Life Cycle Cost Optimization Research Articles

Optimal design of redundant structural systems: fundamentals

In spite of extended recent interest in System Reliability-Based Design Optimization (System RBDO) and life-cycle cost or Risk Optimization (RO), there is a lack of published studies on optimal design of redundant hyperstatic systems with objective consideration of (a) progressive collapse and (b) the impact of epistemic uncertainties. This paper investigates the fundamental aspects of the problem, by addressing the optimal design of simple two-bar active and passive redundant systems. Progressive collapse is objectively addressed, differentiating consequences of direct collapse of statically determinate structures, and progressive collapse of redundant, statically indeterminate structures. A comprehensive study is performed, considering material post-failure behavior (fragile-ductile), strength correlation, dynamic amplification factors in load re-distribution, and material strength ratios. Physical uncertainty in material strengths and loads is considered. However, it is well known that reliability of a structural system also depends on nonstructural factors, or factors beyond structural design, such as unanticipated loading, manufacturing quality, quality of workmanship and human errors. These factors can be taken into account in an encompassing risk analysis, which accounts for physical and epistemic uncertainties, and which contributes a fixed latent failure probability to the structural optimization problem. Results presented herein show that the latent failure probability is the single most important parameter in determining optimal solutions, in System RBDO and in RO solutions. When the latent failure probability is smaller than target (System RBDO) or optimal (RO) failure probabilities, there is an equivalence between redundant and non-redundant (hyperstatic and isostatic) designs. However, when the latent reliability is smaller than target or optimal reliabilities, optimal designs become necessarily redundant (hyperstatic); as the only way to make system reliability larger than the latent reliability is by making structural systems redundant. This result is widely known in context of system reliability, but has been overlooked in past studies involving structural System RBDO and Risk Optimization.

Degradation process and failure estimation of drilling system based on real data and diffusion process supported by state space models

Technical systems used in adverse environments are subject to very intense degradation and their parts deterioration. Due to the problematic placement of some parts, it is sometimes very difficult, to indicate the level of degradation and possible failure occurrence. Therefore, it is very useful to work with the available field operation data. Since we possess such data and apply progressive methods to model the degradation, we are able to predict the possible failure occurrence and forecast residual useful life. At first, we apply spectral analysis approaches. The spectral analysis is used to capture extreme values in the data structure. The extreme values are later filtered out to avoid future estimations which might be affected by the deformed inputs. In the next step, we use non-parametric smoothing and state space models to acquire trend, variance and related statistics in the data structure. These characteristics are later used as input parameters for specific and new forms of diffusion processes. With these diffusion processes we would like to model the degradation evolvement and failure occurrence. The failure occurrence is represented as one of the statistics of the first passage time (FPT). FPT is a moment when the modelled trajectory hits the predefined threshold – such threshold represents a critical limit for our observation. The outcomes are useful for (i) degradation modelling, deterioration prediction and condition assessment, (ii) operation and maintenance planning and rationalisation, and (iii) life cycle cost optimisation and safety improvement.

A Two-Level Kriging-Based Approach with Active Learning for Solving Time-Variant Risk Optimization Problems

Several methods have been proposed in the literature to solve reliability-based optimization problems, where failure probabilities are design constraints. However, few methods address the problem of life-cycle cost or risk optimization, where failure probabilities are part of the objective function. Moreover, few papers in the literature address time-variant reliability problems in life-cycle cost or risk optimization formulations; in particular, because most often computationally expensive Monte Carlo simulation is required. This paper proposes a numerical framework for solving general risk optimization problems involving time-variant reliability analysis. To alleviate the computational burden of Monte Carlo simulation, two adaptive coupled surrogate models are used: the first one to approximate the objective function, and the second one to approximate the quasi-static limit state function. An iterative procedure is implemented for choosing additional support points to increase the accuracy of the surrogate models. Three application problems are used to illustrate the proposed approach. Two examples involve random load and random resistance degradation processes. The third problem is related to load-path dependent failures. This subject had not yet been addressed in the context of risk-based optimization. It is shown herein that accurate solutions are obtained, with extremely limited numbers of objective function and limit state functions calls.

A Systematic Approach to Predict the Economic and Environmental Effects of the Cost-Optimal Energy Renovation of a Historic Building District on the District Heating System

The economic and environmental performance of a district heating (DH) system is to a great extent affected by the size and dynamic behavior of the DH load. By implementing energy efficiency measures (EEMs) to increase a building’s thermal performance and by performing cost-optimal energy renovation, the operation of the DH system will be altered. This study presents a systematic approach consisting of building categorization, life cycle cost (LCC) optimization, building energy simulation and energy system optimization procedures, investigating the profitability and environmental performance of cost-optimal energy renovation of a historic building district on the DH system. The results show that the proposed approach can successfully be used to predict the economic and environmental effects of cost-optimal energy renovation of a building district on the local DH system. The results revealed that the financial gains of the district are between 186 MSEK (23%) and 218 MSEK (27%) and the financial losses for the DH system vary between 117–194 MSEK (5–8%). However, the suggested renovation measures decrease the local and global CO2 emissions by 71–75 metric ton of CO2eq./year (4%) and 3545–3727 metric ton of CO2eq./year (41–43%), respectively. Total primary energy use was decreased from 57.2 GWh/year to 52.0–52.2 GWh/year.

Resilient pavement design with consideration of flooding effect caused by climate change

Climatological reports demonstrate a clear trend of more frequent occurrence of extreme weathers. Flooding caused by heavy rains severely affects highway pavement performance in many coastal regions. As the trend of climate change continues, highway pavements in these regions will become more vulnerable to flooding. At present, however, pavement design is usually based on historical climatological data and seldom considers future climate changes. Moreover, traditional pavement analysis rarely considers the stochastic nature of weather. This study develops a life-cycle cost optimization model and adopts a stochastic approach to analyzing the effect of climate change. Pavement structure design is optimized by incorporating the flooding effect in the model. As a case study, hourly climate data in the past century in Hong Kong is analyzed to investigate changes in rainfall intensity, and the trends are used to optimize pavement design.

A novel approach to district heating and cooling network design based on life cycle cost optimization

Piping layout, material, and dimension choices are essential in determining the initial capital costs and full operating costs of a district heating and cooling (DHC) network. While common practice aims to minimize initial capital costs or, in some cases, operational costs, this paper introduces a novel method for designing DHC network layouts for minimum total life-cycle cost by introducing additional engineering design parameters related to pipe sizing, heat losses, and pumping energy. The proposed mixed-integer linear programming solution satisfies the thermal and hydraulic constraints on the network while minimizing the objective function of total cost over the lifetime of the network. The method is tested with three case studies. Results show improvement in reducing total life-cycle costs of the network compared to approaches that consider only capital or operating costs and exclude network dimensioning.

Economic viability assessment of sustainable hydrogen production, storage, and utilisation technologies integrated into on- and off-grid micro-grids: A performance comparison of different meta-heuristics

In recent years, there has been considerable interest in the development of zero-emissions, sustainable energy systems utilising the potential of hydrogen energy technologies. However, the improper long-term economic assessment of costs and consequences of such hydrogen-based renewable energy systems has hindered the transition to the so-called hydrogen economy in many cases. One of the main reasons for this is the inefficiency of the optimization techniques employed to estimate the whole-life costs of such systems. Owing to the highly nonlinear and non-convex nature of the life-cycle cost optimization problems of sustainable energy systems using hydrogen as an energy carrier, meta-heuristic optimization techniques must be utilised to solve them. To this end, using a specifically developed artificial intelligence-based micro-grid capacity planning method, this paper examines the performances of twenty meta-heuristics in solving the optimal design problems of three conceptualised hydrogen-based micro-grids, as test-case systems. Accordingly, the obtained numeric simulation results using MATLAB indicate that some of the newly introduced meta-heuristics can play a key role in facilitating the successful, cost-effective development and implementation of hydrogen supply chain models. Notably, the moth-flame optimization algorithm is found capable of reducing the life-cycle costs of micro-grids by up to 6.5% as compared to the dragonfly algorithm.

Life cycle cost optimization of building façade: A social housing case

In this paper, a common social housing archetype design was studied in order to improve the energy and cost performance. The focus is on evaluating the effects of some parameters of the design of the façade in particular: the size of the windows and the optical and thermo-physical properties of the components. The aim is to obtain cost optimal energy efficient scenarios in accordance with the Recast of Energy Performance of Buildings Directive (EPBD Recast) by determining efficient thicknesses of the insulation for the exterior walls and efficient window sizes and types of glazing for each orientation, simultaneously. The parameters of the façade are optimized in order to obtain the dominant values and ranges in terms of energy and cost. There are remarkable differences in the dominant options for the thickness of the insulations, as well as the type and size of windows: they depend on whether they have a north, south and east–west orientation. The decision makers should design each façade in dependence on its orientation to determine its optimal optical and thermo-physical properties in terms of its cost and its consumption of energy. A reduction by approximately 5% in the life cycle cost and 17% in the primary energy use was achieved through the optimization of the base case.

