Solar Wall Research Articles

Prediction of room temperature in Trombe solar wall systems using machine learning algorithms

A Trombe wall-heating system is used to absorb solar energy to heat buildings. Different parameters affect the system performance for optimal heating. This study evaluated the performance of four machine learning algorithms—linear regression, k-nearest neighbors, random forest, and decision tree—for predicting the room temperature in a Trombe wall system. The accuracy of the algorithms was assessed using R² and RMSE values. The results demonstrated that the k-nearest neighbors and random forest algorithms exhibited superior performance, with R² and RMSE values of 1 and 0. In contrast, linear regression and decision tree showed weaker performance. These findings highlight the potential of advanced machine learning algorithms for accurate room temperature prediction in Trombe wall systems, enabling informed design decisions to enhance energy efficiency.

A Novel Concept of Nano-Enhanced Phase Change Material.

In the actual context of growing concerns over sustainability and energy efficiency, Phase Change Materials (PCMs) have gained attention as promising solutions for enhancing energy storage and release efficiency. On another hand, materials based on graphene oxide (GO) have proven antibacterial activity, biocompatibility, efficiency in microbial growth inhibition, and pollutant removal. Integrating nanoparticles into PCMs and creating Nano-Enhanced Phase Change Materials (NEPCMs) have opened new horizons for optimizing the performance of these systems and sustainable development. The key objective of this work is to gain insight into NECPMs, which are used in solar wall systems to enhance solar energy storage. Paraffin RT31 was mixed with Cu nanoparticles, graphene oxide (GO), and Cu-decorated GO (Cu@GO) at loading ratios ranging from 1% to 4% (w/w nanoparticles with respect to RT31). The compositions were characterized through Differential Scanning Calorimetry (DSC) and rheology tests. The decoration of the carbon-based nanoparticles was performed using the ultrasonication procedure, and the decoration efficiency was confirmed through X-ray Photoelectron Spectroscopy (XPS). The rheologic measurements were performed to correlate the flow behavior of the NEPCM with their composition at various temperatures. The study methodically investigated these composites' latent heat values, phase change peak temperatures, and solidification phase change temperatures. Compared to pure paraffin, the solidification of the formulations obtained using Cu@GO exhibits the largest increase in latent heat, with a 12.07% growth at a concentration of 2%. Additionally, at a 4% concentration of NEPCM, the largest increase in thermal conductivity was attained, namely 12.5%.

Experimental study on solar wall by considering parametric sensitivity analysis to enhance heat transfer and energy grade using compound parabolic concentrator and pulsating heat pipe

Enhancing high-grade and rapid thermal storage for solar energy utilization is of paramount importance in reducing building energy consumption. Therefore, this study combines the Compound Parabolic Concentrator (CPC) and Pulsating Heat Pipe (PHP) to propose an integrated CPC-PHP solar wall (CPC-PHP-SW) that can enhance solar energy grade and rapid thermal storage. The mixed working fluid for CPC-PHP-SW is developed to reduce the dependence on solar radiation intensity and facilitate PHP startup. Furthermore, the operating characteristics and heat transfer performances of the CPC-PHP-SW are studied experimentally under various factors, including solar radiation intensity, working fluid, and cooling temperature. Sensitivity analyses of these three factors on heat transfer performances are conducted using Multi-factor analysis of variance. Results highlight that solar radiation intensity is the most influential factor on heat transfer performance, followed by cooling temperature, and working fluid. Moreover, employing a CPC with a concentration ratio of 2 reduces thermal resistance by up to 56.46 %, while the maximum effective thermal conductivity increases by up to 129.65 %. A recommended methanol to water ratio is 1:3, which effectively copes with a wide range of solar radiation intensity. These findings provide valuable references for the design and application of CPC-PHP-SW in building envelopes.

