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In this paper, a combined solar chimney and water wall is proposed to provide ventilation as well as moderate heating to an attached room. A transient heat balance model (THBM) is established to predict the thermal performance of the combined system under mild winter conditions in Sydney, Australia. The effects of the glass panel thickness, air gap width, water column thickness, surface tinting and the relative position of solar chimney and water wall are studied respectively. The results show that the combined solar chimney and water wall is capable of providing ventilation throughout the day and night while maintaining the warmth level of the room even though it continuously draws fresh air from the ambient into the room. It is found that increasing the glass panel thickness or reducing the water column thickness enhances the thermal performance of the combined system by increasing both the room temperature and the ventilation rate. On the other hand, increasing the air gap width helps to increase the ventilation rate, but will cause the room temperature to decrease. In addition, between the two configurations, one with the water wall in front of the solar chimney (referred to as the WW-SC configuration) and the other with the solar chimney in front of the water wall (referred to as the SC-WW configuration), the ventilation rate and room temperature obtained with the SC-WW configuration are higher, and thus the latter configuration is more favorable. Furthermore, it is found that surface tinting generally degrades the thermal performance of the proposed system.

The solar chimney is one concept explored by building engineers and designers for reducing heat gain and inducing natural cooling in both commercial and residential buildings. In this sense, scientists around the world have developed significant research on solar chimneys since the 1990s. This review presents the studies related to the numerical thermal modeling of both, conventional solar chimneys and solar chimneys with phase change materials (PCM). The article focuses on two research areas: Computational Fluid Dynamics (CFD) and Global Energy Balance (GEB). Based on the literature, the CFD approach has become a powerful tool to investigate several aspects concerning the heat transfer mechanisms in a solar chimney. Additionally, the analysis of the literature showed that few calculation tools based on CFD transient state models of solar chimneys are available because the computational time required to solve these models could be excessive and impractical. Therefore, the use of high-performance computing (HPC) will be necessary to continue using CFD. On the contrary, the GEB models predict the transient behavior of these systems in short times, and one can integrate them in Building Energy Simulation programs. However, the literature about the solar chimney modeling using GEB shows that the transient mathematical model with PCM (six research papers) has been less used than the steady-state model. In general, results of a solar chimney using a PCM show that the temperature variation of PCM and air in the chimney were available for the natural ventilation in evening and night periods. Finally, this review paper is a reference for future research into the field of solar chimneys with a PCM and its applications.

The overuse of fossil fuels has become a major challenge in recent decades. Since mechanical ventilation systems are responsible for the largest proportion of the energy usage in the buildings, this study aims to come up with a green initiative for resolving the dire consequences of energy consumption. Here, for the first time, we work on an approach in which we aim to assess and enhance the evaporative cooling rate of a passive method during a summer day in a multi-story building in a hot and dry climate. In this regard, the windcatcher is coupled with three solar chimneys, and a water spray system (WSS) is located at the entrance of the windcatcher to decrease the temperature and raise the humidity of the air entering each floor. A combination of wind-catcher, solar chimney, and water spray system is adopted to provide natural air circulation in the absence of wind. Indeed, we employ Radiation, Turbulent, and Discrete Phase Models to simulate the proposed system by CFD. The effect of different variables such as temperature, droplet diameter, and thermal comfort factors are studied. Temperature, velocity, and other airflow profiles are analyzed using ANSYS FLUENT software. The study highlighted that adding WSS leads to a roughly 6-12 ˚C reduction in the temperature; moreover, relative humidity will rise by 80% on the third floor. Accordingly, adding WSS can improve the system’s efficiency and satisfy the thermal comfort conditions in the absence of wind.

Solar chimney has been primarily utilized for natural ventilation, but its application to smoke exhaustion was rarely explored. A 1:3 reduced-scale test platform with a dimension of 1.5 m × 1.5 m × 0.9 m (height) was used to optimize solar chimney under natural ventilation and smoke exhaustion, considering four influencing factors, including height of cavity inlet from the floor (0.2–0.8 m), cavity depth (2.5–17.5 cm), solar radiation (400–1200 W/m2) and fire size (6.8–15.8 kW). Both natural ventilation and smoke exhaustion follow the same trend along the air inlet height and cavity depth, which confirms its viability on smoke exhaustion under fire condition without compromising the performance of natural ventilation. Experimental results suggested a chimney configuration of 0.5 m high air inlet and 12.5 cm cavity depth with optimized functions. External radiation shows obvious benefit on enhancing natural ventilation, while its influence on smoke exhaustion is limited. An empirical model was developed to predict the flow rate under normal and fire conditions. The outcomes of this study provide a technical guidance for the design of solar chimney under scenarios of both natural ventilation and smoke exhaustion.

The electric power production using solar chimney power plant is directly related to the velocity value along the chimney. In this work, the effect of the chimney configuration on the solar chimney power plant performance was investigated. A series of numerical simulations were conducted to simulate the turbulent flow. An experimental setup was developed in Tunisia to carry out several measurements. The comparison between the numerical and the experimental results showed a good agreement. The study focused on studying the solar chimney power plants with: standard, divergent, convergent and opposing chimney. The velocity fields, the static pressure, the magnitude velocity and the temperature distribution were presented and discussed. The results revealed that the chimney form affects the air velocity behavior. The maximum velocity emerges with divergent configuration. However, the others configurations adjust the maximum velocity location, in the chimney center for the opposing configuration, and in the chimney top for the convergent configuration. This variation is due to the static pressure distribution affected the chimney configuration change.

