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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "B2: Clean Energy".

Deadline for manuscript submissions: closed (10 August 2023) | Viewed by 9464

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Special Issue Editors

Dr. Tomasz Garbowski

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Guest Editor

Faculty of Environmental and Mechanical Engineering, Poznan University of Life Sciences, Wojska Polskiego 50, 60-637 Poznan, Poland
Interests: computational mechanics; structural optimization; mathematical programming; inverse problems; mechanics of materials; paper physics
Special Issues, Collections and Topics in MDPI journals

Dr. Anna Szymczak-Graczyk

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Guest Editor

Department of Construction and Geoengineering, Poznan University of Life Sciences, Piątkowska 94 E, 60-649 Poznań, Poland
Interests: structures; rectangular tanks; close rectangular tanks; finite dfference method; building loads

Special Issue Information

Dear Colleagues,

This Special Issue of Energies is devoted to the various green energies as energy sources, the use of which is not associated with a long-term deficit, because the resource is renewed in a relatively short time. Such sources are the sun, wind, water (rivers, tides and sea waves), as well as nuclear energy in a closed fuel cycle, biomass, biogas, bioliquids and biofuels. Renewable energy also includes heat obtained from the ground (geothermal energy), air (aerothermal energy), and water (hydrothermal energy). The former are rather used by state-owned companies or large commercial energy companies, while the latter are often used in households. This Special Issue will enable scientists and engineers to exchange the latest knowledge on advances both in theoretical and computational issues related to green energy production and its practical use.

Among others, the following topics are the main fields of interest for this Special Issue: optimal use of green energy; the use of advanced computer methods in the optimization of energy consumption; advanced techniques in the production of green energy; artificial intelligence in green energy management; passive houses; numerical, and analytical computational techniques in zero-energy structures; laboratory testing methods; geo-, aero- and hydro-thermal energy in passive structures. There are no particular restrictions on the thematic areas of this Special Issue as long as the submitted works relate to green energy. Energies readers and authors are encouraged to send their latest research work in these areas, with an emphasis on experimental validations and empirical proofs.

Dr. Tomasz Garbowski
Dr. Anna Szymczak-Graczyk
Guest Editors

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.

Published Papers (6 papers)

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Research

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18 pages, 10441 KiB

Open AccessArticle

Laboratory Research on Hydraulic Losses on SHP Inlet Channel Trash Racks

by Natalia Walczak, Zbigniew Walczak and Tomasz Tymiński

Energies 2022, 15(20), 7602; https://doi.org/10.3390/en15207602 - 14 Oct 2022

Cited by 2 | Viewed by 1171

Abstract

There is currently a growing trend towards renewable energy sources, which are characterised by a guaranteed power supply and low failure rate. Hydropower plants (small or large) are an example of such a source. They supply a total of 16% of the world’s electricity. The advantages of a small hydropower plant include the relatively simple construction process and the lack of need for upstream water storage. SHPs are one of the most cost-effective and environmentally friendly energy technologies, which is why they are steadily increasing in popularity. One of the important components of SHPs are the trash racks in the inlet channels. Their main purpose is to catch debris and other elements carried downstream and to prevent these pollutants from reaching the turbine units. They can also protect migrating ichthyofauna such as larger fish. If trash racks are installed in the inlet channel, hydraulic losses are to be expected due to the reduction in the flow cross-section through the racks (bars) themselves and through the accumulation of debris and various types of trash on these racks. Energy losses on the trash racks affect the financial aspect of SHP investments. This paper presents the results of laboratory tests on trash racks for SHPs by taking into account the different shapes of the bars used, their number and spacing, and the angles of the trash racks to estimate the hydraulic losses on the trash racks. The measured values of hydraulic losses Δh on the trash racks varied according to the type of trash racks, the density of the bars in the cross-section, and the angle of the trash racks from the horizontal, reaching the highest values on the trash racks with angle bars (AB). They were almost eight times greater than those recorded on cylindrical-bar (CB) trash racks, although they involved different angles. It was shown that the discrepancy in the magnitude of losses on trash racks can be large, even for the same type of trash racks. It depends significantly on the design (shape and bar spacing) of the trash racks and the way the trash racks are installed. Depending on the inclination angle, the increase in energy losses reached 70% for angle bars, 60% for flat-bar trash racks, and almost 40% for cylindrical bars. The values of energy loss as well as the loss coefficient β varied non-linearly for the different bar types depending on the angle of inclination of the gratings, and the degree of this non-linearity depended on the type of bars and the blockage ratio of the section. The presented research results can be useful both during the design and the operation of an SHP. Full article

(This article belongs to the Special Issue Green Energy - Modern Digital Techniques)

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19 pages, 6061 KiB

Open AccessArticle

Dextrins as Green and Biodegradable Modifiers of Physicochemical Properties of Cement Composites

by Marta Sybis, Emilia Konował and Krystyna Prochaska

Energies 2022, 15(11), 4115; https://doi.org/10.3390/en15114115 - 3 Jun 2022

Cited by 5 | Viewed by 1873

Abstract

Growing interest in the use of natural organic compounds in the production of green concrete with the use of plasticizers has been particularly noticeable in the literature of recent decades. Starch is an attractive material due to its abundance, the low cost of sourcing it, and its biodegradability, biocompatibility, and susceptibility to modification. The objective of the study was to evaluate the effect of starch hydrolysate additives on the physicochemical properties of cement composites and concrete. Compressive strength tests and cement slurry rheology measurements were carried out for water–cement ratios from 0.40 to 0.50 and for amounts of added dextrin from 0.0 to 0.7% in relation to the cement weight. The dextrins used were characterized in terms of their viscosity, polymerisation degree, and surface activity in air/water systems. Conducted research indicates that even the minimum content of dextrin increases the fluidization of cement mixes (the flow diameter increased by 67.5% compared with the mixture without the admixture), enables the reduction of mixing water, and contributes to the compressive strength of cement mortars. A further decrease in the w/c ratio to the value of 0.40 resulted in an increase in the strength value of up to 67.9 MPa, which provided a 40% increase in strength. The degree of the polymerisation of added dextrin is seen as having an effect on the physical parameters of the cement mortar; the shorter the polymer chain of the studied dextrin, the more packed the adsorbent layer, and the greater the flow diameter of the cement mortar. Full article

(This article belongs to the Special Issue Green Energy - Modern Digital Techniques)

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Review

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25 pages, 4126 KiB

Open AccessReview

Wind Parks in Poland—New Challenges and Perspectives

by Karolina Talarek, Anna Knitter-Piątkowska and Tomasz Garbowski

Energies 2022, 15(19), 7004; https://doi.org/10.3390/en15197004 - 23 Sep 2022

Cited by 7 | Viewed by 2020

Abstract

The wind farm market in Poland evolved very dynamically in the years 2000–2015. Unfortunately, the high public resistance caused the government in 2016 to freeze the development of this industry by introducing a restrictive act, which practically stopped the wind farm industry overnight. The climate aspects, such as reduction of the carbon footprint, which have been considered and widely discussed for several years at the European Union forums, were a chance to change this situation. The new regulations gave hope that the wind energy industry in Poland would soon be unblocked, unfortunately the commitment to coal was still an effective barrier, which is clearly visible in the presented study. The Russian aggression against Ukraine, which resulted in a blockade of hydrocarbon imports, has completely changed the center of gravity of the Polish energy and heating economy. The article focuses on the accelerated changes in the renewable energy sources (RESs) and the related legislation, especially emphasizing the prospect of building offshore wind farms. The huge European energy crisis means that new solutions, both legislative and technological, which will allow to quickly switch to green energy, must appear in Poland immediately. The direct conversion of green energy from RES farms into thermal energy in the planned investment in heat energy plants is discussed. This article also presents a broad view of new opportunities as well as the challenges and prospects that have recently arisen in the wind energy industry in Poland. Full article

(This article belongs to the Special Issue Green Energy - Modern Digital Techniques)

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Other

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18 pages, 1724 KiB

Open AccessEssay

Storing Carbon in Forest Biomass and Wood Products in Poland—Energy and Climate Perspective

by Zbigniew W. Kundzewicz, Janusz Olejnik, Marek Urbaniak and Klaudia Ziemblińska

Energies 2023, 16(15), 5788; https://doi.org/10.3390/en16155788 - 3 Aug 2023

Cited by 1 | Viewed by 1055

Abstract

Huge amounts of carbon being sequestered in forest ecosystems make them an important land carbon sink at the global scale. Their ability to withdraw carbon dioxide (CO

_{2}

) from the atmosphere, whose concentration is gradually increasing due to anthropogenic emissions, renders them [...] Read more.

Huge amounts of carbon being sequestered in forest ecosystems make them an important land carbon sink at the global scale. Their ability to withdraw carbon dioxide (CO

_{2}

) from the atmosphere, whose concentration is gradually increasing due to anthropogenic emissions, renders them important natural climate-mitigation solutions. The urgent need for transition from high to zero net emission on country, continental, and global scales, to slow down the warming to an acceptable level, calls for the analysis of different economic sectors’ roles in reaching that ambitious goal. Here, we examine changes in CO

_{2}

emission and sequestration rates during recent decades focusing on the coal-dominated energy sector and Land Use, Land-Use Change, and Forestry (LULUCF) as well as wood production at the country level. The main purpose of the presented study is to examine the potential of storing carbon in standing forest biomass and wood products in Poland as well as the impact of disturbances. The ratio of LULUCF absorption of CO

_{2}

to its emission in Poland has ranged from about 1% in 1992 to over 15% in 2005. From a climate-change mitigation point of view, the main challenge is how to maximize the rate and the duration of CO

_{2}

withdrawal from the atmosphere by its storage in forest biomass and wood products. Enhancing carbon sequestration and storage in forest biomass, via sustainable and smart forestry, is considered to be a nature-based climate solution. However, not only forests but also wood-processing industries should be included as important contributors to climate-change mitigation, since harvested wood products substitute materials like concrete, metal, and plastic, which have a higher carbon footprint. The energy perspective of the paper embraces two aspects. First, CO

_{2}

sequestration in forests and subsequently in harvested wood products, is an effective strategy to offset a part of national CO

_{2}

emissions, resulting largely from fossil fuel burning for energy-production purposes. Second, wood as biomass is a renewable energy source itself, which played an important role in sustaining energy security for many individual citizens of Poland during the unusual conditions of winter 2022/2023, with a scarce coal supply. Full article

(This article belongs to the Special Issue Green Energy - Modern Digital Techniques)

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14 pages, 2322 KiB

Open AccessBrief Report

Influences of a Variety of Reinforcements on the Durability of Reinforced Bitumen Sheets Operating at Variable Temperatures

by Barbara Francke, Anna Szymczak-Graczyk, Barbara Ksit, Jarosław Szulc and Jan Sieczkowski

Energies 2023, 16(9), 3647; https://doi.org/10.3390/en16093647 - 24 Apr 2023

Viewed by 1081

Abstract

This manuscript provides an overview of the most commonly-produced bitumen roofing sheets, focusing on the types of reinforcements used for their production and the reinforcements’ effects on the durability of tensile mechanical properties of roofing sheets under thermal loads. The paper includes the analysis of working conditions of roof coverings in the mid-European transitional climate, i.e., exposed to temperatures passing through 0 °C for three seasons in a year, periodic exposure to negative temperatures reaching −15 °C and positive temperatures up to +70 °C, justifying the above-mentioned emphasis on thermal load. It draws attention to technical problems related to the cooperation of roofing sheets with roofing substrates, with particular emphasis on concrete substrates. For the purposes of the work, the analyses were carried out with regard to the assessment of the service life of roof coverings made of various reinforcements working in conditions of variable temperatures and thus exposed to the transfer of thermal movements of substrate plates. The analyses also included the impact of different coefficients of thermal expansion of the materials in contact with other materials within roof coverings on the incidence of damage to cover layers. Particular attention was paid to the conditions resulting from the production process of roofing sheets effect on the durability of roof coverings made of these materials. Additionally, there were set directions for further work to calculate the impact of stresses, arising in layers of roof coverings during their operation in changeable negative and positive temperatures, on the incidence of mechanical damage to these coverings. Full article

(This article belongs to the Special Issue Green Energy - Modern Digital Techniques)

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13 pages, 3104 KiB

Open AccessCase Report

The Direct-Contact Gravel, Ground, Air Heat Exchanger—Application in Single-Family Residential Passive Buildings

by Bartosz Radomski, Franciszek Kowalski and Tomasz Mróz

Energies 2022, 15(17), 6110; https://doi.org/10.3390/en15176110 - 23 Aug 2022

Cited by 2 | Viewed by 1346

Abstract

This paper presents proposals for using the direct-contact gravel, ground, air heat exchanger in single-family residential buildings with a passive house standard, according to the Passive House Institute (PHI). The methodology of their application consists of using heat and cold from the ground at an insignificant depth (about 1.5–4.0 m below the ground level for the central European climate) through an aggregate that is buried in the ground. This solution of simple installations is used for preheating and cooling fresh air drawn into the building through a mechanical ventilation system with heat recovery. In more complex applications it can be integrated with the source of heat and cold in passive buildings to create complete heating, cooling, and ventilation systems. In both cases, the air flowing through the exchanger is cooled and dried in summer, heated and humidified in winter, and filtered from pollen and bacteria all year. Direct contact of the deposit with the surrounding native soil facilitates rapid regeneration of the bed temperature. This article presents several proposals for integration with systems ensuring climatic comfort in a passive building, as exemplary applications. The paper presents preliminary estimates of energy (savings of up to 70% of electrical energy consumed), economic (SPBT = 3.65 years), and environmental (69.5% reduction in CO₂ emissions) benefits related to implementing this solution in various configurations of technological systems for buildings in Poland. The calculations were carried out for the city of Poznań, taking into account the hourly intervals and using the author’s code written in MS Excel. The analysis of the operation of the direct-contact gravel, ground, air heat exchanger (GGAHE) system is based on a theoretical heat and mass exchange model. The integrated solutions of technical systems presented in this article provide an interesting alternative to traditional heating, cooling, and ventilation systems. Full article

(This article belongs to the Special Issue Green Energy - Modern Digital Techniques)

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