Increasing Ship Power System Capability through Exergy Control
Abstract
The exergy coupling of ship subsystems can take several forms: electrical, mechanical, thermal,and chemical to name a few. The focus of this work is on the electrical, electrical-mechanical, andthermal system loads, including those derived from achieving thermal management requirements.This is also one of the least developed areas in the field of exergy control, but it could havesignificant impact in ship applications. Our approach requires (1) developing exergy flow modelsfor coupled electrical/mechanical/thermal systems (2) creating optimal feedforward and feedbackcontrol schemes based on the nonlinear model forms and (3) devising a method to map exergycontrol results to ship-relevant attributes such as subsystem mass, volume and energy storage aswell as energy efficiency, minimal exergy destruction, and optimal information flow. Ourapproach is to develop exergy potential and irreversible entropy production functions that can beused in a variational approach to model generation. Feedforward control will be based onminimizing exergy destruction assuming a complete understanding of the models while thefeedback control will focus on shaping the exergy surface as well as manipulating the exergy flowsto produce a meta-stable closed loop system with specifiable transient performance. Mappingcontrol performance to ship attributes will be based on stability criteria, physics-based andheuristic component models, depending on the specific metric being addressed. Throughout thisprocess a representative simplified ship model, called the Exergy Control Challenge Problem will6 of 15be used to both guide the exergy model creation and assess the exergy control system~sperformance.The Exergy Control Challenge Problem, shown in Figure 1, contains several coupled subsystemsthat all tie back to the ship~s electrical power grid. A turbine generator supplies power to theelectrical bus that has three explicit electrical loads: (1) ship service, (2) chiller system pumps, (3)a pulsed power device. A bus-level energy storage system is included primarily to accommodatethe pulsed power load. All of the electrical loads, the energy storage system, and the generatordissipate heat via the ship~s cooling system and thus are coupled implicitly to the electrical busthrough the chiller~s electrical load. Also, we will evaluate non-traditional energy storage systemssuch as HVAC thermal capacity of living spaces to enable load control with respect to the MVDCsystems.The model will be created using MathWork~s Simulink using components that can be readily usedfor hardware-in-the-loop simulation via the Simulink Coder Toolbox. This will allow not only astaged model evolution during this project but also researchers for other organizations to use themodel for related studies. In year two, the model will be expanded to include multiple generationsources and zones. While most of the model components can be constructed from existingSimulink elements, the exergy rate models do not exist. These will be developed and implementedas c-coded S-Functions, which will permit their use in Simulink Coder. The exergy rate equationswill also form the core of the model-based feedforward and feedback exergy control schemesdiscussed below.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 23, 2016
- Source ID
- N000141613044
Entities
People
- Gordon Parker
Organizations
- Michigan Technological University
- Office of Naval Research
- United States Navy