The Roof Top Solar Chimney system is a natural solar updraft technique utilizing the solar energy to generate wind stream within the system passage that has enough driving force to create stack effect. The influence of the inlet shape of the solar air collector on the solar chimney performance was investigated experimentally and numerically in the present paper. Four different inlet configurations have been modeled and ANSYS FLUENT software was used to simulate and visualize the 2-D aero-thermal flow field surrounding the inlet region. Experimental measurements of the four different inlets were conducted using a roof top solar chimney set up to validate the simulation results and to evaluate and compare the system performance at each inlet configuration. The experimental model has two identical transparent covers installed over the roof of a room model, opened at the top to allow air flow from both sides to a chimney pipe. It was found that when the inlet has vertical cross section, it offered the best performance as the velocity and mass flow rate of the air at the chimney was observed to be higher compared with the other three inlet configurations. When the inlet cross section was employed as horizontal, the performance of the collector was reduced by 84% compared to the vertical inlet setting, at 1.00pm. The CFD analysis demonstrated, interestingly, that most of the air flow in the collector was directed from upper region above the inlet, while small amount is flowing from the bottom side of the inlet. This justify the reason of very low performance of air solar collector with horizontal orientation. The results revealed the possibility of reducing the area of the transparent canopy of the solar chimney power plant and convert the outer region to open top absorber.

In this paper, the performance of solar chimney as a natural convection solar air heater with longitudinal rectangular fins is numerically investigated. Heat transfer and turbulent flow in a three-dimensional domain are investigated under steady state condition and the finite volume method is used to discretize the equations. Numerical results are verified by comparing with existing experimental results in the literature and a good agreement is achieved. Effects of rectangular fins on air temperature and mass flow are discussed and the results are compared with that of a flat absorber. Furthermore, ambient temperature, solar radiation intensity and geometry parameters of the channel and rectangular fins such as depth of the channel, depth, and width of fins are checked. By analyzing the results, appropriate channel dimensions are suggested to yield better performance in the solar chimney. Finally, discontinuous fins in the solar chimney with different interruption gaps are examined. Utilizing discontinuous fins with appropriate interruption gaps may enhance the performance of solar chimney in comparison with continuous fins.

Cooling load accounts for more than 70% of the electric energy used in buildings in the Middle East. This paper presents a passive method to reduce the cooling load in buildings. The proposed concept includes adding an external solar shield enclosing an air gap between it and the outer wall of the building. This external solar shield layer would absorb the solar radiation incident on the outer walls of the building and get heated inducing a convective airflow in the gap between the layer and the building. This is an example of solar chimney in a flat geometry with a superficial resemblance to Trombe wall. Conventional Trombe wall channel heats the building external wall and creates a convective flow in-between a transparent glass layer and the heated wall. This hot flow is used either as a warm inlet air to the building in winter or help inducing airflow from inside the building for ventilation in summer. However, in the present work, the solar chimney induced airflow is purely external to the building. The proposed external solar shield starts with a glass layer from outside followed by an opaque porous metallic layer followed by an air channel before the building outer walls. The absorbing porous layer would get heated up quickly and transfer its heat to the air in the gap effectively due to its large surface area. The porous layer thickness is optimized at 15 cm while the air gap is optimized at 0.3 m. Numerical simulations based on finite volume analysis using ANSYS Fluent were carried out for a wall of 3 m height. Comparisons of the performance of buildings with its outer walls shielded by white painted, black painted and glazed walls are presented and discussed with respect to that of buildings with bared outer walls as a control. Putting glazing alone after an air gap, expectedly, increases the heat gained by 47–56% compared to 0.7 emissivity simple bared wall. Single black and white solar shielding walls reduce the heat gain by 30 and 67%, respectively. However, the proposed design of a solar chimney with a glass outer wall followed by a porous foam metal layer on its inner surface, reduced thermal gain by 67–79%. This results in electrical cooling load reduction by about 28%. Furthermore, the heated airflow induced by a solar chimney formed with a 20 × 3 m south wall can be utilized to induce water evaporation of 625–1046 kg/day allowing active evaporative cooling and/or water desalination under solar irradiation condition of Dhahran, Saudi Arabia

Cooling of buildings is an essential target for engineers and builders in the hot arid climate of Egypt. Performance of inclined solar chimney with passive cooling tower (SCPC) was studied. The system was integrated into a single room built in Assiut University (El-Gorib site) in Assiut, Egypt. Testing of indoor environment for the room with passive cooling was done during August and September 2015. A passive cooling technique was integrated inside a short wind tower made from expanded paper (wet pad) 0.1 m thick. A water tube was installed on the top of the expanded paper with small nozzles. Water is recirculated through the system using water pump. A reduction of room indoor temperature was observed with the integrated system (SCPC). There is a significant reduction of indoor temperature between 6 and 7 K due to passive cooling with surface temperature 19.4 °C for the cooling pad. The relative humidity did not exceed 57% most of the time. The maximum air speed inside the solar chimney was 3.5 m/s under the effect of a high solar radiation of 890 W/m2. The findings show that SCPC system achieves comfortable thermal conditions with a significant improvement in building energy conservation. The result of development this new cooling system helps to develop building code for low energy houses in Egypt and propose a new system to be integrated in the housing project of people with low income.

The purpose of this paper is to investigate the performance of solar chimney used for natural ventilation of closed enclosure in order to save energy. To achieve this purpose, a mathematical model simulating the performance of solar chimney was developed. The geometrical and operational parameters were considered. These parameters include: incident solar radiation, wind speed, ambient temperature and the dimensions of the solar chimney height, gap and width. Moreover, different chimney cover material were examined. A computer program was developed to solve the governing energy and conservation equations simultaneously. The model results were compared with available published data. There was a good agreement between the present results and the published data. The present study considered the performance of a solar chimney under specified meteorological conditions at Cairo. The results showed that the air change rate per hour (ACH) was s ignificantly depended on the wind speed as well as the dimensions (height, gap and width). The chimney gap, wind speed influenced largely the air flow rate. The effect of chimney height was not significant enough to be cost effective. The results showed that the air change rate per hour (ACH) throughout the year was more than the desired ventilation standards in enclosure space. Using materials other than glass to construct the outside cover of the chimney achieved a higher flow rate than the standards air change rate per hour (ACH). In addition, both the reduction in construction cost and safety are achieved.

The solar chimney power plant (SCPP) is a promising solution to produce electrical power from solar energy. The optimization of the solar setup geometry is required to enhance its performance. In this paper, a numerical study is presented to evaluate the performance of the solar chimney power plants while varying the collector roof angle. The considered system is defined by the collector height equal to h = 50 mm, the chimney diameter equal to d = 160 mm, the collector diameter equal to D = 2750 mm and the chimney height equal to H = 3000 mm. Four collector roof angles, equal to β = −1.5°, β = −1°, β = 0° and β = 1°, were investigated. For each collector roof angle, the distribution of the magnitude velocity, the air temperature, the pressure, the incident radiation and the turbulence characteristics were presented and discussed. The efficient choice of the optimal geometry is based on the calculation of the maximum value of the air velocity within the SCPP. Results indicate that a negative collector-roof positively increases the air velocity. The obtained results present an interesting data which can provide the thermal characteristics of the air flow for the designers and the engineers to improve the overall efficiency of the solar setup.

This study investigates the performance of an evaporatively-cooled window driven by solar chimney attached to external facades for providing acceptable thermal comfort at low energy consumption in an office space. A validated simplified model of the novel system was coupled with a developed 3-D computational fluid dynamics (CFD) model of the office space to predict the space window outer surface temperature. The CFD model was then coupled with a validated bio-heat model that was integrated with Zhang model to predict local and overall thermal sensation and comfort. Two representative hours were selected mainly 14 h and 17 h for hot and dry climate conditions for a space located in Riyadh. The reported results showed significant improvement in overall thermal comfort when the novel system is used to reach a thermal comfort level of 1.42 at 14 h and 1.96 at 17 h using a comfort scale varying from very uncomfortable at −4 to very comfortable at +4. Energy savings reaching 10% were recorded during both hours.

Increasingly, passive ventilation solutions are receiving considerable attention for inducing natural ventilation in dwellings regarding operation costs, energy demands, and carbon dioxide emissions. Solar chimney, in particular, is a promising alternative to enhance thermal and ventilation performance for the indoor environment by using convection of air heated by passive solar energy. The present study focuses on achieving optimum natural ventilation rate by incorporating solar chimney into a single room in a hot climatic context. Specifically, a mathematical model is developed through an overall energy balance on the solar chimney. This model examines a wide range of geometry parameters under real weather data to determine the optimum design solutions for the solar chimney. Furthermore, the model predicts the temperatures of the glazing and the black painted absorber as well as air velocity exiting from the chimney. The analytical results showed that an optimum air flow rate of 0.019–0.033 m3/s was achieved by 88.2% during the daytime when the dimensions of a proposed solar chimney are 45° inclination angle, 1.4 m length, 0.6 m width and 0.20 m air gab. Moreover, Computational Fluid Dynamics (CFD) was applied to predict space flow pattern using CFD module in DesignBuilder software, which is based on Energy-Plus dynamic simulation engine. The renormalization group (RNG) k-e turbulence model was applied to solving the mass and energy equations within the solar chimney. Comparisons of the model predictions with CFD calculations and bibliographic experimental work outline the validity of the model.

Solar energy is considered alternative crucial to fulfilling the increasing of energy requirements. Passive cooling systems are considered alternatives to mechanical ventilation systems. In this work, a highlight for a solar chimney with water heater and Phase Change Material is applied as a passive solar technique for cooling building integrated with short wind tower for low energy building in the hot arid climate. This paper aims to investigate the performance of new passive air condition system with the solar chimney and solar water heater as a full system for cooling air and heating water to be applied during day and night time based on the improvement of the solar chimney in Assiut climate, Egypt. Measurements, for air temperatures and surface temperature of the aluminium and air velocity inside the chimney, water temperature and room temperature were conducted with different solar radiations to evaluate the panel performance and room thermal comfort. The findings show a minimum airflow rate in the chimney after sunset equal to 0.69 kg/s to provide fresh cold air during a hot day with a water temperature equal 58 °C and 40 °C during 2 pm and after sunset respectively. Also, integration of solar chimney and PCM with cooling wind tower achieves a significant reduction for room air temperature between 8 and 4 k during day and night time respectively and the condition within the comfort range of Predicted Mean Vote (PMV) especially night time. The results provided information to integrate this new low energy compact passive air cooling and water heating system for the housing projects of the upper floor in a hot arid climate in Egypt.

A general model is developed for solar chimneys with the use of a plume of constant thickness representing thermal boundary and the use of a momentum equation in the plume. A set of correlations between the plume thickness and the channel Reynolds number, defined by the plume velocity and channel hydraulic diameter, are proposed. There was a reasonable agreement between the model and 15 measured datasets in the range of Reynolds number from 17 to 23,151 and Rayleigh number at the half of the chimney height from 4.5 4 × 109 to 2.12 × 1014. The correlations show that the channel free convection is a mixed flow of free convection (dependent on Ra) and a forced channel flow (dependent on Rech). The critical Rayleigh number at the half of the chimney height and the critical Reynolds number are consistent with those of natural free convection and forced channel flow, respectively. The plume model with the proposed correlations can serve as a general model for predicting the mass flow rates of vertical, square-channeled solar chimney systems with connecting ducts.

