Energy and Building Modeling. 

Description:

     Energy and building modeling is a practice of predicting the energy and fuel use of a building.             

Purpose:

     The goal of energy modeling is to accuratly predict the energy use of a particular building and compair it to either the existing building, an improved building, or to test the energy performance of the building with regards to established codes     and standards.  

Industries served:

     All businesses, residential establishements, and industrial buildings that have a significant utility or energy use, would       benefit from energy modeling due to its ability to predict the useful savings that result from utilizing more efficient 

mechanical equipment or energy efficient practices.   Not all energy efficient equipment or practices fit all situations.      Analysis is necessary to find the most worthwhile savings created in exchange for the typically higher up-front cost and effort. 

Methods:

     Classification of the different methods are diverse in their practice but generally subscribe to the goal of predicting energy    use.   They range from the most complext of Computational Fluid Dynamic (CFD) simulations and hourly, or subhourly     simulations to simple spreadsheets that approximate the conditions of a particular site, energy use, occupancy, and     various other factors.  The choice between the different methods is primarily based on level of accuracy desired and what    methods codes or governing body require.    

Techniques:

     Techniques of modeling a particular building with the unique characteristics of that building is strongly dependent on the modeling software used.    Most software is very adaptable from one building to the next but the individual techniques of modeling HVAC equipment in particular can be very detailed.   Understanding how commons air systems work in a building are essential to making a properly working model.    

Existing Guides

• Equest Workbook
• MPP Guidebook

Common Units Used in energy modeling of buildings.

•   Tons of cooling
•   mmbtu vs. mbtu vs. kbtu
•   Therm
•   cooling horsepower
•   cfg (Cubic Foot of Natural Gas)
•   Killowatt-hours (kWh), Killowatts (kW), Kvar,  Phase angle, 3phase vs 2 phase vs single phase AC power
•  Square foot floor area approximation vs. actual flooring survace not including all thickness of walls.  

Software:

• DOE2
• Equest 3.61e (DOE2 interface)
• Equest refrig 3.61b (DOE2refrig -special simulation software for refrigerated facilities)
• Energy Plus ( Demand Response Quick Assessment Tool, DesignBuilder, EFEN, Hevacomp, HLCP,  TREATPlus,  EPlusInterface)
• Treat
• -many others to be udated at a latter time-

Data Classification:

Fundimental building characteristics.

• Outside Air
  • Air Changes Per Hour
  • HVAC exhaust-supply offsets
  • Wind 
  • Cracks in building envelopes
  • Stack effect through all Elevator,mechanical shafts, and stairwells.
  • Air boiancy effect through all elevator, mechanical shafts, and stairwells.
• HVAC
  • CVCT systems
  • VAV systems
  • PTAC systems
  • Typcial residential systems (urban)
  • Typical industrial systems
  • ASHRAE SYSTEM TYPES VS PROGRAM INPUTS
• ENVELOPE
  • Thermal bridging
  • Exposed floor slab, balconies
  • Roof dynamics
  • Cavity wall physics
  • Moisture barrier
  • Wall construction type dependencies on local climate.
• Occupancy
  • Occupancy Schedules:
    • Residential
    • Health Care facilities

Baseline Building Information

• Modeling Codes
  • ASHRAE 90.1 2004 APPENDIX G
  • MPP
  • LEED analysis methodology (per Credit)
• Typical Building Energy Use Resources
  • EBECS
  •  

Improved Building Information

• Modeling Codes
  • ASHRAE 90.1 2004 APPENDIX G
• Energy Conservation Measure Modeling Approaches
  • SOLAR PV
  • CONDENSING BOILERS
  • ENVELOPE IMPROVEMENTS
  • REFRIGERATED STORAGE FACILITY
  • ENVELOPE
  • LIGHTING
  • PROCESS IMPROVEMENT
  • BUILDING MANAGEMENT SYSTEMS
  • ENERGY & HEAT RECOVERY
  • COMBINED HEAT AND POWER (CHP)
  • NATURAL GAS RECRIPROCATING ENGINE GENERATOR, CHILLER
  • BIODESIL RECRIPROCATING ENGINE GENERATOR/ CHILLER
  • ABSORBTION CHILLER
  • HVAC IMPROVEMENT
  • ELEVATOR AND PEOPLE MOVING APPARATUS
  • COMPUTERS, OFFICE EQUIPMENT
  • DAY LIGHTING
  • WIND
  • GROUND-SOURCE GEOTHERMAL
  • RADIANT FLOOR
  • OCCUPANCY SENSING LIGHTING, HVAC
  • EXHAUST AIR DAMPERS
  • EXHAUST CONTROLS

Resources:

Building Modeling

-Information allocation

                -modeling code  (ASHRAE 90.1 2004 APPENDIX G)

                -simulation guidance, best practices, existing guides (NYSERDA MPP etc.)

                -building code, common practices (NREL, NYC VENTILATION STANDARD, ASHRAE 62, ASHRAE 55)

                -filling in the blanks –where to find solid, industry standard numbers where the modeling guideline stops. 

-How to model each aspect of a building in Equest/doe2, Design Builder (this will not be a all inclusive set of instructions but will be a list of the non-intuitive aspects of different programs –what they can do, what they can’t do, and what work around are necessary to model.  Example: how to import a drawing into equest, stack buildings, and make the floor/ceiling relate.

-discussion of the differences between: diversity numbers (1.1 w/sf all year) and source numbers (60 watt bulb on a 4 hours / day schedule)  

-Units commonly found in building energy.  Tons of cooling, mmbtu, Mbtu, therm, cooling horsepower; numbers not commonly defined elsewhere. 

-Energy Efficiency Measures.

                -(I have a long list of these in my bookmarks and there are some great places on the web)

                -How to model challenging ones with Equest/doe2, Design Builder/Eplus

-Output interpretation –reality check

                -comparing the building model to reality  (LBNL http://buildingsdatabook.eere.energy.gov/?id=view_book)

                -Typical heating loads by building type, Heating factor calculation

                -typical cooling loads by building type,

                -typical hot water use for: apartments, restaurants, swimming pools, car wash.

-typical electrical use for: battery cart charging stations, data centers, Sauna, Steam room, Movie theater projection room, etc.

This is an online compilation of energy modeling resources.   Primarily the documents and link