• Programmable Controllers (Open loop or closed loop) Lighting timers (open loop) Lighting controllers with sensors (closed loop) Demand limiters (closed loop) Temperature, pressure, level, flow, etc (all closed loop)• Energy Management Computer Control Systems Level 1, Level 2, Level 3, Level 4
Basic Closed Loop Automatic Control Systems (Feedback Control Systems)1. Basic aspects of closed loop – or feedback control systems – for maintaining a physical variable such as temperature, pressure, humidity, flow, etc at a specified value.2. Elements of a closed loop feedback control system: Sensors Controllers Actuators Controlled devices
Block diagram, Closed loop Controller Control deviceSetpoint Set point + Compn- Actuator Valve Process converter sation unit _ Sensor
Diagram of a Feedback Control System CONTROLLER SET POINT RC CONTROLED DEVICE SENSOR T AIR FLOW HEATING COIL
Control Modes• Two position control system • The system (e.g. a heater) is either OFF or ON. • Accomplished with a relay whose contacts are either open or closed, or a valve whose stem position is either open or closed.
Control Modes• Proportional control system • A variation from the set point produces a proportional movement in the actuator. • Pneumatic controls vary the air pressure. • Electric controls use a potentiometer (a type of variable resistor).
Control Technologies• Pneumatic• Electric• Direct Digital Control
Pneumatic Controls• Use compressed air to operate the control system.• Require the use of very clean, dry and oil-free air.• Have been used in many HVAC applicationsAdvantages• Are well understood by designers and maintenance people• Are inherently proportional, inexpensive and very reliable.
Pneumatic ControlsDisadvantages• Not very precise.• Required frequent calibration to achieve acceptable accuracy.• Pneumatic control algorithms are hard to change e.g. changing a P loop to a PI loop.
Electric Controls• Can be analog electric or electronic controls• Use a variable, but continuous, electrical voltage or current to operate the control system.• Transmit signals quickly and accurately.
Advantages• Can be very accurate and very stable.• Do not require field calibration, and are drift-free, if good quality sensors are used.• Relatively easy to implement proportional plus integral (PI) control electronically.Disadvantages• Often more expensive than pneumatic controls• History of reliability problems.• Difficult to easily interchange parts because of the many different systems.
Direct Digital Controls• Use electrical pulses to send signals.• Interface directly with microprocessors and microcomputers (PCs).
Advantages• Extremely flexible because the control algorithms are implemented in software instead of hardware. Changes are made by keyboard entries, not by adding or modifying hardware elements.• Very precise; recalibration is not necessary.• No controller drift.• Costs have dropped dramatically for DDC components in recent years.• Analog sensors may still require periodic recalibration, but early reliability problems have been cured.
Direct Digital ControlsDisadvantages• Not well understood by many maintenance people and facility managers.• Different programming languages also a problem. BACNET should help this concern.• BACNET: Building Automation Central Control System Network
Direct Digital Controllers Input/ OutputsDigital Inputs Examples:-Differential Pressure Switch is an example of Digital Input. Usuallyinstalled across a fan or a filter. If the contact is closed the DDCcan detect either the fan is running or the filter is clogged.Smoke Detector installed in the duct to allow the controller tostop the Air Handling Unit in case of Fire.Auxiliary contact from contactor to indicate if the contactor isenergized or NOT.
Direct Digital Controllers Input/ OutputsAnalog Inputs Example:-Temperature Sensors/ Setpoint Modules for Rooms.Temperature Sensors for Ducts.Immersion temperature Sensors for water Pipes.Humidity Transmitters for Rooms and Ducts.Differential Pressure Transmitters for CleanRooms.
Direct Digital Controllers Input/ OutputsAnalog Output Examples:-DDC produce a voltage signal ranged from 0 to 10 Volt. Accordingto the value the controlled device respond.To Control the Fan Speed via inverter (Speed Drive).To Modulate water Valve .To Modulate Damper Motor and control Air Flow.
Direct Digital Controllers Input/ OutputsDigital Output Examples:-Digital output is a relay output controlled by DDCTo Energize contactor in the motor control center in order to startFan or Pump.To Start a condensing unit when using DX AirHandling Units.To energize Heater Battery Stages via contactors
Glossary of Control Terminology
Glossary of Control Terminology• Control Point– The actual value of the controlled variable (e.g. temperature, pressure, flow, etc.).• Dead-Band—The range over which the output of the controller remains constant as the input varies, with the output changing only in response to an input outside the differential range.• Direct Acting Controller—A controller for which an increase in the level of the sensor signal (temperature, pressure, etc.) results in an increase in the level of the controller output.
