Special Issue "Modeling and Simulation of Energy Systems"

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Computational Methods".

Deadline for manuscript submissions: closed (31 October 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Thomas A. Adams II

Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton Ontario, Canada L8S 4L7
Website | E-Mail
Phone: +1 905-525-9140 x 24782
Interests: sustainable energy conversion processes; modelling and simulation; new technologies for sustainable liquid fuel production; semi-continuous chemical separation processes

Special Issue Information

Dear Colleagues,

One of the most important drivers of our economy is the production, management, conversion, and consumption of energy and energy products. It is fundamentally linked to many other important aspects of society, such as food production, water consumption, manufacturing, resource management, security, and the environment. Now more than ever, process systems engineers are in a position to address some of the most critical issues relating to energy systems and their impacts on the rest of the world. Advances in energy systems are being made at scales ranging from the international movement and trade of energy; industrial-scale refineries, biorefineries, and chemical plants; integrated energy systems for communities, districts, and neighbourhoods; and individual homes and buildings. The technologies involved can vary widely, such as traditional systems involving natural gas, petroleum, and transportation fuels, biofuels and bioproducts, synthetic and alternative fuels such as alcohols and ethers, nuclear energy, fuel cells, renewables such as wind and solar, and energy storage technologies of many varieties. All of these will be an important component of future of energy systems. Modeling and simulation plays a particularly important role in the development of these systems, since it is one of the most cost effective tools available for their design and analysis. In many cases, the use of models or simulations is the only way to make sound engineering judgements about new process concepts due to the massive scales involved.

This Special Issue on “Modeling and Simulation of Energy Systems” will curate novel advances in research which either use modeling and simulation as an important component of the analysis of energy systems, or, present the development of new and better models of energy systems or energy system components. In order to maximize impact, authors contributing to this Special Issue will be invited to deposit their process models in the open access repository for the process systems engineering community at PSEcommunity.org and/or provide as supplementary material. These may include contributions such as process simulation files, computer code, spreadsheets, model files, optimization codes, or other relevant digital objects used for modelling and simulation purposes with either commercial or open source software.

Topics include, but are not limited to:

  • The development of models or simulations of individual process units contained within energy systems
  • The development of models or simulations of energy process systems
  • Simulation techniques, software, algorithms, or other tools for modeling and simulation
  • Design, analysis, control, optimization, operation, planning, or scheduling of an energy system that employs models or simulations, such as techno-economic analyses, energy/exergy analyses, environmental or life cycle analyses, value and supply chains analysis, or other

Thanks and I hope you consider participating in this Special Issue.

Sincerely,

Prof. Dr. Thomas A. Adams II
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1100 CHF (Swiss Francs). Please note that for papers submitted after 30 June 2019 an APC of 1200 CHF applies. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Modeling
  • Simulation
  • Energy Systems
  • Systems Analysis
  • Tools
  • Algorithms
  • Software
  • Design
  • Process Systems Engineering

Published Papers (21 papers)

