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25 pages, 26783 KiB

Open AccessArticle

Performance Enhancement of a Solar Air Heater Equipped with a Tree-like Fractal Cylindrical Pin for Drying Applications: Tests Under Real Climatic Conditions

by Chotiwut Prasopsuk, Kittiwoot Sutthivirode and Tongchana Thongtip

Energies 2025, 18(9), 2230; https://doi.org/10.3390/en18092230 - 27 Apr 2025

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Abstract

This paper reports the improved thermal and drying performance of a solar air heater powered by real solar irradiance and equipped with a tree-like fractal-based cylindrical pin (SAH-TFCP) as a turbulator for drying applications. The main purpose of this work is to demonstrate [...] Read more.

This paper reports the improved thermal and drying performance of a solar air heater powered by real solar irradiance and equipped with a tree-like fractal-based cylindrical pin (SAH-TFCP) as a turbulator for drying applications. The main purpose of this work is to demonstrate the SAH-TFCP’s improvement potential based on its thermal and drying performance as compared with a conventional solar air heater based on a flat-plate absorber (SAH-FP). The test was implemented based on solar time from 8:30 to 17:30 under Thailand’s climatic conditions at a latitude angle of 14° and a longitude angle of 100°. Turmeric slices were used to evaluate the SAH’s drying performance. The thermal efficiency, moisture content wet basis (MC_wb), drying rate (DR), and drying efficiency were measured as parameters of interest to assess the improvement potential of the SAH-TFCP over the SAH-FP. The results indicate that the SAH-TFCP provides better thermal and drying performance than the SAH-FP. A higher flow rate yields a higher thermal efficiency and a greater improvement potential. The improvement potential is around 44–85%. The drying efficiency of the SAH-TFCP is always higher than that of the SAH-FP and has an improvement potential of 32–44%, depending on the airflow rate. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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19 pages, 2479 KiB

Open AccessArticle

Optimization Research on a Novel Community Integrated Energy System Based on Solar Energy Utilization and Energy Storage

by Xunwen Zhao, Hailin Mu, Nan Li, Xue Kong and Xunpeng Shi

Energies 2025, 18(5), 1151; https://doi.org/10.3390/en18051151 - 26 Feb 2025

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Abstract

Integrated energy systems (IESs) are essential for enabling the energy transition in communities and reducing CO₂ emissions. This paper proposes a novel IES that combines photovoltaic (PV) and solar thermal energy with coordinated electrical and thermal energy storage to meet the energy [...] Read more.

Integrated energy systems (IESs) are essential for enabling the energy transition in communities and reducing CO₂ emissions. This paper proposes a novel IES that combines photovoltaic (PV) and solar thermal energy with coordinated electrical and thermal energy storage to meet the energy demands of residential communities. The system also incorporates hydrogen production for fuel cell vehicles. A dual-objective optimization model was developed, minimizing both economic costs and CO₂ emissions. The system’s performance was evaluated using data from a case study in Dalian, which showed that the IES successfully reduced the annual total cost and CO₂ emissions compared to conventional systems. The key findings showed that PV electrolysis for hydrogen production provides both economic and environmental advantages. The system’s integration of solar thermal energy offers higher economic efficiency, while PV energy supplies enhance coordination. Additionally, carbon trading prices effectively reduce emissions, but excessively high prices do not always lead to better emission outcomes. This study introduces a comprehensive, multi-energy approach for optimizing the energy supply, contributing novel insights to the field of sustainable energy systems. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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19 pages, 6664 KiB

Open AccessArticle

The Effect of Facade Orientation on the Electrical Performance of a BIPV System: A Case Study in João Pessoa, Brazil

by Michelli Mayara de Medeiros Gomes, Renan Douglas Lopes da Silva Cavalcante, Oswaldo Hideo Ando Junior, Claudio Del Pero, João Alves de Lima and Taynara Geysa Silva do Lago

Energies 2025, 18(4), 829; https://doi.org/10.3390/en18040829 - 11 Feb 2025

Viewed by 572

Abstract

Photovoltaic solar energy has emerged as a vital solution in energy transition, especially in buildings with building-integrated photovoltaic (BIPV) systems. This study evaluated a BIPV system in João Pessoa, Brazil, using PVsyst 7.4 software for simulations in 2023 and experimental tests in 2024 [...] Read more.

