Green Buildings to Net-Zero Buildings: Using Autodesk CFD

DR. MUNIRAJULU: Hello, everyone. Welcome to this session about Green Buildings to Net Zero Buildings with a focus on use of Autodesk CFD Simulation. We will go through how Autodesk CFD Simulation is implemented in the design of air conditioning system for a high-rise office building, for which we are targeting Green Building Platinum Certification and Net Zero for energy, water, and waste.

Let me introduce myself. My name is Dr. Munirajulu. I currently am responsible for CFD analysis in MEP AC design for buildings and factories, as well as Green Buildings & Sustainability in L&T, Larsen and Toubro, Limited India, L&T in short.

I use simulation technologies and tools extensively in the design of buildings. I have more than two decades of experience in using CFD technology for design analysis, validation, and optimization. I use CFD simulation in the design of airports, data centers, rail stations, convention centers, stadiums, large office buildings, residential buildings, and large factories.

I have been a regular speaker at Autodesk University since 2017, both in the US and India events. And I'm sure you will find this session interesting and useful. Let me give you an overview of our company Larsen & Toubro, Limited. We are a multinational conglomerate company based out of India.

We are present in 30 countries. We are into high-impact sectors of the economy. Our capabilities in design to deliver and encompass technology, engineering, construction, manufacturing, et cetera. L&T Construction is the construction arm of L&T, and India's largest construction organization, and ranked among world's top contractors.

Buildings & Factories is one of the business lines of L&T Construction. We design and build commercial buildings, residential buildings, public spaces, and airports. In commercial buildings category, we design and build large office buildings, data centers, information technology, and software parks.

Our capabilities in design and construction span the entire gamut of construction; civil, mechanical, electrical, and instrumentation engineering. We design and build many landmark and iconic projects at L&T Construction, as you can see few showcase projects in this slide.

We have designed and built Green Buildings, 40-plus million square feet constructed till date. One such building is a technology and business center, which is India's largest platinum rated building. Rating awarded by Indian Green Building Council. Some salient features of the project are significant energy savings and water savings. 28% energy savings, 38% water savings are achieved.

Other Green Building features include 100% reuse of treated water, 100% storage of rainwater runoff, on-site solar power, and use of recycled and green materials.

Another iconic Green Building project from L&T Construction is the world's largest cricket stadium. Significant achievements in this project are, as part of Green Building design, are 21% energy savings, 30% water savings, and 96% construction waste recycled and reused.

This project is gold rated for Green Building category by Indian Green Building Council. Our company has set target to achieve water neutrality by 2035 and carbon neutrality by 2040. I will touch base briefly on Green Building concepts and techniques that lead to better buildings.

Green Buildings are better because they are better for business. Better for business in terms of increased occupancy rates, premium pricing, and meeting ESG goals as Green Building design and construction focuses on building efficiencies, reduced operational costs, and increased asset value.

Better for people because Green Buildings provide healthier air quality, reduced pollution. Better for the environment because Green Buildings prioritize reduced energy use and carbon emissions for tackling climate change.

Building sector has significant impact on climate change. Building and construction sector accounts for about 40% of global energy consumption, and is responsible for about 40% CO2 emissions. Construction alone accounts for 6% energy consumption and 10% greenhouse gas emissions.

COP27 commitment requires limiting global temperature rise to 1.5 degrees Celsius, above pre-industrial levels. This requires a green gas emissions decline by 43%, by 2030. As we can see, building sector plays a vital role in climate impact and hence, Green Building design, construction, and operation is critical to limit climate change.

Green Buildings provide tangible benefits in terms of energy savings to an extent of 20% to 30%, and water savings to an extent of 30% to 50%. Intangible benefits include enhanced air quality, improved daylighting, health, well-being, and safety of occupants, and also conservation of resources.

So ensuring energy efficient and sustainable buildings is a key to tackle climate change. By building to lead Green Building standards, it is reported that buildings contributed to 50% fewer greenhouse gases than conventionally constructed buildings due to water consumption. 48% fewer greenhouse gases due to solid waste and 5% fewer greenhouse gases due to transportation.

To summarize goals for Green Buildings: to reduce contribution to climate change are directed towards energy efficiency and use of renewable power, such as solar and wind. Water conservation, protecting and enhancing biodiversity, promoting sustainable and regenerative material cycles, and enhancing human health and quality of life are other important goals in Green Buildings.

