Panagiotis Dimas

Civil Engineer, MSc., PhD candidate

Participation in research projects

Participation as Researcher

  1. Maintenance, upgrading and extension of the Decision Support System for the management of the Athens water resource system

Published work

Publications in scientific journals

  1. A. Efstratiadis, P. Dimas, G. Pouliasis, I. Tsoukalas, P. Kossieris, V. Bellos, G.-K. Sakki, C. Makropoulos, and S. Michas, Revisiting flood hazard assessment practices under a hybrid stochastic simulation framework, Water, 14 (3), 457, doi:10.3390/w14030457, 2022.

Book chapters and fully evaluated conference publications

  1. V. Bellos, P. Kossieris, A. Efstratiadis, I. Papakonstantis, P. Papanicolaou, P. Dimas, and C. Makropoulos, Can we use hydraulic handbooks in blind trust? Two examples from a real-world complex hydraulic system, Proceedings of 7th IAHR Europe Congress "Innovative Water Management in a Changing Climate”, Athens, International Association for Hydro-Environment Engineering and Research (IAHR), 2022.
  2. P. Dimas, D. Nikolopoulos, and C. Makropoulos, Simulation framework for pipe failure detection and replacement scheduling optimization, e-Proceedings of the 5th EWaS International Conference, Naples, 556–563, 2022.
  3. V. Bellos, P. Kossieris, A. Efstratiadis, I. Papakonstantis, P. Papanicolaou, P. Dimas, and C. Makropoulos, Fiware-enabled tool for real-time control of the raw-water conveyance system of Athens, Proceedings of the 39th IAHR World Congress, Granada, 2859–2865, doi:10.3850/IAHR-39WC2521716X20221468, International Association for Hydro-Environment Engineering and Research (IAHR), 2022.
  4. P. Dimas, D. Bouziotas, D. Nikolopoulos, A. Efstratiadis, and D. Koutsoyiannis, Framework for optimal management of hydroelectric reservoirs through pumped storage: Investigation of Acheloos-Thessaly and Aliakmon hydrosystems, Proceedings of 3rd Hellenic Conference on Dams and Reservoirs, Zappeion, Hellenic Commission on Large Dams, Athens, 2017.
  5. I. Tsoukalas, P. Dimas, and C. Makropoulos, Hydrosystem optimization on a budget: Investigating the potential of surrogate based optimization techniques, 14th International Conference on Environmental Science and Technology (CEST2015), Global Network on Environmental Science and Technology, University of the Aegean, 2015.

Conference publications and presentations with evaluation of abstract

  1. I. Pappa, Y. Dimakos, P. Dimas, P. Kossieris, P. Dimitriadis, and D. Koutsoyiannis, Spatial and temporal variability of wind speed and energy over Greece, European Geosciences Union General Assembly 2014, Geophysical Research Abstracts, Vol. 16, Vienna, EGU2014-13591, doi:10.13140/RG.2.2.11238.63048, European Geosciences Union, 2014.
  2. P. Dimas, D. Bouziotas, A. Efstratiadis, and D. Koutsoyiannis, A holistic approach towards optimal planning of hybrid renewable energy systems: Combining hydroelectric and wind energy, European Geosciences Union General Assembly 2014, Geophysical Research Abstracts, Vol. 16, Vienna, EGU2014-5851, doi:10.13140/RG.2.2.28854.70723, European Geosciences Union, 2014.
  3. P. Dimas, D. Bouziotas, A. Efstratiadis, and D. Koutsoyiannis, A stochastic simulation framework for planning and management of combined hydropower and wind energy systems, Facets of Uncertainty: 5th EGU Leonardo Conference – Hydrofractals 2013 – STAHY 2013, Kos Island, Greece, doi:10.13140/RG.2.2.27491.55841, European Geosciences Union, International Association of Hydrological Sciences, International Union of Geodesy and Geophysics, 2013.
  4. E. Anagnostopoulou, A. Galani, P. Dimas, A. Karanasios, T. Mastrotheodoros, E. Michailidi, D. Nikolopoulos, S. Pontikos, F. Sourla, A. Chazapi, S.M. Papalexiou, and D. Koutsoyiannis, Record breaking properties for typical autocorrelation structures, European Geosciences Union General Assembly 2013, Geophysical Research Abstracts, Vol. 15, Vienna, EGU2013-4520, doi:10.13140/RG.2.2.20420.22400, European Geosciences Union, 2013.