Glossary of Control Terminology• Equal Percentage Valve—A valve with a plug shaped so the flow varies as the square root of the lift.• Gain—The gain of a controller is defined as the ratio of the output of the controller to the input. In a pneumatic temperature controller, for example, the gain would be expressed as: gain = Controller Output (kPa) Throttling Range (degrees)
Glossary of Control Terminology• Linear Percentage Valve—A valve which has a plug shaped so that the flow varies directly with the lift.• Modulating Controller—A type of controller for which the output can vary infinitely over the range of the controller.• Offset—The difference between the set point and the control point or the actual value of the controlled variable. This is sometimes called drift, deviation, or control point shift.
Glossary of Control Terminology• Set Point—The Value of the controlled variable that is to be maintained.• Throttling Range—The amount of change in the controlled variable required to run the actuator of the controlled device from one end of its stroke to the other end. If the actual value of the controlled variable lies within the throttling range of the controller it is said to be in control. When it exceeds the throttling range it is said to be out of control.
Control Algorithms• Proportional Control (P) With proportional control, the controller output varies in proportion to the error. The system output is: O = A + Kp × e where Kp = Proportional Gain Constant
Control Algorithms• Proportional Plus Integral Control (PI) With proportional plus integral control, an integral term is added to the output equation. The system output is: O = A + Kp × e + Ki × ∫ edt where Ki = Integral Gain Constant
Control Algorithms• Proportional Plus Integral Plus Derivative Control (PID) With PID control, a derivative—or prediction—term is added. The system output is: O = A + Kp × e + Ki × ∫ edt + Kd × de/dt where Kd = Derivative Gain Constant
Energy Consumption (per Sector) ● Energy use split 37% 35% 10% Industry Building Government & shops • Main energy consumption is for motors, cooling, lighting, electronics and appliances
Solutions for Building and Industry SectorEnabling products Buildings & Industy Renovation can yield up to – Variable speed drives for HVAC, pumps, 30% of energy savings fans, motors Building management Power factor systems correction – Power compensation and filtering products – Dimmers, timers, movement and presence detectors, switches. – Thermostat for climate controlManagement systems HVAC control Climate control Lighting control – Building management systems – Power management systems
Energy Efficiency Improvement Steps1 Measure2 Fix the basics3 Automate4 Monitor and Improve
1 Measure ●Energy meters What we can not measure we can not control ●Power quality meters2 Fix the basics3 Automate4 Monitor and Improve
1 Measure 2 Fix the basics ●Power quality ●Insulation material ●Low consumption devices ●Power reliability3 Automate4 Monitor and Improve
P(kW) ϕ P(kW) Q(kvar)S(KVA) S(kVA)App.power
1 Measure2 Fix the basics 3 Automate ●Variable speed derives ●Motor control systems ●Building Management Systems4 Monitor and Improve
1 Measure 4 Monitor and Improve ●Energy management software ●Remote monitoring systems2 Fix the basics3 Automate
Building Management Systems
Centralized System HVACCar ParkManagement COMMON SITEWIDE NETWORK Intruder Energy Detection Metering Fire Alarm Lighting Control CCTV Systems Lift Monitoring Access Control Systems Systems
ISO Standard Levels Model Approved Standard System Control BACnet/LonTalk Workstation, Graphical User Management Level Interface (GUI) Main Plant, AHUs, BACnet/LonTalk Chillers, Boilers Automation Level BACnet, Terminal Units,LONTalk, EIB, VAVs, FCU’s Field LevelProfibus etc.. Heat Pumps (to be merged with Automation Level)
Distributed Energy Management System Architecture
Open Systems and multiple standards Open protocols are the basis of open systems:
Energy Management System FunctionsMonitoring/Surveillance• Building conditions• Equipment status• Utility demand• Climate data• Fire and security
Energy Management System FunctionsControl• Schedule events• Optimized start/stop• Enthalpy optimization• Boiler/chiller optimization• Temperature setback/setup
Energy Management System FunctionsDemand Limiting• Load shedding• Duty cyclingMaintenance• Remote operation and control of equipment• Generation of maintenance schedules• Diagnosing breakdowns
Energy Management System FunctionsRecord Generation• Trends and operation logs• Utility demand profile• Modification/replacement analysis• Energy conservation documentation
Power MonitoringPower Factor Demand Consumption
Peak Demand sheddingHow it contributes to Energy Efficiency? Before After
Energy Centre2 off 5MW CHP Engines2 Dual Fuel Boilers2 Heat Recovery BoilersPlant Rooms34 Air Handling UnitsChillersLPHW systemsCWS Storage TanksLife SafetySmoke ControlSprinklersEmergency Lighting BatteryChargersFire Hydrant SystemsTerminal ServicesEscalators / Auto walksLiftsPump Stations *Surface Water DrainageSewage Pump StationsFire Training GroundApron ServicesAirbridge AlarmsFEGPSubstationsHV Switchgear MonitoringMeteringStandby GeneratorsAccess Control200 DoorsAttendance monitoring
Sample of Building Management Graphical Presentation Air Handling Display
Chillier Plant Display
EMS Feature Descriptions1. Scheduled Start/Stop—Starting and stopping equipment based upon the time of day, and the day of the week.2. Optimum Start/Stop—Adjust equipment operating schedule based upon space temperature, outside air temperature, humidity, etc.3. Duty Cycling—Shutting down equipment for predetermined short periods of time during normal operating hours.
