| 1. |
- Petropoulos, Fotios, et al.
(författare)
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Operational Research : methods and applications
- 2024
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Ingår i: Journal of the Operational Research Society. - : Taylor & Francis Group. - 0160-5682 .- 1476-9360. ; 75:3, s. 423-617
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Forskningsöversikt (refereegranskat)abstract
- Throughout its history, Operational Research has evolved to include methods, models and algorithms that have been applied to a wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first summarises the up-to-date knowledge and provides an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion and used as a point of reference by a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes.
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| 2. |
- Dong, Beibei, et al.
(författare)
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AI-based Dynamic Modelling for CO2 Capture
- 2023
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Ingår i: Energy Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Integrating CO2 capture with biomass/waste fired combined heat and power plants (CHPs) is a promising method to achieve negative emission. However, the use of versatile biomass/waste and dynamic operation of CHPs result in big fluctuations in the flue gas (FG) and heat input to CO2 capture. Dynamic modelling is essential to investigate the interactions between key process parameters in producing the dynamic response of the CO2 capture process. In order to facilitate developing robust control strategies for flexible operation in CO2 capture plants and optimizing the operation of CO2 capture plants, artificial intelligence (AI) models are superior to mechanical models due to the easy implementation into the control and optimization. This paper aims to develop an AI model, Informer, to predict the dynamic responses of MEA based CO2 capture performance from waste-fired CHP plants. Dynamic modelling was first developed in Aspen HYSYS software and validated against the reference. The operation data from the simulated CO2 capture process was then used to develop and verify Informer. The following variables were employed as inputs: inlet flue gas flow rate, CO2 concentration in inlet flue gas, lean solvent flow rate, heat input to CO2 capture. It was found that Informer could predict CO2 capture rate and energy consumption with the mean absolute percentage error of 6.2% and 2.7% respectively.
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| 3. |
- Dong, Beibei
(författare)
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Dynamic modeling of MEA-based CO2 capture in biomass-fired CHP plants
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Global warming is a significant threat to our planet. Adopting the Paris Agreement is a global action that aims to reduce greenhouse gas emissions. An extensive deployment of negative emission technologies (NETs) is required to achieve the targets set by the Paris Agreement. Bioenergy with carbon capture and storage (BECCS) is emerging as one of the most promising NETs. Among different biomass utilization processes, integrating BECCS with biomass-fired and waste-fired combined heat and power (bio-CHP and w-CHP) plants has been considered the most feasible solution. Bio/w-CHP plants are characterized by high fluctuations in operation, which can result in more dynamic variations of flue gas (FG) flowrates and compositions and available heat for CO2 capture. Such changes can clearly affect the performance of CO2 capture; therefore, doing dynamic simulations becomes crucial.This thesis aims to investigate the performance of different dynamic physical model-based approaches and provide suggestions for approach selection. In addition, the data-driven modeling approach, which is an emerging technology, has also been tested.Three physical model-based approaches include the ideal static model (IST), the dynamic approach without control (Dw/oC), and the dynamic approach with control (DwC). To compare their performance, the operating data from an actual waste CHP plant is employed. Various cases have been defined considering different critical operating parameters, including the FG flowrate, the CO2 concentration (CO2vol%), and the available heat for CO2 capture. Apparent differences can be observed in the results from different approaches. For example, when the CO2vol% drops from 15.7 % to 9.7 % (about 38 %) within 4 hours, the difference in the captured CO2 can be up to 22% between DwC and Dw/oC. It is worth noting that when there are both increases and decreases in the variations of parameters, the differences become smaller. Based on the comparison, the recommendations on approaches have been summarized. Dw/oC is recommended for checking the boundary of safety operation by the response analysis. DwC is recommended for designing the control system, observing the flexible dynamic operation, estimating the short-term CO2 capture potential, and optimizing the hourly dynamic operation. IST is recommended for estimating the long-term CO2 capture potential, and optimizing the long-term dynamic operation when the input parameters vary not as often as hourly.A data-driven model, Informer, is developed to model CO2 capture dynamically. The dataset is generated by using a physical model. The FG flowrate, the CO2vol%, the lean solvent flowrate, and the available heat for CO2 capture are employed as input parameters, and the CO2 capture rate and the energy penalty are chosen as outputs. The results show that Informer can accurately predict dynamic CO2 capture. The mean absolute percentage error (MAPE) was found to be 6.2% and 2.7% for predicting the CO2 capture rate and energy penalty, respectively.
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| 4. |
- Dong, Beibei, et al.