To reduce impact of buildings on the environment, next level of achievement in Green Building design and construction and operation is Net Zero Buildings. Net Zero goals focus on high-performance buildings with reduced greenhouse gas emissions through Net Zero energy, Net Zero water, and Net Zero waste, and finally, Net Zero carbon strategies.

For Net Zero Buildings, the goal is to reduce operational carbon by reducing energy demand, by energy efficient design and meeting the energy demand through renewable energy sources. Renewable energy sources can be on-site and/or off-site.

The goal of Net Zero Energy is to reduce energy demand to ensure buildings are highly energy efficient, and 100% of energy demand is met by on-site/off-site renewable energy sources. Usually, renewable energy sources are wind and solar. This reduces operational carbon and hence, carbon emissions.

Net Zero Water Building is designed to minimize total water consumption, maximize alternative water sources, minimize wastewater discharge from the building, and return water to the original water source. Net Zero Water creates a water neutral building where the amount of alternative water used and water returned to the original water source equals the building's total water consumption.

Net Zero Waste eliminates the diversion of waste being sent to landfills. This is done by increased use of green products and materials, reduction in material consumption, increase in reuse of waste, and reduction in costs associated with waste handling and disposal.

The quantity of waste generated needs to be reduced, and quantity of waste reused and recycled need to be increased, so that quantity of waste to the landfill is minimized. It's leading to Net Zero Waste Buildings.

So far, we have seen that reducing energy demand is imperative for both Green Building design, as well as Net Zero Buildings. Using air conditioners and electric fans for cooling accounts for nearly 20% of the total electricity used in buildings around the world, or 10% of all global electricity consumption today.

Air conditioning use is expected to be the second largest source of global electricity demand growth after the industry sector, and the strongest driver for buildings by 2050. So exploring opportunities for energy efficient air conditioning is a key driver in buildings. We will see how we have used Autodesk CFD for evaluating energy efficient designs.

Here, for a sports training multi-purpose hall ventilation, we have evaluated multiple designs to arrive at energy efficient design. Three scenarios are considered. Scenario one, axial fans for ventilation. Scenario two, propeller fans for ventilation. Scenario three, optimized propeller fan scheme.

Requirement was to get airflow velocity less than 0.15m/s in the playing zone, at 4m level from the floor. Based on CFD results of air supply inlet layout, was optimized as in scenario three compared to scenario one and two.

In scenario two and three, energy efficient propeller fans were used, and in scenario three propeller fan layout was optimized. Overall, 26% energy savings were achieved. And this ventilation system is cost-effective alternative to more energy consuming air conditioning system. So meeting sustainable design goals.

Displacement ventilation-based air conditioning system is an energy efficient cooling system. However, design needed validation through CFD modeling and analysis. Displacement ventilation system is cost-effective for maintaining thermal comfort and reduced cooling costs compared to traditional mixing air conditioning systems, thus providing benefits of sustainable design.

Autodesk CFD Simulation is used for evaluating the performance of displacement ventilation system. The displacement ventilation system was used for air conditioning of the grand foyer of a large convention center. And a grand foyer is a large open space for people's circulation that gives access to the exhibition halls, cafes, restaurants, meeting rooms, and to the convention center.

CFD results showed that the occupant level temperature is achieved for thermal comfort and hence, design was validated. To conclude, displacement ventilation system is used to address architectural and structural constraints. The performance of displacement ventilation system in terms of thermal comfort is evaluated using Autodesk CFD.

Maximum stratification that occurs in the displacement ventilation system leads to reduced air flows, airflow rates, and hence, reduce energy consumption. Reduced outdoor air requirements also leads to significant energy savings in this type of air conditioning system. Displacement ventilation system leads to increased indoor air quality, a minimum of 20% improvement, lower peak CO2 levels, and improvement in air quality. All the above contribute to meeting sustainable design goals.

Autodesk CFD is used to evaluate wind loading on facade and roof of a large airport, as conventional calculations are not available. The CFD Simulation and analysis of wind loading provided useful information on wind flow, wind pressure, structure loading, and this resulted in less rework and optimized design, meeting sustainability goals.

