# DESIGN AND CALCULATION TOOLS

## Presentation on theme: "DESIGN AND CALCULATION TOOLS"— Presentation transcript:

DESIGN AND CALCULATION TOOLS
ENERGY EFFICIENCY AND SUSTAINABILITY OF BUILDINGS DESIGN AND CALCULATION TOOLS Prof. dr. Marija Todorovic DERES - DIVISION FOR ENERGY EFFICIENCY AND RENEWABLE ENERGY SOURCES Faculty of Agriculture, University of Belgrade, Serbia th November

AIM OF THIS LECTURE Introduction of the UNESCO E-Learning audience to the computational modeling techniques which are, as the most powerful current design and calculation tools, increasingly being used to successfully predict the internal and external conditions within and around buildings, as well as the buildings energy loads and consumption. Building services engineers, architects, developers and clients use the results to evaluate HVAC strategies to ensure specific project requirements are achieved on-site first time. Substantial savings can be made through low cost design and the avoidance of on-site re-design and re-commissioning.

DEFINITIONS - DYNAMIC THERMAL
SIMULATION AND CFD A computer model of the energy processes within a building that are integrated to provide a thermally comfortable environment for the occupants (or contents) of a building - Building Performance Simulation (BPS) and BPS & prediction (BPSP). The external environment of a building changes permanently. Due to its thermal capacity, the structure and fabric of, a building responds to these changes. This in turn leads to a more gradual dynamic response of the interior climate and to HVAC’s, lighting’s and other technical systems loads and energy use variation. Prediction of dynamics of these changes is of crucial importance in the design of building’s energy efficient heating, cooling & air-conditioning strategies.

DYNAMIC THERMAL SIMULATION AND CFD -COMPUTATIONAL FLUID DYNAMICS
Dynamic Thermal simulation can predict changing internal conditions over a time period of up to 1 year – TMY 8760 hours. The technique predicts zonal (or room) values for parameters such as air temperature. With ever improving computer technology, the use of CFD in Building Design and in the design of HVAC strategies is becoming more widespread. CFD is the only choice to obtain the important details of the internal climate which result from a particular HVAC design. The expertise necessary to fully utilise the latest CFD software for design issues, be they internal environment relevant (velocity, humidity, concentration field and air flows) or external (wind-driven) air flows.

BUILDINGS PERFORMANCE SIMULATION
Describe the building - Physically - Mathematically - Focus on HVAC, lighting and energy supply Computer programs - Whole building programs - Component-based, modular simulators Interpret and use the results

PURPOSE OF BUILDINGS PERFORMANCE SIMULATION
Buildings use % of national energy Improve/optimize energy efficiency Efficiently introduce RES Reduce LCC - life cycle costs Improve comfort and habitability Develop codes and standards Address special design problems Historical building renovation Innovative design Local requirements, i.e., no A/C

WHO SHOULD PERFORM BP SIMULATIONS
A & E firms design/optimize EE issues, marketing Large property owners operational policy/energy cost, retrofit Government agencies code development & enforcement Research labs improving knowledge base, extending state- of-the-art Utility companies marketing, planning

WHOLE BUILDING SIMULATORS
Model 5 to 50 and more thermal zones Detailed description of construction Detailed representation of load profiles of components and total Analyze HVAC systems and plant options Somewhat simplified/or optimized numerically – improved convergence Previously: DOE-2, BLAST, AXCESS, Trace Now: EnergyPlus, PowerDOE, DesignBuilder ESP-r, APACHE, lots of third party derived products

EFFECTIVENESS AND EFFICIENCY OF MODULAR SIMULATORS
Difficulties in describing complex envelopes and structures Complete flexibility/interoperability Rigorous numerical methods Shorter solution times Could be better suited to whole integrated building/HVAC simulations TRNSYS, HVACSIM+, SPARK, IDA

CURRENT ISSUES- WHOLE INTEGRATED BUILDING DESIGN
Flexibility - HVAC System & Plant - Building shell description - Usage patterns Ease of use  wider usage Accuracy - Integration: all-in-a-time step calcs. - Hi-tech: CFD, boundary conditions, contaminant tracking - Validation Cost effectiveness

FUTURE R&D TYPES FOR DIFFERENT USERS GROUPS
Four principal future R&D types for different users can be distinguished, each of which have their own particular needs: building and its technical and HVAC systems designers and operators, building investors and users, local or regional government policy makers and building/HVAC systems physics phenomena and construction HVAC engineering researchers.

