Ferenc Friedler

7004036558

Publications - 56

Exhaustive enumeration of heat exchanger networks with minimum utility consumption using graph-theoretic approach

Ákos Orosz Dhanaraj Turunawarasu Viknesh Andiappan Bing Shen How Jean Pimentel Sin Yong Teng Lip Siang Yeo Ferenc Friedler

Publication Name: Energy

Publication Date: 2025-10-30

Volume: 335

Issue: Unknown

Page Range: Unknown

Description:

Enhancement in energy recovery is always an essential element that requires academic spotlights to ensure its capability to contribute towards carbon neutrality. Recent works have extended to cover multi-solution heat exchanger networks (HEN) synthesis instead of generating a single best solution, which is not guaranteed to be practical. Nevertheless, owing to the technical challenges of synthesising all feasible networks, none of the existing works attempts to comprehensively elucidate how network topologies affect the network cost. To address this gap, P-HENS, a graph theoretic-based HEN synthesis tool, was utilised to generate the set of all heat exchanger networks with minimum utility consumption. Its effectiveness is demonstrated through an illustrative case study, which eventually generates more than 45,000 HENs. The impacts of structural variables on the cost, including the number of exchangers and the stream pairings, were analysed. The cost range of the networks was identified, revealing cost differences of 30 % despite minimum utility consumption or 15 % despite the minimum number of exchangers. Key stream pairs required to meet maximum energy recovery and influence cost were identified, leading to recommendations for improving solution searches. The solution set and the insight from this work are available to the research community for further analysis, offering valuable insights to enhance energy integration in the industry.

Open Access: Yes

DOI: 10.1016/j.energy.2025.137898

Short-period supply reliability evaluation of a gas pipeline network based on transient operation optimization and support vector regression

Lili Zuo Qian Chen Bohong Wang Kai Yang Jing Yan Petar Sabev Varbanov Ferenc Friedler Xiaokai Xing

Publication Name: Energy

Publication Date: 2025-09-15

Volume: 331

Issue: Unknown

Page Range: Unknown

Description:

The gas pipeline network is a critical infrastructure connecting downstream customers and upstream sources, and the gas supply condition of the gas network directly impacts people's lives. In this paper, a novel methodology is proposed to evaluate the short-period supply reliability of a gas pipeline system based on transient operation optimization and support vector regression. Firstly, supply and demand uncertainty characteristics are analyzed, and representative scenarios are selected through the improved Latin Hypercube Sampling method. Secondly, the transient peak-shaving characteristics are studied, and the physical transient peak-shaving operation optimization model is established to evaluate the satisfaction rate of gas customers and the system under representative scenarios. Then the Support Vector Regression model based on the improved Particle Swarm Optimization is established to predict the satisfaction rate of the customer or system under each random scenario, and the probabilities under different satisfaction degrees of the customer and system are given to reflect the supply reliability of a gas network. The proposed integrated methodology is verified by a specific gas pipeline system, and the results show that the maximum and the mean absolute error of the predicted satisfaction rate of the system's demand quantity can be reduced to 0.0070 and 0.0009, and the time consumed for the evaluation process can be reduced by 95 % compared to the traditional pure physical model. The proposed methodology can lay a solid foundation for the grasp of the short-period supply reliability of gas networks.

Open Access: Yes

DOI: 10.1016/j.energy.2025.136923

Multi-Solution Heat Exchanger Network Synthesis for Turbo-Expander-Based Cryogenic CO2 Capture Technology

Ákos Orosz Jaka Sunarso Dhanaraj Turunawarasu Viknesh Andiappan Bing Shen How Yat Choy Wong Ferenc Friedler

Publication Name: Industrial and Engineering Chemistry Research

Publication Date: 2025-01-22

Volume: 64

Issue: 3

Page Range: 1664-1679

Description:

Cryogenic separation of CO2 is a potential technology that can benefit from energy efficiency improvements. However, the current conventional and emerging cryogenic technologies face challenges in terms of high utility consumption. The high utility requirement leads to increasing operational costs and emissions due to the production of required utilities from external energy sources. This issue can be solved if the heat recovery potential of the technology can be realized. Heat recovery enables further improvement in energy efficiency that is required to elevate the feasibility of cryogenic separation. This paper explores heat recovery opportunities between hot and cold streams in a novel cryogenic CO2 capture technology known as Turbo-Expander-based Cryogenic Distillation (CryoDT). This is achieved using P-HENS, a P-graph-based heat exchanger network synthesis tool where multiple feasible heat exchanger network configurations are generated to determine the options that effectively recover process heat to reduce utility consumption. Moreover, the solutions generated by P-HENS are benchmarked with other tools like Aspen Energy Analyzer, by comparing the number of required heat exchangers, along with the associated capital and operating costs. For the predefined hot and cold process streams of the novel technology, the total number of heat exchangers present in the network was lower in the recommended design using P-HENS (i.e., 9 heat exchangers) as opposed to Aspen Energy Analyzer (16 heat exchangers) while maintaining similar energy consumption levels. This indicates that there is a further opportunity to reduce capital costs as a result of less heat exchangers. The CryoDT configuration that is integrated with a heat exchanger network offers significant economic advantages as opposed to other existing cryogenic processes in the market such as the Ryan Holmes and Controlled Freeze Zone (CFZ) processes. Despite its high capital cost, the CryoDT process demonstrates significantly lower operating cost relative to the other two processes. Hence, while the initial investment is substantial, the CryoDT process is much more cost efficient to operate. The low operating cost is attributed to its higher energy efficiency and minimal energy penalties, with only 0.26 GJ/tonne of CO2 compared with 0.82 GJ/tonne of CO2 for the CFZ process and 2.33 GJ/tonne of CO2 for Ryan Holmes. In contrast, the Ryan Holmes process, despite its low capital cost, incurs extremely high annual operational costs, rendering it less economic in the long term. The CFZ process, with its moderate operating cost, presents a balance between capital cost and operational efficiency.

Open Access: Yes

DOI: 10.1021/acs.iecr.4c03469

Control-Oriented Model for Energy-Efficient Electric Vehicle

Tamás Luspay Zoltan Pusztai Ferenc Friedler

Publication Name: Proceedings of the International Symposium on Applied Machine Intelligence and Informatics Sami

Publication Date: 2025-01-01

Volume: Unknown

Issue: Unknown

Page Range: 299-304

Description:

In this paper, a control-oriented Linear Parameter Varying (LPV) model of an energy efficient electric vehicle is proposed, designed for model-based control to minimize energy consumption. The control inputs of the model include the torque reference and the actual cornering radius. The LPV model assesses the impact of cornering on driving resistances and, consequently, on energy consumption, which represents a novel approach. Due to the driving characteristics and the model nonlinear dynamics of the vehicle, a velocity-linearization based method was applied to obtain the parameter-dependent form. The obtained LPV model was then validated by using logged driving data, showing a root mean square error (RMSE) of 0.4682 m/s compared to the measured speed profile, thereby confirming the model's accuracy. The proposed LPV model can be utilized to develop energy-efficient driving strategies, making it highly relevant for the design and operation of energy-efficient vehicles.

Open Access: Yes

DOI: 10.1109/SAMI63904.2025.10883184

The P-graph application extension in multi-period P2P energy trading

Ákos Orosz Jaka Sunarso Bing Shen How Wei Dong Leong Sin Yong Teng Karen Gah Hie Kong Alvin Guo Jian Lee Ferenc Friedler

Publication Name: Renewable and Sustainable Energy Reviews

Publication Date: 2024-08-01

Volume: 200

Issue: Unknown

Page Range: Unknown

Description:

An optimization model that incorporates all combinatorically feasible inter-plant collaboration networks is developed using P-graph. It has been theoretically proven that time-sliced-based energy planning optimization has positive impacts and is capable of achieving carbon emissions reduction goals and minimizing costs simultaneously. However, as the number of entities increased, an exponential growth in possible combinatorial feasible coalitions is anticipated. Therefore, an extension of the P-graph optimization tool that is capable of generating all possible outcomes in multi-period P2P energy trading – PEP (P-graph for energy planning) is developed. The PEP software can be effectively used in modelling complex process networks graphically and solving optimization problems with the combined advantages of combinatorial algorithms and mathematical programming. In this paper, a systematic framework for implementing P2P energy trading using PEP software is proposed and demonstrated using a real-life case study.

Open Access: Yes

DOI: 10.1016/j.rser.2024.114544

Driving Strategy Optimization in Experimental Electric Vehicles: A Study on Optimization Algorithms †

Zoltan Pusztai Ferenc Szauter Ferenc Friedler

Publication Name: Engineering Proceedings

Publication Date: 2024-01-01

Volume: 79

Issue: 1

Page Range: Unknown

Description:

In this paper, the driving strategy simulations for a single-seat, lightweight, energy-efficient experimental electric vehicle are introduced. The vehicle’s operation is simulated using a developed measurement-based vehicle model in the simulation environment. The optimization was performed for the UniTrack platform at the ZalaZone proving ground using the algorithms Particle Swarm Optimization (PSO) and Genetic Algorithm (GA), with different optimization settings corresponding to varying iterations and initial population/swarm sizes. A 2.95% difference was observed between the least effective and the best PSO results, where both the number of iterations and swarm size were doubled. This demonstrates the effectiveness of PSO in solving the presented driving strategy problem, even when using fewer iterations and a smaller swarm size.