An innovative drying method for on-site and precast walls – Efficiency in accelerating the drying of reduced-scale earth-lime-hemp composites

The drying of construction materials is a challenge regarding structure’s durability and costly construction delays. Long drying periods induce high-moisture content that leads to fungal growth risks. This study presents the development of an innovative forced convection drying method, inspired by unglazed transpired solar wall system and repurposed here for its drying potential at the wall scale. This method employs a metal perforated panel placed at a short distance from the material to dry. This creates an air cavity between them where forced convection is applied with ambient air penetrating through the perforated panel. The moistened air is evacuated thanks to an air circuit composed of a fan and an extraction duct. Two panel configurations with round and cross-shaped perforations are investigated and compared to a natural convection reference. The efficiency of the method is evaluated on Earth-Lime-Hemp composites. With forced convection method, the evaporation front moves moisture towards the near wall forced convection surface and leads to more efficient moisture removal. The results demonstrate a 50 % reduction in drying time using forced convection drying compared to natural convection drying in an open area. Both panel configurations show similar efficiency. The proposed drying method meets the challenges above-mentioned and is applicable for both prefabricated elements and on-site construction. Additionally, it can be effective for the restoration after water damage, enhancing overall construction resilience.

Harnessing Nanomaterials for Enhanced Energy Efficiency in Transpired Solar Collectors: A Review of Their Integration in Phase-Change Materials

The building sector plays an important role in the global climate change mitigation objectives. The reduction of CO2 emissions and energy consumption in the building sector has been intensively investigated in the last decades, with solar thermal energy considered to be one of the most promising solutions due to its abundance and accessibility. However, the discontinuity of solar energy has led to the study of thermal energy storage to improve the thermal performance of solar thermal systems. In this review paper, the integration of various types of phase-change materials (PCMs) in transpired solar collectors (TSC) is reviewed and discussed, with an emphasis on heat transfer enhancements, including nanomaterials. Thermal energy storage applied to TSC is studied in terms of design criteria, materials technologies, and its impact on thermal conductivity. This review highlights the potential of nanomaterial technology integration in terms of thermal performance improvements. The utilization of nanomaterials in solar walls holds the potential to significantly enhance their performance. The integration of diverse materials such as graphene, graphite, metal oxides, and carbon nanoparticles can pave the way for improving thermal conductivity.

Solar Wall Technology and Its Impact on Building Performance

Solar walls provide transformative solutions by harnessing solar energy to generate electricity, improve thermal comfort, and reduce energy consumption and emissions, contributing to zero-energy buildings and mitigating climate change. In hot and humid regions, solar walls can reduce indoor temperatures by 30% to 50%, significantly improving energy efficiency. Optimizing the performance of solar walls includes factors such as glazing, shading, solar orientation, ventilation, and catalytic techniques, allowing them to be adapted to different climates. Innovative solar wall variants that include photovoltaic panels, water storage, and phase-change materials offer multifunctionality and sustainability in building design and are in line with global energy efficiency and environmentally conscious goals. In addition, innovative solar wall variants that combine photovoltaic panels, water storage, and phase-change materials promise even more sustainability in building design. These multifunctional solar wall systems can efficiently heat, cool, and generate energy, further reducing a building’s environmental impact. Solar walls have the potential to significantly reduce heating energy consumption; align with global goals for energy-efficient, environmentally conscious, and climate-responsive building design; and offer dynamic and adaptable solutions for sustainable architecture.

A scalable solar-based adsorption thermal battery for day and night heating in a low-carbon scenario

A proof-of-concept realization of a solar ATB wall envelope integrated into a residential building, which comprises a high-performance thermal battery and solar wall design, aiming at achieving day and night space heating in low-carbon scenarios.

Improving summer cooling in the Egypt hot/dry arid region utilizing a Trombe wall system: A field investigation

Air conditioning systems consume a large amount of generated electrical energy. Meanwhile, countries face an energy crisis due to the weakening of fossil energy, the world's largest energy source. Researchers were compelled to look for alternate energy sources and realized that solar energy was one of the most viable options. Also, it was found that solar energy may be used to power certain straightforward systems, such as Trombe walls, in place of air conditioning units. The Trombe wall is getting a lot of publicity and has been demonstrated to be very important and influential in today's environment preservation and energy conservation. The present work aims to extend the Trombe wall systems by installing them on residential structures. For a good design that suits the climate of the city of Sohag in Upper Egypt, a test chamber attached to the Trombe wall is set up in the summer, where different designs of Trombe wall configurations and operating conditions are studied. Five patterns of air gates (A, B, C, D, E) between a brick wall and wooden board slots are evaluated. Three different air gaps for Trombe air cavity distances of 100, 200, and 300 mm are examined. Test runs are assessed in two air entry modes via the window opening (mode-I) and the top hatch in the door (mode-II). The experiments are carried out on certain summer days for different summer months: June, July, August, September, and October. The most noteworthy findings revealed that the Trombe solar wall system in Sohag city had the optimum set-up circumstances with an air gap distance (XAG = 300 mm), air entry through window opening (mode-I), air gate arrangement (pattern-D), and plywood air spacing (WPW = 100 mm).

