Operational Carbon Emissions Research Articles

Parametric BIM-Based Lifecycle Performance Prediction and Optimisation for Residential Buildings Using Alternative Materials and Designs

Residential building construction is resource-intensive and significantly impacts the environment by embodied and operational carbon emissions. This study has adopted a parametric building information modelling (BIM)-based approach for a residential building to analyse its lifecycle carbon performance and to evaluate the optimisation potential through alternative material use and design. The study looks at a residential development project, applying an automatic calculation and analysis tool of upfront embodied carbon and BIM-based lifecycle energy simulation to predict carbon emissions from operating the built spaces. A parametric BIM model has been established to aid energy simulation and operational carbon assessment across a 50-year building lifetime, considering 1.5 °C Net-Zero World and 3 °C Hot House World climate scenarios. Various improvement opportunities for future residential development projects, from material selection to operational efficiencies, are explored. This includes quantitative analysis on architectural-structure design, low-carbon construction materials (e.g., cement substitutes, steel scraps, and green hydrogen steel), and novel design for construction approaches (such as modular integrated construction), with discussion around their impacts on optimising the building lifecycle carbon performance. This study provides a deeper understanding and insights into the lifecycle performance of residential buildings to facilitate further exploration of achieving a more sustainable and low-carbon built environment.

Carbon assessment of building shell options for eco self-build community housing through the integration of building energy modelling and life cycle analysis tools

To achieve the UK's net-zero carbon transition by 2050, new homes need to be designed to high energy efficiency standards and minimise life cycle carbon emissions. This study develops a method that integrates building energy modelling (BEM) and life cycle assessment (LCA) tools, IES Virtual Environment (IES VE) and One Click LCA, to conduct a life cycle assessment of the operational and embodied carbon impacts of a typical terraced building shell in an eco self-build community housing (ESBC) project, using Water Lilies as a case study. It evaluates and compares the 60-year life cycle carbon impacts of six design options that apply different insulation materials to the case study building shell. The results are based on grid-connected Future Energy Scenarios (FES) that have different carbon intensities predicted over time and the microgrid-connected Water Lilies Community Energy (WLCE) scenario that is operationally net-zero carbon. Depending on the FES, embodied carbon accounted between 59 and 80% of total emissions compared to 20–41% from operational carbon across design options. The results show that operational carbon is highly sensitive to the percentage of renewables in the energy mix of the grid, which is difficult to predict, and can significantly influence the design choice. As such, future researchers should account for predicted changes to the carbon intensity of the grid by applying a similar method to that proposed. Overall, the integration of IES VE and One Click LCA provided a more streamlined life cycle assessment to help inform early design decisions by enabling energy consumption simulation in BEM to assess operational carbon emissions and the automated transfer of building materials from the BEM model to the LCA tool to assess embodied carbon emissions. The limitations included the unavailability of material-specific data in early design stage plans, the inability to automatically transfer the timber frame structure from IES VE to One Click LCA, and the uncertainty of future energy trends.

An energy performance baseline scenario for 19thC listed dwellings in the UK

PurposeThe inclusion of heritage dwellings in the UK decarbonization policies can contribute to cut operational carbon emissions from the building stock; this needs to be made a priority if net zero carbon targets are to be achieved. However, the energy and carbon savings potential of suitable retrofit interventions on this part of the stock is extremely variable and strictly intertwined with the range of baseline conditions of such dwellings. This study aims to propose a framework for interventions in traditional listed dwellings (TLDs) to improve their energy performance utilizing dynamic energy simulation (DES) of selected case studies (CSs) in the city of Brighton and Hove (South-East England).Design/methodology/approachTo achieve this aim, the study established a baseline scenario which provides a basis for the assessment of energy performance and thermo-hygrometric behaviour pre- and post-interventions and allows for comparison between different CSs under comparable conditions.FindingsPresenting a brief overview of the methodology adopted in this study, the paper describes the approach devised to generate such baseline scenario. The paper then compares the results obtained from simulation of normalized and baseline models with the status-quo energy consumption of the dwellings investigated (based on meter readings).Originality/valueThis analysis finally allows to highlight some key physical determinants of the baseline HEC which, in the following stage of research, proved to have a considerable effect also on the amount of energy and carbon savings achievable post retrofit interventions.