Open Access: Yes

DOI: 10.3390/engproc2024079042

Optimized Eco-Driving with Real-Time Telemetry in a Lightweight Electric Vehicle

Zoltan Pusztai István Kecskeméti Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2024-01-01

Volume: 114

Issue: Unknown

Page Range: 877-882

Description:

In this paper, the application of an advanced telemetry system is introduced, which is used to monitor an electric, energy-efficient experimental urban vehicle. The system enables real-time observation of both the pilot's actions and vehicle parameters. The vehicle's pilot drives according to a predetermined driving strategy, optimized for minimizing energy consumption during vehicle operation. The telemetry system aims to provide real-time information about the pilot's driving and deviations from the predetermined strategy, offering additional opportunities for correction during operation. Additionally, it facilitates real-time observation of all vehicle and sensor data on the vehicle's CAN network. The paper discusses the determination of the driving strategy and presents its graphical representation for the pilot. A detailed description of the telemetry system's operation through wireless connection is provided in the paper. In terms of implementation, the driving strategy was formulated using MATLAB through optimization, while graphical display, data collection, and telemetry system development were implemented in the LabVIEW environment. The functionality of the created energy-efficient driving support framework was examined under real driving conditions. The application of the telemetry system and proposed hybrid optimization approach helped to further reduce the energy consumption by 8.54%.

Open Access: Yes

DOI: 10.3303/CET24114147

Electrification of oil refineries through multi-objective multi-period graph-theoretical planning: A crude distillation unit case study

Ákos Orosz Bing Shen How Sin Yong Teng Abdulqader Bin Sahl Ferenc Friedler

Publication Name: Journal of Cleaner Production

Publication Date: 2024-01-01

Volume: 434

Issue: Unknown

Page Range: Unknown

Description:

Electrification using renewable energy sources is the key to paving a sustainable and cleaner future for the oil and gas sector, which is known to be a significant carbon dioxide emitter. Nevertheless, the suitability of the electrification designs heavily depends on the seasonal availability of renewable energy sources. This work proposes to use a multi-period graph-theoretical (P-graph) approach to determine the optimal retrofit strategy to achieve electrification with consideration of economic and environmental factors. Both single-period and multi-period models are considered via a graph-theoretical approach to rank and evaluate all the combinatorically feasible electrification pathways based on the overall performance. The effectiveness of the proposed method is developed using a crude distillation unit (CDU) case study adopted from a multinational company. The effectiveness of the proposed method is illustrated using a crude distillation unit (CDU) case study shown in three different scenarios that include prioritizing economic aspect (Scenario 1), prioritizing environmental aspect (Scenario 2), and considering equal importance of both aspects (Scenario 3). For single-period operation, the results showed a mix of natural gas and hydropower energy, exclusive use of onshore wind energy, and a mix of onshore wind energy and biogas cogeneration energy for Scenario 1, Scenario 2, and Scenario 3, respectively. In contrast, the multi-period model also utilized nuclear energy for Scenario 2 and Scenario 3 given the seasonal availability constraint. Following that, a sensitivity analysis is conducted to see the effect of the absence of the most influential energy sources on the optimal solution of each scenario and the top solutions under budget and CO2 emission constraints. Pareto analysis is outlined to offer an understanding of tradeoffs between differently prioritized solutions that decision-makers can select. The combination of the proposed analysis provides a systemic approach towards transforming traditional industries towards a cleaner future via electrification.

Open Access: Yes

DOI: 10.1016/j.jclepro.2023.140179

Synthesis of N-best Heat Recovery Networks with Consideration of Dynamic Control Performance

Hao Yeh Lee Ákos Orosz Bing Shen How Zong Yang Kong Tiffany Ang Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2024-01-01

Volume: 114

Issue: Unknown

Page Range: 73-78

Description:

Recently, graph-theoretic methods have increasingly been employed to generate near-best (n-best) heat recovery networks, aiming to maximize energy recovery efficiency. The exploration of these n-best networks has proven pivotal for making informed decisions. Nevertheless, existing studies in this domain have not attempted to study the favourability of these generated networks based on their respective dynamic control performance. This performance metric reflects the network's ability to maintain target temperature even under disturbances. The network topologies play important role in both economic (i.e., total annual cost (TAC)) and dynamic control aspects. To address this gap, this work introduces a hybrid approach. First, all combinatorically feasible heat recovery networks are generated using P-HENS. Thereafter, each network undergoes dynamic control performance evaluation through Aspen Plus simulations. The final step involves optimization of the network structures based on fuzzy method which avoids over-prioritization. To illustrate the efficacy of the proposed methodology, it is applied to solve a 5-stream problem. Results showed that Network A with the least TAC ($122,249) is not necessarily associated with the greatest dynamic performance (with failure rate of 15 %). Network C which offers the balance performance (with TAC of $122,666 and failure rate of 0 %) is chosen.

Open Access: Yes

DOI: 10.3303/CET24114013

Retrofit heat exchanger network optimization via graph-theoretical approach: Pinch-bounded N-best solutions allows positional swapping

Ákos Orosz Bing Shen How Sin Yong Teng Ferenc Friedler Jeroen J. Jansen

Publication Name: Energy

Publication Date: 2023-11-15

Volume: 283

Issue: Unknown

Page Range: Unknown

Description:

Retrofit heat exchanger network (HEN) optimization is a fundamentally unique problem which requires the consideration of existing structures, compared to grassroots design problems. The optimization of retrofit HENs is particularly difficult due to the integration of both existing and newly acquired equipment. The re-routing of existing equipment can lead to various network topologies, increasing the complexity of considerations. In this work, we exploit the P-graph framework to solve retrofit HEN problems, guaranteeing to find the topology of optimal solutions within the constrained space of the HEN retrofit problem. The P-graph framework has additional advantages that allows topologically-efficient search space, simplifies additional unit placement, considers unit positional swapping (re-sequencing and re-piping within search constraints), considers stream splitting, and n-best solution visualization. The pinch minimum utility constraint also provides a bound for the maximum number of modifications in the HEN, significantly reducing search space. The proposed P-graph-based approach is demonstrated using a real refinery case study to show its capability in obtaining the topology of the optimal HEN, highlighting the economic and energy benefits. Further extensions to other retrofit process integration problems (e.g. retrofit water network, hydrogen network etc.) will be enabled via the proposed P-graph approach.

Open Access: Yes

DOI: 10.1016/j.energy.2023.129029

Optimization of vertical farms energy efficiency via multiperiodic graph-theoretical approach

Jean Pimentel Ferenc Friedler L. Balázs

Publication Name: Journal of Cleaner Production

Publication Date: 2023-09-01

Volume: 416

Issue: Unknown

Page Range: Unknown

Description:

A systematic method is proposed for enhancing the energy efficiency of vertical farms when integrated into urban infrastructure. The method relies on the optimization of a multiperiod model that determines the system's best operation plan considering variations in its parameters throughout the day. These parameters include factors such as resources availability from the urban infrastructure and fluctuations in electricity prices. The model is formulated and solved via the tools of the P-graph framework, which permits the automatic formulation of the rigorous superstructure and the efficient optimization of the integrated system's operation. The method is illustrated via a case study comprising three scenarios. The most efficient case demonstrates up to 40% electricity cost saving potential for a particular operation day, and up to 31% for the entire year. The method presented constitutes an optimization tool that can use real data on electricity prices and forecasts of weather conditions to reduce operating costs and enhance the energy efficiency and sustainability of vertical farming systems.

Open Access: Yes

DOI: 10.1016/j.jclepro.2023.137938

Process synthesis considering sustainability for both normal and non-normal operations: P-graph approach

Ákos Orosz Jiří Jaromír Klemeš Petar Sabev Varbanov Ferenc Friedler

Publication Name: Journal of Cleaner Production

Publication Date: 2023-08-15

Volume: 414

Issue: Unknown

Page Range: Unknown

Description:

Process synthesis usually determines the normal operation of the process. In addition to the cost, recently, sustainability has also become essential in selecting the process. In case of failures of some redundant operating units of the process, it may still be operational as a non-normal operation. This work shows that the sustainability performance of a process in non-normal operation can be much worse than that of the normal case. Consequently, during process synthesis, it is essential to consider the sustainability of a process for both normal and non-normal operations. The current work is the first in offering synthesis of a process network taking into account a pre-specified limit of the process sustainability indicator for both normal and non-normal modes. This synthesis procedure is formulated in a general way, to interface with any sustainability indicator, expressed as a scalar, here Sustainable Process Index has been used in the case studies. The presented method is illustrated on two case studies to showcase the capability of synthesizing processes for multiple operation. The obtained results indicate that it is possible to simultaneously reduce environmental impact and process cost by more than 20%, by appropriate modification of the operating modes.

Open Access: Yes

DOI: 10.1016/j.jclepro.2023.137696

Synthesis of multiperiod heat exchanger networks: n-best networks with variable approach temperature

Ákos Orosz Rozália Lakner Bing Shen How Ferenc Friedler

Publication Name: Thermal Science and Engineering Progress

Publication Date: 2023-07-01

Volume: 42

Issue: Unknown

Page Range: Unknown

Description:

In industrial processes, the stream parameters of the heat exchanger network (HEN) synthesis problem can vary during different periods. As a result of the change in inlet and outlet temperatures and the flow rates of the streams, the optimal HEN and the optimal heat transfer areas of the heat exchangers can be different in each period. In our previous work, the standard HEN synthesis for minimum utility consumption was extended to consider varying stream parameters, where bypasses at the heat exchangers are used to ensure the exit streams meet the expected outlet temperatures. This requires optimization of the total annualized cost based on the maximal heat transfer areas of the heat exchangers for each period. Minimum approach temperature is applied to ensure that the areas of the heat exchangers stay within reasonable limits in the solution network. Since minimum approach temperature affects both the structure of the HEN and the total annualized cost, its value needs to be determined during the optimization procedure. The current work proposes a procedure for HEN synthesis which determines the best, n-best, or all feasible HENs for all periods considering variable approach temperature. The proposed method extends the P-graph-based HEN synthesis method for determining all feasible networks in all periods. Three case studies are used to demonstrate the application of the proposed method. The case studies show that while the commonly applied minimum approach temperature of 10 °C does indeed gives near-optimal results, some problems need different values, such as 25 °C or 30 °C.

