Strategies to improve the thermal performance of heat pipe solar collectors in solar systems: A review

Abstract

Invention of evacuated tube heat pipe solar collectors (HPSCs) was a huge step forward towards resolving the challenges of conventional solar systems due to their unique features and advantages. This has led to their utilization in a wide range of solar applications surpassing other conventional collectors. However, relatively low thermal efficiency of heat pipe solar (HPS) systems is still the major challenge of solar industry evidenced by numerous studies conducted mainly during the last decade to improve their efficiency. To date, several review papers have been published summarizing studies relevant to utilization of HPSCs in various thermal applications. However, to the authors' knowledge, a comprehensive review which surveys and provides an overview of the studies undertaken to improve the thermal performance of HPS systems (mainly during the last decade) by implementing different strategies has not been published to date. This review paper summarizes all the proposed strategies to improve the thermal efficiency of different industrial, domestic, and innovative HPS systems. First, the concept, structure, and operational principles of HPSCs are introduced concisely. Then, novel structures and designs of HPSCs aiming to increase the thermal efficiency of the collector as the most important component of the solar system is reviewed. This is followed by a comprehensive review of various methods to store solar energy more efficiently, increase solar system's operation time, increase overall efficiency by turning the solar system into a multipurpose system, enhance heat transmission in the solar system, and implement new solar loop and heat pipe working fluids with better heat transfer characteristics. Finally, research gaps in this field are identified and some future research trends and directions are recommended.

Design and Analysis of the Domestic Micro-Cogeneration Potential for an ORC System Adapted to a Solar Domestic Hot Water System

“…The working fluid is one of the most important factors to take into consideration for the performance of solar collectors [ 37 ], because it carries the heat absorbed by the solar collector to the load or to the hot water tank. Therefore, it is important to consider the thermal properties such as thermal conductivity.…”

“…This is because the higher the heat transfer to the fluid, the higher the collector efficiency [ 39 ]. Some studies have used acetone as the working fluid in heat pipe collectors, achieving a better performance than with other working fluids [ 37 , 40 , 41 , 42 , 43 ]. These results confirm that acetone is an adequate working fluid to operate with phase changes in solar collectors.…”

Comprehensive review of the recent advances in PV/T system with loop-pipe configuration and nanofluid

“…In terms of current solar energy technologies, photovoltaic/thermal (PV/T) system is the most efficient and widely deployed owing to its stability, non-polluting, security and good visibility features [ 6 , 7 ]. To be more specific, the PV technology and solar thermal could be integrated together to form a single module and produce electricity and heat simultaneously based on the excitation of electrons in the semiconducting material [ [8] , [9] , [10] ]. There are various configurations for the PV/T pipe-loop.…”

Performance Investigation of a Solar Thermal Collector Based on Nanostructured Energy Materials

“…Solar energy is collected through flat-surface-based solar plates, converting this collected energy into heat and then delivering it to working fluid (Amjad et al, 2018a;Dehaj and Mohiabadi, 2019). However, the major drawback of this conventional surface base flat type is that, as the temperature of the flat plate increases, the radiant loss of heat occurs (Kılkış, 2000;Sint et al, 2017;Shafieian et al, 2019).…”