Energies

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14 pages, 4853 KiB

Open AccessArticle

Influence of Untreated Metal Waste from 3D Printing on Electrical Properties of Alkali-Activated Slag Mortars

by Lukáš Fiala, Michaela Petříková, Martin Keppert, Martin Böhm, Jaroslav Pokorný and Robert Černý

Energies 2021, 14(23), 8178; https://doi.org/10.3390/en14238178 - 06 Dec 2021

Viewed by 1633

Abstract

The negative environmental impact of cement production emphasizes the need to use alternative binders for construction materials. Alkali-activated slag is a more environmentally friendly candidate which can be utilized in the design of mortars with favorable material properties. However, the electrical properties of [...] Read more.

The negative environmental impact of cement production emphasizes the need to use alternative binders for construction materials. Alkali-activated slag is a more environmentally friendly candidate which can be utilized in the design of mortars with favorable material properties. However, the electrical properties of such materials are generally poor and need to be optimized by various metallic or carbon-based admixtures to gain new sophisticated material functions, such as self-sensing, self-heating, or energy harvesting. This paper investigates the influence of waste metal powder originating from the 3D printing process on the material properties of alkali-activated slag mortars. The untreated metal powder was characterized by means of XRD and SEM/EDS analyses revealing high nickel content, which was promising in terms of gaining self-heating function due to the high electrical conductivity and stability of nickel in a highly alkaline environment. The designed mortars with the waste metal admixture in the amount up to 250 wt.% to the slag and aggregates were then characterized in terms of basic physical, thermal, and electrical properties. Compared to the reference mortar, the designed mortars were of increased porosity of 17–32%. The thermal conductivity of ~1–1.1 W/m·K was at a favorable level for self-heating. However, the electrical conductivity of ~10⁻⁶ S/m was insufficient to allow the generation of the Joule heat. Even though a high amount of 3D printing waste could be used due to the good workability of mixtures, its additional treatment will be necessary to achieve reasonable, effective electrical conductivity of mortars resulting in self-heating function. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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13 pages, 1188 KiB

Open AccessArticle

Environmental Efficiency Aspects of Basalt Fibers Reinforcement in Concrete Mixtures

by Jan Fořt, Jan Kočí and Robert Černý

Energies 2021, 14(22), 7736; https://doi.org/10.3390/en14227736 - 18 Nov 2021

Cited by 19 | Viewed by 3102

Abstract

Modern building materials must fulfill not only functional performance criteria but also reduce the environmental impact accompanied by their production. Within the past decades, fiber-reinforced materials have been found to be promising and durable materials that can be utilized in various fields. Among [...] Read more.

Modern building materials must fulfill not only functional performance criteria but also reduce the environmental impact accompanied by their production. Within the past decades, fiber-reinforced materials have been found to be promising and durable materials that can be utilized in various fields. Among a wide range of reinforcement types, basalt fibers have been introduced as an alternative to broadly used steel fibers. As informed by the available literature, benefits linked with less energy-intensive production indicate a very good potential application of this material in terms of functional properties and, at the same time, a reduction in environmental burden. However, only a very limited amount of information is available on the actual impact of using basalt fibers in terms of environmental impact. In order to fill this gap, the present study describes, using Life Cycle Assessment, the environmental impacts associated with the production of basalt fibers. In order provide a more reliable and coherent overview, an analysis combining functional and environmental indicators was performed. The presented results reveal that the use of basalt reinforcement provides a significantly lower environmental intensity per strength unit, especially in the case of compressive and flexural strength. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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27 pages, 6413 KiB

Open AccessArticle

Assessment of Passive Retrofitting Scenarios in Heritage Residential Buildings in Hot, Dry Climates

by Hanan S.S. Ibrahim, Ahmed Z. Khan, Waqas Ahmed Mahar, Shady Attia and Yehya Serag

Energies 2021, 14(11), 3359; https://doi.org/10.3390/en14113359 - 07 Jun 2021

Cited by 7 | Viewed by 3773

Abstract

Retrofitting heritage buildings for energy efficiency is not always easy where cultural values are highly concerned, which requires an integrated approach. This paper aims to assess the potential of applying passive retrofitting scenarios to enhance indoor thermal comfort of heritage buildings in North [...] Read more.