Open Access: Yes

DOI: 10.1016/j.tsep.2023.101912

Kriging-Assisted Multi-Objective Optimization Framework for Electric Motors Using Predetermined Driving Strategy

Péter Korös György Istenes Zoltan Pusztai Ferenc Friedler Zoltán Horváth

Publication Name: Energies

Publication Date: 2023-06-01

Volume: 16

Issue: 12

Page Range: Unknown

Description:

In this paper, a multi-objective optimization framework for electric motors and its validation is presented. This framework is suitable for the optimization of design variables of electric motors based on a predetermined driving strategy using MATLAB R2019b and Ansys Maxwell 2019 R3 software. The framework is capable of managing a wide range of objective functions due to its modular structure. The optimization can also be easily parallelized and enhanced with surrogate models to reduce the runtime. The framework is validated by manufacturing and measuring the optimized electric motor. The method’s applicability for solving electric motor design problems is demonstrated via the validation process. A test application is also presented, in which the operating points of a predetermined driving strategy provide the input for the optimization. The kriging surrogate model is used in the framework to reduce the runtime. The results of the optimization and the framework’s benefits and drawbacks are discussed through the provided examples, in addition to displaying the properly applicable design processes. The optimization framework provides a ready-to-use tool for optimizing electric motors based on the driving strategy for single- or multi-objective purposes. The applicability of the framework is demonstrated by optimizing the electric motor of a world recorder energy-efficient race vehicle. In this application, the optimization framework achieved a 2% improvement in energy consumption and a 9% increase in speed at a rated DC voltage, allowing the motor to operate at desired working points even with low battery voltage.

Open Access: Yes

DOI: 10.3390/en16124713

Enabling in-depth analysis in heat exchanger network synthesis via graph-theoretic tool: Experiences in Swinburne University of Technology Sarawak Campus

Ákos Orosz Jaka Sunarso Bing Shen How Sin Yong Teng Ferenc Friedler

Publication Name: Education for Chemical Engineers

Publication Date: 2023-04-01

Volume: 43

Issue: Unknown

Page Range: 100-112

Description:

The ability and capability to analyze and benchmark alternative designs on top of the optimal network are deemed valuable competencies for current and future chemical engineers. In this context, a process graph (P-graph)-inspired tool – P-HENS is introduced to an integrated plant design unit in an undergraduate chemical engineering degree program at Swinburne University of Technology Sarawak Campus in Malaysia. The energy recovery aspect is one of the key design elements in the integrated plant design unit. The introduction of P-HENS, which is capable of mathematically determining multiple optimal and sub-optimal solutions is considered useful for the students to (i) identify plausible heat exchanger networks (HENs) structures that may be overlooked using conventional approaches and (ii) enable a more in-depth analysis to justify the selected design. Overall, the implementation of P-HENS shows positive outcomes, where this free-of-charge software complements the learning of conventional manual approaches used in HENs synthesis. Furthermore, recommendations suggested by the users (students) are collected and compiled for potential future software development. This work serves as an essential reference for other chemical engineering educators who are teaching pinch analysis or heat integration-related courses.

Open Access: Yes

DOI: 10.1016/j.ece.2022.12.003

Implementation of Optimized Regenerative Braking in Energy Efficient Driving Strategies

Péter Korös Zoltan Pusztai Ferenc Szauter Ferenc Friedler

Publication Name: Energies

Publication Date: 2023-03-01

Volume: 16

Issue: 6

Page Range: Unknown

Description:

In this paper, determination of optimized regenerative braking-torque function and application in energy efficient driving strategies is presented. The study investigates a lightweight electric vehicle developed for the Shell Eco-Marathon. The measurement-based simulation model was implemented in the MATLAB/Simulink environment and used to establish the optimization. The optimization of braking-torque function was performed to maximize the recuperated energy. The determined braking-torque function was applied in a driving strategy optimization framework. The extended driving strategy optimization model is suitable for energy consumption minimization in a designated track. The driving strategy optimization was created for the TT Circuit Assen, where the 2022 Shell Eco-Marathon competition was hosted. The extended optimization resulted in a 2.97% improvement in energy consumption when compared to the result previously achieved, which shows the feasibility of the proposed methodology and optimization model.

Open Access: Yes

DOI: 10.3390/en16062682

Exploring N-best solution space for heat integrated hydrogen regeneration network using sequential graph-theoretic approach

Ákos Orosz Bing Shen How Adrian Chun Minh Loy Juin Yau Lim Abdulqader Bin Sahl Ferenc Friedler

Publication Name: International Journal of Hydrogen Energy

Publication Date: 2023-02-12

Volume: 48

Issue: 13

Page Range: 4943-4959

Description:

To achieve the ever-stringent sustainable goals, this paper aims to synthesize a heat integrated hydrogen regeneration network (HIHRN) using a graph-theoretic-based sequential method. Firstly, the optimal and near-optimal structures for a hydrogen regeneration networks (HRN) are determined using P-graph model with consideration of both impurity and pressure constraints. These networks are then used as inputs in P-HENS software to generate a list of optimal and near-optimal heat exchanger network (HEN) structures. An eight source and sink problem is used to demonstrate the effectiveness of the proposed method. There are 199,677 feasible HIHRN structures identified, while the 6 near-optimal solutions which are within 0.05% tolerance of the optimal network cost (i.e., less than 33.04 M$/y) are presented together with the top four HEN designs that can offer comparable costs (∼115,500 $/y). In addition, the impacts of pressure swing adsorber (PSA) pressure drop consideration and minimum temperature difference on the optimal design are also presented.

Open Access: Yes

DOI: 10.1016/j.ijhydene.2022.10.196

Energy Efficient Drive Management of Lightweight Urban Vehicle

Zoltan Pusztai Ferenc Szauter Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 103

Issue: Unknown

Page Range: 253-258

Description:

In this paper, the energy saving effect of optimized driving strategy is presented and compared to human driving strategy. The driving strategy of a one-seated experimental electric vehicle is investigated and optimized in this study, where the objective function of optimization is the minimization of the consumed energy. Measurement-based vehicle model is used during the optimization process. The initialization and constraints of optimization are set up by analyzing the acquired vehicle data of the driver. The analyzation is done using a transform algorithm, making the initialization of optimization automated. Genetic algorithm is used with mixed initial population acquired from measured driving data and from creation function. Using this hybrid initial population helped to decrease the time of optimization. The resulted velocity profile of the optimized driving strategy was used in field test measurements, where 4.28% energy savings was achieved compared to the results prior to optimization.

Open Access: Yes

DOI: 10.3303/CET23103043

Technoeconomic Assessment of Recycling Routes for Chemicals: A Case Study of n-Hexane

Gerardo Ruiz-Mercado Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 103

Issue: Unknown

Page Range: 349-354

Description:

The circular economy has become one of the most popular topics in worldwide sustainability research. The imperious necessity of reducing resource consumption and decreasing waste generation has led to reincorporating materials at the end-of-life (EoL) stage into the productive chain. Nonetheless, the presence of hazardous substances in the EoL stage materials poses a significant challenge for the transition toward the production model. The adequate transformation of these materials into feedstocks requires their correct allocation into recovery plants and final destinations. Such an allocation can be decided by resorting to optimisation by generating the best alternative networks, from where the stakeholders may decide the most suitable recycling scheme. In this work, a graph-theoretic approach is introduced to identify the best alternatives to reincorporate industrial EoL chemicals into the productive chain. This contribution presents the initial approach to this problem, demonstrated through a case study considering the data reported on the publicaccess release inventory data for n-hexane. Different recycling routes are proposed for the case study by optimising the total treatment cost, and their advantages and disadvantages are discussed; moreover, their efficiency concerning the circular economy is measured by comparing the amount of recovered chemicals. By generating plausible recycling alternatives, this work contributes positively to analysing potential alternatives for circular economy and resource conservation in industry.

Open Access: Yes

DOI: 10.3303/CET23103059

Framework to embed machine learning algorithms in P-graph: Communication from the chemical process perspectives

Ákos Orosz Bing Shen How Jean Pimentel Sin Yong Teng Ferenc Friedler Jeroen J. Jansen

Publication Name: Chemical Engineering Research and Design

Publication Date: 2022-12-01

Volume: 188

Issue: Unknown

Page Range: 265-270

Description:

P-graph is a popularly used framework for process network synthesis (PNS) and network topological optimization. This short communication introduces a Python interface for P-graph to serve as a linkage to modern programming ecosystems. This allows for a wider application of the fast and efficient P-graph solver, to provide structural and topological enumeration in numerous fields. The proposed framework allows for more integrative usage in Artificial Intelligence (AI), machine learning, process system engineering, chemical engineering and chemometrics. Large and repetitive topologies can also be automated using the new programming interface, saving time and effort in modelling. This short communication serves as a demonstration of the newly developed open-sourced P-graph interface.

Open Access: Yes

DOI: 10.1016/j.cherd.2022.09.043

Enabling technology models with nonlinearities in the synthesis of wastewater treatment networks based on the P-graph framework

Ákos Orosz Kirti M. Yenkie Jean Pimentel Emmanuel A. Aboagye Mihály Csaba Markót Heriberto Cabezas Ferenc Friedler

Publication Name: Computers and Chemical Engineering

Publication Date: 2022-11-01

Volume: 167

Issue: Unknown

Page Range: Unknown

Description:

Designing effective wastewater treatment networks is challenging because of the large number of treatment options available for performing similar tasks. Each treatment option has variability in cost and contaminant removal efficiency. Moreover, their mathematical models are highly nonlinear, thus rendering them computationally intensive. Such systems yield mixed-integer nonlinear programming models which cannot be solved properly with contemporary optimization tools that may result in local optima or may fail to converge. Herein, the P-graph framework is employed, thus generating all potentially feasible process structures, which results in simpler, smaller mathematical models. All potentially feasible process networks are evaluated by nonlinear programming resulting in guaranteed global optimum; furthermore, the ranked list of the n-best networks is also available. With the proposed tool, better facilities can be designed handling complex waste streams with minimal cost and reasonable environmental impact. The novel method is illustrated with two case studies showing its computational effectiveness.