Design of solar chimney in buildings is considered as one of the passive ventilation methods enhancing the ventilation for adjacent spaces through renewable energy of sun and applying chimney effect phenomenon in an air canal. The layout of solar chimney in different parts of the building affects the ventilation rate and performance of solar chimney due to its effect on air flow rate. This research examines the performance of solar chimney based on its layout in southern, west-southern and east-southern part of the building. Then, the performance of solar chimney is compared in the plan center and southern facade-connect part. To achieve these objectives, EnergyPlus software was used to simulate the performance of solar chimney connected to a typical seven-story office building located in Isfahan. The results were presented in terms of two parameters including building layout and materials of the walls and glasses. The results show that locating solar chimney in east-southern part of the building provides maximum ventilation rate due to the maximum radiation and two side absorbing wall. It was also found that every solar chimney provides necessary ventilation rate for spaces attached to it.

Solar chimney has been widely used in industry for solar heating and cooling and in power generation. Their effectiveness can further be increased for building heating/cooling applications if used along with energy storage. However, achieving good heat transfer between energy storage material and air is still a challenge. Several studies have been made on improving the heat transfer by using thermal conductivity enhancers (TCEs). However, no study provides comprehensive analysis on their complex and non-stationary heat transfer characteristics. This paper focuses on the influences of thermal conductivity enhancers (TCEs) on heat transfer performance inside the phase change material (PCM) during the melting and solidification processes for solar chimney application. Four types of TCEs namely vertical fin (VF), horizontal fin (HF), honeycomb structure (HCS) and square cell structure (SCS) have been used in the study. The experimental results show that the VF, HF, HCS and SCS reduce the melting time by 8%, 12%, 14.5% and 16%, respectively compared to the pure PCM sample. It is also being found that the VF and HF with the same volume fraction have different effects on the heat transfer inside the PCM during the melting process proving that the geometry and distribution of fins are very important for the heat transfer enhancement.

The significant energy use and increasing requirement for good indoor environment quality in the built environment have led to a renewed interest in natural ventilation strategies such as windcatchers. Windcatcher is a roof-mounted device that supplies fresh airflow into a room and expels polluted air under the action of wind pressure and buoyancy forces. The aim of this review is to investigate factors which affect the natural ventilation performance of windcatcher including internal factors (related to geometry/design of windcatcher), external building features (microclimate) and surrounding environment (macroclimate) plus the impact of integration with other passive systems. From reviewing the literature, it was found that windcatcher with a square cross-section and curved roof demonstrates better ventilation in the room compared to other configurations. Moreover, the overall findings indicated that the integration of windcatcher with other natural ventilation systems such as solar chimney and wing wall has a considerable effect on the ventilation efficiency. In urban environments, buildings are often located quite close to each other, and the effect of surrounding structures on airflow profile cannot be ignored but only a limited number of works considered the impact of urban environment and objects (upstream or downstream) on the ventilation efficiency of windcatcher. Finally, the impact of vegetation, techno-economic cost and energy saving in a building are some significant gaps of current studies.

This study presents the world-first design of solar chimney for a real building considering both energy-saving and fire safety. Typical designing factors on both functions were investigated by a numerical tool after it was validated by experiments. It was obtained that solar chimney can be adopted for both functions with 7.42 air changes per hour natural ventilation under normal conditions and at least 6.52 times extension of available safe egress time for occupants under typical fire conditions. It was also known that the previously obtained optimized cavity gap of 0.2–0.3 m is no longer applicable for a big space, where the optimum gap is 1.2 m considering both functions for a big space. A consistency coefficient is also proposed here that a positive consistency coefficient means the increased parameter can enhance the performance of both functions, while a negative coefficient represents the performance enhancement of one function will compromise the other. The consistency coefficient of those designing parameters are: cavity gap (30.91) > air supply area through top vent (12.47) > air supply area through bottom door (5.4) > cavity height (3.09) > 0 > solar radiation (-0.47) > cavity height below the roof (-40.04). The parameters with negative consistency such as cavity height below the roof should be considered carefully when both functions are planned.

A Solar Chimney (SC) is a passive system harnessing solar energy to ventilate inner spaces and improve occupants’ thermal comfort. The purpose of this study is to determine the time periods of a year most suitable for the use of a SC in terms of thermal comfort under the different climates of Bandar-Abbas (hot and humid), Yazd (hot and arid), Paris (mild and humid) and Toronto (cold and humid). To this aim, a thermosyphonic model – validated against published experimental data – was employed for running dynamic thermal simulations of a residential building using the EnergyPlus software. The optimal time periods of operation of the SC, driven by the values of the Predicted Mean Vote (PMV) between −0.7 and +0.7 and Predicted Percentage of Dissatisfied (PPD) below 15%, are found to be November and January to April in Bandar-Abbas (2265 h), while for the city of Yazd it comprises the months of April and May together with September and October (2145 h). As for Paris and Toronto, the period spans from June to August, for a total of 1065 and 1620 h respectively. Correlation coefficients disclosing the impact of the increased air mass flow rate revealed a positive impact everywhere during nighttime in terms of indoor air temperatures (from 0.02 in Bandar-Abbas to 0.77 in Yazd). On the other hand, the impact on indoor relative humidity is always negatively correlated, with a peak of −0.73 in Yazd. Year-long comfort conditions are finally displayed in psychometric charts against ASHRAE 55 Standard boundaries.

Theoretical analysis was carried out to develop an unsteady-state model for displacement ventilation in buildings with solar chimneys and fans. The influence of solar radiation intensity and the height of the solar chimney on the interface height, reduced gravity and natural ventilation rate was analyzed, as well as the mechanical ventilation rate and the area ratio of the openings. It was found that the interface height and airflow rate increased significantly with solar radiation intensity and the height of the solar chimney for a relatively smaller time scale ratio, but reduced gravity increased significantly for a larger time scale ratio. When the mechanical force assisted the thermal force, the increasing mechanical ventilation rate and area ratio increased the interface height and total ventilation rate, but decreased the natural ventilation rate in hybrid ventilation.