Academic works

  1. P. Dimas, Stochastic simulation framework for optimal planning of hybrid system of hydroelectic - wind energy. Investigation based on the Aliakmonas hydrosystem, Diploma thesis, 237 pages, Department of Water Resources and Environmental Engineering – National Technical University of Athens, December 2013.

Miscellaneous works

  1. G. Karakatsanis, I. Apostolopoulos, G. Alexiou, P. Stamouli, I. Fountoulakis, S. C. Batelis, Y. Dimakos, E. Feloni, E. C. Moschou, N. Bountas, N. Boboti, D. Bouziotas, P. Dimas, and E. Sepetzi, Water resources, infrastructures and services: Privatization or municipalization?, Athens, 4 July 2013.

Details on research projects

Participation as Researcher

  1. Maintenance, upgrading and extension of the Decision Support System for the management of the Athens water resource system

    Duration: October 2008–November 2011

    Budget: €72 000

    Project director: N. Mamassis

    Principal investigator: D. Koutsoyiannis

    This research project includes the maintenance, upgrading and extension of the Decision Support System that developed by NTUA for EYDAP in the framework of the research project “Updating of the supervision and management of the water resources’ system for the water supply of the Athens’ metropolitan area”. The project is consisted of the following parts: (a) Upgrading of the Data Base, (b)Upgrading and extension of hydrometeorological network, (c) upgrading of the hydrometeorological data process software, (d) upgrading and extension of the Hydronomeas software, (e) hydrological data analysis and (f) support to the preparation of the annual master plans

Published work in detail

Publications in scientific journals

  1. A. Efstratiadis, P. Dimas, G. Pouliasis, I. Tsoukalas, P. Kossieris, V. Bellos, G.-K. Sakki, C. Makropoulos, and S. Michas, Revisiting flood hazard assessment practices under a hybrid stochastic simulation framework, Water, 14 (3), 457, doi:10.3390/w14030457, 2022.

    We propose a novel probabilistic approach to flood hazard assessment, aiming to address the major shortcomings of everyday deterministic engineering practices in a computationally efficient manner. In this context, the principal sources of uncertainty are defined across the overall modelling procedure, namely, the statistical uncertainty of inferring annual rainfall maxima through distribution models that are fitted to empirical data, and the inherently stochastic nature of the underlying hydrometeorological and hydrodynamic processes. Our work focuses on three key facets, i.e., the temporal profile of storm events, the dependence of flood generation mechanisms to antecedent soil moisture conditions, and the dependence of runoff propagation over the terrain and the stream network on the intensity of the flood event. These are addressed through the implementation of a series of cascade modules, based on publicly available and open-source software. Moreover, the hydrodynamic processes are simulated by a hybrid 1D/2D modelling approach, which offers a good compromise between computational efficiency and accuracy. The proposed framework enables the estimation of the uncertainty of all flood-related quantities, by means of empirically-derived quantiles for given return periods. Finally, a set of easily applicable flood hazard metrics are introduced for the quantification of flood hazard.

    Full text: http://www.itia.ntua.gr/en/getfile/2170/1/documents/water-14-00457.pdf (6083 KB)

    See also: https://www.mdpi.com/2073-4441/14/3/457

    Other works that reference this work (this list might be obsolete):

    1. Tegos, A., A. Ziogas, V. Bellos, and A. Tzimas, Forensic hydrology: a complete reconstruction of an extreme flood event in data-scarce area, Hydrology, 9(5), 93, doi:10.3390/hydrology9050093, 2022.
    2. Afzal, M. A., S. Ali, A. Nazeer, M. I. Khan, M. M. Waqas, R. A. Aslam, M. J. M. Cheema, M. Nadeem, N. Saddique, M. Muzammil, and A. N. Shah, Flood inundation modeling by integrating HEC–RAS and satellite imagery: A case study of the Indus river basin, Water, 14(19), 2984, doi:10.3390/w14192984, 2022.
    3. Vangelis, H., I. Zotou, I. M. Kourtis, V. Bellos, and V. A. Tsihrintzis, Relationship of rainfall and flood return periods through hydrologic and hydraulic modeling, Water, 14(22), 3618, doi:10.3390/w14223618, 2022.

