Guidelines for the solar chimney application : as a passive single and Integrated strategy for heating and cooling residential buildings in Aley – western mid-mountain climatic zone of Lebanon

Abstract

Solar Chimney (SC) is a passive design used to enhance natural ventilation and space conditioning in a building, limiting the energy requirement of the building to low operational costs. In Lebanon, high energy consumption of residential buildings is recorded mainly for heating and cooling, marking the highest consumption in the Western Mid Mountain (WMM) climatic zone. Thus, proposing the SC application for limiting this high thermal demand in residential buildings of the WMM zone for both heating and cooling would limit the total energy consumption. SC design has various types (Stand-alone SC application or coupled systems based on SC)and design configurations in terms of layout, materials and dimensions which vary according to the existing building conditions; in this thesis, the Literature review presents previous research studying the optimum performance of different SC types and the conditions for using each type. Three main building conditions are classified in the Literature as factors that significantly impact the choice of the SC type and configuration; for instance, the orientation, the height and the solar exposure. Through field survey and observation, the three conditions are analyzed within the selected study area in Aley; also, three scenarios composed of different existing conditions are categorized. Scenario 1 focuses on multi-floor buildings oriented towards the south with full solar exposure; scenario 2 represents multi-floor buildings oriented towards the south-western exposure and are shaded by a highly dense built environment, while Scenario 3 stands for multi-floor buildings oriented towards the west and located in a highly dense built-up area. By referring to the Literature review suggestions, two respective SC approaches (characterized by special design configurations, such as single and coupled SC-EAHX strategies) are proposed for each building scenario in a way that optimizes the solar absorption and respects the identified conditions. These SC approaches are assessed using building simulation tools: Revit for modeling the initial buildings and the proposed designs, Green Building Studio (GBS) for assessing the initial thermal demand and Computational Fluid Dynamics (CFD) for testing the indoor thermal performance of the buildings coupled with the proposed designs in each scenario. The results in these three scenarios demonstrate that the performance of the suggested coupled SC-EAHX approach is better than the stand-alone SC strategy. Energy saving for the coupled strategy is calculated using heat loss/ gain equations and heating capacity formulas; it also shows that the coupled strategy saves up to 37%, 33% and 26% of the initial thermal consumption in scenarios 1, 2 and 3 respectively. In addition, cost efficiency analysis is performed for the coupled system in the three scenarios and it expresses the success of the approach in all. Hence, coupled SC-EAHX approaches are recommended for the identified three existing scenarios in Aley and this thesis recommends special design configuration for each to attain optimum performance. Therefore, the three design configurations of the coupled system can be used for limiting the thermal energy consumptions in either existing or new buildings in Aley or any other region that shares the same climatic parameters and building conditions of any of the selected scenarios.