Feasibility Study of Heat Transfer Enhancement in Solar Photovoltaic-Thermal Systems Using FDM Generated Novel Curved Thermal Absorbers
Authors: Kamble Akash Dilip , Singh Ambrish , Singh Dipendra , Das Dudul , Kapil Sajan , Kalita Pankaj 
Published: February 2024

Abstract
Global warming and climate change are the major global concerns in the recent past as far as power generation is concerned. Renewable energy power generation is extensively promoted for the reduction of harmful gas emissions resulting in global warming. Among all the renewable energy technologies solar energy has greater global potential as the sun’s radiation is received uniformly everywhere. Solar thermal and solar photovoltaic (PV) are the two prominent routes of converting sunlight into usable forms wherein PV technology is more accessible for domestic and commercial deployment of solar energy. With higher intensity radiations, PV systems experience 0.45% efficiency loss per degree rise in solar cell temperature. To address this difficulty, solar photovoltaic-thermal (PV/T) collectors are proposed. PV/T is a promising technology where the simultaneous generation of both electrical and thermal energy generation is possible. The present study addresses the current challenges associated with the existing PV/T collectors or absorbers. The problem of heat transfer rate enhancement consistently persists because of low surface area exposure and less cooling uniformity of thermal absorbers. PVT thermal absorbers which have been designed by existing curves or patterns like Raster, Spiral or Rectangular spiral, etc., fail to deliver the optimum outcomes because of the raised issues.
The alternative novel type of curves has the potential to overcome these problems, categorized as space-filling curves and have a significant role in mathematical analysis. Spacefilling curves usually include the Hilbert curve, Peano curve, Grosper curve, Sierpinski curve, Z-curve, etc. with features like complex shapes or multiple turns and higher space-filling ratio, which will be favourable for designing a better PV/T thermal absorber. So, the proposed work will focus on the feasibility study of these space-filling curves as PV/T thermal absorbers for heat transfer enhancement, wherein investigation and identification of suitable novel space-filling curves as PV/T thermal absorbers have been performed for higher thermal and electrical efficiency.
The investigation formulated an analytical and computational analysis for finding the best suitable curve. The results of this analysis are compared to the existing curves as PV/T thermal absorbers to find a better alternative. The Hilbert curve is found to accommodate a larger tube length at the back of the PV panel, which facilitates a higher surface area and exhibits 9.676%, 35.237% and 14.576% increase in total surface area compared to Raster, Rectangular spiral and Peano curves respectively for heat transfer. Furthur, the time taken to extract the available heat to reach steady state condition from the specified PV panel surface by the Hilbert curve pattern is the comparatively minimum from other available curve patterns, showing its ability of maximum heat transfer rate. Thus, the Hilbert curve is better than available space-filling curves, exhibiting Higher surface area and heat transfer rate superiority. The fabrication of such novel curved metal absorbers becomes costly and needs sophisticated instruments like 3D printing technology due to its intrigued pattern, which has a maximum number of turns in its single pathway. Thus, Prototype models were prepared by Fused Deposition Modelling (FDM) using PLA as filler material, showing the practicability of these novel curves as PV/T thermal absorbers. Hence, to optimize efficiency, some novel types of space-filling curves, like the Hilbert curve, can be considered for full-scale PV/T thermal absorbers.