Photovoltaic solar energy has emerged as a vital solution in energy transition, especially in buildings with building-integrated photovoltaic (BIPV) systems. This study evaluated a BIPV system in João Pessoa, Brazil, using PVsyst 7.4 software for simulations in 2023 and experimental tests in 2024 to compare real and simulated energy values injected into the grid. The experiments were conducted in April, June, July, and August, covering seasonal variations. The east and west orientations showed the best performance, with annual production of 65.5 and 81.6 kWh, respectively, due to the balanced solar irradiance. Conversely, the north and south orientations generated less electricity, with 51.3 and 42.1 kWh, respectively, due to lower direct solar exposure. The average injected energy was 0.2445 to 0.2530 kWh/day in April, 0.2851 to 0.2470 kWh/day in June, 0.2816 to 0.2400 kWh/day in July, and 0.1556 to 0.1700 kWh/day in August. Performance ratios were 44.3% for the north, 44.4% for the south, 47.4% for the east, and 56.8% for the west, highlighting the impact of orientation. It is concluded that the east and west facades are more suitable for BIPV systems in João Pessoa, emphasizing the importance of local factors in optimizing urban energy efficiency. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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21 pages, 11094 KiB

Open AccessArticle

Non-Condensation Turbulence Models with Different Near-Wall Treatments and Solvers Comparative Research for Three-Dimensional Steam Ejectors

by Yiqiao Li, Hao Huang, Dingli Duan, Shengqiang Shen, Dan Zhou and Siyuan Liu

Energies 2024, 17(22), 5586; https://doi.org/10.3390/en17225586 - 8 Nov 2024

Cited by 1 | Viewed by 1020

Abstract

Steam ejectors are important energy-saving equipment for solar thermal energy storage; however, a numerical simulation research method has not been agreed upon. This study contributes to a comprehensive selection of turbulence models, near-wall treatments, geometrical modeling (2-D and 3-D), solvers, and models (condensation [...] Read more.

Steam ejectors are important energy-saving equipment for solar thermal energy storage; however, a numerical simulation research method has not been agreed upon. This study contributes to a comprehensive selection of turbulence models, near-wall treatments, geometrical modeling (2-D and 3-D), solvers, and models (condensation and ideal-gas) in the RANS equations approach for steam ejectors through validation with experiments globally and locally. The turbulence models studied are k-ε Standard, k-ε RNG, k-ε Realizable, k-ω Standard, k-ω SST, Transition SST, and linear Reynolds Stress. The near-wall treatments assessed are Standard Wall Functions, Non-equilibrium Wall Functions, and Enhanced Wall Treatment. The solvers compared are pressure-based and density-based solvers. The root causes of their distinctions in terms of simulation results, applicable conditions, convergence, and computational cost are explained and compared. The complex phenomena involving shock waves, choking, and vapor condensation captured by different models are discussed. The internal connections of their performance and flow phenomena are analyzed from the mechanism perspective. The originality of this study is that both condensation and 3-D asymmetric effects on the simulation results are considered. The results indicate that the k-ω SST non-equilibrium condensation model coupling the low-Re boundary conditions has the most accurate prediction results, best convergence, and fit for the widest range of working conditions. A 3-D asymmetric condensation model with a density-based solver is recommended for simulating steam ejectors accurately. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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38 pages, 7303 KiB

Open AccessArticle

Towards Sustainable Energy Solutions: Evaluating the Impact of Floating PV Systems in Reducing Water Evaporation and Enhancing Energy Production in Northern Cyprus

by Youssef Kassem, Hüseyin Gökçekuş and Rifat Gökçekuş

Energies 2024, 17(21), 5300; https://doi.org/10.3390/en17215300 - 25 Oct 2024

Viewed by 1266

Abstract

Floating photovoltaic systems (FPVSs) are gaining popularity, especially in countries with high population density and abundant solar energy resources. FPVSs provide a variety of advantages, particularly in situations where land is limited. Therefore, the main objective of the study is to evaluate the [...] Read more.