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Research

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Open AccessArticle Comparison of the Utilization of 110 °C and 120 °C Heat Sources in a Geothermal Energy System Using Organic Rankine Cycle (ORC) with R245fa, R123, and Mixed-Ratio Fluids as Working Fluids
Processes 2019, 7(2), 113; https://doi.org/10.3390/pr7020113
Received: 12 January 2019 / Revised: 2 February 2019 / Accepted: 15 February 2019 / Published: 21 February 2019
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Abstract
Binary cycle experiment as one of the Organic Rankine Cycle (ORC) technologies has been known to provide an improved alternate scenario to utilize waste energy with low temperatures. As such, a binary geothermal power plant simulator was developed to demonstrate the geothermal energy [...] Read more.
Binary cycle experiment as one of the Organic Rankine Cycle (ORC) technologies has been known to provide an improved alternate scenario to utilize waste energy with low temperatures. As such, a binary geothermal power plant simulator was developed to demonstrate the geothermal energy potential in Dieng, Indonesia. To better understand the geothermal potential, the laboratory experiment to study the ORC heat source mechanism that can be set to operate at fixed temperatures of 110 °C and 120 °C is conducted. For further performance analysis, R245fa, R123, and mixed ratio working fluids with mass flow rate varied from 0.1 kg/s to 0.2 kg/s were introduced as key parameters in the study. Data from the simulator were measured and analyzed under steady-state condition with a 20 min interval per given mass flow rate. Results indicate that the ORC system has better thermodynamic performance when operating the heat source at 120 °C than those obtained from 110 °C. Moreover, the R123 fluid produces the highest ORC efficiency with values between 9.4% and 13.5%. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessArticle Model-Based Cost Optimization of Double-Effect Water-Lithium Bromide Absorption Refrigeration Systems
Processes 2019, 7(1), 50; https://doi.org/10.3390/pr7010050
Received: 16 October 2018 / Revised: 11 January 2019 / Accepted: 17 January 2019 / Published: 19 January 2019
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Abstract
This work presents optimization results obtained for a double-effect H2O-LiBr absorption refrigeration system considering the total cost as minimization criterion, for a wide range of cooling capacity values. As a model result, the sizes of the process units and the corresponding [...] Read more.
This work presents optimization results obtained for a double-effect H2O-LiBr absorption refrigeration system considering the total cost as minimization criterion, for a wide range of cooling capacity values. As a model result, the sizes of the process units and the corresponding operating conditions are obtained simultaneously. In this paper, the effectiveness factor of each proposed heat exchanger is considered as a model optimization variable which allows (if beneficial, according to the objective function to be minimized) its deletion from the optimal solution, therefore, helping us to determine the optimal configuration. Several optimization cases considering different target levels of cooling capacity are solved. Among the major results, it was observed that the total cost is considerably reduced when the solution heat exchanger operating at low temperature is deleted compared to the configuration that includes it. Also, it was found that the effect of removing this heat exchanger is comparatively more significant with increasing cooling capacity levels. A reduction of 9.8% in the total cost was obtained for a cooling capacity of 16 kW (11,537.2 $·year−1 vs. 12,794.5 $·year−1), while a reduction of 12% was obtained for a cooling capacity of 100 kW (31,338.1 $·year−1 vs. 35,613.9 $·year−1). The optimization mathematical model presented in this work assists in selecting the optimal process configuration, as well as determining the optimal process unit sizes and operating conditions of refrigeration systems. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Building Block-Based Synthesis and Intensification of Work-Heat Exchanger Networks (WHENS)
Processes 2019, 7(1), 23; https://doi.org/10.3390/pr7010023
Received: 16 November 2018 / Revised: 30 December 2018 / Accepted: 1 January 2019 / Published: 7 January 2019
Cited by 1 | PDF Full-text (917 KB) | HTML Full-text | XML Full-text
Abstract
We provide a new method to represent all potential flowsheet configurations for the superstructure-based simultaneous synthesis of work and heat exchanger networks (WHENS). The new representation is based on only two fundamental elements of abstract building blocks. The first design element is the [...] Read more.
We provide a new method to represent all potential flowsheet configurations for the superstructure-based simultaneous synthesis of work and heat exchanger networks (WHENS). The new representation is based on only two fundamental elements of abstract building blocks. The first design element is the block interior that is used to represent splitting, mixing, utility cooling, and utility heating of individual streams. The second design element is the shared boundaries between adjacent blocks that permit inter-stream heat and work transfer and integration. A semi-restricted boundary represents expansion/compression of streams connected to either common (integrated) or dedicated (utility) shafts. A completely restricted boundary with a temperature gradient across it represents inter-stream heat integration. The blocks interact with each other via mass and energy flows through the boundaries when assembled in a two-dimensional grid-like superstructure. Through observation and examples from literature, we illustrate that our building block-based WHENS superstructure contains numerous candidate flowsheet configurations for simultaneous heat and work integration. This approach does not require the specification of work and heat integration stages. Intensified designs, such as multi-stream heat exchangers with varying pressures, are also included. We formulate a mixed-integer non-linear (MINLP) optimization model for WHENS with minimum total annual cost and demonstrate the capability of the proposed synthesis approach through a case study on liquefied energy chain. The concept of building blocks is found to be general enough to be used in possible discovery of non-intuitive process flowsheets involving heat and work exchangers. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessArticle Supercritical CO2 Transesterification of Triolein to Methyl-Oleate in a Batch Reactor: Experimental and Simulation Results
Processes 2019, 7(1), 16; https://doi.org/10.3390/pr7010016
Received: 16 October 2018 / Revised: 21 December 2018 / Accepted: 25 December 2018 / Published: 1 January 2019
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Abstract
In earlier work (Silva et al., 2016; Soh et al., 2014a; Soh et al., 2015), the supercritical CO2 transesterification of triolein to methyl-oleate using Nafion solid-acid catalyst and large methanol/triolein molar feed ratios was carried out. Herein, these ratios are adjusted (from [...] Read more.
In earlier work (Silva et al., 2016; Soh et al., 2014a; Soh et al., 2015), the supercritical CO2 transesterification of triolein to methyl-oleate using Nafion solid-acid catalyst and large methanol/triolein molar feed ratios was carried out. Herein, these ratios are adjusted (from 50–550) to evaluate the yield of fatty acid methyl esters in batch laboratory reactors as temperature is varied from 80–95 °C and pressure is varied from 8.0–9.65 MPa. Also, to better understand the effect of varying these operating parameters, batch reactor simulations using the Soave-Redlich-Kwong Equation of State (RK-ASPEN EOS) in ASPEN PLUS are carried-out. A single-reaction kinetic model is used and phase equilibrium is computed as the reactions proceed. Experimental data are compared with these results. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle A General Model for Estimating Emissions from Integrated Power Generation and Energy Storage. Case Study: Integration of Solar Photovoltaic Power and Wind Power with Batteries
Processes 2018, 6(12), 267; https://doi.org/10.3390/pr6120267
Received: 17 October 2018 / Revised: 5 December 2018 / Accepted: 8 December 2018 / Published: 18 December 2018
Cited by 1 | PDF Full-text (6440 KB) | HTML Full-text | XML Full-text
Abstract
The penetration of renewable power generation is increasing at an unprecedented pace. While the operating greenhouse gas (GHG) emissions of photovoltaic (PV) and wind power are negligible, their upstream emissions are not. The great challenge with the deployment of renewable power generators is [...] Read more.
The penetration of renewable power generation is increasing at an unprecedented pace. While the operating greenhouse gas (GHG) emissions of photovoltaic (PV) and wind power are negligible, their upstream emissions are not. The great challenge with the deployment of renewable power generators is their intermittent and variable nature. Current electric power systems balance these fluctuations primarily using natural gas fired power plants. Alternatively, these dynamics could be handled by the integration of energy storage technologies to store energy during renewable energy availability and discharge when needed. In this paper, we present a model for estimating emissions from integrated power generation and energy storage. The model applies to emissions of all pollutants, including greenhouse gases (GHGs), and to all storage technologies, including pumped hydroelectric and electrochemical storage. As a case study, the model is used to estimate the GHG emissions of electricity from systems that couple photovoltaic and wind generation with lithium-ion batteries (LBs) and vanadium redox flow batteries (VFBs). To facilitate the case study, we conducted a life cycle assessment (LCA) of photovoltaic (PV) power, as well as a synthesis of existing wind power LCAs. The PV LCA is also used to estimate the emissions impact of a common PV practice that has not been comprehensively analyzed by LCA—solar tracking. The case study of renewables and battery storage indicates that PV and wind power remain much less carbon intensive than fossil-based generation, even when coupled with large amounts of LBs or VFBs. Even the most carbon intensive renewable power analyzed still emits only ~25% of the GHGs of the least carbon intensive mainstream fossil power. Lastly, we find that the pathway to minimize the GHG emissions of power from a coupled system depends upon the generator. Given low-emission generation (<50 gCO2e/kWh), the minimizing pathway is the storage technology with lowest production emissions (VFBs over LBs for our case study). Given high-emission generation (>200 gCO2e/kWh), the minimizing pathway is the storage technology with highest round-trip efficiency (LBs over VFBs). Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Offshore Power Plants Integrating a Wind Farm: Design Optimisation and Techno-Economic Assessment Based on Surrogate Modelling
Processes 2018, 6(12), 249; https://doi.org/10.3390/pr6120249
Received: 15 October 2018 / Revised: 16 November 2018 / Accepted: 30 November 2018 / Published: 4 December 2018
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Abstract
The attempt to reduce the environmental impact of the petroleum sector has been the driver for researching energy efficient solutions to supply energy offshore. An attractive option is to develop innovative energy systems including renewable and conventional sources. The paper investigates the possibility [...] Read more.
The attempt to reduce the environmental impact of the petroleum sector has been the driver for researching energy efficient solutions to supply energy offshore. An attractive option is to develop innovative energy systems including renewable and conventional sources. The paper investigates the possibility to integrate a wind farm into an offshore combined cycle power plant. The design of such an energy system is a complex task as many, possibly conflicting, requirements have to be satisfied. The large variability of operating conditions due to the intermittent nature of wind and to the different stages of exploitation of an oil field makes it challenging to identify the optimal parameters of the combined cycle and the optimal size of the wind farm. To deal with the issue, an optimisation procedure was developed that was able to consider the performance of the system at a number of relevant off-design conditions in the definition of the optimal design. A surrogate modelling technique was applied in order to reduce the computational effort that would otherwise make the optimisation process unfeasible. The developed method was applied to a case study and the resulting optimal designs were assessed and compared to other concepts, with or without wind power integration. The proposed offshore power plant returned the best environmental performance, as it was able to significantly cut the total carbon dioxide (CO2) emissions in comparison to all the other concepts evaluated. The economic analysis showed the difficulty to repay the additional investment for a wind farm and the necessity of favourable conditions, in terms of gas and carbon dioxide (CO2) prices. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Development of a Dynamic Model and Control System for Load-Following Studies of Supercritical Pulverized Coal Power Plants
Processes 2018, 6(11), 226; https://doi.org/10.3390/pr6110226
Received: 8 October 2018 / Revised: 6 November 2018 / Accepted: 14 November 2018 / Published: 17 November 2018
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Abstract
Traditional energy production plants are increasingly forced to cycle their load and operate under low-load conditions in response to growth in intermittent renewable generation. A plant-wide dynamic model of a supercritical pulverized coal (SCPC) power plant has been developed in the Aspen Plus [...] Read more.
Traditional energy production plants are increasingly forced to cycle their load and operate under low-load conditions in response to growth in intermittent renewable generation. A plant-wide dynamic model of a supercritical pulverized coal (SCPC) power plant has been developed in the Aspen Plus Dynamics® (APD) software environment and the impact of advanced control strategies on the transient responses of the key variables to load-following operation and disturbances can be studied. Models of various key unit operations, such as the steam turbine, are developed in Aspen Custom Modeler® (ACM) and integrated in the APD environment. A coordinated control system (CCS) is developed above the regulatory control layer. Three control configurations are evaluated for the control of the main steam; the reheat steam temperature is also controlled. For studying servo control performance of the CCS, the load is decreased from 100% to 40% at a ramp rate of 3% load per min. The impact of a disturbance due to a change in the coal feed composition is also studied. The CCS is found to yield satisfactory performance for both servo control and disturbance rejection. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessArticle Waste Fuel Combustion: Dynamic Modeling and Control
Processes 2018, 6(11), 222; https://doi.org/10.3390/pr6110222
Received: 15 October 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 13 November 2018
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Abstract
The focus of this study is to present the adherent transients that accompany the combustion of waste derived fuels. This is accomplished, in large, by developing a dynamic model of the process, which can then be used for control purposes. Traditional control measures [...] Read more.
The focus of this study is to present the adherent transients that accompany the combustion of waste derived fuels. This is accomplished, in large, by developing a dynamic model of the process, which can then be used for control purposes. Traditional control measures typically applied in the heat and power industry, i.e., PI (proportional-integral) controllers, might not be robust enough to handle the the accompanied transients associated with new fuels. Therefore, model predictive control is introduced as a means to achieve better combustion stability under transient conditions. The transient behavior of refuse derived fuel is addressed by developing a dynamic modeling library. Within the library, there are two models. The first is for assessing the performance of the heat exchangers to provide operational assistance for maintenance scheduling. The second model is of a circulating fluidized bed block, which includes combustion and steam (thermal) networks. The library has been validated using data from a 160 MW industrial installation located in Västerås, Sweden. The model can predict, with satisfactory accuracy, the boiler bed and riser temperatures, live steam temperature, and boiler load. This has been achieved by using process sensors for the feed-in streams. Based on this model three different control schemes are presented: a PI control scheme, model predictive control with feedforward, and model predictive control without feedforward. The model predictive control with feedforward has proven to give the best performance as it can maintain stable temperature profiles throughout the process when a measured disturbance is initiated. Furthermore, the implemented control incorporates the introduction of a soft-sensor for measuring the minimum fluidization velocity to maintain a consistent level of fluidization in the boiler for deterring bed material agglomeration. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Diagnostics-Oriented Modelling of Micro Gas Turbines for Fleet Monitoring and Maintenance Optimization
Processes 2018, 6(11), 216; https://doi.org/10.3390/pr6110216
Received: 14 October 2018 / Revised: 29 October 2018 / Accepted: 31 October 2018 / Published: 2 November 2018
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Abstract
The market for the small-scale micro gas turbine is expected to grow rapidly in the coming years. Especially, utilization of commercial off-the-shelf components is rapidly reducing the cost of ownership and maintenance, which is paving the way for vast adoption of such units. [...] Read more.
The market for the small-scale micro gas turbine is expected to grow rapidly in the coming years. Especially, utilization of commercial off-the-shelf components is rapidly reducing the cost of ownership and maintenance, which is paving the way for vast adoption of such units. However, to meet the high-reliability requirements of power generators, there is an acute need of a real-time monitoring system that will be able to detect faults and performance degradation, and thus allow preventive maintenance of these units to decrease downtime. In this paper, a micro gas turbine based combined heat and power system is modelled and used for development of physics-based diagnostic approaches. Different diagnostic schemes for performance monitoring of micro gas turbines are investigated. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Effect of Tariff Policy and Battery Degradation on Optimal Energy Storage
Processes 2018, 6(10), 204; https://doi.org/10.3390/pr6100204
Received: 15 September 2018 / Revised: 19 October 2018 / Accepted: 19 October 2018 / Published: 22 October 2018
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Abstract
In the context of an increasing participation of renewable energy in the electricity market, demand response is a strategy promoted by electricity companies to balance the non-programmable supply of electricity with its usage. Through the use of differential electricity prices, a switch in [...] Read more.
In the context of an increasing participation of renewable energy in the electricity market, demand response is a strategy promoted by electricity companies to balance the non-programmable supply of electricity with its usage. Through the use of differential electricity prices, a switch in energy consumption patterns is stimulated. In recent years, energy self-storage in batteries has been proposed as a way to take advantage of differential prices without a major disruption in daily routines. Although a promising solution, charge and discharge cycles also degrade batteries, thus expected savings in the energy bill may actually be non-existent if these savings are counterbalanced by the capacity lost by the battery. In this work a convex optimization problem that finds the operating schedule for a battery and includes the effects of current-induced degradation is presented. The goal is to have a tool that facilitates for a consumer the evaluation of the convenience of installing a battery-based energy storage system under different but given assumptions of electricity and battery prices. The problem is solved assuming operation of a commercial Li-ion under two very different yet representative electricity pricing policies. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Approximating Nonlinear Relationships for Optimal Operation of Natural Gas Transport Networks
Processes 2018, 6(10), 198; https://doi.org/10.3390/pr6100198
Received: 4 September 2018 / Revised: 13 October 2018 / Accepted: 15 October 2018 / Published: 18 October 2018
Cited by 1 | PDF Full-text (2151 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The compressor fuel cost minimization problem (FCMP) for natural gas pipelines is a relevant problem because of the substantial energy consumption of compressor stations transporting the large global demand for natural gas. The common method for modeling the FCMP is to assume key [...] Read more.
The compressor fuel cost minimization problem (FCMP) for natural gas pipelines is a relevant problem because of the substantial energy consumption of compressor stations transporting the large global demand for natural gas. The common method for modeling the FCMP is to assume key modeling parameters such as the friction factor, compressibility factor, isentropic exponent, and compressor efficiency to be constants, and their nonlinear relationships to the system operating conditions are ignored. Previous work has avoided the complexity associated with the nonlinear relationships inherent in the FCMP to avoid unreasonably long solution times for practical transportation systems. In this paper, a mixed-integer linear programming (MILP) based method is introduced to generate piecewise-linear functions that approximate the previously ignored nonlinear relationships. The MILP determines the optimal break-points and orientation of the linear segments so that approximation error is minimized. A novel FCMP model that includes the piecewise-linear approximations is applied in a case study on three simple gas networks. The case study shows that the novel FCMP model captures the nonlinear relationships with a high degree of accuracy and only marginally increases solution time compared to the common simplified FCMP model. The common simplified model is found to produce solutions with high error and infeasibility when applied on a rigorous simulation. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Simulation of Dual Mixed Refrigerant Natural Gas Liquefaction Processes Using a Nonsmooth Framework
Processes 2018, 6(10), 193; https://doi.org/10.3390/pr6100193
Received: 26 September 2018 / Revised: 11 October 2018 / Accepted: 15 October 2018 / Published: 17 October 2018
Cited by 2 | PDF Full-text (530 KB) | HTML Full-text | XML Full-text
Abstract
Natural gas liquefaction is an energy intensive process where the feed is cooled from ambient temperature down to cryogenic temperatures. Different liquefaction cycles exist depending on the application, with dual mixed refrigerant processes normally considered for the large-scale production of Liquefied Natural Gas [...] Read more.
Natural gas liquefaction is an energy intensive process where the feed is cooled from ambient temperature down to cryogenic temperatures. Different liquefaction cycles exist depending on the application, with dual mixed refrigerant processes normally considered for the large-scale production of Liquefied Natural Gas (LNG). Large temperature spans and small temperature differences in the heat exchangers make the liquefaction processes difficult to analyze. Exergetic losses from irreversible heat transfer increase exponentially with a decreasing temperature at subambient conditions. Consequently, an accurate and robust simulation tool is paramount to allow designers to make correct design decisions. However, conventional process simulators, such as Aspen Plus, suffer from significant drawbacks when modeling multistream heat exchangers. In particular, no rigorous checks exist to prevent temperature crossovers. Limited degrees of freedom and the inability to solve for stream variables other than outlet temperatures also makes such tools inflexible to use, often requiring the user to resort to a manual iterative procedure to obtain a feasible solution. In this article, a nonsmooth, multistream heat exchanger model is used to develop a simulation tool for two different dual mixed refrigerant processes. Case studies are presented for which Aspen Plus fails to obtain thermodynamically feasible solutions. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessArticle Dynamic Modeling and Control of an Integrated Reformer-Membrane-Fuel Cell System
Processes 2018, 6(9), 169; https://doi.org/10.3390/pr6090169
Received: 30 July 2018 / Revised: 10 September 2018 / Accepted: 11 September 2018 / Published: 17 September 2018
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Abstract
Owing to the pollution free nature, higher efficiency and noise free operation, fuel cells have been identified as ideal energy sources for the future. To avoid direct storage of hydrogen due to safety considerations, storing hydrocarbon fuel such as methane and suitably reforming [...] Read more.
Owing to the pollution free nature, higher efficiency and noise free operation, fuel cells have been identified as ideal energy sources for the future. To avoid direct storage of hydrogen due to safety considerations, storing hydrocarbon fuel such as methane and suitably reforming in situ for hydrogen production offers merit for further investigation. Separating the resulting hydrogen in the reformate using membrane separation can directly feed pure gas to the anode side of fuel cell for power generation. Despite the numerous works reported in literature on the dynamic and steady state modeling and analysis of reformers, membrane separation units and fuel cell systems, there has been limited work on an analysis of the integrated system consisting of all the three components. This study focuses on the mathematical modeling and analysis of the integrated reformer, membrane, fuel cell system from first principles in a dynamic framework. A multi loop control strategy is developed and implemented on the mathematical model of the integrated system in which appropriate controllers based on the system dynamics are designed to examine and study the overall closed loop performance to achieve rapidly fluctuating target power demand and rejection of reformer feed and fuel cell coolant temperature disturbances. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessArticle Energy and Exergy Analysis of the S-CO2 Brayton Cycle Coupled with Bottoming Cycles