Retrofitting heritage buildings for energy efficiency is not always easy where cultural values are highly concerned, which requires an integrated approach. This paper aims to assess the potential of applying passive retrofitting scenarios to enhance indoor thermal comfort of heritage buildings in North Africa, as a hot climate, a little attention has been paid to retrofit built heritage in that climate. A mixed-mode ventilation residential building in Cairo, Egypt, was selected as a case study. The study combines field measurements and observations with energy simulations. A simulation model was created and calibrated on the basis of monitored data in the reference building, and the thermal comfort range was evaluated. Sets of passive retrofitting scenarios were proposed. The results (based on the ASHRAE-55-2020 adaptive comfort model at 90% acceptability limits) showed that the annual thermal comfort in the reference building is very low, i.e., 31.4%. The application of hybrid passive retrofitting scenarios significantly impacts indoor thermal comfort in the reference building, where annual comfort hours of up to 66% can be achieved. The originality of this work lies in identifying the most effective energy measures to improve indoor thermal comfort that are optimal from a conservation point of view. The findings contribute to set a comprehensive retrofitting tool that avoids potential risks for the conservation of residential heritage buildings in hot climates. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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18 pages, 1199 KiB

Open AccessArticle

Economic and Energy Analysis of Building Retrofitting Using Internal Insulations

by Małgorzata Basińska, Dobrosława Kaczorek and Halina Koczyk

Energies 2021, 14(9), 2446; https://doi.org/10.3390/en14092446 - 25 Apr 2021

Cited by 15 | Viewed by 2183

Abstract

The energy-saving requirements for most buildings focus on improving the insulation and airtightness of a building’s envelope. In this paper, the authors have investigated the effect of additional internal insulation on energy consumption for heating and cooling in a residential building. Energy performance [...] Read more.

The energy-saving requirements for most buildings focus on improving the insulation and airtightness of a building’s envelope. In this paper, the authors have investigated the effect of additional internal insulation on energy consumption for heating and cooling in a residential building. Energy performance analyses were conducted for buildings with four internal thermal insulation systems in three locations using the WUFI Plus software. The Global Cost Method and Simply Pay Back Time have been used to assess and compare the economic viability of the retrofit systems. The results show that, in relation to energy, retrofitting with internal wall insulation can be an alternative to traditional external insulation. The assessment of internal insulation for low-energy buildings, however, cannot be conducted based on economic criteria. The usual approach of Simply Pay Back Time has exceptionally long payback time, which is unacceptable. In turn, the Global Cost Method, can only be used to compare the applied materials. With high investment costs, thermo-modernization improvements do not contribute to significant savings. The conditions of thermal comfort and the analysis of temperature and steam pressure play a decisive role in assessing this type of solution. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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19 pages, 5591 KiB

Open AccessArticle

Improving the Energy Performance of Public Buildings Equipped with Individual Gas Boilers Due to Thermal Retrofitting

by Anna Życzyńska, Dariusz Majerek, Zbigniew Suchorab, Agnieszka Żelazna, Václav Kočí and Robert Černý

Energies 2021, 14(6), 1565; https://doi.org/10.3390/en14061565 - 12 Mar 2021

Cited by 6 | Viewed by 1431

Abstract

The article assesses an impact of thermal retrofitting on an improvement of the energy quality of public buildings in terms of their heating. The analysis covered a group of 14 buildings, including schools, kindergartens or offices, while energy audits were carried out for [...] Read more.

The article assesses an impact of thermal retrofitting on an improvement of the energy quality of public buildings in terms of their heating. The analysis covered a group of 14 buildings, including schools, kindergartens or offices, while energy audits were carried out for 12 of them. The indications of individual gas meters were the source of actual data for the assessment of changes in energy consumption indexes in operating conditions. The analysis showed a clear improvement in the energy quality of buildings; however, the actual effects were much lower than forecasted. The average forecasted decrease in energy consumption was supposed to be 64.3%, but the measured data showed only 37.1%. The investigation confirmed that the most complex refurbishing provided the most satisfactory decrease in energy consumption (51.4% of real decrease in energy consumption), while objects with partial thermal refurbishing reached an efficiency of only 21.8%. It was stated that in operating conditions, special attention should be paid to the manner of energy use, since different indicators of energy consumption can be obtained with the same parameters of building’s balance cover. The results obtained can be further utilized in thermal-refurbishment implementation procedures. Follow-up investigations on the impact of selected parameters on energy consumption are planned. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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25 pages, 13717 KiB

Open AccessArticle

Evaluation of the Summer Overheating Phenomenon in Reinforced Concrete and Cross Laminated Timber Residential Buildings in the Cold and Severe Cold Regions of China

by Haibo Guo, Lu Huang, Wenjie Song, Xinyue Wang, Hongnan Wang and Xinning Zhao

Energies 2020, 13(23), 6305; https://doi.org/10.3390/en13236305 - 29 Nov 2020

Cited by 11 | Viewed by 1915

Abstract

As the climate changed in recent years, an increase in summer indoor temperatures in severe cold and cold regions of China has started to affect thermal comfort. However, the local design standard for energy efficiency does not recognize this phenomenon. This paper reports [...] Read more.

As the climate changed in recent years, an increase in summer indoor temperatures in severe cold and cold regions of China has started to affect thermal comfort. However, the local design standard for energy efficiency does not recognize this phenomenon. This paper reports the potential overheating phenomenon in residential buildings and examines the rationale for the current thermal designs adopted in severe cold and cold regions of China. In this study, the two most commonly used building materials, reinforced concrete (RC) and cross laminated timber (CLT), are used separately in the design of an 18-story residential building envelope located in six different cities in the severe cold and cold regions. The energy consumption and indoor operative temperatures during the operation of these buildings are simulated using Integrated Environmental Solutions Virtual Environment (IES VE). The results demonstrate that both the RC and the CLT buildings experience varying degrees of overheating in any climate subregion. The CLT buildings have longer overheating hours compared to the RC buildings, especially in the cold regions. The results also indicate that for apartments on higher stories, the cooling energy consumption and indoor temperature also increase gradually. The research results suggest that the local design standard for energy efficiency needs to be adjusted by adding thermal design methods for summer to reduce the periods of overheating. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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15 pages, 3774 KiB

Open AccessArticle

Heat Transfer Analysis of Timber Windows with Different Wood Species and Anatomical Direction

by Namhyuck Ahn and Sanghoon Park

Energies 2020, 13(22), 6050; https://doi.org/10.3390/en13226050 - 19 Nov 2020

Cited by 4 | Viewed by 3042

Abstract

When assessing the hygrothermal performance of timber windows, it is important to apply the unique thermal conductivity of wood by each wood species as well as an anatomical direction within the same material as they affect the performance and long-term durability of products. [...] Read more.

When assessing the hygrothermal performance of timber windows, it is important to apply the unique thermal conductivity of wood by each wood species as well as an anatomical direction within the same material as they affect the performance and long-term durability of products. A series of heat transfer analyses of window frames using THERM and WINDOW along with measurements on the thermal conductivity of five hardwoods using laser flash apparatus (LFA) was performed to compare and evaluate heat transmittance (U-value) and condensation resistance (CR) of three types of timber and hybrid timber windows. For each window type, 6.1 to 10.3% of the maximum difference in the heat transmittance among cases was calculated. Besides, a linear correlation was found between the U-value and the CR for most cases; thus, the selection of wood species and anatomical direction would improve the hygrothermal performance of timber windows overall. The results also indicated that there were some cases where the overall CR of windows did not improve because the U-value of the glazing system was not sufficiently low. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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20 pages, 9013 KiB

Open AccessArticle

A Study on Axial Compression Performance of Concrete-Filled Steel-Tubular Shear Wall with a Multi-Cavity T-Shaped Cross-Section

by Hao Sun, Qingyuan Xu, Pengfei Yan, Jianguang Yin and Ping Lou

Energies 2020, 13(18), 4831; https://doi.org/10.3390/en13184831 - 16 Sep 2020

Cited by 9 | Viewed by 1740

Abstract

In order to study the axial compression performance of the T-shaped multi-cavity concrete-filled steel tube shear wall, first, three specimens were designed to perform the axial compression test. Then three-dimensional finite element analysis by the ABAQUS software was used to obtain the axial [...] Read more.

In order to study the axial compression performance of the T-shaped multi-cavity concrete-filled steel tube shear wall, first, three specimens were designed to perform the axial compression test. Then three-dimensional finite element analysis by the ABAQUS software was used to obtain the axial bearing capacity of the shear wall with different parameters. According to the results of the finite element model, the computational diagram in the limit state was obtained. The diagram was simplified into the core concrete in the non-enhanced area that was not constrained by the steel tube and the core concrete in the enhanced area that was uniformly constrained by the steel tube. Finally, a new practical equation for calculating the axial bearing capacity of a multi-cavity concrete-filled steel tubular shear wall was deduced and proposed based on the theory of ultimate equilibrium. The calculation results of the proposed equation were in good agreement with the finite element results, and the proposed equation can be used in practical engineering design. Full article

(This article belongs to the Special Issue Experimental and Computational Assessment of Building Envelopes, Materials and Components)

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