Retrofit Planning Research Articles

Comparative study on different energy-saving plans using water-side economizer to retrofit the computer room air conditioning system

An energy efficient, environmentally friendly and economical retrofit plan of traditional computer room air conditioning system is necessary to reduce energy consumption of data centers. In this study, two energy-saving retrofit plans, a computer room air handler system with water-side economizer (Plan 1) and a loop thermosyphon system with water-side economizer (Plan 2), are compared with an air-cooled computer room air conditioning system (existing cooling system) in a data center. To analyze and compare the energy efficiency, environmental and economic potential, energy models of the existing cooling system and retrofit plans are established. Under different set points (including supply chilled water temperature and supply air temperature) and 2.08–6 kW average electric power of racks, the free cooling periods of Plan 1 and Plan 2 reach 3878–5867 h and 4541–7661 h, respectively, which lead to the annual energy consumption of Plan 1 and Plan 2 decreases by 27.6–47.3% and 53.4–63.6%, respectively. Due to the lower annual energy consumption of main equipment (including chillers, chilled water pumps, cooling water pumps and terminal equipment), Power Usage Effectiveness of Plan 2 is 0.049–0.090 lower than that of Plan 1, and Global Coefficient of Performance of Plan 2 is 23.3–67.3% higher than that of Plan 1. Furthermore, the annual CO2 emissions of Plan 1 and Plan 2 are 337.3–557.1 tons and 599.8–1106.9 tons less than those of the existing cooling system at different operating stages respectively. Finally, the dynamic payback periods of Plan 1 and Plan 2 are 4.11–5.42 years and 1.64–3.57 years.

Probabilistic Seismic Multi-hazard Risk and Restoration Modeling for Resilience-informed Decision Making in Railway Networks

ABSTRACT Transportation systems, such as railways, are considered critical infrastructure. It is essential to identify potential hazards that can affect the functionality of these systems and quantify metrics that can be used for resilience-informed decision-making. This paper develops an integrated probabilistic model for seismic multi-hazard risk and restoration assessment of railway systems by accounting for the effects of seismic waves propagation, liquefaction and landslide as main phenomena affecting the integrity of distributed networked infrastructure; this is done via a GIS-based user interface. An illustrative case study is then presented to assess the seismic risk and restoration of the Tehran-Sari railway in Iran. The implementation results demonstrate the capability of the presented methodology to quantify physical metrics (including combined damage state of network components, component- and system-level functionality and restoration) and economic loss. These metrics can assist officials with implementing retrofit plans to reduce loss and improve the resilience of railway system segments.

In-situ test and model updating of an RC tied-arch bridge

The Italian bridge asset is dated, and the functionality of many bridges is jeopardised by degradation due to ageing and environmental effects, as well as by increasing traffic loads. An adequate operational monitoring and maintenance program is essential for ensuring the safety condition of these critical structures. Administrations in charge and policymakers must clearly understand the actual condition of the infrastructure asset in order to optimise maintenance and retrofit planning. For this purpose, visual inspections might fail to reflect the current condition accurately; thus, additional experimental investigation campaigns are desirable. In the knowledge process for existing bridges, valuable information can be obtained through appropriate experimental tests, such as material testing and dynamic identification. Moreover, the potential of on-site test results in updating structural modelling has been demonstrated, successfully improving the performance assessment of bridges. However, sensitivity-based Finite Element model updating requires a deep knowledge of the examined structure to determine which parameters mainly affect the dynamic response.In this framework, the contribution of this paper consists of a typological analysis and model updating of an existing RC tied-arch bridge dating back to the 1930s. The structural condition was assessed by an on-site investigation campaign, including a geometric survey, material testing, and ambient vibration test (AVT). For the latter, three algorithms for operational modal analysis were performed to extract the bridge's modal parameters and then compare outcomes. Lastly, results from experimental tests were used to update a 3D finite element model.

The Impact of Traditional Raw Earth Dwellings’ Envelope Retrofitting on Energy Saving: A Case Study from Zhushan Village, in West of Hunan, China

