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# Announcement - PowerPoint PPT Presentation

Announcement. Lecture on Energy Plus by Wesley Cole Monday, December 1, 8 am ECJ Computer lab. Lecture Objectives:. Finish with TMY weather data Compare detailed and empirical modeling discus accuracy Show how to use life-cycle cost analysis integrated in eQUEST. TMY weather data.

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### Announcement

Lecture on Energy Plus

by Wesley Cole

Monday, December 1, 8 am

ECJ Computer lab

• Finish with TMY weather data

• Compare detailed and empirical modeling

• discus accuracy

• Show how to use life-cycle cost analysis

• integrated in eQUEST

• TMY, TMY2, TMY3

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

1991, 1992, ……………...1994, 1995

TMY3: January , February , March, ….December

Each location - different set

Building

Heating/Cooling

System

Plant

QBuilding

QSystems

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

Mixing box

m - mass flow rate [kg/s], T – temperature [C], w [kgmoist/kgdry air],

r - recirculation rate [-], Q energy/time [W]

Energy and mass balance equations for Air handling unit model – steady state case

1) The energy balance for the mixing box is:

‘r’ is the re-circulated air portion,

TO is the outdoor air temperature,

TM is the temperature of the air after the mixing box.

The air-humidity balance for the mixing box is:

wOis the outdoor air humidity ratio and

wM is the humidity ratio after the mixing box

2) The energy balance for the cooling coil is given as:

Example of Plant Models:Chiller

P electric () = COP () x Q cooling coil ()

TOA

What is COP for this

air cooled chiller ?

T Condensation = TOA+ ΔT

Evaporation at 1oC

TCWS=5oC

TCWR=11oC

water

Building users (cooling coil in AHU)

COP is changing with the change of TOA

Chiller (plant) model: COP= f(TOA , Qcooling , chiller properties)

Chiller data: QNOMINAL nominal cooling power,

PNOMINAL electric consumption forQNOMINAL

The consumed electric power [KW] under any condition

Available capacity as function of evaporator and condenser temperature

Cooling water supply

Outdoor air

Full load efficiency as function of condenser and evaporator temperature

Efficiency as function of percentage of load

The coefficient of performance under any condition:

Building

Heating/Cooling

System

Plant

QBuilding

QSystems

eQUEST

Integrated Model

Building

Heating/Cooling

System

Plant

QBuilding

QSystems

EnergyPlus

Feedback

Measured for a building in Syracuse, NY

Model

For an average year use TMY2

=835890ton hour = 10.031 106 Btu

Source of inaccuracywhen considering final results

• Assumptions related to the model

• Lack of precise input data

• Modeling software (tool) limitations

• Limitation related to available computational resources

• Result interpretations

Two options:

• Comparison with the experimental data

- monitoring

- very expensive

- feasible only for smaller buildings

2) Comparison with other energy simulation programs

- for the same input data

- system of numerical experiments

- BESTEST

Cranfield test rooms (from Lomas et al 1994a)

• System of tests (~ 40 cases)

- Each test emphasizes certain phenomena like

external (internal) convection, radiation, ground contact

• Simple geometry

• Mountain climate

COMPARE THE RESULTS

• System development

• Building design improvement

• Economic benefits (pay back period)

• Budget planning (fuel consumption)

• Example: glass facade design tool

THERM: heat thermal bridge analysis

• Your projects 1 and 2

Economic benefitsLife Cycle Cost Analysis

• Engineering economics

Energy benefits

Beside energy benefits expressed in \$,

you should consider:

• First cost

• Maintenance

• Operation life

• Change of the energy cost

• Interest (inflation)

• Taxes, Discounts, Rebates, other Government measures

• Using eQUEST analyze the benefits (energy saving and pay back period)

of installing

- low-e double glazed window

- economizer

in the school building in NYC

• System development

• Building design improvement

• Economic benefits (pay back period)

• Budget planning (fuel consumption)

Least accurate