Z. Maroulis | National Technical University of Athens (original) (raw)

Papers by Z. Maroulis

Research paper thumbnail of Erratum: Brackish Karstic Springs Model: Application to Almiros Spring in Crete (Ground Water (September-October))

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Research paper thumbnail of Renewable Energy Sources Penetration in Greece: Characteristics and Seasonal Variation of the Electricity Demand Share Covering

Energies, 2019

The significant penetration of renewables, in the Hellenic electricity system, during the last 12... more The significant penetration of renewables, in the Hellenic electricity system, during the last 12 years, was based on feed-in tariff-supporting schemes, according to the compliance to European Directives. The characteristics of this penetration are presented and analyzed in this paper based on real data. Photovoltaics, wind parks, hydroelectric plants, biomass-driven plants, and cogeneration systems are examined. The cost of the feed-in tariff incentives is qualified and analyzed. Simple but effective models are proposed to describe renewable seasonal variation: (a) A simple cosine model adequately describes the seasonal performance of various renewable technologies in terms of capacity factor; (b) a smart seasonal model based on the separation between winter and summer consumption activities (both following normal distributions) adequately describes the electricity consumption profile. The predicted values of renewable shares using the proposed models were also validated with histo...

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Research paper thumbnail of Penetration of Photovoltaics in Greece

Energies, 2015

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Research paper thumbnail of Modeling of thermal conductivity of granular starches

Journal of Food Engineering, 1990

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Research paper thumbnail of Simultaneous estimation of heat and mass transfer coefficients in externally controlled drying

Journal of Food Engineering, 1991

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Research paper thumbnail of Food Plant Economics

Food Science and Technology, 2007

INTRODUCTION Food System Food Process Technology Food Plant Economics Economic Analysis of Food P... more INTRODUCTION Food System Food Process Technology Food Plant Economics Economic Analysis of Food Processing Plants Food Research and Development STRUCTURE OF THE FOOD INDUSTRY Food Systems OVERVIEW OF FOOD PROCESS AND PLANT DESIGN Food Process Design Food Plant Design Food Plant Utilities Food Plant Economics PROCESS ENGINEERING ECONOMICS Money Flow in a Business Enterprise Capital Cost Manufacturing Cost Cash Flow Analysis Plant Profitability Sensitivity Analysis CAPITAL COST OF FOOD PLANTS Quotations from Fabricators Equipment Cost Estimation Data for Preliminary Equipment Cost Estimation Short-Cut Equipment Sizing OPERATING COST OF FOOD PLANTS Raw Materials Food Product Cost Data Packaging Materials Utilities Utility Cost Estimating Model Labor Labor Cost Estimation Model FOOD PRESERVATION PLANTS Tomato Paste Plant Orange Juice Concentration Plant UHT Sterilized Milk Plant Fruit Canning Plant Vegetable Freezing Plant Vegetable Dehydration Plant Techno-Economic Comparison Suppliers of Major Food Processing Equipment FOOD MANUFACTURING PLANTS Bread Manufacturing Plant Yogurt Manufacturing Plant Wine Processing Plant Economic Comparison FOOD INGREDIENTS PLANTS Beet Sugar Plant Overview of Process Plant Optimization APPENDIX Glossary of Economic Terms Notation and Conversion to SI Units Useful Thermophysical Properties of Water Thermophysical Properties of Some Food Materials Rheological Properties Overall Heat Transfer Coefficients Accompanying CD INDEX

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Research paper thumbnail of Cogeneration Economics for Greenhouses in Europe

Energies, 2020

Cogeneration is a cost-effective technology, and modern greenhouses are considered one of the bes... more Cogeneration is a cost-effective technology, and modern greenhouses are considered one of the best applications for it due to their energy intensity. Taking into account that in such cases the production cost is significantly affected by the cost of energy, the potential of combined heat and power (CHP) has already been examined and proved in practice in some European countries, with the Netherlands being the most representative example. In this study, a comparative investigation of the greenhouse energy cost in all European countries is presented through the use of a combined cooling heat and power (CCHP) system. Using actual historical data spanning a decade, a total overview of the European level is given regarding greenhouse thermal requirements and CCHP energy costs for the cultivation of products with an accepted temperature cultivation range 20 ± 5 °C. By consulting (a) the available daily historical meteorological data for the 2008–2018 period, (b) the recorded actual electr...

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Research paper thumbnail of Food Process Design

... Food Process Design, Zacharias B. Maroulis and George D. Sara-vacos 127. ... edited by Consta... more ... Food Process Design, Zacharias B. Maroulis and George D. Sara-vacos 127. ... edited by Constan-tina Tzia and George Liadakis Additional Volumes in Preparation Physical Principles of Food Preservation: Second Edition, Re-vised and Expanded, Marcus Karel and Daryl B ...