Cost Optimum Design of Zero-Energy Residential Building

The continuous growth of population in sub-urban areas leads to increasing demand for mid-rise housing. Recent studies found that greenhouse gas emission in Indonesia continues to escalate at an alarming rate, and housing development is considered as one of the greenhouse gas contributors. Zero-Energy Residential Building, a highly energy efficient and low carbon housing design concept, is regarded as the answer for this environmental issue. Application of Zero-Energy Residential Building concept can reach almost zero sites electrical consumption and reduce greenhouse gas emission since this concept utilizes clean and renewable energy sources, e.g. solar cell, to generate electricity independently. However, this design concept has not been implemented widely since the utilization of solar panels, and other energy conservation components are still too expensive. This study is proposed to find out an optimum combination of design parameters that contribute to cost optimization housing design using sequential search algorithm. Comprehensive study literature and experiment using software are applied in this research. Hence, using the parameter combination in designing a mid-rise dense housing and Zero-Energy Building concept can generate optimum life cycle cost performance. As a result, the study concludes that the life cycle cost of optimized mid-rise Zero-Energy Building is better than the conventional mid-rise housing with annual electrical cost saving up to 98 percent.

Assessing evidence-based single-step and staged deep retrofit towards nearly zero-energy buildings (nZEB) using multi-objective optimisation

There is a dearth of data and evidence in the literature to assist the industry in determining the most appropriate strategies for large-scale deep retrofitting of non-domestic buildings to achieve healthy low-energy buildings. Support to decision-making and enabling deep retrofit of these buildings requires approaches such as long-term renovation strategies and building renovation passports. This paper compares the impact of single-step and staged retrofit approaches to improve the building energy performance of an existing building to a nearly zero-energy building (nZEB) level with improved comfort and optimal life-cycle costs. The novel developed methodological framework is applied to a university building built in 1975 (partially retrofit in 2005) that is expected to be completely retrofitted in 2020. A set of scenarios are analysed for the case study building using a combination of retrofit measures towards achieving the cost-optimal non-dominated solutions (Pareto front) based on multiple-objective optimisation for the decision-maker. The results highlight that a single-step retrofit can achieve a reduction of up to 60% in primary energy consumption and reduction of 38% in discomfort hours. The findings also indicate that nZEB performance with the primary energy consumption in the range of ~ 75–90 kWh m−2 year−1 (with plug loads) can be achieved cost-effectively through single-step deep retrofit for a university building. Results also highlighted the inability to achieve higher energy performance or improved comfort in two stages relative to completing a deep retrofit in a single stage. The results aim to contribute to the existing debate on the economic and environmental feasibility in realising long-term renovation strategies for existing non-domestic buildings, especially university buildings.

Life Cycle Costing of Public Construction Projects

The purpose of this paper is to highlight the role of life cycle costing in the preparation phase of public construction projects. Life cycle costing is a method of economic analysis directed at all costs related to constructing, operating, and maintaining a construction project over a defined period of time. In the early phase of construction projects, an enormous benefit in life cycle costing can be achieved. The commonly used construction cost minimization approach should be substituted for life cycle cost optimization. In order to gain the maximum value for money, all costs incurred over the whole life span must be estimated. The optimization of the life cycle costs of a construction project is essential for a complex decision making process. All taken into consideration, the solution with the minimum value of life cycle costs can be chosen. Public investors are required to meet the objectives of sustainable building, and as a group they face limited financial resources and frequently a very strict institutional framework including procurement procedures. The quantification of life cycle costs, when deciding on a construction project, is required by the public sector in the Czech Republic. In addition, the estimated amount of life cycle costs has become a criterion in public tenders. The paper summarizes experience in building design valuation in terms of these life cycle costs.

Evaluation of energy renovation strategies for 12 historic building types using LCC optimization

The life cycle cost (LCC) optimization is a vital method when performing building energy renovation. The present paper provides an evaluation of cost-optimal energy renovation strategies for historic buildings using LCC optimization software OPERA-MILP. The evaluation is performed based on preset targets depending on LCC (LCC optimum) and energy use (decrease by 50%), where the environmental performance is also addressed. Twelve building types, which are typical of the historic building stock in Visby, Sweden, are used as the study object.The results show possible decreases of 12–38% in LCC when targeting LCC optimum. When targeting a 50% decrease in energy use, the LCC is decreased in 21 of 26 cases compared to before energy renovation. Cost-efficient EEMs on the building envelope are characterized by low renovation costs and additional insulation of building components with poor thermal properties. Furthermore, the environmental performance from the energy renovations is highly dependent on the chosen energy system boundary.