Processes 2018, 6(9), 153; https://doi.org/10.3390/pr6090153
Received: 11 July 2018 / Revised: 23 August 2018 / Accepted: 28 August 2018 / Published: 1 September 2018
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Abstract
Supercritical carbon dioxide (S-CO2) Brayton cycles (BC) are soon to be a competitive and environment friendly power generation technology. Progressive technological developments in turbo-machineries and heat exchangers have boosted the idea of using S-CO2 in a closed-loop BC. This paper [...] Read more.
Supercritical carbon dioxide (S-CO2) Brayton cycles (BC) are soon to be a competitive and environment friendly power generation technology. Progressive technological developments in turbo-machineries and heat exchangers have boosted the idea of using S-CO2 in a closed-loop BC. This paper describes and discusses energy and exergy analysis of S-CO2 BC in cascade arrangement with a secondary cycle using CO2, R134a, ammonia, or argon as working fluids. Pressure drop in the cycle is considered, and its effect on the overall performance is investigated. No specific heat source is considered, thus any heat source capable of providing temperature in the range from 500 °C to 850 °C can be utilized, such as solar energy, gas turbine exhaust, nuclear waste heat, etc. The commercial software ‘Aspen HYSYS version 9’ (Aspen Technology, Inc., Bedford, MA, USA) is used for simulations. Comparisons with the literature and simulation results are discussed first for the standalone S-CO2 BC. Energy analysis is done for the combined cycle to inspect the parameters affecting the cycle performance. The second law efficiency is calculated, and exergy losses incurred in different components of the cycle are discussed. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Valorization of Shale Gas Condensate to Liquid Hydrocarbons through Catalytic Dehydrogenation and Oligomerization
Processes 2018, 6(9), 139; https://doi.org/10.3390/pr6090139
Received: 15 July 2018 / Revised: 11 August 2018 / Accepted: 14 August 2018 / Published: 23 August 2018
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Abstract
The recent shale gas boom has transformed the energy landscape of the United States. Compared to natural gas, shale resources contain a substantial amount of condensate and natural gas liquids (NGLs). Many shale basin regions located in remote areas are lacking the infrastructure [...] Read more.
The recent shale gas boom has transformed the energy landscape of the United States. Compared to natural gas, shale resources contain a substantial amount of condensate and natural gas liquids (NGLs). Many shale basin regions located in remote areas are lacking the infrastructure to distribute the extracted NGLs to other regions—particularly the Gulf Coast, a major gas processing region. Here we present a shale gas transformation process that converts NGLs in shale resources into liquid hydrocarbons, which are easier to transport from these remote basins than NGL or its constituents. This process involves catalytic dehydrogenation followed by catalytic oligomerization. Thermodynamic process analysis shows that this process has the potential to be more energy efficient than existing NGL-to-liquid fuel (NTL) technologies. In addition, our estimated payback period for this process is within the average lifetime of shale gas wells. The proposed process holds the promise to be an energy efficient and economically attractive step to valorize condensate in remote shale basins. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Improving Flexibility and Energy Efficiency of Post-Combustion CO2 Capture Plants Using Economic Model Predictive Control
Processes 2018, 6(9), 135; https://doi.org/10.3390/pr6090135
Received: 30 July 2018 / Revised: 15 August 2018 / Accepted: 17 August 2018 / Published: 21 August 2018
Cited by 3 | PDF Full-text (1035 KB) | HTML Full-text | XML Full-text
Abstract
To reduce CO2 emissions from power plants, electricity companies have diversified their generation sources. Fossil fuels, however, still remain an integral energy generation source as they are more reliable compared to the renewable energy sources. This diversification as well as changing electricity [...] Read more.
To reduce CO 2 emissions from power plants, electricity companies have diversified their generation sources. Fossil fuels, however, still remain an integral energy generation source as they are more reliable compared to the renewable energy sources. This diversification as well as changing electricity demand could hinder effective economical operation of an amine-based post-combustion CO 2 capture (PCC) plant attached to the power plant to reduce CO 2 emissions. This is as a result of large fluctuations in the flue gas flow rate and unavailability of steam from the power plant. To tackle this problem, efficient control algorithms are necessary. In this work, tracking and economic model predictive controllers are applied to a PCC plant and their economic performance is compared under different scenarios. The results show that economic model predictive control has a potential to improve the economic performance and energy efficiency of the amine-based PCC process up to 6% and 7%, respectively, over conventional model predictive control. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Dynamic Optimization of a Subcritical Steam Power Plant Under Time-Varying Power Load
Processes 2018, 6(8), 114; https://doi.org/10.3390/pr6080114
Received: 2 June 2018 / Revised: 13 July 2018 / Accepted: 21 July 2018 / Published: 3 August 2018
Cited by 1 | PDF Full-text (906 KB) | HTML Full-text | XML Full-text
Abstract
The increasing variability in power plant load in response to a wildly uncertain electricity market and the need to to mitigate CO2 emissions, lead power plant operators to explore advanced options for efficiency optimization. Model-based, system-scale dynamic simulation and optimization are useful [...] Read more.
