demand controlled ventilation with demand based scheduling: campus applications
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Demand Controlled Ventilation with Demand Based Scheduling: Campus Applications. Deep Energy Efficiency. Demand Controlled Ventilation. Controlling the amount of ventilation to a space based on demand - PowerPoint PPT PresentationTRANSCRIPT
Deep Energy Efficiency
Demand Controlled Ventilation with Demand
Based Scheduling: Campus Applications
Demand Controlled Ventilation
Controlling the amount of ventilation to a space based on demand
Reset based on occupancy: Use carbon dioxide sensors to track space CO2 levels and raise lower supply fan airflow to maintain <700ppmReset based on economizer operation: Lower supply fan airflow based on percentage of outside air in supply air mix
Occupancy sensorsDetermine physical presence of people
CO2 sensorsDetermine quality of air in spaceLocated in return air duct or in conditioned space
Temperature sensorsDetermine whether space needs to be cooled/heated
Variable Speed DrivesAllow a proportional rate of airflow to space based on demand
Control EquipmentUse sensors to determine space need and operate equipment efficientlyGraphical building control systemEffective sequence of operation
Buildings designed before 2001Large spaces with dedicated air handling unitsHigh operating hours/Low usage/Dense occupancySpaces that have wide weekly operating schedules and highly variable actual usage
Performance spacesArt/Music StudiosLecture hallsLarge ClassroomsAuditoriumsComputer LabsMulti-purpose RoomsDining Areas
Potential DCV Retrofit Applications
Problem:UCSC facility staff were aware of building equipment that was running when spaces were not occupied
HolidaysClass scheduling changes and reductions to spacesFaculty / Researchers demanded spaces be accessible during a wide range of hours
Legacy building control systems could not be modified quickly and easily
Solution: Demand Based Scheduling
Retrofit legacy BMS controllersInstall Occupancy and CO2 sensorsIf CO2 levels are below setpointAnd temperature is within desired rangeAnd occupancy sensors indicate empty spaceShut off equipment
Demand Based Scheduling
Demand Based Scheduling
Turning OFF air handling equipment whenCO2 levels are below 700ppm ANDSpace is unoccupied ANDTemperature of space is between 64-80 deg F
Sequence of Operation
3 modes of building equipment operation
Occupied Mode: regular building occupancy scheduled hours. Occupancy sensors sense space occupancy. Equipment ONUnoccupied Mode: regular building unoccupied schedule hours. Equipment OFFStandby Mode: regular building occupied hours, space is unoccupied, CO2 and temperature is within desired range. Equipment OFF or at reduced operation
Energy Benefits
Electrical Savings:Variable airflow results in exponential electrical reductionLower equipment runtimeReduce airflow when economizer is in free cooling modeReduced cooling from reduced volume of air to coolReduced cooling from temperature setback (standby mode)
Natural Gas Savings:Reduced heating from temperature setbackReduced heating from reduced volume of air to heat
UCSC Theatre Arts Complex
Annual Energy Savings200,337 kWh28.4 kW15,062 therms
Demand Controlled VentilationDemand Based SchedulingTimer Switches on Fan Coil Units
UCSC Theatre Arts Complex
Main Stage and Second Stage Occupant wanted broad access, but actual usage of
space is low7 days/week, 8am-11pmSpecial Events: Theatre PerformancesHighly variable actual occupancyAirflow rates designed for peak capacity (performances)
Performance StudiosMultiple spaces with operable
windows and dedicated FCUs.7 days/week, 8am-11pmVariable actual occupancyOccupant need for conditioned
air was low
Engineering 2 Auditorium
Building built in 2004Designed and constructed with DCVTrending of system determined that
DCV was not operation correctlyModified sequence to include demand
based schedulingResolved over pressurization issues
by reducing supply fan airflow and maintaining CO2 levels
Engineering 2 Auditorium pre vs.
post kW trending
Red line shows kW profile before commissioning
Blue line shows kW profile after commissioning
Social Sciences 1
Annual Energy Savings73,286 kWh17.64 kW1,124 therms
Demand Based SchedulingZone Level DCV
Zone Level DCV1) Occupancy Sensor goes
unoccupied2) VAV goes to min position3) Main Supply/Return fan
slow down as VAVs close
Soc Sci 1: Room 110
Exterior classroom with dedicated Air Handling Unit
Weekly schedule: 530am-1100pm,7 days/week
Original BMS didn’t allow for simple schedule modifications
Installed occupancy sensors and changed sequence of operations
June 2011:Scheduled Hours: 525 hoursActual Hours: 78 hours
Reduced hours of operation by 85%
Science & Engineering Library Computer Lab
Annual Energy Savings35,066 kWh2.4 kW
DCV and Demand Based Scheduling
Sci & Eng Library Computer lab
*Implemented measures a a part of Monitored Based Commissioning Project (MBCx)*Computer lab has dedicated AHU that ran 24/7*During academic breaks, building was open for staff but
computer lab was closed*Allowed HVAC operation of computer lab during extended
hours*CO2 levels trigger AHU during non-scheduled hours
Lessons Learned
Sequence of operation needs to be commissioned. If too complex or mis-programmed, DCV will not be effective
CO2 sensors need to be appropriately placed. If system shuts off during standby mode, CO2 sensors MUST be placed in space, not return air duct
Integration of lighting and HVAC optimizes retrofit