Solar Thermal Research Articles

Design and analysis of a machine learning-optimized multi-layered absorber for renewable energy applications

Harvesting solar energy into other useful energy sources are essential now a days, hance there are many systems available for that, such as solar absorbers, solar PV, etc. In this study, we have investigated four different solar absorber designs. Out of that four, the Hash-Shaped Solar Absorber (HSSA) structure is more effective for absorbing solar radiation and converting it into heat energy. With the broad response range this structure absorb more than 90 % of the radiation in observed range (100–5000 nm). The HSSA structure demonstrates absorption > 99 % at specific wavelength peaks, including 170 nm, 550 nm, 1790 nm, 2750 nm, 3090 nm, and 3700 nm within the solar spectrum. With this the HSSA structure is having more than 93 % absorption in the 3000–4000 nm range, whereas more than 97 % absorption is achieved in the visible region. Further, the HSSA structure is treated with the Machine Learning model as the parameter optimization. The greatest R2 value for this structure is 0.999592with a test size of 0.25, and the mean squared error is 1.79801 × 10−4. The ML reduces time (takes ¼ of the traditional time) and other simulation requirements. Additionally, the structure is polarization insensitive and up to 60° incident angle insensitive. Due tothese characteristics, the HSSA structures find usage in variousapplications, including solar thermal energy harvesting systems, plasmonic sensors, and detectors.

High-performance ultra-simple solar absorber with extremely high tolerance for fabrication errors

Broadband metamaterial perfect absorbers have drawn considerable attention from researchers for a broad range of applications in electromagnetic stealth, solar energy harvesting and other fields. However, it is extremely challenging to integrate the excellent characteristics of ultra-broadband, perfect absorption, polarization independent, and insensitivity to wide incidence angles into a structurally simple absorber. Herein, we present an ultra-wideband solar perfect absorber with an ultra-simple structure, which consists of a Si3N4-Ti-Si3N4-Ti four-layer structure. The optimized structure offers more than 92 % absorption in the bandwidth range of 450–2750 nm, and the average absorption is up to 97.3 %. Moreover, we elaborate the physical mechanism to achieve the broadband perfect absorption. For solar thermal systems, the absorber is capable of absorbing 95.7 % of the sunlight, its blackbody radiation absorption is as high as 98.0 % at 1900 K and it has a photothermal conversion efficiency of 90.2 % at 1000 K. Furthermore, the absorber displays the characteristics of being independent of polarization and insensitive to wide incidence angles. Additionally, the absorber possesses a very high tolerance for manufacturing errors. It is shown that the designed absorber is ultra-simple in structure and excellent in performance, and has excellent application prospects in fields including solar thermal conversion.

Research on Concentrated Solar Thermal Power Efficiency Based on Solar Elevation

Research on Concentrated Solar Thermal Power Efficiency Based on Solar Elevation

Improvement of Latent Heat Thermal Energy Storage Rate for Domestic Solar Water Heater Systems Using Anisotropic Layers of Metal Foam

Latent Heat Transfer Thermal Energy Storage (LHTES) units are crucial in managing the variability of solar energy in solar thermal storage systems. This study explores the effectiveness of strategically placing layers of anisotropic and uniform metal foam (MF) within an LHTES to optimize the melting times of phase-change materials (PCMs) in three different setups. Using the enthalpy–porosity approach and finite element method simulations for fluid dynamics in MF, this research evaluates the impact of the metal foam’s anisotropy parameter (Kn) and orientation angle (ω) on thermal performance. The results indicate that the configuration placing the anisotropic MF layer to channel heat towards the lower right corner shortens the phase transition time by 2.72% compared to other setups. Conversely, the middle setup experiences extended melting periods, particularly when ω is at 90°—an increase in Kn from 0.1 to 0.2 cuts the melting time by 4.14%, although it remains the least efficient option. The findings highlight the critical influence of MF anisotropy and the pivotal role of ω = 45°. Angles greater than this significantly increase the liquefaction time, especially at higher Kn values, due to altered thermal conductivity directions. Furthermore, the tactical placement of the anisotropic MF layer significantly boosts thermal efficiency, as evidenced by a 13.12% reduction in the PCM liquefaction time, most notably in configurations with a lower angle orientation.

New hybrid nano- and bio-based phase change material containing graphene-copper particles hosting beeswax-coconut oil for solar thermal energy storage: Predictive modeling and evaluation using machine learning

Although utilizing phase change materials (PCMs) for thermal energy storage and management has remarkably grown, the reliance on petroleum-based PCMs has raised concerns about their sustainability. Hence, in this study, the mixture of beeswax (BW) and coconut oil (CO) as a new biological-based PCM (bio-PCM) was developed. Also, the effect of 0.5, 1, and 2 wt% of graphene-copper (Gr-Cu) hybrid nanoparticles on the bio-PCM's ability in thermal energy storage (TES) was scrutinized. Thermal, chemical, physical, and stability specifications of BW-CO/Gr-Cu nano- and bio-based PCMs (bio-nPCMs) were examined by Differential Scanning Calorimeter (DSC), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Also, the thermal conductivity of bio-PCM and bio-nPCMs were explored in a range of temperatures from 25 to 60 °C. FTIR indicated no chemical reactions or new synthesis materials in the final composite. Also, all the used materials were recognized by XRD. DSC analysis showed that melting and solidification of bio-PCM start at 51 and 56 °C while adding 2 wt% Gr-Cu nanoparticles reduced the temperatures to 49.9 °C and 53.8 °C, respectively. In addition, bio-PCM had latent heats of 172.3 kJ/kg and 173.11 kJ/kg for melting and solidification, whereas 2 wt% Gr-Cu nanoparticles shifted them to 160.75 kJ/kg and 167.45 kJ/kg, in respect. On the other hand, the higher the concentration of Gr-Cu in the base PCM, the higher the thermal conductivity of bio-nPCMs maximally about 604 % higher than that of the base bio-PCM at T = 25 °C. Furthermore, a new model was proposed for the thermal conductivity that had an average error of 5 %. Machine learning was employed to estimate the thermal conductivity and latent heat. The former with R-squared, mean error (MSE), and average absolute relative deviation (%AARD) of 0.9996, 1.1253 × 10−4, 1.871, and the latter with 1, 4.7 × 10−10, and 0.01, respectively. The outcomes of this study present a procedure to develop future bio-PCMs and hybrid nanoparticles to pave the way to reaching net-zero carbon.

Parabolic trough solar collector technology using TiO2 nanofluids with dimpled tubes

Nanoparticle concentrations have recently attracted attention as a means to increase the effectiveness of parabolic trough solar collectors (PTSC). Computational fluid dynamics (CFD) study has recently gained popularity for evaluating the performance of PTSC with Dimpled Tubes using a nanofluid made of TiO2 nanoparticles distributed in deionized water (DI-H2O). The effect of using Dimpled Tubes with varied turbulent flow rates, from 0.5 kg/minto 2.5 kg/min, is studied via a battery of tests and computational fluid dynamics simulations. TiO2nanofluid performance is compared to water, the “base fluid,” in this study.This study investigates the utilization of TiO2 nanofluids in enhancing the heat transfer performance of parabolic trough solar collector (PTSC) technology, particularly when integrated with dimpled tubes.The importance of this research lies in the quest for improving the efficiency of solar thermal systems, which is crucial for sustainable energy production.Variables such as solar collector efficiency, Reynolds number, and Nusselt number are tracked as the inquiry progresses. When TiO2 nanofluids are added to the base fluid within the dimpled tube, the convective heat transfer coefficient increases by an astonishing 34.25 percent.This improvement is most pronounced at a mass flow rate of 2.5 kg/min and a volume concentration of TiO2 nanofluid of 0.3 %. Parabolic trough solar collectors have recently been the focus of attempts to improve efficiency via nanoparticle concentrations. The paper uses Computational Fluid Dynamics analysis to investigate how well Dimpled Tubes work with TiO2/DI-H2O nanofluid. The significant increase in the convective heat transfer coefficient was clarified by experimental and CFD calculations that considered fluctuations in turbulent flow rates. The improvement is particularly striking at a mass flow rate and a volume concentration of TiO2 nanofluid.Findingsindicate a significant improvement in heat transfer rates when TiO2 nanofluids are used, particularly in conjunction with dimpled tubes. The combined effect leads to a notable thermal efficiency enhancement, representing the potential of nanofluid-based improvements in optimizing PTSC performance.

