Zakia Afroz - Academia.edu (original) (raw)

Papers by Zakia Afroz

Energy and Buildings, Aug 1, 2021

Abstract While baseline energy modelling approaches for buildings are progressing to meet the dem... more Abstract While baseline energy modelling approaches for buildings are progressing to meet the demand for measurement and verification (M&V) of savings of an energy performance contract, more robust and insightful modelling approaches are needed. This study compares four baseline modelling approaches (e.g., change point, nonlinear autoregressive exogenous models (NARX), Gaussian process, and ensembles of trees) in terms of predictive accuracy and operational insights. The approaches were selected based on preliminary study and employed on pre- and post-intervention data gathered from twelve commercial buildings in Ottawa, Canada. Changes in the post-intervention energy use were estimated by comparing the predicted data with measured data for the individual buildings. The known primary intervention in these buildings was implementing commercially available smart building technologies that identify and address operational suboptimalities. A deeper analysis of one building’s automation system data indicates that energy savings were largely due to simple corrective actions such as eliminating the concurrent operation of heating and cooling coils of an air handling unit. The results show that saving estimates are largely affected by the choice of baseline energy modelling approach. NARX outperformed all other modelling approaches regarding accuracy and data fitting capability. On the contrary, the change point modelling approach offered insights into the operational performance of the buildings.

Energy and Buildings, Jul 1, 2020

The ventilation component is one of the critical parts in an heating, ventilation and airconditio... more The ventilation component is one of the critical parts in an heating, ventilation and airconditioning systems (HVAC) system and holds prime importance in ensuring operational efficacy and efficiency in terms of energy consumption and indoor environmental conditions. A true demand-based ventilation system with an economy air cycle not only offers reduced amounts of energy consumption but also can take part in a healthy indoor environment. This study provides true insight into the performance of a typical variable-air-volume air handling unit system under different operating conditions through a rigorous case study analysis in a real commercial building. To highlight pragmatic solutions to existing complexity within demand control ventilation strategies of the case building this study sets up real-time dynamic scenarios and investigates those scenarios in the context of indoor environment where both carbon dioxide (CO 2) and volatile organic compound (VOC) concentrations are linked. To predict and monitor the indoor air CO 2 concentration for the stated real time scenarios this study uses the mass balance equation for CO 2 concentration. This study demonstrates that integrating the CO 2 mass balance equation along with CO 2 sensor data into the building management control system not only assists in reducing energy consumption but also takes part in a healthy indoor environment. This study suggests including the mass balance equation for CO 2 concentration into the Australian ventilation standard AS 1668.2.

Energy Procedia, Dec 1, 2017

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Heating, Ventilation, and Air Conditioning (HVAC) systems are responsible for a substantial share... more Heating, Ventilation, and Air Conditioning (HVAC) systems are responsible for a substantial share of the energy consumed in commercial buildings. Energy used by HVAC systems has increased over the years due to its broader application in response to the growing demand for better thermal comfort within the built environment. While existing case studies demonstrate the energy saving potential of efficient HVAC operation, there is a lack of studies quantifying energy savings from optimal operation of HVAC systems when considering indoor environmental conditions. This research aims to improve the performance of HVAC systems by optimizing its energy consumption without compromising indoor environmental conditions. The concept of maintaining indoor environmental conditions poses new challenges to the optimal operation of HVAC systems. While the primary objective of ensuring optimal operation is to minimize energy consumption, controlling the indoor environmental parameters, e.g., temperature, humidity, the level of carbon dioxide (CO2), and volatile organic compounds (VOCs) to remain within the acceptable range imposes excess energy use. These two conflicting objectives constitute a multi-variable constrained optimization problem that has been solved using a particle swarm algorithm (PSO). A real-time predictive model has been developed for individual indoor environmental parameters and HVAC energy consumption using Nonlinear Autoregressive Exogenous (NARX) neural network (NN). During model development, efforts have been paid to optimize the performance of the model in terms of complexity, prediction results, and ease of application to a real system. The proposed predictive models are then optimized to provide an optimal control setting for HVAC systems taking into account seasonal variations. An extensive case study analysis has been performed in a real commercial building to demonstrate the effectiveness of developing predictive models and evaluating the relevance of integrating indoor air quality (IAQ) within the optimization problem. Results show that it is possible to minimize 7.8% energy consumption from HVAC systems without compromising indoor environmental conditions. This study demonstrates that the proposed optimal control settings maintain the indoor environment within the acceptable limit of thermal comfort conditions (indoor air temperature between 19.60 to 28.20C and indoor air humidity between 30 to 65 %RH as per ASHRAE Standard 55-2017) and air quality (CO2 ≤ 800 ppm and VOC ≤ 1000ppm as per Australian Standard AS 1668.2 2016). The outcomes of this research will act as a guideline for energy management practices, not only for energy efficient building design and retrofitting but also for building energy performance analysis. This research provides insight into the aspects that affect the performance of predictive models for indoor temperature. The proposed feature selection approach establishes its efficacy to determine salient and independent input parameters without compromising prediction performance. The application of this approach will minimize the measurement and data storing cost of variables. Further, using fewer numbers of input parameters in the model will reduce the computational cost and time. Thus, the proposed model establishes its applicability in a real system for a more extended period of advanced prediction. In addition, the need to better account for building-occupant interactions as an important step to maintain a healthy indoor environment has been recognized through evaluating a real-life demand control (DCV) system. Lastly, the proposed optimization approach, where four defined environmental parameters are considered simultaneously presents a new outlook within the HVAC control system by eliminating the unseen interface between thermal comfort and IAQ. Overall, this unexploited potential to simultaneously improve the performance of HVAC systems and indoor environmental conditions drives the discussion on reconsidering the set-point configuration standards of HVAC in commercial buildings, either as part of individual building retrofit planning or as part of building regulatory applications.

IOP conference series, Sep 1, 2019

Indoor environmental parameters especially the air temperature have substantial effect on energy ... more Indoor environmental parameters especially the air temperature have substantial effect on energy consumption in commercial buildings and indoor thermal comfort. This study presents a tuning approach of dynamic control strategy of temperature set-point with a view to improving occupants' thermal comfort while simultaneously minimizing energy consumption. To determine optimum temperature set-points in response to ambient conditions, this study investigates the thermal comfort conditions of a commercial building based on real time series data. To quantify thermal environmental conditions for human occupancy, this study uses the graphical comfort zone method proposed by ASHRAE Standard 55-2017 through a rigorous analysis. Based on this analysis the study narrows down the comfort range in the context of seasonal variations and proposes tuning the Master Temperature Set-Points (MTSP) with 4.8 0 C variable linear band between upper and lower temperatures dependent on a simple algorithm. This re-setting strategy of temperature set-point ultimately offers extended lower and upper boundary limit for variable linear band. Extension of linear band for MTSP reduces the gap between temperature set-point and outdoor temperature which ultimately offers less heating and cooling energy consumption. Results show that implementation of this proposed approach would lead to monthly 2707.94 kWh energy savings either from heating or cooling or both during winter and summer season.

Demand response (DR) is widely recognized as an important mechanism in the Australian electricity... more Demand response (DR) is widely recognized as an important mechanism in the Australian electricity market, though large-scale uptake in commercial buildings is yet to occur, in part due to the difficulty of characterising the resource. This paper describes a bottom-up physics-based approach to characterise the DR potential of three types of commercial buildings (schools, offices, and data centres) under a global set-point temperature offset strategy. Representative models are calibrated with energy meter data and parametric analysis is used to assess sensitivity to different building, operating and system parameters. Parametric equations are provided for relative DR potentials as functions of temperature and time of day. School buildings were found to have the highest relative DR potential (~40-45%) for ambient temperatures over 30 • C, followed by data centres (~20-30%) and offices (~20%). Location has the strongest relative influence for school and office buildings and equipment energy intensity for data centres. The Australia-wide combined DR potential for school, office and data centres is estimated to be between 551 and 647 MW. Office buildings have the highest aggregate potential at between 1.5 and 1.7 times that of school buildings and between 9 and 11 times that of data centres.

Energy and Buildings, Nov 1, 2020

Abstract While the research community widely recognizes the importance of post-occupancy measurem... more Abstract While the research community widely recognizes the importance of post-occupancy measurement of buildings to verify performance, requirements of green building certification schemes are highly varied. To assess the effectiveness of building certification schemes during the operation and maintenance stage of certified buildings, this paper critically reviews recent case studies that report on post-certification performance. The review of relevant case studies from the literature reveals some important findings in relation to the performance gap of certified buildings. Subsequently, major operation and maintenance-related building certification schemes are surveyed to reveal the underlying reasons behind this performance gap. Post-certification actions that require post-occupancy data collection and analysis are identified through this survey and compared to highlight their strengths and shortcomings and pinpoint the major discrepancies in data infrastructure and archiving practices that hinder certified buildings in performing according to their design intent. Lastly, suggestions are extracted which may shed light on the re-certification pathways.

2nd International Conference on the Developments in Renewable Energy Technology (ICDRET 2012), 2012

The present research work concerns with the dynamic conditions of Multi S-shaped bladed rotor at ... more The present research work concerns with the dynamic conditions of Multi S-shaped bladed rotor at different Reynolds number. The investigation on wind loading and aerodynamic effects on the four, five and six bladed S-shaped vertical axis vane type rotor has been conducted with the help of an open circuit subsonic wind tunnel. For different bladed rotor the flow velocities were varied from 5m/s to 9m/s covering the Reynolds numbers up to 1.35 × 105. Finally, the nature of predicted dynamic characteristics has been analyzed by comparing with the existing research works.

Environmental Research Letters, 2021

As current action remains insufficient to meet the goals of the Paris agreement let alone to stab... more As current action remains insufficient to meet the goals of the Paris agreement let alone to stabilize the climate, there is increasing hope that solutions related to demand, services and social aspects of climate change mitigation can close the gap. However, given these topics are not investigated by a single epistemic community, the literature base underpinning the associated research continues to be undefined. Here, we aim to delineate a plausible body of literature capturing a comprehensive spectrum of demand, services and social aspects of climate change mitigation. As method we use a novel double-stacked expert—machine learning research architecture and expert evaluation to develop a typology and map key messages relevant for climate change mitigation within this body of literature. First, relying on the official key words provided to the Intergovernmental Panel on Climate Change by governments (across 17 queries), and on specific investigations of domain experts (27 queries),...

Journal of Mechanical Engineering, 2014

In the present research work the dynamic conditions of Multi S-shaped bladed rotor at different R... more In the present research work the dynamic conditions of Multi S-shaped bladed rotor at different Reynolds number have been identified. The investigation on wind loading and aerodynamic effects on the four, five and six bladed S-shaped vertical axis vane type rotor has been conducted with the help of an open circuit subsonic wind tunnel. For different bladed rotor the flow velocities were varied from 5m/s to 9m/s covering the Reynolds numbers up to 1.35 x 105. It was experiential that by increasing the number of blades of rotor to the optimum limit considering all significant factors and at the same time by increasing its Reynolds number, the power output can be increased to its maximum level Finally, the nature of predicted dynamic characteristics has been examined by comparing with the existing research works. DOI: http://dx.doi.org/10.3329/jme.v44i1.19501

Environmental Research Letters

IOP Conference Series: Materials Science and Engineering

Energy Procedia