Open Access: Yes

DOI: 10.1016/j.compchemeng.2022.108034

Synthesis of multiperiod heat exchanger networks: Minimum utility consumption in each period

Ákos Orosz Rozália Lakner Bing Shen How Ferenc Friedler

Publication Name: Computers and Chemical Engineering

Publication Date: 2022-10-01

Volume: 166

Issue: Unknown

Page Range: Unknown

Description:

Heat exchanger networks in real industrial processes often have to be designed for varying parameters of the process streams that renders multiperiod heat exchanger network synthesis essential in industrial realization. However, three standing issues must be considered in the synthesis procedure. (1) The generated network should be efficient in all periods, preferably consuming minimum utility. (2) This network should also be structurally as simple as possible for minimizing the investment cost and making the process controllable. Furthermore, (3) all or the n-best networks that fulfilled the first two principles must be considered for the selection of the most preferred industrial realization. The method proposed in the current work satisfies all three requirements simultaneously; it has been the only known method with these properties. The method primarily relies on the formerly developed P-graph-based heat exchanger network synthesis procedure. Three case studies demonstrate the application of the proposed method.

Open Access: Yes

DOI: 10.1016/j.compchemeng.2022.107949

General formulation of resilience for designing process networks

Ákos Orosz Jean Pimentel Ferenc Friedler Andres Argoti

Publication Name: Computers and Chemical Engineering

Publication Date: 2022-09-01

Volume: 165

Issue: Unknown

Page Range: Unknown

Description:

Herein, the formula proposed for quantifying the resilience of engineering systems, including processing systems, is general in several aspects. The structure of a system can be highly complex where the numbers of loops, raw materials, and products are not limited. The mathematical models of the operating units can be either linear or nonlinear for simulating the effect of the failures. The damage caused by an unexpected event can result in various levels of operation for the operating units. The proposed formula is also general in the sense that all possible combinations of failures are considered. The problem formulation, the related structure representation, the enumeration and evaluation of possible failures are based on the P-graph framework and its algorithms. The proposed formula for resilience is applicable to any complex engineering system whose behavior is primarily determined by its structure, including supply chains, information systems, municipal infrastructures, and electrical transmission networks.

Open Access: Yes

DOI: 10.1016/j.compchemeng.2022.107932

Vehicle Model-Based Driving Strategy Optimization for Lightweight Vehicle

Péter Korös Zoltan Pusztai Ferenc Szauter Ferenc Friedler

Publication Name: Energies

Publication Date: 2022-05-01

Volume: 15

Issue: 10

Page Range: Unknown

Description:

In this paper, driving strategy optimization for a track is proposed for an energy efficient battery electric vehicle dedicated to the Shell Eco-marathon. A measurement-based mathematical vehicle model was developed to simulate the behavior of the vehicle. The model contains complicated elements such as the vehicle’s cornering resistance and the efficiency field of the entire powertrain. The validation of the model was presented by using the collected telemetry data from the 2019 Shell Eco-marathon competition in London (UK). The evaluation of applicable powertrains was carried out before the driving strategy optimization. The optimal acceleration curve for each investigated power-train was defined. Using the proper powertrain is a crucial part of energy efficiency, as the drive has the most significant energy demand among all components. Two tracks with different characteristics were analyzed to show the efficiency of the proposed optimization method. The optimization results are compared to the reference method from the literature. The results of this study provide an applicable vehicle modelling methodology with efficient optimization framework, which demonstrates 5.5% improvement in energy consumption compared to the reference optimization theory.

Open Access: Yes

DOI: 10.3390/en15103631

P-graphs for process systems engineering: Mathematical models and algorithms

Ákos Orosz Jean Pimentel Losada Ferenc Friedler

Publication Name: P Graphs for Process Systems Engineering Mathematical Models and Algorithms

Publication Date: 2022-02-03

Volume: Unknown

Issue: Unknown

Page Range: 1-261

Description:

This book discusses the P-graph framework for developing and understanding effective design tools for process systems engineering, and addresses the current state of its theory and applications. The book details the new philosophy of the axioms-based mathematical modelling of processing systems, the basic algorithms, areas of application, future directions, and the proofs of theorems and algorithms. Because of the rigorous foundation of the theory, the framework provides a firm basis for future research in mathematical modelling, optimization, and design of complex engineering systems. The various P-graph applications discussed include process network synthesis, reliability engineering, and systems resilience. The framework opens new avenues for research in complex systems including redundant operations for critical infrastructure, systems sustainability, and modelling tools for disaster engineering. Demonstration software is provided to facilitate the understanding of the theory. The book will be of interest to institutions, companies, and individuals performing research and R&D in process systems engineering.

Open Access: Yes

DOI: 10.1007/978-3-030-92216-0

Regenerative Braking Optimization of Lightweight Vehicle based on Vehicle Model

Péter Korös Zoltan Pusztai Ferenc Szauter Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2022-01-01

Volume: 94

Issue: Unknown

Page Range: 601-606

Description:

The usage of regenerative braking highly improves the overall energy efficiency of electric vehicles. In this paper, the model-based optimization of the torque profile is determined in the regenerative braking process of a lightweight electric vehicle. For the optimization, measurement-based vehicle model was used, where the extended powertrain model was set up, including the regenerative operation. The whole model was elaborated in MATLAB Simulink environment, where genetic algorithm (GA) was applied for the optimization. The resulted optimized braking curve was applied to control the experimental vehicle and field test were made to validate the optimization results. The results of the presented work can be directly used to further improve the drive cycle efficiency of the urban electric vehicles. The application of optimized driving strategies, including regenerative braking, could contribute to further energy and pollution reduction in urban transportation.

Open Access: Yes

DOI: 10.3303/CET2294100

Synthesis of Integrated Vertical Farming Systems with Multiperiodic Resource Availability

Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2022-01-01

Volume: 94

Issue: Unknown

Page Range: 1039-1044

Description:

Vertical farming (VF) has been proposed as an approach to decrease the land required for growing agricultural products. This technique consists of growing produce in vertical orientation within a controlled environment. However, one of the most significant barriers for its implementation is the uncertain economic feasibility, derived from the elevated consumption of energy and the high investment costs. A strategy to enhance VF efficiency proposes its integration with municipal infrastructure, thus establishing closed-loop systems where VF seizes organic waste, manure, CO2, and excess energy from productive plants and local power stations. Because of the economic uncertainty of its development, the optimal synthesis of such a closed-loop system (i.e., the selection and specification of its components, and their connections) is of utmost importance for the implementation of this strategy. The difficulty of the synthesis task arises from the combinatorial nature of the problem and the variability of the resources and market conditions in time. This work employs a graph-theoretic approach for the synthesis of a closed-loop system of VF considering the variability of the resources during multiple periods of operation. The proposed method relies on the P-graph framework which permits the identification of the n-best alternatives for the system’s design, employing the properties of the problem’s structure to enhance the effectiveness of the solution procedure. Consequently, the most cost-effective systems are identified together with their policy of operation for the different periods. This method constitutes a powerful tool for the assessment of systems for VF integration that enhance the sustainability of agricultural activity.

Open Access: Yes

DOI: 10.3303/CET2294173

The Resilience Barriers of Automated Ground Vehicles from Military Perspectives

Árpád Tóth Rudolf Krecht Alex Suta Attila Hajdu Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2022-01-01

Volume: 94

Issue: Unknown

Page Range: 1195-1200

Description:

In the case of autonomous and semi-autonomous unmanned ground vehicles (UGVs), the military application of these systems is becoming more evident and is expected to play an increasingly important role in the future. This paper aims to present and analyse the military applicability and resilience of currently available autonomous ground vehicle perception and control systems. It is important to underline that the paper, after a comprehensive literature review and a presentation of the currently applied methods, attempts to provide a methodological classification of these complex vehicle platforms from the resilience perspective. The methodological classification is based on observations from both economic and engineering perspectives as a result of the systematic review. Furthermore, possible results of resilience are also discussed: survivability, supportability, agility and reusability of the analysed autonomous ground vehicle systems. All these factors can be significant from the point of view of sustainability. As UGVs used under challenging conditions get damaged or outdated, they tend to be dismissed without reusing expensive components, thus generating additional waste. UGVs designed with resilience in mind could be kept in service for a longer period, or their components could be reused more successfully, which supports sustainability. Based on findings there are not yet widely adopted estimation methods to measure the long-term resilience of autonomous military ground vehicles. Thus, a possible theoretical solution for system-autonomy resilience quantification was discussed relying on sensory components and perception methods extracted from the literature as input variables.

Open Access: Yes

DOI: 10.3303/CET2294199

Multiple-solution heat exchanger network synthesis using P-HENS solver

Ákos Orosz Bing Shen How Ferenc Friedler

Publication Name: Journal of the Taiwan Institute of Chemical Engineers

Publication Date: 2022-01-01

Volume: 130

Issue: Unknown

Page Range: Unknown

Description:

Analysis on the alternative designs on top of the optimal network has proven valuable and meaningful for the decision-makers in determining the most suitable options which fulfill a wide range of objective functions. On the basis of an extension of the P-graph framework, a procedure was developed previously for multiple-solution heat exchanger network (HEN) synthesis. This procedure is capable of generating the n-best HENs depending on predefined structural constraints, for example, the maximum number of heat exchangers used for the entire system, the maximum number of sequential heat exchangers on each stream, the maximum number of stream splittings per stream. Since the choice of a parameter influences the effect of other parameters on the result, it is difficult to find the proper set of parameters for the solver that result in all plausible solutions to the original problem. Naturally, this issue emerges in any HEN synthesis problem, its systematic treatment is essential. The purpose of the current work was to develop a heuristic framework for determining the most reasonable parameters of the HEN generation algorithm and guiding the designer through the optimization process. The outcome of this study not only benefits the researchers and industrial practitioners of this field but may also be extended for educational purposes.

Open Access: Yes

DOI: 10.1016/j.jtice.2021.05.006

Reducing resource use and emissions by integrating technology and policy solutions

Raymond R. Tan Yee Van Fan Petar Sabev Varbanov Ferenc Friedler

Publication Name: Clean Technologies and Environmental Policy

Publication Date: 2022-01-01

Volume: 24

Issue: 1

Page Range: Unknown

Description:

No description provided

Open Access: Yes

DOI: 10.1007/s10098-021-02237-2

Reliability incorporated optimal process pathway selection for sustainable microalgae-based biorefinery system: P-graph approach

Ákos Orosz Bing Shen How Juin Yau Lim Ferenc Friedler Chang Kyoo Yoo

Publication Name: Computer Aided Chemical Engineering

Publication Date: 2022-01-01

Volume: 49

Issue: Unknown

Page Range: 217-222

Description:

Biofuel from microalgae is one of the promising solutions on addressing climate change by its possibility of reducing the fossil fuel dependency. Till-date, the overall competitiveness of microalgae based biorefinery is the major concern due to its unique operational mechanism, especially the biological growth of microalgae that fluctuates towards the surrounding. Therefore, a novel graph-theoretic approach has been proposed to provide an optimization approach for identifying optimal process design with the consideration of three aspects that includes: economic, environmental, and reliability. The optimization is conducted using P-graph (a powerful graph-theoretic tool) which is capable to determine optimal and near-optimal solutions based on three objective functions: (i) minimizing annual operating cost, (ii) minimizing potential environmental impact, and (iii) maximizing reliability of process. The pool of feasible solutions (optimal and near-optimal) is obtained by satisfying the constraints on both greenhouse gas emissions and its respective reliability along. Thereupon, a further analysis was carried out with the aid of TOPSIS considering three of the assessment aspects to identify the optimal microalgae biorefinery configuration

Open Access: Yes

DOI: 10.1016/B978-0-323-85159-6.50036-1

Synthesis and Techno-Economic Analysis of Pyrolysis-Oil-Based Biorefineries Using P-Graph

Botond Bertok Abid H. Tanzil Anamaria Paiva Pinheiro Pires Lina Martinez-Valencia István Heckl Juan C. García-Ojeda Ferenc Friedler Manuel Garcia-Perez Andres Argoti

Publication Name: Energy and Fuels

Publication Date: 2021-08-19

Volume: 35

Issue: 16

Page Range: 13159-13169

Description:

The production of renewable fuels and chemicals is a critical component of global strategies to reduce greenhouse gas emissions. In this regard, pyrolysis oil obtained from biomass comprises hundreds of chemical compounds, thus rendering it a good precursor for manufacturing a variety of fuel products of commercial interest. Despite the large number of contributions describing the products' extraction, upgrading, and potential refining schemes, no bio-oil refinery is currently in operation. The main challenge in building a bio-oil refinery lies in the lack of an economically viable process configuration. Systematic studies comparing alternative refinery concepts, or configurations, are needed to identify the most promising configuration. To the best of our knowledge, this study is the first to use process graph (P-graph) methodology for the synthesis of pyrolysis oil refineries. In particular, this work shows the effectiveness of P-graph methodology in simultaneously calculating the profitability of various biorefinery designs by using data reported in the literature and providing information on how the introduction of new technologies to the database will impact the formation of profitable biorefinery concepts. Our work demonstrates a methodology for the addition of new unit operations to the database generated from the literature. The addition of a centrifuge for water extraction and a wet oxidation system for acetic acid production resulted in the generation of 330 biorefinery configurations, seven of which have a profitability ranging from $1,650 to $23,666/h (USD) with acetic acid and levoglucosan as the main products, respectively. This demonstrates that P-graph methodology is useful for discovering optimum techno-economic scenarios that may otherwise be overlooked.

Open Access: Yes

DOI: 10.1021/acs.energyfuels.1c01299

The P-graph approach for systematic synthesis of wastewater treatment networks

Ákos Orosz Kirti M. Yenkie Jean Pimentel Heriberto Cabezas Ferenc Friedler

Publication Name: Aiche Journal

Publication Date: 2021-07-01

Volume: 67

Issue: 7

Page Range: Unknown

Description:

Wastewater treatment consists of three or four sequential stages: preliminary, primary, secondary, and tertiary. Each stage can comprise multiple alternative technologies that can perform the same tasks with different efficiencies, operating times, and costs. Thus, we propose a systematic approach for designing wastewater treatment networks by utilizing principles of mathematical modeling and generating an exhaustive enumeration of all the possible technologies and their connections during the early stages of designing a treatment facility. Some of these structures are nonintuitive and include recycling, reprocessing, bypasses, and multiple technologies in parallel or series to remove the same contaminant. The nonintuitive structures with multiple technologies may provide a measure of resilience compared to typical heuristic designs. Thus, the combination of P-graph methodology and the sequence of treatment technologies predicted via the optimization algorithm from the maximal structure is based on holistic considerations and does not lead to suboptimal solutions.

Open Access: Yes

DOI: 10.1002/aic.17253

Conceptual design of a negative emissions polygeneration plant for multiperiod operations using P-graph

Kathleen B. Aviso Ákos Orosz Raymond R. Tan Jean Pimentel Ferenc Friedler

Publication Name: Processes

Publication Date: 2021-02-01

Volume: 9

Issue: 2

Page Range: 1-19

Description:

Reduction of CO2 emissions from industrial facilities is of utmost importance for sustainable development. Novel process systems with the capability to remove CO2 will be useful for carbon management in the future. It is well-known that major determinants of performance in process systems are established during the design stage. Thus, it is important to employ a systematic tool for process synthesis. This work approaches the design of polygeneration plants with negative emission technologies (NETs) by means of the graph-theoretic approach known as the P-graph framework. As a case study, a polygeneration plant is synthesized for multiperiod operations. Optimal and alternative near-optimal designs in terms of profit are identified, and the influence of network structure on CO2 emissions is assessed for five scenarios. The integration of NETs is considered during synthesis to further reduce carbon footprint. For the scenario without constraint on CO2 emissions, 200 structures with profit differences up to 1.5% compared to the optimal design were generated. The best structures and some alternative designs are evaluated and compared for each case. Alternative solutions prove to have additional practical features that can make them more desirable than the nominal optimum, thus demonstrating the benefits of the analysis of near-optimal solutions in process design.

Open Access: Yes

DOI: 10.3390/pr9020233

Vehicle Model for Driving Strategy Optimization of Energy Efficient Lightweight Vehicle

Péter Korös Zoltan Pusztai Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 385-390

Description:

The energy consumption and CO2 emission of urban vehicles are highly dependent on their operation. Vehicle models can be used for optimizing driving strategy for emission reduction. This paper proposes a novel vehicle model of a one-seat electric vehicle dedicated for Shell Eco-marathon (SEM), the most famous and largest race of energy efficient vehicles. The available vehicle dynamical formulas cannot be directly used to describe the characteristics of lightweight vehicles. In the current work, a novel grey-box vehicle model has been introduced, based on measurement scenarios. The whole model has been elaborated in MATLAB Simulink environment, where individual subassemblies were defined for driving resistance model, powertrain model, and the racetrack characteristics. The resistance force model manages the forces in straight line moving and also takes the effect of cornering into account. Based on test bench measurements the complete efficiency map of the drivetrain was created and implemented into the vehicle model. The presented vehicle model is suitable for driving strategy optimization. By optimizing this model, 7.1 % energy savings have been achieved compared to best human driven lap. Driving strategy optimization will be essential, especially for autonomous vehicles, expressing the importance of the presented results in the future.

Open Access: Yes

DOI: 10.3303/CET2188064

Processing systems design considering resilience

Ákos Orosz Jean Pimentel Ferenc Friedler

Publication Name: Computer Aided Chemical Engineering

Publication Date: 2021-01-01

Volume: 50

Issue: Unknown

Page Range: 807-812

Description:

The resilience of a system is defined as the system's capability of recovering from failures. Traditionally, only predictable aspects are considered when designing processing systems. Evaluation of these aspects is performed via assessment of exact indicators and enumeration of all cause-effect options. However, such evaluation is not appropriate for determining the resilience of processing systems, since resilience is based on unexpected events in addition to the expected ones. Consequently, the cause part of the cause-effect relation is not known or not effective. In the current work, the general formula for determining resilience of a system is embedded into a P-graph based process synthesis algorithm. Thus, the resilience can be considered when selecting the most preferred process during its synthesis. The result is illustrated by synthesizing a process of adipic acid production by nitric acid oxidation of KA oil.

Open Access: Yes

DOI: 10.1016/B978-0-323-88506-5.50126-1

Systematic Design and Evaluation of Energy-Efficient Alternatives of Heterogeneous Azeotropic Distillation: Furfural Case Study

Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 619-624

Description:

Separation of azeotropic mixtures receives special attention for their impact on various significant industrial processes. Because of the non-ideal behaviour of these mixtures, it is impossible to separate them by conventional distillation. Instead of a single distillation unit, a system of multiple operations is to be employed. Heterogeneous azeotropic distillation (HAD) is an example of this kind of systems, where entrainers are applied to modify the behaviour of the mixture. The selection of the best separation system is a key objective during the synthesis of the process network. However, synthesis of HAD is especially difficult because of the complex interaction between its continuous and discrete features. Therefore, traditional separation network synthesis tools are incapable of solving this problem. In this work, the properties of the ternary vapor-liquid-liquid equilibrium diagram are exploited for systematically identifying plausible operating units that perform the separation of the azeotrope. Subsequently, energy consumption of the entire network is estimated through rigorous simulation. The P-graph framework is employed to represent the system’s structure. Additionally, its combinatorial algorithms generate a rigorous superstructure for the synthesis problem, and the set of n-best designs that minimize energy consumption. The method is illustrated by synthesizing the dehydration of furfural through HAD. The results demonstrate that it constitutes a valuable tool for the designer by being effective in the systematic identification and assessment of HAD alternatives.

Open Access: Yes

DOI: 10.3303/CET2188103

Retrofit Synthesis of Industrial Heat Exchanger Networks with Different Types of Heat Exchangers

Olga Arsenyeva Ákos Orosz Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 613-618

Description:

Heat Exchanger Network (HEN) synthesis is a powerful tool for the development of more efficient processes with high utilization of mass and energy resources. The implementation of compact heat exchangers with enhanced heat transfer into the industrial flowsheets can provide more efficient and economically feasible solutions. Plate Heat Exchanger (PHE) is one of established types of enhanced HEs. To estimate possible benefits of that kind of heat transfer enhancement, a mathematical model of PHE, which accounts for different plate types and corresponding corrugations geometry, is used. The integration of this model with the P-graph-based HEN synthesis approach allowed to create the method, which considers different types of heat exchangers. This approach enables to integrate not only conventional shell-and-tube heat exchangers, but also PHEs, which overall heat transfer coefficient is in average 2-3 times higher, during the optimization process of a new or existing HEN. The capabilities of the proposed method are presented via a case study for oil preheat train, where an existing network is retrofitted; first with shell-and-tube heat exchangers only, then with the consideration of both shell-and-tube and plate heat exchangers.

Open Access: Yes

DOI: 10.3303/CET2188102

Heat Integrated Water Regeneration Network Synthesis via Graph-Theoretic Sequential Method

Ákos Orosz Bing Shen How Sin Yong Teng Juin Yau Lim Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 49-54

Description:

The integration of multiple resources conservation networks is necessary to attain the ever-stringent sustainable goals. This work takes initiatives to develop a heat integrated water network via a proposed P-graph-based sequential methodology. In the first step, a set of feasible water regeneration networks is generated using the conventional P-graph framework. Then, the obtained feasible networks will be used as the inputs in the second stage which aims to generate various sets of feasible heat exchanger networks. It is worth noting that the second model is solved by an extended P-graph framework (P-HENS) for combinatorial process network optimization. The solutions are then ranked based on the total network cost. To demonstrate the effectiveness of the proposed method, a typical water regeneration network (three sources and three sinks) with multi-contaminants is used. The results show a total of 103 feasible water network structures (water network cost ranging from 0.76 M$/y to 1.18 M$/y). Thereafter, a list of feasible HIWRN can be determined using P-HENS. The top four HIWRNs which offer similar total network cost (~1.639 M$/y) are demonstrated. This proposed method provides valuable insights that allow decision-makers to further select the optimal solution which may be more beneficial as compared to the one obtained via conventional methods.

Open Access: Yes

DOI: 10.3303/CET2188008

Energy Integration of Vertical Farms for Higher Efficiency and Sustainability

Jean Pimentel Ferenc Pongrácz György Ágoston Zoltán Sejpes Zsolt Bukodi István Kenyeres Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 727-732

Description:

As a result of the increasing human population, the availability of resources per capita has been vastly diminished in the last decades. Naturally, the depletion of valuable environmental assets such as water and arable land, poses a threat to mankind’s sustainable development. In this regard, various novel ideas have been proposed for processing agricultural products ecologically and sustainably; one of such ideas is vertical farming (VF). VF is a novel production technology that aims at enhancing both the yield and the product quality, by growing them in highly packed, high energy-density systems with high mass-flow rates and in a controlled environment. The technologies required for VF have been developed and successfully tested, thereby producing crops that meet the requirements of food safety, adequate nutrient content, and maximum yield. However, the extremely high biomass densities and high turnover rates employed to give rise to challenges regarding to energy efficiency and homogeneity patterns. In this work, a P-graph model is presented for the integration of VF systems. The algorithmic approach is employed to evaluate options for process integration and intensification of VF with plausible synergetic production processes into a dense urban environment. As a result, 115 integrated process alternatives are identified for the base case, with the best structure exhibiting a total cost of 41,920 EUR/y, thereby yielding reductions up to 11% for the total cost of the integrated network. The pareto front of economic performance and CO2 emission is presented to illustrate the potential benefits of integration, and the capability of the methodology to evaluate alternative designs.

Open Access: Yes

DOI: 10.3303/CET2188121

Efficient Design and Sustainability Assessment of Wastewater Treatment Networks using the P-graph Approach: A Tannery Waste Case Study

Ákos Orosz Kirti M. Yenkie Jean Pimentel Emmanuel A. Aboagye Heriberto Cabezas Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 493-498

Description:

In the tannery industry approximately, 30 - 35 m3 of wastewater (WW) is generated per ton of rawhide processed. The WW comprises high concentrations of salts, ammonia, dye, solvents, and chromium. Of particular interest is chromium, which has been proven to cause dermatological, developmental, and reproductive issues on exposure. Thus, there is a need for appropriate treatment of the tannery WW before it is discharged for natural remediation. However, designing a treatment process is multifaceted due to the availability of multiple technologies that can perform similar tasks and the complex composition of waste streams. This necessitates the treatment to be performed in stages namely, primary, secondary, and tertiary. In some cases, pretreatment is required to enhance the recovery in the following stages. Due to the combinatorial nature of this problem, the P-graph approach, which uses principles from graph theory, can be used to synthesize a treatment pathway by selecting appropriate technologies at each stage, while meeting required purity specifications. Furthermore, the P-graph approach can provide alternate feasible treatment structures ranked based on Economics as well as Sustainability indicators, such as the Sustainable Process Index (SPI). In this work, a tannery WW case study is investigated with multiple stages and treatment technologies. A complex maximal structure is generated comprising all possible technologies, flows, connections, bypasses, mixers, and splitters. The models for each technology involve capital and operating costs, efficiency, and SPI at each stage of the treatment process. This problem is formulated in P-graph and solved using the Accelerated Branch-and-Bound algorithm.

Open Access: Yes

DOI: 10.3303/CET2188082

Multiple-solution heat exchanger network synthesis for enabling the best industrial implementation

Ákos Orosz Ferenc Friedler

Publication Name: Energy

Publication Date: 2020-10-01

Volume: 208

Issue: Unknown

Page Range: Unknown

Description:

The synthesis of heat recovery networks traditionally results in an optimal or suboptimal solution for the supplied set of streams and simplifying assumptions. In the current work, the assumption of a single optimal solution is replaced by the goal of generating an ordered set of optimal or quasi-optimal networks. This enables industrial engineers to further select the solution most suitable for detailed design and practical implementation. The problem is formulated for and solved by an extension of the P-graph framework for combinatorial process network optimization. The presented method for HEN synthesis generates a list of solutions ranked by the Total Annualized Cost. In addition to the feasibility, all list elements also feature a degree of heat recovery ranging from the thermodynamic maximum, down to a specified margin allowing accounting for the energy-capital trade-off. The current method is illustrated with three case studies. The obtained results demonstrate optimal solutions that cannot be generated by the Pinch-based methods or the stage-wise superstructure approaches. The proposed parameters, an upper limit on the number of heat exchangers per process stream and a maximum relaxation of utility demand compared to the Pinch targets, allow performing parametric evaluations of the resulting solutions.

Open Access: Yes

DOI: 10.1016/j.energy.2020.118330

Socio-ecological network structures from process graphs

Angelyn Lao Ákos Orosz Raymond R. Tan Heriberto Cabezas Ferenc Friedler

Publication Name: Plos One

Publication Date: 2020-08-01

Volume: 15

Issue: 8 August

Page Range: Unknown

Description:

We propose a process graph (P-graph) approach to develop ecosystem networks from knowledge of the properties of the component species. Originally developed as a process engineering tool for designing industrial plants, the P-graph framework has key advantages over conventional ecological network analysis techniques based on input-output models. A P-graph is a bipartite graph consisting of two types of nodes, which we propose to represent components of an ecosystem. Compartments within ecosystems (e.g., organism species) are represented by one class of nodes, while the roles or functions that they play relative to other compartments are represented by a second class of nodes. This bipartite graph representation enables a powerful, unambiguous representation of relationships among ecosystem compartments, which can come in tangible (e.g., mass flow in predation) or intangible form (e.g., symbiosis). For example, within a P-graph, the distinct roles of bees as pollinators for some plants and as prey for some animals can be explicitly represented, which would not otherwise be possible using conventional ecological network analysis. After a discussion of the mapping of ecosystems into P-graph, we also discuss how this framework can be used to guide understanding of complex networks that exist in nature. Two component algorithms of P-graph, namely maximal structure generation (MSG) and solution structure generation (SSG), are shown to be particularly useful for ecological network analysis. These algorithms enable candidate ecosystem networks to be deduced based on current scientific knowledge on the individual ecosystem components. This method can be used to determine the (a) effects of loss of specific ecosystem compartments due to extinction, (b) potential efficacy of ecosystem reconstruction efforts, and (c) maximum sustainable exploitation of human ecosystem services by humans. We illustrate the use of P-graph for the analysis of ecosystem compartment loss using a small-scale stylized case study, and further propose a new criticality index that can be easily derived from SSG results.

Open Access: Yes

DOI: 10.1371/journal.pone.0232384

General formulation for the resilience of processing systems

Ákos Orosz Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2020-01-01

Volume: 81

Issue: Unknown

Page Range: 859-864

Description:

Resilience is one of the key indicators of processing systems, it expresses the behaviour of the system as a result of expected or unexpected failures. This indicator can be essential during systems design and operation, especially, when the system is part of or related to a critical infrastructure. The numerous contributions on systems resilience are related to a wide range of applications, however, there is no general uniform framework for resilience evaluation. For instance, most studies examine resilience as a function of the continuous parameters of the system, usually avoiding the influence of its structure. In the current work, a general framework for determining the structural resilience of processing systems is presented. This framework derives on formulas that satisfy the requirements of the original definition of resilience. The formerly developed P-graph framework is the mathematical basis of the procedure for determining the indicator. The resilience of the system is calculated as a function of the operative subprocesses for all possible failures and is a normalized indicator on [0, 1]. The examination of two industrial case studies shows that the proposed resilience can be an appropriate indicator to be considered in process design.

Open Access: Yes

DOI: 10.3303/CET2081144

Automated synthesis of process-networks by the integration of P-graph with process simulation

Ákos Orosz Raymond R. Tan Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2020-01-01

Volume: 81

Issue: Unknown

Page Range: 1171-1176

Description:

Chemical process simulation has become one of the most important tools for the analysis of process networks. The simulation software currently available are not capable of automatically generating the process structure, the designer must provide it as an input for the simulation. This limits the contribution of simulation to the latter stages of design after the structure has been clearly defined. Since the P-graph methodology was originally conceived to generate process structures systematically, it can be used to produce the topology of the problem automatically based on rigorous combinatorial axioms and algorithms. In this work, the properties of two P-graph algorithms are exploited to automatically generate alternative structures in a commercial simulator, conferring the latter an improved capacity to assist during the early stage of design. Initially, the maximal structure generation (MSG) algorithm is employed to identify a rigorous superstructure from the initial set of plausible operating units. The solution structure generation (SSG) algorithm is then used to enumerate all combinatorially feasible processes included in the superstructure. Each process structure is individually exported to Aspen Plus®, where rigorous models are used to simulate its performance. A set of alternative processes ranked by their economic performance can be generated. This integrated methodology is employed in a case study for producing methyl lactate from methanol and lactic acid. This work demonstrates that integration of P-graph with rigorous simulation constitutes an enhanced tool for process synthesis that automates the generation of process alternatives, providing useful information and additional insight of the synthesis problem.

Open Access: Yes

DOI: 10.3303/CET2081196

Multi-period natural gas pipeline scheduling optimisation integrated with LNG cold energy cascade utilisation

Bohong Wang Hengcong Tao Wen Zhao Long Peng Yunzhong Bei Petar Sabev Varbanov Ferenc Friedler

Publication Name: Sustainable Energy Technologies and Assessments

Publication Date: 2025-11-01

Volume: 83

Issue: Unknown

Page Range: Unknown

Description:

Liquefied Natural Gas (LNG), as a vital form of natural gas resources, has exhibited a steadily increasing trend in global production and trade volumes. LNG terminals are facing the challenge of how to recover and utilise cold energy in a safe and efficient regasification process, while coordinating with the natural gas pipeline network transport scheduling. This study proposes an integrated regulation and collaborative optimisation approach for natural gas pipeline networks and LNG cold energy cascade utilisation systems. For natural gas pipeline network systems, P-Graph develops multi-period gas-electric interconnected supply chain network to optimise resource allocation. For the LNG cold energy cascade utilisation system, a dual Organic Rankine Cycle (ORC) framework for both power generation and refrigeration is developed, as well as thermodynamic analysis and heat integration techniques are applied to optimise system efficiency. Using a coastal LNG terminal in Zhejiang, China, as a case study, when the LNG regasification flow rate is 62.46 t/h, cold energy generates electricity of 2,335.94 kW and air-conditioning cooling load of 1,651.5 kW, system efficiency reaches 44.75 %. The peak regulation and gas storage effect of LNG is significant, which helps to alleviate that energy shortage in the region, and the coupled system of LNG and natural gas pipeline network improves energy utilisation efficiency and economic benefits for LNG industry chain.

Open Access: Yes

DOI: 10.1016/j.seta.2025.104577

Pathway Optimization for Low-Carbon Plastic Waste-to-Hydrogen Production with Flexible Feed Composition Using a Regression Model

Viknesh Andiappan Bing Shen How Selena Kian Yii Song Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2025-01-01

Volume: 120

Issue: Unknown

Page Range: 169-174

Description:

Conversion of plastic waste into hydrogen is a potential solution to address the issues of growing demand for hydrogen and the massive accumulation of plastic waste simultaneously. However, most studies on plastic-to-hydrogen technology selection were based on predetermined plastic waste composition, limiting their applicability to dynamic real-life operations. To address this, this work introduces a flexible optimisation model capable of accommodating varying compositions of plastic waste. With the aid of regression models, the optimisation model can optimise the plastic-to-hydrogen production pathways, considering economic and environmental performances, without the constraints of specific plastic waste types or mixture compositions. Regression models are developed based on the ultimate analysis data (carbon, hydrogen, nitrogen, oxygen, and sulphur content) to estimate hydrogen yield and purity across various pathways. Thereafter, fuzzy optimisation is employed to identify the trade-off between cost and environmental impact. In addition to the selection of optimal plastic waste-to-hydrogen pathways, the model also considers different purification technologies that can improve the hydrogen purity to various extents. The model demonstrated that pyrolysis-steam reforming combined with PSA is capable of achieving hydrogen purity of 99.999 % with a highest overall satisfaction of 0.7141 (equivalent to total cost of 3.43 M$ and emissions of 528,647 kg CO2/y) while pyrolysis-catalytic decomposition is more suitable to produce hydrogen with lower purity (55 %).

Open Access: Yes

DOI: 10.3303/CET25120029

Enhanced Heat Recovery Network with Integrated Sensible Heat Storage Facilities for Energy Intensive Industry

Ákos Orosz Viknesh Andiappan Bing Shen How Tiffany Ang Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2025-01-01

Volume: 120

Issue: Unknown

Page Range: 19-24

Description:

Energy-intensive industries contribute large amounts of greenhouse gas emissions. An effective strategy to decarbonise these industries is by applying process integration tools to enhance energy efficiency and reduce overall energy consumption. Recent studies showed that thermal energy storage offers significant benefits in energy efficiency enhancement, as it can amplify the energy recovery potential. Despite its potential, studies that applied process integration tools to address heat recovery problems with consideration of heat storage remain limited. This work develops an optimisation framework that aims to determine optimal heat storage type and size based on the total annualised cost (i.e., costs associated with storage facilities and utilities) to form a feasible heat recovery network between plants. The proposed framework is demonstrated through a case study that focuses on optimising the sensible heat storage selection for indirect heat integration between a mixed plastic waste treatment plant and a steel mill. By analysing the performance and effectiveness of the storage media studied, nitrate salt storage medium is selected due to its greatest energy and cost savings of 12.7 % and 20.7 %, when compared to direct Heat Integration. Insights from this provide information on the feasibility of implementing a storage-supported heat recovery network in the energy-intensive industry.

Open Access: Yes

DOI: 10.3303/CET25120004

N-best Design Options with Strategical Differences in Process Network Synthesis

Ákos Orosz Sin Yong Teng Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2025-01-01

Volume: 120

Issue: Unknown

Page Range: 409-414

Description:

The main goal of Process Network Synthesis is usually to find the lowest-cost process for a given problem. Since the model is not able to account for every parameter of an industrial realisation, the decision makers prefer to have alternatives, which can be provided when generating the n-best solutions. This, however, comes with another issue, specifically that several of the near-optimal solutions are almost identical to the optimal one, and only differ in one or two operating units. Thus, the next step to improve the generation of feasible and performant alternatives is to provide process designs with meaningful differences from the optimum. Meaningful differences between designs have to be defined by the decision makers. These are differences that the decision makers consider as major strategic questions, while other changes in the process constitute fine details where simply selecting the lowest cost option is enough. The current work describes a branch-and-bound algorithm that is able to generate the n-best strategically different process designs. The difference between considering and ignoring strategic differences when generating n-best solutions is illustrated via a case study.

Open Access: Yes

DOI: 10.3303/CET25120069

Enabling Energy-Efficient and Sustainable Green Glycerol-Derived 1,3-Propanediol Production via a Graph-Theoretical-Based Approach

Ákos Orosz Bing Shen How Adrian Chun Minh Loy Lip Siang Yeo Tiffany Ang Selena Kian Yii Song Ferenc Friedler

Publication Name: ACS Sustainable Chemistry and Engineering

Publication Date: 2025-07-28

Volume: 13

Issue: 29

Page Range: 11178-11189

Description:

The rise in biodiesel production results in an excess of crude glycerol, which further leads to environmental concerns. Consequently, transforming crude glycerol into valuable products is deemed an effective way to address this issue. Process Integration techniques are introduced to enhance the overall economic viability by maximizing the energy recovery in the biodiesel plant. However, most of the existing studies merely focused on a single optimal heat exchanger network (HEN) generated. In this study, P-HENS software is utilized to generate viable HENs for a glycerol-derived 1,3-propanediol plant. Subsequently, piping costs of each HEN are estimated to determine the optimal HEN by assuming the respective heat exchanger is placed at the centroid. Finally, the optimal HEN is identified based on the total annualized costs (TAC) (which include the capital cost of the heat exchanger, utility cost, and piping costs) and energy-related carbon emissions of the network. The results show that, among the 4,188 feasible networks generated, network #623 possesses the best overall performance when both cost and environmental aspects are considered. The carbon emissions of network #623 is 16.7% lower than that of the case without heat recovery. This work demonstrates the usefulness of the generated near-best HENs in enabling a more comprehensive HEN optimization. By application of the proposed methodology, the most economical and environmentally friendly HEN can be determined. This contributes to both cost savings and sustainability in HEN design.