A novel nanoplastic removal method based on solar interface evaporation technology

The widespread presence of nanoplastics in water environment has become a prominent threat to human health, and it is urgent to develop low-carbon and efficient nanoplastic removal methods. In this work, a novel nanoplastic removal method based on solar interface evaporation technology was successfully developed. The solar interface evaporator was constructed by modifying the surface of sorghum straw with polypyrrole, which exhibited satisfactory evaporation rate (2.946 kg·m−2·h−1) with a solar steam conversion efficiency up to 95.4 %. The proposed evaporator was successfully applied to the removal of nanoplastics obtained from take-out lunch boxes, mineral water bottles and plastic bags. The device also showed potential application in seawater desalination and sewage treatment. The water transport and heat transfer during the evaporation process were simulated by finite element simulation. This work sheds new light on nanoplastic removal and expands the application of solar interface evaporation techniques.

Ultra-high solar steam generation based on regulated water management strategy in 3D biomass hydrogels inspired by the “binding effect” of cell walls

Facing the global challenge of water scarcity, solar-driven seawater desalination has been emerged as a green, non-polluting and sustainable technology, but the practical application of existing solar evaporators was hindered by their low evaporation efficiency and poor mechanical property. Inspired by the binding effect of cell walls, a novel and high-efficiency three-dimensional (3D) evaporator (CDs/CF/CS-LF) was constructed, in which loofah (LF) served as a natural 3D skeleton to support the hydrogel evaporator, resisted deformation, and created an efficient dual water supply mode with the chitosan (CS) hydrogel ensuring that the evaporator maintains high evaporation rate even under high salt environment. Additionally, the cellulose nanofibers (CF) filler enhanced the mechanical property of the hydrogel, ensuring shape stability under pressure impact, and carbon dots (CDs) facilitated the aggregation and cross-linking of chitosan chains through hydrogen bonds, further improving the mechanical property of the evaporator, while also enhancing the photothermal conversion capability of the 3D-CDs/CF/CS-LF evaporator as a photothermal material. The experimental results indicated that the 3D-CDs/CF/CS-LF evaporator could achieve an ultra-high solar vapor production rate of 8.08 kg m−2 h−1 under 1 sunlight intensity in 3.5 wt% NaCl solution. Outdoor seawater desalination experiments demonstrated the utility of 3D-CDs/CF/CS-LF evaporator for practical applications. This work provided a new approach for the improvement of CS-based evaporators and demonstrated their potential application in seawater desalination and purification.

Corn straw coated with Fe3+-tannic acid bilayers as a photothermal material for solar steam generation

Recently, studies on developing a system to filter seawater into clean water using the method of water evaporation at the interface of photothermal materials and air using solar energy (solar steam generation - SSG) have attracted increasing attention from the scientific community. In those SSG systems, photothermal materials play a key role in improving water evaporation rate and efficiency. In this study, a photothermal material was fabricated by treating the corn straw with tannic acid and Fe3+ solution (cheap and environmentally friendly). The surface of photothermal material from corn stalks exhibited a good ability to absorb over 90% of light with wavelengths of 300-1500 nm due to the formation of a complex layer between Fe3+ ions and hydroxy groups (OH) of tannic acid with sizes of 200-1000 nm. Besides, corn straw consists of many vascular bundles and porous multilayers that exhibit a honeycomb-like structure, which improves the ability of water transportation and reduces the thermal conductivity of the material. Therefore, an SSG system utilising the photothermal material based on corn straw possesses a high-water evaporation efficiency of 1.58 kg m-2 h-1. This efficiency was stably maintained for a long time due to the durability of corn straw in various conditions. The corn straw-based photothermal material showed high potential for SSG utilising seawater desalination method with affordable fabrication cost and eco-friendly raw materials.

Helical Micropillar Processed by One-Step 3D Printing for Solar Thermal Conversion.

