Large Amount Of CO2 Emissions Research Articles

Synergistic Electrocatalytic Syngas Production from Carbon Dioxide by Bi‐Metallic Atomically Dispersed Catalysts

AbstractThe production of syngas by traditional processes such as steam methane reforming is energetically intensive and produces a large amount of CO2 emissions. In contrast, the electrochemical CO2 reduction reaction (CO2RR) enables the carbon neutral production of syngas at ambient conditions. Among non‐precious metal catalysts, metal‐nitrogen‐carbon electrocatalysts are inexpensive and highly selective towards syngas production. This study examined the selectivity of mono‐ and bi‐metallic (M−N−C, M=Fe, Mo or FeMo) electrocatalysts towards syngas production. The ratio of the CO : H2 in the syngas was tuned by modifying the ratio of the metallic precursors in the bi‐metallic FeMo−N−C catalysts, tailoring the catalysts’ selectivity towards the CO2RR or the hydrogen evolution reaction (HER). The catalyst synthesis temperature(s) were considered as they influence the catalyst morphology and activity. Further, the dependence of the ratio of CO : H2 in the syngas as a function of the potential was explored for the different bi‐metallic catalysts. This work showed that by tailoring both the ratio of Fe : Mo in the bi‐metallic catalyst and optimizing the reductive potential, a CO : H2 ratio between 0.25 to 5 was achievable. This study demonstrated a novel approach in which the ratio of the product syngas composition could be tailored in a single reaction, without the need for further downstream processing to reach a desired composition.

Techno-economic evaluation of post-combustion carbon capture based on chemical absorption for the thermal cracking furnace in ethylene manufacturing

As the core unit of an ethylene production plant, thermal cracking furnace generates a large amount of CO2 emissions. To reduce the CO2 emissions, post-combustion carbon capture based on chemical absorption using monoethanolamine (MEA) solvent is used to capture CO2 from the thermal cracking furnace. The computational fluid dynamics (CFD) method was used to simulate the operation of a 60kt/a thermal cracking furnace to obtain the flow rate and composition of the flue gas. A carbon capture plant model was developed using Aspen Plus® and validated using the pilot plant test data from Technology Centre Mongstad (TCM) in Norway. Scale-up of the capture plant model was carried out to match the flue gas flow rate of the thermal cracking furnace. Two integration cases of the carbon capture plant and the industrial thermal cracking unit were carried out. The results show that the excess heat of the gasoline fractionator can be used to provide heat for the carbon capture plant without affecting ethylene production. The economic evaluation was conducted based on the two case studies. Results show that the cost of CO2 capture can be reduced from $80.03/tonne (without heat integration) to $70.41/tonne with heat integration. When considering the impact of carbon credits on capture costs, the cost will be further reduced to $50.41/tonne.

Research progress on the influence of geopolymer grouting material properties

Grouting technology is to inject slurry with cementing ability into the cracks and voids of the formation to achieve the purpose of reinforcement and filling. At present, cement-based materials are mainly used for grouting, which has the advantages of mature technology, cheap price, high stone strength and wide application, but there are also defects such as high-water separation rate, poor stability and long setting time. Most importantly, the production of cement materials consumes a lot of energy and emits a lot of CO2, which aggravates the global greenhouse effect and is not in line with the concept of sustainable development. In recent years, geopolymer materials based on volcanic ash and industrial waste residue have attracted extensive attention of scholars because of their green and environmental characteristics, and have been gradually applied in the field of grouting. Geopolymer is a new inorganic cementitious material formed by leaching the active components (Si, Al, and other elements) from industrial wastes such as fly ash, slag, and steel slag using chemical alkali activation technology (AAT) and further recombination. Using geopolymer as grouting material has two advantages :(1) geopolymer has a wide source of raw materials and low cost, which can effectively reduce the cost of grouting engineering; (2) Compared with cement materials, geopolymer materials have the advantages of low energy consumption, green environmental protection and other advantages, which can realize the effective recovery and reuse of industrial waste residue, reduce a large amount of CO2 emissions, and have far-reaching environmental and social benefits. Among them, temperature is an important factor affecting the properties of geopolymer grouting cementitious materials. In this paper, the effects of the selection of aluminosilicate raw materials, the fineness of raw materials, the ratio of liquid to solid, the type and modulus of alkali activator, and the temperature conditions on the properties of geopolymer grouting cementitious materials are comprehensively combed.

