Solar Heating Research Articles

Rapid heating rates define the volatile emission and regolith composition of (3200) Phaethon

Asteroid (3200) Phaethon experiences extreme solar radiant heating ( ~ 750 °C) during perihelion (0.14 au), leading to comet-like activity. The regolith composition and mechanism of volatile emission are unknown but key to understanding JAXA’s DESTINY+ mission data (fly-by in 2029) and the fate of near-Sun asteroids more generally. By subjecting CM chondrite fragments to fast, open system, cyclic heating (2-20 °C/min), simulating conditions on Phaethon we demonstrate that rapid heating rates combine with the low permeability, resulting in reactions between volatile gases and decomposing minerals. The retention of S-bearing gas limits the thermal decomposition of Fe-sulphides, allowing these minerals to survive repeated heating cycles. Slow escape of S-bearing gases provides a mechanism for repeated gas release from a thermally processed surface and, therefore the comet-like activity without requiring surface renewal to expose fresh material each perihelion cycle. We predict Phaethon regolith is composed of olivine, Fe-sulphides, Ca-sulphates and hematite.

Simulation study on thermal performance of solar coupled air source heat pump system with phase change heat storage in cold regions

The development of efficient and clean heating technologies is profoundly significant for the reduction of carbon emissions in cold regions. This paper puts forth a novel solar-coupled air source heat pump system integrated with phase change heat storage technology, which is well-suited for regions with such climatic conditions. A numerical model of the components and coupled systems is established using the lumped parameter method, and an iterative method is employed for the computational solution in MATLAB software. A variety of system performance aspects are then simulated and analysed following the configuration of component structural parameters and initial operating conditions. The results of the simulations indicate that an increase in the phase change temperature interval of the phase change materials leads to a higher average heat release power. In particular, a 2 °C increase in the phase change temperature interval results in an increase in the heat release power of over 10 %. Furthermore, when the system is applied in typical cold regions, including Kunming, Hangzhou, Lhasa, and Harbin, the average coefficient of performance is 10.23, 8.87, 8.49, and 7.70, respectively. The proportion of solar energy input contributes to an increase in system efficiency across all regions. A case study of Hangzhou reveals that the incorporation of solar energy into the system results in an increase in efficiency of 70.91 %. This research provides valuable operational methods and site selection recommendations for engineering practices, laying a theoretical foundation for its widespread application in cold regions.

Feasibility study of a metal hydride-based solar thermal collector system

The present study aims to assess the technical feasibility of a novel Metal Hydride-based Solar Thermal Collector (MH-STC) system. This system includes a flat-plate solar collector integrated with a metal hydride bed, a hydrogen compressor, a photovoltaic panel, a hydrogen tank, and a water storage tank. This system combines the principles of a conventional solar thermal collector with the energy storage capabilities of metal hydrides, enabling the storage of surplus thermal energy. The LaNi5 alloy was used as heat storage material. A 3D-mathematical model is established and a numerical code written in Fortran-90 is developed to simulate the dynamic behavior of the proposed solar thermal collector. It was shown that the developed 3D-model produces computational results that are consistent with experimental data. In addition, to check the accuracy of the mathematical model and numerical approach, the relative errors in the mass balance and energy balance were calculated and values of 0.054 % and 0.18 %, respectively, were obtained.The simulation results offer insights into the system's technical feasibility, revealing an overall efficiency of 90.6 %, the water temperature at the collector outlet can reach 357.3 K, and a water volume heated of 230.4 L under the considered operating conditions. Moreover, the results indicate that the proposed MH-STC system exhibits significant potential as a viable alternative for thermal storage in domestic hot water systems.

