Chimney Design Research Articles

Explainable Artificial Intelligence twin for metaheuristic optimization: double-skin facade with energy storage in buildings

Abstract The double facade solar chimney along with energy storage components is a sustainable building technology that harnesses the power of the sun to regulate indoor temperatures. Extensive research has been conducted on the theoretical simulation of such systems. The novelty of this work is to explore the potential of explainable artificial intelligence in improving the design and optimization of the double-skin solar chimney. The need for this research is owing to the high computational limitations of the physical model of such systems, thus the application of explainable artificial intelligence based upon Artificial Neural Network can address this research gap. The paper solved a validated physical model and demonstrates the suitability of Artificial Neural Network twins as computational-efficient subrogates that can be later used by a multi-objective optimization function to find the optimal design values for the facades of double-skin buildings. The results of the comparison between the physical and the Artificial Neural Network model show the practical advantage of utilizing the digital twin model without compromising accuracy. The results have indicated that the Artificial Neural Network can achieve a high coefficient of determination ranging from 0.921 to 0.999 on different performance indicators which implies a high goodness of fit. Accordingly, the optimization study based upon a non-sorting genetic algorithm (NSGA-II) has indicated a high ventilation rate of 2.86 1/h and an efficiency of 37.21%. The insights of this work have reflected that exploring the societal implications of sustainable building technologies such as the double facade solar chimney through educational initiatives can cultivate a new generation of society who not only understand the technical aspects but also appreciate the broader social and environmental contexts of their work, eventually to have future buildings with integrated passive systems.

PERBANDINGAN DESAIN PENGERING BERBASIS EFEK RUMAH KACA VARIASI CEROBONG PENGHAWAAN: IMPLEMENTASI PADA MASYARAKAT LOKAL

Greenhouse effect-based dryers are an efficient and environmentally friendly technological solution to improve the quality and added value of agricultural and fishery products. This research aims to analyze the comparative technical and economic performance of three variations of ventilation chimney designs, namely conventional, thermal, and multidirectional, in their implementation in local communities. Research methods include field experiments to measure technical parameters, such as temperature, humidity, drying time, and airflow speed, and economic analysis to calculate investment costs, payback period, and net profits. The results showed that the thermal chimney provided the best performance with an average temperature of 50°C, drying time of 21 hours, and high airflow efficiency, suitable for rural areas. Multidirectional chimneys are more flexible against unstable wind conditions, making them ideal for coastal areas. This technology is environmentally friendly with a reduction in carbon emissions of up to 1.2 tonnes of CO₂ per year per unit. The novelty of this research lies in the combination of innovative design, in-depth economic analysis, and the application of technology that is adaptive to local needs and challenges, making it relevant and beneficial to society and the environment. In conclusion, a greenhouse effect-based dryer with a ventilation chimney design is a technology that is feasible to apply to increase productivity, environmental sustainability, and the welfare of local communities.

Simulation and design of a solar chimney integrated with phase change material layer for building ventilation

The development of modern life requires new energy sources, and one of this energy is renewable solar energy uses in solar chimney for natural ventilation, but at the present time it is not greatly invested, taking into account the weather conditions of the region and the physical characteristics of solar radiation and air in the area in which the study will be conducted. The current study was carried out in Basrah city- Iraq, at longitude 47.749° and latitude 30.568°, where the solar chimney was facing south. The investigation was conducted using both theoretical and experimental studied. In the theoretical study, the solar chimney with the room in the presence and absence of PCM was simulated numerically using the finite volume method using the soft package ANSYS-Fluent/2021/R2. The effect of different tilt angles (α = 30°, 45°, and 60°), solar chimney air gap (gab = 10 cm, 15 cm, and 20 cm), and PCM basin thickness (tPCM = 3 cm, 4 cm, and 5 cm) were investigated. The results were presented in the form of contours of the distribution of streamlines, velocity, temperature, and liquid fraction of the solar chimney with the room, rate of temperature of the absorber plate with time and the rate of temperature of the PCM (TPCM) with time, rate of air change per hour (ACH). As for the experimental side, the device was built, and the intensity of solar radiation was studied for several days on 30 Sep. and 15 Oct. 2023, the temperature distribution rate of the absorbent plate over time, the PCM temperature rate, and the air change per hour (ACH). The theoretical results were compared with the experimental results, where there was good agreement, and the theoretical comparison was also made with several researchers. Significant results showed that the optimal ratio of the air gap width of the solar chimney is 15 cm, the inclination angle of the solar chimney α = 30°, and the thickness of the PCM basin (tPCM = 4 cm) to obtain the maximum ventilation rate. The thickness of the PCM basin = 4 cm gives the largest liquid fraction along time and maximum average temperature of the absorber plate. On the experimental, it was found that PCM convert into the liquid phase after its melting point, which is 340 K, after 12 noon, and the highest value of ACH reached 37 on September 30/2023 at midday.

