Lecture 23: Primary System Loops and Components

Material prepared by GARD Analytics, Inc. and University of Illinoisat Urbana-Champaign under contract to the National Renewable Energy

Laboratory. All material Copyright 2002-2003 U.S.D.O.E. - All rights reserved

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Purpose of this Lecture

Gain an understanding of: EnergyPlus loop controls Some of the many EnergyPlus plant

and condenser components

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Keywords Categories Covered in this Lecture

Plant Loop and Condenser LoopPlant Operation Schemes,

Cooling/Heating Load Range Based Operation, Load Range Equipment List

CoilPumpBoilerChillerCooling TowerCurve

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Plant Loop

IDD Description:PLANT LOOP, A1 , \field Plant Loop Name A2 , \field Fluid Type (Water) A3 , \field Plant Operation Scheme List Name A4 , \field Loop Temperature Setpoint Schedule Name N1 , \field Maximum Loop Temperature in C N2 , \field Minimum Loop Temperature in C N3 , \field Maximum Loop Volumetric Flow Rate in m3/s N4 , \field Minimum Loop Volumetric Flow Rate in m3/s N5, \field volume of the plant loop in m3 A5, \field Plant Side Inlet Node Name A6, \field Plant Side Outlet Node Name A7, \field Plant Side Branch List Name A8, \field Plant Side Connector List Name A9, \field Demand Side Inlet Node Name A10, \field Demand Side Outlet Nodes Name A11, \field Demand Side Branch List Name A12, \field Demand Side Connector List Name A13; \field Load Distribution Scheme (Optimal|Sequential)

Control information

Flow and temperature limits for both sides of the loop

Supply side nodes, branches, and connectionsDemand side nodes, branches, and connectionsControl information

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Plant Loop Limits

Provides upper and lower boundaries for temperature and flow rate

Pump will operate within this range of flows (pump controls actual flow rate)

Loop will not be allowed to vary temperature beyond temperature limits

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Plant Loop Controls: Temperature

Setpoint temperature for plant loop can be scheduled

Plant loop will run equipment as needed and as defined by the remaining controls to meet setpoint temperature

If not enough equipment capacity, loop setpoint temperature may not be met (can “catch-up” in future time steps)

Pump controls will determine loop flow rate

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Plant Loop Controls: Load Distribution

Sequential Sequential simply operates equipment in a serial

manner based on the loop operation scheme (which assigns priority to different equipment on the loop)

When highest priority equipment is out of capacity, next highest priority equipment tries to meet the load, etc.

Optimal Parallel operation of equipment Tries to find an “optimal” balance of the plant loop

load between equipment based on the operating characteristics of the equipment on the loop

Not a strict optimization, simply an approximation at what might be the best load distribution from an energy perspective

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Plant Loop Controls: Operation Scheme

List of load ranges that define which equipment might try to meet a load

Requires following input: Plant Operation Schemes—a list of load range

definitions and the schedules for when they are in effect

Cooling/Heating Load Range Based Operation—a list of load ranges and the lists of equipment that are operating for those ranges

Load Range Equipment List—the equipment lists referenced by the load ranges

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Plant Loop Controls: Operation Scheme Example

PLANT OPERATION SCHEMES, CW Loop Operation, !- Plant Operation Scheme Name LOAD RANGE BASED OPERATION, !- KEY--Control Scheme 1 Peak Operation, !- Control Scheme Name 1 On Peak, !- Control Scheme Schedule 1 LOAD RANGE BASED OPERATION, !- KEY--Control Scheme 2 Off Peak Operation, !- Control Scheme Name 2 Off Peak; !- Control Scheme Schedule 2

COOLING LOAD RANGE BASED OPERATION, Peak Operation, !- Name 0, !- Load Range Lower Limit 1 {W} 70000, !- Load Range Upper Limit 1 {W} Chiller Plant, !- Priority Control Equip List Name 1 70000, !- Load Range Lower Limit 2 {W} 245000, !- Load Range Upper Limit 2 {W} Chiller Plant and Purchased, !- Priority Control Equip List Name 2 245000, !- Load Range Lower Limit 3 {W} 500000, !- Load Range Upper Limit 3 {W} Purchased Only; !- Priority Control Equip List Name 3

COOLING LOAD RANGE BASED OPERATION, Off Peak Operation, !- Name 0, !- Load Range Lower Limit 1 {W} 900000, !- Load Range Upper Limit 1 {W} All Chillers; !- Priority Control Equip List Name 1

Referenced in Plant Loop input

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Plant Loop Controls: Operation Scheme Example

LOAD RANGE EQUIPMENT LIST, Chiller Plant, !- Equip List Name CHILLER:CONST COP, !- KEY--Plant Equip 1 Type Little Chiller; !- Equip Name 1

LOAD RANGE EQUIPMENT LIST, Chiller Plant and Purchased, !- Equip List Name CHILLER:ELECTRIC, !- KEY--Plant Equip 1 Type Big Chiller, !- Equip Name 1 Purchased:Chilled Water, !- KEY--Plant Equip 2 Type Purchased Cooling; !- Equip Name 2

LOAD RANGE EQUIPMENT LIST, Purchased Only, !- Equip List Name Purchased:Chilled Water, !- KEY--Plant Equip 1 Type Purchased Cooling; !- Equip Name 1

LOAD RANGE EQUIPMENT LIST, All Chillers, !- Equip List Name CHILLER:ELECTRIC, !- KEY--Plant Equip 1 Type Big Chiller, !- Equip Name 1 CHILLER:CONST COP, !- KEY--Plant Equip 2 Type Little Chiller; !- Equip Name 2

Load Range Equipment Lists referenced on previous slide

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Example: Plant Loop

PLANT LOOP, Chilled Water Loop, !- Plant Loop Name Water, !- Fluid Type CW Loop Operation, !- Plant Operation Scheme List Name CW Loop Temp Schedule, !- Loop Temperature Setpoint Schedule Name 98, !- Maximum Loop Temperature {C} 1, !- Minimum Loop Temperature {C} 0.0011, !- Maximum Loop Volumetric Flow Rate {m3/s} 0, !- Minimum Loop Volumetric Flow Rate {m3/s} autosize, !- volume of the plant loop {m3} CW Supply Inlet Node, !- Plant Side Inlet Node Name CW Supply Outlet Node, !- Plant Side Outlet Node Name Cooling Supply Side Branches, !- Plant Side Branch List Name Cooling Supply Side Connectors, !- Plant Side Connector List Name CW Demand Inlet Node, !- Demand Side Inlet Node Name CW Demand Outlet Node, !- Demand Side Outlet Nodes Name Cooling Demand Side Branches, !- Demand Side Branch List Name Cooling Demand Side Connectors, !- Demand Side Connector List Name Optimal; !- Load Distribution Scheme

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Coils

COIL:Water:SimpleCoolingCOIL:Water:SimpleHeatingCOIL:Electric:HeatingCOIL:Gas:HeatingCOIL:Water:DetailedFlatCoolingCOIL:DX:Cooling Bypass Factor-

Empirical Includes the condensing unit

COIL:DX:Heating-Empirical

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Coil - Example

Supply Fan

ZONE1

Reheat CoilZone 1

Zone 1 ReheatAir Outlet Node

Zone 1 ReheatAir Inlet Node Zone 1 Reheat Water

Inlet Node

Zone 1 Reheat WaterOutlet Node

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Coil – Example (cont’d)

COIL:Water:SimpleHeating, Reheat Coil Zone 1, !Name of coil FanAndCoilAvailSched, !Coil Schedule 400.0, !UA of the Coil 1.3, !Max Water Flow Rate of Coil kg/sec Zone 1 Reheat Water Inlet Node, Zone 1 Reheat Water Outlet Node, !Coil Water Side Inlet & Outlet Node Zone 1 Reheat Air Inlet Node, Zone 1 Reheat Air Outlet Node; !Coil Air Side Inlet & Outlet Node