Carbon emissions from buildings based on a life cycle analysis: carbon reduction measures and effects of green building standards in China

Carbon emissions from buildings account for approximately half of China's total social carbon emissions. Focusing only on the carbon emissions of building operation tends to neglect the carbon emissions of other related parts of the building sector, thus slowing down the progress of carbon peaking in the building sector. By applying life-cycle analysis to calculate carbon emissions throughout the building's life cycle, the performance of carbon emissions at each stage of building materials, construction, operation and end-of-life demolition can be identified, so that carbon reduction strategies in building design can be selected.. This paper constructed a method for calculating the carbon emissions of green buildings in whole-building life cycle, and conducted a summary analysis of the carbon emissions of 33 projects that were awarded green building certification. The study found that the Chinese Assessment Standard for Green Buildings has a significant effect on reducing the carbon emissions of buildings in whole-building life cycle. Compared with the current average operational carbon emissions of buildings in China, the carbon intensity of green public buildings is 41.43% lower under this standard and the carbon intensity of green residential buildings is 13.99% lower. A carbon correlation analysis of the provisions of the current Chinese Assessment Standard for Green Buildings was conducted, comparing the changes in the carbon intensity of buildings before and after the revision of the standards. The study concluded that the new version of the standards has a greater impact on public buildings than residential buildings, the requirement of carbon emission reduction in the production stage of building materials is strengthened in terms of carbon emission during the whole-building life cycle. This study addresses the current problem of unclear carbon emission reduction effect of green buildings.

Research on the Integration of a Natural Gas-Distributed Energy System into the Oilfield Facility in China

The oilfield facility provides a sufficient supply of self-produced natural gas and has an obvious price advantage. However, China’s oilfield facilities are supplied with electricity and heat from the external grid and natural gas boilers separately. Therefore, in this study, a natural gas distributed energy saving system is built in the oilfield facility, which can supply electricity and heating simultaneously. An oilfield facility in Changchun, China, is used as the case study in this research to design a natural gas-distributed energy system. The operational carbon emissions and the operating cost are used as evaluation criteria. Three energy supply methods of the natural gas-distributed energy system are studied. Meanwhile, the impacts of China’s distributed energy policy are also quantified to determine the capacity of the power generation units. The results reveal that under the optimized following the heating load method (FHL-restricted), where the self-electricity consumption ratio of the gas engine is kept at 50%, the natural gas-distributed energy systems can meet policy requirements while achieving optimal carbon emission reductions and minimizing operating costs. The newly built system can simultaneously achieve the goals of energy saving, carbon emission reduction, and energy cost mitigation.

Kaya for Computer Architects: Toward Sustainable Computer Systems

This article reformulates the well-known Kaya identity to understand computer systems’ impact on sustainability and its total carbon footprint. By making a distinction between embodied and operational carbon emissions, we are able to understand 1) how the global carbon footprint of computing is likely to scale in the future, and 2) what we, as computer architects, can do to reduce the environmental impact of computing. We conclude that computer architects should first and foremost design smaller chips; reducing lifetime energy consumption is of secondary importance, yet still significant.

A theoretical assessment of transport emissions from institutional buildings in a Norwegian municipality

Municipalities are key actors in reaching the sustainable development goals 9, 11, 12, 13 set by the United Nations. The aim of this paper is to develop, on a theoretical level, a sustainable building refurbishment framework for municipalities. The focal point of the framework is reduction of embodied and operational carbon emissions deriving from buildings, including travel-induced emissions. The institutional buildings governed by a Norwegian municipality are the case study objects in this study. The framework that is currently is used in the municipality value the building stock based on the quality and cost of refurbishing them. No framework currently includes travel-induced emissions in the evaluation. The intention is to provide a holistic framework that includes this aspect when deciding if a building should be refurbished or demolished. The omission of transport emissions can lead to truncation errors in assessments. The transport to and from the school generates higher emissions in certain scenarios. Based on the knowledge in the assessment, a theoretical framework that assesses this is developed.