This study presents the CO2 emissions and energy performance of traditional raw earth dwellings’ envelope retrofitting located in the Zhushan Village, western Hunan Province, China. The numerical simulations of heating energy consumption on the building models were performed using DesignBuilder, an energy simulation program. The energy performance was evaluated using the indexes (including energy consumption, CO2 emissions, heat balance analysis, and air temperature profiles). The detailed evaluation process of the energy performance is presented as follows. First, the current situation was analyzed through the field research, and two typical building models were built. Second, all schemes were simulated using the DesignBuilder software. Subsequently, the four main retrofit measures (replacing the external insulation windows, setting the external wall insulation layer, setting the roof insulation layer, and setting the ceiling insulation layer) were analyzed, respectively. The optimal parameters of the respective retrofit measure were calculated. Lastly, a multi-objective optimization analysis was conducted on all retrofit plans using the coupling method. In the winter, the results indicated that the “I-shape” dwelling heat consumption of the enclosure structure was reduced by 12.8 kW·h/m2, and the CO2 emissions were reduced by 882.8 kg. While in the benchmark building, the results showed that the “L-shape” dwelling heat consumption of the enclosure structure was decreased by 13.27 kW·h/m2, and the CO2 emissions were reduced by 894.4 kg. As the renewal scheme has been progressively implemented, the whole Zhushan Village will save energy by 11.2 × 104 kW·h after the insulation renewal of the envelope structure is completed.

Aesthetic appealing wall insulation: A novel approach for uptake of solid wall insulation in the UK

Solid wall dwellings in the UK are in urgent need for energy retrofit to support achieving the UK net-zero strategies in the building sector and reduce fuel poverty. Several barriers are a cause of uncertainty for householders about Solid Wall 1nsulation (SWI) and slow down the progress. This paper aims to examine people's perceptions of possible inclusion of aesthetics elements in Internal Wall Insulation (IWI), providing a suitable solution to promote wall insulation intake and attractiveness. To achieve this aim, first, the current literature is critically reviewed and analysed to highlight the gap between energy studies and design/aesthetic features of SWI retrofit. Then, an online survey is conducted, and the collected data are analysed. The results show that the aesthetic factor is very important for participants with more than 90% agreement. This level of agreement is as high as other well-known critical factors in renovation such as cost and energy saving. Also, aesthetic integration in IWI can surpasses negative concerns such as the retrofit cost or losing internal space. Furthermore, over 2/3rd of participants are in agreement with a suggested business model for delivering both aesthetic and energy improvement in combined retrofit plans by established approved organizations. It is concluded that aesthetic inclusion is the priority and an encouraging factor in the internal renovation to reduce the barriers and increase success. Finally, the findings from this research pointed to how the retrofit industry, policymakers, and designers should evolve to achieve the benefits of aesthetics in SWI.

Hotel Adapted to the Requirements of an nZEB Building—Thermal Energy Performance and Assessment of Energy Retrofit Plan

Recently, emissions and the energy use of the building and construction sector globally increased. Therefore, energy retrofit processes and reducing the energy consumption of buildings are increasingly often discussed by the academic community, industry, and end-users. The application of high-performance technologies and highly insulating materials results in a low energy demand in newly constructed buildings. A crucial challenge is to reduce energy consumption in existing buildings. The article presents an energy analysis of the reconstruction of a historic building adapted to hotel functionality. Based on the available information on the design of the facility, and the annual demand for cooling and heating energy, simulations of the energy performance were carried out. The proposals to exchange the heat source and replace the existing systems were simulated and assessed. Three different retrofit options were analyzed, including the replacement of the air handling unit (variant 1—v1), bathroom fixtures (v2), and, in the last scenario analyzed (v3), the above-mentioned activities and the usage of tri-generation units. As the results show, such solutions allow for the reduction in final energy consumption of 20%, to 73% regarding the baseline variant.

Integrating Sustainability and Users’ Demands in the Retrofit of a University Campus in China

Green retrofit is essential for the sustainable development of Chinese Higher Education Institutions (HEIs). Limited by time and cost, a campus retrofit plan needs to consider both sustainability principles and usage demands to set feasible priorities. By integrating usage demands with sustainability principles, this paper aims to observe the relationship between the sustainability assessment tool (SAT) indicators of campus retrofit and users’ needs in this process. The Chinese official SAT for campuses was combined with the campus environment components from six investigated HEIs, and then processed by a group of 15 members to establish an implementable framework of retrofit objectives. Taking the Weijin Campus of Tianjin University as an example, feedback from 432 users on the sample environment was analyzed according to our framework. The results show the difference between the users’ perspective and sustainability indicators, emphasizing the importance of the sustainable development of HEIs and leading to the implementation of measures to improve sustainability awareness and guide a retrofit.

