Announcement

Course Exam November 3rd

In class: 90 minutes longExamples will be posted on the

course website

Announcement

- Project 1 Due This Thursday

- Course Exam is on November 3rd In class: 90 minutes longExamples are posted on the course website

Lecture Objectives:

Learn about weather files (TMY)

Discuss Modeling steps

Learning about QUEST and other software

Typical Meteorological Year (TMY)

• Collation of one year weather data for a specific location

• Generated from a historic data to represent typical year

• Not an average year! It contains real data.

1990 1991 1993 1993 1994 1995 1996 …. 2000 2001 ….. 2005

January February March April May December

Most typical moth

…..

What is in TMY

http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/by_state_and_city.html

TMYs Data sets • TMY

– Generated in 1981 for 26 U.S. locations for the period of 1952 to 1975

• TMY2– In 1990 reformatted and expanded to larger number of location. Also updated

to reflect 1961-1990

• TMY3 – In 2005 with greater emphasis on solar radiation data as well as the inclusion

of precipitation data.   – Include data for ~ 2,500 locations primarily in the United States and Europe,

but also world wide. – http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/– http://www.nrel.gov/docs/fy08osti/43156.pdf

• TMY4 – is coming soon (an update for the changing climate)

Modeling

Modeling

Modeling

Modeling 1) External wall (north) node

2) Internal wall (north) node

Qsolar=solar·(Idif+IDIR) A

Qsolar+C1·A(Tsky4 - Tnorth_o

4)+ C2·A(Tground4 - Tnorth_o

4)+hextA(Tair_out-Tnorth_o)=Ak/(Tnorth_o-Tnorth_in)

C1=sky·surfacelong_wave··Fsurf_sky

Qsolar_to int surf =portion of transmitted solar radiation that is absorbed by internal surface

C3A(Tnorth_in4- Tinternal_surf

4)+C4A(Tnorth_in4- Twest_in

4)+ hintA(Tnorth_in-Tair_in)= =kA(Tnorth_out--Tnorth_in)+Qsolar_to_int_ considered _surf

C3=niort_in··north_in_to_ internal surface for homework assume ij Fiji

transmitedtotalsolarsurfconsideredenvelopetotalsurfconsideredernaLsurfconsideredtosolar QAAQ ___int_int____int_int___ )/(

A- wall area [m2]- wall thickness [m]k – conductivity [W/mK] - emissivity [0-1]- absorbance [0-1] = - for radiative-gray surface,sky=1, ground=0.95Fij – view (shape) factor [0-1]h – external convection [W/m2K]s – Stefan-Boltzmann constant [5.67 10-8 W/m2K4]

C2=ground·surfacelong_wave··Fsurf_ground

Matrix equation

M × t = f

for each time step

b1T1 + +c1T2

+=f(Tair,T1,T2

)

a2T1 + b2T2

+ +c2T3+=f(T1

,T2, T3

)

a3T2 + b3T3

+ +c3T4+=f(T2

,T3 , T4

)

a6T5 + b6T6

+ =f(T5 ,T6

, Tair)

………………………………..

M × t = f

Modeling

Modeling

Modeling steps• Define the domain• Analyze the most important phenomena and

define the most important elements• Discretize the elements and define the

connection • Write the energy and mass balance equations• Solve the equations (use numeric methods or

solver)• Present the result

Structure of ES programs

SolverInterface for input data

Graphical User Interface (GUI)

Interface for result presentation

Preprocessor Engine Preprocessor

ASCIfile

ASCIfile

Modeling steps• Define the domain• Analyze the most important phenomena and define the most important elements• Discretize the elements and define the connection • Write energy and mass balance equations• Solve the equations• Present the result

ES program

Preprocessor

Solver

Postprocessor

ES programs

• Large variety • http://www.eere.energy.gov/buildings/tools_directory

• DOE2• eQUEST (DOE2)• BLAST • ESPr• TRNSYS• EnergyPlus (DOE2 & BLAST)

eQUEST (DOE2)US Department of Energy & California utility customers

• eQUEST - interface for the DOE-2 solver• DOE-2 - one of the most widely used ES program - recognized as the industry standard • eQUEST very user friendly interface • Good for life-cycle cost and parametric analyses