Solar chimney design in rural areas of Anhui, China: CFD simulation, energy and carbon footprint assessment

China is currently undergoing a large-scale renovation of rural buildings. The solar chimney, a passive solar system, emerges as a cost-effective and easily implementable solution, particularly suitable for rural regions. This study designs a solar chimney in the Hui architectural style for renovating residential buildings in rural areas of Anhui province. A selected pilot building serves as the testbed for the solar chimney implementation, with plans to extend the design to other local renovation projects. Computational Fluid Dynamics (CFD) simulations are employed to compare various solar chimney configurations and identify the optimal design for the case study. Results from the CFD simulations highlight the optimal configurations for the pilot building's solar chimney design. Additionally, a comparative analysis of heating and cooling energy consumption is conducted between buildings with and without solar chimneys to assess the energy-saving potential. Furthermore, a life cycle assessment evaluates the environmental impacts of solar chimney construction and the environmental benefits during operation. It is revealed that the solar chimney can reduce building energy consumption. The greenhouse gas emissions associated with solar chimney construction can be offset within one year. The study presents an effect diagram illustrating the renovated building with a solar chimney. This study provides valuable insights into the application of solar chimneys in developing rural areas to enhance indoor comfort and promote energy savings. Additionally, it offers guidance for exploring optimal solar chimney configurations for specific geographical regions areas.

Theoretical models for predicting ventilation performance of vertical solar chimneys in tunnels

Solar chimney as a reliable renewable energy system has been primarily utilized for building ventilation, but its application in the tunnel is rarely explored. This study develops theoretical models to predict the ventilation performance of vertical solar chimney in urban tunnel. Five temperature distribution types within the chimney cavity are analyzed, including uniform, vertically linear, horizontally semi-parabolic, two piecewise semi-parabolic in the depth direction, and three-dimensional parabolic profiles. The theoretical models consider the effect of chimney configuration, tunnel geometry, glazing materials, and solar radiation intensity on airflow rate through solar chimney. Validation against experimental data and numerical simulation shows that considering three-dimensional temperature distributions results in an average 11 % deviation from validation data, outperforming assumptions of uniform (29.3 % deviation) or lower-dimensional profiles. The volumetric flow rate through solar chimney exponentially decreased with h/w and h/d that the optimum ratio of h/d is 10. The airflow rate linearly increased with 0.14 power of glazing absorptivity. This analysis provides technical guidance for optimizing solar chimney design in tunnels, enhancing natural ventilation, and reducing energy consumption for mechanical ventilation systems.

Theoretical analysis and numerical study of natural convection inside combined solar chimney

AbstractSolar chimneys may induce natural ventilation through solar radiation. However, sufficient theoretical studies are needed as a basis to fully exploit passive design in practical green building design. In this work, we investigate the heat transfer properties of turbulent natural convective flows in a combined solar chimney with a thermal flux at the absorption wall by means of theoretical analysis and numerical simulations. Two different flow patterns have been found, one with a clear thermal boundary layer flow pattern and the other without, based on high Rayleigh numbers. For flow development in these two flow regimes, the transient scaling analysis is performed separately and the control mechanism for each phase is presented. Some new scale relationships are established to characterize the ventilation performance of solar chimneys, including thermal boundary layer thickness δT, velocity vT, mass flow m, and so on. For the distinct thermal boundary layers, δT,s ~ HΓ2/5/Bo1/5κ2/5, vT,s ~ Bo2/5κ4/5Γ1/5/H, m ~ ρBo1/5κ2/5Γ3/5. For nonobvious thermal boundary layers, vT,f ~ Bo1/3κ/H2/3W1/3, m ~ ρBo1/3κ/A2/3. The important scale relationships are validated using corresponding numerical simulation data, such as the mass flow rate scale M ~ (Γ/κ)3/5Bo1/5 in the distinct thermal boundary layer flow state, and so on. The air changes per hour and heat exchange efficiencies are calculated for a solar chimney with a fixed height‐to‐width ratio to provide a basis for the design of a solar chimney.