(författare)
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Negative emission potential from biomass/waste combined heat and power plants integrated with CO2 capture : An approach from the national perspective
- 2024
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Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 467
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Tidskriftsartikel (refereegranskat)abstract
- Integrating carbon dioxide (CO2) capture in biomass or waste-fired combined heat and power (CHP) plants has been considered a key measure to achieve negative emissions. To support decision-making, an accurate assessment of the potential contribution and the associated cost from the national perspective is urgently needed. This paper proposed a bottom-up approach based on a dynamic modelling to evaluate the potental of nationwide negative emissions. As heat supply is often prioritized by CHP plants, unchanged heat generation is a prerequisite of this study. Two operating modes (OMs) for the integration of CO2 capture are investigated, which can represent the upper and lower boundaries of CO2 capture: OM1 aims to maximize the amount of captured CO2, while electricity generation can be sacrificed; OM2 aims to maximize the amount of captured CO2, while the electricity generation is maintained unchanged. Sweden is employed as a case study. Results show that operating CO2 capture in OM1 can achieve 8.7 million ton CO2 nationwide negative emissions a year, while operating CO2 capture in OM2 can generate 4.3 million ton CO2 positive emissions a year, which represents a reduction of 6.3 million tonCO2 a year compared with the reference plant without CO2 capture. The levelized costs of CO2 avoided are 36.9 USD/tonCO2 and 52.0 USD/tonCO2 for OM1 and OM2, respectively. The biogenic fraction of waste has a significant influence on negative emissions. According to the Swedish climate goal about bioenergy with CO2 capture and storage (BECCS), to achieve 3 million ton negative CO2 emissions a year, the minimum biogenic fractions should be 32.8% and 84.3% for operating CO2 capture in OM1 and OM2, respectively; in contrast, to achieve 10 million ton negative emissions a year, biomass and waste-fired CHP plants have to operate CO2 capture in OM1 and the biogenic fraction needs to be over 59.9%.
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| 5. |
- Dong, Beibei, et al.
(författare)
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PVTxy Properties of CO2 Mixtures for CCS : An Update of Experimental Data and Models Since 2009
- 2018
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Ingår i: JOINT INTERNATIONAL CONFERENCE ON ENERGY, ECOLOGY AND ENVIRONMENT ICEEE 2018 AND ELECTRIC AND INTELLIGENT VEHICLES ICEIV 2018. - : DESTECH PUBLICATIONS, INC. - 9781605955902
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Konferensbidrag (refereegranskat)abstract
- The latest progress on the experimental data and theoretical models regarding PVTxy properties of CO2 mixtures has been updated. This review shows that more experimental data are available, such as the vapor liquid equilibrium (VLE) of CO2/NO and the density of CO2/O-2. But there are still some clear deficiencies: for example, there have been no data on VLE of CO2/COS and density of CO2/NH3; there are only few points on VLE of CO2/NH3 and CO2/N2O, and density of binary mixtures containing CO, N2O4, COS and H2S. Several new models exhibit advantages for calculating PVTxy properties of CO2 mixtures. For example, Equation of State for Combustion Gases and Combustion Gas-like Mixtures (EOS-CG) shows better accuracy on both phase equilibrium and density than GERG-2008 except for the critical region. Peng-Robinson+ residual Helmholtz energy-based model (PR + EOS/(E,Wilson)(ares)) displays significant improvement in the representation of high-pressure critical region (deviation decreasing from 12.6% to 1% for CO2/O-2/N-2) and wider application of polar and non-polar mixtures for VLE.
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| 6. |
- Dong, Beibei, et al.
(författare)
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Selecting the approach for dynamic modelling of CO2 capture in biomass/waste fired CHP plants
- 2023
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier Ltd. - 1750-5836 .- 1878-0148. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- Integrating CO2 capture with biomass/waste fired combined heat and power (CHP) plants is a promising method to achieve negative emissions. However, the use of versatile biomass/waste and the dynamic operation of CHP plants result in bigger fluctuations in the properties of flue gas (FG), e.g. CO2 concentration (CO2vol%) and flowrates, and the heat that can be used for CO2 capture, when comparing with coal fired power plants. To address such a challenge, dynamic modelling is essential to accurately estimate the amount of captured CO2 and optimize the operation of CO2 capture. This paper compares three dynamic approaches commonly used in literature, namely using the ideal static model (IST) and using dynamic models without control (Dw/oC) and with control (DwC), for MEA based chemical absorption CO2 capture. The performance of approaches is assessed under the variations of key factors, including the flowrate and CO2vol% of FG, and the available heat for CO2 capture. Simulation results show clear differences. For example, when the CO2vol% drops from 15.7 % to 9.7 % (about 38 %) within 4 hours, DwC gives the highest amount of captured CO2, which is 7.3 % and 22.3 % higher than IST and Dw/oC, respectively. It is also found that the time step size has a clear impact on the CO2 capture amount, especially for DwC. Based on the results, suggestions are also provided regarding the selection of dynamic modelling approaches for different purposes of simulations.