The increasing variability in power plant load in response to a wildly uncertain electricity market and the need to to mitigate CO2 emissions, lead power plant operators to explore advanced options for efficiency optimization. Model-based, system-scale dynamic simulation and optimization are useful tools in this effort and are the subjects of the work presented here. In prior work, a dynamic model validated against steady-state data from a 605 MW subcritical power plant was presented. This power plant model was used as a test-bed for dynamic simulations, in which the coal load was regulated to satisfy a varying power demand. Plant-level control regulated the plant load to match an anticipated trajectory of the power demand. The efficiency of the power plant’s operation at varying loads was optimized through a supervisory control architecture that performs set point optimization on the regulatory controllers. Dynamic optimization problems were formulated to search for optimal time-varying input trajectories that satisfy operability and safety constraints during the transition between plant states. An improvement in time-averaged efficiency of up to 1.8% points was shown to be feasible with corresponding savings in coal consumption of 184.8 tons/day and a carbon footprint decrease of 0.035 kg/kWh. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle A Differentiable Model for Optimizing Hybridization of Industrial Process Heat Systems with Concentrating Solar Thermal Power
Processes 2018, 6(7), 76; https://doi.org/10.3390/pr6070076
Received: 6 June 2018 / Revised: 18 June 2018 / Accepted: 19 June 2018 / Published: 23 June 2018
Cited by 1 | PDF Full-text (2109 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A dynamic model of a concentrating solar thermal array and thermal energy storage system is presented that is differentiable in the design decision variables: solar aperture area and thermal energy storage capacity. The model takes as input the geographic location of the system [...] Read more.
A dynamic model of a concentrating solar thermal array and thermal energy storage system is presented that is differentiable in the design decision variables: solar aperture area and thermal energy storage capacity. The model takes as input the geographic location of the system of interest and the corresponding discrete hourly solar insolation data, and calculates the annual thermal and economic performance of a particular design. The model is formulated for use in determining optimal hybridization strategies for industrial process heat applications using deterministic gradient-based optimization algorithms. Both convex and nonconvex problem formulations are presented. To demonstrate the practicability of the models, they were applied to four different case studies for three disparate geographic locations in the US. The corresponding optimal design problems were solved to global optimality using deterministic gradient-based optimization algorithms. The model and optimization-based analysis provide a rigorous quantitative design and investment decision-making framework for engineering design and project investment workflows. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle Modelling of a Naphtha Recovery Unit (NRU) with Implications for Process Optimization
Processes 2018, 6(7), 74; https://doi.org/10.3390/pr6070074
Received: 30 May 2018 / Revised: 16 June 2018 / Accepted: 18 June 2018 / Published: 22 June 2018
PDF Full-text (4418 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The naphtha recovery unit (NRU) is an integral part of the processes used in the oil sands industry for bitumen extraction. The principle role of the NRU is to recover naphtha from the tailings for reuse in this process. This process is energy-intensive, [...] Read more.
The naphtha recovery unit (NRU) is an integral part of the processes used in the oil sands industry for bitumen extraction. The principle role of the NRU is to recover naphtha from the tailings for reuse in this process. This process is energy-intensive, and environmental guidelines for naphtha recovery must be met. Steady-state models for the NRU system are developed in this paper using two different approaches. The first approach is a statistical, data-based modelling approach where linear regression models have been developed using Minitab® from plant data collected during a performance test. The second approach involves the development of a first-principles model in Aspen Plus® based on the NRU process flow diagram. A novel refinement to this latter model, called “withdraw and remix”, is proposed based on comparing actual plant data to model predictions around the two units used to separate water and naphtha. The models developed in this paper suggest some interesting ideas for the further optimization of the process, in that it may be possible to achieve the required naphtha recovery using less energy. More plant tests are required to validate these ideas. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Open AccessFeature PaperArticle An Integrated Approach to Water-Energy Nexus in Shale-Gas Production
Processes 2018, 6(5), 52; https://doi.org/10.3390/pr6050052
Received: 18 April 2018 / Revised: 3 May 2018 / Accepted: 4 May 2018 / Published: 8 May 2018
Cited by 8 | PDF Full-text (4834 KB) | HTML Full-text | XML Full-text
Abstract
Shale gas production is associated with significant usage of fresh water and discharge of wastewater. Consequently, there is a necessity to create proper management strategies for water resources in shale gas production and to integrate conventional energy sources (e.g., shale gas) with renewables [...] Read more.
Shale gas production is associated with significant usage of fresh water and discharge of wastewater. Consequently, there is a necessity to create proper management strategies for water resources in shale gas production and to integrate conventional energy sources (e.g., shale gas) with renewables (e.g., solar energy). The objective of this study is to develop a design framework for integrating water and energy systems including multiple energy sources, the cogeneration process and desalination technologies in treating wastewater and providing fresh water for shale gas production. Solar energy is included to provide thermal power directly to a multi-effect distillation plant (MED) exclusively (to be more feasible economically) or indirect supply through a thermal energy storage system. Thus, MED is driven by direct or indirect solar energy and excess or direct cogeneration process heat. The proposed thermal energy storage along with the fossil fuel boiler will allow for the dual-purpose system to operate at steady-state by managing the dynamic variability of solar energy. Additionally, electric production is considered to supply a reverse osmosis plant (RO) without connecting to the local electric grid. A multi-period mixed integer nonlinear program (MINLP) is developed and applied to discretize the operation period to track the diurnal fluctuations of solar energy. The solution of the optimization program determines the optimal mix of solar energy, thermal storage and fossil fuel to attain the maximum annual profit of the entire system. A case study is solved for water treatment and energy management for Eagle Ford Basin in Texas. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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Review