A parametric analysis of future climate change effects on the energy performance and carbon emissions of a Chinese prefabricated timber house

Prefabricated timber houses have received growing attention in China recently as being one possible approach to mitigating climate change impacts. This article presents the results from a dynamic thermal simulation parametric analysis of building characteristics and primary energy consumption, embodied and operational carbon of newly built prefabricated timber house types in northern China for current and future climates (2050 and 2080). The dynamic thermal modelling software DesignBuilder (+EnergyPlus) was adopted as the simulation package. The main findings from the study were: (i) by 2080 climate change could increase energy demand by 13% for a terraced house, by 10% for a semi-detached house, and by 6% for a detached house, with corresponding increased carbon emissions of 27%, 26% and 23% respectively; (ii) in 2080, a terraced house would achieve 74% energy demand and 90% carbon emissions of a detached house; (iii) increasing the window-to-wall ratio from 0.25 to 0.45 would lead to 31% increase in energy demand, and 42% increase in carbon emissions in 2080; (iv) adjusting the configuration of key timber structural components (walls and floors) could lead to reductions of 19% in primary energy demand, 23% in operational carbon, and 6% in embodied carbon. A terraced timber house with south-facing and a window-to-wall ratio of 0.25 would be an optimal configuration to mitigate climate change impacts in northern China. The adjustment of prefabricated timber wall structure could give rise to significant reductions in primary energy consumption, operational carbon emissions, and embodied carbon.

Integrating Reactive Chlorine Species Generation with H2 Evolution in a Multifunctional Photoelectrochemical System for Low Operational Carbon Emissions Saline Sewage Treatment.

Conventional wastewater treatment plants (WWTPs) suffer from high carbon emissions and are inefficient in removing emerging organic pollutants (EOPs). Consequently, we have developed a low operational carbon emissions multifunctional photoelectrochemical (PEC) system for saline sewage treatment to simultaneously remove organic pollutants, ammonia, and bacteria, coupled with H2 evolution. A reduced BiVO4 (r-BiVO4) photoanode with enhanced PEC properties, ascribed to constructing sufficient oxygen vacancies and V4+ species, was synthesized for the aforementioned technique. The PEC/r-BiVO4 process could treat saline sewage to meet local WWTPs' discharge standard in 40 min at 2.0 V vs Ag/AgCl and completely degrade carbamazepine (one of EOPs), coupled with 633 μmol of H2 production; 93.29% reduction in operational carbon emissions and 77.82% decrease in direct emissions were achieved by the PEC/r-BiVO4 process compared with large-scale WWTPs, attributed to the restrained generation of CH4 and N2O. The PEC system activated chloride ions in sewage to generate numerous reactive chlorine species and facilitate •OH production, promoting contaminants removal. The PEC system exhibited operational feasibility at varying pH and total suspended solids concentrations and has outstanding reusability and stability, confirming its promising practical potential. This study proposed a novel PEC reaction for reducing operational carbon emissions from saline sewage treatment.

Comparison of Green Building Rating Systems from LCA Perspective

Buildings account for a considerable proportion of carbon emissions throughout their lifecycle. Therefore, Green Building Rating Systems (GBRSs) have been developed globally to evaluate building environmental performance and mitigate their impacts on climate change. Life Cycle Assessment (LCA) as a science-based method has been recognised in the GBRSs to enhance the building environmental assessment. Regardless of the wide implementation of GBRSs, buildings carbon emissions have continued to rise by nearly 1% per year since 2010. Furthermore, no academic research has been conducted to compare GBRSs assessment criteria from the LCA perspective in respect of the recognition and weighting of (1) whole building LCA, (2) embodied carbon emissions and (3) operational carbon emissions. To this end, this research aims to evaluate the efficiency, validity and reliability of five international GBRSs (i.e., LEED, BREEAM, BEAM Plus, Green Star and Homestar) in terms of assessing and auditing the building total carbon emissions; embodied and operational emissions. Results show that conducting whole building LCA is an optional assessment criterion with negligible weighting. Moreover, the assessment of the operational carbon emissions make up the major portion of the total weighting in the existing GBRSs. By contrast, the assessment of building embodied carbon emissions is overlooked. Based on the results, shifting focus from operational carbon towards a full life cycle perspective is urgently needed to achieve the emissions reduction targets and so decarbonising the built environment.