Integrated retrofit solutions for improving the energy performance of historic buildings through energy technology suitability analyses: Retrofit plan of wooden truss and masonry composite structure in Korea in the 1920s

Building energy consumption and carbon emissions must be reduced to decrease the rate of global warming. To improve the energy efficiency of historic buildings, energy retrofitting can serve as an effective strategy. Retrofitting historic buildings is difficult due to the conflict between the historical value and usefulness of the building, but a modern scientific approach can help ensure that valuable historical records and artifacts remain protected and available. In addition, the retrofit of historic buildings can contribute, although a small part, to reducing carbon emissions nationally, and can have a symbolic meaning as a combination of history and modernity.This paper proposes a package of appropriate measures to improve energy efficiency, reduce the energy consumption of buildings, and preserve regularly used historic buildings for 100-year-old wooden truss and masonry composite structured historic buildings in Korea. The proposed measures are applied to most historic buildings in Korea built in the 1920s and have the potential to improve building performance. A new approach to applying energy technology to historic buildings is proposed. The energy application suitability analysis process was established by integrating three analysis techniques: the energy-saving effect analysis technique, historical value impact evaluation technique, and economic analysis technique. To achieve an appropriate retrofit plan, the condition of a building was evaluated through on-site diagnosis. Thermal transmittance rate assessments, temperature, and humidity monitoring, and infrared thermal imaging analyses were performed to evaluate the building's condition. Consequently, thermal transmittance rates for the wall and roof of the historic building were 1.18 W/m2K and 1.67 W/m2K, respectively, which indicated a risk of excessive energy consumption and condensation. Then, the suitability of each energy technology was evaluated by analyzing its economic feasibility and impact on the historical value and by simulating the reduction in energy consumption of the building. Thereafter, based on the analyses, the energy technologies deemed suitable were integrated to form an energy-efficient retrofit package, and an appropriate solution was elucidated. In conclusion, the package with the lowest impact on the historical value and the highest energy reduction decreased the total energy consumption by 15.9%. According to the results of this study, the process and package solutions proposed in this study are appropriate measures for historic buildings built in the 1920s in Korea, and can be a strategy with the potential to reduce carbon emissions and energy.

Seismic reliability assessment of bridge networks considering travel time and connectivity reliabilities

AbstractTransportation networks play a vital role in transporting goods and casualties immediately after an earthquake. Thus, identifying the most reliable and shortest path is critical for ensuring efficient emergency response and recovery after an earthquake; consequently, it is important to compute the reliability of transportation networks by simultaneously accounting for connectivity and travel time. In this regard, this paper proposes a novel seismic reliability indicator termed as the travel time and connectivity reliability (TTCR), which combines the travel time and connectivity reliabilities. Additionally, a novel framework for computing the TTCR of transportation networks is proposed. The proposed methodology is applied to a bridge network in California. Furthermore, a retrofit plan based on the TTCR is proposed to help risk managers make appropriate and timely decisions for reducing the seismic risk of transportation networks.

Sustainable energy retrofit plan for enhancing energy efficiency of residential apartments in arid climate: case of Afghanistan

Sustainable energy retrofit plan for enhancing energy efficiency of residential apartments in arid climate: case of Afghanistan

Accelerating the 1.5°C energy transition for Canadian residential buildings through selective direct electrification with heat pumps

Limiting global warming to 1.5–2.0°C in line with our climate commitments will require decarbonization of residential buildings. The traditional approach starts with major energy efficiency upgrades to the building envelope followed by switching to low‐carbon fuel sources for space and water heating. Building envelope retrofits have been a policy goal for over two decades in Canada and elsewhere, yet historical rates and associated emission reductions fall far short of what is required if we are to meet our climate targets. Alternatively, we propose direct fuel switching to electric heat pumps for space and water heating in regions with low‐carbon electricity. Using a database of 44,463 home energy profiles in Waterloo Region, Canada, we modeled the energy efficiency and greenhouse gas emission impacts of building envelope retrofits and direct electrification. While all retrofit plans achieved significant energy efficiency gains (17‐40%), so did direct electrification (70%) and building envelope retrofits plus electrification combined (70‐80%). Only plans that included electric heat pumps achieved greenhouse gas emission reductions of 90% or more. Compared to the conventional approach, direct electrification with heat pumps may be a simpler, more effective, and more realistic approach for policies aiming to decarbonize the residential sector.

Machine Learning–Based Seismic Reliability Assessment of Bridge Networks

Transportation networks are critical components of lifeline systems. They can experience disruptions due to seismic hazards that could lead to severe emergency response and recovery problems. Finding an efficient and effective method to evaluate the seismic reliability of bridge networks is crucial for risk managers. This study proposes a method that can compute the seismic reliability of bridge networks using machine learning techniques. The proposed method is computationally less expensive than existing methods and can be implemented easily in emergency risk management systems. Moreover, it includes information on ranking bridges and prioritizing retrofit plans.