This paper presents an experimental study of a new designed Trombe wall in combination with solar chimney and water spraying system in a test room under Yazd (Iran) desert climate. The Trombe wall area is 50% of that of the southern wall of the building that occupies less space and reduces the implementation costs. The new design of the channel has caused the absorber to receive the solar radiation from three directions. Based on the results, the optimum mass flow rate and the nozzle diameter of the water spraying system has been obtained 10 l/h and 30 μm, respectively. The results indicate that the water spraying system decreases indoor temperature and increases indoor relative humidity by about 8 °C and 17%, respectively. The most effect of outdoor relative humidity variation is on indoor relative humidity, rather than indoor temperature. When outdoor temperature increases, both indoor relative humidity and the difference between indoor and outdoor relative humidity decreases. The results also showed that the stored energy of the Trombe wall plays important role in the air ventilation during non-sunny periods. Lastly, the water spraying system enhances thermal efficiency by approximately 30%.

An experimentally validated numerical model is developed to study the effects of seven design and operational parameters on the heating performance of a solar chimney incorporated with phase change material (PCM) in this paper. It is found that when the latent heat increases from 70 to 170 kJ/kg, the melting time is increased by 103% and freezing time is prolonged by 60%. If heat flux is increased by 33%, the melting time is reduced by 36.4%. Increasing thermal conductivity of the insulation material from 0.02 to 0.06 W/m K, the melting time is prolonged by 47.2%. When absorptivity of the absorber is increased from 0.8 to 1.0, the melting time is decreased by 26.3%. When transmissivity of the glass cover is increased by 25%, the melting time is reduced by 26.7%. For the inlet air temperature, when it decreases from 25 to 15 °C, the freezing time is shortened by 39%. The melting time is only reduced by 8% when thermal conductivity of the absorber is increased by 25 times. Therefore, it can be concluded that the first six parameters have more impact on the system's performance while the thermal conductivity of absorber slightly impacts it.

A model for time dependent analysis of solar chimneys is presented. The energy balance equations for three components of solar chimneys, absorbing plate, cover glass and air-gap are discretized with respect to time using an implicit finite difference model. The discretized nonlinear energy balance equations are solved for numerous time steps over a 24-h period using the Newton–Raphson method. The time dependent solar irradiation is determined using the clear sky model. The model's performances for various parameters of solar chimney that affect the thermal mass of the absorbing plate are tested. It was determined that a solar chimney with a relatively large thermal-mass produces airflow well into night and early morning when no solar irradiance is present. Also, a high thermal mass of the absorbing plate results in smaller variations in the airflow rate. The results of the present model for a solar chimney with no thermal storage compare well with the previously published data.

This paper reports a numerical investigation of the buoyancy induced turbulent air flow in an inclined passive wall solar chimney (IPWSC) attached to a room (ventilated space) for ventilation applications over a range of controlling parameters. The standard k − ɛ turbulence model has been employed to model air turbulence in the solar chimney system. With an isoflux heating condition specified on the absorber wall, the ventilation performance of the IPWSC design has been examined over the Rayleigh number range of 1.36 × 10 13 ≤ Ra ≤ 1.36 × 10 16 and inclination angles from 0 to 6. The present numerical result shows that the turbulent kinetic energy and turbulent intensity in the solar chimney decrease with the increase of the inclination of the passive wall. The effectiveness of the IPWSC design for enhancing the thermally driven ventilation has been confirmed. Additional simulations have been carried out with a standalone solar chimney model. The result shows that the standalone model over-predicts the mass flow rate compared to that predicted by the attached model. The average difference in the predicted mass flow rates between the standalone model and the attached model with inclination angles from 0 to 6 at a representative Rayleigh number of Ra = 1.36 × 10 14 is around 10%.

The thermal behaviors of a solar chimney incorporating with organic phase change material (PCM) RT-42 unit under different heat fluxes are studied in this paper. For the numerical model, effective heat capacity method is employed to analyze the performance of RT-42, while the average thermo-physical property approach is used to describe the PCM/fins component. The PCM behaviors during its melting and solidification processes, absorber surface temperature, mass flow rate, and inlet and outlet air temperature difference have been investigated. The numerical results give good agreements with the experimental results. The comprehensive investigations under various heat fluxes from 100 to 800 W/m 2 are carried out by using the verified model. The numerical results show that the performance of the system deteriorates sharply once the heat flux is or lower than 500 W/m 2 , but not big improvement if the heat flux is higher than 700 W/m 2 . Therefore, the performance of the system is highly dependent on the solar radiation. The application of high effective thermal conductivity enhancers can further improve the performance of the chimney under lower solar radiation.

Determination of the roof top solar chimney behaviour during the day time is essential for the proper designing and sizing. This paper presents a mathematical model and analysis of an inclined type roof top solar chimney. The thermal energy and fluid flow processes were simulated mathematically based on the energy and mass balances. The model was converted to a MATLAB computer program and solved by iteration method. The analysis was carried out at various collector areas (15, 150, and 600 m 2 ) and various chimney heights (5, 10, and 15 m). The model was validated by comparing the results with the experimental measurements. The developed mathematical model was able to predict the dynamic behaviour of the system. The results demonstrated that the performance of the system is highly influenced by the solar intensity. The system becomes functional for space ventilation when the solar intensity is higher than 400 W/m 2 with a 15 m 2 collector area and 5 m chimney height, under Malaysia and similar weather conditions. As the wind speed increases from 1.5 to 6 m/s, it contributes to reduce the system performance by 25% at solar intensity of 900 W/m 2 .

