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Energy performance of room air-conditioners and ceiling fans in mixed-mode buildings (2023)

Journal: Energies, Volume 16, Issue 19

Authors: Sriraj Gokarakonda, Christoph Van Treeck, Rajan Rawal, Stefan Thomas

Abstract: Studies show that people can tolerate elevated temperatures in the presence of appreciable air movement (e.g., from using ceiling

Keywords: room air-conditioners; ceiling fans; set-point temperature; thermal comfort; user behaviour; sensors and monitoring

Energy performance of room air-conditioners and ceiling fans in relation to thermal comfort (2023)

Journal: Energy and Built Environment, Volume 4, Issue 6

Authors: Sriraj Gokarakonda, Christoph Van Treeck, Rajan Rawal, Stefan Thomas

Abstract: Studies show that people can tolerate elevated temperatures in the presence of appreciable air movement (e.g., by using ceiling fans). This results space cooling

Keywords: Room air-conditioners; Ceiling fans; Set point temperature; Thermal comfort

Validated open-source Modelica model of direct evaporative cooler with minimal inputs (2022)

JournalJournal of Building Performance Simulation, Volume 15, Issue 6

AuthorsSaranya Anbarasu, Wangada Zuo, Yangyang Fu, Yash Shukla, Rajan Rawal

AbstractDirect evaporative coolers (DECs) are a low-energy cooling alternative to conventional air conditioning in hot-dry climates. The key component of DEC is the cooling pad, which evaporatively cools the air passing through it. While detailed numerical models of heat and mass transfer have been proposed for the cooling pad, these require many input parameters that are not readily accessible. Alternatively, simplified models lack accuracy and are confined to common types of cooling pad. To address these limitations, we developed and validated a physics-based model, that only needs the nominal data to compute the heat and mass transfer with considerable accuracy. The proposed model is implemented in Modelica, an equation-based object-oriented modeling language. For comparison, a basic lumped model from EnergyPlus based on the efficiency curve of the cooling pad is also implemented. The physics-based model exhibits <2% error from the experimental data and the lumped model exhibits a 12.3% error.

Keywordsdirect evaporative cooler, modelica, physical-based model

Adaptive thermal comfort model based on fields studies in five climate zones across India (2022)

JournalBuilding and Environment. Volume 219

AuthorsRajan Rawal, Yash Shukla, Vishnu Vardhan, Sneha Asrani, Marcel Schweiker, Richard de Dear, Vishal Garg, Jyotirmay Mathur, Sanjay Prakash, Saurabh Diddi, Vikash Ranjan, Abdullah N.

AbstractIndian residences are vulnerable to heat-driven discomfort amid the mounting prevalence of weather extremes, residential design and construction practices, and densifying urbanscapes. Therefore, it is vital to understand the thermal comfort characteristics of nationwide residences. This study proposes an adaptive thermal comfort model based on yearlong field surveys in eight cities located across five climate zones of India – the India Model for Adaptive Comfort - Residential (IMAC-R). The model prescribes the operative temperature bands for 80% and 90% thermal acceptability in correlation with the outdoor reference temperature, applicable to mixed-mode (MM) and naturally ventilated (NV) residences.

More than 80% of the Indian residential occupants experienced a neutral thermal sensation in the indoor operative range of 16.3–35 °C in response to a 5.5–33 °C variation in the 30-day outdoor running mean temperature. Comparing the proposed model with the PMV model revealed that the latter underpredicts the thermal adaptivity of Indian occupants. The model was also compared against its predecessor – India Model for Adaptive Comfort for Commercial Buildings (IMAC MM and NV), along with relevant global and regional thermal comfort models. On average, the neutral temperature prescribed by IMAC-R was warmer than the temperatures prescribed by IMAC MM and NV by 2.9 °C and 2.1 °C, respectively; it was also warmer than the temperature prescribed by the recent ASHRAE-55 and EN 16798-1 models by 2 °C and 0.3 °C, respectively. IMAC-R reserves the prospect of addressing the thermal comfort needs of the national population while paving the way for long-term energy savings and climate action.

Keywords: Thermal adaptation; Adaptive comfort model; Indian residences; Mixed-mode ventilation; Natural ventilation; IMAC

Alternatives to air-conditioning: policies, design, technologies, behaviours (2022)

Journal: Buildings and Cities, Volume 3, Issue 1

Authors: Brian Ford, Dejan Mumovic, Rajan Rawal

Abstract: Far from being a panacea, air-conditioning is shown to create social, environmental and economic problems. Alternatives to air-conditioning are identified as

Keywords: Adaptation air-conditioning, climate change, cooling, design, energy demand,, environmental control, passive cooling, public policy, thermal comfort

Emissions from a net-zero building in India: life cycle assessment (2022)

Journal: Buildings & Cities, Volume 3, Issue 1

Authors: Mili Jain, Rajan Rawal

Abstract: This study quantifies the gap between net-zero energy and net-zero carbon through a life cycle assessment (LCA) of a net-zero energy building (NZEB) in Ahmedabad,

Keywords: Buildings; carbon footprint;embodied carbon; life cycleassessment; net-zero carbon;net-zero energy; India

Integrating low energy cooling and ventilation strategies in Indian residences (2022)

Journal: Buildings and Cities, Volume 3, Issue 1

Authors: Malcolm Cook, Yash Shukla, Rajan Rawal, Charalampos Angelopoulos, Luciano Caruggi-De-Faria, Dennis Loveday, Eftychia Spentzou, Jayamin Patel

Abstract: Rapidly developing economies of countries in hot climates

Keywords: control cooling, dwellings, energy, mixed mode, residential, thermal comfort, ventilation, India

Experimental investigation on hygrothermal behaviour of cement and lime plaster (2022)

Journal: Building and Environment, Volume 217

Authors: Rashmin Damle, Nikita Khatri, Rajan Rawal 

Abstract: Traditional buildings since many centuries have used lime as a binder and finishing material. However, in contemporary construction practices, lime mortar and lime

Investigating Optimum Cooling Set Point Temperature And Air Velocity For Thermal Comfort And Energy Conservation In Mixed-Mode Buildings In India (2022)

Journal: Energies, Volume 15, Issue 6

Authors: Sriraj Gokarakonda, Christoph van Treeck, Rajan Rawal

Abstract: In warm and hot climates, ceiling fans and/or air conditioners (ACs) are used to maintain thermal comfort. Ceiling fans provide air movement near the skin, which enhances the evaporation of sweat, reduces heat stress, and enhances thermal comfort. This is also called the cooling effect. However, AC usage behaviour and the effects of elevated air speed through the use of ceiling fans on indoor operative temperature during AC usage are not widely studied. This study investigated the optimum AC (cooling) set point temperature and air velocity necessary for maintaining thermal comfort while achieving energy conservation, in mixed-mode buildings in India, through field studies by using used custom-built Internet of Things (IOT) devices. In the current study, the results indicate a 79% probability that comfort conditions can be maintained by achieving a temperature drop of 3K. If this drop can be achieved, as much as possible, through passive measures, the duration of AC operation and its energy consumption are reduced, at least by 67.5 and 58.4%, respectively. During the air-conditioned period, there is a possibility that the cooing effect is reduced because of increase in operative temperature due to ceiling fan operation. Therefore, the optimum solution is to maintain the highest AC set point and minimum fan speed setting that are acceptable.

Keywords: elevated air speed; thermal comfort; mixed-mode buildings; set point temperature; energy consumption in buildings

Thermally Comfortable Affordable Housing: A Study on Residential Building Code in India (2022)

Journal: The Journal of Engineering Research (TJER), Volume 18, Issue 2

Authors: Sneha Asrani, Rajan Rawal, Yash Shukla, Peter Graham, Priyanka Bhanushali, Arjun Desai

Abstract: On an average, India has more than 3000 Cooling Degree Days (CDD).

Assessing A Fit-For-Purpose Urban Building Energy Modelling Framework With Reference To Ahmedabad (2021)

Journal: Science and Technology for the Built Environment

Authors: Anmol Mathur, Pamela Fennell, Rajan Rawal, Ivan Korolija

Abstract: Urban building energy models (UBEM) are driving sustainable design and operations of cities by combining urban datasets with energy simulations. UBEMs are developed from a range of inputs on the spatial and semantic details of the buildings, and the systems affecting their energy performance. Large geographical scales with finer spatio-temporal details increase the challenges of data processing for a reliable UBEM. Thus, it is essential to understand the impact of increasing the resolution of model inputs on the outputs to balance the efforts spent on model development, filling data gaps and maintaining the reliability of the results. This research introduces a Fit-for-Purpose modelling strategy and extends the concept of Levels of Detail (LoD) used for 3D models, to UBEM characteristics including occupancy, geometry, context, modelling methodology, and calibration with the proposed model characterisation framework. A case study based on a 0.3km2 area of Ahmedabad, India, is presented to demonstrate the framework. The results highlight a need for a higher LoD in occupancy modelling for the residential and educational buildings, whereas a higher LoD is more important for the commercial buildings’ envelope characteristics. These insights will enable a highly targeted supplementary data collection approach for the UBEM of the entire city.

Performance metrics for room air-conditioners: energy, comfort and environmental impacts (2021)

Journal: Building and Cities, Volume 2, Issue 1

Authors: Nidhi Rai Jain, Rajan Rawal, Vishnu Vardhan, Shubhashis Dey

Abstract: India’s current standards and labels for room air-conditioners (RACs) account for energy efficiency, but omit other important criteria that could influence product development and

The Colours Of Comfort: From Thermal Sensation To Person-Centric Thermal Zones For Adaptive Building Strategies (2020)

Journal: Energy and Buildings, Volume 216
Himani PandyaRajan Rawal, Federico Tartarini, Rohit Upadhyay, Andreas Wagner
Abstract: Thermal comfort research has been traditionally based on cross-sectional studies and spatial aggregation of individual surveys at building level. This research design is susceptible to compositional effects and may lead to error in identifying predictors to thermal comfort indices, in particular in relation to adaptive mechanisms. A relationship between comfort and different predictors can be true at an individual level but not evident at the building level. In addition, cross-sectional studies overlook temporal changes in individual thermal perception due to contextual factors. To address these limitations, this study applied a longitudinal research design over 8 to 21 months in eight buildings located in six countries around the world. The dataset comprises of 5,567 individual thermal comfort surveys from 258 participants. The analysis aggregated survey responses at participant level and clustered participants according to their thermal sensation votes (TSV). Four TSV clusters were introduced, representing four different thermal sensation traits. Further analysis reviewed the probability of cluster membership in relation to demographic characteristics and behavioural adaptation. Finally, the analysis at individual level enabled the introduction of a new metric, the thermal zone (Zt), which in this study ranges from 21.5 °C to 26.6 °C. The thermal sensation traits and person-centric thermal zone (Zt) are a first step into the development of new metrics incorporating individual perceived comfort into dynamic building controls for adaptive buildings.

Personal Comfort Systems: A Review On Comfort, Energy, And Economics (2020)
Journal: Energy and Buildings, Volume 214
Authors: Rajan Rawal, Marcel Schweiker, Ongun Berk Kazanci, Vishnu Vardhan, Quan Jin, Lin Duanmu
Abstract: Conventional heating, ventilation, and air-conditioning (HVAC) systems are designed to condition the entire building volume. In contrast, Personal Comfort Systems (PCS) target conditioning

A Framework For Adopting Adaptive Thermal Comfort Principles In Design And Operation Of Buildings (2019)

Journal: Energy and Buildings, Volume 205
Authors: Runa T. Hellwig, Despoina Teli, Marcel Schweiker, Joon-Ho Choi, M.C. Jeffrey Lee, Rodrigo Mora, Rajan Rawal, Zhaojun Wang, FarahAl-Atrash
Abstract: The concept of adaptive thermal comfort was formulated many decades ago and has been validated in numerous field studies. As a result, wider acceptable indoor temperature ranges based on adaptive models have been included in international and national standards and the adaptive approach to thermal comfort is regarded as a significant contributor in achieving low energy building design and operation. Despite the ever-increasing scientific literature on adaptive comfort around the world, the overall understanding of how to translate the adaptive principles into design practice and concepts for operating buildings is still limited, which suggests a gap between the scientific outcomes and the real-world applications. This discussion paper identifies the challenges and gaps in using the principles of adaptive thermal comfort by design practitioners and discusses them in light of relevant research findings. More than 100 literature sources were reviewed in support of the discussion. The paper then proposes a framework that aims to facilitate the adoption of adaptive comfort principles in design and operation of buildings and describes the outline of an imminent guideline for low energy building design based on the concept of adaptive thermal comfort.

A Study Of Indoor Thermal Parameters For Naturally Ventilated Occupied Buildings In The Warm-Humid Climate Of Southern India (2019)

Journal: Building and Environment, Volume 151
Vishnu VardhanSanyogita Manu, Gail Brager, Rajan Rawal
Abstract: The ever-increasing demand for built spaces to cater to the needs of the tropical population compels for the adoption of sustainable building forms and passive design strategies. This research aims at studying the cases of six naturally ventilated occupied buildings constructed in the tropical ‘warm and humid’ climate of Pondicherry and Auroville, India. The buildings were subjected to long-term data logging and sporadic hand-held measurements. Indoor parameters of air temperature (Ta), surface temperature (Ts), and relative humidity (RH) across six living spaces, eight roof assemblies, and six passive design strategies were logged on an hourly basis and analysed for the hottest and coldest months. In order to estimate the thermal comfort, Ta readings of the most occupied zones were compared against ASHRAE-55 adaptive thermal comfort model and India Model for Adaptive Comfort (IMAC) temperature limits. This research showed that the hourly averaged Ta and RH in the six naturally ventilated spaces at the hottest summer hour (13:00) was between 31.0 and 33.2 °C and 56.0–69.0% while the outdoors were at 36.9 °C and 43.3% respectively. The hourly averaged rooftop and ceiling Ts for the unshaded roofs at 14:00 h during peak summer was between 53.0-43.4 °C and 36.6–31.0 °C respectively, while a shaded roof had a rooftop and ceiling Ts of 34.5 °C and 31.9 °C respectively. The passive design strategies of exposed cavity walls, night ventilation, and optimised building forms were found to be the most effective. The number of uncomfortable hours predicted by the ASHRAE model were found to be 93.4% higher than those by IMAC.

Performance Evaluation Of Climate Responsive Buildings In India – Case Studies From Cooling Dominated Climate Zones. Building And Environment (2019)
Journal: Building and Environment, Volume 148
Authors: Sanyogita Manu, Gail Brager, Rajan Rawal, Angela Geronazzo and Devarsh Kumar
Abstract: India has a rich

Influence Of Building Design And Control Parameters On The Potential Of Mixed-Mode Buildings In India (2019)

Journal: Building and Environment, Volume 148
Authors: Sriraj Gokarakonda, Christophvan Treeck, Rajan Rawal
Abstract: The potential of mixed-mode office buildings with varying design and control parameters is examined by using an uncertainty analysis in the three climate zones of India. The analysis is in terms of cooling energy consumption, thermal comfort conditions, and natural ventilation hours. Furthermore, influential parameters are identified using sensitivity analysis. In this study, opening the windows enables natural ventilation. Night-time ventilation through the windows is not enabled because these are mostly closed at night. A maximum natural ventilation of 10% of the total building occupancy hours are observed in warm and humid, and hot and dry climates; however, they are slightly higher in the composite climate. A further increase in the number of natural ventilation hours leads to an increase in the occupancy hours outside the Indian Model for Adaptive Comfort model for mixed-mode buildings with at least 90% of occupants are satisfied. There are no occupancy hours outside of 80% of occupants are satisfied. The choice of thermal comfort band is crucial for determining the potential of mixed-mode buildings. The cooling setpoint temperature, building size, window solar heat gain coefficient, and surface properties of exterior surfaces are identified as the more influential parameters than the thermophysical properties of building envelope constructions. Although the building envelope which is in compliance with the Energy Efficient Building Code of India increases energy efficiency during air-conditioning periods, whether it reduces natural ventilation hours, because of overheating during such period remains to be determined.

A Review Of Advances For Thermal And Visual Comfort Controls In Personal Environmental Control (PEC) Systems (2019)
Journal: Intelligent Buildings International, Volume 11, Issue 2
Authors: Sam Babu Godithi, Enna Sachdeva, Vishal Garg, Richard Brown, Christian Kohler, Rajan Rawal
AbstractThe buildings are conventionally operated to maintain homogeneous indoor ambient conditions to maintain comfortable thermal and visual environments. However, maintaining these homogeneous conditions throughout the building leads to unnecessary energy consumption, and does not address the varying thermal and visual comfort needs of the individual occupants. This has led the building science community to pursue personal environmental control (PEC) systems that work in tandem with adaptive centralized ambient comfort systems. These PEC systems create favorable environmental conditions around each occupant, employing specialized equipment, such as a personal thermal conditioning system, task lighting, plug load monitoring and control, window shade control system, and similar systems. Coordinating among personal control systems and with centralized building management systems allows the optimal provision of services such as cooling, lighting, and other such services where they are needed, potentially leading to significant energy efficiency and improved occupant satisfaction.
This paper provides an overview of the state of research associated with personalized thermal conditioning and lighting systems. In addition, presents a survey of controls and communication systems that operate these devices. Finally, the paper considers the energy savings potential from a personal thermal comfort and lighting comfort.

Low Energy Cooling And Ventilation In Indian Residences (2018)

Journal: Science and Technology for the Built Environment, Volume 24, Issue 8
Authors: Malcolm Cook and Rajan Rawal

Achieving The 2°C Goal: The Potential Of India’s Building Sector (2018)
Journal: Building Research & Information, Volume 47, Issue 1
Authors: Peter Graham and Rajan Rawal
Abstract: India’s growth of energy demand in the building stock, and efforts to curb it, are placed into an international

Thermal Characterization Of Full-Scale PCM Products And Numerical Simulations, Including Hysteresis, To Evaluate Energy Impacts In An Envelope Application (2018)
Journal: Applied Thermal Engineering, Volume 138
Authors: Kaushik Biswas, Yash Shukla, Andre Desjarlais, Rajan Rawal
Abstract: This article presents combined measurements of fatty acid-based organic PCM products and numerical simulations to evaluate the energy benefits of adding a PCM
The simulations were done using a previously-validated two-dimensional (2D) wall model containing a PCM layer and incorporating the HFMA-measured enthalpy functions. The wall model was modified to include the hysteresis phenomenon observed in PCMs, which is reflected in different melting and freezing temperatures of the PCM. Simulations were done with a single enthalpy curve based on the PCM melting tests, both melting and freezing enthalpy curves, and with different degrees of hysteresis between the melting and freezing curves. Significant differences were observed between the thermal performances of the modeled wall with the PCM layer under the different scenarios.

Development Of The ASHRAE Global Thermal Comfort Database II (2018)
Journal: Building and Environment, Volume 142
Authors: Veronika Földváry, Toby Cheung, Hui Zhang, Richard de Dear, Thomas Parkinson, Edward Arens, Chungyoon Chun, Stefano Schiavon, Maohui Luo, Gail Brager, Peixian Li, Soazig Kaam, Michael A Adebamowo, Mary M Andamon, Francesco

Packaged Scalable Energy Information Systems For Hotels (2018)
Journal: Journal of Facilities Management, Volume 16, Issue 2
Authors: Reshma Singh, Paul Mathew, Jessica Granderson, Yash Shukla, Amiya Ranjan Behera
A five-step approach was followed: 1. Identifying business drivers as key determinants for hotel sector-specific packages 2. Addressing heterogeneity to develop standardized, tiered packages 3. Determining performance metrics for key stakeholders 4. Recommending streamlined data architecture 5. Developing visualization enabling insights and actions.
Technical specifications for two tiers (entry and advanced) of EIS packages for hotels have been developed. EIS vendor, integrator, and client organization’s facilities and IT staff have been considered as key stakeholders. Findings from six field demonstrations show benefits of (i) cost-effectiveness, through reduced transactional, first, and operational costs, (ii) scalability, by accommodating heterogeneity across the building sub-sector, (iii) simplicity, by integrating meters, gateways, and software in the package, and (iv) actionability in organizations, across various decision making levels.
Building owners and operators can use these specifications to ease procurement and installation of EIS in their facilities. EIS software vendors can use them to develop new product offerings for underserved sectors.