INTEGRATED BUILDING DESIGN Need for wider implementation and
Dissemination New technological approach in designing SUSTAINABLE “GREEN” BUILDINGS considering energy efficiency, renewable energy and renewable raw materials utilization and environmental technologies implementation.

CFD – PHOENICS, CFX, FLUENT
Multimodel approach in Integrated Building Design – Energy Efficiency Optimisation TRNSYS DOE2 SERIES VISUAL DOE ENERGY PLUS, ESP-r APACHE Gen Opt ADELINE – RADIANCE SPARK, IDA ICE CFD – PHOENICS, CFX, FLUENT

GenOpt A GENERIC MULTI-PARAMETER PROGRAM FOR SYSTEM OPTIMIZATION.
Automatically determines the values of user-selected design parameters that lead to the best operation of a given system. Optimizes a user-selected objective function, such as a building's calculated annual energy use. Offers an interface for implementing own optimization algorithms into its library, and has an open interface on both the simulation program side and the optimization algorithm side. By modifying a configuration file, it allows users to easily couple any external program (like DOE-2, SPARK, BLAST, EnergyPlus, TRACE, TRNSYS, etc., or any user-written program). GenOpt is written entirely in Java so that it is platform independent. An interface for coupling external simulation programs and adding custom optimization algorithms is available.

Domain specific Common Framework
Envelope & Zone Heat Balance Models & Solution Climate & Radiation Models & Solution HVAC Models & Solution Multizone Air Models & Solution Domain specific Typical architecture of a simulator in the traditional approach

GUI Equation Based Framework Domain independent Domain specific
Envelope & Zone Heat Balance Models Climate & Radiation Models Shading Models Numerical Solver 1 Numerical Solver 2 Symbolic Processor Language Parser HVAC Models Domain independent Domain specific Basic architecture of an equation based building simulator

MODELED TO SOME EXTENT TO FORM A MEANINGFUL SIMULATION
MODEL ARE Outdoor climate conditions, including temperature and incident solar radiation Dynamic heat flux through the building envelope and internal structure Heat balance of each room (or ventilated zone) Air, water flows and Heat flow through the primary and Secondary HVAC system

Windows and daylighting
Thermal Bridges Window simuation study Therm Series

MANY TOOLS ALSO MODEL A SERIES OF THE CLOSELY COUPLED QUANTITIES
Moisture transport within the building Cost of supplied energy Thermal sensation (comfort) of building occupants Daylighting Naturally occurring air-flows between and within zones Indoor Air Quality Performance of ground-coupled systems

Three typical purposes and corresponding time-scales of building performance simulations Prediction of extreme conditions (design day or design period of year) Prediction of the energy consumption (per year) Prediction of controller action (1/100- seconds) Typical Meteorological Year

Buildings Energy Tools Software by Subject
Whole Building Analysis Energy Simulation Load Calculation Renewable Energy Retrofit Analysis Sustainability/Green Buildings Codes & Standards Materials, Components, Equipment, & Systems Envelope Systems HVAC Equipment and Systems Lighting Systems Other Applications Atmospheric Pollution Energy Economics Indoor Air Quality Solar/Climate Analysis Training Utility Evaluation Validation Tools Ventilation/Airflow Water Conservation Misc. Applications

AAMASKY skylights, daylighting, commercial buildings Total number 335
ABACODE Residential code compliance, IECC ACOUSALE acoustics, codes and standards Acoustic Program HVAC acoustics, sound level prediction, noise level ADELINE daylighting, lighting, commercial buildings buildings AFT Fathom design, pump selection, pipe analysis, duct design, duct sizing, chilled water systems, hot water system AFT Mercury optimization, pipe optimization, pump selection, duct design, duct sizing, chilled water systems, hot water systems AGI32 lighting, daylighting, rendering, roadway AIRPAK airflow modeling, contaminant transport, room air distribution, temperature and humidity distribution, thermal comfort, computational fluid dynamics (CFD) AkWarm home energy rating systems, home energy, residential modeling, weatherization Analysis Platform heating, cooling, and SWH equipment, commercial buildings Animate animated visualization of data, XY graphs, energy-use data AnTherm thermal bridges, heat flow, steady state, transfer coefficients, temperature distribution Apache thermal design, thernal analysis, energy simulation, dynamic simulation, system simulation

Proposed Design Standard Simulate both designs Compliance achieved yes
PD <= SD ? Compliance achieved yes no Revise design determines (Requires two annual energy simulations) (A “twin” building generated IAW the “rule set”) PERFORMANCE METHODS

MODELS IN BUILDING ENERGY PERFORMANCE SIMULATION CLASSIFICATION
Dynamic - Uniform time unit Discrete - Continous change captured at “discrete moments” Deterministic - Decisions based on certainty Models for (comparative) analysis