Book chapters and fully evaluated conference publications

  1. V. Bellos, P. Kossieris, A. Efstratiadis, I. Papakonstantis, P. Papanicolaou, P. Dimas, and C. Makropoulos, Can we use hydraulic handbooks in blind trust? Two examples from a real-world complex hydraulic system, Proceedings of 7th IAHR Europe Congress "Innovative Water Management in a Changing Climate”, Athens, International Association for Hydro-Environment Engineering and Research (IAHR), 2022.

    In this work, we investigate whether the parameters of physics-based hydraulic models, omnipresent in every relevant engineering handbook, can be used in blind trust in a real-world complex system. Here, we focus on the discharge coefficient for flows through a sluice gate and the Manning’s coefficient for steady flows, and we compare their typical literature values (experimentally derived) against the ones obtained via a “grey-box” calibration approach using real flow data from the complex raw-water conveyance system of Athens, Greece.

  1. P. Dimas, D. Nikolopoulos, and C. Makropoulos, Simulation framework for pipe failure detection and replacement scheduling optimization, e-Proceedings of the 5th EWaS International Conference, Naples, 556–563, 2022.

    Identification of water network pipes susceptible to failure is a demanding task, which requires a coherent and extensive dataset that contains both their physical characteristics (i.e., pipe inner diameter, construction material, length, etc.) and a snapshot of their current state, including their age and failure history. As water networks are critical for human prosperity, the need to adequately forecast failure is immediate. A huge number of Machine Learning (ML) and AI models have been applied, furthermore, only a few of them have been coupled with algorithms that translate the failure probability into asset management decision support strategies. The latter should include pipe rehabilitation planning and/or replacement scheduling under monetary/time unit constraints. Additionally, the assessment of each decision is seldomly performed by developing performance indices stemming from simulation. Hence, in this work, the outline of a framework, able to incorporate pipe failure detection techniques utilizing statistical, ML and AI models with pipe replacement scheduling optimization and assessment of state-of-the-art resilience indices via simulation scenarios, is presented. The framework is demonstrated on a real world-based case study.

    Full text:

  1. V. Bellos, P. Kossieris, A. Efstratiadis, I. Papakonstantis, P. Papanicolaou, P. Dimas, and C. Makropoulos, Fiware-enabled tool for real-time control of the raw-water conveyance system of Athens, Proceedings of the 39th IAHR World Congress, Granada, 2859–2865, doi:10.3850/IAHR-39WC2521716X20221468, International Association for Hydro-Environment Engineering and Research (IAHR), 2022.

    The raw water network system of Athens (Greece) is a complex infrastructure comprising around 500 km of aqueducts, conveying water from four reservoirs to four water treatment plants, while serving several other local users. In this work, we focus on the most important part of this system, namely the open-channel aqueduct of Mornos. This extends over 200 km and has a dual operation, namely water conveyance and flow regulation through temporary storage along the channel. This is achieved by a series of Λ-type structures, each one comprising sluice gates for flow control and a lateral ogee spillway. Currently, the regulation across the channel is performed through empirical rules, and according to target volumes requested by the operators of the downstream water treatment plants, on a daily basis. However, this management policy, which is strongly based on expert’s knowledge, is neither sustainable nor safe, from a resilience perspective. Furthermore, the system is subject to occasional failures, due to undesirable overflows resulting to non-negligible water losses. In order to establish an optimal control policy, we developed an operational tool for the real- time scheduling of the sluice gate settings. Core of the tool is a conceptual model that incorporates the following assumptions: a) the operation of a Λ-type structure does not affect the operation of the other relevant structures; b) the Λ-type structure has two flow components, namely through the sluice gate and over the lateral spillway, which can be described by theoretical and semi-empirical hydraulic formulas, considering as unknown parameters the discharge coefficients of all sluice gates. On the other hand, the known model inputs are the geometrical characteristics of Λ-type structures and the real-time data for discharge, water level and gate opening, which are obtained from the telemetric monitoring system of the channel. In this respect, the key challenge is the determination of the discharge coefficients. This is employed through a grey-box approach, in which the model parameters are calibrated in continuous mode, using real-time data. To check the plausibility of the discharge coefficients, as derived by the real-time calibration phase, a comparison is made with the corresponding coefficients derived by historical data (off-line calibration). The tool, along with other analytics and algorithms developed, has been seamlessly integrated with the existing legacy system (e.g., SCADA, databases) of the system’s operator (Athens Water Supply and Sewerage Company - EYDAP), using the FIWARE standardization protocol.

