Modeling, optimization, and control of ship energy systems using exergy methods

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Department of Mechanical Engineering-Engineering Mechanics


Changing emissions regulations, fuel price fluctuations and development of new energy-intensive mission systems are driving both component technological innovation and require more sophisticated controls on-board modern ships. Historically, numerous components and systems aboard ships perform energy conversions from one form to another. Conversion from chemical to thermal to kinetic to electrical and back to thermal energy are common. Today, subsystems are designed separately without opportunity for optimizing overall system-of-systems performance. By modeling multiple system domains simultaneously and applying the Second Law of Thermodynamics, this progresses towards overall ship system optimization. Exergy, the available energy for performing useful work, and exergy destruction was calculated in each energy conversion process. Knowledge of the exergy flows leads to a system-of-systems optimization to minimize overall exergy destruction translating into lower emissions and fuel costs. This can eventually result in more efficient, smaller and lighter shipboard systems. A model of notional shipboard power and cooling system is presented that features a pulsed load (an electromagnetic railgun) and have implemented both traditional and exergy-based control schemes. This paper will briefly review the modeling, which has been previously published, and present results using exergy destruction for optimization of the ship system controls.

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