Numerical investigation of free convection inside square wavy enclosure using response surface methodology

AbstractFree convection is commonly applied in various engineering fields such as solar energy, electronic devices, nuclear energy, and heat exchangers. A computational simulation was used to analyze the natural heat transfer through convection in a wavy cavity with squared shape that was filled with tap water and saturated metal foam to assess the influence of hump configuration (square, triangle, circular, down semicircular, and up semicircular) and magnetic fields (magnetohydrodynamics) on heat transfer rate. The bottom wavy wall of the enclosure exhibits a high temperature (Th), whereas the top and side walls maintain a low temperature (Tc). The present paper will examine how the bottom wall hump number (N), aspect ratio (L), geometry inclination angle (θ), Hartman number (Ha), magnetic field intensity inclination angle (ɤ) affects the heat transfer rate at various Rayleigh numbers. When the circular hump design is used with specific parameters, including ɛ = 0.85, L = 1.25, N = 4, Tc = 0°C, θ = 0°, Ha = 600 and ɤ = 45°, for different Ra values, it leads to increased heat transfer and notable improvements in heat transfer enhancement (ɸ) and energy enhancement (e). The enhancements were measured at 2.5 times for heat transfer enhancement and 8.9 times for energy enhancement. Moreover, the ideal case of the current study had Ha = 600, L = 1.25, Ra = 30 × 103, and θ = 0° compared to the baseline case. Simulations were accomplished using CFD. The results demonstrate that the primary goal of the research was achieved by optimizing the design, leading to a significant improvement in hydrothermal performance for both ɸ = 2.5 and e = 8.9.

Modeling and manufacturing of solar modules of different designs for energy supply of biogas plant

The article presents a description of the modeling and manufacturing of solar modules of photovoltaic, thermal and photovoltaic thermal designs intended to supply energy to a biogas plant intended for the production of biohydrogen and biomethane. Mathematical modeling of the photovoltaic module was carried out and the calculated temperature of the photovoltaic converters was determined, and also the photovoltaic module was manufactured using the process of sealing the photovoltaic converters with a two-component polysiloxane compound. Mathematical modeling of a solar thermal collector with water radiators in the form of a round copper tube, an oval copper tube, as well as a rectangular water cooling channel (“water jacket”) was also carried out, in which pressure losses and the amount of water heating were assessed. The distances between the rectangular channels of the water-cooling radiator for uniform heat removal were determined, and mathematical modeling of the thermal state of a solar thermal collector with a semicircular cross-section of the water-cooling radiator channel was carried out, after which the solar thermal collector was manufactured. Mathematical modeling of the total displacements of the components of a photovoltaic thermal module, the values of which do not exceed acceptable limits, was carried out, after which a photovoltaic thermal module was manufactured using the process of sealing photovoltaic converters with a two-component polysiloxane compound.

Graphene-based Cr-GaAs-Ag multilayer absorber structure for solar heating applications

The optimization of the solar absorber is very important to develop the efficiency of the solar absorber. We have designed here one solar absorber which is optimized using variation in different physical parameters. The design of this absorber is based on Cr-GaAS-Ag materials which is also based on a thin film graphene material. The designed solar structure is used for heating applications which can be applied in industrial use. The highest absorption of more than 99 % is achieved for different wavelengths. The design also shows the 97.1 % absorption for the 1000 nm wavelength. The optimization section is also provided in this research at the end of results section. The conclusions are obtained using absorption for the different layer structures in this research. Layer by layer analysis for the absorption is provided in this manuscript. The research is aimed at renewable energy use in the industries by providing sustainable heating applications.

Non-uniform variation characteristics of temperature field and corresponding thermal effect of longitudinal continuous slab ballastless track structure

The longitudinal continuous slab ballastless track structure (LCSBTS) easily suffers from interface and joint damage when subjected to extremely high-temperature loads, significantly affecting the running smoothness and safety of high-speed trains. This paper establishes a numerical model of the LCSBTS using the heat transfer principle and real-time shadow technology to replicate the time-varying evolution and spatial distribution of the temperature field. The corresponding thermal effect is obtained based on the sequential thermal-mechanical coupling method. The results show that the temperature variation and the corresponding thermal effect exhibit strong temporal-spatial non-uniformity on the horizontal and vertical planes of the LCSBTS. Solar radiation and heat convection are the dominant factors for the temperature field of the LCSBTS in the daytime and night, respectively, resulting in a higher temperature and greater thermal deformation on the sunny side than on the shady one. The temperature and vertical thermal deformation along the longitudinal direction vary periodically with a specific wavelength between the two adjacent rail support concrete blocks. The thermal deformation increments under the studied non-uniform temperature loads cause an interface damage increment. Finally, the consideration of a non-uniform temperature load produces remarkably different thermal effects from those given by the design temperature load.