Applying Renewable Energy Technologies in an Integrated Optimization Method for Residential Building’s Design

Designing a Zero Energy Building (ZEB) requires an optimal choice of the materials of a building envelope. Different material properties and window areas could be selected to generate a set of possibilities of the design of a building, being the demand defined by its thermal characteristics. The energy demand of a building could be produced with renewable systems such as photovoltaic. Moreover, the HVAC (Heating, Ventilation, and Air Conditioning) systems could be selected considering the system cost. The present methodology focuses on finding a balance between investment and low energy consumption for a building, based on an integrated optimization method. Such methodology applies a Tabu search algorithm and a simplified model to select the passive design. Afterwards, active elements of the design, as photovoltaic systems, are selected. Therefore, the methodology faces the problem of estimating the annual energy demand and the life cycle cost. The goal is the design of a building with a large amount of energy generated by renewable energy, to have a ZEB, and in the worst case, a nearly Zero Energy Building (nZEB). This methodology reduces investment, reduces the energy demand and selects the best construction materials, renewable energy, and air conditioning system. The present paper analyzes a set of case studies considering different climatic zones in Spain. The results conclude that the methodology could help builders in the design stage, to find a new design that allows a ZEB with the optimal life cycle cost.

Multidisciplinary Optimization of Life-Cycle Energy and Cost Using a BIM-Based Master Model

Virtual design tools and methods can aid in creating decision bases, but it is a challenge to balance all the trade-offs between different disciplines in building design. Optimization methods are at hand, but the question is how to connect and coordinate the updating of the domain models of each discipline and centralize the product definition into one source instead of having several unconnected product definitions. Building information modelling (BIM) features the idea of centralizing the product definition to a BIM-model and creating interoperability between models from different domains and previous research reports on different applications in a number of fields within construction. Recent research features BIM-based optimization, but there is still a question of knowing how to design a BIM-based process using neutral file formats to enable multidisciplinary optimization of life-cycle energy and cost. This paper proposes a framework for neutral BIM-based multidisciplinary optimization. The framework consists of (1) a centralized master model, from which different discipline-specific domain models are generated and evaluated; and (2) an optimization algorithm controlling the optimization loop. Based on the proposed framework, a prototype was developed and used in a case study of a Swedish multifamily residential building to test the framework’s applicability in generating and optimizing multiple models based on the BIM-model. The prototype was developed to enhance the building’s sustainability performance by optimizing the trade-off between the building’s life-cycle energy (LCE) and life-cycle cost (LCC) when choosing material for the envelope. The results of the case study demonstrated the applicability of the framework and prototype in optimizing the trade-off between conflicting objectives, such as LCE and LCC, during the design process.

Fast Seismic Life Cycle Cost Optimization of Steel Moment Frames to Improve Seismic Performance

This study presents a fast method of Life Cycle Cost (LCC) optimization of structures. One of the main obstacles to implementation of seismic lice cycle cost optimization is the time-consuming process of evaluating the possibility of failure of the structure. To overcome this restriction, in the proposed approach, the probability of failure is estimated using fragility functions. A fast method for developing the fragility function was employed in this paper to reduce the computation time. Two well-studied frames, adopted from the literature, were studied to demonstrate the implementation of the methodology. A comparison of results with previous studies indicates that a reasonable increase in the initial cost substantially reduces damage and life-cycle costs of the structure. It also significantly improves the seismic performance of structures. The proposed method can be employed to design more reliable and economical structures.