Open Access: Yes

DOI: 10.1021/acssuschemeng.5c00606

LTV-LQG Control for an Energy Efficient Electric Vehicle

Tamás Luspay Zoltan Pusztai Ferenc Friedler

Publication Name: Vehicles

Publication Date: 2025-12-01

Volume: 7

Issue: 4

Page Range: Unknown

Description:

This paper presents the design and evaluation of a Linear Time-Varying Linear Quadratic Gaussian (LTV-LQG) controller for an energy efficient electric vehicle, using a predetermined driving strategy as the reference trajectory. The proposed approach begins with the development of a structured nonlinear vehicle model based on relevant subsystems, enabling accurate energy consumption estimation with a deviation of less than 2% from experimental measurements. This model serves as the basis for computing a near-optimal driving trajectory. The nonlinear model is linearized along the predefined trajectory to support control design. A time-varying control structure is then developed, integrating a Kalman filter that estimates unmeasured external disturbances, such as wind, and enhances feedback performance. The proposed control strategy is evaluated through simulations and compared to a rule-based switching controller that replicates human-like driving behavior. The simulation results demonstrate that the LTV-LQG controller consistently satisfies the time constraints in both headwind- and tailwind-dominant scenarios, where the switching controller tends to exceed the time limit. Moreover, in tailwind-dominant cases, the LTV-LQG controller achieves lower energy consumption (up to 15.4%). The proposed framework represents a computationally efficient and practically feasible control solution for electric vehicles operating under realistic disturbance conditions.

Open Access: Yes

DOI: 10.3390/vehicles7040113

Systematic generation of flexible heat exchanger networks with minimum utility consumption

Ákos Orosz Bing Shen How Jean Pimentel Petar Sabev Varbanov Ferenc Friedler

Publication Name: Thermal Science and Engineering Progress

Publication Date: 2026-02-01

Volume: 70

Issue: Unknown

Page Range: Unknown

Description:

Heat exchanger network (HEN) synthesis is a topic of high importance, encompassing several solution approaches and problem aspects. One such aspect crucial to industrial applications is flexibility, since real systems often experience variations of certain parameters, e.g., inlet temperatures or flowrates. Decades of research have revealed numerous methods for analyzing the flexibility of a given heat exchanger network. Meanwhile, the synthesis of flexible HENs continued to prove to be a severely difficult task, especially since handling the parameter deviations should not compromise the high level of heat integration. This work introduces a novel direction for synthesizing flexible HENs by combining flexibility analysis methods with P-graph-based, exhaustive, combinatorial network generation. The method generates all feasible networks that satisfy both the structural criteria and the maximum energy recovery over the entire variation region, and presents them ordered by capital cost. This first iteration of the work focuses on variations in inlet stream temperatures. This allows proving the validity of the underlying concepts by generating HENs that achieve minimum utility consumption for the entire range of temperature variations. The capability to generate multiple suitable networks is demonstrated through a case study, where 429 feasible networks were generated, which are all capable of achieving maximum heat integration within the parameter variation region. For the best generated design options, a 4–6% increase in capital cost compared to the base case is sufficient to satisfy the flexibility requirements.

Open Access: Yes

DOI: 10.1016/j.tsep.2026.104490

How to design a dynamically-feasible heat exchanger network? Insights gained from experience

Hao Yeh Lee Ákos Orosz Bing Shen How Zong Yang Kong Tiffany Ang Ferenc Friedler

Publication Name: Energy

Publication Date: 2026-02-01

Volume: 344

Issue: Unknown

Page Range: Unknown

Description:

This paper aims to share the challenges encountered by the authors while exploring the significance of controllability in the early stage of heat exchanger network (HEN) design, particularly through the use of P-HENS – a graph theoretic-based HEN synthesis tool for multi-solution HEN synthesis. Presently, no existing studies have leveraged P-HENS-derived networks to reveal insight on how network topology affects its dynamic performance. This work began with a 5-stream problem as a base case, where P-HENS was used to generate four feasible HENs that meets the minimum energy requirement (MER). A preliminary screening narrowed these options to two configurations, which were then simulated in Aspen Plus. Bypass are added to the two selected HENs for further control studies in Aspen Plus Dynamics. The results indicated that both HENs could handle only some disturbances and return the outlet temperature to its nominal value, with some cases showing marginal deviations. Then, different bypass values (e.g., 0.1 and 0.5) were explored to analyze its impact on control performance but it reveals that even with a larger bypass value of 0.5, the HEN struggled to adequately adjust during disturbances. The findings from this work showed that the controllability of the HEN is collectively influenced by the bypass value, the temperature difference of the “direct inlet and outlet of the heat exchanger”, and the temperature difference of the “inlet streams of both hot and cold streams placed in the heat exchanger”. A generic workflow that would help future researchers avoid similar pitfalls has been presented.

Open Access: Yes

DOI: 10.1016/j.energy.2026.139903

Uncovering the energy infrastructure in Europe: Data-driven digital twin for policy analysis and interpretation via multi-way analysis

Ákos Orosz Jean Pimentel Sin Yong Teng Ferenc Friedler Jeroen J. Jansen

Publication Name: Energy

Publication Date: 2026-02-01

Volume: 344

Issue: Unknown

Page Range: Unknown

Description:

With the adoption of the European Green Deal, the target to reduce net greenhouse gas emissions by 55 % by 2030, compared to 1990 levels, requires a higher renewable energy fraction and better energy efficiency. This requires a comprehensive re-evaluation of the power infrastructure within the European Union (EU). To achieve this, a EU-focused digital twin has been constructed, focusing on the European region and neighboring countries. The twin uses annual and 30-min resolution data from 113 main stations representing 40 countries, with a focus on EU member states. Multi-way analysis (PARAFAC2) is used to align interpretation for both data and high-resolution data, prioritizing regional energy infrastructure features. An automated graph-theory (P-graph) approach is used to construct a large-scale multi-time-sliced energy-balanced model as a digital twin model. This novel integration of macro-level trend analysis (via PARAFAC2), time-resolved optimization, and equity-based constraints enables a data-driven exploration of diverse policy scenarios. This study shows that effective EU energy policy should balance renewable diversification, equity in energy access, and regional cooperation, as policy shifts significantly affect energy flows and trade dynamics. While resilient infrastructure may require high investment, trade-off analysis reveals cost-effective, balanced pathways that optimize both sustainability and security objectives. The work demonstrates the potential for data-driven policy making for regional or international infrastructure, focusing on optimization of energy transfer activities, promotion of renewable sources, and systematic planning.

Open Access: Yes

DOI: 10.1016/j.energy.2026.140001

Navigating Cost-Efficient Circular Integration of Plastic Waste-to-X Pathways into Oil Refinery Using the Graph-Theoretic Approach

Ákos Orosz Viknesh Andiappan Bing Shen How Jui Yuan Lee Yat Choy Wong Sin Yong Teng Adeline Shu Ting Tan Ferenc Friedler

Publication Name: Industrial and Engineering Chemistry Research

Publication Date: 2026-04-01

Volume: 65

Issue: 12

Page Range: 6587-6604

Description:

Plastic waste conversion has been widely recognized as a promising strategy to address growing waste management challenges. However, the feasibility of its integration into existing industrial systems remains uncertain. This paper explores a plastic waste-to-X strategy aimed at reintegrating plastic waste into its original supply chain, in alignment with circular economy principles. A graph-theoretic optimization model is developed using P-graph to identify the optimal and near-optimal pathway configurations under multiple scenarios. Under a cost minimization scenario, the optimal solution achieves a 0.013–0.19% lower cost compared with alternative pathways; however, related to the higher opportunity cost of up to 24,364 USD/y from forgone utility savings and carbon tax reductions. Incorporating carbon credits shifts the focus toward balancing cost efficiency and emission reduction. Under budget constraints, the benefit-cost analysis reveals that emission reduction does not increase linearly with budget expansion. These findings guide decision-makers in setting realistic emission reduction targets and allocating budget efficiently, while helping policymakers to develop a financial scheme that promotes greater emission reductions without excessive expenditure.

Open Access: Yes

DOI: 10.1021/acs.iecr.5c04350

Enabling industry symbiosis between energy-intensive industries via optimal integration of thermal energy storage

Ákos Orosz Viknesh Andiappan Bing Shen How Sin Yong Teng Tiffany Ang Ferenc Friedler

Publication Name: Thermal Science and Engineering Progress

Publication Date: 2026-06-01

Volume: 74

Issue: Unknown

Page Range: Unknown

Description:

Energy-based industrial symbiosis is a potential decarbonisation strategy for energy-intensive industries, which contribute significantly to carbon emissions. Thermal energy storage (TES) can be integrated to enhance energy efficiency and operational flexibility, while addressing issues related to supply–demand fluctuations. Nonetheless, the economic feasibility of TES-supported interplant heat recovery depends on the costs and properties of the storage media incorporated. Therefore, this work presents a systematic framework for optimising TES selection across a spectrum of storage options for interplant indirect heat integration. The objective is to minimise the total annualised cost (TAC), comprising energy and storage capital costs. The optimal TES option can then be identified based on its respective TAC ranking. A case study that compares the effectiveness of the indirect method against the intraplant and direct methods is conducted. The results show that among the 33 TES options evaluated, silica fire brick offers the lowest TAC and energy-related carbon emissions, leading to a reduction of 21.60% and 13.16%, respectively, as compared to the intraplant method. Subsequently, a sensitivity analysis is performed to explore the impacts of varying stream flowrates and storage capacity redundancy allocation on the TES selection. This provides insights into the performance of various TES options under intraplant, direct, and indirect heat integration methods. Finally, the threshold (i.e., stream flowrate required to provide economic gain under a given redundant allocation scenario) aligned with the strategic planning can be determined. This work demonstrates that TES integration can improve the economic feasibility and sustainability of industrial symbiosis in energy-intensive industries.

Open Access: Yes

DOI: 10.1016/j.tsep.2026.104707