Application and evaluation of phase change materials for improving photovoltaic power generation efficiency and roof overheating reduction

With the development of countries, concerns about global warming have increased. Many countries are taking steps to implement green building-related policies to reduce carbon dioxide emissions; however, these policies are generally applied to new buildings. Therefore, this study focused on the applicability of phase change materials (PCMs) and the optimal application method for educational buildings that have a long service period and are difficult to dismantle among existing buildings. The best application is focused on reducing the building energy demand. phase change materials were applied to address concerns regarding surface temperatures of the building. The passive element, phase change material integrated brick, was applied to the roof, while the active element was a phase change material packed into the back of photovoltaic (PV) panels. Five scenarios were considered in assessing these technologies. photovoltaic installation on the roof surface was assumed for all scenarios, except scenario 1. In scenario 3, the phase change material was applied to the back of the photovoltaic panel, and in scenario 4, a brick layer impregnated with the phase change material was added to the roof surface. In scenario 5, the technologies of scenarios 3 and 4 were applied in combination. As a result of the analysis across the five scenarios, a maximum annual cooling load reduction of 14 521.6 kWh was derived. The overall heating demand increased, with the maximum annual heating demand increasing by 7134.2 kWh. Electrical energy was produced by installing photovoltaic panels, and energy savings were achieved; the highest overall load reduction rate was 22.55%. The calculated shortest payback period was seven years, which is reasonable. Based on cost and energy aspects, scenario 4 is considered the optimal retrofit plan. These results suggest that significant cost and energy savings can be achieved through building renovation with phase change materials.

Artificial Neural Network for Predicting Building Energy Performance: A Surrogate Energy Retrofits Decision Support Framework

Assessing the energy performance of existing residential buildings (ERB) has been identified as key to improving building energy efficiency and reducing associated greenhouse gas emissions in Canada. However, identifying optimal retrofit packages requires a significant amount of knowledge of building energy modelling, and it is a time-consuming and laborious process. This paper proposed a data-driven framework that combines machine learning, multi-objective optimization, and multi-criteria decision-making techniques to evaluate the energy performance of ERB and thereby formulate optimal retrofit plans. First, an artificial neural network (ANN) was developed to predict the energy performance of a wide range of retrofit packages. A genetic algorithm was employed to determine the best structure and hyperparameters of the ANN model. Then, the energy consumption results were integrated with environmental and economic impact data to evaluate the environmental and economic performance of retrofit packages and thereby identify Pareto optimal solutions. Finally, a multi-criteria decision-making method was used to select the best retrofit packages among the optimal solutions. The proposed framework was validated using data on a typical residential building in British Columbia, Canada. The results indicated that this framework could effectively predict building energy performance and help decision-makers to make an optimal decision when choosing retrofit packages.

Exploratory and Multi-Objective Decision-Making Methods for Retrofit Planning Processes

Existing buildings are seen as a potential field where effective carbon-saving and energy-efficiency strategies can be applied. Their lifetime and performance can be increased by implementing different retrofit measures. The retrofit processes remain a complex task that necessitates long-term planning and costly operations and requires a consensus of their stakeholders to identify an ultimate solution from many alternatives. This paper demonstrates a simulation-based exploratory approach, allowing a broader consideration of alternative retrofit solutions to increase non-technical and technical stakeholders’ involvement over design decisions. A hypothetical office building was selected, and a list of retrofit parameters and their combinations focusing on multiple objectives was determined, modeled, simulated, and visualized. Three different decision-making approaches are presented and discussed over the case study results. The study suggests that giving a voice to all stakeholders in decision-making processes might lead to achieving more robust retrofit solutions.

Predicting Energy Savings of the UK Housing Stock under a Step-by-Step Energy Retrofit Scenario towards Net-Zero

The UK has one of the least energy-efficient housing stocks in Europe. By 2030, the emissions from UK homes need to fall by at least 24% from 1990 levels to meet the UK’s ambitious goal, which is reaching net-zero emissions. The originality of this paper is to apply the building typology approach to predict energy savings of the UK housing stock under a step-by-step energy retrofit scenario, targeting the Passive House Standard for refurbishments of existing buildings, namely the EnerPHit “Quality-Approved Energy Retrofit with Passive House Components.” The typologies consist of twenty reference buildings, representative of five construction ages and four building sizes. The energy balance of the UK residential buildings was created and validated against statistical data. A building stock retrofit plan specifying the order in which to apply energy efficiency measures was elaborated, and energy savings were calculated. The predicted total energy demand for the UK residential building stock for the year 2022 is 37.7 MTOE, and the carbon emissions estimation is 65.33 MtCO2e. The energy-saving potential is 87%, and carbon reductions are about 76%, considering all the steps of renovation applied. It has been demonstrated that the step that provides the biggest savings across the housing stock is the one that involves replacing windows, draught-proofing, and installing mechanical ventilation with heat recovery.