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Pump – Example

CW Supply Inlet Node

CW Pump Outlet Node

Circ Pump

Chiller 1 Chiller 2

Cond. Demand Side Loop

Plant Supply SideCooling Loop

Plant Demand SideCooling Loop

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Pump – Example (cont’d)

PUMP:CONSTANT SPEEDPUMP:VARIABLE SPEED PUMP:VARIABLE SPEED, CW Circ Pump, !- Pump Name CW Supply Inlet Node, !- Inlet_Node CW Pump Outlet Node, !- Outlet_Node .0013, !- Rated Volumetric Flow Rate {m3/s} 300000, !- Rated Pump Head {Pa} 560, !- Rated Power Consumption {W} .87, !- Motor Efficiency 0.0, !- Fraction of Motor Inefficiencies to Fluid Stream 0, !- Coefficient1 of the Part Load Performance Curve 1, !- Coefficient2 of the Part Load Performance Curve 0, !- Coefficient3 of the Part Load Performance Curve 0, !- Coefficient4 of the Part Load Performance Curve 0, !- Min Flow Rate in variable flow capacity;{m3/s} INTERMITTENT; !- Pump Control Type

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Boilers

BOILER:SIMPLEWATERHEATER:SIMPLE

Storage tank Heat recovery

PURCHASED:HOT WATER

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Boiler - Example

Boiler

BoilerInlet Node

BoilerOutlet Node

Plant Supply SideHeating Loop

Plant Demand SideHeating Loop

±HW Pump

Heating Coil

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Boiler – Example (cont’d)

BOILER:SIMPLE, Boiler Plant Boiler,! Boiler Name GAS, ! Fuel Type 25000, ! Nominal Capacity {W} 0.8, ! Theoretical Boiler Efficiency 100, ! Design Boiler Water Outlet Temp {C} 0.0021, ! Max Design Boiler Water Flow Rate {m3/s} 0.10, ! Minimum Part Load Ratio 1.00, ! Maximum Part Load Ratio 1.00, ! Opt Part Load Ratio 1.0, ! Coefficient1 of the fuel use/part load ratio curve 0.0, ! Coefficient2 of the fuel use/part load ratio curve 0.0, ! Coefficient3 of the fuel use/part load ratio curve Boiler Inlet Node, ! Boiler_Water_Inlet_Node Boiler Outlet Node, ! Boiler_Water_Outlet_Node 100, ! Temp Upper Limit Water Outlet {C} ConstantFlow; ! Boiler Flow Mode (v1.0.1)

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Chillers

CHILLER:ELECTRICCHILLER:GAS TURBINECHILLER:ABSORPTIONCHILLER:GAS ABSORPTION

Direct-Fired Gas Absorption Chiller-HeaterCHILLER:CONST COPCHILLER:ENGINEDRIVENPURCHASED:CHILLED WATER

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Chiller – Example

Chiller

Chiller Inlet Node

Chiller Outlet Node

Chiller CondenserInlet Node

Chiller CondenserOutlet Node

Condenser DemandSide Loop

Plant Supply SideCooling Loop

CW PumpPlant Demand Side

Cooling Loop

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Chiller – Example (cont’d)

CHILLER:ELECTRIC, Big Chiller, !- Chiller Name WATER COOLED, !- Condenser Type 100000, !- Nominal Capacity {W} 2.75, !- COP Big Chiller Inlet Node, !- Plant_Side_Inlet_Node Big Chiller Outlet Node, !- Plant_Side_Outlet_Node Big Chiller Condenser Inlet Node, !- Condenser_Side_Inlet_Node Big Chiller Condenser Outlet Node, !- Condenser_Side_Outlet_Node .15, !- Minimum Part Load Ratio 1.0, !- Maximum Part Load Ratio .65, !- Opt Part Load Ratio 35.0, !- Temp Design Condenser Inlet {C} 2.778, !- Temp Rise Coefficient 6.67, !- Temp Design Evaporator Outlet {C} 0.0011, !- Design Evaporator Vol Water Flow Rate {m3/s} (v1.0.1) 0.0011, !- Design Condenser Volumetric Water Flow Rate

