1. Lecture Objectives: Discuss Final Project
Parametric Analyses
Life Cycle Cost Assessment
Format
Answer eQUEST related question
Continue with HVAC systems
Differences between typical systems
Setpoint
Modeling

2. What are the reasons for energy simulations?
System Development (research)
Building design (evaluate different design solutions)
Economic benefits
Budget planning

3. Life Cycle Cost Analysis
Engineering economics

4. Parameters in life cycle cost analysis
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

5. Example
Using eQUEST analyze the benefits (energy saving and pay back period)
of installing
- low-e double glazed window
- variable frequency drive
in the school building in NYC

7. Building Envelope vs. HVAC System
Load - System - Plant Model
Building
Qbuiolding
Heating/Cooling
System Q
including
Ventilation
and
Dehumidification
Plant
Electric
Energy
Gas

8. Building HVAC Systems (Primary and Secondary Building HVAC Systems)
AHU – Air Handling Unit
Distribution
systems
Fresh air
for ventilation
AHU
Primary
systems
Air transport
Electricity
Secondary
systems
Cooling
(chiller)
Heating
(boilers)
Building
envelope
HVAC systems affect the energy efficiency of
the building as much as the building envelope.
In many situation even more!
(or Gas)
Gas

9. eQUEST HVAC Models

10. Example of a Plant System (Chilled Water System)
Air cooled chiller
Chiller with a cooling tower
COP ~ 3
COP ~ 5
COP = Cooling Energy / Electric Energy ( same units)

11. Two Basic Approaches for Modeling of HVAC and Building Envelope
Load System Plant model
Building
Qbuiolding
Heating/Cooling
System Q
including
Ventilation
and
Dehumidification
Plant
Integrated models
Building
Heating/Cooling
System
Plant

12. Example of a HVAC Model 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]

13. Example of a 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

14. Plant model Refrigeration Cycle
Released energy
(condenser)
T outdoor air
T cooled water
- What is COP?
- How the outdoor air temperature
affects chiller performance?
Cooling energy (evaporator)

15. Chiller model: COP= f(TOA , Qcooling , chiller properties)
Chiller data: QNOMINAL nominal cooling power,
PNOMINAL electric consumption for QNOMINAL
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
Percentage of load:
The coefficient of performance under any condition: