6420 Thermal Analysis of Buildings

Transcription

1 6420 Thermal Analysis of Buildings Design Rules of Thumb Model Energy Considerations Christoph Reinhart L01 Building Energy Simulation Analysis

2 Course Objectives This seminar will introduce students to manual and computer based calculation methods to evaluate the thermal/energy performance of buildings. The course will also discuss nontechnical aspects of using whole building energy simulation during building design, retrofitting and operation. The primary simulation tool used will be DesignBuilder/EnergyPlus. We will also be working on an EnergyPlus plug in for Rhino. Rules of Thumb Energy Design Design Simulation analysis. Revised Design

3 Learning Objectives Learn how to carry out an energy analysis of an envelope-dominated building. Develop an intuition of when to use energy simulations as opposed to manual methods. Understand how simulations results can be effectively used during building design and operation. Learn how to set up a parametric energy modeling script using Rhinoceros, Grasshopper and EnergyPlus.

4 Course Philosophy An informed decision is a better decision. Simulations as a pedagogical means to bring building physics to life. Current user interfaces for energy simulations are at a point at which designers/novices i can make meaningful models? (If the userunderstand d the modeling assumptions.)

5 Why should I take this course now? New generation of design tools. Remaining question: How can designers effectively use them?

6 Mechanics Meet once a week on Fridays to There was a request to move the class up one hour to 9AM to noon. First half lectures, second half practical exercises Prerequisites: 6205 or equivalent Bring your laptops to class. Course open to all GSD students This is supposed to be an interactive class.

7 Course Overview Fundamentals Jan 29 Course Introduction Feb 5 Manual Methods Balance Point Feb 12 Numeric Methods I Response Functions, HVAC Feb 19 Numeric Methods II Radiation Exchange, Surface Convection, Daylight Feb 25 Manual vs. Numeric Methods Analysis of selected US DOE energy benchmark buildings Mar 6 Natural Ventilation Air Flow networks and Manual Methods Applications Mar 12 Practical Exercise Modeling a Small Building; Zoning Mar 26 Professional Practice I ASHRAE 90.1 and LEED Apr 2 Professional PracticeII Costs,Liability, bl Ownership, Commissioning, BIM Apr 9 Good Friday Individual Group Meetings with Instructor Apr 16 Building Simulation Modeler Perspective (Guest Lecture) Apr 23 Student tpresentations ti Case Studies and Parametric Energy Modeling

8 Assignments Feb 5 1. Individual: Work through Tutorial 1: Getting Started with DesignBuilder EnergyPlus and submit results for Boston. Feb Individual: Work through Tutorial 2: Load Schedules Feb Individual: Work through Tutorial 3: Construction Assemblies, Load Reduction & Shading Feb Group Presentation & Report: Compare manual and numeric methods for one of the DOE Energy Benchmark Buildings Mar Natural Ventilation Exercise Mar Group Presentation: Design a Residential Home I Apr 9 7. Group Presentation: ti Design a Residential lhome II

9 Course Projects Two types of project: Case Studies on the use of energy models in building design. Parametric Energy Modeling

10 Last Year s Project - Model Gund Hall Collect weather data Build an energy model Survey occupant behavior Measure Energy Use Compare predicted versus measured energy use ARUP prize for the best paper out of 208 submission on the application of building performance simulation in the design process.

11 Results Electricity & Thermal Electric: Significance of installed electric lighting power densities Heating Energy: Significance of Infiltration Rates

12 Results Cooling Initial Results for 2007/2008 Historic Cooling Data for Gund Hall Chilled water meters have been replaced. Benefit of an energy model for building operation (continuous commissioning) Results for 2006/2007

13 Conclusions from previous Seminar Design students are capable of learning to model a large complex building. Students had confidence in their results for comparative analysis purposes for smaller buildings. St d t f t l l i PBS d d h l i it Student comfort levels using PBS dropped when applying it to complex buildings (handover point to the mechanical engineers).

14 G(SD)2 Rhino Toolbar Radiation Maps Rhino Model Daylighting Metrics Thermal Analysis

15 Round of Introductions Your name/program/year. Have you any energy simulations in the past? (Which programs?) Other simulation experience? What are your favorite CAD tools? Could you do Fridays 9AM to noon? Main interests for this course. Which type of course project are you spontaneously more drawn to (Case Study or Rhino Modeling)?

16 Resources

17 Books and Publications Go through bibliography from the syllabus

18

19 Software WE will be using the following software throughout the course. Please use the setup files form the course web site. DesignBuilder 2.1 Open Studio (January 2010) EnergyPlus 4.0

20 Building Performance Simulation

21 What is BPS? Building performance simulation (BPS) is the attempt to model the various energy and mass flows within a building in order to predict one or several performance aspects of a building using computer simulations. Example performance aspects are energy, light, acoustics, LCA, structure, costs,

22 What are BPS used for? To compare different design variants. To demonstrate code compliance (most difficult). To reduce risk through reduced planning uncertainty.

