Energies

Review

29 pages, 864 KiB

Open AccessEditor’s ChoiceReview

Review of Physicochemical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers

by Janvier Sylvestre N’cho, Issouf Fofana, Yazid Hadjadj and Abderrahmane Beroual

Energies 2016, 9(5), 367; https://doi.org/10.3390/en9050367 - 13 May 2016

Cited by 202 | Viewed by 12741

A power transformer outage has a dramatic financial consequence not only for electric power systems utilities but also for interconnected customers. The service reliability of this important asset largely depends upon the condition of the oil-paper insulation. Therefore, by keeping the qualities of [...] Read more.

A power transformer outage has a dramatic financial consequence not only for electric power systems utilities but also for interconnected customers. The service reliability of this important asset largely depends upon the condition of the oil-paper insulation. Therefore, by keeping the qualities of oil-paper insulation system in pristine condition, the maintenance planners can reduce the decline rate of internal faults. Accurate diagnostic methods for analyzing the condition of transformers are therefore essential. Currently, there are various electrical and physicochemical diagnostic techniques available for insulation condition monitoring of power transformers. This paper is aimed at the description, analysis and interpretation of modern physicochemical diagnostics techniques for assessing insulation condition in aged transformers. Since fields and laboratory experiences have shown that transformer oil contains about 70% of diagnostic information, the physicochemical analyses of oil samples can therefore be extremely useful in monitoring the condition of power transformers. Full article

(This article belongs to the Special Issue Power Transformer Diagnostics, Monitoring and Design Features)

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25 pages, 10377 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Diagnostic Measurements for Power Transformers

by Stefan Tenbohlen, Sebastian Coenen, Mohammad Djamali, Andreas Müller, Mohammad Hamed Samimi and Martin Siegel

Energies 2016, 9(5), 347; https://doi.org/10.3390/en9050347 - 6 May 2016

Cited by 166 | Viewed by 14350

Abstract

With the increasing age of the primary equipment of the electrical grids there exists also an increasing need to know its internal condition. For this purpose, off- and online diagnostic methods and systems for power transformers have been developed in recent years. Online [...] Read more.

With the increasing age of the primary equipment of the electrical grids there exists also an increasing need to know its internal condition. For this purpose, off- and online diagnostic methods and systems for power transformers have been developed in recent years. Online monitoring is used continuously during operation and offers possibilities to record the relevant stresses which can affect the lifetime. The evaluation of these data offers the possibility of detecting oncoming faults early. In comparison to this, offline methods require disconnecting the transformer from the electrical grid and are used during planned inspections or when the transformer is already failure suspicious. This contribution presents the status and current trends of different diagnostic techniques of power transformers. It provides significant tutorial elements, backed up by case studies, results and some analysis. The broadness and improvements of the presented diagnostic techniques show that the power transformer is not anymore a black box that does not allow a view into its internal condition. Reliable and accurate condition assessment is possible leading to more efficient maintenance strategies. Full article

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28 pages, 2317 KiB

Open AccessEditor’s ChoiceReview

Inorganic p-Type Semiconductors: Their Applications and Progress in Dye-Sensitized Solar Cells and Perovskite Solar Cells

by Ming-Hsien Li, Jun-Ho Yum, Soo-Jin Moon and Peter Chen

Energies 2016, 9(5), 331; https://doi.org/10.3390/en9050331 - 30 Apr 2016

Cited by 85 | Viewed by 18783

Abstract

Considering the increasing global demand for energy and the harmful ecological impact of conventional energy sources, it is obvious that development of clean and renewable energy is a necessity. Since the Sun is our only external energy source, harnessing its energy, which is [...] Read more.

Considering the increasing global demand for energy and the harmful ecological impact of conventional energy sources, it is obvious that development of clean and renewable energy is a necessity. Since the Sun is our only external energy source, harnessing its energy, which is clean, non-hazardous and infinite, satisfies the main objectives of all alternative energy strategies. With attractive features, i.e., good performance, low-cost potential, simple processibility, a wide range of applications from portable power generation to power-windows, photoelectrochemical solar cells like dye-sensitized solar cells (DSCs) represent one of the promising methods for future large-scale power production directly from sunlight. While the sensitization of n-type semiconductors (n-SC) has been intensively studied, the use of p-type semiconductor (p-SC), e.g., the sensitization of wide bandgap p-SC and hole transport materials with p-SC have also been attracting great attention. Recently, it has been proved that the p-type inorganic semiconductor as a charge selective material or a charge transport material in organometallic lead halide perovskite solar cells (PSCs) shows a significant impact on solar cell performance. Therefore the study of p-type semiconductors is important to rationally design efficient DSCs and PSCs. In this review, recent published works on p-type DSCs and PSCs incorporated with an inorganic p-type semiconductor and our perspectives on this topic are discussed. Full article

(This article belongs to the Special Issue Dye Sensitized Solar Cells)

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20 pages, 1827 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Smart Distribution Systems

by Yazhou Jiang, Chen-Ching Liu and Yin Xu

Energies 2016, 9(4), 297; https://doi.org/10.3390/en9040297 - 19 Apr 2016

Cited by 31 | Viewed by 11125

Abstract

The increasing importance of system reliability and resilience is changing the way distribution systems are planned and operated. To achieve a distribution system self-healing against power outages, emerging technologies and devices, such as remote-controlled switches (RCSs) and smart meters, are being deployed. The [...] Read more.

The increasing importance of system reliability and resilience is changing the way distribution systems are planned and operated. To achieve a distribution system self-healing against power outages, emerging technologies and devices, such as remote-controlled switches (RCSs) and smart meters, are being deployed. The higher level of automation is transforming traditional distribution systems into the smart distribution systems (SDSs) of the future. The availability of data and remote control capability in SDSs provides distribution operators with an opportunity to optimize system operation and control. In this paper, the development of SDSs and resulting benefits of enhanced system capabilities are discussed. A comprehensive survey is conducted on the state-of-the-art applications of RCSs and smart meters in SDSs. Specifically, a new method, called Temporal Causal Diagram (TCD), is used to incorporate outage notifications from smart meters for enhanced outage management. To fully utilize the fast operation of RCSs, the spanning tree search algorithm is used to develop service restoration strategies. Optimal placement of RCSs and the resulting enhancement of system reliability are discussed. Distribution system resilience with respect to extreme events is presented. Test cases are used to demonstrate the benefit of SDSs. Active management of distributed generators (DGs) is introduced. Future research in a smart distribution environment is proposed. Full article

(This article belongs to the Special Issue Electric Power Systems Research)

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27 pages, 3191 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review of Modeling Bioelectrochemical Systems: Engineering and Statistical Aspects

by Shuai Luo, Hongyue Sun, Qingyun Ping, Ran Jin and Zhen He

Energies 2016, 9(2), 111; https://doi.org/10.3390/en9020111 - 18 Feb 2016

Cited by 68 | Viewed by 12309

Abstract

Bioelectrochemical systems (BES) are promising technologies to convert organic compounds in wastewater to electrical energy through a series of complex physical-chemical, biological and electrochemical processes. Representative BES such as microbial fuel cells (MFCs) have been studied and advanced for energy recovery. Substantial experimental [...] Read more.

Bioelectrochemical systems (BES) are promising technologies to convert organic compounds in wastewater to electrical energy through a series of complex physical-chemical, biological and electrochemical processes. Representative BES such as microbial fuel cells (MFCs) have been studied and advanced for energy recovery. Substantial experimental and modeling efforts have been made for investigating the processes involved in electricity generation toward the improvement of the BES performance for practical applications. However, there are many parameters that will potentially affect these processes, thereby making the optimization of system performance hard to be achieved. Mathematical models, including engineering models and statistical models, are powerful tools to help understand the interactions among the parameters in BES and perform optimization of BES configuration/operation. This review paper aims to introduce and discuss the recent developments of BES modeling from engineering and statistical aspects, including analysis on the model structure, description of application cases and sensitivity analysis of various parameters. It is expected to serves as a compass for integrating the engineering and statistical modeling strategies to improve model accuracy for BES development. Full article

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24 pages, 9983 KiB

Open AccessEditor’s ChoiceReview

Experimental and Numerical Studies of a High-Head Francis Turbine: A Review of the Francis-99 Test Case

by Chirag Trivedi, Michel J. Cervantes and Ole G. Dahlhaug

Energies 2016, 9(2), 74; https://doi.org/10.3390/en9020074 - 26 Jan 2016

Cited by 80 | Viewed by 13018

Abstract

Hydraulic turbines are widely used to meet real-time electricity demands. Computational fluid dynamic (CFD) techniques have played an important role in the design and development of such turbines. The simulation of a complete turbine requires substantial computational resources. A specific approach that is [...] Read more.

Hydraulic turbines are widely used to meet real-time electricity demands. Computational fluid dynamic (CFD) techniques have played an important role in the design and development of such turbines. The simulation of a complete turbine requires substantial computational resources. A specific approach that is applied to investigate the flow field of one turbine may not work for another turbine. A series of Francis-99 workshops have been planned to discuss and explore the CFD techniques applied within the field of hydropower with application to high-head Francis turbines. The first workshop was held in December 2014 at the Norwegian University of Science and Technology, Norway. The steady-state measurements were conducted on a model Francis turbine. Three operating points, part load, best efficiency point, and high load, were investigated. The complete geometry, meshing, and experimental data concerning the hydraulic efficiency, pressure, and velocity were provided to the academic and industrial research groups. Various researchers have conducted extensive numerical studies on the high-head Francis turbine, and the obtained results were presented during the workshop. This paper discusses the presented numerical results and the important outcome of the extensive numerical studies on the Francis turbine. The use of a wall function assuming equilibrium between the production and dissipation of turbulence is widely used in the simulation of hydraulic turbines. The boundary layer of hydraulic turbines is not fully developed because of the continuously-changing geometry and large pressure gradients. There is a need to develop wall functions that enable the estimation of viscous losses under boundary development for accurate simulations. Improved simulations and results enable reliable estimation of the blade loading. Numerical investigations on leakage flow through the labyrinth seals were conducted. The volumetric efficiency and losses in the seals were determined. The seal leakage losses formulated through analytical techniques are sufficient. Full article

(This article belongs to the Special Issue Hydropower)

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Other

32 pages, 538 KiB

Open AccessEditor’s ChoiceSystematic Review

A Review of Cybersecurity Concerns for Transactive Energy Markets

by Daniel Sousa-Dias, Daniel Amyot, Ashkan Rahimi-Kian and John Mylopoulos

Energies 2023, 16(13), 4838; https://doi.org/10.3390/en16134838 - 21 Jun 2023

Cited by 8 | Viewed by 2752

Abstract

Advances in energy generation and distribution technology have created the need for new power management paradigms. Transactive energy markets are integrated software and hardware systems that enable optimized energy management and direct trading between prosumers. This literature review covers unresolved security and privacy [...] Read more.

Advances in energy generation and distribution technology have created the need for new power management paradigms. Transactive energy markets are integrated software and hardware systems that enable optimized energy management and direct trading between prosumers. This literature review covers unresolved security and privacy vulnerabilities in the proposed implementations of such markets. We first performed a coarse search for such implementations. We then combed the resulting literature for references to privacy concerns, security vulnerabilities, and attacks that their system was either vulnerable to or sought to address. We did so with a particular focus on threats that were not mitigated by the use of blockchain technology, a commonly employed solution. Based on evidence from 28 peer-reviewed papers, we synthesized 14 categories of concerns and their proposed solutions. We found that there are some concerns that have been widely addressed, such as protecting trading history when using a public blockchain. Conversely, there were serious threats that are not sufficiently being considered. While a lack of real-world deployment has limited information about which attacks are most likely or feasible, there are clear areas of priority that we recommend to address going forward, including market attacks, false data injection attacks, single points of failure, energy usage data leakage, and privacy. Full article

(This article belongs to the Special Issue Digitization of Energy Supply and Demand Sides)

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23 pages, 403 KiB

Open AccessEditor’s ChoicePerspective

The Material Entropy and the Fourth Law of Thermodynamics in the Evaluation of Energy Technologies of the Future

by Aleksander Jakimowicz

Energies 2023, 16(9), 3861; https://doi.org/10.3390/en16093861 - 30 Apr 2023

Cited by 3 | Viewed by 5740

Abstract

The primary purpose of this article is to use the laws of thermodynamics, mainly the second and fourth laws, to evaluate three energy technologies of the future: fusion, solar, and fission. Among the criteria used to evaluate them, the most important are the [...] Read more.

The primary purpose of this article is to use the laws of thermodynamics, mainly the second and fourth laws, to evaluate three energy technologies of the future: fusion, solar, and fission. Among the criteria used to evaluate them, the most important are the amount of matter needed to sustain the technology itself and the environmental impact. Much emphasis is placed here on the fourth law of thermodynamics, which introduces the concept of material entropy. Zemansky–Georgescu-Roegen’s Law of Inevitable Dissipation of Useful Concentrated Matter states that, in the economic process, some matter is inevitably degraded and becomes unavailable matter. This has tremendous implications for humanity as a whole since the Earth is thermodynamically a closed system, meaning that it cannot exchange matter with space but is open to the flow of solar energy. This results in the need to conserve matter and natural resources. This law can be used as an important criterion for the selection of energy technology. Moreover, the flow–fund model, which was proposed by Georgescu-Roegen, was used to assess the viability of energy technologies. The final conclusion is that there is no Promethean technology of the third kind yet, but the closest to meeting this condition is solar technology. Technology based on nuclear fission has been rejected due to its adverse ecological effects, while fusion technology has proven to be less useful due to the matter criterion, the negative environmental impact, since radioactive waste only becomes safe for humans after 500 years, and the risks associated with nuclear proliferation. Solar technology can become Prometheus III only after all of humanity is involved with this project, which requires profound social changes, widespread demilitarization, and the development of organic agriculture. This implies the necessity of the emergence of a global solar society based on an economic system called solar communism. Full article

(This article belongs to the Special Issue Sustainable and Low Carbon Development in the Energy Sector)

13 pages, 1920 KiB

Open AccessEditor’s ChoicePerspective

Potential Pathway for Reliable Long-Term CO₂ Storage as Clathrate Hydrates in Marine Environments

by Beatrice Castellani

Energies 2023, 16(6), 2856; https://doi.org/10.3390/en16062856 - 20 Mar 2023

Cited by 14 | Viewed by 3732

Abstract

A countermeasure to global warming is removing high CO₂ amounts from the atmosphere and locating the emitted CO₂ into long-term stable carbon storage sites. The sequestration technologies must be reliable, long-lasting, and environmentally friendly. An alternative and innovative approach that may [...] Read more.

A countermeasure to global warming is removing high CO₂ amounts from the atmosphere and locating the emitted CO₂ into long-term stable carbon storage sites. The sequestration technologies must be reliable, long-lasting, and environmentally friendly. An alternative and innovative approach that may meet the sequestration requirements is CO₂ storage as clathrate hydrates in marine environments. Extensive research has been devoted to CO₂-CH₄ replacement in natural gas hydrates. Another option is the direct formation of CO₂ hydrates into deep ocean water or into marine underfloor sediments. This article deals with the positioning of direct hydrate-based CO₂ storage among the other traditional geological options and the discussion of new, by-far, state-of-the-art knowledge required for the development of a hydrate-based CO₂ storage pathway that is reliable, stable, durable, efficient, and environmentally benign. Full article

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6 pages, 667 KiB

Open AccessEditor’s ChoicePerspective

The Green Versus Green Trap and a Way Forward

by Haris Doukas, Alexandros Nikas, Giorgos Stamtsis and Ioannis Tsipouridis

Energies 2020, 13(20), 5473; https://doi.org/10.3390/en13205473 - 20 Oct 2020

Cited by 19 | Viewed by 4957

Abstract

Massive deployment of renewables is considered as a decisive step in most countries’ climate efforts. However, at the local scale, it is also perceived by many as a threat to their rich and diverse natural environment. With this perspective, we argue that this [...] Read more.

Massive deployment of renewables is considered as a decisive step in most countries’ climate efforts. However, at the local scale, it is also perceived by many as a threat to their rich and diverse natural environment. With this perspective, we argue that this green versus green pseudo-dilemma highlights how crucial a broad societal buy-in is. New, transparent, participatory processes and mechanisms that are oriented toward social licensing can now be employed. A novel, integrative research agenda must orbit around co-creation to enable and promote resource co-management and co-ownership where possible, with increased consensus. Full article

(This article belongs to the Special Issue Sustainable Management of Energy Resources, Energy Strategies and Climate Change)

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10 pages, 1031 KiB

Open AccessFeature PaperEditor’s ChoiceCommentary

Will Electric Vehicles Be Killed (again) or Are They the Next Mobility Killer App?

by Christian Thiel, Anastasios Tsakalidis and Arnulf Jäger-Waldau

Energies 2020, 13(7), 1828; https://doi.org/10.3390/en13071828 - 10 Apr 2020

Cited by 26 | Viewed by 7338

Abstract

Electric vehicles (EVs) have been around for more than a hundred years. Nevertheless, their deployment has not been a sustainable success up until now. Many scientists, engineers and policymakers argue that EVs are a promising, maybe even indispensable option to achieve ambitious decarbonization [...] Read more.

Electric vehicles (EVs) have been around for more than a hundred years. Nevertheless, their deployment has not been a sustainable success up until now. Many scientists, engineers and policymakers argue that EVs are a promising, maybe even indispensable option to achieve ambitious decarbonization goals, if powered by electricity from renewable energy sources. At the moment, the EVs market is gaining a lot of momentum and we may be near the point of no return for a sustained mass market deployment of electric vehicles. Many papers exist that describe future prospects of EVs. In our commentary we try to provide a bigger picture view and look at market and societal aspects. We analyze why previous generations of EVs were not successful and how current electric vehicles could become a sustainable success. We perform a semi-quantitative Strengths, Weaknesses, Opportunities, Threats (SWOT) analysis and find that current electric vehicle designs are technologically on par with or better than conventional alternatives. Car buyers go electric when the economics make sense to them. We conclude that incentives are needed for electric vehicles until battery costs lower—as much as to allow EVs to become cheaper—from a total cost of ownership (TCO) perspective, than other alternatives. Other policy measures are needed to overcome remaining barriers, especially in supporting the setup and operation of publicly accessible recharging points to overcome range anxiety. EVs in isolation may not be the next mobility killer app. The real next mobility killer app may emerge as an autonomous shared EV in a world where the border between public and private transport will cease to exist. The findings of our commentary are relevant for scientists, policymakers and industry. Full article

(This article belongs to the Section E: Electric Vehicles)

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