Among all the available solutions to the current high energy demand and consequent economic and environmental problems, solar energy, without any doubt, is one of the most promising and widespread solutions. However, conventional solar systems face some intractable challenges affecting their technical performance and economic feasibility. To overcome these challenges, increasing attention has been drawn towards the utilization of heat pipes, as an efficient heat transfer technology, in conventional solar systems. To the authors’ knowledge, despite many valuable studies on heat pipe solar collectors (mainly during the last decade), a comprehensive review which surveys and summarizes those studies and identifies the research gaps in this field has not been published to date. This review paper provides an overview of the recent studies on heat pipe solar collectors (HPSCs), their utilization in different domestic, industrial, and innovative applications, challenges, and future research potentials. The concept and principles of HPSCs are first introduced and a review of the previous studies to improve both energy efficiency and cost effectiveness of these collectors is presented. Moreover, a concise section is dedicated to mathematical modeling to demonstrate suitable methods for simulating the performance of HPSCs. Also, the latest applications of HPSCs in water heating, desalination, space heating, and electricity generation systems are reviewed, and finally, some recommendations for future research directions, regarding both development and new applications, are made.

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A review of latest developments, progress, and applications of heat pipe solar collectors

Evacuated tube solar collector with multifunctional absorber layers

Coupled optical-thermal modeling, design and experimental testing of a novel medium-temperature solar thermal collector with pentagon absorber

Theoretical modelling approaches of heat pipe solar collectors in solar systems: A comprehensive review

Performance evaluation of the senergy polycarbonate and asphalt carbon nanotube solar water heating collectors for building integration

Dual use of carbon nanotube selective coatings in evacuated tube solar collectors

Carbon nanotube, oriented free standing sheets can be laminated on any surface asВ selective solar absorbers while simultaneously dry spun in a highly controlled processВ from vertically oriented forests grown by CVD. We have found that properties of aВ CNT forest strongly correlate with the optical transparency and reflectivity of CNTВ sheets required for solar selective coatings and can be properly tuned for optimalВ coatings for solar collectors. We study absorptive and emissive properties of CNTВ sheets that are laminated by a simple automated and controlled process, developedВ for coating of cylindrical glass tubes for evacuated solar collectors (ETC). TheВ advantages of Joule heating of CNT coatings are demonstrated and test resultsВ described, showing a unique property of fast heating as compared to slow heating inВ conventional solar water heaters.

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William Holmes

Papers

Dual use of carbon nanotube selective coatings in evacuated tube solar collectors

Carbon Nanotube Dry Spinnable Sheets for Solar Selective Coatings by Lamination