KNOW AND UNDERSTAND ASSUMPTIONS
Explicitly stated/documented assumptions Implicit assumptions Assumptions based on (scientific) fact Assumptions based on conventionaal wisdom Assumptions based on educated guesses Assumptions based on wild guesses

GOALS OF BUILDING THERMAL SIMULATION
Load Calculations - Generally used for determining sizing of equipment such as fans, chillers, biolers, etc. Energy Performance Analysis - Helps evaluate the energy cost of the building over longer periods of time

SIMULATIONS DO ENERGY SAVING
Building thermal simulation allows one to model a building before it is built or before renovations are started Simulation allows various energy alternatives to be investigated and options compared to one another Simulation can lead to an energy-optimized building or to a more informated design process Simulation is much less expensive and less time consuming than experimentation – every building is unique

EVERY BUILDING IS UNIQUE
Every building is different in many ways: - Location and exterior thermal environment - Construction/building envelope - Space usage/interior environment - HVAC system Exterior thermal environment is a driving force that determines how a building will respond Energy efficient design requires an understanding of and a response to the exterior thermal environment Thermal simulation requires information on the exterior thermal environment to properly analyze the building from an energy perspective

ADDITIONAL FORECASTS Building performance analysis and evaluation through computer modeling and simulation will likely become increasingly important - Encourages product innovation - Fits the entrepreneurial market - Allows design flexibility - Provides for cost optimization There will be increasing market pressure to verify, certify and accredit building energy performance software tools.

MORE CONTEXT As little as 10 years ago, detailed building energy simulation and analysis was effectively limited to “research institutes” Significant computational power (memory and speed) needed Significant user knowledge (thermodynamics, materials, algorithms, etc.) needed Today’s powerful PCs, databases and GUIs have changed our world Now “dumb” users plus “smart” interfaces can achieve acceptable results.

Performance-based codes and standards “Beyond code” programs
SOME OF THE INCENTIVES Performance-based codes and standards “Beyond code” programs DOE Building America program EPA ENERGY STAR® program “Green building” programs (LEED, etc.) Utility & “public benefits fund” incentives Proposed federal tax incentives Pollution and “Carbon” programs EPA non-attainment program (Texas) European Union’s “Energy Performance of Buildings Directive” (EPBD) – mandatory!

EU EPBD PROGRAM Mandatory across EU for all buildings (existing and new) starting in January 2006! Requires each country to introduce a standard energy calculation methodology For all but simple buildings, requirement is being interpreted as a detailed simulation tool Questions about software standards, testing and verification.

NEW CHALLENGING GOALS Goal is dramatic improvement in residential purchased energy use 40% - 70% more efficiency by Ultimate goal: Zero-Energy Homes 70% efficiency improvement plus on-site PV power production for remainder (net zero) Design, analysis, accounting and reporting based on detailed simulation analysis.

PERFORMANCE STANDARDS
Challenges Basic principles are poorly understood by many (most building officials) Confusing lingo: Standard design, Reference home, Baseline home, Benchmark home Mistrust by building officials (“black box”) Consensus-based decision making Myth is more widespread than you think Science is often difficult to explain There are often unintended consequences (scientists do this a lot)!

CHALLENGES Users (dumb & dumber) Software errors Results consistency
Inadvertent errors (typos, etc.) Lack of knowledge Software errors Faulty algorithms Bugs Results consistency Differences of opinion (algorithms) Sophistication detail

Algorithm Differences Reference results can vary widely!

COMPONENTS SPECIFIED Above grade walls Basements and crawlspace walls
Above grade floors Ceilings Roofs Attics Foundations Doors Glazing Skylights Sunrooms Air exchange rates Mechanical ventilation Internal gains Internal mass Structural mass Heating systems Cooling systems Service hot water Thermal distribution systems

OTHER IECC* REQUIREMENTS
Computer generation of standard reference design – no user modification allowed Calculation of equipment sizing for standard reference design Generation of official inspection checklist listing each of the proposed design component characteristics Calculations that account for effects of climate and equipment sizing on system performance. *International Energy Conservation Code

IBPSA CHALLENGES Participate actively in efforts to develop software verification methods and test suits Seek methods to reduce real differences in software results due to algorithm differences Help all of us walk that fine line between the most advanced simulation models and techniques the CEFAPP needs of the marketplace.

