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Thermodynamic Optimization of Complex Energy Systems

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A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Thermodynamics".

Deadline for manuscript submissions: closed (31 October 2020) | Viewed by 37018

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Special Issue Editor

Prof. Dr. Jose M. Martinez-Val

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Department of Energy and Fluid Mechanics Engineering, Madrid Polytechnical University, C/José Gutiérrez Abascal No. 2, 28006 Madrid, Spain
Interests: thermodynamics; heat transfer; energy; solar energy; fusion energy

Special Issue Information

Dear Colleagues,

Please, let me ask you to pay attention to one of the most recurrent words in Engineering and Economics, “Optimization”. In such a competitive world as ours, everything seems to be optimized, but this is not true. There is plenty of room to improve our systems, particularly in the domain of Energy. This is why you are cordially invited to contribute to the Special Issue presented here, with the subject “Thermodynamic Optimization of Complex Energy Systems”.

Topics that could be included in this Special Issue are too many for us to be able to name them all. They can run from classical subjects to the new requirements of sustainable development. Thermal energy storage is a very powerful mechanism for storing energy, but it conveys the design of a thermodynamic cycle with high efficiency both for feeding the storage and to discharge it. Supercritical cycles, particularly with CO2, are a promise that must reach a mature level soon, and it will help other topics, notably concentrating solar power, which will have to be treated in the Special Issue with the interest it deserves. Extremely low temperatures also require many optimization approaches. Type II superconductors, such as MgB2, have stirred a lot of attention for the transport of huge electrical currents, but those cables need to be inside an envelope keeping its internals at the temperature of liquid hydrogen. This is not an easy task. Cryogenics is a mandatory word in this context, and thermodynamics must be the integrating factor for all these challenges.

Please, consider this Special Issue as an opportunity to review facts and theories, and to approach a brighter future. Your papers and proposals will be checked, studied, and treated with warm enthusiasm.

The deadline for paper submission is extended until the end of September 2020, because of the abnormal living and working conditions produced by the pandemic COVID-19. Nevertheless, authors are encouraged to send contributions as soon as possible, to speed up the editing process.

Papers of relevance and high quality will be sponsored by Madrid (Spain) based Foundation F2i2, who will pay for their page fees. Originality in how to deal with the concept of Optimization will be highly appreciated.

I look forward to hearing from you soon, and I remain at your disposal should you have any questions about this Special Issue.

Prof. Dr. Jose M. Martinez-Val
Guest Editor

Manuscript Submission Information

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

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

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Optimization tools
Physical properties and uncertainties
Optimization evaluation
Supercritical cycles
New concepts in thermodynamic cycles
Thermal synergism
Thermal coherence
Concentrating solar power
Cryogenics

Published Papers (10 papers)

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Research

27 pages, 408 KiB

Open AccessArticle

Optimization of an Industrial Sector Regulated by an International Treaty. The Case for Transportation of Perishable Foodstuff

by Juan P. Martínez-Val and Alberto Ramos

Entropy 2021, 23(1), 109; https://doi.org/10.3390/e23010109 - 15 Jan 2021

Cited by 2 | Viewed by 1791

Abstract

Transportation of perishable foodstuff is an engineering and commercial activity ruled by an international Agreement (the ATP) that needs an updated regulation. Before addressing such updating, some analyses are required about the physics of the problem, in order to identify the optimum use of the available technologies and the advantages represented by new methodologies that could be enabled soon. It is worth pointing out that manufacturers of ATP equipment follow quite closely the prescriptions given by this Agreement. So, optimizing those prescriptions will generate a general optimization trend in this sector. In this paper, a coherent analysis on these subjects is presented, and a new coefficient is proposed for qualifying ATP units, and some new tests are also proposed for measuring that coefficient in an efficient and inexpensive way. These goals are justified in this paper as a contribution from basic physics to a particular domain of Thermal Engineering. The paper is intended to be a bridge from Science to Technology, which is a must to get optimum results in exploiting technical knowledge. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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25 pages, 4843 KiB

Open AccessArticle

Minimization of Entropy Generation Rate in Hydrogen Iodide Decomposition Reactor Heated by High-Temperature Helium

by Rui Kong, Lingen Chen, Shaojun Xia, Penglei Li and Yanlin Ge

Entropy 2021, 23(1), 82; https://doi.org/10.3390/e23010082 - 08 Jan 2021

Cited by 19 | Viewed by 2270

Abstract

The thermochemical sulfur-iodine cycle is a potential method for hydrogen production, and the hydrogen iodide (HI) decomposition is the key step to determine the efficiency of hydrogen production in the cycle. To further reduce the irreversibility of various transmission processes in the HI decomposition reaction, a one-dimensional plug flow model of HI decomposition tubular reactor is established, and performance optimization with entropy generate rate minimization (EGRM) in the decomposition reaction system as an optimization goal based on finite-time thermodynamics is carried out. The reference reactor is heated counter-currently by high-temperature helium gas, the optimal reactor and the modified reactor are designed based on the reference reactor design parameters. With the EGRM as the optimization goal, the optimal control method is used to solve the optimal configuration of the reactor under the condition that both the reactant inlet state and hydrogen production rate are fixed, and the optimal value of total EGR in the reactor is reduced by 13.3% compared with the reference value. The reference reactor is improved on the basis of the total EGR in the optimal reactor, two modified reactors with increased length are designed under the condition of changing the helium inlet state. The total EGR of the two modified reactors are the same as that of the optimal reactor, which are realized by decreasing the helium inlet temperature and helium inlet flow rate, respectively. The results show that the EGR of heat transfer accounts for a large proportion, and the decrease of total EGR is mainly caused by reducing heat transfer irreversibility. The local total EGR of the optimal reactor distribution is more uniform, which approximately confirms the principle of equipartition of entropy production. The EGR distributions of the modified reactors are similar to that of the reference reactor, but the reactor length increases significantly, bringing a relatively large pressure drop. The research results have certain guiding significance to the optimum design of HI decomposition reactors. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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24 pages, 2966 KiB

Open AccessArticle

Techno-Economic Optimization of CSP Plants with Free-Falling Particle Receivers

by Luis F. González-Portillo, Kevin Albrecht and Clifford K. Ho

Entropy 2021, 23(1), 76; https://doi.org/10.3390/e23010076 - 06 Jan 2021

Cited by 36 | Viewed by 3577

Abstract

Particle receivers are one of the candidates for the next generation of CSP plants, whose goal is to reduce the levelized cost of electricity (LCOE) to 0.05 $/kWh. This paper presents a techno-economic analysis to study if a CSP system with free-falling particle receiver can achieve this goal. The plant analyzed integrates two ground-based bins to store the excess energy and a supercritical CO₂ cycle to generate electricity. The model used for the analysis presents several upgrades to previous particle systems models in order to increase its fidelity, accuracy, and representativeness of an actual system. The main upgrades are the addition of off-design conditions during the annual simulations in all the components and an improved receiver model validated against CFD simulations. The size of the main components is optimized to obtain the system configuration with minimum LCOE. The results show that particle CSP systems can reduce the LCOE to 0.056 $/kWh if the configuration is composed of 1.61 × 10⁶ m² of heliostats, a 250 m high tower with a 537 m² falling particle curtain, and 16 h thermal energy storage. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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18 pages, 2807 KiB

Open AccessArticle

Dichotomic Decision Optimization for the Design of HVDC Superconducting Links

by Javier Muñoz-Antón, Adela Marian, Frédéric Lesur and Christian-Eric Bruzek

Entropy 2020, 22(12), 1413; https://doi.org/10.3390/e22121413 - 15 Dec 2020

Cited by 2 | Viewed by 2179

Abstract

Superconducting links are an innovative solution for bulk power transmission, distinguished by their compact dimensions, high efficiency and small environmental footprint. As with any new technology field, there is a large amount of design possibilities for such links, each of them having a profound impact on the system configuration. For instance, changing the material can imply a change in the working temperature from 20 to 70 K and has consequences on the maximum link length. This article presents the dichotomic decision possibilities for the optimized design of a high-power superconducting link, focusing on some of the key components of the cable system. The complex design optimization process is exemplified using the European project Best Paths, in which the first 3-gigawatt-class superconducting cable system was designed, optimized, manufactured, and successfully tested. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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17 pages, 1649 KiB

Open AccessArticle

Comparative Analysis of Energy and Exergy Performance of Hydrogen Production Methods

by Angel Martínez-Rodríguez and Alberto Abánades

Entropy 2020, 22(11), 1286; https://doi.org/10.3390/e22111286 - 12 Nov 2020

Cited by 27 | Viewed by 6155

Abstract

The study of the viability of hydrogen production as a sustainable energy source is a current challenge, to satisfy the great world energy demand. There are several techniques to produce hydrogen, either mature or under development. The election of the hydrogen production method will have a high impact on practical sustainability of the hydrogen economy. An important profile for the viability of a process is the calculation of energy and exergy efficiencies, as well as their overall integration into the circular economy. To carry out theoretical energy and exergy analyses we have estimated proposed hydrogen production using different software (DWSIM and MATLAB) and reference conditions. The analysis consolidates methane reforming or auto-thermal reforming as the viable technologies at the present state of the art, with reasonable energy and exergy efficiencies, but pending on the impact of environmental constraints as CO₂ emission countermeasures. However, natural gas or electrolysis show very promising results, and should be advanced in their technological and maturity scaling. Electrolysis shows a very good exergy efficiency due to the fact that electricity itself is a high exergy source. Pyrolysis exergy loses are mostly in the form of solid carbon material, which has a very high integration potential into the hydrogen economy. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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15 pages, 2448 KiB

Open AccessArticle

Beta Type Stirling Engine. Schmidt and Finite Physical Dimensions Thermodynamics Methods Faced to Experiments

by Cătălina Dobre, Lavinia Grosu, Monica Costea and Mihaela Constantin

Entropy 2020, 22(11), 1278; https://doi.org/10.3390/e22111278 - 11 Nov 2020

Cited by 14 | Viewed by 6240

Abstract

The paper presents experimental tests and theoretical studies of a Stirling engine cycle applied to a β-type machine. The finite physical dimension thermodynamics (FPDT) method and 0D modeling by the imperfectly regenerated Schmidt model are used to develop analytical models for the Stirling engine cycle. The purpose of this study is to show that two simple models that take into account only the irreversibility due to temperature difference in the heat exchangers and imperfect regeneration are able to indicate engine behavior. The share of energy loss for each is determined using these two models as well as the experimental results of a particular engine. The energies exchanged by the working gas are expressed according to the practical parameters, which are necessary for the engineer during the entire project, namely the maximum pressure, the maximum volume, the compression ratio, the temperature of the heat sources, etc. The numerical model allows for evaluation of the energy processes according to the angle of the crankshaft (kinematic–thermodynamic coupling). The theoretical results are compared with the experimental research. The effect of the engine rotation speed on the power and efficiency of the actual operating machine is highlighted. The two methods show a similar variation in performance, although heat loss due to imperfect regeneration is evaluated differently. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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18 pages, 1092 KiB

Open AccessArticle

Optimum Expanded Fraction for an Industrial, Collins-Based Nitrogen Liquefaction Cycle

by Carlos Arnaiz-del-Pozo, Ignacio López-Paniagua, Alberto López-Grande and Celina González-Fernández

Entropy 2020, 22(9), 959; https://doi.org/10.3390/e22090959 - 30 Aug 2020

Cited by 4 | Viewed by 2124

Abstract

Industrial nitrogen liquefaction cycles are based on the Collins topology but integrate variations. Several pressure levels with liquefaction to medium pressure and compressor–expander sets are common. The cycle must be designed aiming to minimise specific power consumption rather than to maximise liquid yield. For these reasons, conclusions of general studies cannot be extrapolated directly. This article calculates the optimal share of total compressed flow to be expanded in an industrial Collins-based cycle for nitrogen liquefaction. Simulations in Unisim Design R451 using Peng Robinson EOS for nitrogen resulted in

88 %

expanded flow, which is greater than the 75–80% for conventional Collins cycles with helium or other substances. Optimum specific compression work resulted

430.7

kWh/ton of liquid nitrogen. For some operating conditions, the relation between liquid yield and specific power consumption was counterintuitive: larger yield entailed larger consumption. Exergy analysis showed

40.3 %

exergy efficiency of the optimised process. The exergy destruction distribution and exergy flow across the cycle is provided. Approximately 40% of the

59.7 %

exergy destruction takes place in the cooling after compression. This exergy could be used for secondary applications such as industrial heating, energy storage or for lower temperature applications as heat conditioning. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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17 pages, 5758 KiB

Open AccessEditor’s ChoiceArticle

Optimization of a New Design of Molten Salt-to-CO₂ Heat Exchanger Using Exergy Destruction Minimization

by María José Montes, José Ignacio Linares, Rubén Barbero and Beatriz Yolanda Moratilla

Entropy 2020, 22(8), 883; https://doi.org/10.3390/e22080883 - 12 Aug 2020

Cited by 7 | Viewed by 3984

Abstract

One of the ways to make cost-competitive electricity, from concentrated solar thermal energy, is increasing the thermoelectric conversion efficiency. To achieve this objective, the most promising scheme is a molten salt central receiver, coupled to a supercritical carbon dioxide cycle. A key element to be developed in this scheme is the molten salt-to-CO₂ heat exchanger. This paper presents a heat exchanger design that avoids the molten salt plugging and the mechanical stress due to the high pressure of the CO₂, while improving the heat transfer of the supercritical phase, due to its compactness with a high heat transfer area. This design is based on a honeycomb-like configuration, in which a thermal unit consists of a circular channel for the molten salt surrounded by six smaller trapezoidal ducts for the CO₂. Further, an optimization based on the exergy destruction minimization has been accomplished, obtained the best working conditions of this heat exchanger: a temperature approach of 50 °C between both streams and a CO₂ pressure drop of 2.7 bar. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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13 pages, 310 KiB

Open AccessArticle

Step by Step Derivation of the Optimum Multistage Compression Ratio and an Application Case

by Ignacio López-Paniagua, Javier Rodríguez-Martín, Susana Sánchez-Orgaz and Juan José Roncal-Casano

Entropy 2020, 22(6), 678; https://doi.org/10.3390/e22060678 - 18 Jun 2020

Cited by 11 | Viewed by 4733

Abstract

The optimum pressure ratio for the stages of a multistage compression process is calculated with a well known formula that assigns an equal ratio for all stages, based on the hypotheses that all isentropic efficiencies are also equal. Although the derivation of this formula for two stages is relatively easy to find, it is more difficult to find for any number of stages, and the examples that are found in the literature employ complex mathematical methods. The case when the stages have different isentropic efficiencies is only treated numerically. Here, a step by step derivation of the general formula and of the formula for different stage efficiencies are carried out using Lagrange multipliers. A main objective has been to maintain the engineering considerations explicitly, so that the hypotheses and reasoning are clear throughout, and will enable the readers to generalise or adapt the methodology to specific problems. As the actual design of multistage compression processes frequently meet engineering restrictions, a practical example has been developed where the previous formulae have been applied to the design of a multistage compression plant with reciprocating compressors. Special attention has been put into engineering considerations. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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20 pages, 3436 KiB

Open AccessArticle

Analysis of an Integrated Solar Combined Cycle with Recuperative Gas Turbine and Double Recuperative and Double Expansion Propane Cycle

by Antonio Rovira, Rubén Abbas, Marta Muñoz and Andrés Sebastián

Entropy 2020, 22(4), 476; https://doi.org/10.3390/e22040476 - 21 Apr 2020

Cited by 6 | Viewed by 3027

Abstract

The main objective of this paper is to present and analyze an innovative configuration of integrated solar combined cycle (ISCC). As novelties, the plant includes a recuperative gas turbine and the conventional bottoming Rankine cycle is replaced by a recently developed double recuperative double expansion (DRDE) cycle. The configuration results in a fuel saving in the combustion chamber at the expense of a decreased exhaust gas temperature, which is just adequate to feed the DRDE cycle that uses propane as the working fluid. The solar contribution comes from a solar field of parabolic trough collectors, with oil as the heat transfer fluid. The optimum integration point for the solar contribution is addressed. The performance of the proposed ISCC-R-DRDE design conditions and off-design operation was assessed (daily and yearly) at two different locations. All results were compared to those obtained under the same conditions by a conventional ISCC, as well as similar configurations without solar integration. The proposed configuration obtains a lower heat rate on a yearly basis in the studied locations and lower levelized cost of energy (LCOE) than that of the ISCC, which indicates that such a configuration could become a promising technology. Full article

(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)

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