Floating photovoltaic systems (FPVSs) are gaining popularity, especially in countries with high population density and abundant solar energy resources. FPVSs provide a variety of advantages, particularly in situations where land is limited. Therefore, the main objective of the study is to evaluate the solar energy potential and investigate the techno-economic perspective of FPVSs at 15 water reservoirs in Northern Cyprus for the first time. Due to the solar radiation variations, solar power generation is uncertain; therefore, precise characterization is required to manage the grid effectively. In this paper, four distribution functions (Johnson SB, pert, Phased Bi-Weibull, and Kumaraswamy) are newly introduced to analyze the characteristics of solar irradiation, expressed by global horizontal irradiation (GHI), at the selected sites. These distribution functions are compared with common distribution functions to assess their suitability. The results demonstrated that the proposed distribution functions, with the exception of Phased Bi-Weibull, outperform the common distribution regarding fitting GHI distribution. Moreover, this work aims to evaluate the effects of floating photovoltaic systems on water evaporation rates at 15 reservoirs. To this aim, five methods were used to estimate the rate of water evaporation based on weather data. Different scenarios of covering the reservoir’s surface with an FPVS were studied and discussed. The findings showed that annual savings at 100% coverage can reach 6.21

\times

10⁵ m³ compared to 0 m³ without PV panels. Finally, technical and economic assessment of FPVSs with various scales, floating assemblies, and PV technologies was conducted to determine the optimal system. The results revealed that a floating structure (North orientation-tilt 6°) and bifacial panels produced the maximum performance for the proposed FPVSs at the selected sites. Consequently, it is observed that the percentage of reduction in electricity production from fossil fuel can be varied from 10.19% to 47.21% at 75% FPV occupancy. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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19 pages, 9356 KiB

Open AccessArticle

Scaling Law of Flow and Heat Transfer Characteristics in Turbulent Radiative Rayleigh-Bénard Convection of Optically Thick Media

by Jiajun Song, Panxin Li, Lu Chen, Yuhang Zhao, Fengshi Tian and Benwen Li

Energies 2024, 17(19), 5009; https://doi.org/10.3390/en17195009 - 8 Oct 2024

Viewed by 1229

Abstract

Radiative natural convection is of vital importance in the process of energy storage, power generation, and thermal storage technology. As the attenuation coefficients of many heat transfer media in these fields are high enough to be considered as optically thick media, like nanofluids [...] Read more.

Radiative natural convection is of vital importance in the process of energy storage, power generation, and thermal storage technology. As the attenuation coefficients of many heat transfer media in these fields are high enough to be considered as optically thick media, like nanofluids or molten salts in concentrated solar power or phase change thermal storage, Rosseland approximation is commonly used. In this paper, we delve into the impact of thermal radiation on the Rayleigh-Bénard (RB) convection. Theoretical analysis has been conducted by modifying the Grossmann-Lohse (GL) model. Based on turbulent dissipation theory, the corresponding scaling laws in four main regimes are proposed. Direct numerical simulation (DNS) was also performed, revealing that radiation exerts a notable influence on both flow and heat transfer, particularly on the formation of large-scale circulation. By comparing with DNS results, it is found that due to the presence of radiation, the modified Nu scaling law in small Pr range of the GL model is more suitable for predicting the transport characteristics of optical thick media with large Pr. The maximum deviation between the results of DNS and prediction model is about 10%, suggesting the summarized scaling law can effectively predict the Nu of radiative RB convection. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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18 pages, 25427 KiB