A Holistic Framework for Determining the Trade-off between Embodied and Operational Carbon Emissions of High-rise Residential Buildings

Buildings’ carbon emissions consist of embodied carbon (EC) associated with the production and transportation of materials and operational carbon (OC) generated from consumed energy during daily use. However, previous studies concentrated on either EC or OC but ignored an integrated analysis of their relationships. Therefore, this paper aims to explore appropriate building envelope design solutions by examining the trade-off between EC and OC of high-rise residential buildings. To achieve this aim, the life cycle assessment method was used to evaluate the EC and OC of the residential buildings using SimaPro and DesignBuilder software. A building information modelling (BIM) model was developed to extract the geometric data and material consumption. A typical 30-story public residential building in Hong Kong was examined. The EC and OC of the case building were calculated as 561 kg CO2e/m2 and 50.18 kg CO2e/m2/yr, respectively. Different low carbon design scenarios were identified from the literature review and the semi-structured interviews with designers and contractors. Results indicate that low carbon concrete is an effective approach for not only reducing the EC by 5%-15%, but saving a mild percentage of OC, and is therefore encouraged. However, changing the thickness of external walls leads to a very limited life cycle carbon reduction (0.99%). Lower U-value of envelopes is recommended as 2.84% and 2.89% life cycle carbon is reduced when adopting insulations for external walls and triple-glazing windows. The findings are valuable for examining the relationships between EC and OC and can support low carbon building decision-making.

Operational carbon transition in the megalopolises’ commercial buildings

Megalopolises are important political and economic centers and offer the best opportunities for decarbonizing commercial building operations. This study estimates the decarbonization level of commercial buildings from China's five major megalopolises (Jing-Jin-Ji, Yangtze River Delta, Pearl River Delta, Yangtze River Middle Reach, and Cheng-Yu) through the generalized Divisia index method, considering the impacts of socio-economy, technology evolution, and climate. Results found the following: First, economic growth effects [service industry added value (42.2%) and gross domestic product (36.5%)] and energy consumption (23.8%) were the main drivers of the spike in operational carbon emissions of the megalopolises from 2000 to 2018. Second, except for Cheng-Yu, operational carbon emissions were decoupled from economic growth effects since 2009, with the most significant decoupling status occurring in Jing-Jin-Ji, and technical effects being the main factor leading to the decoupling. Third, the five megalopolises cumulatively decarbonized 233.1 mega-tons of carbon dioxide (MtCO2), offsetting 4.4% of the operational carbon of commercial buildings, with the highest decarbonization level in Jing-Jin-Ji (5.7 MtCO2 per yr, 7.8 kg of carbon dioxide per square meter per yr, and 55.6 kg of carbon dioxide per capita per yr). Furthermore, current decarbonization strategies for megalopolises are reviewed to plan for future low-carbon developments. Overall, this study assesses the operational decarbonization change of commercial buildings in Chinese megalopolises. The findings help inform building of sector pathways toward China's carbon peaking and neutral goals and develop global low-carbon cities.

Life Cycle Assessment of Recently Constructed “Climate Protection Neighbourhoods” – Which Lessons can be Drawn?

The results of a life cycle assessment of five recently finished housing projects in Northern Germany - all of them part of two certified climate protection neighbourhoods - point out the necessity of combining a variety of different carbon reduction approaches in order to reach carbon neutrality. The analysis presented here focuses on both, embodied and operational carbon emissions, as well as embodied and operational energy, over a period of 50 years. Both residential areas examined do not tap the full potential of their environmental impact reduction as they focus on single strategies only: one development limits the reduction of carbon emissions for heating and domestic hot water supply to a max. of 7.5 kg GHG emissions per m2 and year, by means of conventional solid construction. For the other estate the developers encouraged timber construction by requiring a minimum share of the construction volume of 70% timber. Comparing both approaches shows, that climate friendly construction can only be achieved by combining different ways and means, e.g. easily demountable hence reusable timber structures with a high level of energy efficiency and a carbon free heat supply. The results drawn from this study are designated to serve as a basis for discussion of the development of ambitious and climate responsible housing standards in Bremen.