LCC Optimization of Different Insulation Materials and Energy Sources Used in HVAC Duct Applications

The heating, ventilation and air conditioning (HVAC) ducts distribute the conditioned air to different zones. They are installed outside in a harsh environment which escalates the energy loss due to heat transfer. This study aims to estimate the economically feasible and environmental amiable insulation thickness for HVAC duct using life cycle cost (LCC) and environmental assessment method. It deems five insulation materials for the duct and eight energy sources for chiller operation in selected countries. It uses the design and operating parameters of the duct installed in a renowned pharmaceutical company at Jamshoro/Pakistan. An apropos mathematical model is developed using the collected parameters to calculate optimum insulation thickness (OIT), LCC, maximum energy savings (ES) at minimum payback period (PP) and emission reduction in the insulated duct. It examines the effect of insulation thickness on economic and environmental outcomes using the linear slope line regression method. The results revealed that the use of EP and natural gas has minimum LCC of 13.66 $/m-year (− 0.484), 95% ES (0.248) corresponding to OIT (64.64 mm) with minimum PP of 1.2 years (decreasing at a rate of − 3.69 with insulation thickness). Fuel consumption reduces dramatically (− 0.79) and once OIT is achieved, further increasing insulation thickness has a negligible impact on fuel savings (− 0.041). Higher fuel cost produces maximum ES in the duct and reduces PP of insulation cost in selected countries but they do not affect the variation in fuel consumption and CO, $$\hbox {CO}_{2}$$ and $$\hbox {SO}_{2}$$ emission. Additionally, OIT of EP for duct reduces CO and $$\hbox {CO}_{2}$$ emission at a maximum rate of -0.134 in case LPG (96%) and − 0.484 (95%) in the case of natural gas, respectively.

Architecture, Ecology and Economy: Synergy or Contradiction?

Economy and ecology in architecture are seen by most ascontradictions. On the other hand traditional building concepts andvernacular architecture all over the world use local renewable materialsand building methods as well as designs based on optimizations, traditionsand culture and thus follow an economic and ecologic approach. Theenvironment is not a world outside the economy. Well considered ecologicapproaches and solutions for socio-ecological problems can triggerinnovation and economic success. As architects we have an increasingresponsibility towards sustainability. In this context the use of buildingcost optimization and life cycle cost optimization without compromisingquality will be part of the „Ecological Economy in Architecture”. The goalwill be to create consumer value on several levels. Ecologic architecturalprojects will create economic competitive advantage in conjunction withthe creation of unique selling points. The starting points will be the wellbalancedanalysis and management of economic efficiency, ecological, social and cultural aspects - considering all stakeholders and the wholelifecycle of buildings. Hence current ways of design, decision-making, communication and education must be questioned from all sides.

Life Cycle Cost Analysis and Optimization of Modular Substation

Due to the lack of high standardization and specialization, the production scale of modular substation is difficult to meet the established requirements. Compared with traditional substation construction, there are still practical problems such as high production costs. Therefore, it is still difficult to promote modular substation. Considering the life cycle of modular substation project, Cost Breakdown Structure (CBS) and Engineering Breakdown Structure (EBS) of the modular substation were defined through literature reading and data analysis. Then use the life cycle cost mapping model to further determine the mapping relationship between CBS and EBS. Finally, the connotation and goal of the life cycle cost optimization of modular substation were proposed, which can effectively promote the cost management of modular substation projects and optimization.

Cradle to Cradle and Whole-Life Carbon assessment – Barriers and opportunities towards a circular economic building sector

The general awareness of climate change has been increasing steadily while buildings continue to be the main contributors to greenhouse gas emissions. To address the need for change in the building industry and transform its hazardous impacts on the environment to a positive footprint, circular economic design approaches and Whole-Life Carbon (WLC) assessment have been introduced. This paper analyses the main barriers for a successful implementation of the regenerative Cradle to Cradle (C2C) concept and WLC evaluation, identifying the lack of unified and measurable framework along with the deficiency of detailed case studies and post occupancy evaluation. In the context of the increasing demand for carbon accounting, obtaining comprehensive information on embodied carbon in buildings is challenging despite the existing Life Cycle Assessment structure. To link theory with practice, the paper discusses the London School of Economics Centre Buildings Redevelopment by RSH+P as case study. It reveals barriers and opportunities for WLC evaluation as well as the potential of life cycle cost optimization in environmental and economic terms.The paper concludes with a reflection on how the certification of materials through material passports may not only achieve a higher transparency but lead to a circular economic building industry by comprehensive WLC assessment and a closer implementation of reversible building design corresponding to the C2C principles. The potential of combining WLC evaluation with C2C strategies and translating them into a comprehensive, unified assessment framework for a circular building sector is identified.

Life cycle costs optimization of residential buildings

This paper considers the questions of techno-economic optimization in order to determine the thermal transmittance coefficient of the external walls of an existing residential building.The optimization procedure is conducted for the climatic and economic conditions in Bulgaria and taking into account the existing legal framework. The minimum of the building life cycle costs is determined by using genetic algorithm