    Full text: http://www.itia.ntua.gr/en/getfile/2226/1/documents/04-07-014-1468.pdf (10700 KB)

  1. P. Dimas, D. Bouziotas, D. Nikolopoulos, A. Efstratiadis, and D. Koutsoyiannis, Framework for optimal management of hydroelectric reservoirs through pumped storage: Investigation of Acheloos-Thessaly and Aliakmon hydrosystems, Proceedings of 3rd Hellenic Conference on Dams and Reservoirs, Zappeion, Hellenic Commission on Large Dams, Athens, 2017.

    In this study, a holistic approach for the optimal management of two large, multi-reservoir hydrosystems in Greece is analysed, applied in cases of multiple and conflicting water uses, such as hydroelectric production and the coverage of irrigation and drinking water demands. In general, the optimal management of such hydrosystems presents a strong challenge for engineers, due to the stochasticity of inflows and the non-linear nature of hydroelectric production. To manage the strong variability of renewable energy production, the use of the two studied cases of Acheloos-Thessaly and Aliakmonas as pump-storage systems is proposed. To explore the optimal management policies, the methodological framework of “Parameterisation-Simulation-Optimisation” (PSO) is applied, employed through the use of Hydronomeas software and its hydroelectric production optimization module. The goal of the analysis is the estimation of the capacity to generate firm energy with a preset high reliability level in both systems, as well as the assessment of the consequent economic benefit obtained with the optimal policies found through Hydronomeas. Moreover, the benefits of employing pump-storage schemes in order to provide a buffer for other renewable energy sources with strong variability, such as wind energy, is explored.

    Full text: http://www.itia.ntua.gr/en/getfile/1747/1/documents/fragmata2017.pdf (1070 KB)

    Additional material:

  1. I. Tsoukalas, P. Dimas, and C. Makropoulos, Hydrosystem optimization on a budget: Investigating the potential of surrogate based optimization techniques, 14th International Conference on Environmental Science and Technology (CEST2015), Global Network on Environmental Science and Technology, University of the Aegean, 2015.

    Development of uncertainty-aware operational rules for multi-reservoir systems is a demanding and challenging task due to the complexity of the system dynamics, the number of decision variables and the hydrological uncertainty. In order to overcome this issue the parsimonious parameterization-simulation-optimization (PSO) framework is employed coupled with stochastically generated hydrological time-series. However, when the simulation model requires long computational time this coupling imposes a computational barrier to the framework. The purpose of this paper is threefold: a) Investigate the potential of Efficient Global Optimization (EGO) algorithm (and its variants) which is capable of reaching global optima within a few simulation model evaluations (~500 or less). b) Extend the capabilities of WEAP21 water resources management model by using it within PSO framework (named WEAP21-PSO) and c) Validate and compare the results of WEAP21-PSO using the well-known hydrosystem management model Hydronomeas coupled with Evolutionary Annealing Simplex (EAS) optimization algorithm. Results confirm that EGO has the potential and the capabilities to handle computationally demanding problems and furthermore is capable of locating the optimal solution within few simulation model evaluations and that the WEAP21-PSO framework performs well at the task at hand.