Solar thermal utilization has broad applications in a variety of fields. Currently, maximizing the photo-thermal conversion efficiency remains a research hotspot in this field. The exquisite plant structures in nature have greatly inspired human structural design across many domains. In this work, inspired by the photosynthesis of helical grass, a HM type solar absorber made in graphene-based composite sheets is used for solar thermal conversion. The unique design promoted more effective solar energy into thermal energy through multiple reflections and scattering of solar photons. Notably, the Helical Micropillar (HM) is fabricated using a one-step projection 3D printing process based on a special 3D helical beam. As a result, the solar absorber's absorbance value can reach 0.83 in the 400-2500nm range, and the surface temperature increased by ≈128.3% relative to the original temperature. The temperature rise rate of the solar absorber reached 22.4°Cmin-1, demonstrating the significant potential of the HM in practical applications of solar thermal energy collection and utilization.

Cobalt-Based Perovskites as Efficient Oxygen Exchange Redox Materials for Solar Thermochemical Application

Solar thermochemical CO2 splitting (STCS) cycles provide the promising routes to generate renewable fuel, fuel precursors, or chemical feedstocks by the utilization of renewable resources like solar thermal energy and CO2 relating to current energy as well as climate change. Perovskites have been proposed as the potential oxygen exchange redox materials for the two-step STCS process due to their greater oxygen release and redox stability. Herein, the oxygen release and redox stability were investigated for the cobalt-based perovskites (SrCoO3-δ and SrCo0.9Zr0.1O3-δ) as the potential STCS candidates. Consequently, the XRD, FT-IR, and Raman confirmed the dual-phase perovskite constitutions of SrCo0.9Zr0.1O3-δ (i.e. SrCoO2.29 and SrZrO3) compared to SrCoO3-δ. The thermogravimetric analysis indicated the incorporation of Zr could facilitate the oxygen release and enhance the phase stability. The near-equilibrium lattice oxygen release and uptake at high temperatures could be observed through the redox performance of SrCo0.9Zr0.1O3-δ at different heating and cooling rates. The results are noteworthy and demonstrate the potential of Zr-enhanced cobalt-based perovskites as the oxygen exchange redox materials for practical solar thermochemical applications.

Thermal Desalination Through Forward Osmosis Coupled With CO2-Mixture Power Cycles for CSP Applications

This work, performed in the framework of the H2020 EU project “DESOLINATION”, analyses the coupling between CSP plants using transcritical power cycles with CO2-mixtures and an innovative thermal desalination technique based on Forward Osmosis. Calculations are presented for a large scale CSP plant with central tower receiver and direct storage with solar salts in Dubai, adopting the mixtures CO2+SO2 and CO2+C6F6 in the power cycles. The heat rejected from the cycle condenser is recovered directly by the FO plant, where the draw solute is heated up from 40 °C to 76 °C, to allow for the regeneration of the draw solution used in the forward osmosis membrane. The thermo-responsive polymer adopted is PAGB2000, already considered in literature as a promising option. Results show a very effective synergy between the electricity and the freshwater production: high yearly solar to electric efficiencies are possible (around 19%), with a low freshwater specific thermal consumption (around 100 kWhth/m3). The proposed desalination method is more effective than a conventional MED system (with + 50% of yearly freshwater produced), while a larger solar field (+ 28% in surface area) is necessary for a PV+RO plant to produce annually both the energy and freshwater produced by the CSP+FO plants.

Impact of Temperature and Optical Error on the Combined Optical and Thermal Efficiency of Solar Tower Systems for Industrial Process Heat

Concentrating solar thermal (CST) power towers can provide high flux concentrations at commercial scale. As a result, CST towers exhibit potential for high-temperature solar industrial process heat (SIPH) applications. However, at higher operating temperatures, thermal radiation losses can be significant. This study explores the trade-off between thermal and optical losses for SIPH applications using a collection of three case studies at operating temperatures that range from 900-1,550 °C. We assume blackbody radiation to represent the thermal losses at the receiver and we use ray tracing to estimate the optical losses. The results show the impact of process temperature on the maximum attainable system efficiency, as well as the higher flux concentration requirements as the temperature increases.

