Tiêu đề The Green Side of Passive Cooling- Building Facades Inspired by Evapotranspiration in Trees_CATE 23.pdf ✅

Comfort At The Extremes 2023 Dec 13-14-15 | 2023 , Ahmedabad | India. 160Abstract ID, | The Green STitle of the paper. ide of Passive Cooling 1 of 8 Building Facades Inspired by Evapotranspiration in Trees The Green Side of Passive Cooling: Building Facades Inspired by Evapotranspiration in Trees Abstract. Buildings suffer from uncontrolled heat gain through their skin, which creates an urgent need for thermal comfort. In hot climates such as India, a growing economy with a rising per capita income is leading to an expected rise in cooling demand—by 11 times in the next two decades. The use of passive cooling strategies to reduce direct heat gain through building envelopes is an integral step in reducing the energy demand for cooling. The system works as a shading device similar to adjustable louvers, moreover, the terracotta’s porosity mimics cooling evapotranspiration. It adapts to sun angle, building orientation, and design. It combines terracotta and water to effectively cool, especially in multi-story buildings. The efficiency of the proposed passive cooling system was tested in the composite climatic regions of Raipur and Hyderabad, the nature-inspired passive cooling system reduced cooling energy needs by 30% and 47% respectively. The future of space cooling in buildings can benefit by using efficient passive cooling envelopes that can reduce the heat gain in the buildings. Climatically adaptive designs hold the potential to influence the shape of future buildings, landscapes, and cities, perhaps with earthy tones. Keywords. Envelope Cooling, Passive Cooling, Building Façade, Climate Responsive, Biomimicry 1. Introduction In India, a country experiencing hot climates, a growing economy with a rising per capita income is leading to an increased demand for cooling. Most of this demand is attributed to the construction industry as space cooling in buildings. According to the India Cooling Action Plan (ICAP), the cooling demand in the building sector is expected to rise by 11 times in the next two decades [9]. Using RACs for cooling our indoors is effectively heating up our outdoors. This leads to a further increase in demand for indoor cooling, what we can call the ‘cooling paradox.’ Navigating this demand effectively necessitates a well-balanced approach. This involves advocating for the adoption of energy-efficient cooling systems and integrating sustainable design practices that utilize passive cooling techniques for buildings. Building Envelopes, made of roofs and facades, face high heat and solar radiation. This causes thermal transmission that affects indoor spaces negatively in tropical regions where temperatures are already too hot [8] (p. (pp. 104-113). ACs are harmful to the environment and use a lot of energy. For instance, in Indian homes, ACs account for 20-40% of the electricity consumption [7]. Hence, it is important to lower the cooling energy consumption in buildings while maintaining thermal comfort. 1.1 Towards Alternative Cooling Techniques: Inspired by Nature, Guided by Tradition Traditionally in India, buildings were designed in consideration of the environmental context, using passive strategies that channel air and sun into the building interiors in a way that reduced heat gain and increased thermal comfort [13] (p. (pp. 1901-1911). According to ICAP, using building envelopes that suit the climate can reduce the cooling energy demand by 20% by 2037-38 [9]. The temperature under a tree is often 10-12° C lower than the surroundings [1] (p.(pp. 139-148). This difference in temperature is the combined result of the phenomenon of ventilation, shading, and evapotranspiration. The stomata regulate the exchange of CO2 and water between the plants and the atmosphere. A large amount of water evaporates from the canopy; a process that uses an equivalent amount of heat energy from the surrounding, thus cooling it.