23 Who should do PBS?

24 Architects! (At least some of them.) Better interfaces. Faster computers. To interactively improve your design at the schematic design stage. To be able to engage in a dialogue with the HVAC engineer. Competitive edge: high demand for simulationists Opportunity to work on more interesting projects.

25 Do today s BPS work? Yes, but: You have to make sure that the tool that you are using has been validated for the specific task that you intend to use it for and that you know how to use it properly. Energy BESTEST/ ASHRAE 140 Daylight: NRC Daylighting Test Cases gov/dirpubs/rio4 pdf

26 I have heard that LEED buildings, which receive a rating that is partly based on BPS, do often not save as much energy as predicted by the simulation.

27 Energy Performance of LEED Buildings Measured energy use data from 100 LEED-certified commercial and institutional buildings were compared to the energy use of the general US commercial building stock. On average, LEED buildings used 18 39% less energy per floor area than their conventional counterparts. However, 28 35% of LEED buildings used more energy than their conventional counterparts. Further, the measured energy performance of LEED buildings had little correlation with certification level of the building, or the number of energy credits achieved by the building at design time. LEED building uses less energy than the reference building LEED building uses more energy than the reference building Newsham et al. Energy and Buildings 2009

28 Measured Energy Performance vs. Energy Credits (BPS) Newsham et al., Energy and Buildings 2009 Poor correlation (lots of scatter in the data) Reasons can be attributed to differences as designed vs. as built vs. as used Despite these shortcomings, PBS is useful/required for the design of high performance buildings.

29 BPS Requirements Elements needed for BPS are a building model, a simulation program (GUI & engine) and a suitable metric that is able to measure the performance in question.

30 Simulation Engine vs. GUI Most building energy simulation programs come with a graphical user interface (GUI) as well as the actual simulation engine. The former is used to prepare simulation input files for the latter and to display simulation results once a simulation is complete. While the choice of GUI determines the ease of use if a simulation program, it is ultimately the engine that determines how reliable simulation results are. A great GUI with a weak engine cannot yield reliable results!

31 Slide 30 MSOffice1 Inset slide:gui and Simulation EngineExplain the difference (with a graph) and that an engine can have mutiple GUIs. Explain that the hcooice of simulation program should begin with the engine as results cannot be trusted otherwise. The (next slide) motivate our choice for EnergyPlus (what is it, what are its capabilties, accreditation etc. Active developer community with new modules being added contantly such as green roofs and phase change materials. There is also a growing user base.explain strategy of USDOE to offer the engine for freree and have comercial comapnies devleop GUIS and provide software support. Explain that in he long run a tool will have most credivbility if the osurce code is avaialbe (external quality fcontrol.)now why design builder: commercial tool, currently most matured GUI. Offers flexible geometry input and extensive material librabies and load profiles., 8/5/2008

32 Simulation Mindset Use simulations to create value for the design process. Have the end in mind before you start. Use a validated simulation tool. You have to understand the assumptions and limitations of the underlying simulation models and performance metrics. Build you model as simple as your intended use allows. If possible divide your model into pieces for a detailed analysis.

33 Energy Simulation

34 Energy Simulation

35 Energy Simulation

36 Energy Simulation

37 Significance of building energy simulations? Buildings consume roughly one-third of all the energy consumed nationally every year. Much of this energy is consumed maintaining the thermal conditions inside the building and lighting. Simulation can and has played a significant role in reducing the energy consumption of buildings Energy savings should be realized through comparing competing design variants (link to LEED).

38 Slide 36 MSOffice7 Inset slide:gui and Simulation EngineExplain the difference (with a graph) and that an engine can have mutiple GUIs. Explain that the hcooice of simulation program should begin with the engine as results cannot be trusted otherwise. The (next slide) motivate our choice for EnergyPlus (what is it, what are its capabilties, accreditation etc. Active developer community with new modules being added contantly such as green roofs and phase change materials. There is also a growing user base.explain strategy of USDOE to offer the engine for freree and have comercial comapnies devleop GUIS and provide software support. Explain that in he long run a tool will have most credivbility if the osurce code is avaialbe (external quality fcontrol.)now why design builder: commercial tool, currently most matured GUI. Offers flexible geometry input and extensive material librabies and load profiles., 8/5/2008

39 Simulation Engine vs. GUI Most building energy simulation programs come with a graphical user interface (GUI) as well as the actual simulation engine. The former is used to prepare simulation input files for the latter and to display simulation results once a simulation is complete. The developers of simulation engines and GUIs often work for different companies with the engine being developed at public organizations (government lab & universities) whereas GUIs are more often developed by commercial vendors. As a result there can be several GUIs for the same simulation engine. While the choice of GUI determines the ease of use if a simulation program, it is ultimately the engine that determines how reliable simulation results are. A great GUI with a weak engine cannot yield reliable results!