Numerical investigation of the effect of rectangular and semicircular cavities filled with phase change materials installed on the solar wall

The use of alternative energy sources, particularly solar energy, in buildings is rising and spreading around the globe. In this paper, a solar wall is analyzed using a numerical method. On the wall, a number of obstacles are placed in two shapes, rectangular (REC) and semicircular (SEC). The cavities are filled with organic phase-change materials. This study was performed in 7 h in the absence of solar radiation on the wall for different dimensions of obstacles in 5 different modes. Various temperatures have been investigated, including exhaust air temperature (TAR), Trombe wall temperature (TWL), and mean volume % of molten PCM in cavities. COMSOL software is used to carry out this numerical study. The results of this study showed that the use of SECs compared to RECs causes the TWL to be higher. In the most extreme case, at a 16 cm aspect ratio, the use of SECs gives a 2.1 °C increase in TWL relative to the REC one. The outlet TAR is also increased by the usage of SECs. The use of larger dimensions of the cavities has increased the TAR leaving the wall so that the TAR after 7 h of the absence of solar radiation, in the most significant case of SECs, was more than 295.5 K. The use of SECs also increases the PCM freezing time. In the largest case of cavities, using SECs increases the freezing time by 15 min compared to RECs.

Thermal performance analysis of PCM solar wall under variable natural conditions: An experimental study

Low-carbon technologies are critical for mitigating climate change and achieving net-zero emission buildings. Phase change material (PCM) solar wall as a low-carbon technology is a passive heating/cooling system with the potential to cover a significant portion of building energy demand. To better understand the potential of PCM solar walls in different climates, further research into their performance is needed. This research is based on an experimental investigation of the performance of the Solar wall test cell in changing natural conditions for cold and warm seasons. A series of experiments were conducted in both seasons by recording the variation of exterior and interior temperature, as well as solar radiation. Statistical tools were used to analyze the influence of variations in external air temperature and solar radiation on the thermal characteristics of the solar wall in the cell. The results showed a significant difference between external and internal temperature variations for both seasons. Particularly, the wall had the potential during the heating season to maintain the temperature of the test cell above 20 °C for up to 7 h, while in the cooling season, it is observed that the wall keeps room temperature for about 17 h within the comfort range.

Compound Heat Transfer Enhancement in Dimpled and Sinusoidal Metal Solar Wall Ducts Fitted with Wired Inserts

An improved Metal Solar Wall (MSW) with integrated thermal energy storage is presented in this research. The proposed MSW makes use of two, combined, enhanced heat transfer methods. One of the methods is characterized by filling the tested ducts with a commercially available copper Wired Inserts (WI), while the other one uses dimpled or sinusoidal shaped duct walls instead of plane walls. Ducts having square or semi-circular cross sectional areas are tested in this work.A developed numerical model for simulating the transported thermal energy in MSW is solved by finite difference method. The model is described by system of three governing energy equations. An experimental test rig has been built and six new duct configurations have been fabricated and tested. Air is passed through the six ducts with Reynolds numbers from 1825 to 7300.Six, new, correlations for Nusselt number and friction factor are developed to assess the benefits that are gained from using the WI and the dimpled and sine-wave duct walls. It is found that higher heat transfer rates are achieved using the Dimpled, semi–circular duct with Wired Inserts (DCWI). Also, it is found that Nusselt number and the pressure drop in the DCWI are respectively(44.2% -100%) and (101.27% - 172.8%) greater than those of the flat duct with WI. The improvement in Nusselt number for flat duct with WI is found to be (1.4 – 2) times the values for flat duct with no WI. The results demonstrated that DCWI provides enhancements efficiency value that is higher than those obtained from other types of ducts. The developed MSW ducts have added to local knowledge a better understanding of the compound heat transfer enhancement.