The method Passive Cooling Load Ratio (PCLR) is an innovative simplified method which calculates the monthly cooling energy needs of a thermal zone where passive cooling systems are installed using the variables: cooling energy load and passive cooling potential. This new method is based on the Solar Load Ratio (SLR) that was previously developed for solar heating systems. Although, PCLR was theoretically developed for any passive cooling system, here it is applied to passive cooling based on ventilation strategies. In addition, this paper presents its application to an office room ventilation using: (i) forced cooled air from an earth-to-air heat exchanger (EAHE) and (ii) natural induced air by a solar chimney from the EAHE. Correlations were obtained for those systems, using the parameters that describe the local climate, the system type and its dimensions. The numerical model used to obtain the correlation functions when one of the systems is installed, associates previously developed numerical models with 5R1C model of ISO 13790. However, the PCLR method can be used to accurately estimate the cooling energy needs without using complex models for simulation. The error for all systems does not overcomes 5.2%, which is an acceptable variation for a simplified method.

The scope of this work was to investigate the summer ventilation performance of three high thermal inertia solar thermosyphonic configurations, used as night natural ventilation systems. The aim was to assess the effectiveness of each configuration and orientation on night natural ventilation. Three designs, (a) SC1 a conventional SC, (b) SC2 a thermal chimney with duct attached behind the absorber, and (c) SC3 a thermal chimney rectangular duct with two surfaces glazed. Thermal performance of each SC was investigated by simulations in EnergyPlus followed by a Sensitivity Analysis performed on predicted results. For calibration and validation, output variables were checked and verified for coherence against published experimental data of similar nature found in literature. Analysis disclosed SC2 facing West the most effective design. Simulation results showed that a concrete thermal chimney 3 m tall with 0.1 m wall thickness and 0.2 m air gap exhibited night cooling capacity, depending on configuration and orientation, was found ranging from 3.27 MJ/m-day for the SC1 faced South, up to 10.0 MJ/m-day and 14.7 MJ/m-day for the SC3 and SC2 facing West, respectively. SC2 faced West was predicted to deliver flow rate 98% higher than the flow rate of a same size conventional SC1 faced South.

The considered Zero Energy Building is a three-story building located in Singapore which was recently retrofitted in 2009 with a range of green features. A solar chimney system was constructed to enhance the air ventilation within the interior spaces using a series of solar assisted ducts that linked the lower floor classrooms and upper floor hall. The mechanism of the solar chimney system is explained in detail and experiments conducted separated the classroom into experimental and reference regions of similar volumes. Results showed that the solar chimney system is operating well in the hot and humid tropics, including cooler days. Furthermore, the presence of the solar chimney system effectively caused the interior air speed of the experimental region to reach a maximum of 0.49 m/s and the interior air temperature to heat up slower and cool down faster by 1–2 h as compared to the reference region. Lastly, the position of the solar chimney's inlet within the classroom was found to be significant; lowering it to occupancy's height of 1.20 m increased the interior air speed to a maximum of 0.60 m/s.

Integrating passive systems such as cross and stack ventilation, a solar chimney, a wind tower or an earth-air tunnel into a building envelope has the potential to significantly reduce the ventilation and air-conditioning demand on buildings. However the application of combination of these features in low rise contemporary buildings is limited. Among the major reasons, is the lack of simple building modelling techniques preventing effective integrated passive systems. Existing coupled multi-zone airflow and thermal modelling software such as COMIS-TRNSYS, CONTAM-TRNSYS or TRNFLOW do not include the passive airflow components which require simultaneous prediction of temperature and airflow rate in the components such as solar chimneys and wind-induced earth-air tunnels. This paper develops an integrated model incorporating these passive airflow components into a coupled multi-zone ventilation and building thermal model. The model is validated against COMIS-TRNSYS software for a lightweight building with large openings. The prediction of each passive airflow component is validated with available published analytical and experimental findings. The solar chimney model is able to predict reverse flow and accurately predicts the air temperature in the chimney. The earth air tunnel (EAT) considers the transient heating up effect of the soil during operation and predicts the outlet air temperature. Refereed/Peer-reviewed

Heat transfer process and fluid flow in a solar chimney used for natural ventilation are investigated numerically and experimentally her in. Solar chimney was designed, manufactured and tested by selecting different positions of air entrance namely: bottom entrance, side entrance, and both side and bottom entrances. The effect of integrating the chimney with paraffin (phase change material) on its thermal behavior has been also investigated. CFD analysis based on finite volume method is used to predict the thermal performance, and fluid flow in two-dimensional solar chimney under unsteady state condition, to identify the effect of different parameters such as solar radiation, and inclination angle. Experimental results show that a solar chimney with side entrance gives better thermal performance; also integrating solar chimney with PCM extended the ventilation period after the sunset. A comparison between the numerical and the experimental results shows fair agreement.

The solar chimney is a passive cooling technique to enhance the natural ventilation of buildings. The effect is, however, limited under hot and humid climatic conditions. In the study, the solar chimney was accompanied by a dew-point evaporative cooler. The dew-point evaporative cooler was integrated with the ceiling of a building. The air flow induced by the solar chimney was predicted by simulation, and the cooling effect of the dew-point evaporative cooler was also analyzed by heat and mass transfer simulation. The results showed that the system was capable of coping with internal heat gains of an ordinary office building. In addition, the optimal geometry of the evaporative cooling channel was revealed.

Two computational domains have been used for simulation of buoyancy-driven natural ventilation in vertical cavities for different total heat fluxes and wall heat distributions. Results were compared between cavities with horizontal and vertical inlets. The predicted ventilation rate and heat transfer coefficient have been found to depend on the domain size and inlet position as well as the cavity size and heat distribution ratio. The difference in the predicted ventilation rate or heat transfer coefficient using two domains is generally larger for wider cavities with asymmetrical heating and is also larger for ventilation cavities with a horizontal inlet than those with a vertical inlet. The difference in the heat transfer coefficient is generally less than that in the ventilation rate. In addition, a ventilation cavity with symmetrical heating has a higher ventilation rate but generally lower heat transfer coefficient than does an asymmetrically heated cavity. A computational domain larger than the physical size should be used for accurate prediction of the flow rate and heat transfer in ventilation cavities or naturally ventilated buildings with large openings, particularly with multiple inlets and outlets. This is demonstrated with two examples for natural ventilation of buildings.

The low energy approach should be the key concept in any long-term strategy aiming to build sustainability. For Madrid climate, action should be taken to reduce energy demand for heating and cooling in residential buildings. The performance of a passive cooling system was developed as a part of design work for the project of a low cost residential building. The passive cooling systems incorporate a solar chimney and precool the air by using the sanitary area of the building. The natural ventilation is enhanced with the help of the solar chimney and fresh air is cooled down by circulation within the sanitary area. The application of this system to the living rooms of a low cost residential building was evaluated and implemented. This cooling system incorporated to a residential building is the third prototype developed since 1991 by the designers. A model was developed to allow to predict the temperature of the air in the living room. The performance of the passive cooling system was evaluated based on the energy balance for a typical summer day. To reduce the energy demand in winter, a new design and window orientation has been developed and evaluated using DOE-2 simulation tool. The building has been constructed and monitored during 2006–2007.

The solar chimney is a simple and practical idea that is applied to enhance space natural ventilation. The chimney could be vertical or inclined. The chimney inclination angle is an important parameter that greatly affects space flow pattern and ventilation rate. In the present study, the effect of chimney inclination angle on air change per hour and indoor flow pattern was numerically and analytically investigated. A numerical simulation using Ansys, a FEM-based code, was used to predict flow pattern. Then the results were compared with published experimental measurements. A FORTRAN program was developed to iteratively solve the mathematical model that was obtained through an overall energy balance on the solar chimney. The analytical results showed that an optimum air flow rate value was achieved when the chimney inclination is between 45° and 70° for latitude of 28.4°. The numerically predicted flow pattern inside the space supports this finding. Moreover, in the present study a correlation to predict the air change per hour was developed. The correlation was tested within a solar intensity greater than or equal to 500 W/m2, and chimney width from 0.1 m to 0.35 m for different inclination angles with acceptable values.

The performance of the double-skin facade depends closely on the chosen ventilation means within its intermediate space. The modes of ventilation could be natural (buoyancy driven), forced (mechanically driven) or mixed (both natural and forced). Oesterle et al. has attempted to classify the double-skin constructions into four different types, namely box window facade, shaft-box facade, corridor facade and multi-story facade. A number of interesting investigations and findings are reported in the literature pertaining to passive ventilation in buildings and the thermal performance of double-skin facades. The researches have revealed close link between natural ventilation design and the function of double-skin facade. Most of them are using the idea of stack effect or the solar chimney concept and found that passive ventilation in summer is possible even for multi-storey buildings. It was found that significant energy saving is possible if natural ventilation could be exploited through the use of double-skin facade. In this research, CFD was used to analyse various thermal comfort parameters with different double facade configurations to determine a new type of double-skin facade configurations which will provide a better indoor thermal comfort in the hot and humid climate through natural ventilation strategies for the high-rise buildings.

Double skin facades are defined as two layers of facade separated by an air gap, that varies in its depth creating a solar chimney effect where warm air rises by buoyancy. As a facade technology, its thermal and daylight performance is still under scientific scrutiny. The bulk of research on the performance of this facade configuration is carried out in moderate climates. However, little is understood about the performance of double skin facade configurations in extreme hot arid climates. This investigation adopts an analytical approach using a dynamic simulation software (IESVE), to convert general intuitions on the performance of a double skin facade, in hot arid areas, into the grounds of understanding its performance based on research. It is an opportunity to study this facade configuration before the technology is transferred into construction in hot arid areas. In this paper, a comparative analysis of cooling loads on a single skin base case is compared against three possible changes to the physical properties of the external layer of the double skin facade. A dynamic thermal performance software APACHE-Sim is used (integrated environmental solutions IESVE, version 5.1). Simulation results indicate that a reflective double skin facade can achieve better energy savings than a single skin with reflective glazing.

Double-skin roof is known as a very effective way to reduce both the conduction and convection heat transfers from roof to the ceiling of building, on the other hand, RBS (radiant barrier system) is very effective in blocking the radiation heat transfer between roof and ceiling. In this study, prototypical double roofs inspired by the concepts of both double-skin structure and RBS technique was specifically designed to cut down the solar heat gain from roof. The effect of energy saving was experimentally measured. A double roof structure, formed by a roof plate and an aluminum foil-PP (polypropylene) board-RC slab, can achieve good performance of heat barrier and is highly recommended.

The solar chimney concept used for improving room natural ventilation was analytically and numerically studied. The study considered some geometrical parameters such as chimney inlet size and width, which are believed to have a significant effect on space ventilation. The numerical analysis was intended to predict the flow pattern in the room as well as in the chimney. This would help optimizing design parameters. The results were compared with available published experimental and theoretical data. There was an acceptable trend match between the present analytical results and the published data for the room air change per hour, ACH. Further, it was noticed that the chimney width has a more significant effect on ACH compared to the chimney inlet size. The results showed that the absorber average temperature could be correlated to the intensity as: (Tw = 3.51I0.461) with an accepted range of approximation error. In addition the average air exit velocity was found to vary with the intensity as (νex = 0.013I0.4).

This paper reports on an experimental investigation into heat transfer and mass flow in thermosyphoning air heaters, such as solar chimneys and Trombe Walls. The test rig comprised a vertical open-ended channel with closed sides, resembling a solar collector or solar chimney approximately 1 m2. Close control of the heat input was achieved by using an electrical heating mat—steady-state heat inputs ranged from 200 to 1000 W, and the channel depth was varied between 20 and 110 mm. Temperatures were recorded throughout the test rig, as was the air velocity. The principal results from the data showed: • The mass flow rate through the channel was a function of both the heat input and the channel depth: m ∝ Q i 0.572 and m ∝ s 0.712 • The thermal efficiency of the system (as a solar collector) was a function of the heat input, and not dependent on the channel depth: η ∝ Q i 0.298 Correlations are given in dimensionless forms.