EMS Feature Descriptions4. Demand Limiting—Temporarily shedding electrical loads to prevent exceeding a peak value.5. Day/Night Setback—Lowering the space heating setpoint or raising the space cooling setpoint during unoccupied hours.6. Outside Air Economizer—Brings in outside air when the OA dry bulb temperature is less than the required mixed air temperature for the building.7. Enthalpy Economizer—Brings in outside air when the OA enthalpy is less than that of the return air.
EMS Feature Descriptions8. Warm Up/Cool Down Ventilation and Recirculation —Controls operation of the OA dampers when the introduction of OA would impose an additional thermal load during warm-up or cool-down cycles prior to occupancy of a building.
EMS Feature Descriptions10. Steam Boiler Optimization—Implemented in heating plants with multiple boilers. Boiler plant optimization is accomplished through the selection of the most efficient boiler to satisfy the space temperature requirements during the building occupied period.11. Reheat Coil Reset—Selects the zone/area with the greatest need for reheat, and establishes the minimum temperature of the heating hot water so that is is just hot enough to meet the reheat needs for that time period.
EMS Feature Descriptions12. Hot Water Boiler Optimization—Same technique as Steam Boiler Optimization.13. Hot Water OA Reset—The heating hot water temperature is reduced as the heating need for the facility decreases.14. Chiller Optimization—For facilities with multiple chillers, the most efficient chiller or chillers are selected to meet the existing load with minimum demand and or energy.
EMS Feature Descriptions15. Chiller Demand Limiting—The chiller electrical load is reduced at certain times to meet a maximum pre- specified chiller kW load.16. Lighting Control—Turns lighting off and on according to a pre-set time schedule.• Remote Boiler Monitoring and Supervision—Uses sensors at the boiler to provide inputs to the EMS for automatic central reporting of alarms, critical operating parameters, and remote shutdown of boilers.
EMS Feature Descriptions18. Maintenance Management—Provides a maintenance schedule for utility plants, mechanical and electrical equipment based on run time, calendar time, or physical parameters.19. Fire/Security Management Control—When allowed by local building codes, these functions can be combined with the Energy Management System functions in a cost effective manner.
Building Management SystemDirect Digital Controller Applications
Constant volume air handling unit with return fan,heating and cooling coils and mixed air dampers.
Constant volume air handling unit with return fan,heating and cooling coils and mixed air dampers. Equipment List Item QTY Duct Temperature Sensor 4 Modulating Valves 2 DP Switch 3 Modulating Damper Actuators 3 Duct Smoke Detector 2 RH Transmitter 2 Direct Digital Controller with 7 DI, 2 DO, 6 1 AI, 5 AO 20% Extra points is recommended
Constant volume air handling unit with return fan, heating and cooling coils and mixed air dampers. Control Sequence -1
Constant volume air handling unit with return fan, heating and cooling coils and mixed air dampers. Control Sequence -2
Constant volume air handling unit with return fan,heating and cooling coils and mixed air dampers. Control Sequence -3
Constant volume air handling unit with return fan,heating and cooling coils and mixed air dampers. Control Sequence -4
Monitors chiller loading and failure status to control a lead and lag chiller system.
Monitors chiller loading and failure status to control a lead and lag chiller system. Equipment List Item QTY Immersion Temperature Sensor 3 Water Flow Sensor 2 Direct Digital Controller with 4 DI, 4 DO, 4 1 AI. 20% Extra points is recommended