Çok katlı binalarda doğal havalandırma farklı analiz araçları ve örnek alan entegrasyonu ile planlama için bir yöntem

Natural ventilation of buildings has the potential to significantly reduce energy consumption related to cooling and fanning. This can be achieved by (i) providing good indoor air quality without any electricity demand and (ii) improving thermal comfort in the summer through increased daytime airspeed and high night ventilation rates. In high-rise office buildings, however, natural ventilation is still not a widely preferred means of ventilation. The main reason is the lack of information on the required system design. There are neither standards nor tools and instrument that support planners in the design of natural ventilation systems. Evaluation tools and instruments that are usually applied for effective vent sizing during preliminary planning are not suitable for complex flow path design. Only few results, if any, are available on the performance of naturally ventilated high-rise office buildings, especially where energy conservation is considered. In addition, a passive cooling approach can rely not only on intense natural ventilation but also on the reduction of heat gains, and on night cold storage systems. Considering these aspects together, there is a definitive need for research on the flow path design taking vent sizing for the provision of good indoor air quality and thermal comfort into account.. The current thesis is predicated on the above mentioned research gap. Towards this end, the thesis sets out to explore the concept of natural ventilation with focus on office buildings as a major application area. Emphasis is laid on the cooling potential of natural ventilation. The existing barriers for practically implementing passive technologies can be lowered by creating a quantifiable framework that accounts for all the relevant input parameters in the design process. In order to reach this goal, a planning and simulation approach is developed for the required system design, and the functionality is subsequently evaluated. The results of simulations are compared to those of a reference case-study. The 28-floor Kanyon high-rise office tower, situated in Istanbul, Turkey, is selected to demonstrate the applicability as it is considered to be a representative, state-of-the art building. From the energy metering, it is concluded that mechanical cooling and ventilation result in significant electricity consumption. Detailed information on the building and its operation has been made available by the building management. In addition to the primary case-study, a comparative assessment of the impact of three different moderate climate locations, viz., Istanbul, Turin and Stuttgart, is systematically analysed. The primary objectives of the thesis can be stated as (i) the development of a design approach, and (ii) the investigation of the feasibility of the proposed design, based on an existing case-study building virtually adapted specifically for this purpose. The approach is developed in three steps, including (i) conceptual design considerations with focus on the architectural consequences on the building type of concern, (ii) the original development of a preliminary design tool based on electrical circuit analogies for sizing the natural ventilation system, and (iii) a more detailed design development based on annual building energy performance simulations including custom ventilation control. In the first step, an architectural concept is developed for passive cooling in wide-shaped high-rise buildings where it is impossible to realise simple cross ventilation or single-sided ventilation. During the conceptual design process several challenges emerged. Conceptual adaptations addressing the flow path design are (i) a central chimney strategy in respect to the building width, (ii) isolated, modular segments, as each can then be treated as a medium-rise building and (iii) opposed, wind adapting openings to guarantee the intended flow direction and to maximise the wind pressure differences. Other solutions proposed for passive cooling are (iv) improved external shading devices (v) activation of the structural mass for night-time ventilation. In the second step of the design approach, the originally developed 'HighVent' planning tool is introduced with the aim to determine the design air change rate and system sizes necessary for climate specific summer design days. Simple electrical circuit analogies, for both ventilation and thermal models, are found to be suitable in supporting the passive system planning. As it is concluded that the classic design day conditions for mechanical plant sizing are too strict for passive cooling system design, meaningful design boundary conditions are provided. Openings can be sized automatically by the inverse solver method including an optimization process. For the Kanyon building, the pressure distribution is deduced from wind tunnel measurements. The program first calculates the flow-path design for a given airflow rate with unchanging boundary conditions. These values are then provided to the thermal module, which calculates the dynamic thermal comfort. The procedure is then repeated till the system size is sufficient for passive cooling. The tool outputs include advice if certain adaptive thermal comfort criteria can be reached for a summer design day. In the third step, the annual performance is exemplarily modelled with EnergyPlus building energy performance simulations including airflow networks. This includes the 'HighVent' tool preliminary ventilation design outputs, further 'post-processed' as model inputs, the conceptual adaptations made for improved shading and thermal mass activation, and the remaining features of the as-built Kanyon building in accordance with the data provided by the building management. It allows the users to perform sensitivity analysis for the investigation of the impact of specific parameters. The custom ventilation control dynamically targets to achieve (i) good indoor air quality according to EN 13779, and (ii) stay within adaptive comfort limits category II according to EN 15251. Annual thermal comfort is the most crucial indicator for evaluating passive cooling concepts, and is therefore proposed for final decision making. As the volume of a building is an expensive resource, the designer needs to do a weighting between the expected comfort and the size of the natural ventilation system. The applicability of the '3-step' design approach is then further evaluated by comparing the fully mechanical operated as-built Kanyon building with an operation based on passive and the hybrid control. The assessment is carried out with the help of performance indicators, and the results are intended to assist decision making in the design phase. Indicators proposed to evaluate the functionality are the energy consumption compared to that of mechanical ventilation and cooling systems, and compliance with the thermal comfort limits; additional aspects are the ventilation rates and the indoor air quality reached. A significant result of this comparative study is that control over the openings is crucial for all the scenarios when it comes to natural ventilation applications; otherwise ventilation rates can get too high and the office rooms tend to cool down way too much even during summer. It is shown that the 'adaptive temperature amplifier' control algorithm developed is more robust than simplistic controls. Furthermore, simulation results indicate that properly designed and controlled natural ventilation shows a good functionality and the comfort limits are rarely exceeded. However, differences in climate among geographical regions have a varying impact on the simulation results. For example, in the climate of Stuttgart, further adaptations to the preliminary design of the 'HighVent' tool or hybrid cooling are not necessary, whereas in Istanbul adaptations might be reasonable. However, to satisfy the comfort expectations in Turin, there is a necessity for further passive design adaptations or a hybrid cooling concept. That humidity values meet comfort expectations must be discussed and accepted by all project stakeholders, else a hybrid operation approach might be a good alternative. Nonetheless, in all controlled scenarios, high indoor air quality is achieved. To systematically study the possible energy conservation while maintaining thermal comfort, the energy consumption of identical buildings with different variants (passive/hybrid/active) is compared and benchmarked against the as-built scenario. Results show that the primary energy input for the Kanyon office-tower building can be reduced by approximately 30% to 40% for passive operation and by 28% to 34% for hybrid operation. For passive cooling including controlled natural ventilation, there is even no energy consumption for cooling and ventilation required, while energy usage for pump operation is limited only to the heating season. The hybrid strategies are found to be capable of exploiting the biggest share of passive cooling and ventilation energy conservation by providing a maximum operative temperature limit of 26 °C. This verifies the initial assumption that energy conservation of purely passively cooled and ventilated office spaces is significant, especially when compared to highly energy consuming state-of-the-art office towers. The results of this research work are intended, on the one hand, to support building planners in better understanding and implementing passive cooling measures and, on the other hand, to contribute to further development of sustainable building practices.