The energy savings achieved by various Trombe solar wall enhancement techniques for heating and cooling applications: A detailed review

The energy savings achieved by various Trombe solar wall enhancement techniques for heating and cooling applications: A detailed review

Overview of the Trombe-Michel wall application in concept of an energy-efficient building

The aim of the study is to consider different configurations of the Trombe-Michel wall. The researches of various scientists such as A. K. Soloviev, S. Corasaniti, L. Manni, F. Russo, F. Gori, V. V. Bryzgalin, K. N. Klevets have been studied. The construction of the Trombe-Michel wall has been described and compared with the solar wall. Heat fluxes and modifications of ventilation openings have been studied. The dependence of air flows on the configuration of the elements of the Trombe-Michel wall has been analyzed. The use of a passive house in the conditions of a heterogeneous climate in Russia has been considered. A comparative analysis of various passive houses is conducted. Effective methods for assessing the Trombe-Michel wall have been found. The possibility of achieving energy effiency and reducing the load on the systems for maintaining the microclimate of the building premises is described. The method of complex qualimetric assessment using four indicators has been considered.

Investigation on the dynamic thermal storage/release of the integrated PCM solar wall embedded with an evaporator

The integrated phase change materials (PCM) solar wall can store solar energy effectively, which has a broad application prospect. However, the integrated PCM solar wall cannot completely release heat at night. In this paper, the evaporator of the heat pump system is embedded in the integrated PCM solar wall, which can realize the combination of active and passive utilization of solar energy. A numerical study on the thermal storage/release characteristics of the integrated PCM solar wall with an embedded evaporator was carried out in this paper considering its two-dimensional heat transfer. The effect of the thermal release mode, the thermophysical parameters of PCM and the solar radiation intensity on the thermal storage/release characteristics was studied. The simulation results showed that the active thermal release mode increased the released heat by 33.33 kJ/kg, and the proportion of the released heat to the stored heat increases by 30.12%, compared with the passive thermal release mode. Moreover, the increase of the phase transition temperature and the thermal conductivity of PCM can increase the stored heat and released heat, and the latent heat of PCM will increase the stored heat and decrease the released heat. The conclusion can provide a theoretical basis for the research of active and passive solar systems.

Numerical study on the impact of wall structure on the thermal performance of double-channel porous solar wall

With the improvement of people’s living standards, they have higher requirements for indoor thermal comfort in the cold season. Solar wall utilizing solar energy for heating can reduce carbon emissions and achieve carbon neutrality. In the aspect of solar wall research, the influence of wall structure on the thermal performance of double-channel porous solar wall is limitedly investigated. In fact, the optimization design of wall structure is important for the thermal performance of solar wall and its applications. Therefore, a simplified three dimensional room model is built to study the influence of the wall structure on the thermal performance of porous solar wall by numerical simulation. With this model, different channel spacing and thickness of porous walls were used to determine the optimal design for a double-channel porous solar wall in terms of enhancing the heat storage. Moreover, the influence of the surface emissivity on the characteristics of heating and temperature field of double-channel porous solar wall are studied based on the optimal structure. The CFD simulation results indicate that the optimal structure parameters should include spacing of 0.08 m for channel 1, the porous wall thickness should be 0.08 m, and the air channel 2 spacing should be 0.06 m. The temperature of air channel 1 and air channel 2, the indoor temperature, and the heat storage of porous wall decrease with the increase of the surface emissivity of the porous wall. In order to improve the heat storage performance of double-channel porous solar wall, the outer surface of the porous wall should use a lower emissivity material. The outer surface emissivity of porous wall has a significant impact on the heat storage of the porous wall and little effect on the thermal storage wall. The temperature of porous wall is always higher than that of outdoor environment temperature.