40 Slide 37 MSOffice6 Inset slide:gui and Simulation EngineExplain the difference (with a graph) and that an engine can have mutiple GUIs. Explain that the hcooice of simulation program should begin with the engine as results cannot be trusted otherwise. The (next slide) motivate our choice for EnergyPlus (what is it, what are its capabilties, accreditation etc. Active developer community with new modules being added contantly such as green roofs and phase change materials. There is also a growing user base.explain strategy of USDOE to offer the engine for freree and have comercial comapnies devleop GUIS and provide software support. Explain that in he long run a tool will have most credivbility if the osurce code is avaialbe (external quality fcontrol.)now why design builder: commercial tool, currently most matured GUI. Offers flexible geometry input and extensive material librabies and load profiles., 8/5/2008

41 Brief History of Simulation 1 st Generation handbook oriented, piecemeal (disparate simulation techniques) easy to apply but difficult to interpret 2 nd Generation (mid seventies) stress on temporal aspects of energy simulation; response functions (analytical solutions) HVAC modeling confined to steady state t 3 rd Generation (mid eighties) integration: only space, time, and climate are independent variables all other system parameters are linked and solved numerically first GUIs 4 th Generation (mid nineties) Ref. J Clarke integration continued data modeling and interoperability user centered knowledge based GUIs and user-training

42 Where are we now? Focus on integrated databases. Focus on modeling occupant behavior. Use of parametrics and genetic algorithms to identify optimum solutions. More quality control in simulations and enhanced workflows. Making simulations accessible to larger audiences due to market pressures. Use of the energy model for commissioning and operation.

43 History of Energy Modeling Tools BLAST at US-DOD, DOE2 at US-DOE, TRNSYS at University of Wisconsin and ESP at Strathclyde University 2001: DOE2 and BLAST merged into EnergyPlus Td Today: - several interfaces for DOE2: equest, Green Building Studio - several interfaces for EnergyPlus: DesignBuilder, Open Studio - ESP-r has only a very basic interface - several interfaces for TRYNSYS - IDA-ICE is gaining increased recognition in Europe - IES/VE uses proprietary APACHE engine

44 Understanding di Thermal Models

45 EnergyPlus continued EnergyPlus is freely available for download. The program comes with ample documentations but without a GUI. EnergyPlus capabilities are constantly being further expanded so that more recent modules might not be accessible through any GUI. As a result advanced users often start editing their models manually using a text editor. Once any manual changes have been made to a model one usually cannot go back to the GUI. INFO

46 Other reasons for using EnergyPlus It is a Qualified Computer Software for Calculating Energy Savings for Purposes of the Energy-Efficient Efficient Commercial Building Tax Deduction under Internal Revenue Code 179D. Expert users can get access to the source code allowing for third-party validation which adds to the software s credibility and long term reliability. EnergyPlus has been validated under the comparative Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs BESTEST/ASHARE STD 140. The BESTEST (Building Energy Simulation TEST) is a comparative set of tests which has become one of the industry s most accepted methods to validate and test the simulation capabilities of the exterior envelope portions of building energy simulation programs. More information at gov/dirpubs/rio4 pdf

47 We will be suing DesignBuilder as the GUI for EnergyPlus Includes extensive default libraries cudese te s e de au t ba es Emphasis on architectural concerns such as massing and building form, façade design and loads

48 Why DesignBuilder? We chose DesignBuilder the tool for this tutorial as we found it to be a mature product which offers flexible geometry input and extensive material libraries and load profiles. EnergyPlus is integrated within DesignBuilder s environment which h allows you to carry out complete simulations without leaving the interface. INFO When bringing whole-building performance simulation closer to designers it is key to make the process of setting up a model and populating it with technical data as simple as possible without compromising accuracy or rigor. Reliable data templates of libraries and components (constructions, materials, schedules, HVAC system, activity profiles, etc) are extremely important in this process as they help designers set up their models in a comprehensive and transparent way.

49 Why DesignBuilder? Simulation results can be effectively displayed and analyzed. simulation data in a comprehensive manner. DesignBuilder has quality control procedures which assure the accuracy of the results in comparison the stand-alone EnergyPlus engine. e.g. As EnergyPlus, it has been tested under the comparative Standard Method BESTEST/ASHARE STD 140.

50 Software Limitations An advanced user might find the EnergyPlus simulation capabilities that are accessible form the DesignBuilder GUI limiting. In this case a user can export a DesignBuilder model into EnergyPlus ASCII files. Unfortunately, it is currently not possible to import a modified model back into DesignBuilder. There are limitation for inputting complex geometry (e.g. geometries defined through smooth functions / free forms)

51 Demo

52 DesignBuilder GUI DesignBuilder model of a small office building Monthly energy use by fuel

53 Installation - DesignBuilder 2.0X (January 2010) - EnergyPlus 4.0 6it4qjq9t -Open Studio ch8tragu -SketchUp 7

54 Assignment & Reading #1 By Friday, Feb 5th: Work through the Getting Started with DesignBuilder/EnergyPlus tutorial and submit your DesignBuilder file for Boston via the course s Dropbox.

55 Questions