GREEN AND SUSTAINABLE TECHNOLOGY IN THE GHANAIAN CONSTRUCTION INDUSTRY

Green and sustainable technologies pave the way for environmentally friendly and improve the conservation of natural resources. The study examined the application of green and sustainable technology within the school-built environment in Cape Coast Metropolis, Ghana. The qualitative research method was adopted to collect 92 responses from professionals and other stakeholders in the built environment, via a self-administered questionnaire. Data collected was analyzed using both descriptive statistical and relative importance index (RII). Findings show that thermal and photovoltaic solar energy, utilization of construction and demolition waste products were the most common and more familiar green and sustainable technologies in the built environment. The study also revealed the reduction in waste generation, improvement of indoor air quality, and savings of natural resources as positive impacts of applying green and sustainable technologies. Further findings revealed the unavailability of skilled human resources for the installation of the technologies, high research, and development costs, and much time consumption as piercing negative impacts of the green technology application in the built environment. Stakeholders in the built environment should apply and utilize green technologies to reduce the overall usage and consumption of energy and other raw materials to minimize the effects of global warming and improve the quality of air and water, as well as general projects.

Development and Investigation of Nitrate Phase Change Filler Material for Solar Process Heating Applications

Thermocline thermal energy storage system is an imperial system for solar process heating applications. The thermal energy storage system comprises filler material and heat transfer fluid. In the present study, the commercial phase change material (PCM) (filler material) solar salt (60%NaNO3+40%KNO3) is synthesized, and it is encapsulated with a 1mm thickness of stainless steel 316L encapsulation with the macro-size of 60mm; the encapsulated PCMs is considered as a single particle in the thermocline thermal energy storage system. The performance of the single encapsulated PCM is studied with a constant heat transfer fluid (Therminol-VP1) flow rate of 0.00015 kg/s during the charging process. The specific heat of the solar salt is measured in Differential Scanning Calorimeter (DSC) in the solid phase is found as 1.381 J/gK, and liquid phase is identified as 1.551 J/g-K, the enthalpy during the phase change process is found as 116.72 J/g. As well, the thermal conductivity of the solar salt is measured in Transient Heat Conduction method, and the thermal conductivity follows the linear relationship of -0.0025(T)+0.4023 (45ºC<T<100ºC) in the sensible region. The temperature variations and the phase change phenomena for the solar salt is identified and the contours are provided. The charging time for the encapsulated solar salt is identified as ~138 minutes. The energy storage cost for the single filler material (Solar Salt + SS316L encapsulation) is identified as Rs.5.93/- (USD 0.071) for the period of charging duration.

Enhanced performance of a hybrid adsorption desalination system integrated with solar PV/T collectors: Experimental investigation and machine learning modeling coupled with manta ray foraging algorithm

This study explores the performance augmentation of a solar adsorption desalination system (SADS) powered by a hybrid solar thermal system with evacuated tubes and photovoltaic thermal (PV/T) collectors, both numerically and experimentally. The system concurrently generates both electrical power via the PV/T system and desalinated water through the SADS. The cooling of photovoltaic cells is achieved through the utilization of chilled water produced during the desalination process of the SADS, which aims to enhance the electrical efficiency of photovoltaic cells and optimize the overall utilization of the adsorption distillation cycle. The SADS is examined under different operational scenarios and thoroughly assessed in terms of specific cooling power, specific daily freshwater product, and the coefficient of performance (COP). More so, a hybrid machine learning framework integrating an adaptive network-based fuzzy inference system (ANFIS) fine-tuned through the utilization of a manta ray foraging optimization algorithm (MRFOA) is also developed to predict the performance parameters of the SADS. The experiments indicated that the modified PV/T system improved the PV efficiency by 18 % at peak time, where the yielded electrical power and electrical efficiency reached 112 W/m2 and 11.13 %, respectively. The specific freshwater product (SWP), specific cooling power (SCP), and COP of the SADS are estimated as 53.3 L/ton-cycle (6.30 m3/ton-day), 153 W/kg, and 0.25, respectively. Furthermore, Furthermore, the simulated findings showed that the deterministic coefficient and RMSE of the predictive SWP are 0.989 and 1.314 for ANFIS-MRFOA and 0.965 and 2.323 for typical ANFIS, respectively. Hence, the ANFIS-MRFOA exhibited the highest prediction accuracy and can be deemed a potent optimization tool for forecasting the energetic performance of adsorption distillation systems.