Comparative Analysis of Solar Chimney Power Plant Chimney Design: Performance Evaluation and Material Cost Comparison

Abstract: This paper investigates different configurations of solar chimney design in a solar chimney power plant system. Mathematical analysis of the system has been done in Ansys software. The results of the maximum (inlet) velocity, pressure, efficiency, and temperature of the air are obtained for base type, convergent, divergent, sudden contraction, and sudden expansion types of chimneys. Furthermore, the electrical power output of Solar Chimney Power Plants has been determined for different chimney types. In this analysis, one Solar Chimney Power Plant (SCPP) with a solar collector diameter of 258 m and a chimney height of 197 meters and outlet diameter of 10 m has been taken as the basis. It has been found that sudden expansion and divergent types of chimneys give higher output power than the other types of chimneys. Also, while calculating the cost of materials of the different types of chimneys, it has been found that the sudden expansion type of chimneys is costing less than other types of chimneys. When power output was compared, it was found that the sudden expansion type of chimney gives higher output than other chimneys. Detailed simulation, testing, and analysis are necessary to consolidate the results.

Enhancement of Thermal Efficiency in Gas-Fired Heaters Through a Novel Double-Walled Chimney Design: Experimental and CFD Analysis

Enhancement of Thermal Efficiency in Gas-Fired Heaters Through a Novel Double-Walled Chimney Design: Experimental and CFD Analysis

Numerical Simulation of a Efficient Solar-Powered Ventilation System

The objective of this study is to conduct a numerical analysis of a small-scale solar ventilation-air conditioning system operating under the meteorological conditions of Bisha, Saudi Arabia. The primary objective of the proposed system is to provide sustainable and comfortable thermal conditions. To achieve this objective, the system recovers the heat wasted by the solar ventilation process and reuses it to power the desiccant dehumidification process. The solar chimney features a lateral (vertical) wall design, and a comparative performance investigation of two solar chimney designs (conventional vs original) is conducted. Mathematical models of the ventilated room and solar chimney are developed, and numerical simulations are carried out to evaluate the performance of each solar chimney design. The study aims to assess the ability of each design to maintain indoor thermal comfort through the analysis of air distribution temperature and air streamlines. The results of the performance comparison revealed that the proposed solar chimney design outperformed the conventional design in terms of thermal and ventilation performance. The proposed solar chimney design, with its lateral (vertical) wall, was also found to be more effective in maintaining indoor thermal comfort than the conventional design. The simulations showed that the proposed design produced a more uniform air distribution temperature within the ventilated room, resulting in improved comfort levels. Additionally, the proposed design was found to have a more efficient airflow pattern, with fewer areas of stagnant airflow. These results suggest that the proposed solar ventilation-air conditioning system has the potential to provide sustainable and comfortable thermal conditions in small-scale buildings.

Enhancing solar chimney performance in urban tunnels: Investigating the impact factors through experimental and theoretical model analysis

Efficient and sustainable ventilation in urban tunnels is crucial for combating air pollution and safeguarding human health. This study investigates the design factors impacting solar chimney performance in urban tunnels to optimize ventilation efficiency. Experimental trials analyzed the effects of blockage ratio, chimney height, and solar radiation on temperature distribution and ventilation rate. The results demonstrate that increased chimney height and solar radiation positively influence airflow velocity at the chimney outlet, enhancing ventilation. The temperature rise near absorber is higher than that closed to glazing wall. Temperature distribution within the chimney follows a distinctive horizontal two-piecewise semi-parabolic decay pattern, enabling accurate prediction of temperature profiles along the cavity depth. Novel analytical models predict temperature distribution, airflow velocity, and ventilation rate within the solar chimney system, aiding precise design and optimization. Remarkably, the blockage ratio has limited impact on ventilation rate, allowing for disregarding vehicle blockage effects in solar chimney design for urban tunnels. Matching chimney width to tunnel width and ensuring a relatively high chimney height are emphasized for optimal functionality. The study holds substantial implications for ventilation system design in urban environments, promoting healthier and more sustainable cities.

Computational fluid dynamics simulation and optimization of the fluid flow behaviour in a multi‐stage solar updraft tower using a new chimney design

AbstractThis work proposes a new chimney design that allows for the development of a multi‐stage solar updraft tower (SUT). The new design consists of two successive divergent chimneys. A 3D model was established to inspect the air flow behaviour within the SUT in six configurations: four multi‐stage systems with four divergence angles of the second stage were compared to the simple conventional SUT and the simple SUT with a divergent chimney. The new SUT performs better than the conventional one, while the two‐stage solar tower multiplied the system efficiency. Two high‐velocity zones appeared for the two‐stage SUT, whereas one zone occurred for the conventional system. The velocity in the two zones achieved a significant value, like that of the conventional system. In addition, the second stage's divergence angle directly impacts the velocity value inside the two stages. The static pressure distribution varies with the change in chimney design. The depression area occurs twice for the multi‐stage SUT in the inlet of each stage.

The Chimney Heat Potential to be Converted into Electrical Energy with Thermoelectric Generator: Dimensionless Analysis

The gas-steam power plant combines a gas power plant and a steam power plant, where Heat Recovery Steam Generator (HRSG) is a unit for generating steam. The waste heat from this system is channelled to the chimney with a Thermoelectric Generator (TEG) module to generate electrical energy. TEG uses the waste heat from the thermal conduction process from the chimney wall, where the height, diameter, and velocity variables are considered for analysis. To optimize this analysis, we used dimensional analysis to get a laboratory-scale system, and the method used the matrix dimensionless of the balance energy equation. As a result of the investigation, the calculation of chimney heat potential is obtained; the condition temperature will increase when velocity increases and the value of diameter and height decrease, then there is have an error about 14% from laboratory-scale design of chimney.

First analysis of a novel design of a solar chimney with absorber elements distributed in the air channel

The study of solar chimneys arouses great interest because of the wide variety of its applications, above all passive heating, cooling and ventilating of buildings. Mathematical models to predict the obtainable air flow rates and the conversion efficiency have been developed. Some studies focused on the possibility of increasing the amount of heat transferred to the air, and thus the efficiency, through an increase of the absorbing surface area inside the channel. The present work arises in this research line, and in this study a never investigated novel solar chimney configuration is proposed, with four arrays of cylindrical absorber elements in the air channel. Aim of this system is not only to increase the absorbing surface, but also the convection exchange coefficient between absorber surface and air, thus increasing thermal efficiency compared to a traditional system. A numerical model has been developed to investigate the proposed system, with an accurate approach to the radiative heat transfer exchanges, that have usually been rather neglected in previous studies. Convection heat transfer coefficient have been calculated and simulations have been conducted both in the hypothesis of natural and mixed convection. Head losses have also been taken into account. Thermal efficiency and air flow rate have been calculated for different values of the solar height. Results show that in the investigated configuration (a direct power equal to 669.1 W has been considered) the efficiency is always higher than in the traditional system, reaching values up to 61%. Moreover, efficiency value does not decrease as solar height increases, as it happens in the traditional system, where efficiency maximum value is 38% for a 10° solar altitude. Compared to the traditional system efficiency values, the proposed system values result increased, between a minimum of 47% at a solar altitude equal to 3 3° and a maximum of 128% at a solar altitude equal to 71°. Also airflow rates are higher, from a minimum of 7% to a maximum of 21% respectively for the solar altitude values of 33° and 71°. With reference to the average of the efficiency values (in the ten solar altitude values examined in the range 10°-71°), it has been verified that is 68% higher for the configuration with cylinders than for the traditional one. The average air flow rate is 11% higher.Also the power lost by the glass surface do not depend on solar height, and results much lower in the proposed system than in the traditional; the power loss due to the direct power on the inlet opening in the proposed system is lower than in the traditional system, especially for high solar altitudes, having a value up to 135 W, while in the traditional system it reaches 280 W. Moreover, the proposed system efficiency values in several cases results also higher than those found with solutions presented in other studies to increase the absorbing surface.Results therefore show considerable advantages in adopting a novel solar chimney system such as the one proposed in the present work, and its performance appears to be worthy of further investigation, focusing on convection mode and on the optimization of the arrangement of the cylinders (position, number of arrays,..) with respect to the solar height.

Effect of passive and active ventilation on malaria mosquito house entry and human comfort: an experimental study in rural Gambia.

Rural houses in sub-Saharan Africa are typically hot and allow malaria mosquitoes inside. We assessed whether passive or active ventilation can reduce house entry of malaria mosquitoes and cool a bedroom at night in rural Gambia. Two identical experimental houses were used: one ventilated and one unventilated (control). We evaluated the impact of (i) passive ventilation (solar chimney) and (ii) active ventilation (ceiling fan) on the number of mosquitoes collected indoors and environmental parameters (temperature, humidity, CO2, evaporation). Although the solar chimney did not reduce entry of Anopheles gambiae sensu lato, the ceiling fan reduced house entry by 91% compared with the control house. There were no differences in indoor nightly temperature, humidity or CO2 between intervention and control houses in either experiment. The solar chimney did not improve human comfort assessed using psychrometric analysis. While the ceiling fan improved human comfort pre-midnight, in the morning it was too cool compared with the control house, although this could be remedied through provision of blankets. Further improvements to the design of the solar chimney are needed. High air velocity in the ceiling fan house probably reduced mosquito house entry by preventing mosquito flight. Improved ventilation in houses may reduce malaria transmission.

A Novel Design of a Hybrid Solar Double-Chimney Power Plant for Generating Electricity and Distilled Water

The classical solar chimney offers passive electricity and water production at a low operating cost. However, the solar chimney suffers from high capital cost and low energy output density per construction area. The high capital investment increases the levelized cost of energy (LCOE), making the design less economically competitive versus other solar technologies. This work presents a new noteworthy solar chimney design for high energy density and maximizing water production. This was achieved by integrating a cooling tower with the solar chimney and optimizing the operating mood. The new design operated day and night as a hybrid solar double-chimney power plant (HSDCPP) for continuous electricity and water production. During the daytime, the HSDCPP operated as a cooling tower and solar chimney, while during the night, it operated as a cooling tower. The annual energy output from the cooling towers and solar chimney (i.e., the HSDCPP) totaled 1,457,423 kWh. The annual energy production from the cooling towers alone was 1,077,134 kWh, while the solar chimney produced 380,289 kWh. The annual energy production of the HSDCPP was ~3.83-fold greater than that of a traditional solar chimney (380,289 kWh). Furthermore, the HSDCPP produced 172,344 tons of fresh water per year, compared with zero tons in a traditional solar chimney. This led to lower overall capital expenditures maximizing energy production and lower LCOE.

Characterizing the induced flow through the cavity of a wall solar chimney under the effects of the opening heights

Using solar chimneys in buildings can enhance the thermal insulation of the building envelope and provide sufficient ventilation and cooling. The performance of a solar chimney is strongly affected by its configurational factors. This work examines the effects of the opening heights on the flow field in the cavity of a wall solar chimney with a Computational Fluid Dynamics (CFD) model. Both cases of equal and unequal opening areas were considered. The results show that the induced flow rate increases with the opening height and gradually becomes constant as the opening height is about 2.0–3.0 and 5.0–6.0 times the air gap for heating the left wall (HLW) and the right wall (HRW) of the air cavity, respectively. Particularly, using equal inlet and outlet heights that are equal to the air gap reduces the flow rate of 27% for HLW and 85% for HRW compared to the maximum ones. The optimal design of a wall solar chimney to achieve maximum flow rate is proposed for two cases of heating, that is, (a) for HLW, equal opening heights which are twice the air gap, and (b) for RHW, the inlet height equal to the air gap, and the outlet height equal to five times the air gap.

The Implication of Solar Chimney for Enhanced Stack Ventilation

In this study the effect of a solar chimney in enhancing the stack ventilation in an e-Bike Prototype Assembly building is analyzed. The Study area is Birgunj, Nepal. Natural ventilation in the existing plans is studied and compared with an alternate scenario of incorporating a solar chimney. Various parameters like temperature (Air, operative and radiant), pressure and velocity distribution, and comfort parameters (PPM and PPD) are compared. The DesignBuilder software is used to analyze natural ventilation. DesignBuilder internal CFD analysis is used to study the effect of solar chimney as a part of the building on the natural ventilation. Results show that there is significant improvement in ACH and air movement inside the building with incorporation of Solar Chimney. The PPD analysis results show that the comfort aspect is not only related to a single parameter like the air flow, temperature and pressure differential but a combination of these. The design of solar chimney should not only focus to improve a single aspect but a combination of the entire parameters for overall comfort. The study also shows that internal CFD analysis can be effectively used to predict internal condition of a building. The performance of Solar Chimney can be measured either or wholly in terms of air movement/air flow, temperature and velocity distribution and also thermal comfort parameters like PPD and PMV.

A novel staggered split absorber design for enhanced solar chimney performance

Solar chimney enables passive ventilation in green buildings, without drawing electricity from the grid. The factors influencing the performance of this sustainable passive ventilation device have been widely studied. However, more work needs to be done to increase the induced flow rate, which is crucial to enhance the attractiveness of this ventilation method. This study highlights the importance of high uniformity of outlet velocity distribution which can be achieved through distributed heating of the air in a solar chimney, leading to the staggered split absorber design proposed in this study. The flow rate induced by this novel solar chimney design is predicted numerically using an experimentally validated model and compared against the conventional solar chimney design. This novel absorber configuration results in higher flow uniformity at the chimney outlet and increases the ventilation rate by 57.0%, from 0.194 kg/s to 0.304 kg/s, for a solar chimney of 2.8 m in height, 1 m in width and 0.84 m in depth under 600 W/m2 solar irradiance.

Ventilating aged-care center based on solar chimney: Design and theoretical analysis

Natural ventilation is considered the first suggestion for COVID-19 prevention in buildings by the World Health Organization (WHO). Solar chimney’s viability in aged care centers or similar facilities was analyzed numerically and theoretically. A new solar chimney design was proposed to reduce the cross-infection risk of COVID-19 based on an airflow path through window, ceiling vent, attic, and then chimney cavity. Solar chimney performance, quantified by the natural ventilation rate, presented power function with window area, ceiling vent area, cavity height, and solar radiation. The ceiling vent is suggested to be closer to the corridor to enhance the performance and ventilation coverage of the room. A cavity gap of 1.0 m is recommended to balance the ventilation performance and construction cost. A theoretical model was also developed for aged care centers with multiple rooms and a joint attic. Its predictions obey reasonably well with the numerical results. Solar chimney’s viability in aged care center is confirmed as a 7.22 air change per hour (ACH) ventilation can be achieved even under a low solar radiation intensity of 200 W/m2, where its performance fulfills the minimal ventilation requirement (i.e., 6 ACH) suggested by the WHO for airborne infection isolation rooms. This study offers a new design and a guideline for the future implementation of solar chimney in aged care centers or similar facilities.

Analysis of solar chimney ventilation systems in high-rise residential buildings using parallel flow networks

Solar chimneys are passive ventilation systems that leverage solar energy to supplement or replace mechanical ventilation. Here we present a novel flow network analysis method for solar chimneys in high-rise buildings and use this method to develop insights into the design of these systems in high-rise multi-unit residential buildings (MURBs). The proposed method differs from others as it relies on a flow network that is less computationally intensive than computational fluid dynamics methods, but it can consider more complex system layouts than existing flow network methods, allowing for characterization of these systems in high-rise buildings. The method was validated by comparing results to other studies in the literature, showing that it can match the flow rates reported for single-floor systems within a 5% error, and qualitatively match the trends from studies of multi-floor systems. We use a case study to demonstrate how the model can be used to analyze the performance of a solar chimney in a high-rise MURB. The results indicate that the air flow rate to each floor induced by the solar chimney is proportional to collector width and solar flux, and inversely proportional to the inlet temperature and the number of floors. The method detailed in this study can be used by practitioners and researchers to develop simulation programs, and the case study results can be used to improve solar chimney design in high-rise MURBs.