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Research paper thumbnail of Economic Assessment of Cogeneration Systems in Operation

Energies, 2020

A systematic method to evaluate the economic operating performance of existing combined heat and ... more A systematic method to evaluate the economic operating performance of existing combined heat and power (CHP) or combined cooling heat and power (CCHP) generation systems is applied. Two key performance indicators are selected to evaluate both the technical and the economic performance, based on operating recording data; the capacity factor and the capital recovery. The case study for eight projects in Athens is presented with the purpose to reveal the current situation of CHP in Greece and identify reasons that are hindering its penetration. Interesting conclusions were reached from the analysis. Only two out of the eight projects managed to achieve the break-even point in less than four years since the beginning of their operation, while oversizing phenomena were noticed in many cases leading in extremely low capacity factors.

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Research paper thumbnail of Merit Order Effect Modeling: The Case of the Hellenic Electricity Market

Energies, 2019

A simple effective model is proposed for the day-ahead electricity market. The model considers th... more A simple effective model is proposed for the day-ahead electricity market. The model considers the main factors which govern the process, predicts the seasonal and daily variation of electricity demand, renewable production, system marginal price, and merit order effect. The accuracy of the model is increased by fitting to historic data of the Hellenic electricity market. During the period between October 2016 and December 2018, the Hellenic electricity market calculated explicitly the merit order effect using an innovative mechanism to directly charge the electricity suppliers (retailers). On the basis of the proposed model and the market recorded data, the effect of the renewable penetration on the wholesale Hellenic electricity prices is revealed. The model is further used to analyze the market future behavior when basic factors (electricity demand, conventional power, and renewable penetration) are known or estimated. The effect of merit order effect on the Hellenic legislation ...

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Research paper thumbnail of Process Engineering Economics

Food Science and Technology, 2007

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Research paper thumbnail of Brackish Karstic Springs Model: Application to Almiros Spring in Crete

Ground Water, 2003

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Research paper thumbnail of Heat and mass transfer modeling in air drying of foods

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Research paper thumbnail of Viscoelastic behaviour of dehydrated products during rehydration

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Research paper thumbnail of Object-oriented simulation of hydrometallurgical processes Part III. Application to leaching of laterites and pyrites

Metallurgical and Materials Transactions B, 1997

The steady-state process simulator developed by Kiranoudis et al. has been used for the detailed ... more The steady-state process simulator developed by Kiranoudis et al. has been used for the detailed simulation of the Bayer process flowsheet. It consists of the digestor/flash section as well as the precipitation and washing circuits. Advanced hydrometallurgical process models for the specific unit operations involved were developed and are appropriately described. The simulation studies mainly focus on studying the overall effects of certain design parameters on the entire plant efficiency. The overall performance of the bauxite digestion section is greatly and positively affected by the free-soda concentration of the feed liquor, the corresponding concentration of solid particles, and the operation temperature of the circuit. Precipitation of alumina in crystallizers is greatly affected by the corresponding soda concentration of the washing unit product stream, indicating the importance of this section. Furthermore, ambient temperature is important to the precipitation kinetics, influencing negatively the quantitative precipitation but resulting in particle populations of higher mean diameter.

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Research paper thumbnail of Modelling and optimization of carbon-in-pulp gold recovery processes

IMA Journal of Management Mathematics, 1998

... Obviously, the binary constants expressing whether a pump is working or not hold for ... MODE... more ... Obviously, the binary constants expressing whether a pump is working or not hold for ... MODELLING AND OPTIMIZATION OF CIP GOLD RECOVERY ... problem comprise both integer and continuous variables forming mixed-integer nonlinear programming (MINLP) configurations. ...

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Research paper thumbnail of Drying kinetics of onion and green pepper

... Investigation involved two vegetables (namely, green pepper and onion) and a wide range of ch... more ... Investigation involved two vegetables (namely, green pepper and onion) and a wide range of characteristic dimensions of samples and air ... Mathematical modeling of dehydration operations is important in the design and optimization of dryers (Brook and Bakker-Arkema, 1978 ...