Comfort At The Extremes 2023 Dec 13-14-15 | 2023 , Ahmedabad | India. 2 of 8 160 | The Green Side of Passive Cooling Building Façades Inspired by Evapotranspiration in Trees Figure 1 Lower Temperatures Below the Tree (source: Author) Passive cooling systems based on the principle of evapotranspiration can be very effective for providing thermal comfort in building interiors, especially in hot-and-dry climatic regions such as India. Such cooling systems can be realized as an additional ‘second skin’ that can also be attached to the existing building facade to provide thermal comfort through passive means. 1.2 Research Questions 1. Can building envelopes be inspired from the natural process of trees? What if buildings had a second skin that acts like the foliage of the tree? 2. What is the impact of such building envelopes on the Cooling Load of buildings? 3. What is the impact of such building envelopes on the Thermal Comfort of the occupants? 4. How can passive design strategies effectively reduce the energy demand for cooling in buildings in hot and dry regions like India? 5. How do these strategies and their performance differ as per different building typologies and project briefs? 2. Methods 2.1 Nature-Inspired Second Skin as Passive Cooling Systems The proposed solution is realized as a second skin facade, called the ‘Aerofoils’ made with an assembly of porous material modules.Water is circulated through this system which cools the passing air through the principle of evaporative cooling. Figure 2 Part plan of the system (source: Author) Each module in the system is designed in the shape of an aerofoil made of terracotta to imitate evapotranspiration of trees. It stores water which gradually evaporates through its surface to facilitate evaporative cooling as air flows between two modules. The aerofoil shape is assembled to create a nozzle effect that creates a pressure difference to allow better airflow. For a comprehensive evaluation of the passive design strategies, we have considered different cases, pertaining to different building typologies and project briefs. Two of those cases are described in this paper: the first is a residential project in Hyderabad, and the second is a commercial complex at Raipur, both in composite climate. The selection of these cases is based on the fact that they belong to a similar climatic classification, but have different in the project requirements and briefs, making them comparable. For Case 1 (Residence), the overall
Comfort At The Extremes 2023 Dec 13-14-15 | 2023 , Ahmedabad | India. 160Abstract ID, | The Green STitle of the paper. ide of Passive Cooling 3 of 8 Building Facades Inspired by Evapotranspiration in Trees building envelope (facades) was adapted to the climatic context using shading devices, and optimising material specifications. In the second case, variations were introduced in the passive cooling facade as there was a lack of flexibility in specialising other envelope mateirals. The evaluation parameters for both the cases considered overall temperature difference, energy consumption, and cost savings. Parameters specific to certain aspects of both cases were also evaluated: in the context of the Commercial Complex, performance in different scenarios- with ventilation, with evaporative cooling, with the shading only, etc. were considered to evaluate the monthly energy consumption and savings, carbon footprint and Energy Performance Index (EPI). Whereas, for the residential project, the paramount goal was to realise achieved thermal comfort of the spaces throughout the year. 2.2. Evaluation The studies are both located in regions where buildings pre-dominantly recieve maximum sun-exposure from the south and west facde; therefore the second skin is considered in these cardinal directions. 2.1.1. Case 1 | Residence in Hyderabad Project Type: Residential Location: Hyderabad, Telangana Climate: Composite [10] Built up Area: 2000 sqft. Facade orientation: Aerofoils proposed on West and South Facades Figure 3 Rendered View of the Hyderabad Residence Plotting the average diurnal variations against wet bulb depression in the region gives us the potential of evaporative cooling in the region. Figure 4 Evaporative Cooling Potential Upon close investigation, feasibility of evaporative cooling, as described in the image above, 33% of time of the year (approx. 2931 hours) passive cooling strategies such as Aerofoil facade have the potential to reduce the outdoor air by more than 5 ͦC. The analysis is primarily to evaluate the potential of façade based evaporative cooling for providing comfort in Naturally ventilated or Hybrid Air-conditioned modes of operation. Three scenarios are evaluated: 1. AC mode to assess peak cooling load performance. 2. Naturally ventilated with Evaporative cooling,
Comfort At The Extremes 2023 Dec 13-14-15 | 2023 , Ahmedabad | India. 4 of 8 160 | The Green Side of Passive Cooling Building Façades Inspired by Evapotranspiration in Trees 3. Evaporative Cooling. To model the evaporative effect of the fins the model is to mimic through an Indirect Evaporative Cooler. Secondary air stream was kept the same as Primary air stream. Primary Air flow rate was calculated through Heat Load assessment assuming an AC building running on 24°C setpoint. Heat load calculations made using simulations- ASHRAE Heat balance method. 2.1.2. Case 2 | Commercial Complex in Raipur Project Type: Commercial Location: Raipur, Chhattisgarh Climate : Composite [10] Building Floor Area: 2145 sq m Facade orientation: Aerofoils proposed on West and South Facades Figure 5 Rendered view of Commercial Complex in Raipur The performance of the aerofoil cooling facade system is assessed based on the following parameters: 1. Temperature Variation- between Indoors and Outdoors. 2. Cooling Load and Capital Cost savings- A lower temperature achieved through passive means translates to a reduced cooling demand. This reduces capital costs- an important factor considering the affordability of the system. 3. Building Energy Consumption- Reduced Cooling Load on buildings leads to a reduction in overall energy consumption in the building. 4. Energy Performance Index and Operational Savings. 5. Carbon Footprint- as annual and incremental savings in kgCO2e/kg 6. Water Consumption 2.3. Simulation For both the cases, assessment of the applied strategies was carried out by simplifying the building design in Rhino 3D and analysed with the use of Energyplus on Openstudio and Honeybee (Ladybug tools). 3. Results 3.1 Case 1 | Residence in Hyderabad The first set of assessments evaluated the impact of shading to reduce the Radiant and surface temperatures. “Fins Shading” indicates the effect using Aerofoil Cooling Facade. 3.1 Figures and Tables (11-pt Times New Roman, bold & italics)