Estimation of CO2 Emissions Embodied in Domestic Trade and Their Influencing Factors in Japan

CO2 emissions embodied in domestic trade between Japanese prefectures are gradually increasing and becoming an important growth point in the country’s CO2 emissions. The primary objective of this study is to evaluate the CO2 emissions embodied in Japan’s domestic imports and exports to visualize the carbon transfer paths between prefectures according to the attributes of production and consumption: also to identify the influencing factors of the carbon flow. This study estimated the CO2 emissions embodied in domestic imports and exports by prefectures using input–output analysis, followed by the log-mean Divisia index decomposition approach, which is used to quantify the influencing factor of net export CO2 emissions across prefectures. The results show substantial regional differences in the CO2 emissions embodied in domestic imports and exports across prefectures. Manufacturing prefectures satisfy most of Japan’s domestic demand for industrial products and are the main net exporters of CO2 emissions. Carbon flow is more obvious in economically advanced regions (such as the Kanto and Kansai regions) and covers more prefectures through carbon transfer. Consumer prefectures import the most CO2 emissions and export large amounts of CO2 emissions to other prefectures. Among the three factors influencing net export CO2 emissions, the technology effect has the most significant impact through the carbon intensity of domestic trade flows. These findings highlight the substantial differences in CO2 emissions embodied in domestic trade and the influencing factors across prefectures in Japan. The responsibility for emission reduction is attributable to both manufacturing and consumer prefectures.

Peaking Industrial CO2 Emission in a Typical Heavy Industrial Region: From Multi-Industry and Multi-Energy Type Perspectives.

Peaking industrial carbon dioxide (CO2) emissions is critical for China to achieve its CO2 peaking target by 2030 since industrial sector is a major contributor to CO2 emissions. Heavy industrial regions consume plenty of fossil fuels and emit a large amount of CO2 emissions, which also have huge CO2 emissions reduction potential. It is significant to accurately forecast CO2 emission peak of industrial sector in heavy industrial regions from multi-industry and multi-energy type perspectives. This study incorporates 41 industries and 16 types of energy into the Long-Range Energy Alternatives Planning System (LEAP) model to predict the CO2 emission peak of the industrial sector in Jilin Province, a typical heavy industrial region. Four scenarios including business-as-usual scenario (BAU), energy-saving scenario (ESS), energy-saving and low-carbon scenario (ELS) and low-carbon scenario (LCS) are set for simulating the future CO2 emission trends during 2018–2050. The method of variable control is utilized to explore the degree and the direction of influencing factors of CO2 emission in four scenarios. The results indicate that the peak value of CO2 emission in the four scenarios are 165.65 million tons (Mt), 156.80 Mt, 128.16 Mt, and 114.17 Mt in 2040, 2040, 2030 and 2020, respectively. Taking ELS as an example, the larger energy-intensive industries such as ferrous metal smelting will peak CO2 emission in 2025, and low energy industries such as automobile manufacturing will continue to develop rapidly. The influence degree of the four factors is as follows: industrial added value (1.27) > industrial structure (1.19) > energy intensity of each industry (1.12) > energy consumption types of each industry (1.02). Among the four factors, industrial value added is a positive factor for CO2 emission, and the rest are inhibitory ones. The study provides a reference for developing industrial CO2 emission reduction policies from multi-industry and multi-energy type perspectives in heavy industrial regions of developing countries.

