Lesson Overview:
Energy use is often the biggest source of a product’s environmental impact. You can learn to use energy more effectively by better understanding energy systems, choosing the right sources, and improving efficiency.
Objectives:
In this lesson, you will learn:
(1) that energy is critical to sustainable design to include learning what energy is, how it is converted into useful forms, and what engineers can do to create more energy efficient designs.
(2) to optimize energy use in mechanical designs, reduce the unwanted friction forces when parts move against each other.
(3) to reduce friction with good use of materials, lubrication, wheels, and more.
(4) how heat transfer and thermodynamics is key to creating energy efficient designs.
(5) to use conduction, convection, and radiation to improve energy use.
(6) why fluid dynamics is vital to creating energy efficient designs.
(7) to reduce energy losses, learn how to minimize fluid drag, viscous drag, and major and minor head losses.
(8) how building energy loads reduces energy use, enabling architects to design net zero energy buildings.
(9) to use convection, conduction, and radiation to design passive systems.
(10) to use daylighting, efficient lights, and good controls to both reduce energy demands and make people happier and more productive.
(11) how mechanical Heating, Ventilation, and Air Conditioning (HVAC) systems help keep building occupants comfortable when passive design strategies aren’t enough.
(12) to design efficiently by not oversizing the system, choosing efficient components, and optimizing the whole system.
A. Energy Efficient Design
Watch the 'Introduction to Energy Use In Design' movie
Humans use energy to enhance life in important ways. Yet commonly used energy sources like coal, oil and gas are finite in supply and release greenhouse gases. To continue to improve quality of life while maintaining the planet’s ability to support us, we need to both move towards renewable energy and design for energy efficiency.
Energy efficiency is only part of the story. Being energy effective means both designing for efficiency and choosing the right technologies and energy sources. For example, the Carnot cycle dictates that the most efficient internal combustion engines will only be 40% efficient with today's materials. Also, most use fossil fuels. Instead, it's more effective to use an electric motor with energy sources generated from the sun and wind.
Engineers and designers have a big role to play. By understanding energy, how it is converted to useful forms, and where it is lost, engineers and designers can rethink the way we make things and use energy more wisely.
Energy is the ability to do work. It is measured in joules or kilowatt-hours. Power is the rate at which we use energy, and it is measured in watts. To get the energy when and where we want it, we need to convert energy from one form to another.
There are many different forms of energy. For example, the spinning wheel of your bicycle has mechanical energy and the battery in your phone stores chemical energy. Your toaster converts electrical energy to heat energy.
Whenever energy is converted, some useful energy is lost. Energy is also lost if designers aren’t careful about using it efficiently. Today’s engineers and designers have an incredible opportunity to help society use energy more effectively.
You can minimize common forms of energy loss like mechanical friction, fluid drag, and unwanted heat transfer, by doing things like improving the layout and insulation of a refrigerator or designing lighter vehicles that are more aerodynamic and have lower rolling resistance.
1. Reducing Friction
Watch the 'Friction: Reducing Energy Losses in Design' movie
Friction will occur at any place where two surfaces come into contact with each other. Friction can cause energy losses that create unwanted heat, deformation, and wear. This can reduce the lifetime and increase the cost of the products you design.
However, friction also helps us move around. Consider how our tires grip the road. With a thorough understanding of how friction works, engineers can create designs that reduce friction and resulting energy losses, while maintaining the benefits of friction when it’s helpful.
Friction forces oppose the direction of motion and can vary greatly based on the materials in contact, temperature, pressure, and whether the objects are stationary or moving. The coefficient of friction, μ, determines the friction force and is derived experimentally.The higher this number, the greater the resistance.
There are a variety of strategies to minimize μ and reduce unwanted friction. These include switching materials, using lubricants, adding wheels, and even preventing objects from touching using magnetics and acoustics. Reducing friction is studied in-depth in the engineering field of tribology.
Simulation software can help designers see the effects of friction in their designs. Autodesk® Simulation Multiphysics software can run mechanical event simulations (MES) that take the coefficient of friction into account, and provide visual and technical data to help optimize your design for energy effectiveness.
2. Heat Transfer
Watch the 'Heat Transfer: Reducing Energy Losses in Design' movie
Heat Transfer refers to how heat energy moves through the world around us. Refrigerators, ovens, laundry machines, cars, and buildings all manage the flow of heat. Engineers and designers who understand heat transfer can use energy more effectively by optimizing the form and materials of their designs.
There are three modes of heat transfer: conduction, convection and radiation. All three modes are often at work at the same time for any given object.
Conduction – When heat flows through a material itself based on temperature differences.
Convection - When heat is transferred through the bulk motion of a fluid.
Radiation – When heat travels as electromagnetic waves (like light).
For each of these modes, we measure the rate of heat transfer (q) in watts.
