectors (PTSC) are the most efficient and advanced type of CSPs. However, the efficiency and heat loss while storing are two major drawbacks in using PTSC. Adding nanoparticles to a conventional heating fluid will increase the thermal conductivity of that fluid, which will enhance the performance of the PTSC, and improve the overall performance of a PTSC/Thermal Energy Storage (TES) integrated system. In this thesis, the effect of using nanofluids as a heating fluid in an integrated PTSC/TES System is evaluated. Two metallic nanoparticles: Copper (Cu) and Alumina (Al₂O₃), and one non-metallic: Single Walled Carbon Nanotubes (SWCNT) are dispersed into Therminol VP-1 and Syltherm 800. The thermophysical properties of the resulting nanofluids are studied for different volume fractions, and their effect on the convective heat transfer coefficient is analyzed. Further, the improvement in performance of the PTSC is investigated, and the effect of that improvement on the performance and the cost of different configurations of an integrated PTSC/TES system for different modes of operation (no storage, 7.5 hours and 10 hours) are examined. The results show that adding nanoparticles to a base fluid will increase the thermal conductivity as well as the overall heat transfer inside the absorber tube of the PTSC. It was seen that SWCNT-based nanofluids showed the highest improvement of 6-8% in the PTSC efficiency. The effect of the nanofluids on the performance and cost of the PTSC/TES system depends on the mode of operation, where different nanofluids showed different enhancements on the annual energy and net saving of the PTSC/TES system. It was concluded that the 2ndmode of operation with a storage period of 7.5 hours is the most efficient and cost effective mode for the PTSC/TES system to operate on.