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| 7. |
- Dong, Shuaili, et al.
(författare)
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Volatility of electricity price in Denmark and Sweden
- 2019
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Ingår i: INNOVATIVE SOLUTIONS FOR ENERGY TRANSITIONS. - : ELSEVIER SCIENCE BV. ; , s. 4331-4337
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Konferensbidrag (refereegranskat)abstract
- Under the pressure of global environmental climate change, all countries in the world are developing renewable energy such as hydropower, wind energy, and solar energy As a result, the electricity price varies in different patterns depending on the penetration of renewable energy. In this paper, a non-parametric model is employed to analyze the historical data of electricity spot price from Danish price areas of the Nord Pool (with high percentage of wind power), Swedish price areas of the Nord Pool (with high percentage of hydropower) and PJM market (with little renewable energy penetrated). The objective is to deeply understand the influence of renewable energies on electricity price volatility. It is found that electricity prices are more stable in Swedish price areas as hydropower is a more stable energy source. The electricity price in PJM market is also comparatively stable, only more volatile than Swedish market, as fossil fuels are dominant energy resources. For Danish price areas, the volatility of electricity prices is clearly affected by wind power, which is a highly intermittent energy resource.
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| 8. |
- Dong, X., et al.
(författare)
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A novel design of a metal hydride reactor integrated with phase change material for H2 storage
- 2024
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 367
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Tidskriftsartikel (refereegranskat)abstract
- Using metal hydride for hydrogen storage in stationary applications and for transportation is a promising technology due to its advantages of large hydrogen storage capacity, low pressure and low energy consumption. Combining the metal hydride reactor with PCM is expected to recover the heat generated during the hydrogen absorption and use it for hydrogen desorption, thus improving the energy efficiency of the system. This paper proposes a metal hydride reactor integrated with honeycomb fins and PCM to enhance heat transfer. Based on simulations, the results show that the achieved hydrogen storage capacity is 1.326 wt%, the gravimetric and volumetric storage densities are 0.411% and 14.76 kg of H2 per m3, respectively, and the mean saturated rates are 1.222 × 10−3 g s−1 and 0.773 × 10−3 g s−1 for absorption and desorption processes. Compared with the reactor without fins, the mass and volume of the reactor using honeycomb fins are increased, resulting in a decrease in gravimetric and volumetric storage density, but a increase in reaction rate during hydrogen absorption and desorption processes. Based on this structure, we also propose a honeycomb fin reactor filled with sandwich PCM to further accelerate the heat transfer in the reaction process. Compare to the reactor with PCM only filled on the periphery of the honeycomb fins, the hydrogen absorption and desorption times are shortened by about 86.4% and 81.1%, respectively. In addition, different reactor structures are compared using multiple KPIs to provide relevant suggestions for the reactor optimization. The obtained research results can provide a reference for effective thermal management methods in MH storage systems.
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| 9. |
- Hu, C., et al.
(författare)
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Different control strategies for MEA based chemical absorption
- 2021
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Ingår i: Energy Proceedings. - : Scanditale AB.
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Konferensbidrag (refereegranskat)abstract
- When capturing CO2 from biomass fired combined heat and power plants, the dynamic changes in the feedstock and the heat and electricity demands can clearly affect the operation of the boiler, which can further affect the performance of chemical absorption CO2 capture. To handle such dynamic changes, control systems are needed. This work aims to compare the performance of two control strategies that can control the reboiler duty in the stripper to achieve a constant capture rate. Control strategy A uses the reboiler temperature as input based on a PID controller; and control strategy B is a modification of control strategy A by introducing a feedforward compensation based on the flowrate of rich solution when regulating the reboiler duty. Based on dynamic simulations, it is found that control strategy B can reduce the settling time and capture more CO2 with a lower average energy penalty within a certain time length.
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| 10. |
- Hu, C., et al.
(författare)
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Dynamic simulation of CO2 capture from biomass power plant by MEA
- 2020
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Ingår i: Energy Proceedings. - : Scanditale AB.
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Konferensbidrag (refereegranskat)abstract
- The bioenergy with CO2 capture and storage (BECCS) is a promising solution to cut CO2 emissions and will play an important role in achieving the climate goal of 1.5°C. As the properties of biomass varies significantly, it is of importance to understand the dynamic performance when capturing CO2 from biomass fired power plants. This work is to reveal the dynamic performance of chemical absorption. The aqueous solution of monoethanolamine (MEA) was selected as the solution. By using the real flue gas (FG) data, the influence of FG flow rate on CO2 capture were studied by doing dynamic simulations. It has been found that as the FG flow rate decreases, the CO2 capture rate first rose before going down; and the reboiler duty decreased while the energy consumption of CO2 capture increased.
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