Challenges in reaching positive energy building level in apartment buildings in the Nordic climate: A techno-economic analysis

Buildings consume significant amount of final energy and they emit large amount of CO2 emissions. To address this issue, nearly zero energy buildings is becoming a common in many countries, while research is advancing towards the positive energy building (PEB) target by utilizing renewable energy that can support reducing the emissions from the building stock. The aim of this study, is to design and model a renewable-based energy system for a real demo apartment building in Nordics (Finland) in order to be a PEB, by exceeding the building’s heating, cooling and plug load demands. The novelty of this study is to assesses the fulfillment of the PEB level in cold climate, by simulating various technologies (such as photovoltaic-thermal (PVT) system, heat pump (HP), wind turbines, seasonal thermal energy storage etc.) their integration with the building, its controls strategies, types of load included in the energy balance and definition of building boundaries across which the balance is calculated. TRNSYS simulation software is mainly used for dynamic simulation of the energy system. The electricity import and export, the life cycle cost (LCC), and the onsite energy matching factors are calculated to estimate the performance of the proposed system. In addition, the challenges related to the building’s limited physical boundary are discussed. The results of this study shows that, if all the demands are included, i.e. heating, cooling and plug loads, then it is difficult to reach the PEB level. In this case, the investment cost in the energy system is around 47–62% of the LCC and the rest is the operational cost. On the other hand, the PEB level is relatively easier to achieve if the plug loads are excluded, then the investment cost is around 88–100% of the LCC and there can be positive cash flow due to larger energy export than import. The PEB level is possible to be achieved when all the demands are included if the building boundary is extended to a virtual boundary outside its physical boundary that allows the addition of more renewable generations or by changing the building’s shape that allows the more installations of renewables on the roof. In this scenario, the investment cost on the energy system is around 62–91% of the LCC. Compared to the building cost, the energy system cost is generally low, i.e. around 1.2–4.3% of the building cost.. It can be concluded that in the Nordic conditions, it is difficult to reach the PEB level for the buildings in urban areas if the all the building’s energy demands are included. Renewable energy generations, such as additional PVT and wind turbines, are needed to be installed in an extended (virtual) boundary of the building if the PEB criterion has to be met when considering all the energy demands. Investment cost of the renewable energy system is low compared to the building’s cost, therefore, such renewable-based solutions can be provided with small additional cost, along with the new building’s cost, so that PEB and carbon neutrality targets can be achieved.

A Critical Review on Decarbonizing Heating in China: Pathway Exploration for Technology with Multi-Sector Applications

Coal-fired heating is the main method of heating in China, causing serious air pollution and large amounts of CO2 emissions. Decarbonizing heating is important to reduce carbon emissions, and choosing a suitable heating technical scheme is conducive to the early realization of carbon neutrality in China. Coal to gas and coal to electricity transformation projects were carried out in 2017 and achieved remarkable effects. This study compares the current domestic and international clean heating modes, where gas heating, electric heating, heat hump heating, biomass heating, and solar heating coupling system are taken into account. The heating technology potential and heating support aspects, including the industrial sector, building sector, carbon capture and storage (CCS) technology, and publicity are explored as well. Regarding the actual situation in China, a comparative analysis is also conducted on the different types of heat pumps, and then an optimal heating scheme for urban and rural areas is proposed. It is suggested that the urban area with centralized heating can install ground source heat pumps, and the rural area with distributed heating can apply a coupling system of solar photovoltaics to ground source heat pumps (PV-GSHP). Based on current policies and standards support, this study calculates the carbon emissions of this scheme in 2030 and provides a detailed analysis of relevant parameters. The feasibility and superiority of the scheme are confirmed by comparison and discussion with other studies. Moreover, specific measures in planning, subsidy, construction, and electricity are proposed to implement the heating scheme. This study provides a reference for the mode selection and technical scheme of heating decarbonation in China, and that could be also considered in other regions or countries.