Jump to: Research

Open AccessFeature PaperReview Modeling and Simulation of Energy Systems: A Review
Processes 2018, 6(12), 238; https://doi.org/10.3390/pr6120238
Received: 12 October 2018 / Revised: 14 November 2018 / Accepted: 18 November 2018 / Published: 23 November 2018
Cited by 3 | PDF Full-text (2532 KB) | HTML Full-text | XML Full-text
Abstract
Energy is a key driver of the modern economy, therefore modeling and simulation of energy systems has received significant research attention. We review the major developments in this area and propose two ways to categorize the diverse contributions. The first categorization is according [...] Read more.
Energy is a key driver of the modern economy, therefore modeling and simulation of energy systems has received significant research attention. We review the major developments in this area and propose two ways to categorize the diverse contributions. The first categorization is according to the modeling approach, namely into computational, mathematical, and physical models. With this categorization, we highlight certain novel hybrid approaches that combine aspects of the different groups proposed. The second categorization is according to field namely Process Systems Engineering (PSE) and Energy Economics (EE). We use the following criteria to illustrate the differences: the nature of variables, theoretical underpinnings, level of technological aggregation, spatial and temporal scales, and model purposes. Traditionally, the Process Systems Engineering approach models the technological characteristics of the energy system endogenously. However, the energy system is situated in a broader economic context that includes several stakeholders both within the energy sector and in other economic sectors. Complex relationships and feedback effects exist between these stakeholders, which may have a significant impact on strategic, tactical, and operational decision-making. Leveraging the expertise built in the Energy Economics field on modeling these complexities may be valuable to process systems engineers. With this categorization, we present the interactions between the two fields, and make the case for combining the two approaches. We point out three application areas: (1) optimal design and operation of flexible processes using demand and price forecasts, (2) sustainability analysis and process design using hybrid methods, and (3) accounting for the feedback effects of breakthrough technologies. These three examples highlight the value of combining Process Systems Engineering and Energy Economics models to get a holistic picture of the energy system in a wider economic and policy context. Full article
(This article belongs to the Special Issue Modeling and Simulation of Energy Systems)
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