Energy and exergy analysis of a glazed solar preheating collector wall with non-uniform perforated corrugated plate

The solar preheating wall provides an effective solution to the conflict between the requirement for fresh air and the need for heat conservation in winter by preheating fresh ventilation air. In this paper, a study of the glazed solar preheating collector wall is carried out by numerical simulation with the aim of improving heat collection efficiency through structural optimization. The influence of the environment as well as its range of applications are investigated. The characteristics of the internal flow and temperature distribution are obtained to facilitate the structural analysis. The influence of air volume and structural parameters on thermal efficiency is investigated, providing a good reference for structural design optimization. In addition, it is observed that the exergy efficiency of the optimized design is 1.3 times higher than that of the conventional solar wall, while the thermal efficiency is 15% higher than traditional ones. The heat loss rate is reduced by 40% in high wind and extremely cold regions compared to that of the unglazed one. The maximum supply percentage can reach 69.4% and the temperature rise is approximately 20 °C. Finally, a parametric investigation is carried out on different functional buildings, and an optimal structure in Xi'an is given as a reference. The energy collection and transfer efficiency increase with the increase of air volume, but the energy saving rate decreases. The results indicate that this solar wall is ideal for buildings with low fresh air demand, such as single residences and small offices. It also has a considerable preheating effect on high fresh air demand ones.

New Supply-Air Solar Wall with Thermal Storage Designed to Preheat Fresh Air: Development of a Numerical Model Adapted to Building Energy Simulation

Façades built with integrated passive solar systems hold great promise for improving the energy performance of buildings and achieving indoor comfort conditions. Among these techniques, solar air preheating systems with different configurations have proven their ability to reduce the energy consumption of buildings during the heating season. In this study, we propose a ventilated solar wall (VSW) with a thermal storage unit intended for preheating ventilation air. The final aim of this study is to determine the thermal performance of the studied VSW over a significant time period (during the heating season) under various climatic conditions when it is integrated into the building envelope. Therefore, for this purpose, a simplified model was developed to be coupled to a building energy simulation (BES) code. The results from the detailed steady-state 2D computational fluid dynamics (CFD) model show that the thermal efficiency of the VSW ranged from 55% to 70% as the air mass flow rate increased from 0.008 kg/s to 0.02 kg/s for a surface of 2.15 m2. These results were used to evaluate the convective heat transfer coefficients in the two air cavities and to validate the simplified model. The results indicate good agreement between the two models.

Thermal behavior estimation of a solar wall operated by TiO2 nanofluids using several machine learning models

Thermal behavior estimation of a solar wall operated by TiO2 nanofluids using several machine learning models

The effect of using phase change materials in a solar wall on the number of times of air conditioning per hour during day and night in different thicknesses of the solar wall

In this paper, the effect of using PCM in a solar wall is investigated numerically and analytically. For this purpose, a solar wall with a room in both PCM and PCM-free modes is simulated in the solar wall. The effective heat capacity method has been used to simulate the PCM melting process. The effect of using PCM in the solar wall in different heat fluxes, different wall thicknesses, average room temperature, etc. on the number of times of natural air conditioning in the room has been investigated. This analysis is performed as a transition for a full day. For this purpose, a handwritten code with COMSOL software has been used. The results of this study showed that storing solar energy in PCM as latent melting energy can provide 24-h ventilation in the room. This is also possible for small solar fluxes. Also, the use of PCM in the wall can significantly reduce the wall thickness. The results also show that the use of PCM with higher thermal conductivity increases the number of times of air conditioning. The highest number of air conditionings per hour occurred during the peak hours of solar radiation.

Thermoeconomic Analysis in Advanced Cogeneration Systems in Buildings

In this work thermoeconomics is applied to a central thermal system covering three buildings that consists of a cogeneration engine, an aerothermal heat pump and a natural gas condensing boiler. Cogeneration systems integrated with renewable energy technologies are very attractive solutions in the building sector. Nevertheless, the use of cogeneration systems together with active envelope solutions, such as the one encountered in this work, are scarce and the efforts to enhance the synergies between both systems are even scarcer. A heat pump is connected to a so-called solar wall to provide hot air and a renewable photovoltaic system supplies the electricity consumed by the heat pump. Thermoeconomics is applied to evaluate the cost of flows based on its energy-quality. Hence, this innovative and complex system can be analysed and diagnosed by this methodology. As a result, thermoeconomics is presented as an effective tool for the detailed study of the energy cost distribution and the key to enhancing energy efficiency.