Open AccessFeature PaperArticle

Two-Phase Lattice Boltzmann Study on Heat Transfer and Flow Characteristics of Nanofluids in Solar Cell Cooling

by Hui Liu, Minle Bao, Luyuan Gong, Shengqiang Shen and Yali Guo

Energies 2024, 17(17), 4265; https://doi.org/10.3390/en17174265 - 26 Aug 2024

Cited by 1 | Viewed by 834

Abstract

During solar cell operation, most light energy converts to heat, raising the battery temperature and reducing photoelectric conversion efficiency. Thus, lowering the temperature of solar cells is essential. Nanofluids, with their superior heat transfer capabilities, present a potential solution to this issue. This [...] Read more.

During solar cell operation, most light energy converts to heat, raising the battery temperature and reducing photoelectric conversion efficiency. Thus, lowering the temperature of solar cells is essential. Nanofluids, with their superior heat transfer capabilities, present a potential solution to this issue. This study investigates the mechanism of enhanced heat transfer by nanofluids in two-dimensional rectangular microchannels using the two-phase lattice Boltzmann method. The results indicate a 3.53% to 22.40% increase in nanofluid heat transfer, with 0.67% to 6.24% attributed to nanoparticle–fluid interactions. As volume fraction (φ) increases and particle radius (R) decreases, the heat transfer capability of the nanofluid improves, while the frictional resistance is almost unaffected. Therefore, the performance evaluation criterion (PEC) of the nanofluid increases, reaching a maximum value of 1.225 at φ = 3% and R = 10 nm. This paper quantitatively analyzes the interaction forces and thermal physical parameters of nanofluids, providing insights into their heat transfer mechanisms. Additionally, the economic feasibility of nanofluids is examined, facilitating their practical application, particularly in solar cell cooling. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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Review

Jump to: Research

33 pages, 2848 KiB

Open AccessReview

A Review on Phase-Change Materials (PCMs) in Solar-Powered Refrigeration Systems

by Yali Guo, Chufan Liang, Hui Liu, Luyuan Gong, Minle Bao and Shengqiang Shen

Energies 2025, 18(6), 1547; https://doi.org/10.3390/en18061547 - 20 Mar 2025

Cited by 1 | Viewed by 498

Abstract

Over the past few years, the combination of solar power with refrigeration technology has matured, providing a promising solution for sustainable cooling. However, a key challenge remains, namely the inherent intermittency of solar energy. Due to its uneven temporal distribution, it is difficult [...] Read more.

Over the past few years, the combination of solar power with refrigeration technology has matured, providing a promising solution for sustainable cooling. However, a key challenge remains, namely the inherent intermittency of solar energy. Due to its uneven temporal distribution, it is difficult to ensure continuous 24 h operation when relying solely on solar energy. To address this issue, thermal energy storage technology has emerged as a viable solution. This paper presents a comprehensive systematic review of phase-change material (PCM) applications in solar refrigeration systems. It systematically categorizes solar energy conversion methodologies and refrigeration system configurations while elucidating the fundamental operational principles of each solar refrigeration system. A detailed examination of system components is provided, encompassing photovoltaic panels, condensers, evaporators, solar collectors, absorbers, and generators. The analysis further investigates PCM integration strategies with these components, evaluating integration effectiveness and criteria for PCM selection. The critical physical parameters of PCMs are comparatively analyzed, including phase transition temperature, latent heat capacity, specific heat, density, and thermal conductivity. Through conducting a critical analysis of existing studies, this review comprehensively evaluates current research progress within PCM integration techniques, methodological classification frameworks, performance enhancement approaches, and system-level implementation within solar refrigeration systems. The investigation concludes by presenting strategic recommendations for future research priorities based on a comprehensive systematic evaluation of technological challenges and knowledge gaps within the domain. Full article

(This article belongs to the Special Issue Advanced Technology for Solar Thermal Cooling, Heating, and Energy Storage)

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