Decarbonizing residential buildings in the developing world: Historical cases from China

China's large residential building stocks lead to the serious effect of operational carbon lock-in, which becomes a major challenge in hitting the carbon peak by 2030. This work is the first to develop the Generalized Divisia Index Method with a matrix of 8 × 14 to identify fourteen factors and analyze the provincial carbon change (especially the decarbonization progress) in residential building operations from 2000 to 2018. It shows that: (1) The operational carbon emissions released by residential buildings increased during 2000–2018, with an average rate of 4.53 % per yr in 30 samples. Behind this, the most positive contributor is residential floor areas, while the most negative contributor is the share of household consumption expenditure in the gross domestic product. (2) The annual decarbonization of most provinces in northern China peaked before 2008, accounting for 4.70 mega-tons of carbon dioxide (MtCO2) per province per yr, and in central and eastern China mainly peaked in approximately 2014, accounting for 7.21 MtCO2 per province per yr, and the annual decarbonization in southern China generally continued to grow. (3) High levels of decarbonization and decarbonization efficiency have been observed in northern and southwestern China, with 35.06 MtCO2 per province of decarbonization and 7.05 % per province of efficiency in 2001–2018. Overall, this study improves the analytical method to assess the decarbonization of building operations, and it helps the governments investigate the building decarbonization potential to promote the schemes of carbon peak.

Assessment of operational carbon emission reduction of energy conservation measures for commercial buildings: Model development

Using energy conservation measures (ECMs) for building retrofit can significantly reduce building operational carbon emissions (BOCEs) and contribute to Chinese carbon neutrality by 2060. This paper involves 11 feasible ECMs for commercial buildings in hot-summer and cold-winter zone, China, and proposes a quick assessment approach to BOCEs reduction. Prototypical models are simulated for ECMs using EnergyPlus and the emission intensity is corrected by the building shape factor and window-to-wall ratio. Based on pre-simulated results, effects on reducing emissions of individual measures and packages of them are studied to develop regression models in SPSS. The results show that decreasing the U-factor of external walls, lighting power density (LPD), or shading coefficient can reduce BOCEs linearly. BOCEs are most sensitive to LPD and using daylighting control can reduce emissions by 5–15%. In addition, increasing the boilers’ efficiency reduces emissions linearly, while performance improvement of chillers or heat pumps reduces emissions logarithmically. Furthermore, utilizing variable speed pumps, heat recovery ventilation, and air-side economizers can reduce emissions by 3.8%, 6.6%, and 15.2%, respectively. Finally, significant interactions exist among measures of enhancing glazing U-factor, adding external shading, using energy-saving lamps, and improving cooling/heating system efficiencies. The developed regression models are validated in a retrofit case in Shanghai. Through assessment, the case can reduce BOCEs by 15.9 kgCO2/m2, with a reduction rate of 20.8%. Compared with recorded data, the relative error of assessing emission reduction is −13.0% and that of assessing reduction rate is 0.5%, which are acceptable in the decision-making stage of retrofit strategies.

Spatiotemporal Analysis of Influencing Factors of Carbon Emission in Public Buildings in China

The rapid development of public buildings has greatly increased the country’s energy consumption and carbon emissions. Excessive carbon emissions contribute to global warming. This paper aims to measure the carbon emissions in the operation of public buildings, and to identify the multiple influencing factors of carbon emissions in operational public buildings. First, the spatial and temporal variation characteristics of carbon emissions from public buildings in 30 provinces of China from 2008–2019 are analyzed. Second, a green building index is constructed, and the STIRPAT (Stochastic Impacts by Regression on Population, Affluence, and Technology) model is utilized to explore the relationship between each influencing factor and carbon emissions, using spatial and temporal geographically weighted regression analysis. The results show that the effects of population, urbanization rate, GDP per capita, green building index, and industrial structure on carbon emissions from public buildings all show spatial correlation and differences. There are east-west differences in the operational carbon emissions of public buildings in China’s provinces. Cluster evolution shows a spatially increasing trend from west to east. To some extent, policymakers can develop appropriate policies for different provinces through the findings.