BUILDING’S EXPERIMENTING
Repeatable physical experiments on buildings are often difficult to perform. Many building systems are too bulky for laboratory measurements and long term measurement on real buildings are either expensive, due to the cost of an unoccupied building, or disturbed by building utilization. This makes computer based experimentation on building models attractive.

INNOVATIONS IN CONSTRUCTION INDUSTRY
The building industry is oriented towards one-of-a-kind production, with a low relative investment in engineering. Coupled with the difficulty of in situ measurements, this creates unfavorable conditions for innovation and performance feedback. The process of natural refinement of engineering solutions is therefore slow. Ability to experiment with new solutions in the design office by simulation is bound to improve this situation, if the right tools are available.

EXPERIMENTING BY SIMULATIONS
Furthermore, since malfunctions in the delivered product are difficult to detect and quantify, designs that do not perform correctly, even theoretically, are sometimes realized. If design offices were obliged to demonstrate intended functionality on a computer model prior to realization, many such problems could be avoided.

SUCCESSFUL DEVELOPMENT HISTORY Whole-Building Simulators
Under Floor Air Distribution System (versions 1.01, 1.1) Have the supply plenum, slab coupling, need better zone model Ground Coupling (version 1.01) Photovoltaics, TRNSYS link (versions 1.01, 1.1) Cooled beams, cooled ceiling panels (version 1.1) Equipment sizing (versions 1.01, 1.1) Heat recovery: more types, controls (versions 1.01, 1.1) Missing old stuff air-to-air, water loop, ground source heat pumps (version 1.01)

Energy Plus SIMULATION FLEXIBILITY
VS. SIMPLICITY HVAC Simulation Based on Configurable Input Template Systems Code Allows Connection Flexibility Input Defines Specific System Configurations - Connections are in the Input Completely Modular Systems and Real-Time Controls Handled by Links to SPARK and TRNSYS

30+YEARS OF BUILDING SIMULATION
User interface advanced from: Numbers (NBSLD) to Textual languages (DOE-2, BLAST) to GUIs (PowerDOE, DOE-2 add-ons) Perhaps we are nearing “user friendly” and ready for the practitioner?

30+YEARS OF BUILDING SIMULATION
Modeling paradigm shifted from: Procedural languages (NBSLD*) to Monolithic programs (DOE-2, BLAST) to Modular simulators (TRNSYS, HVACSIM+) to Object oriented simulators (SPARK, IDA) Still need to merge this technology with the whole building programs. *National Bureau of Standards Load Determination

30+YEARS OF BUILDING SIMULATION
Solving method shifted from: Hour-by-hour solving without iteration (DOE-2, BLAST) to Sub-hourly time step with iteration (EnergyPlus) to Proper error controlled numerical solving of differential algebraic systems (SPARK, IDA) Still need to integrated all this into the whole building codes.

Fully Integrated Loads & HVAC Simulation Example: chiller capacity exceeded Occupant Comfort Moisture storage and release Mix and Match systems Green Buildings Example: natural ventilation, COMIS Lots more Low and high temperature radiant heating supply air plenums

Mathematical modeling Application development Model use measurement
specification Mathematical modeling Formally Described models Library models researchers Application development Ready made applications Software engineers specification Model use Simulation results . Mathematics . Physics . Signal processing . Experimentation consultants . Software development . Customer support . Market awareness . Other primary competence

CREATING SUSTAINABLE, ENERGY EFFICIENT BUILDINGS FOR THE FUTURE
An energy concept is a complete combined solution to energy efficiency in buildings and energy supply incl. – Demands on building design and installations – Energy storage and local energy production The aim is to find the optimal solutions

WHAT IS NECESSARY TO OPTIMIZE AN ENERGY EFFICIENCY?
Considerable efforts from project start Good co-operation between architects and engineers and a dedicated client Specialist knowledge, inventiveness, and information on new solutions Follow-up on the preconditions of the building Analysis of a number of innovative solutions Selection of a solution with good indoor climate and as environmental friendly Optimisation with the reference to the cost effectiveness and overall economy

WHAT IS THE PRICE? NO extra investment costs are needed!
In case of an optimal combination, the construction costs will be cheaper Add to this operational savings for energy and maintenance!

INEXTRICABLE LINKAGE RES, REM, EnEfficiency and Sustainable Development All level regular and vacational Education, Engineering Experience (Designing, Construction, LCCommisioning and Operation) Most current knowledge and technologies and Mental awarness/Ethics of Sustainability Cost effectiveness/harmonization of - Dynamics of final energy user’s loads - Dynamics of Co/Trigeneration efficiency - Dynamics of technically available RES fluxes Small specific energy fluxes and Distributed character of RES versus Distributed Co/Trigeneration