Understanding the physics and thermodynamics behind heat transfer can help you optimize your designs. For example, the rate of heat transfer depends on the materials you use and it goes up as both the temperature difference and surface area increase. You may want to encourage or avoid this depending on your design goals.
Simulation software can help engineers optimize heat transfer in their designs. Computational fluid dynamics (CFD) simulations take into account both heat transfer and fluid flow. CFD analysis can return both visual and technical data to help you create designs that use energy more effectively.
You can perform this type of analysis using Autodesk Simulation CFD or and Autodesk Simulation Multiphysics software. See more about Simulation for Sustainable Design.
Fluid dynamics is crucial to a wide range of products and systems. Whether you’re designing an airplane, a refrigerator, a plumbing system, or a turbine, you can make it more energy efficient by optimizing fluid flow.
3. Fluid Dynamics
Watch the 'Fluid Flow: Reducing Energy Losses in Design' movie
Fluid Dynamics is a study of the motion of fluids, including both air and water. Engineers can create energy efficient designs that optimize fluid flow by making smarter choices on the form, speeds, and materials of their designs.
Energy is required to move objects through fluids, like air around a car. To improve aerodynamics and use less energy, you need to reduce the drag coefficient. For example, the Urbee car has enclosed wheel wells and gentle curves in the front and back. These give it a streamlined shape that reduces its drag coefficient to about half that of normal cars.
Energy is also lost when a fluid moves through an object, like water in a pipe or air through the ducts in a building. Major head losses occur from the friction forces between the pipe and the fluid, and minor head losses occur as the fluid travels through bends and valves. One way to optimize designs is to eliminate sharp turns or widen your pipes.
Computational fluid dynamics (CFD) simulations can help you optimize your designs by helping you to better understand how your design will interact with fluids.
Using Autodesk® Simulation Multiphysics or Simulation CFD you can perform CFD analysis and optimize the fluid flow of your design.
Students and educators: Download Autodesk® Simulation Multiphysics software free of charge by visiting the Autodesk Education Community Download Center.
Visit the Autodesk SIM Squad to explore the latest trends in simulation or connect with experts.
Watch a 2-minute video that provides an Overview of Computational Fluid Dynamics (CFD) Simulation.
B. Net Zero Energy Buildings
Watch the 'Net Zero Energy Buildings and Energy Loads' movie
Reducing energy use in buildings is one of the most important ways to reduce humans’ overall environmental impact. This is because buildings account for 40% of worldwide energy use1 —far more than cars and airplanes combined.
To improve your building’s energy efficiency, you need to understand its energy loads. Energy loads help describe the flow of energy on the site and in the building.
Thermal loads such as heating and cooling come from the external environment (like sun, wind or weather) and internal operations (like heat generated by people and equipment). These loads need to be managed to keep the building comfortable. Lighting load is the energy used to power electric lights and plug load is the amount of electricity used for other equipment like computers. These loads are determined by the building’s intended use.
Use Energy Loads to Your Advantage By understanding the building’s thermal loads and its intended use, you can more effectively use the energy in natural systems to passively heat, cool and ventilate your building, light your building, and design efficient HVAC systems. You can also generate energy on-site by harnessing the power of the sun and wind.
When your building is energy efficient and generates enough energy on-site to equal its annual energy needs, you’ve designed a Net Zero Energy Building.
Watch the 'Passive Heating, Cooling, & Ventilation' movie
Passive HVAC systems run on energy from natural sources such as geothermal heat, sunlight, wind and cool air.
Consider the analogy of a sailboat, which uses natural forces to propel a boat through water. Similarly, you can ‘sail’ your building and keep its occupants comfortable by using passive design strategies for heating, cooling and ventilation.
To help you choose the most effective passive techniques, you first need to understand the following:
Your building’s environmental conditions, thermal loads, and energy loads based on your building’s intended use. See our video that covers building loads.
The factors that determine human comfort. See the article on Human Comfort.
The basic physics behind how heat is transferred through convection, conduction and radiation
Autodesk’s Building Information Modeling (BIM) software can help you predict the energy performance of your building before it’s built. You can visualize and simulate different design scenarios and quickly make changes to optimize them. Students and educators can access this software free of charge in the Autodesk Education Community.
Conduct solar radiation studies within Autodesk Vasari and Autodesk Revit to determine which faces of your building will receive the most sun, create the most shade, or have the most potential for adding solar panels. This will help you test design options and optimize your building’s form and orientation.
More information on conducting solar radiation studies can be found in the comparative conceptual design curriculum at the BIM Workshop.
To quickly predict and optimize building energy use in your design, you can build a massing model within Autodesk Revit Architecture or Autodesk Project Vasari and then create a conceptual energy analysis. This will give you estimates of your building’s energy use and display a broad array of weather data.