Net zero by 2050: Investigating carbon-budget compliant retrofit measures for the English housing stock

The UK has enacted one of the most ambitious carbon reduction targets striving for net zero emissions by 2050. A major challenge to achieving this is decarbonizing heating demand with almost 25 m homes in need of retrofit. This paper explores a range of retrofit interventions to the English residential stock. These are deployed immediately in 2021 to investigate the maximum carbon reduction that could be achieved. The impact of these interventions on embodied and operational carbon emissions is estimated from 2021 to 2050. The resulting emissions are compared to estimated national carbon budgets, in order to ascertain, if, and with what combination of retrofit measures, the English housing stock can stay within carbon budgets. The results show that mass deployment of air source or ground source heat pumps can reliably achieve combined embodied and operational emissions within national carbon budgets by 2050. The careful selection of insulation materials is key in bringing down the embodied emissions, particularly to meet stricter carbon budgets. The identified scale and pace of deployment thus needed to stay within carbon budgets is likely to pose enormous practical challenges. To overcome these challenges, we argue for (a) urgently increasing both heat pump deployment, and renewable generation targets beyond existing pledges, (b) increasing social awareness of residential retrofit benefits, and (c) providing more attractive financing options to incentivise and facilitate retrofit uptake.

Electricity Consumption and Operational Carbon Emissions of European Telecom Network Operators

This study presents operational electricity consumption and greenhouse gas emissions for named European telecom network operators during 2015–2018. These results are also compared to data for 2010–2015. The study provides an extensive primary data set, collected from European Telecommunication Network Operators (ETNO) members, covering operations in Europe and beyond, providing data with higher granularity than publicly available sources. The collected data set corresponds to roughly 36 percent of European subscriptions and 8 percent of global subscriptions. This data set was used to calculate the aggregated annual electricity consumption for the assessed operators, as well as associated subscription intensities, in total, for Europe and per network type. Moreover, aggregated electricity-related carbon emissions and emissions from other sources were calculated. Finally, estimates were made for the overall network operation in Europe for 2018 and 2020. The study concludes that the electricity consumption and number of subscriptions for the reporting telecom network operators remained nearly constant (+1 percent and −3 percent, respectively) between 2015 and 2018, while data traffic increased by a factor of three. For the extended period of 2010–2018, the electricity consumption per subscription remained quite stable, slightly below 30 kWh/subscription despite substantial data traffic growth (by a factor of 12).

Resource Efficiency and Thermal Comfort of 3D Printable Concrete Building Envelopes Optimized by Performance Enhancing Insulation: A Numerical Study

3D concrete printing has gained tremendous popularity as a promising technique with the potential to remarkably push the boundaries of conventional concrete technology. Enormous research efforts have been directed towards improving the material properties and structural safety of 3D printed concrete (3DPC) over the last decade. In contrast, little attention has been accorded to its sustainability performance in the built environment. This study compares the energy efficiency, operational carbon emission, and thermal comfort of air cavity 3DPC building envelopes against insulated models. Four insulations, namely expanded polystyrene (EPS), extruded polystyrene (XPS), polyurethane foam (PUF), and fiberglass (FG), are iteratively paired with three different 3DPC mix designs, and their resulting performances are reported. A numerical optimization analysis is performed to obtain combinations of 3DPC building models and insulation with the least energy expenditure, carbon production, and thermal efficiency. The results indicate that insulation considerably enhances the overall environmental performance of 3DPC structures. The optimization process also demonstrates the potential of using 3D printable fiber reinforced engineered cementitious concrete (3DPFRECC) with polyurethane infill for amplified sustainable performance in modern construction.

Low-carbon distribution system planning considering flexible support of zero-carbon energy station

Zero-carbon energy stations (ZCESs) have a promising prospect in reducing carbon emission, which also results in great impacts on the planning scheme of low-carbon distribution system (DS). In this context, this paper carries out the low-carbon DS planning considering the flexible support of ZCES. Firstly, a low-carbon DS planning model is established, where the material carbon emission and operational carbon emission are both considered. Then, for achieving the low-carbon goal of DS, the flexible support of ZCES is considered during the low-carbon DS planning process. Especially, ZCES is supplied by zero-carbon renewable energy (e.g., photovoltaics and wind power). Meanwhile, DS and ZCES are regarded as different stakeholders, which is addressed by the analytical target cascading (ATC) algorithm. In addition, a distributionally robust optimization method is proposed to cope with the probability distribution (PD) uncertainty of renewable energy and loads. Moreover, a tractable low-carbon planning model for DS considering the flexible support of ZCES is reformulated based on the duality method. Finally, the proposed planning model is tested on a modified IEEE 33-node and a practical 99-node distribution system with ZCES. Numerical results show that the proposed low-carbon planning model is effective in managing PD uncertainties, and improving the low-carbon and economic performance of DS while the ATC algorithm also exhibits good convergence performance.