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

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

Life Cycle Cost Analysis Engineering economics

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

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

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

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

eQUEST HVAC Models

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)

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

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]

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

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)

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: