Modelling, estimation and control of waste heat recovery and desalination processes in maritime applications

Thumbnail Image

Files

isbn9789526074870.pdf (4.29 MB)

URL

Journal Title

Journal ISSN

Volume Title

School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2017-06-20
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.

Authors

Date

2017

Department

Sähkötekniikan ja automaation laitos
Department of Electrical Engineering and Automation

Major/Subject

Mcode

Degree programme

Language

en

Pages

100 + app. 78

Series

Aalto University publication series DOCTORAL DISSERTATIONS, 115/2017

Abstract

Energy-efficient operation of ships is meaningful in maritime applications due to the finite nature of fossil fuel and in order to limit the impact on the environment. The development of waste heat recovery systems combined with control systems has contributed in the optimization of the onboard processes. However, in many scenarios, the processes are subject to numerous sources of uncertainties such as incomplete models, unknown system parameters / states, disturbances etc. that are to be incorporated appropriately. Two particular thermal systems on a ship are investigated, namely a freshwater cooling circuit on the one hand and a multistage flash evaporation plant on the other hand. The thesis is situated in the field of applied control theory with emphasis on the analysis of uncertain systems by means of modelling, estimation and control.  Due to incomplete process models of the freshwater cooling circuit, the waste heat recovery process cannot be deduced as several parameters and states are unobserved. They are successfully estimated online by a conditionally Gaussian filter based on noisy measurements. The estimates are further utilized in the design of a model-based feedback controller that stabilizes the unobserved waste heat recovery process around its operating point. Its ensures a steady harvesting of waste heat energy as well as suppressing the propagation of disturbances to adjacent subsystems. The waste heat recovery process is proven to be conditionally Gaussian that inherits beneficial closed-loop properties such as optimal state estimates in the mean-square sense. The same observer concept is applied to a larger cooling network with many more unknown parameters and states. A sequence of two conditionally Gaussian filters estimates the unobserved variables reasonably well. The observer performance is validated against two sets of acquired data from a real ship during operation.  Concerning the fresh water production in the multistage evaporation plant, a PDE model is developed for the relevant desalination processes. It presents a convenient framework to study the propagation of noises throughout the plant that are caused by the flow turbulence. The stochastic process is actuated by boundary controls that stabilize the pressure head to a defined reference profile throughout the whole subdomain in order to maintain efficient distillate production. Robust system performance is achieved by evaluating the spatial and temporal statistics of the regulation error field in terms of first four spatial moments and autocorrelation function. The regulation error could successfully maintained within tight bounds in the whole subdomain.

Description

Supervising professor

Visala, Arto, Prof., Aalto University, Department of Electrical Engineering and Automation, Finland

Thesis advisor

Tenno, Robert, Dr., Aalto University, Department of Electrical Engineering and Automation, Finland

Keywords

Waste heat recovery, desalination, process uncertainties, modelling, estimation, control

Other note

Parts

  • [Publication 1]: P. Nguyen, R. Tenno. Modelling, estimation and control of a fresh-water cooling system on cruising ships. Proceedings of 2015 IEEE European Control Conference (ECC), p. 2756-2761, Linz, Austria, July 2015.
    DOI: 10.1109/ECC.2015.7330955 View at publisher
  • [Publication 2]: P. Nguyen, R. Tenno. Unmeasured temperature control in the presence of unknown drifting parameters in a cruise ship application. Journal of Process Control, Vol. 47, p. 22-34, September 2016.
    DOI: 10.1016/j.jprocont.2016.09.002 View at publisher
  • [Publication 3]: P. Nguyen, R. Tenno. Waste heat recovery estimation on ships by means of Conditionally-Gaussian Filtering. Proceedings of 10th IFAC Conference on Control Applications in Marine Systems (CAMS 2016), Vol. 49, Iss. 23, p. 408-413, Trondheim, Norway, September 2016.
    DOI: 10.1016/j.ifacol.2016.10.438 View at publisher
  • [Publication 4]: P. Nguyen, R. Tenno. Modelling, optimization and control of a multistage flash evaporator by means of motion-planning. Proceedings of 54th IEEE Conference on Decision and Control (CDC), Vol. 2016-February, p. 6674-6679, Osaka, Japan, December 2015.
    DOI: 10.1109/CDC.2015.7403270 View at publisher
  • [Publication 5]: P. Nguyen, R. Tenno. Modelling and control of a flash evaporator through ODE system representation in PDEs form. Proceedings of 12th IEEE International Conference on Control and Automation (ICCA), Vol. 2016-July, p. 317-322, Kathmandu, Nepal, June 2016.
    DOI: 10.1109/ICCA.2016.7505296 View at publisher
  • [Publication 6]: R. Tenno, P. Nguyen. Multistage evaporator control in PDE representation. Proceedings of IFAC Workshop on Thermodynamic Foundations of Mathematical Systems Theory (TFMST II 2016), Vol. 49, Iss. 24, p. 70-75, Vigo, Spain, September 2016.
    DOI: 10.1016/j.ifacol.2016.10.757 View at publisher
  • [Publication 7]: P. Nguyen, R. Tenno. Stochastic evolution of regulation errors in a boundary actuated desalination plant. Journal of Process Control, Vol. 54, p. 101-117, June 2017.
    DOI: 10.1016/j.jprocont.2017.03.007 View at publisher

Citation

Permanent link to this item

https://urn.fi/URN:ISBN:978-952-60-7487-0

Collections

[diss] Sähkötekniikan korkeakoulu / ELEC