Energy Appliance Transformation In Commercial Buildings In India Under Alternate Policy Scenarios (2017)
Journal: Energy, Volume 140, Part 1
Authors: Amit Garg, Jyoti Maheshwari, P.R. Shukla, and Rajan Rawal
Abstract: The total electricity consumption from commercial sector was about 9% during 2013–14 in India. Load research survey was carried out to study the usage patterns for all types of electric appliances used in commercial establishments at income, appliance and end-use levels in Gujarat state of India – one of the most progressive states. Penetration level of efficient appliances, electricity load curves and Energy Performance Index (EPI) were estimated. The mean EPI was 98 kWh/m2/year (SD = 105.5) for surveyed small commercial establishments (low income) while mean EPI was 181 kWh/m2/year (SD = 68) for surveyed large commercial establishments (Malls). Electricity saving potentials was estimated if electric appliances at these commercial establishments were replaced with efficient appliances. Four alternate scenarios were analyzed using cost of conserved energy (CCE) curves with various efficiency enhancement options – following at least commercial sub-category level median EPIs, following average EU equivalent EPI levels, following average EPI levels of equivalent US commercial establishments, and following the best available technologies (BAT). The average energy savings ranged between 14% and 25% across buildings and scenarios. Energy efficient air-conditioner and LED lights offer the highest energy savings potential among appliances.

Transient Three-Dimensional CFD Modelling Of Ceiling Fans (2017)

Journal: Building and Environment, Volume 123

Authors: Francesco Babich, Malcolm Cook, Dennis Loveday, Rajan RawalYash Shukla
Abstract: Ceiling fans have been used for decades as a means of providing thermal comfort in tropical countries such as India. However, recent years have witnessed a significant increase in the use of air conditioning as a means to achieve comfort, and therefore in the total energy consumption and related CO2 emissions. Ceiling fans are still viable options to limit use of air conditioners or in combination with air conditioners without compromising on thermal comfort and still achieving energy savings. Ceiling fans generate non-uniform velocity profiles, and therefore relatively non-uniform thermal environments, whose characteristics may be tough to analyse with simple modelling methods. This issue can be investigated using CFD. However, to date, there are few works on ceiling fans, CFD and thermal comfort. More accurate models are therefore required to predict their performance. The research presented in this paper aimed to develop and validate a three-dimensional transient implicit CFD model of a typical ceiling fan available in India by comparing simulation results obtained using different URANS turbulence models with measured data collected in controlled environment. The results highlight that this ceiling fan model is able to replicate the predominant characteristics of the air flow generated by the fan such as the meandering plume and the local fine free shear layers. The best results are achieved when the SST k-ω turbulence model is used, with 83% of the simulated values being within the error bars of the respective measured value.
Keywords: Ceiling fan, Thermal comfort, CFD validation, Turbulence modelling, India, Environmental chamber

Field Studies Of Thermal Comfort Across Multiple Climate Zones For The Subcontinent: India Model For Adaptive Comfort (IMAC) (2016)
Journal: Building and Environment, Volume 98
Authors: Sanyogita Manu, Yash Shukla, Rajan Rawal, Leena E.Thomas, Richard de Dear
Abstract: India is witnessing unprecedented growth trends in building construction, particularly office spaces. Indian offices
Occupants in naturally ventilated Indian offices were found to be more adaptive than the prevailing ASHRAE and EN models would suggest. According to the IMAC model, neutral temperature in naturally ventilated buildings varies from 19.6 to 28.5 °C for 30-day outdoor running mean air temperatures ranging from 12.5 to 31 °C. This is the first instance where a study proposes a single adaptive model for mixed mode buildings asserting its validity for both naturally ventilated and air-conditioned modes of operation in the building, with neutral temperature varying from 21.5 to 28.7 °C for 13–38.5 °C range of outdoor temperatures. For air-conditioned buildings, Fanger's static PMV model was found to consistently over-predict the sensation on the warmer side of the 7-point sensation scale.
Keywords: Indian office buildings, Fanger PMV, Adaptive thermal comfort, Adaptive model, Neutral temperature, Comfort standards

Impact Of Vegetation And Building Height On Urban Ambient Temperature In Hot And Dry Climate (2011)

Journal: Journal of Habitat Engineering, Volume 3, Issue 2
: Jalpa Gandhi, Rajan Rawal

Supported by:

Ministry of New and Renewable Energy Govt. of India, Gujarat Energy Development Agency, U.S. Agency for International Development iNDEXTb (Industrial Extension Bureau) Govt. of Gujarat, Shakti Sustainable Energy Foundation, New Delhi