Choice of energy efficient design for air conditioning is critical for reducing energy demand and hence, contributing to Net Zero energy goals. We will go through a project where we have evaluated a green variable air volume air distribution design, in comparison with conventional fixed flow rate air distribution system.

The project for which we are targeting Net Zero energy, water, and waste is a large high-rise office space with three levels of basement, ground floor, and 13 floors for office and business purposes. Built up area is 62,000 square meters, meant for 5,000 occupants on 12 floors.

Many energy efficient technologies are used in this project, and I will share the use of Autodesk CFD Simulation for evaluating a variable air volume system for air distribution for thermal comfort in this project.

Conventional air distribution system is a constant air volume diffuser. Air flow rate is fixed based on damper control from a room thermostat. And the airflow rate is fixed for the entire supply branch with multiple diffusers by the damper on the supply branch.

Energy efficient option was a VAV-based diffuser. Air flow rate is controlled automatically by individual thermostat and built-in damper in the diffuser itself, providing individual zone of variable air volume control. Therma-Fuser is a brand name of a variable air volume diffuser considered in this project.

Advantages of Therma-Fuser are superior air distribution, pleasing comfort, occupants breathe easier, providing personal temperature choice. And these type of variable air volume diffusers lead to lowest energy consumption, and hence, it can be called a green variable air volume design and low to no maintenance, leading to sustainable design and easily adapts to office changes in terms of occupancy.

A portion of the office space is considered for CFD analysis using Autodesk CFD. CAD model is shown on the left and CFD model created in Autodesk CFD is shown on the right. The detailed CFD model consists of furniture, computer hardware, and the seated occupants.

The model is used for two design scenarios. Scenario one with slot diffusers, and scenario two, term of user. CAD model is prepared using Fusion 360 and the slot diffuser CAD model is shown on the left, and the CFD model air volume capturing flow path is shown on the right.

Similarly, CAD model for Therma-Fuser is shown on the left, and the model for airflow path is shown on the right. Design data for CFD model includes external heat gains, using overall heat transfer coefficients-- that is U values-- and outside ambient temperature, and internal heat gains are accounted for lighting equipment and people load.

Diffusers are specified by design supply flow rates and supply temperature in the CFD model, as you can see on the right side. Now, we will look at CFD results from Autodesk CFD Simulation.

Temperature distribution and airflow pattern are analyzed to understand the effect of two types of air distribution systems for occupant comfort. Results are visualized on vertical and horizontal planes to get insight into the performance of the air distribution system.

Here we have the room temperature distribution for 100% occupancy, comparing slot diffuser and the VAV diffuser, Therma-Fuser. We see that the traditional diffusers, that is slot diffusers, results in non-uniform temperature, over-cooling, compared to the Therma-Fuser.

The room airflow results show that the VAV diffuser-- that is, the most used diffuser-- provides better air mixing, as you can see in the image at the bottom, than the slot diffuser. And cold air dumping is evident from the slot diffuser, as we can see in the image on the top.

When occupancy is reduced, the effect of non-uniform temperature distribution, over-cooling, and cold air dumping from slot diffuser becomes significant. And this type of air distribution and temperature is not energy efficient. In comparison, VAV diffuser provides better room air mixing and uniform temperature for the occupant comfort.

With reduced occupancy, room airflow results show that the VAV diffuser provides better air mixing than the slot diffusers, as you can see from the velocity pattern. The room temperature distribution at 1m from finished floor level indicate a similar outcome, that is over-cooling, cold air dumping, and non-uniform temperature in the case of slot diffuser, in comparison to the Therma-Fuser.

With reduced occupancy, the effect of over-cooling, cold air dumping, and non-uniform temperature becomes significant, as you can see in these temperature plots for slot diffuser and Therma-Fuser.

In conclusion, the use of traditional slot diffusers with VAV box for the air supply branch leads to over-cooling of occupied space in general, a non-uniform mixing of room air, and dumping of cool air. And this results into-- and this results into a system that is not energy efficient.

In contrast, use of Therma-Fuser with individual thermostat and built-in damper leads to no over-cooling, better room air mixing, and uniform temperature distribution. So the CFD analysis of office space using Autodesk CFD helped us to evaluate the performance of energy efficient air conditioning diffuser system contributing to Green Building design and Net Zero targets.

Would like to conclude saying Green and Net Zero Buildings for a better tomorrow! Thank you for listening, and have a good day.