View several videos tutorials on how to build a massing model in Vasari or Revit.
View a video tutorial on how to conduct Conceptual Energy Analysis
To validate the effectiveness of your passive design strategies, you can perform a whole building energy analysis by exporting the BIM model to Green Building Studio. This will allow you to make adjustments to both the passive and active systems used in your building.
Students who are members of the Autodesk Education Community receive a subscription to Green Building Studio for free. Watch an overview of its features. For more precise results, it is also possible to export the model to eQUEST or Energy Plus.
The Anderson Anderson Architects Energy Neutral Portable Classroom project is an example of an innovative project that uses a host of passive design strategies to radically reduce energy use. It was designed and simulated using Revit Architecture, Ecotect Analysis, and other Autodesk tools.
2. Daylighting and Lighting
Watch the 'Lighting and Daylighting Design' movie
Daylighting, or using sunlight to illuminate your building, is an effective way to both decrease your building’s energy use and make it more enjoyable for people. Even when you can’t use daylighting, good lighting design can reduce energy use significantly. Both are important in Net Zero Energy Buildings.
a. Daylighting and Lighting Basics:
Strategies to increase the amount of sunlight within a space include using skylights, light shelves, reflective materials, and larger windows. Skylights can provide an even distribution of filtered light but can only be used where there is access to a roof. Large perimeter windows are ideal, but can cause glare without careful design. Nearby buildings can also cast shadows on your building, so pay attention to existing buildings and anticipate future buildings.
Visual comfort is a complex issue involving window positions, solar angle/latitude and glare. To make sure you’re providing the right amount of light for various activities, reference a list of common illumination levels. Good daylighting practices also take into account the thermal comfort of occupants and any increased in heat gain from the sun’s radiation.
You’ll have to use electric lights when natural sunlight can't satisfy all of your lighting needs and when daylight isn’t available due to cloud cover or nightfall. Task lighting, like desk lamps, ensures there’s enough light for a particular activity. Ambient lighting ensures that the overall space has enough light. Task-ambient lighting handles these two needs separately and leads to more efficient designs. Good user controls and automatic controls that can sense and adjust to light levels can both help optimize comfort and energy efficiency.
Autodesk software can simulate your lighting and daylighting designs to ensure the building performs well as the sun’s position changes.
Using Revit or Vasari, you can simulate the Sun’s path to see how shadows will be cast from your building and any other surrounding buildings or trees. For more detailed visualization and analysis of shadows, daylight factors, and solar radiation you can use Autodesk Ecotect Analysis. For further study, see these Lighting Analysis Tutorials.
To get a very visual sense of the lighting, you can create photo-realistic renderings. Take a look at the Light Measurement Tutorial Set to learn how to take advantage of the Mental Ray engine included within Autodesk 3D Studio Max, which produces physically accurate sunlight, reflections and shadows, and can measure the footcandles of light within the image.
3. Effective HVAC Design
Watch the 'Efficient HVAC Design' movie
Heating, Ventilation and Air Conditioning (HVAC) systems help keep building occupants comfortable. HVAC systems are usually designed by mechanical engineers and typically account for 30% or more of a buildings total energy use. An effective HVAC strategy is essential for a Net Zero Energy Building.
Traditional HVAC systems heat or cool air that is then forced throughout the building. To improve efficiency, look for equipment with a high coefficient of performance or energy efficiency ratio. Also, maximize the whole system with integrative design. For example, heat exchanging systems can condition incoming air with energy from exhaust air. HVAC equipment that doesn’t use forced air, like chilled beams and radiant panels, can also be very efficient.
Using Autodesk simulation tools, you can estimate how much energy your building will use, make adjustments to building systems, and compare results to determine the optimal configuration. For early analysis, use the Conceptual Energy Analysis (CEA) Tools in Autodesk Vasari and Revit. First, create a massing model and then choose one of the several HVAC systems available for simulation.
Using Revit MEP, you can calculate peak heating and cooling loads, as well as measure the impact of varying the amount of outside air and the level of filtration. See Revit MEP Tutorials for detailed information about how to perform this type of calculation.
For more detailed analysis, you can export your model to Autodesk Green Building Studio. This will give you more information about weather conditions, the energy mix in your area, and a rough estimate of your building’s energy use. For more precise results with an externally validated tool from the US Department of Energy, you can export your Revit BIM model to eQUEST. For even further analysis of your Revit model, including visualizing airflow with Computational Fluid Dynamics, see Visual Quantitative Energy and CFD Analysis.
To see high-performance building design strategies at work in a more complex building, see the grocery store retrofit 10xE case study by The Rocky Mountain Institute (RMI). You will learn how to calculate lighting levels , determine HVAC load calculations, and perform whole building energy analysis from a BIM model.