AN ANALYSIS OF LOW CARBON ENERGY ASSESSORS (LCEA) IN PUBLIC BUILDINGS

World has been shifting towards cleaner and safer sources of energy. Reducing the carbon footprint is the need of the hour. Industries all over the globe are researching on reducing the pollution causing emissions and trying to improve in terms of using sustainable sources of energy and saving the environment. This paper would analyse the low carbon energy assessors (LCEA) in the construction industry. A detailed study has been conducted using primary and secondary research to determine the carbon emissions at different stages of construction. The study would help us in identifying the main phases and activities and components, contributing the majority of the carbon footprints. The need of this age is to work on this area and minimise the pollution and harm to the environment. The construction sites chosen are diverse and consist of all types of building in the southern part of India. The highest carbon emission component in building construction is the cement as a large amount of CO2 emission takes place during the manufacturing process of the cement. The minimum carbon emission that takes place due to the components from the building are labour, sand, MS steel and stainless steel. The study would give a high level idea about the impact of low carbon energy assessors (LCEA) in the construction industry.

Applicability of CO2-related concentration indicators by classifying various seawaters in the world

Carbon dioxide capture and storage is expected to reduce large amount of CO2 emissions from large sources, such as coal power plants. For offshore CO2 storage, it is necessary to monitor CO2 concentration in seawater to ensure safe storage. However, such concentrations have large regional and seasonal variations due to biological activity. In our previous study, to avoid the misidentification of large natural fluctuations as abnormally high CO2 concentrations (false positive), a method was proposed using multiple indicators of CO2-related concentration in seawater: namely, anomalies are judged only if there are data that exceed statistical criteria, e.g. 3-sigma, of all the multiple correlations of different types. This is because any single indicator can have data exceeding such criteria in theory. In this study, we examined the universality of applying multiple indicators of different types to seawaters around the world. The results show that the world seawaters can be classified into three groups using the relationships between alkalinity and salinity and the vertical profiles of dissolved oxygen, and that at least one of the four indicators has a clear correlation in each group, suggesting that the applicability of the proposed method using multiple indicators has been proved.

The climate economic effect of technology spillover

There is increasing interest in the global CO2 emissions transfer caused by international trade. However, the reduction potential of technology spillover is rarely considered. More importantly, the effect of technology spillover on climate change and the social cost of carbon (SCC) should be further investigated to inform climate policy-makers. In this study, we investigate the climate economic impact of technology spillover through unidirectional coupling of the emissions embodied in bilateral trade (EEBT) method and the dynamic integrated model of climate and economy (DICE). The results indicate that technological progress in the electricity sector could contribute to climate change mitigation and SCC lowering. The trade-related CO2 emissions of key CO2 exporters could be substantially reduced, such as China, India, Russia, and resource- and labor-intensive countries. High-tech countries outsourced large amounts of CO2 emissions to labor- and resource-intensive countries. However, a large income gap remains between high-tech and labor/resource-intensive countries. These results indicate the great importance of technological progress and sustainable management throughout the global supply chain.

Aging of recycled aggregates mortars by drying-wetting cycles

Due to the large amount of CO2 emissions produced nowadays by the construction sector, the scientific community is looking for measures that will bring constructions to the be as environmental-friendly as possible. One of the most popular lines of research is the use of construction waste as recycled aggregates for the production of recycled aggregates concrete. Regarding the use of coarse recycled aggregates, there are a large number of studies that validate their use at both a mechanical and durability levels. Regarding the use of fine particles, which are inherent to the existence of coarse particles, it is necessary to increase the existing knowledge before they can be widely used. In this paper, the authors have sought to isolate the weakest part of those concrete mixes with exclusively recycled aggregate, i.e. a mortar made exclusively with fine recycled aggregates, in order to analyse the effect of drying-wetting cycles on mixes with recycled aggregates only. Specifically, three types of fine aggregates were used, one natural silica aggregate, one aggregate from crushed ballast and one from crushed sleepers. The mortars made with these aggregates were subjected to 50 durability cycles in distilled water, seawater and water with sulphates. Mechanical, visual and microstructural tests were carried out to analyse the effect of each of these environments on each of the mortars.