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Research paper thumbnail of Microwave vacuum drying kinetics of some fruits

Microwave vacuum drying kinetics of three fruits (namely, apple, kiwi and pear) were studied by i... more Microwave vacuum drying kinetics of three fruits (namely, apple, kiwi and pear) were studied by introducing an one-parameter empirical mass transfer model, involving a characteristic parameter (drying constant), as a function of process variables. The model was tested with data produced in a microwave oven equipped with vacuum apparatus, using non-linear regression analysis. The investigation involved a wide range of

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Research paper thumbnail of Equilibrium moisture content and heat of desorption of some vegetables

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Research paper thumbnail of Water sorption isotherms of raisins, currants, figs, prunes and apricots

Journal of Food …, 1990

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Research paper thumbnail of Erratum: Brackish Karstic Springs Model: Application to Almiros Spring in Crete (Ground Water (September-October))

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Research paper thumbnail of Renewable Energy Sources Penetration in Greece: Characteristics and Seasonal Variation of the Electricity Demand Share Covering

Energies, 2019

The significant penetration of renewables, in the Hellenic electricity system, during the last 12... more The significant penetration of renewables, in the Hellenic electricity system, during the last 12 years, was based on feed-in tariff-supporting schemes, according to the compliance to European Directives. The characteristics of this penetration are presented and analyzed in this paper based on real data. Photovoltaics, wind parks, hydroelectric plants, biomass-driven plants, and cogeneration systems are examined. The cost of the feed-in tariff incentives is qualified and analyzed. Simple but effective models are proposed to describe renewable seasonal variation: (a) A simple cosine model adequately describes the seasonal performance of various renewable technologies in terms of capacity factor; (b) a smart seasonal model based on the separation between winter and summer consumption activities (both following normal distributions) adequately describes the electricity consumption profile. The predicted values of renewable shares using the proposed models were also validated with histo...

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Research paper thumbnail of Penetration of Photovoltaics in Greece

Energies, 2015

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Research paper thumbnail of Modeling of thermal conductivity of granular starches

Journal of Food Engineering, 1990

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Research paper thumbnail of Simultaneous estimation of heat and mass transfer coefficients in externally controlled drying

Journal of Food Engineering, 1991

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Research paper thumbnail of Food Plant Economics

Food Science and Technology, 2007

INTRODUCTION Food System Food Process Technology Food Plant Economics Economic Analysis of Food P... more INTRODUCTION Food System Food Process Technology Food Plant Economics Economic Analysis of Food Processing Plants Food Research and Development STRUCTURE OF THE FOOD INDUSTRY Food Systems OVERVIEW OF FOOD PROCESS AND PLANT DESIGN Food Process Design Food Plant Design Food Plant Utilities Food Plant Economics PROCESS ENGINEERING ECONOMICS Money Flow in a Business Enterprise Capital Cost Manufacturing Cost Cash Flow Analysis Plant Profitability Sensitivity Analysis CAPITAL COST OF FOOD PLANTS Quotations from Fabricators Equipment Cost Estimation Data for Preliminary Equipment Cost Estimation Short-Cut Equipment Sizing OPERATING COST OF FOOD PLANTS Raw Materials Food Product Cost Data Packaging Materials Utilities Utility Cost Estimating Model Labor Labor Cost Estimation Model FOOD PRESERVATION PLANTS Tomato Paste Plant Orange Juice Concentration Plant UHT Sterilized Milk Plant Fruit Canning Plant Vegetable Freezing Plant Vegetable Dehydration Plant Techno-Economic Comparison Suppliers of Major Food Processing Equipment FOOD MANUFACTURING PLANTS Bread Manufacturing Plant Yogurt Manufacturing Plant Wine Processing Plant Economic Comparison FOOD INGREDIENTS PLANTS Beet Sugar Plant Overview of Process Plant Optimization APPENDIX Glossary of Economic Terms Notation and Conversion to SI Units Useful Thermophysical Properties of Water Thermophysical Properties of Some Food Materials Rheological Properties Overall Heat Transfer Coefficients Accompanying CD INDEX

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Research paper thumbnail of Cogeneration Economics for Greenhouses in Europe

Energies, 2020

Cogeneration is a cost-effective technology, and modern greenhouses are considered one of the bes... more Cogeneration is a cost-effective technology, and modern greenhouses are considered one of the best applications for it due to their energy intensity. Taking into account that in such cases the production cost is significantly affected by the cost of energy, the potential of combined heat and power (CHP) has already been examined and proved in practice in some European countries, with the Netherlands being the most representative example. In this study, a comparative investigation of the greenhouse energy cost in all European countries is presented through the use of a combined cooling heat and power (CCHP) system. Using actual historical data spanning a decade, a total overview of the European level is given regarding greenhouse thermal requirements and CCHP energy costs for the cultivation of products with an accepted temperature cultivation range 20 ± 5 °C. By consulting (a) the available daily historical meteorological data for the 2008–2018 period, (b) the recorded actual electr...

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Research paper thumbnail of Food Process Design

... Food Process Design, Zacharias B. Maroulis and George D. Sara-vacos 127. ... edited by Consta... more ... Food Process Design, Zacharias B. Maroulis and George D. Sara-vacos 127. ... edited by Constan-tina Tzia and George Liadakis Additional Volumes in Preparation Physical Principles of Food Preservation: Second Edition, Re-vised and Expanded, Marcus Karel and Daryl B ...

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Research paper thumbnail of Economic Assessment of Cogeneration Systems in Operation

Energies, 2020

A systematic method to evaluate the economic operating performance of existing combined heat and ... more A systematic method to evaluate the economic operating performance of existing combined heat and power (CHP) or combined cooling heat and power (CCHP) generation systems is applied. Two key performance indicators are selected to evaluate both the technical and the economic performance, based on operating recording data; the capacity factor and the capital recovery. The case study for eight projects in Athens is presented with the purpose to reveal the current situation of CHP in Greece and identify reasons that are hindering its penetration. Interesting conclusions were reached from the analysis. Only two out of the eight projects managed to achieve the break-even point in less than four years since the beginning of their operation, while oversizing phenomena were noticed in many cases leading in extremely low capacity factors.

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Research paper thumbnail of Merit Order Effect Modeling: The Case of the Hellenic Electricity Market

Energies, 2019

A simple effective model is proposed for the day-ahead electricity market. The model considers th... more A simple effective model is proposed for the day-ahead electricity market. The model considers the main factors which govern the process, predicts the seasonal and daily variation of electricity demand, renewable production, system marginal price, and merit order effect. The accuracy of the model is increased by fitting to historic data of the Hellenic electricity market. During the period between October 2016 and December 2018, the Hellenic electricity market calculated explicitly the merit order effect using an innovative mechanism to directly charge the electricity suppliers (retailers). On the basis of the proposed model and the market recorded data, the effect of the renewable penetration on the wholesale Hellenic electricity prices is revealed. The model is further used to analyze the market future behavior when basic factors (electricity demand, conventional power, and renewable penetration) are known or estimated. The effect of merit order effect on the Hellenic legislation ...

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Research paper thumbnail of Process Engineering Economics

Food Science and Technology, 2007

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Research paper thumbnail of Brackish Karstic Springs Model: Application to Almiros Spring in Crete

Ground Water, 2003

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Research paper thumbnail of Heat and mass transfer modeling in air drying of foods

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Viscoelastic behaviour of dehydrated products during rehydration

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Object-oriented simulation of hydrometallurgical processes Part III. Application to leaching of laterites and pyrites

Metallurgical and Materials Transactions B, 1997

The steady-state process simulator developed by Kiranoudis et al. has been used for the detailed ... more The steady-state process simulator developed by Kiranoudis et al. has been used for the detailed simulation of the Bayer process flowsheet. It consists of the digestor/flash section as well as the precipitation and washing circuits. Advanced hydrometallurgical process models for the specific unit operations involved were developed and are appropriately described. The simulation studies mainly focus on studying the overall effects of certain design parameters on the entire plant efficiency. The overall performance of the bauxite digestion section is greatly and positively affected by the free-soda concentration of the feed liquor, the corresponding concentration of solid particles, and the operation temperature of the circuit. Precipitation of alumina in crystallizers is greatly affected by the corresponding soda concentration of the washing unit product stream, indicating the importance of this section. Furthermore, ambient temperature is important to the precipitation kinetics, influencing negatively the quantitative precipitation but resulting in particle populations of higher mean diameter.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Modelling and optimization of carbon-in-pulp gold recovery processes

IMA Journal of Management Mathematics, 1998

... Obviously, the binary constants expressing whether a pump is working or not hold for ... MODE... more ... Obviously, the binary constants expressing whether a pump is working or not hold for ... MODELLING AND OPTIMIZATION OF CIP GOLD RECOVERY ... problem comprise both integer and continuous variables forming mixed-integer nonlinear programming (MINLP) configurations. ...

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Research paper thumbnail of Drying kinetics of onion and green pepper

... Investigation involved two vegetables (namely, green pepper and onion) and a wide range of ch... more ... Investigation involved two vegetables (namely, green pepper and onion) and a wide range of characteristic dimensions of samples and air ... Mathematical modeling of dehydration operations is important in the design and optimization of dryers (Brook and Bakker-Arkema, 1978 ...

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Research paper thumbnail of Microwave vacuum drying kinetics of some fruits

Microwave vacuum drying kinetics of three fruits (namely, apple, kiwi and pear) were studied by i... more Microwave vacuum drying kinetics of three fruits (namely, apple, kiwi and pear) were studied by introducing an one-parameter empirical mass transfer model, involving a characteristic parameter (drying constant), as a function of process variables. The model was tested with data produced in a microwave oven equipped with vacuum apparatus, using non-linear regression analysis. The investigation involved a wide range of

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Research paper thumbnail of Equilibrium moisture content and heat of desorption of some vegetables

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Water sorption isotherms of raisins, currants, figs, prunes and apricots

Journal of Food …, 1990

Bookmarks Related papers MentionsView impact