SnO2/Silver Nanowire/Polyimide Flexible Transparent Conductive Films for Double-Sided Perovskite Solar Cells and Heaters

SnO₂/Silver Nanowire/Polyimide Flexible Transparent Conductive Films for Double-Sided Perovskite Solar Cells and Heaters

Accuracy of daily extreme air temperatures under natural variations in thermometer screen ventilation

AbstractAccurate air temperatures underpin environmental research. Most professional meteorological air temperature measurements still expose thermometers within traditional, naturally ventilated screens. Their representation of true air temperature depends on screen airflow, and therefore local winds. Accuracies of daily maximum (Tmax) and minimum (Tmin) air temperatures are assessed by comparison between a naturally ventilated large conventional screen and a co‐located aspirated reference screen. In over 1200 days' data, the naturally ventilated Tmin and Tmax both showed small (median < 0.06°C) cold bias, but, in 1% of cases, warm Tmax bias and cold Tmin bias >|1°C|. The Tmin cold bias is associated with calm clear nights, and the Tmax warm bias events with calm winter days at low sun angles, allowing solar heating of the screen. The prevalence of poor natural ventilation, potentially affecting Tmin and Tmax, is estimated across European sites. Poor ventilation occurred at Tmin for 12% of values, and at Tmax for 4%. Climatological averaging will reduce these effects, but, without corroborating wind data, statistical changes in Tmin or Tmax, including identifying “Tropical Nights” (Tmin > 20°C) or occurrences of winter extremes, may have limited value. Wider adoption of aspirated thermometer screens, with an initial overlap period, will largely eliminate these effects.

Design of a dynamically switchable metamaterial solar heating and daytime radiative cooling device based on reversible metal electrodeposition

Abstract The combination of daytime radiative cooling and solar heating can regulate the temperature of buildings in all seasons, which is vital to achieving energy savings. However, achieving a dynamic and efficient switch between radiative cooling and solar heating states is still challenging. The reversible metal electrodeposition is a promising electrochromic (EC) technology that can dynamically manipulate the visible and infrared spectrum by depositing a nanoscale metal layer. By combining it with a delicate nanostructure design, reconfigurable daytime radiative cooling and solar heating states can be achieved. In this work, a metamaterial EC device capable of efficiently switching between high solar reflectance (91.73%) and high solar absorptance (95.41%) via reversible silver layer electrodeposition has been developed. This device consists of a top layer, which is a visible transparent electrode of indium tin oxide covered with an ultrathin platinum film, an electrolyte in the middle, and a metamaterial absorber based on a metal/dielectric multilayered structure at the bottom. Afterward, we analyze the spectrum of each part of the device and carry out a parametric study on the practical performance with different ambient temperatures and convective heat transfer coefficients. The average solar reflectance of the device in the radiative cooling state is 93.41% within the range of 0.3–2.5 μm. In the solar heating mode, the average solar absorptance of the device reaches 95.46%. Numerical simulations show that the device in the cooling mode achieves a temperature drop of 5 °C–9.8 °C and an average cooling power of 140.8 W m − 2 . The device in heating mode achieves a maximum temperature rise of 45 °C and a maximum heating power of 700 W m − 2 . This work provides a feasible design for solar heating and daytime radiative cooling switching devices, which is promising in applications like energy-saving buildings, wearable devices, electric vehicles and other outdoors facilities.

Model-based optimisation of solar-assisted ORC-based power unit for domestic micro-cogeneration

Integrating flat solar thermal collectors and organic Rankine cycle (ORC)-based power units in micro-cogeneration systems ensures a reduction in CO2 emissions in domestic applications. The key component of these systems is the expander, which must withstand frequent off-design operating conditions owing to the intermittent nature of the solar source. Despite being in the first stage of technological development, scroll expanders are widely adopted in small-scale applications owing to their operating flexibility and robustness. In this study, a domestic micro-cogeneration unit equipped with a scroll expander is characterised experimentally. The experimental data are used to calibrate the expander and ORC unit models. The models are used to evaluate the operating limits of the units as functions of the main operating parameters. The maximum power and efficiency are obtained as 300 W and 3 %, respectively, for hot water temperatures between 90 °C and 100 °C, close to the rated performances. Finally, the effect of adopting a dual-intake port on the expander and unit performance is assessed. The technology facilitates the widening of the operating range (20–140 g/s mass flow rate of WF) and a peak power production of 1.2 kW.

