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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A: Sustainable Energy".

Deadline for manuscript submissions: closed (13 July 2024) | Viewed by 14872

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Special Issue Editor

Dr. Vedran Mrzljak

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Guest Editor

Faculty of Engineering, University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia
Interests: internal combustion engines; gas and steam turbines; marine power plants; power/energy systems; energy and exergy analysis; optimization

Special Issue Information

Dear Colleagues,

The Guest Editor is inviting submissions to a Special Issue of Energies on the subject area of “Sustainable/Renewable Energy Systems Analysis and Optimization”. As the energy sector is currently facing many challenges, the analysis of various sustainable and renewable energy systems as well as their optimization are pressing challenges. Understanding operation characteristics, detecting problems, performing improvements and optimizing any energy system inevitably leads to economic, environmental and other benefits which can be achieved during exploitation.

This Special Issue will deal with analysis and optimization of various sustainable and renewable energy systems. Topics of interest for publication include, but are not limited to:

Conventional energy systems;
Marine energy and power systems;
Renewable and sustainable energy processes;
Energy storage systems;
Electric energy systems;
Energy management;
Novel energy processes;
Energy processes: environmental impact;
Energy system performance improvement;
Optimal energy system operation guidelines;
Various load conditions;
Process analysis;
Optimization algorithms;
Application of artificial intelligence methods and processes in the energy sector.

Dr. Vedran Mrzljak
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. Energies is an international peer-reviewed open access semimonthly 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

energy systems
marine energy systems
renewable and sustainable processes
energy storage
electric energy systems
energy management
environmental impact
performance improvement
various load conditions
process analysis
optimization
artificial intelligence

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Published Papers (9 papers)

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18 pages, 10952 KiB

Open AccessArticle

The Coordinated Power Control of Flexible DC Microgrids in Sustainably Optimized Yacht Marinas

by Andrea Alessia Tavagnutti, Serena Bertagna, Marco Dalle Feste, Massimiliano Chiandone, Daniele Bosich, Vittorio Bucci and Giorgio Sulligoi

Energies 2024, 17(2), 521; https://doi.org/10.3390/en17020521 - 21 Jan 2024

Viewed by 1178

Abstract

Nowadays, the industrial world is undergoing a disruptive transformation towards more environmentally sustainable solutions. In the blue economy, this new approach is not only expressed in the domain of actual vessels, but also in the development of charging infrastructure, displaying a notable transition towards more eco-friendly solutions. The key focus lies in adopting flexible power systems capable of integrating renewable energy sources and storage technologies. Such systems play a crucial role in enabling a shift towards low-emission maritime transport. The emissions reduction goal extends beyond onboard shipboard distribution systems, encompassing also the design of supplying platforms and marinas. This study explores the implementation of a controlled DC microgrid tailored to efficient management of power flows within a yacht marina. Once having established the interfaces for the vessels at berth, the integration between the vessels, the onshore photovoltaic plant and the battery storage unit is made possible thanks to the coordinated management of multiple power converters. The overarching goal is to curtail reliance on external energy sources. Within this DC microgrid framework, a centralized controller assumes a pivotal role in orchestrating the power sources and loads. This coordinated management is essential to achieve sustainable operations, ultimately leading to the reduction of emissions from both ships and onshore power plants. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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17 pages, 11195 KiB

Open AccessArticle

Renewable Electric Energy Storage Systems by Storage Spheres on the Seabed of Deep Lakes or Oceans

by Horst Werner Schmidt-Böcking, Gerhard Luther, Michael Düren, Matthias Puchta, Tom Bender, Andreas Garg, Bernhard Ernst and Heinz Frobeen

Energies 2024, 17(1), 73; https://doi.org/10.3390/en17010073 - 22 Dec 2023

Cited by 1 | Viewed by 1702

Abstract

This paper describes a new underwater pumped storage hydropower concept (U.PSH) that can store electric energy by using the high water pressure on the seabed or in deep lakes to accomplish the energy transition from fossil to renewable sources. Conventional PSH basically consists of two storage reservoirs (upper and lower lake) at different topographical heights. It needs special topographic conditions, which are only limitedly available in mountain regions. Furthermore, due to the lack of acceptance and the environmental impact, new conventional PSH projects are very unlikely to be built in larger numbers in Europe in the near future. The presented solution solves these issues by placing the storage system on the seabed, thus having other geographical requirements. It operates as follows: in contrast to well-known conventional PSH plants, which use two separated water reservoirs of different heights, the U.PSH concept uses the static pressure of the water column in deep waters by installing a hollow concrete sphere in deep water. Storage of electricity is achieved by using a reversible pump in the hollow sphere. Upon opening a valve, water flows into the sphere, driving a turbine/generator, thereby discharging the storage device. In order to re-charge, the water is pumped out of the sphere against the pressure of the surrounding water. The power and energy, respectively, are proportional to the surrounding water pressure at the seabed. The amount of energy stored depends on the water depth and the volume of the spheres. The spheres need a cable connection to the shore or to a close-by floating transformer station (e.g., an offshore wind plant). No other connections such as pipes are needed. The functional principle of this energy storage technology, its state of the art, its storage capacity and the shape and size of the required spheres are discussed in this paper. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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27 pages, 7287 KiB

Open AccessArticle

Economic Evaluation of a 1 MW_el Capacity Power-to-Biomethane System

by Attila Bai, Péter Balogh, Adrián Nagy, Zoltán Csedő, Botond Sinóros-Szabó, Gábor Pintér, Sanjeev Kumar Prajapati, Amit Singh and Zoltán Gabnai

Energies 2023, 16(24), 8009; https://doi.org/10.3390/en16248009 - 11 Dec 2023

Cited by 1 | Viewed by 1769

Abstract

Power-to-biomethane (bio-P2M) is a novel technology that combines the long-term storage of periodically available renewable energy sources (RES) and the upgrading of biogas. This article introduces a complex economic analysis of a 1 megawatt electric (MW_el) capacity bio-P2M system based on economic characteristics considered to be typical in practice. The evaluation includes an investment analysis to present the basic scenario, a sensitivity analysis and a unit cost calculation to show the economic viability, the cost structure and the possible reserves of the synthetic natural gas (SNG) as a final output. The risk analysis is executed using Monte Carlo simulation, and the final results are the mean and standard deviation of the outputs, distribution functions and probabilities. Our results show that a significant state subsidy would be needed to boost competitiveness either in terms of investment costs (44% in our calculation) or in technology development to improve technological effectiveness. Another important competitiveness issue is the full utilization of the plant and the lowest possible price for the electricity used. If both cannot be optimized at the same time, then the first one is more important. Natural gas prices and the full utilization of waste heat might result in smaller changes. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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18 pages, 586 KiB

Open AccessArticle

Decentralized Smart Grid Stability Modeling with Machine Learning

by Borna Franović, Sandi Baressi Šegota, Nikola Anđelić and Zlatan Car

Energies 2023, 16(22), 7562; https://doi.org/10.3390/en16227562 - 14 Nov 2023

Cited by 4 | Viewed by 1732

Abstract

Predicting the stability of a Decentralized Smart Grid is key to the control of such systems. One of the key aspects that is necessary when observing the control of DSG systems is the need for rapid control. Due to this, the application of AI-based machine learning (ML) algorithms may be key to achieving a quick and precise stability prediction. In this paper, the authors utilize four algorithms—a multilayer perceptron (MLP), extreme gradient boosting (XGB), support vector machines (SVMs), and genetic programming (GP). A public dataset containing 30,000 points was used, with inputs consisting of

τ

—the time needed for a grid participant to adjust consumption/generation, p—generated power, and

γ

—the price elasticity coefficient for four grid elements; and outputs consisting of

s t a b

—the eigenvalue of stability and

s t a b f

, the categorical stability of the system. The system was modeled using the aforementioned methods as a regression model (targeting

s t a b

) and a classification model (targeting

s t a b f

). Modeling was performed with and without the

τ

values due to their low correlation. The best results were achieved with the XGB algorithm for classification, with and without the

τ

values as inputs—indicating them as being unnecessary. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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15 pages, 7791 KiB

Open AccessArticle

Microbial Fuel Cell as Battery Range Extender for Frugal IoT

by Carlos Augusto Berlitz, Andrea Pietrelli, Fabien Mieyeville, Gaël Pillonnet and Bruno Allard

Energies 2023, 16(18), 6501; https://doi.org/10.3390/en16186501 - 9 Sep 2023

Cited by 2 | Viewed by 1222

Abstract

The simplest DC/DC converter for supplying an Internet-of-Things device is definitely a switched-capacitor converter. The voltage from a mere 1.2 V battery may be stepped up to 2 V. A quite large operating frequency is required in order to reach the smallest possible output impedance value of the DC/DC converter. The overall efficiency is then limited even more so if the power area density of the system should be large. The article details how a microbial fuel cell may substitute one capacitor in the switched-capacitor converter, achieving a better efficiency at a much lower operating frequency. In that perspective, the microbial fuel cell acts as a kind of battery range extender. Some limitations exist that are discussed. A simple converter is experimentally evaluated to support the discussion. Substituting a microbial fuel cell inside a 100

μ

W switched-capacitor converter compensates for losses in the order of 5% of efficiency. Moreover, the microbial fuel cell extends the lifespan of the battery, as 1.6 V output voltage is still possible when the battery voltage drops to 0.8 V. More than 94% efficiency is measured for a range of output power between 100

μ

W and 1 mW, which is sufficient to address a lot of frugal IoT applications. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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30 pages, 6575 KiB

Open AccessArticle

Part-Load Energy Performance Assessment of a Pumped Thermal Energy Storage System for an Energy Community

by Emanuele Nadalon, Ronelly De Souza, Melchiorre Casisi and Mauro Reini

Energies 2023, 16(15), 5720; https://doi.org/10.3390/en16155720 - 31 Jul 2023

Cited by 3 | Viewed by 1289

Abstract

Research on pumped thermal energy storage (PTES) has gained considerable attention from the scientific community. Its better suitability for specific applications and the increasing need for the development of innovative energy storage technologies are among the main reasons for that interest. The name Carnot Battery (CB) has been used in the literature to refer to PTES systems. The present paper aims to develop an energy analysis of a CB comprising a high-temperature two-stage heat pump (2sHP), an intermediate thermal storage (latent heat), and an organic Rankine cycle (ORC). From a broad perspective, the CB is modeled considering two types of heat inputs for the HP: a cold reservoir in the ground (at a constant temperature of 12 °C throughout the entire year) and a heat storage at 80 °C (thermally-integrated PTES—TI-PTES). The first part defines simple models for the HP and ORC, where only the cycles’ efficiencies are considered. On this basis, the storage temperature and the kind of fluids are identified. Then, the expected power-to-power (round-trip) efficiency is calculated, considering a more realistic model, the constant size of the heat exchangers, and the off-design operation of expanders and compressors. The model is simulated using Engineering Equation Solver (EES) software (Academic Professional V10.998-3D) for several working fluids and different temperature levels for the intermediate CB heat storage. The results demonstrate that the scenario based on TI-PTES operation mode (toluene as the HP working fluid) achieved the highest round-trip efficiency of 80.2% at full load and 50.6% round-trip efficiency with the CB operating at part-load (25% of its full load). Furthermore, when the HP working fluid was changed (under the same scenario) to R1336mzz(Z), the round-trip full-load and part-load efficiencies dropped to 72.4% and 46.2%, respectively. The findings of this study provide the HP and ORC characteristic curves that could be linearized and used in a thermo-economic optimization model based on a Mixed-Integer Linear Programming (MILP) algorithm. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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26 pages, 6827 KiB

Open AccessArticle

Thermodynamic Analysis and Improvement Potential of Helium Closed Cycle Gas Turbine Power Plant at Four Loads

by Vedran Mrzljak, Igor Poljak, Maro Jelić and Jasna Prpić-Oršić

Energies 2023, 16(15), 5589; https://doi.org/10.3390/en16155589 - 25 Jul 2023

Cited by 1 | Viewed by 1249

Abstract

This paper presents thermodynamic and improvement potential analyses of a helium closed-cycle gas turbine power plant (Oberhausen II) and dominant plant components at four loads. DESIGN LOAD represents optimal operating conditions that cannot be obtained in exploitation but can be used as a guideline for further improvements. In real plant exploitation, the highest plant efficiency is obtained at NOMINAL LOAD (31.27%). Considering all observed components, the regenerator (helium-helium heat exchanger) is the most sensitive to the ambient temperature change. An exact comparison shows that the efficiency decrease of an open-cycle gas turbine power plant during load decrease is approximately two and a half or more times higher in comparison to a closed-cycle gas turbine power plant. Plant improvement potential related to all turbomachines leads to the conclusion that further improvement of the most efficient turbomachine (High Pressure Turbine—HPT) will increase whole plant efficiency more than improvement of any other turbomachine. An increase in the HPT isentropic efficiency of 1% will result in an average increase in whole plant efficiency of more than 0.35% at all loads during plant exploitation. In the final part of this research, it is investigated whether the additional heater involvement in the plant operation results in a satisfactory increase in power plant efficiency. It is concluded that in real exploitation conditions (by assuming a reasonable helium pressure drop of 5% in the additional heater), an additional heating process cannot be an improvement possibility for the Oberhausen II power plant. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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Review

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19 pages, 4242 KiB

Open AccessReview

Innovation Solution in Photovoltaic Sector

by Filip Czepło and Piotr F. Borowski

Energies 2024, 17(1), 265; https://doi.org/10.3390/en17010265 - 4 Jan 2024

Cited by 4 | Viewed by 1598

Abstract

The modern world is moving towards a zero-emission economy; therefore, various actions are being taken to reduce the share of fossil fuels in energy production. The article examines the potential for the continued expansion of photovoltaic farms, with a special emphasis on farms utilising east–west panel orientation. The east–west orientation is an innovative solution with many advantages over the traditional north–south arrangement. The paper also makes a detailed assessment of the photovoltaic farm environment by applying two analyses based on the following factors: Political, Economic, Social, and Technological (PEST) and Demographic, Economic, Environmental, Political, Legal, Informational, Social, and Technological (DEEPLIST) factors. This is followed by an insightful, comprehensive review of the most important factors that contribute to the efficiency of photovoltaic installations, namely site conditions, existing infrastructure, and ability to connect to the electricity grid. The paper also devotes space to an analysis of daily energy price changes that affect the economic efficiency of the installation and discusses the potential for energy storage in the context of photovoltaic farms. The development of photovoltaics also requires investing in energy storage. All discussed issues fall within the scope of photovoltaic farm development and optimal use of energy resources. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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24 pages, 6113 KiB

Open AccessReview

Energy Harvesting Opportunities in Geoenvironmental Engineering

by Leonardo Marchiori, Maria Vitoria Morais, André Studart, António Albuquerque, Luis Andrade Pais, Luis Ferreira Gomes and Victor Cavaleiro

Energies 2024, 17(1), 215; https://doi.org/10.3390/en17010215 - 30 Dec 2023

Cited by 3 | Viewed by 1942

Abstract

Geoenvironmental engineering involves defining solutions for complex problems, such as containment systems management, contaminant transport control, wastewater management, remediation of contaminated sites and valorization of geomaterials and wastes. In the last years, energy harvesting (EH)—or energy scavenging—methods and technologies have been developed to reduce the dependence on traditional energy sources, namely fossil fuels, and nuclear power, also responding to the increase in energy demands for human activities and to fulfill sustainable development goals. EH in geoenvironmental works and the surrounding soil and water environment includes a set of processes for capturing and accumulating energy from several sources considered wasted or unusable associated with soil dynamics; the stress and strain of geomaterials, hydraulic, vibrations, biochemical, light, heating and wind sources can be potential EH systems. Therefore, this work presents a review of the literature and critical analysis on the main opportunities for EH capturing, accumulating and use in geoenvironmental works, among basic electric concepts and mechanisms, analyzing these works in complex conditions involving biological-, chemical-, mechanical-, hydraulic- and thermal-coupled actions, concluding with the main investigation and challenges within geoenvironmental aspects for EH purposes. Full article

(This article belongs to the Special Issue Sustainable/Renewable Energy Systems Analysis and Optimization)

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