A new approach to retrofit plans for distributed energy resources to mitigate adverse impacts on bulk power systems stability

This work presents a new methodology to assess the need of a retrofit plan to readjust anti-islanding protection of distributed energy resources (DERs) with focus on bulk power systems stability. The proposed approach aims to reduce DERs cascade disconnection during major disturbances in transmission networks, a phenomenon that can amplify or result in major blackouts in power systems with high or moderate DERs penetration. The proposed methodology is based on the assessment of Dynamic Security Regions with the incorporation of a simplified modeling to represent DERs cascade disconnection. As a result, recommendations for executing a retrofit plan with a low cost, preserving an adequate level of security, are provided. Initially, the impact of DERs disconnection on the Brazilian Interconnected Power Systems (BIPS) is demonstrated, highlighting the importance of modeling such effect in stability studies. Then, the proposed methodology is applied to the BIPS, evidencing its benefits by specifying the minimum amount of DERs that needs to be submitted to a retrofit plan to guarantee an adequate level of security.

Seismic performance assessment of an existing multispan bridge in eastern Canada retrofitted with fiber reinforced elastomeric isolator

A seismically resilient transportation network entails preprioritized retrofit plans for conventionally designed highway bridges. This is particularly important for the province of Ontario in Canada, where more than 44% of the multispan bridges have been constructed prior to 1970. To support future seismic risk mitigation efforts, this study evaluated the seismic performance of a multispan continuous reinforced concrete bridge in Ontario, Canada, in its as-built and retrofitted conditions. Seismic retrofit is conducted utilizing novel Fiber Reinforced Elastomeric Isolators (FREIs). Analytical fragility curves are developed using Incremental Dynamic Analysis (IDA) on a three-dimensional nonlinear finite element model of the bridge using 45 synthetic ground motion records for eastern Canada. Results indicate that seismic isolation can effectively mitigate the seismic demand on columns and transfer the shear forces to the end abutments resulting in excessive backfill soil deformation. However, this deformation does not necessarily result in bridge failure and traffic disruption.

An advanced Grid Diagram for heat exchanger network retrofit with detailed plate heat exchanger design

This paper presents a method for heat exchanger network (HEN) optimisation considering plate heat exchangers (PHEs), incorporating detailed PHEs design. The developed method starts from a mathematical model based on the Advanced Grid Diagram, which can optimise the HEN structure. The model minimises the energy consumption cost with the constraints that enable a solution thermodynamically feasible. Then comes the heat exchanger type selection part, which is provided by a graphical tool helping to identify which types of the heat exchanger are feasible. The feasible temperature range can be easily visualised to avoid the temperature violation of PHEs. This selection part integrates the area calculation and cost calculation with the detailed heat exchanger design. The method has been tested by a case study of crude oil distillation system illustrating that the application of brazed plate heat exchangers (BHEs) of CB series manufactured by Alfa Laval can save 6.6% of the investment cost for new heat exchangers compared with the retrofit plan that only shell-and-tube and double pipe heat exchangers are used.

Optimization and BIM-based lifecycle assessment integration for energy efficiency retrofit of buildings

A retrofit plan for improving the energy efficiency of an existing building can contribute to a sustainable built environment. This study presents a novel framework for integrating mathematical optimization, 6D-Building Information Modeling (BIM), and Life Cycle Assessment to enhance existing buildings' energy efficiency through applying energy retrofit measures. This framework aims to (1) integrate life cycle cost, and environmental impacts analysis (2) identify energy-efficient alternatives for buildings' energy retrofit (3) make the decision-making process straightforward for decision-makers and investors (4) discover the primary energy efficiency agents that impose the most energy waste on existing buildings. This study contributes to the body of knowledge by applying effective retrofit measures and alternative material choice and empowers decision-making by analyzing life cycle cost and environmental impacts of building envelopes by combining mathematical optimization, BIM, and LCA. The BIM energy model compares the cooling and heating loads of the building's components before and after applying retrofitting measures. The results show that inefficient buildings' envelopes and evaporative coolers play a significant role in energy consumption. A developed mathematical optimization model estimates the economic benefits of energy efficiency upgrades to minimize the total lifecycle cost of a building during its lifetime. Moreover, it provides an optimum energy retrofitting scenario that leads to reductions of 24%–58.2% in energy consumption. In conclusion, the Life Cycle Assessment Comparison between the building before and after retrofitted measures demonstrates that over 45% of global warming impacts could be reduced in the well-established building.