5G as Communication Platform for Solar Tower Plants

Wiring of heliostat fields for solar tower plants is a cost factor that becomes more important as the overall cost target is decreasing. Wireless heliostats with radio communication and autarchic energy supply have therefore been proposed in the past. But none of the communication solutions investigated so far could realistically scale to commercial size plants with tens of thousands of heliostats. Moreover, the digitalization of CSP plants with numerous mobile and stationary sensor systems requires a suitable data communication, too. The new generation of mobile radio communication (5G) is capable of handling the heterogenous communication profile portfolio comprising large numbers of units with low data rates – like heliostats - and few units with very large data volume – like e.g. drone-based camera systems. The communication requirements of a typical solar tower installation are assessed in this work and a data traffic model is created for the most relevant communication channels. The various existing 5G implementations are assessed to find the most suitable solution. Different operator models for 5G are considered and their applicability in CSP target countries is discussed. A simulation test case is presented that models the radio communication traffic of a heliostat field control during a cloud passage. Finally, the experimental 5G campus network is introduced that is currently installed at the Solar Tower Jülich research plant and will be operated in the upcoming months to demonstrate the technical feasibility of 5G radio for communication in solar fields.

Optimized Photothermal Conversion Ability through Interband Transitions in FeCoNiCrMn High-Entropy-Alloy Nanoparticles.

High-entropy-alloy nanoparticles (HEA-NPs) composed of 3d transition metallic elements have attracted intensive attention in photothermal conversion regions due to their d-d interband transitions (IBTs). However, the effect arising from the unbalanced elemental ratio still needs more focus. In this work, FeCoNiCrMn HEA-NPs with different elemental ratios among Cr and Mn have been employed to clarify the impact of different composed elements on the optical absorption and photothermal conversion performance. It can be recognized that the unbalanced elemental ratio of HEA-NPs can reduce the photothermal performance. Density functional theory calculation demonstrated that d-d IBTs can be changed by the different composed element ratios, resulting in a number of insufficient filling regions around the Fermi level (±4 eV). As a result, the HEA-NPs (FeCoNiCr0.75Mn0.25) with a balanced elemental ratio exhibit the highest surface temperature of 97.6 °C under 1 sun irradiation, and the evaporation rate and energy conversion efficiency could reach 2.13 kg·m-2·h-1 and 93%, respectively, demonstrating effective solar steam generation behavior.

Comparative Assessment of the Durability of Glass and Polymer Mirrors for Concentrated Solar Thermal Technologies

This paper describes experimental work that has been carried out to assess the durability of glass and polymer mirrors against erosion and soiling phenomena. Both outdoor and indoor tests have been performed and the results show that polymer mirrors are quickly degraded in comparison to glass. Soiling deposition has been simulated using a soiling test rig developed for laboratory use. Results show that polymer mirrors, due to their high roughness and their surface energy properties, can accumulate more soiling on their surface generating a higher drop in specular reflectance compared to glass mirrors. Contact cleaning processes have also been simulated on polymer mirrors and the results show that using a hard brush, even at low speed with rotational motion, causes significantly more degradation than a soft brush.

3D printing of bio-inspired porous polymeric solar steam generators for efficient and sustainable desalination

Freshwater scarcity is a pressing issue worldwide, and solar steam generators (SSGs) have emerged as a promising device for seawater desalination, harnessing renewable solar energy to facilitate sustainable water evaporation. The facile fabrication approach for SSG with complex topologies to achieve high water evaporation efficiency remains a challenge. Herein, a MIL-101 (Fe)-derived C@Fe3O4 ink was employed to multi-jet fusion (MJF) printing of polymeric porous SSGs with specific topologies. The optimized porous structure endows the printed SSGs with capillary force, greatly promoting water transport. The tree-like topology enables high water evaporation rates under various simulated solar radiation conditions. A finite element model was built to fully understand the light-to-thermal energy conversion and water evaporation processes. Moreover, the MJF-printed SSGs exhibit self-cleaning properties and can automatically remove accumulated salt on their surfaces, enabling sustainable desalination. During prolonged testing, the water evaporation rate of the SSGs remained relatively stable and reached as high as 1.55 kg m−2 h−1. Additionally, the desalinated water met the standards for direct drinking water. This study presents a state-of-the-art technology for producing efficient SSGs for desalination and introduces a novel method for MJF printing of functional nanocomposites.