Optimization and sequencing of chilled-water plant based on extremum seeking control

2016 ◽  
Author(s):  
Baojie Mu ◽  
Yaoyu Li ◽  
Timothy I. Salsbury ◽  
John M. House
Keyword(s):  
Extremum Seeking ◽  
Extremum Seeking Control ◽  
Water Plant ◽  
Chilled Water

A Multivariable Newton-Based Extremum Seeking Control for Condenser Water Loop Optimization of Chilled-Water Plant

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Baojie Mu ◽  
Yaoyu Li ◽  
John E. Seem ◽  
Bin Hu
Keyword(s):  
Power Efficiency ◽  
Cooling Tower ◽  
Water Flow Rate ◽  
Extremum Seeking ◽  
Total Power ◽  
Feedback Signal ◽  
Efficient Operation ◽  
Extremum Seeking Control ◽  
Water Plant ◽  
Chilled Water

This paper presents a multivariable Newton-based extremum seeking control (ESC) scheme for efficient operation of a chilled-water plant. A modelica-based dynamic simulation model of the chilled-water plant consists of one screw chiller and one counter-flow cooling tower was adopted for evaluation of proposed two-input Newton-based ESC controller. The ESC controller takes the total power of the chiller compressor, the cooling-tower fan, and the condenser water (CW) pump as feedback signal and discovers the optimum outputs of cooling-tower fan speed and the condenser-loop water flow rate to maximize the power efficiency in real time with the cooling load being satisfied. Remarkable energy saving is observed for several testing conditions.

A Multi-Variable Newton-Based Extremum Seeking Control for a Chilled Water Plant With Variable Water and Air Flow

2014 ◽  
Author(s):  
Baojie Mu ◽  
Yaoyu Li ◽  
Bin Hu ◽  
John E. Seem
Keyword(s):  
Energy Saving ◽  
Power Efficiency ◽  
Cooling Tower ◽  
Water Flow Rate ◽  
Extremum Seeking ◽  
Total Power ◽  
Extremum Seeking Control ◽  
Model Free ◽  
Water Plant ◽  
Chilled Water

The chilled water system, typically consisting of chiller and cooling tower, plays a major role in the ventilation and air-conditioning systems in commercial buildings. Due to the significant power consumption of such system, improvement of its efficiency would lead to significant benefit in energy saving. As the system characteristics and operational conditions can vary dramatically in practice, model-free self-optimizing control is of high interest in practice. In this study, the chilled-water plant being studied consists of one screw chiller and one counter-flow cooling tower. A multi-variable Newton-based extremum seeking control (ESC) scheme is applied to maximize the power efficiency in real time with the cooling load being satisfied. The feedback for the ESC controller is the total power of the chiller compressor, the cooling tower fan and the condenser water pump, while the inputs are cooling-tower fan speed and the condenser-loop water flow rate. The two-input Newton-based ESC controller is simulated with a Modelica based dynamic simulation model of the chiller-tower system. Two inner-loop PI controllers are used to regulate the temperatures of evaporator superheat and evaporator leaving water at their respective setpoints. Simulation results validate the effectiveness of the proposed control strategy. Remarkable energy saving is observed for several testing conditions.

Extremum Seeking Based Control Strategy for a Chilled-Water Plant With Parallel Chillers

2015 ◽  
Author(s):  
Baojie Mu ◽  
Yaoyu Li ◽  
Timothy I. Salsbury ◽  
John M. House
Keyword(s):  
Control Strategy ◽  
Cooling Tower ◽  
Input Saturation ◽  
Extremum Seeking ◽  
Total Power ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Water Plant ◽  
Total Power Consumption ◽  
Chilled Water

Chilled-water plants with multiple chillers are the backbone of ventilation and air conditioning (VAC) systems for commercial buildings. A penalty function based multivariate extremum seeking control (ESC) strategy is proposed in this paper for maximizing the energy efficiency in real time for a variable primary flow (VPF) chilled-water plant with parallel chillers. The proposed ESC algorithm takes the total power consumption (chiller compressors + cooling tower fan + condenser water pumps + penalty terms if inputs saturation occurs) as feedback, and tower fan air flow, condenser water flows and evaporator leaving chilled-water temperature setpoint as plant inputs (ESC outputs). A band-pass filter array is used in place of the conventional high-pass filter at the plant output so as to reduce the cross-channel interference. Chiller sequencing is also enabled with input saturation related signals. A Modelica based dynamic simulation model is developed for a chilled-water plant with two parallel chillers, one cooling tower, one air-handling unit and one zone. Simulation results under several testing conditions validate the effectiveness of the proposed model-free control strategy, as well as the significant energy saving.

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