    Full text: http://www.itia.ntua.gr/en/getfile/1574/1/documents/cest2015_00162_oral_paper.pdf (475 KB)

    See also: http://cest.gnest.org/cest15proceedings/public_html/papers/cest2015_00162_oral_paper.pdf

Conference publications and presentations with evaluation of abstract

  1. I. Pappa, Y. Dimakos, P. Dimas, P. Kossieris, P. Dimitriadis, and D. Koutsoyiannis, Spatial and temporal variability of wind speed and energy over Greece, European Geosciences Union General Assembly 2014, Geophysical Research Abstracts, Vol. 16, Vienna, EGU2014-13591, doi:10.13140/RG.2.2.11238.63048, European Geosciences Union, 2014.

    To appraise the wind potential over Greece we analyse the main statistical properties of wind speed through time. To this end, we use 66 time series from 1932 to 2013 on daily and monthly time scale and examine the spatial variability of wind speed over Greece. To depict the main statistical behavior and potential of the wind over Greece, maps have been created illustrating the basic statistical characteristics of wind speed on monthly to annual time scale. We also examine time series of energy production from the currently developed system of key wind parks and we compare the theoretical potential with the actually produced energy. Finally, we explore a methodology to simulate wind energy production in a stochastic framework. In that context we generate hourly wind speed synthetic data using a modified Bartlett-Lewis model implemented in Hyetos. The results of our analysis offer an improved overall picture of wind speed variability over Greece and help us clarify to which extent Hyetos is applicable in the stochastic generation of wind speed time series.

    Full text:

    Additional material:

    See also: http://dx.doi.org/10.13140/RG.2.2.11238.63048

  1. P. Dimas, D. Bouziotas, A. Efstratiadis, and D. Koutsoyiannis, A holistic approach towards optimal planning of hybrid renewable energy systems: Combining hydroelectric and wind energy, European Geosciences Union General Assembly 2014, Geophysical Research Abstracts, Vol. 16, Vienna, EGU2014-5851, doi:10.13140/RG.2.2.28854.70723, European Geosciences Union, 2014.

    Hydropower with pumped storage is a proven technology with very high efficiency that offers a unique large-scale energy buffer. Energy storage is employed by pumping water upstream to take advantage of the excess of produced energy (e.g. during night) and next retrieving this water to generate hydro-power during demand peaks. Excess energy occurs due to other renewables (wind, solar) whose power fluctuates in an uncontrollable manner. By integrating these with hydroelectric plants with pumped storage facilities we can form autonomous hybrid renewable energy systems. The optimal planning and management thereof requires a holistic approach, where uncertainty is properly represented. In this context, a novel framework is proposed, based on stochastic simulation and optimization. This is tested in an existing hydrosystem of Greece, considering its combined operation with a hypothetical wind power system, for which we seek the optimal design to ensure the most beneficial performance of the overall scheme.

    Full text: http://www.itia.ntua.gr/en/getfile/1442/2/documents/2014_egu_hybrid.pdf (1659 KB)

    Additional material:

    See also: http://dx.doi.org/10.13140/RG.2.2.28854.70723

  1. P. Dimas, D. Bouziotas, A. Efstratiadis, and D. Koutsoyiannis, A stochastic simulation framework for planning and management of combined hydropower and wind energy systems, Facets of Uncertainty: 5th EGU Leonardo Conference – Hydrofractals 2013 – STAHY 2013, Kos Island, Greece, doi:10.13140/RG.2.2.27491.55841, European Geosciences Union, International Association of Hydrological Sciences, International Union of Geodesy and Geophysics, 2013.

    Pumped storage within hydroelectric reservoir systems is a proven technology with very high efficiency, as well as the unique large-scale energy buffer. The storage of energy is implemented by pumping water upstream, for taking advantage of the excess of energy (e.g. during night hours), and next retrieving this water to generate hydropower during demand peaks. Interestingly, this excess can be offered by other renewable energy sources, particularly wind turbines, which can be integrated within hydroelectric systems with pumped storage facilities, to formulate autonomous hybrid renewable energy schemes. The optimal planning and management of such systems is a challenging task, which requires a holistic viewpoint and a consistent representation of the multiple sources of uncertainty. In this respect, a novel framework is proposed, which is tested in an existing hydrosystem of Greece (i.e. the reservoir system of Aliakmon, which also serves other water uses), considering a combined operation with a hypothetical wind power system. The two components, which are linked through a single pumping storage plant, are modelled in different time resolutions. In particular, for the representation of the water resource system we adopt, as typically, a monthly time step, while for the wind power system we use hourly steps. For both systems, the input variables (i.e. hydrological inflows and wind velocity, respectively) are generated via appropriate stochastic simulation models, by means of synthetic time series of 1000 years length. In order to ensure the most beneficial performance of the integrated system, we investigate different design parameters of the wind turbines, for which we optimize the operation policy of the hydroelectric reservoirs.