Advanced Exergy Analysis of an Acid Gas Removal Plant to Explore Operation Improvement Potential toward Cleaner Production

This research aims to conduct an integrated energy and exergy evaluation of an acid gas recovery (AGR) plant. An effective simulation platform is developed and linked to a thermodynamic modeling approach. A newly developed amine blend, composed of methyl-di-ethanolamine (MDEA), di-ethanolamine (DEA), and piperazine (PZ), is utilized to absorb the acid gases. Based on the classical energy analysis, an energy loss of 70.79 MW and an energy efficiency of 90.29% are attained for each process component. Conventional exergy analysis is then conducted, and the sources of irreversibility are identified. The postprocessing is performed on the conventional exergy evaluation results using an advanced exergy method, to obtain a more realistic insight into the system’s energy/exergy performance. It is concluded that stripper and absorber account for the maximum exergy destructions of 8.15 and 7.55 MW, respectively; this shows significant potential for operation improvement in these two key equipment. Also, it is concluded that 5.47 and 4.92 MW unavoidable exergy destructions occur in the stripper and absorber, respectively, which cannot be prevented. It is found from the advanced exergy analysis that the absorber, stripper, and heat exchanger with the greatest recoverable exergy amount (e.g., exergy rehabilitation ratio) exhibit substantial operation enhancement capability in comparison to the other process equipment. The overall exergy efficiency of the entire system is enhanced from 99.70 to 99.90%, when the technological constraints are abolished and the ideal condition governs. The results of avoidable/endogenous exergy destruction reveal high potential of the absorber (2.58 MW), stripper (2.18 MW), heat exchanger (0.74 MW), and valve (0.19 MW) in terms of operation improvement compared to the other process components. Based on the environmental analysis, a large amount of CO2 emission (22.12 ton·day–1) can be prevented, when the process components are technologically upgraded.

Current development of geopolymer cement with nanosilica and cellulose nanocrystals

The cement industry has contributed large amounts of CO2 emissions and is responsible for the consumption of non-renewable natural resources. Geopolymer based cement has emerged as an environmentally friendly alternative to construction materials because it can be produced from industrial waste. Similar to ordinary portland cement, geopolymer cement can be strengthened with nanomaterials. This paper presents a review of nanosilica and cellulose nanocrystals in geopolymer cement. The addition of nanosilica can improve the properties of pozolan which is able to bind calcium-hydroxide so that the resistance to sulfate corrosion will also be better and nanosilica can also increase chemical reactions due to its surface area. Nano-sized cellulose-based particles can fill the smallest gaps in cement paste that cannot be treated by other micro or macro sized materials. This paper also presents an overview of the latest advances in the production of geopolymer cement that reinforced by nanosilica and cellulose nanocrystals as promising sustainable construction materials.

Construction of a Z-scheme heterojunction for high-efficiency visible-light-driven photocatalytic CO2 reduction.

The continuous growth of fossil fuel consumption and large amounts of CO2 emissions have caused global energy crisis and climate change. The employment of semiconductor photocatalysts to convert CO2 into value-added products has attracted extensive attention and research worldwide in recent years. However, it is difficult for a single-component semiconductor photocatalyst to achieve this goal efficiently due to its drawbacks, such as low quantum efficiency, limited surface area, limited number of active sites, the short lifetime of photogenerated carriers, poor long-term stability, and the weak redox ability of carriers. Fortunately, inspired by photosynthesis, the construction of an artificial Z-scheme heterojunction has brought a new dawn for the realization of this goal. The Z-scheme heterojunction has a high separation efficiency of electron-hole pairs with strong redox ability and a wide light response range. The abovementioned advantages make the Z-scheme heterojunction provide a great opportunity for the conversion of CO2 to value-added chemicals. This review concisely reports the progress of the Z-scheme heterojunction in the field of photocatalytic CO2 reduction in recent years, photocatalytic mechanism, choice of oxidation and reduction systems, strategies for improving efficiency, confirmation of the Z-scheme charge transport mechanism, problems and challenges, and the prospects for the future.

