Biao Wang

doi:10.19080/CERJ.2019.09.555767

Mini Review

High-Rise Building Integrated with Solar Chimney

Biao Wang*

Department of Architecture, North China University of Technology, China

Submission: November 20, 2019; Published: December 10, 2019

*Corresponding Author: Biao Wang, Department of Architecture, North China University of Technology, China

How to cite this article: Biao Wang. High-Rise Building Integrated with Solar Chimney. Civil Eng Res J. 2019; 9(4): 555767. DOI: 10.19080/CERJ.2019.09.555767

Abstract

In dense mega cities, high-rise buildings energy consumption on mechanical ventilation and overheat produced by the air conditioners are among big problems for the sustainable building development and green city construction. Solar chimney is proved to be an efficient method to promote natural ventilation for buildings. Different types of solar chimney are discussed with different high-rise building layout and floorplans. Solar chimney geometry and environment basic data can be evaluated to optimize its natural ventilation.

Mini Review

In hot and humid areas, people depend heavily on electricity-powered air conditioners to provide comfortable indoor temperature. The demand of electricity for air conditioning in dense cities in summer counts a big part for the building consumed energy and the heat generated by the air conditioners conversely make the city heat island effect more severe. In developed countries, the buildings sector is the final user of the biggest energy amount (35-45%) and more than half of that energy is due to thermal conditioning [1]. To meet the rise in electricity, demand more amount of fossil fuel needs to be burnt, which then increases its environmental footprint as well. Solar chimney (SC) is found as one of the efficient methods to heat and ventilate indoor air in the hot and humid areas as well as cold climate countries. It has attracted attention in recent years because of its ability to effectively drive natural ventilation. The main mechanism is like this: air enters the chimney at its lower level from the premises which are to be ventilated; solar radiation is absorbed by the main body of the chimney with high thermal storage opaque materials on surfaces or on inner wall with glass surfaces; the absorbed solar radiation then increases the air inside the chimney; as the air is heated, its density decreases, generating a natural ascending flow; when the air reaches the open top of the chimney then is evacuated outside [2]. There are currently many papers discussing SC in order to reduce the indoor temperatures using natural ventilation. As a reliable renewable energy system, SC has been largely utilized to conquer global energy crisis [3]. Maerefat & Haghighi [4] proposed a system that employed a SC along with an evaporative cooling cavity to cool the air, that was able to reduce room temperatures by 4-9 °C from the ambient. However, the humidity of the indoor air, increased to levels higher than ASHRAE recommended value of 65% relative humidity for occupied indoor spaces [5]. Due to the natural ventilation, a building in Japan with SC was found to reduce the fan shaft power requirement by about 50% in annual total, even up to 90% in January and February [6]. Inspired with the prototype of SC power plant built in Manzanares, Spain, a new type of building-integrated SC is introduced [7]. There a 11-story building was designed to integrate three types of SC: outside-wall SC, elevator shaft SC and atrium SC. The outside-wall SC which benefits from the neighboring staircase as an additional radiation collector and chimney, can run much better than the separated wall SC. Also, to make the SC function more effectively, every atrium space for different floors is connected as a whole, so all the small atria can better benefit from the SC ventilation effect.

Generally, many of the researchers on SC adopted physical experiments to evaluate the ventilation effect. Cheng et al. [8] introduced a SC platform with a dimension of 1.5 m × 1.5 m × 0.9 m to evaluate natural ventilation and smoke exhaustion, considering four influencing factors, including height of cavity inlet from the floor, cavity depth, solar radiation and fire size. Results show that external radiation shows obvious benefit on enhancing natural ventilation, while its influence on smoke exhaustion is limited. Ahmed and Hussein [9] made a hybrid SC with PV panels (348 cm*67cm*10cm) and studied two types of SC with different cover and absorber materials. The two types of SC are similar as show in while the thermal storage material is changed by PV panels. It is found that the system A (collector glass roof and a PV panel as an absorber) had higher thermal gain than system B (PV panel as collector roof cover and plywood as a base absorber) while the daily average of electrical power in system B was a little higher (6%). Zha et al. [10] have studied a SC of 6.2m length, 2.8m width and 0.35m air gap, the experimental results show that air flow rate of 70.6 m3/h ~1887.6 m3/h can be achieved during the daytime in the testing day. Results show that during the transition seasons (from April to October), SC can be used for saving energy with an energy saving rate around 14.5% in Shanghai. Some other researchers [11-13] investigated the thermal behavior of a SC with Phase Change Material (PCM). Ayadi et al. [14] have adopted the code Ansys-Fluent 17.0 to study different impact of five turbulence models on the distribution of the air flow characteristics. The work showed that the turbulence model types affect directly the numerical results. Asadi et al. [15] used Energy Plus software to simulate the performance of SC in different parts of a typical seven-story office building and studied the influence of the layout of SC. Neves and Silva [16] have studied a SC with wind tunnel experiments and computer simulations using Energy Plus. Results showed that the airflow rate and distribution pattern at the outlet openings of the SC are influenced by either the thermal gradients and, mainly, by the outdoor wind velocity and direction. Ghanbari and Rezazadeh [17] have applied a novel application of a giant chimney with the practical purpose of helping to ventilate and decrease the local air pollution in metropolises. Results show that a chimney with high altitude, working in low ambient temperature and unstable weather conditions, and in expanded cities near sea level will typically produce better performance.

Overall, most of the existing literature studied SC on its geometry, layout and outdoor environment (such as temperature, wind velocity and direction), based on a small-scale model (even a case model with 2 story high) or a numerical model. However, examples of high-rise building with SC are hardly found. As we know, high-rise buildings with their vast facades have a great potential to consume sustainable energies and therefore they can easily gain solar radiations. There are many famous buildings that are well designed to utilise solar radiation to promote natural ventilation, for example, the Frankfurt Commerzbank Tower and the Pinnacle Tower, which are separately analysed on the solar design aspects [18]. For many high-rise buildings in the metropolises, the vast facades can act as a great solar radiation gainer, which would be much potential to integrate SC.

On the other side, the materials for radiation absorber for the SC need to be selected. Most researchers use simple blackpainting concrete wall [16,19], dark porous materials [20] as heat-absorbing materials, while some others adopt PV panel [9]. In fact, micro-algae integrated panel can be a good choice. Cervera & Pioz [21] has introduced the micro-algae integrated panel for building envelop (window, wall and roof). Microalgae photo-bioreactor has advantages such as energy storage, Co2 absorber, sugar, protein and oxygen producer, etc [22]. In building integrated SC design, vast of facade and roof area can be used for this algae photo-bioreactor panels as the envelop glass and solar radiation absorber.

Conclusions

With consideration of other experiments results in the literature, wind flow in the buildings integrated SC may not strong enough to generate electricity, but efficient natural ventilation is generally obvious, especially for high-rise buildings as they offer higher air-pressure variance and bigger solar radiation receiver surface. Three types of SC, namely outside-wall SC, elevator shaft SC and atrium SC, can be integrated with high-rise buildings. For better promoting and evaluating natural ventilation in high-rise buildings, parametric study with CFD simulation and physical experiments are proposed.