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Chiller – Example (cont’d)

21 2 3temp tempAvailToNominalCapacityRatio C C C

21 2 3FullLoadtoPowerRatio C C AvailToNominalCapRatio C AvailToNominalCapRatio

21 2 3FracFullLoadPower C C PartLoadRatio C PartLoadRatio

0.9949, !- Coefficient1 of the capacity ratio curve-0.045954, !- Coefficient2 of the capacity ratio curve-0.0013543, !- Coefficient3 of the capacity ratio curve 2.333, !- Coefficient1 of the power ratio curve-1.975, !- Coefficient2 of the power ratio curve 0.6121, !- Coefficient3 of the power ratio curve 0.03303, !- Coefficient1 of the full load ratio curve 0.6852, !- Coefficient2 of the full load ratio curve 0.2818, !- Coefficient3 of the full load ratio curve 5; !- Temp Lower Limit Evaporator Outlet {C} ConstantFlow; !- Chiller Flow Mode (v1.0.1)

COP

QPowerRatioFullLoadtoadPowerFracFullLoPower evaporator

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Cooling Tower – Example

Condenser TowerInlet Node

Condenser TowerOutlet Node

Tower

Cond Demand Side Loop

Plant Supply SideCooling Loop

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Cooling Tower – Example (cont’d)

COOLING TOWER:TWO SPEEDCOOLING TOWER:SINGLE SPEED

2 Input Methods UA and Design Water Flow Rate

COOLING TOWER:SINGLE SPEED, Big Tower1, !- Tower Name Condenser Tower 1 Inlet Node, !- Water Inlet Node Name Condenser Tower 1 Outlet Node, !- Water Outlet Node Name .0011, !- Design Water Flow Rate {m3/s} 8.0, !- Design Air Flow Rate {m3/s} 500, !- Fan Power at Design Air Flow Rate {W} 175.0, !- Tower UA Value at Design Air Flow Rate {W/K} 0.0, !- Air Flow Rate in Free Convection Regime {m3/s} 0.0, !- Tower UA Value at Free Convection Air Flow Rate {W/K} UA and Design Water Flow Rate; !- Tower Performance Input Method

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Cooling Tower – Example (cont’d)

2 Input Methods (Cont.) Nominal Capacity

COOLING TOWER:SINGLE SPEED, Big Tower1, !- Tower Name Condenser Tower 1 Inlet Node, !- Water Inlet Node Name Condenser Tower 1 Outlet Node, !- Water Outlet Node Name , !- Design Water Flow Rate {m3/s} autosize, !- Design Air Flow Rate {m3/s} 500, !- Fan Power at Design Air Flow Rate {W} , !- Tower UA Value at Design Air Flow Rate {W/K} 0.0, !- Air Flow Rate in Free Convection Regime {m3/s} 0.0, !- Tower UA Value at Free Convection Air Flow Rate {W/K} Nominal Capacity, !- Tower Performance Input Method 20438., !- Tower Nominal Capacity {W} 0.; !- Tower Free Convection Capacity {W}

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Curve Objects

CURVE:CUBICCURVE:QUADRATICCURVE:BIQUADRATIC CURVE:BIQUADRATIC, Sample Curve, !- Name 1.000, !- Coeff1 Constant 0.100, !- Coeff2 x 0.001, !- Coeff3 x**2 0.200, !- Coeff4 y 0.002, !- Coeff5 y**2 0.003, !- Coeff6 x*y 0, !- minimum value of x 100, !- maximum value of x 0, !- minimum value of y 100; !- maximum value of y

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Summary

Each component on the primary system loops has specific input requirements that are unique to that component type

Some components may link between two different loops, for example: Coils—air/zone equipment loop and plant

demand side Chiller—plant supply side and condenser

demand sidePrimary loops have temperature, flow,

and operational controls that must be defined by the program user