Sector-level evaluation of China’s CO2 emissions: Trend evolution and index ranking

In China’s low-carbon development progress, industrial sectors play a crucial role in reducing CO2 emissions and maintaining economic growth targets. Because the Chinese government is promoting industrial structure transformation for “high-quality economic development,” the dominant CO2 emitters have changed in recent years. It is important to identify the trend evolution of industrial CO2 emitters and implement targeted measures and policies for CO2 emission control at the sector level. In this paper, a hybrid input–output model is adopted to assess the situation and trend of sectoral CO2 emissions from 2002 to 2017 in China. Demand-side drivers of sectorial embodied CO2 emissions are discussed. Based on the embodied CO2 emission decomposition of 27 sectors, a CO2 emission evaluation index is defined for CO2 emission ranking and key sectors for embodied CO2 emissions are identified. For the key CO2 emitters, we provide targeted policy suggestions for CO2 emission mitigation from the perspective of trend evolution and index ranking.The results indicate the following. (1) 2015 is a turning point for China’s CO2 emission mitigation progress, because the previously increasing embodied CO2 begins to decrease from 2015 to 2017. (2) Although the Construction sector stimulates a large amount of CO2 emissions at present, the major driving forces of CO2 emissions have gradually changed from infrastructure construction to the increasing demand of consumer goods, service industry, and export of technology-intensive products. (3) The CO2 emission intensity of the Electric Power and Heat Supply sector has increased, and promotion of renewable energy consumption is urgently needed. (4) From the demand-driven aspect, tertiary industry has greater CO2 emission potential than heavy industry.

Multi-objective optimization of post combustion CO2 capture using methyldiethanolamine (MDEA) and piperazine (PZ) bi-solvent

Global warming is becoming a critical issue in 21st century which is mainly due to the growing rate of greenhouse gas emissions. This is mostly due to the large amount of CO2 emission from power generation activity using fossil fuels. One of the main methods of fighting global warming and reducing CO2 emission into atmosphere is to perform carbon capture, sequestration and utilization. Carbon capture can be performed through different ways, in which post combustion CO2 capture (PCC) has been developed and both economic and technically wise is in state of art. One of the disadvantages of PCC is its high efficiency penalty due to energy consumption in the reboiler for solvent regeneration. Many efforts have been done to reduce the consumption of energy in the reboiler via different strategies including process parameters optimization, solvent development and novel process configuration. This investigation used different blends of PZ and MDEA as solvent and process parameters optimization via evolutionary algorithm and multi-objective optimization. The optimization was performed on a conventional process flow diagram. CO2 capture efficiency and reboiler heat duty were used as the objective functions and main decision variables are solvent flowrate and MDEA/PZ concentration. Flue gas CO2 capture of 90, 91, 92, 93, and 94% corresponded to regeneration energy consumption of 2.68, 2.71, 2.72, 2.75, and 2.76 Eregen/tCO2; respectively. These optimized values showed a higher energy efficiency compared to MEA and MDEA/PZ in conventional process configuration.

Comparison and suggestion of indicators of concentrations associated with CO2 in seawater considering biological activity

Carbon dioxide capture and storage is expected to reduce large amount of CO2 emissions from pointwise large sources, such as coal power plants, by 2030 in Japan. For offshore CO2 storage, it is necessary to monitor concentrations associated with CO2 in seawater to ensure safe storage. To do so, it is also necessary to know the baseline concentrations in the target seas. However, such concentrations have large regional and seasonal variations, mainly because of biological activity. In this study, we compared various indicators of CO2 dissolved in seawater, using the seawater off Tomakomai, Japan, observed between 2013 and 2018. Among the indicators, we found very strong correlations between [nDIC + kDO] and T and between [DIC − 0.5TA + kDO] and T. These indicators are thought to be effective for investigating the possibility of unexpected leakage of CO2 stored in sub-seabed geological formations. However, data always contain a degree of scattering, even when their correlation is very high. In the case of the seawater off Tomakomai, the data that exceeded a criteria based on the residual standard deviation of some indicators were not necessarily the same as those of the other indicators. Therefore, it is suggested that two or more, different types of indicators should be used, such as pCO2-[DO saturation] and [nDIC + kDO]-T or [DIC − 0.5TA + kDO]-T.

