Seminar Meeting 11/2013

Christopher PriceComponent Level HVAC Control

NIST Project

Overview

• Motivation• Background• Cascaded Control• Air Volume Systems• Hydronic Radiators• Future Work

Motivation

• DMPC Control Project (NIST)–Advanced control algorithms to

generate system set points–Reduced energy consumption and

cost through improved efficiency–Full energy savings when

components have adequate tracking

Motivation

• Where I Fit

Background

• Vapor Compression Cycle

(2010) Eliot & Rasmussen: On Reducing Evaporator Superheat Nonlinearity

Background

• Expansion Valves

http://image.ec21.com/image/zjwanjie/OF0008152543_1/Sell_capillary_tube_with_nut.jpg

Capillary Tube

http://neilorme.com/pics/aev1.jpg

http://www.swtc.edu/Ag_Power/air_conditioning/lecture/expansion_valve.png

Automatic Expansion

ValveThermostatic

Expansion Valve

Background

• Hybrid Expansion Valve

(2009) Eliot & Rasmussen: Evaporator Superheat Regulation Via Emulation of Semi-Active Flow Control

Cascaded Control

• Block Diagram

Cascaded Control

Valve Position to Mass Flow

Mass Flow to Pressure

Mass Flow to

Superheat

(2009) Eliot & Rasmussen: Evaporator Superheat Regulation Via Emulation of Semi-Active Flow Control

Air Volume Systems

• Apply same control idea to air handlers

• Two main types:–Constant Volume Systems

• Flow rate constant, temperature varied

–Variable Air Volume Systems*• Varied flow rate, temperature

constant

VAV Systems

• Schematic

VAV Systems

• Damper Types

2009 ASHRAE Handbook FundamentalsArrow United Industries

Parallel Blade

Opposed Blade

Single Blade

VAV Systems

• Damper Characteristics

2009 ASHRAE Handbook Fundamentals

Parallel Blade

Opposed Blade

VAV Systems

• Traditional PID vs. Cascaded Control

VAV Systems

• Simulation Model

• Damper Model

(2010) Yamakawa: Compensation of Manual Reset for PID Controller

VAV Systems – Traditional PID Control

VAV Systems – Cascaded Control

PID Control Cascaded Control

Case MAE RMS Case MAE RMS

20% 0.4461 0.1239 Low Flow 0.743 0.263

35% 0.4274 0.1052 Mid Flow 0.351 0.097

50% 0.8246 0.2489 High Flow 0.268 0.047

80% 1.9682 0.5446

Hydronic Radiators

• Shown cascaded control works for refrigerant and air mediums

• Apply control design to water radiator systems

• Currently working on validating results from Tahersima 2013 paper

Hydronic Radiators

• Equations–Radiator:

–Room:

–Valve:

(2013) Tahersima: Analytical Solution for Stability-Performance Dilemma for Hydronic Radiators

Hydronic Radiators

• Motivation

(2013) Tahersima: Analytical Solution for Stability-Performance Dilemma for Hydronic Radiators

Future Work

• Study the effect of sampling rate on performance of cascaded loop

• Proper tuning of cascaded loop control• Application of cascaded control to

positive displacement components (fans/pumps)

• Alternate control structures (e.g. feed forward control)

Questions?