Solar Thermal Integrated Alkaline Water Electrolyser for Fast Ramping Up

There is significant recent interest in clean hydrogen production from renewable water electrolysis. In general, alkaline water electrolysis (AWE) operates with a voltage of ca. 2 V due to ohmic and overpotential-derived loss (0.7~0.8 V) [1]. In addition, it requires 0.5~1 hours for the ramping-up, which hinders its wider implementation. Our intended solution is to introduce a heat-tolerant electrolyser integrated with a chemically resistant solar thermal collector, providing a heated electrolyte to increase the reactivity [2] and reduce the ramp-up time. In this work, we discuss key dimensional design aspects of the thermal collector for alkaline electrolyser, considering the control feasibility of operating temperature and fluidic parameters. Furthermore, we also demonstrate our proof-of-concept experimental results using our alkaline electrolyser integrated with the solar-thermal collector at an elevated temperature. The time-dependent current output of the solar-thermal integrated AWE over the first 1 h yielded ca. 70% higher compared to the conventional AWE system. E. Amores, J. Rodríguez, J. Oviedo, A. De Lucas-Consuegra, Open Eng 2017, 7,141–152.B. Zhang, Q. Daniel, M. Cheng, L. Fan, L. Sun, Faraday Discuss 2017, 198, 169–179 Figure 1

Customized Ultrathin Oxygen Vacancy-Rich Bi2W0.2Mo0.8O6 Nanosheets Enabling a Stepwise Charge Separation Relay and Exposure of Lewis Acid Sites toward Broad-Spectrum Photothermal Catalysis.

Designing robust photocatalysts with broad light absorption, effective charge separation, and sufficient reactive sites is critical for achieving efficient solar energy conversion. However, realizing these aims simultaneously through a single material modulation approach poses a challenge. Here, a 2D ultrathin oxygen vacancy (Ov)-rich Bi2W0.2Mo0.8O6 solid solution photocatalyst is designed and fabricated to tackle the dilemma through component and structure optimization. Specifically, the construction of a solid solution with ultrathin structure initially facilitates the separation of photoinduced electron-hole pairs, while the introduction of Ov strengthens such separation. In the meantime, the presence of Ov extends light absorption to the NIR region, triggering a photothermal effect that further enhances the charge separation and accelerates the redox reaction. As such, photoinduced charge carriers in the Ov-Bi2W0.2Mo0.8O6 are separated step by step via the synergistic action of 2D solid solution, OV, and solar heating. Furthermore, the introduction of OV exposes surface metal sites that serve as reactive Lewis acid sites, promoting the adsorption and activation of toluene. Consequently, the designed Ov-Bi2W0.2Mo0.8O6 reveals an enhanced photothermal catalytic toluene oxidation rate of 2445µmolg-1h-1 under a wide spectrum without extra heat input. The performance is 9.0 and 3.9 times that of Bi2WO6 and Bi2MoO6 nanosheets, respectively.

Evaluation of a building envelope Heat Transfer Coefficient in use: Bayesian approach to improve the inclusion of solar gains

Accurately measuring the actual building performance would be a significant step toward performance contracting. Methods under occupancy have operational advantages but come with additional constraints due to the variability of weather and occupancy conditions, which cannot be overlooked. Especially in recent, well-insulated buildings, since solar gains are a larger contribution to the global heat balance. This work aims to enhance the accuracy of the Heat Transfer Coefficient estimation in an occupied building by taking better account of solar gains in multilinear regression models. The approach adopted here considers solar gains from both the incident solar heat flux through glazing and from the opaque elements of a building by calculating an equivalent outdoor temperature. This model feeds a multilinear regression model whose parameters are estimated by Bayesian inference. Our model for estimating HTC is validated against a set of virtual data from a simulated detached house under different weather conditions.

Exploring double-diffusive convection in ferromagnetic Carreau nanofluid with magnetic dipole: Insights for solar thermal systems over plate, wedge, and stagnation

The use of ferromagnetic Carreau nanofluid in solar thermal systems enhances heat transfer and magnetic effects, optimizing solar collector design, improving solar power efficiency, and innovating nanofluid-based solar heaters and energy storage. Magnetic nanostructures significantly impact viscosity and thermophysical properties, influencing Ferrofluids' magneto-viscous nature. The investigation illustrates double-diffusive convection in radiative flow past three different geometries of ferromagnetic Carreau nanofluid, emphasizing the novel discussion of diffuse-thermal and thermo-diffusion impacts. Numerical solutions are obtained using the shooting technique with the Runge-Kutta fourth-order approach. Graphs and numerical data in tables depict the impacts of pertinent parameters. The study reveals that the radiation parameter, Soret parameter, and Dufour parameter contribute to temperature improvement as they are enhanced. These findings showcase the potential for advancing solar thermal systems through the utilization of ferromagnetic Carreau nanofluid, offering insights for sustainable solar energy applications. As the thermophoresis parameter increases from 0.001 to 0.005, the percentage change in the Nusselt number decreases for all three locations: Plate (0.90 %–0.66 %), Wedge (0.77 %–0.62 %), and Stagnation Point (0.62 %–0.54 %). This indicates that while the absolute values of the Nusselt numbers increase, the rate of change becomes smaller as increases.

Colored Radiative Cooling and Flame-Retardant Polyurethane-Based Coatings: Selective Absorption/Reflection in Solar Waveband.

The aesthetic demand has become an imperative challenge to advance the practical and commercial application of daytime radiative cooling technology toward mitigating climate change. Meanwhile, the application of radiative cooling materials usually focuses on the building surface, related tightly to fire safety. Herein, the absorption and reflection spectra of organic and inorganic colorants are first compared in solar waveband, finding that iron oxides have higher reflectivity in NIR region. Second, three kinds of iron oxides-based colorants are selected to combine porous structure and silicon-modified ammonium polyphosphate (Si-APP) to engineer colored polyurethane-based (PU) coating, thus enhancing the reflectivity and flame retardancy. Together with reflectivity of more than 90% in near-infrared waveband and infrared emissivity of ≈91%, average temperature drops of ≈5.7, ≈7.9, and ≈3.8°C are achieved in porous PU/Fe2O3/Si-APP, porous PU/Fe2O3·H2O/Si-APP, and porous PU/Fe3O4·H2O/Si-APP, compared with dense control samples. The catalysis effect of iron oxides in the cross-linking reaction of pyrolysis products and dehydration mechanism of Si-APP enable PU coating to produce an intumescent and protective char residue. Consequently, PU composite coatings demonstrate desirable fire safety. The ingenious choice of colorants effectively minimizes the solar heating effect and trades off the daytime radiative cooling and aesthetic appearance requirement.

Application of solar thermal collectors for milk pasteurization to explore the potential of renewable energy in the dairy sector: Challenges and possibilities

Dairy farming has become a key business to fulfill the daily milk needs in populated countries like India. Conversely, pathogenic and spoilage microorganisms in raw milk are killed by applying different heat treatments to increase shelf life, preserve quality, and ensure safety. Among the heat treatment processes used at the dairy plant, pasteurization consumes a significant amount of heat, which increases the energy demand in the dairy sector. Since milk pasteurization occurs between 65°C and 150°C, multiple solar thermal collector alternatives are available for various kinds of pasteurization processes. Employing solar thermal collectors for milk pasteurization allows the dairy sector to use free solar energy. Solar energy in milk heat treatments minimizes fuel and power consumption, reducing carbon emissions and promoting sustainability. However, solar milk pasteurization in dairy sector is limited by the large area requirement, high initial cost, and weather dependency. There have been attempts to use different types of solar thermal collectors to pasteurize the milk in an effort to replace conventional energy usage with solar energy. The parameters of milk heat treatment, primarily pasteurization, have been discussed concerning energy usage. The benefits and limitations of various solar collectors for milk pasteurization and other heating applications in the dairy sector have been addressed. Multiple studies on integrating various solar thermal collectors with different pasteurization systems have been reviewed, summarized, and concluded.

Solar Water Heating System with Absorption Heat Transformer for Annual Continuous Water Heating

We show the performance of solar heating by coupling a Solar Water Heating System (SWHS) with an Absorption Heat Transformer (AHT) for annual continuous water heating. Solar Fraction (SF), Solar Heat Gain (SHG), and Auxiliary Heat (Qaux) were meticulously assessed for three Mexican cities located in the most characteristic climates (Saltillo, Toluca, and Tapachula). This rigorous assessment process ensures the reliability and accuracy of our findings. The potential reduction in net solar collector area (Ac) and storage tank volume (Vt) can be seen by comparing its annual performance to that of a conventional SWHS. Both configurations were designed to deliver the same hot water amount (0.019 kg/s, 1693.4 L/day, heating from 15.8 to 94.4 °C) and simulated using TRNSYS software version 16.01 concerning combinational systems. The results showed that SWHS-AHT achieved superior performance in solar water heating, achieving a higher SF (up to 99.6%) and SHG (up to 1352 kWh/m2-year) compared to the conventional SWHS. On the other hand, the SWHS-AHT achieved similar performance to a conventional SWHS with up to 60% less Ac. For instance, in Tapachula, a SWHS-AHT with an Ac of 150 m2 and a Vt of 18 m3 matched the performance of a SWHS with an Ac of 375 m2 and a Vt of 15 m3. Notably, both systems required the same Qaux. Thus, the Qaux requirement shows that SWHS-AHT is promising for industrial applications in Mexico, offering improved performance and a reduced footprint.

Laser-Tracing Multi-Station Measurements in a Non-Uniform-Temperature Field

Due to the increasing requirements for the improvement of the accuracy of large coordinate-measuring machines (CMMs), the laser-tracing multi-station measurement technology, as one of the advanced precision measurement technologies, is worth studying in depth in terms of its practical application for the compensation of errors in large CMMs. Since it is difficult to maintain a constant temperature of about 20 °C in the actual workshop under the influence of solar radiation and convective heat transfer, there is a gradient in the spatial temperature distribution, and the overall temperature changes with the influence of external factors with synchronous hysteresis, it is difficult for the actual calibration environment to meet the standard environmental requirements. Therefore, the influence of temperature and other environmental factors on the accuracy of laser ranging and large-scale CMM calibration should not be ignored. In this paper, on the basis of analyzing the temperature distribution and change rule of large CMM measurement space under different working conditions, the radial basis function (RBF) neural network algorithm was used to build a non-uniform-temperature field model, and based on this model and the measurement principle of the laser-tracking instrument, the method of laser tracking and interferometric ranging accuracy enhancement was put forward under a non-uniform-temperature field. Finally, based on the multi-station technique of laser tracing, an accurate solution for the volumetric error of large CMMs under the condition of non −20 °C ambient temperature was realized. Simulation results proved that compared with the traditional temperature-compensation method, the proposed method improved the measurement accuracy of the volumetric error of a large-scale CMM using laser-tracing multi-station technology in a non-uniform-temperature field by 33.5%. This study provides a new approach for improving the accuracy of laser-tracer multi-station measurement systems.

Combined solar and ground source heat pump heating system with a latent heat storage tank as a sustainable system to replace an oilfield hot water station

Present study focuses on a clean energy replacement for an oilfield hot water station and develops a combined solar and ground source heat pump (GSHP) heating system with a latent heat storage tank (LHST). The effects of LHST and heat replenishment on energy and coefficient of performance (COP) are quantitatively analyzed during short-term or long-term operation of the system. The suitability of three different phase change materials for the system is compared, and the optimal one is identified. Results show that the LHST with 70 °C melting point can increase the collector efficiency to 53.91 % and reduce the total energy consumption of the system by 52344 kWh. Heat replenishment could effectively mitigate the ground temperature drop to 0.19 °C/year, reducing the annual energy consumption of GSHP by more than 4230 kWh and providing an additional thermal energy of 72 GJ. Compared to the initial heating system, the novel system efficiency increases to 51.25 %. Gas consumption and total system energy consumption decreased by 81.7 % and 75.2 %, respectively. Annual reduction of CO2 emission is about 1150 tons, showing satisfactory performance. Outcomes of this study prove the application of clean energy in oil field industrial processes, and help in achieving the goals of emission reduction and carbon neutrality.