Effect of inclination of absorber on the airflow rate has been investigated in a solar induced ventilation system using Roof Solar Chimney (RSC) concept. During summer months, due to the higher altitude of sun, absorber at small inclination with the horizontal plane captures more solar radiation, but suffers with reduction in the stack height. Results of the developed solution show that optimum absorber inclination varies from 40° to 60° depending upon the latitude of place. At Jaipur (India) 45° is found to be optimum for obtaining maximum rate of ventilation. At this inclination, the rate of ventilation is about 10% higher as compared to 60° and 30° inclinations. Experimental investigations show good agreement with the theoretical results. Roof Solar chimney of this size can easily be mounted on residential buildings for enhancing natural ventilation.

A passive night cooling system was developed and implemented for a new project of social housing. The passive cooling system incorporates a solar chimney in combination with high thermal mass in the building construction. The natural ventilation is enhanced with the help of the solar chimney and night fresh air cools the building structure. The design of this concept was calculated by balancing energy using basic thermal equations for a summer reference day and evaluated using two simulation tools, TRNSYS and TAS. The building has been constructed and actually in process of monitoring.

Solar heated open cavities including solar chimneys and double facades were studied for enhancing natural ventilation of buildings. A commercial CFD package was used to predict buoyant air flow and flow rates in the cavities. The CFD model was validated against measured data from the literature and good agreement between the prediction and measurement was achieved. The effect of the cavity width of solar chimneys and double facades on the buoyancy-induced ventilation rate was investigated. It was found that there existed an optimum cavity width for maximising the buoyancy-induced flow rate and the optimum width was between 0.55 and 0.6 m for a solar chimney of 6 m high. The ventilation rate in a double facade of four-storeys high generally increased with cavity width but decreased with floor level from bottom to top. Integration of photovoltaics into a double facade increased the ventilation rate while reducing its variation from floor to floor.

Double-skin facade is getting more and more attention as it provides many possibilities for energy conservation and at the same time creates good indoor environment. In this paper, natural ventilation performance of a double-skin facade is highlighted. A prototype building is proposed, which is thought to be an eight-storey office building with an atrium space in the north side. The south facade of the building is a double-skin facade and a thermal storage space called solar chimney is considered above the double-skin space. Actually, the double-skin space is connected with the chimney channel. Reduced scale model experiments and computational fluid dynamics (CFD) analysis are carried out in this research to evaluate the natural ventilation performance of the prototype building.

The study investigated the performance of solar chimney, which is integrated into a one-story building. A module was developed for and implemented in the Energy Plus program for the simulation and determination of the energy impact of thermal chimneys. The basic concepts, assumptions, and algorithms are implemented into the Energy Plus program to predict the performance of a solar chimney. The results showed that in Nanjing 45° is found to be optimum for obtaining maximum rate of ventilation and the rate of ventilation increases with increase of the ratio between height of absorber and gap between glass and absorber. This finding is in agreement with experimental results.

An improved heat dissipation system for buildings’ air conditioning, based on a previous prototype, has been developed and tested. It acts as an extended solar driven cooling tower, reducing service water temperature. The paper presents the physical basis of the system, the geometrical modifications of the new prototype, the mathematical model and the performed tests. Experimental results obtained during summer 2000 in a full-scale prototype showed that the cooling power capacity of this model is about 50% greater than that of the preliminary model. For each square meter of Hydrosolar Roof, more than 400 W of heat released can be reached under common operating conditions. Correlations of the system thermal performance have been obtained as functions of solar radiation, wind velocity and ambient conditions, allowing the design of system for actual buildings’ applications.

The aim of this research was to investigate, experimentally, both the feasibility of a solar chimney to reduce heat gain in a house by inducing natural ventilation and the effect of openings (door, window and inlet of solar chimney) on the ventilation rate. The study was conducted using a single-room school house of approximately 25 m 3 volume. The southern wall was composed of three different solar chimney configurations of 2 m 2 each, whereas, the roof southern side included two similar units of 1.5 m 2 each of another solar chimney configuration. Those configurations were built by using common construction materials. Experimental observations indicated that when the solar chimney ventilation system was in use, room temperature was near that of the ambient air, indicating a good ability of the solar chimney to reduce house's heat gain and ensuring thermal comfort. The air change rate varied between 8–15. Opening the window and door is less efficient than using solar chimneys, as temperature difference between room and ambient was higher than that obtained with solar chimneys.

In a solar-heated chimney, used to promote air movement within a building, stored heat is the main source for warming air within the chimney. This creates a buoyancy pressure which draws air through the building. It is therefore important to study the effect of the orientation upon the amount of heat that can be collected by the chimney for better performance. A theoretical study was conducted using a finite difference technique which showed that the amount of heat that can be collected by a solar chimney is strongly dependent upon its azimuth.

The performance of a single family residential solar house with three different window systems is presented. Of these three systems, two are window sunspace systems that operate as a heating component in winter and as a solar chimney for summer ventilation. The first window sunspace system is a small, local one and operates like a Trombe wall. However, contrary to a Trombe wall, the system presented here allows the penetration of daylight like any window. This window system can easily be used in small apartment buildings, where extra area for full-scale sunspace is not available. The second window sunspace system is a large central one and is designed between two tilted roofs. The heat collected by this sunspace is driven down into the living area by forced convection. The central window sunspace system collects sufficient amount of energy to heat the floor, which is shaded by the neighbouring building to its south. Such a situation is frequently encountered in low-rise high density areas. The realized solution can generally be applied to such areas. Evaluation of the expected performance of the building was carried out during the design process by means of a detailed simulation model. Comparisons between actual measurements during the first year occupancy and the simulation model are presented.