• Not very large capabilities for modeling of different HVAC systems

• Many simplified models • Certain limitations related to research application - no capabilities for detailed modeling

eQUEST

• Download it at http://doe2.com/equest/

• Examples related to:– Defining envelope and internal loads – Selecting HVAC system– Presenting results – Finding design cooling and heating loads– Extracting simulation detail

ESPrUniversity of Strathclyde - Glasgow, Scotland, UK

• Detailed models – Research program • Use finite difference method for conduction• Simulate actual physical systems • Enable integrated performance assessments

Includes daylight utilization, natural ventilation, airflow modeling CFD, various HVAC and control models

• Detail model – require highly educated users• Primarily for use with UNIX operating systems

ESPrUniversity of Strathclyde - Glasgow, Scotland, UK • Detailed models

– Research program

TRNSYSSolar Energy Lab - University of Wisconsin

• Modular system approach • One of the most flexible tools available • A library of components • Various building models including HVAC • Specialized for renewable energy and emerging

technologies

• User must provide detailed information about the building and systems

• Not free

Component-based simulation programs - Trnsys

EnergyPlusU S Department of Energy

• Newest generation building energy simulation program ( BLAST + DOE-2)

• Accurate and detailed• Complex modeling capabilities• Large variety of HVAC models• Some integration wit the airflow programs Zonal models and CFD

• Detail model – require highly educated users • Very modest interface• Third party interface – very costly

EnergyPlus

eQUEST

• Download it at: – http://www.doe2.com/equest/

Start working on Project 1

eQUEST HVAC Models• Predefined configuration (no change) • Divided according to the cooling and heating sources• Details in e quest help file:

For example: DX CoilsNo Heating– Packaged Single Zone DX (no heating)

• Packaged single zone air conditioner with no heating capacity, typically with ductwork.– Split System Single Zone DX (no heating)

• Central single zone air conditioner with no heating, typically with ductwork. System has indoor fan and cooling coil and remote compressor/condensing unit.

– Packaged Terminal AC (no heating)• Packaged terminal air conditioning unit with no heating and no ductwork. Unit may be window or through-wall mounted.

– Packaged VAV (no heating)

DX CoilsFurnace• Packaged direct expansion cooling system with no heating capacity. System includes a variable volume, single duct fan/distribution

system serving multiple zones each with it's own thermostatic control.– Packaged Single Zone DX with Furnace

• Central packaged single zone air conditioner with combustion furnace, typically with ductwork.– Split System Single Zone DX with Furnace

• Central single zone air conditioner with combustion furnace, typically with ductwork. System has indoor fan and cooling coil and remote compressor/condensing unit.

– Packaged Multizone with Furnace• Packaged direct expansion cooling system with combustion furnace. System includes a constant volume fan/distribution system serving

multiple zones, each with its own thermostat. Warm and cold air are mixed for each zone to meet thermostat control requirements.

Building HVAC Systems (Primary and Secondary Building Systems)

AHU

Buildingenvelope

Cooling(chiller)

(or Gas)

Electricity

Gas

Heating(boilers)

Fresh air For ventilation

Distribution systems

Air transport

Secondary systems

Primarysystems

AHU – Air Handling Unit

HVAC systems affect the energy efficiency of the building as much as the building envelope

Integration of HVAC and building physics models

Building Heating/Cooling System Plant

Building Heating/Cooling System Plant

Load System Plant model

Integrated models

Qbuiolding Q

including

Ventilation

and

Dehumidification

Example of System Models:Schematic of simple air handling unit (AHU)

rmSfans

cooler heater

mS

QC QH

wO wS

TR

room TR

Qroom_sensibel

(1-r)mS mS

wM

wR

Qroom_latent

TSTO

wR

TM

Tf,inTf,ou t

m - mass flow rate [kg/s], T – temperature [C], w [kgmoist/kgdry air], r - recirculation rate [-], Q energy/time [W]

Mixing box