    Full text: http://www.itia.ntua.gr/en/getfile/1386/1/documents/KosHybrid_poster.pdf (691 KB)

    See also: http://dx.doi.org/10.13140/RG.2.2.27491.55841

  1. E. Anagnostopoulou, A. Galani, P. Dimas, A. Karanasios, T. Mastrotheodoros, E. Michailidi, D. Nikolopoulos, S. Pontikos, F. Sourla, A. Chazapi, S.M. Papalexiou, and D. Koutsoyiannis, Record breaking properties for typical autocorrelation structures, European Geosciences Union General Assembly 2013, Geophysical Research Abstracts, Vol. 15, Vienna, EGU2013-4520, doi:10.13140/RG.2.2.20420.22400, European Geosciences Union, 2013.

    Record-breaking occurrences in hydrometeorological processes are often used particularly in communicating information to the public and their analysis offers the possibility of better comprehending extreme events. However, the typical comprehension depends on prototypes characterized by pure randomness. In fact the occurrence of record breaking depends on the marginal distribution and the autocorrelation function of the process as well the length of available record. Here we study the influence of the process autocorrelation structure on the statistics of record-breaking occurrences giving emphasis on the differences with those of a purely random process. The particular stochastic processes, which we examine, are the AR(1), AR(2) and ARMA(1,1), as well as the Hurst-Kolmogorov process. The necessary properties are calculated using either analytical methods when possible or Monte Carlo simulation. We also compare the model results with observed hydrometeorological time series.

    Full text:

    Additional material:

    See also: http://dx.doi.org/10.13140/RG.2.2.20420.22400

Academic works

  1. P. Dimas, Stochastic simulation framework for optimal planning of hybrid system of hydroelectic - wind energy. Investigation based on the Aliakmonas hydrosystem, Diploma thesis, 237 pages, Department of Water Resources and Environmental Engineering – National Technical University of Athens, December 2013.

    Pumped storage is a proven technology with very high efficiency that offers a unique large-scale energy buffer. Energy storage is employed by pumping water upstream to take advantage of the excess of energy (e.g. during night) and next retrieving this water to generate hydro-power during demand peaks. This excess can be offered by other renewables, which can be integrated within hydroelectric systems with pumped storage facilities to formulate autonomous hybrid renewable energy systems (HRES). The optimal planning and management of HRES requires a holistic overview, where uncertainty is properly represented. In this context, a novel framework is proposed, based on stochastic simulation and optimization. This is tested in an existing hydrosystem of Greece, considering its combined operation with a hypothetical wind power system, for which we seek the optimal design to ensure the most beneficial performance of the overall scheme.

    Related works:

    • [9] Presentation in EGU Leonardo conference

    Full text: http://www.itia.ntua.gr/en/getfile/1417/1/documents/Thesis_Dimas_1.pdf (14927 KB)

    Additional material:

Miscellaneous works

  1. G. Karakatsanis, I. Apostolopoulos, G. Alexiou, P. Stamouli, I. Fountoulakis, S. C. Batelis, Y. Dimakos, E. Feloni, E. C. Moschou, N. Bountas, N. Boboti, D. Bouziotas, P. Dimas, and E. Sepetzi, Water resources, infrastructures and services: Privatization or municipalization?, Athens, 4 July 2013.

    Remarks:

    Student Workshop of the course "Water Resources Management". Coordinators: Demetris Koutsoyiannis & Andreas Efstratiadis

    Photos from the workshop are also available. Extensive reportage of the event was presented by the newspaper Eleftherotypia, (see also the print version in an attached file above), as well as by Internet forums (e.g. Econews, Infowar).

    Full text:

    Additional material: