Solar Chimney Effect Research Articles

Thermal analysis on porous evaporation composite wall integrated with solar chimney

This paper introduces a composite wall integrated with a solar chimney and a wet porous layer for evaporation cooling without consumption of electrical power, in which the airflow is driven by the buoyancy force from solar chimney effect, and water for evaporation on surface is supplied by capillary forces in wet porous layer. A numerical study on heat and mass transfer in composite wall was conducted to analyze the impact of environmental conditions and composite wall structure on cooling performance. More convection between airflow and surface of porous layer under higher solar irradiation, and larger evaporation on surface of wet porous layer under lower relative humidity benefits for cooling to be obtained. The 3.3 or 2.1 K smaller temperature of indoor surface of composite wall below ambient occurs at about 12:30 in a sunny day. The effective cooling and cooling efficiency are defined to be evaluated the cooling performances in composite wall. The solid matrix material, thickness and porosity of wet porous layer relating to its thermal resistance and thermal capacity, as well as channel width and window-to-wall ratio relating to effects of airflow amount and evaporation surface size influence effective cooling and cooling efficiency greatly. The higher cooling and lower cooling efficiency occur in case with thinner porous wall at initial stage, and the cooling efficiency increases in case with thicker porous wall with thickness above 0.1 m. The larger cooling and lower cooling efficiency occur in cases with smaller channel width or window-to-wall ratio. All these results should be taken into account for the utilization of the porous evaporation composite wall integrated with solar chimney.

Analysis of the Ventilation Performance of a Solar Chimney Coupled to an Outdoor Wind and Indoor Heat Source

The effects of different solar radiation intensities, heat flow density of indoor heat sources, outdoor wind speed, and the relative location of indoor heat sources on the natural ventilation performance of solar chimneys are investigated through three-dimensional numerical simulations. The mechanism of the mutual coupling of the solar chimney effect with the outdoor wind and indoor heat source heat plume is explored. The results of the study show that when the structural parameters of the solar chimney are the same, the heat flow density on the surface of the indoor heat source, the outdoor wind speed and the solar radiation intensity all have a gaining effect on the ventilation performance of the solar chimney and the effects of the three on the ventilation of the solar chimney promote each other, when the solar radiation intensity is 200 W/m2, the outdoor wind speed is 1.0 m/s, and the indoor heat source heat flow density increases from 0 to 1 500 W/m2, the solar chimney ventilation volume increases from 0.393 m3/s to 0.519 m3/s, the maximum value of the increase is 32.1%. In the other two cases, the maximum increase in solar chimney ventilation is 176.7% and 33.1%, respectively. Under the same conditions, solar chimney ventilation is optimal when the heat source is in the middle of the room. The presence of outdoor wind, however, affects the optimum design parameters of the solar chimney. Compared to the case where no outdoor wind is taken into account, the optimum inlet width of 0.2–0.3 m for the solar chimney no longer applies with outdoor wind, with the optimum value rising to 0.5 m.

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 Prototype Passive Solar Drying System: Exploitation of the Solar Chimney Effect for the Drying of Potato and Banana

Agricultural product drying is of great importance as it is a reliable method for fruit and vegetable preservation. Tackling the high energy consumption of the process will reduce the final product cost and mitigate greenhouse gas emissions. In this work, a passive drying method was experimentally evaluated. The method was based on the principle of the stack effect taking place in the solar chimney structure. Different types of solar chimneys in terms of dimensions and materials were evaluated for the drying of banana and potato slices. The results of the experiments showed that the drying rate was close to solar drying systems. Parameters such as height and material characteristics of drying tubes, as also weather conditions, influenced the drying rate. It was found that the banana and potato slices were dried at a satisfactory rate for almost 48 h during the summer period in Greece. From the parameters of the drying tubes that were varied, it was found that both the height and material played a major role, as did the air flow rate. With the increase in the drying tube by 1 m and with the choice of proper manufacturing material, an increase in the flow rate between 40% and 100% can be achieved. When only the color of two 3 m-high tubes changed, the flow rate varied between 4% and 15%. The proposed method has almost zero energy consumption, and it could be used as a standalone or as a part of a hybrid drying system. It can also be adjusted in existing greenhouse-type agricultural structures as a parallel operation system.

Investigation on the cooling performance of a buoyancy driven earth-air heat exchanger system and the impact on indoor thermal environment

The feasibility and cooling performance of a pure buoyancy-driven earth-air heat exchanger system (B-EAHE) with the assistance of combined effect of solar chimney and thermal mass were verified and revealed by a full-scale experimental study. The experimental results showed that the EAHE pipe diameter plays an important role in the system performance, and the airflow rates reach peak values of approximately 252 m3/h and 166 m3/h for the EAHE pipes with diameters of 0.3 m and 0.2 m, respectively. The air temperature differences between the inlet and outlet of the EAHE were approximately 12.5 °C and 13.0 °C in maximum, and 4.8 °C and 4.78 °C in average for the EAHE pipes with diameters of 0.2 and 0.3 m. In addition, the amplitude of indoor air temperature was further attenuated under the regulation of the B-EAHE system. The air temperature inside reference chamber varies from 28.3 to 35.1 °C, while the air temperature inside test chamber with 0.3 m diameter pipe ranges from 28.5 to 30 °C, which is approximately 2 °C lower than that for test chamber with 0.2 m diameter pipe. Moreover, higher energy saving potential is justified by the 0.3 m diameter pipe with peak cooling capacity of 1179 W compared with the 0.2 m diameter pipe with peak cooling capacity of 629 W. It is concluded that the B-EAHE system is able to achieve 24 h periodically fluctuating natural ventilation and passive cooling, and to improve the indoor thermal environment greatly in hot summer conditions.

Distributed heat absorption in a solar chimney to enhance ventilation

This study examined an innovative approach to enhancing solar chimney effect of using solar energy for building ventilation. Solar absorbing plates were inserted in a solar chimney to form a distributed heating flux among walls and insertions. Experiments using electrical heating to simulate the solar irradiation showed that adding two insertions increased the mass flow rate by 30%. The experimental data validated a computational fluid dynamics (CFD) model and two analytical models from the literature. Among these models, the plume model predicted the flow rate in the absence of insertions with reasonable accuracy, while the stratified model predicted the theoretical maximum flow rate instead of actual flow rate. The difference in flow rate between the two analytical models represents the potential for enhancement. The CFD simulations indicated that the insertion method could achieve approximately 70% of this potential. This represents a 57% increase in flow rate over the base case without insertions. This was achieved with 15 insertions. Adding more insertions was not advantageous because of the increase in friction. Insertions increase the uniformity of the heat distribution across the chimney channel and reduce the maximum temperature, resulting in a more uniform temperature distribution across the channel and, consequently, an increased buoyancy effect. However, two or three insertions are likely the most cost-effective in practice, as three insertions can realize majority (57%) of the potential enhancement. This study proves the concept of improving the efficiency of a solar chimney by adding transparent glazing insertions in the channel.

Measurement of the Green Façade Prototype in a Climate Chamber: Impact of Watering Regime on the Surface Temperatures

Green façades with an active water regime and the water flowing through the substrate itself are not common. This system reduces the temperatures and incorporates the evapotranspiration, which could be more effective than by the regular green façades. The use of a double-skin façade with a ventilated air cavity can reduce the heat load, but the evapotranspiration can reduce it even more with additional benefits. Green façades could also serve as a key element for reducing the surface temperatures of the insulated metal panels (IMP), which are mostly used as a façade system for production facilities or factories. In this paper, a prototype of a double-skin façade, which consisted of vegetation board from recycled materials and IMP, is tested in a climate chamber to evaluate the function and benefits of such a combination. The outdoor skin is made from board, the surface of which is covered by the rooted succulent plants. Measurement results are represented as a direct comparison of single sunny day surface temperatures with and without a double-skin (green) façade. The use of the green façade reduces the indoor surface temperature of IMP by 2.8 °C in this measurement. The use of water circulation through the outdoor skin reduces the temperature of the vegetation board by 28 °C. This could have a great impact on the microclimate around the façade. Because of the controlled environment and ventilation system in a climate chamber, it is not possible to investigate the airflow and solar chimney effect within the ventilated cavity. In addition, it is complicated to show the potential of microclimate change caused by the wet vegetation surface. For the mentioned reasons, the need to carry out “in situ” tests on a model wall under the real conditions was indicated.

Study on ventilation performance of inclined solar chimney coupled with indoor heat source

The study of ventilation air distribution of the building with built-in heat source and set inclined solar chimney is carried out through 3D numerical simulation. The synergistic effect of thermal plume formed by internal heat source and solar chimney effect is analyzed. The effects of different solar radiation intensity I, heat flow density W at the surface of the internal heat source and structural parameters (including the height of the internal heat source from the ground h and the mezzanine inlet spacing b) on the indoor natural ventilation performance of the building are investigated.

The Effect of Solar Chimney on the Thermal Performance of Hotel Room in Aswan, Upper Egypt

The Effect of Solar Chimney on the Thermal Performance of Hotel Room in Aswan, Upper Egypt

Effect of Solar Chimney and PCM cooling ceiling to the air flow inside a naturally-ventilated building

Computational fluid dynamics (CFD) gives significant contributions to building design fields. Building ventilation is the most common problem to simulate in CFD software. 2D and 3D simulation can be used to simulate cross ventilation within the building. ANSYS Fluent is commonly used CFD software, and it has been used in this study to assess the environment of an atrium building under buoyancy-driven natural ventilation and wind-driven natural ventilation. Buoyancy is one of the main forces driving flows. Buoyancy effect happened when the moving fluid is lighter or heavier than surrounding fluid. This paper will elaborate the use of ANSYS Fluent in assessment the environmental performance of a building. Some cases on a building were set in this study. The aim is to simulate accurately buoyancy-driven air flow inside a building for natural ventilation, visualize and analyse simulation results, provide architectural/engineering solution to natural ventilation of buildings. Cooler air appears from ceilings and creates cooling to the room down. Meanwhile, solar chimney generates wind flow across the building due to temperature differences within the chimney.

Effect of the Position of the Phase Change Material (PCM Na2CO3•10H2O) on the Solar Chimney Effect

To reduce the energy consumed by ventilation in a building is a critical task for the related researchers. Using the solar chimney effect to obtain the nature ventilation at day time is possible. Here a hybrid wall with PCM was provided, and the effect of the position of PCM in the hybrid wall on the solar chimney effect was studied. The thickness of PCM was 1cm, the air gap was 30cm and the power of the simulation solar light was 780W. The results show that when PCM was in front of absorber, the temperature of the air in the gap was higher than that of the air with a PCM behind the absorber. As for the air velocity in the gap, when the simulation solar light was turn on, the air velocity with PCM in front of the absorb was higher than that of the air with PCM behind the absorb. While when the simulation solar light was turn off, the air velocity with PCM in front of the absorb was lower than that of the air with PCM behind the absorber It is interesting to guide the construction of the hybrid wall.

J-54 ソーラーチムニーを用いたハイブリッド換気とGHPを用いた個別分散型空調を併用した学佼建築に関する研究 : (第1報)ソーラーチムニーの換気特性と省エネルギー効果

J-54 ソーラーチムニーを用いたハイブリッド換気とGHPを用いた個別分散型空調を併用した学佼建築に関する研究 : (第1報)ソーラーチムニーの換気特性と省エネルギー効果

Case Study of Trombe Wall Inducing Natural Ventilation through Cooled Basement Air to Meet Space Cooling Needs

AbstractUnderground spaces normally are at cooler air temperature than ambient air temperature because of earth-sheltered walls. This cooler air can be circulated to occupied spaces using a solar chimney effect to exhaust air from the basement to where it is needed. This work aims to study the viability of using natural ventilation induced by a Trombe wall to draw fresh air from underground basement floors for space cooling in the dry desert climate. Outdoor air is delivered to the basement through an earth tube. A numerical model integrating thermal models of the basement space and the occupied zone, and the Trombe wall is used to predict the air temperature variation with time in the occupied space air temperature and to predict thermal comfort. The feasibility of implementing the proposed system is assessed in a case study of a residence in the inland dry desert climate of Lebanon during the summer. It was found that the proposed system achieved thermally comfortable conditions at 80% acceptability for...

The Study on Numerical Simulation of Classrooms Using Hybrid Ventilation Under Different Solar Chimney Radiation

Based on the known geometric model of classrooms using hybrid ventilation with solar chimney, the solar radiation intensity of the solar chimney's effect on indoor air temperature and velocity is simulated and analyzed based on the Fluent software. Combined with the numerical simulation analysis, it can be seen that ventilation quantity increases with the increase of solar radiation and the variation of average temperature with a series of room heights under different solar radiation can be available. Study and Research on the solar chimney can provide the theoretical evidence for the ventilation effect of classrooms, however, a more accurate conclusion will be required for further study on the numerical simulation and experimental verification.

Simulating home cooling load reductions for a novel opaque roof solar chimney configuration

The roof solar chimney (RSC) is a low cost passive ventilation technique for reducing the energy consumption for cooling buildings. This study examines the performance and level of energy savings by simulating a detached home in four climates with RSC, cross-ventilation, and standard ventilation strategies. Each case was simulated in ESP-r for baseline and high efficiency construction, detached homes with a single story, three bedrooms, a 189m2 floor plan and high thermal mass constructions. Photovoltaic panels were integrated into the surface of the solar chimney on the South-facing roof to improve the RSC performance with their absorptive properties, and provide cooling to the reverse of the panels with the ventilation airflow. To form the RSC, a gap under the external layer of the roof allowed airflow from the interior of the house to a plenum in the peak of the attic with vents to the outside. Cross ventilation was aided with openings in the interior walls allowing flow between rooms. The ventilation gap was modeled by discretizing the RSC into 12 sections and calibrating the air-flow and convection coefficients with corresponding computational fluid dynamics models. The results indicate that the ventilated roof provides free cooling and natural ventilation in all climates and seasons tested. Flow was caused more by the stack effect rather than through natural convection and the solar chimney effect. Cross ventilation reduced cooling load by approximately 50% percent over the baseline, and the ventilated roof by up to another 80%. Either advanced natural ventilation approach reduced cooling load by more than the green envelope and efficiency practices in three of the four climates. The natural ventilation techniques were proportionally as effective in reducing load in a high efficiency home as in the base case home.

Thermal Analysis of the Domed Vernacular Houses of Harran, Turkey

Minimum energy consumption and economic efficiency using local and recyclable materials is essential for achieving sustainability, considering the depletion of global energy sources. The Anatolian Peninsula presents a diverse range of local building construction techniques accumulated over centuries, which meet the criteria mentioned above. Due to richness of climatic variety and the influence of many civilisations throughout history, Anatolian regions reflect this richness in their respective solutions to building construction. Built mainly out of brick and stone, mortared and plastered by mud, the domed vernacular houses of Harran, a small town in the province of Urfa in the hot arid climate of southeastern Anatolia, are one of the best examples that deserve attention with respect to minimum energy consumption. In this study, the thermal performance of the “Harran house” as a vernacular type was analysed. For this purpose, temperatures inside and outside a Harran house complex with relative humidity variations were measured. In addition, for investigating the domed houses’ thermal behaviour, temperature measurements at different surfaces and media were recorded. The solar chimney effect obtained from the dome and the importance of the thermal mass of the square base of the house were also evaluated. The study yielded results, which showed that the indoor conditions were within the limits for thermal comfort even under extreme summer conditions.

Double versus single skin facades in hot arid areas

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.

煉瓦の熱的特性と自然エネルギーを利用した室内熱環境制御システムの提案 : 自然エネルギーを利用した空気循環式煉瓦造住宅の開発研究 その1

This paper reports on test house measurements and simulated prediction for the proposed a low energy house with air-circulation in brick walls. Distribution of thermal mass, arrangement of heat gain/exhaust elements, combination of other devices and operation scheme control the indoor thermal environment and reduces of air-conditioning load. The first stage, the thermal performance of a brick house was simulated to compare with other types of wall structures, and it was possible to improve the thermal performance of a brick house with utilization of heat gain/exhaust elements. The next stage, a test house was constructed to validate experimentally the effect of proposed devices. Direct solar gain and Trombe wall effect are the object in winter in terms of heat gain. Earth cool tubes and solar chimney effect by Trombe wall are measured to estimate the cooling amount. We proposed a real size model house with air-circulation in brick walls combined with a solar air-heater, Trombe wall and cool tubes, and the thermal performance of it was simulated as the third part of this paper. Experimental results on the test house were used to validate the accuracy of the simulation programs. As for the seasonal heating/cooling load, the brick house with air-circulation was estimated about 20% less than a normal wooden structure house.