Characterization and reduction behavior of carbon-infiltrated goethite ore by impregnation of tar recovered from coke oven gas

The Iron/Steel industry is currently facing serious problem due to excessively dependent on metallurgical coke, which is produced a large amount of CO2 emission and it was limited source in Indonesia. Coke-free iron-making is one of the efficient method to reduce the amount of cokes. Carbon-infiltrated iron ores were prepared by impregnation process from coaltar solution and goethite ore at 500 °C and 600 °C to promote direct reduction in iron making. These variables were systematically characterized by XRD and SEM/EDX. Pore distribution and BET surface area were determined by N2 adsorption-desorption measurement. The XRD signals attributed to Fe2O3 in the goethite ore were completely disappeared and replaced by signals attributed to Fe3O4 after impregnation process. Cross-sectional analyses of composite particles prepared using both temperatures showed that tar-derived carbonaceous materials have completely either impregnated or vapor infiltrated into the mesoporous in pyrolyzed goethite ore. Carbon-infiltrated goethite ore showed a higher reduction degree than conventional coke. It is confirmed that high reactivity of carbon-infiltrated iron ores is due to close contact between the goethite ore and carbon in its nanoporous interior facilitated the fast reduction.

Building integrated renewable energy

About one-third of the primary energy in the world is consumed by buildings. A large amount of CO2 emission due to building energy consumption has threatened the sustainable development of the world. Improvement on the building energy performance, especially by integration with renewable energy resources has attracted interest worldwide to reduce greenhouse gas emission to make our society more sustainable. This Special Issue on building integrated renewable energy was open to all contributors in the field of building energy efficiency. The original experimental studies, numerical simulations, and reviews in all aspects of renewable energy utilization, management, and optimization have been considered. In the event, all these topics were covered in the extensive submissions accepted, but interesting papers on other aspects of building energy efficiency were also received. The purpose of this editorial is to summarize the main research findings of accepted papers in this Special Issue, including the use of renewable energy and energy saving technologies in buildings and identify a number of research questions and research directions.

Influence of carbon steel fibers on the flexural crack width of RC beam

Reinforced concrete beams are the significant structural elements in the structure. They improve resistivity against flexural loads. The concrete portion in the reinforced concrete beam is good in compression but at the time of bending reinforcement will take about the structural element. When the flexural stresses exceed the flexural capacity of the reinforced concrete beam cracks will occur at the flexural portion. In this investigation for avoiding and delaying flexural cracks, carbon steel fibres are incorporated into the concrete mix. The carbon steel fibres are added in concrete concerning the total volume of concrete. Different percentages like 0.5%, 1%, 1.5% and 2% of carbon steel fibres are added to the conventional concrete. Another side large amount of CO2 emission occurs while manufacturing the cement in the industry. Because of that the cement content is replaced 30% with GGBS (Ground Granulated Blast Furnace Slag). The mix design used in this investigation is M30 with a water-cement ratio of 0.4. Cubes, cylinders and RC beams of 1.5 m X 0.23 m X 0.23 m are cast and placed in curing for 7 days and 28 days respectively. In this investigation single crack and multiple crack behaviour is analysed. The compression and split tensile strength of concrete are enhanced by incorporating carbon steel fibres in the conventional concrete. The RC beams with 28 days effective curing were tested under the loading frame of 2000T capacity. The result shows the initial crack propagation time is increased by increasing fibres content because at the time of crack propagation fibers present in the concrete mix will resist the entry of crack in the concrete and crack width is reduced by increasing fibres content compared with conventional concrete.