D.G. Leo Samuel

Bio: D.G. Leo Samuel is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Passive cooling & Thermal comfort. The author has an hindex of 6, co-authored 11 publication(s) receiving 194 citation(s). Previous affiliations of D.G. Leo Samuel include Motilal Nehru National Institute of Technology Allahabad.

Passive alternatives to mechanical air conditioning of building: A review

Abstract: Human comfort is gaining importance in the recent decades. Mechanical air conditioners are conventional means of creating thermal comfort but they are energy intensive and hence harmful to ecological system. Therefore passive cooling can be adopted as a viable alternative to conventional cooling system. This paper reviews various passive cooling options available such as nocturnal radiation, geothermal, ventilation, evaporative, hydrogeothermal, deep ocean/lake, thermal insulation and shading along with their advantages, limitations, working principles and climatic dependence. The mathematical equations used for computing the performance of passive cooling systems have been discussed along with design and environmental parameters influencing the systems' performance. The usefulness of phase change materials, thermal mass and radiant cooling in passive cooling systems is also examined. Case studies containing experimental data and numerical predictions are discussed to provide options for building architects and infrastructure developers to adopt the appropriate passive cooling strategy. In addition, issues related to occupants' health and indoor air quality are also explained. A brief review of energy-efficient and eco-friendly solar cooling systems is also included.

Thermal comfort in traditional buildings composed of local and modern construction materials

Abstract: In recent years, there is a renewed interest towards the passive cooling features of ancient building architectures, which are cost effective, eco-friendly and best suited for the local climate. On the other hand, the modern construction materials, such as cement and steel, are highly durable. Thermal comfort of eight vernacular buildings that use modern construction materials to improve the structural durability was monitored in July 2014. The buildings are located in Hyderabad, India. They have many passive cooling features that include air cavities in the structures to reduce heat transfer, high thermal mass to reduce temperature fluctuation and induced ventilation to remove heat from the indoor. All the passive cooling features investigated were found to have an appreciable influence on the thermal comfort of the indoor space. The ventilated air gaps in the roof reduced the average temperature of the roof interior surface by 1.2 °C. The diurnal temperature fluctuation of the indoor air reduced by 0.9 °C in a building with a higher thermal mass compared to a building with thin walls and roof. All the eight buildings were found to be comfortable most of the time with a slight discomfort during late night and morning hours. The maximum CO 2 recorded was 550 ppm. This indicates that the buildings were adequately ventilated.

Simulation of indoor comfort level in a building cooled by a cooling tower–concrete core cooling system under hot–semiarid climatic conditions:

Abstract: Concrete core cooling system is an energy efficient alternative to the conventional mechanical cooling system. It provides better comfort due to direct absorption of radiation load, low indoor air velocity, apt vertical temperature gradient and absence of noise. It can be operated at relatively higher water temperature, which facilitates the use of passive cooling strategies. In this study, a cooling tower, which is an ‘evaporative cooling system’, is preferred over other passive cooling options due to its better cooling performance in dry regions and its ability to operate all through the day. This paper presents the results of computational fluid dynamic analysis of a room cooled by concrete core cooling system supported by a cooling tower. The study reveals that for a typical hot–semiarid summer climatic condition in India, the system reduces the average indoor air temperature to a comfortable range of 23.5 to 28℃ from an uncomfortable range of 35.3 to 41℃ in a building without cooling. The average pre...

Feasibility analysis of passive thermally activated building system for various climatic regions in India

Abstract: Thermally activated building system (TABS) is a hydronic cooling system, in which cold water is circulated through pipes embedded in the building structure to remove the heat from the indoor space. This paper proposes a hybrid passive cooling system, in which TABS is integrated with a cooling tower. The performance of this integrated system greatly depends on the climatic conditions of the geographical area. Hence, the feasibility of the proposed system to provide thermal comfort in twelve Indian cities spread over five different climatic regions is investigated using COMSOL Multiphysics. Different cooling scenarios like Roof and Floor cooled TABS (RF) and All Surfaces cooled TABS (AS) are compared. The proposed system performs well in arid and semi-arid regions, and the RF scenario is sufficient to achieve thermal comfort. The system is able to reduce the indoor operative temperature by 14 °C for the arid climatic conditions of Jaipur. In the other three regions, i.e., humid subtropical, tropical wet and dry and tropical wet regions, the performance of the proposed system is relatively low and the AS scenario is required to achieve thermal comfort.

Parametric analysis on the thermal comfort of a cooling tower based thermally activated building system in tropical climate – An experimental study

Abstract: Thermally Activated Building System (TABS) provides not only better thermal comfort but also good indoor air quality. It can be coupled with passive cooling systems as it can operate at a relatively higher water temperature. Even though TABS is a promising energy-efficient and eco-friendly system, the influences of various design and operating parameters on the indoor thermal comfort of a building with TABS are not well understood. Hence, the influences of cooling surfaces (area), shading, natural ventilation and ceiling fan on the performance of cooling tower based TABS were investigated in an experimental room of dimensions 3.5 m × 3.5 m × 3.15 m. The increase in the number of cooling surfaces decreased (favourable) the thermal comfort indices and advanced the time at which their maximum and minimum were reached. The average predicted percentage of dissatisfied was 89% if roof alone was cooling. This reduced to 20% if all the surfaces of the building were cooled. Shading of the roof reduced the maximum operating temperature of the indoor space by 0.9 °C when all the surfaces of the building were cooled with TABS. The use of ceiling fan increased the indoor operative temperature marginally. However, the increase was less than the neutral temperature offset of 2.6 °C that was achieved by higher air movement. Thus, the use of the fan results in a better indoor thermal comfort. Natural ventilation advanced the occurrence of the maximum temperature of indoor air by 1½ and 2¾ hours for fan off and fan on cases respectively. It also advanced the extrema of the other indoor comfort parameters. The cooling tower based TABS was able to achieve thermal comfort even in unfavourable warm and humid tropical climates under certain operating conditions.

Radiative Cooling: Principles, Progress, and Potentials

Abstract: The recent progress on radiative cooling reveals its potential for applications in highly efficient passive cooling. This approach utilizes the maximized emission of infrared thermal radiation through the atmospheric window for releasing heat and minimized absorption of incoming atmospheric radiation. These simultaneous processes can lead to a device temperature substantially below the ambient temperature. Although the application of radiative cooling for nighttime cooling was demonstrated a few decades ago, significant cooling under direct sunlight has been achieved only recently, indicating its potential as a practical passive cooler during the day. In this article, the basic principles of radiative cooling and its performance characteristics for nonradiative contributions, solar radiation, and atmospheric conditions are discussed. The recent advancements over the traditional approaches and their material and structural characteristics are outlined. The key characteristics of the thermal radiators and solar reflectors of the current state-of-the-art radiative coolers are evaluated and their benchmarks are remarked for the peak cooling ability. The scopes for further improvements on radiative cooling efficiency for optimized device characteristics are also theoretically estimated.

A 50 year review of basic and applied research in radiant heating and cooling systems for the built environment

Abstract: The radiant heating and cooling (RHC) system has been gaining much popularity due to high thermal comfort, reduced energy consumption, quiet operation, space saving, and so on. For this reason, there have been numerous studies on the RHC system to evaluate the thermal performance of the system and to implement the system for practical applications. This study conducted a literature review on the basic and applied research in RHC systems for the built environment. The objective of this review is to find out the research trend of the RHC system, to discover main issues for the RHC system understanding, and to suggest further studies for the system development. In this study, a comprehensive review was conducted, in terms of thermal comfort, thermal analysis including heat transfer model, heating/cooling capacity, CFD analysis, energy simulation, system configuration and control strategies. The results showed that the RHC system has been continuously developed, modified and improved to achieve better thermal comfort and energy efficiency. Based on the review results, several topics for future studies were suggested, which are required to overcome the limitations of the RHC system for extending its application to various building types, climate, and so on.

The contextual factors contributing to occupants' adaptive comfort behaviors in offices – A review and proposed modeling framework

Abstract: Occupants play an unprecedented role on energy use of office buildings and they are often perceived as one of the main causes of underperforming buildings. It is therefore necessary to capture the factors influencing these energy intensive occupant behaviors and to incorporate them in building design. This review-based article puts forward a framework to represent occupant behavior in buildings by arguing: occupants are not illogical and irrational but rather that they attempt to restore their comfort in the easiest way possible, but are influenced by many contextual factors. This framework synthesizes statistical and anecdotal findings of the occupant behavior literature. Furthermore, it lends itself to occupant behavior researchers to form a systematic way to report the influential contextual factors such as ease of control, freedom to reposition, and social constraints.

Eco-efficient construction and building materials research under the EU Framework Programme Horizon 2020

Abstract: With an overall budget of around 70,000 million € for the next seven years (2014–2020) the EU Framework Programme for research and Innovation-Horizon 2020 constitutes the most important financial instrument for research and innovation in the world. Sustainable development is of paramount significance for Horizon 2020 through climate action and resource efficiency, which will represent at least 60% of the overall budget. This sustainability focus could have a strong impact on the future of the European construction industry and also being an opportunity for the development and commercialization of eco-efficient construction and building materials. This article addresses the case of materials for energy efficiency and materials capable of reusing a high waste content. Nanotech energy efficiency related building materials has the potential to become a hot research area being promoted and funded as a Key Enabling Technology-KET.

A review of clear sky radiative cooling developments and applications in renewable power systems and passive building cooling

Abstract: Although nocturnal radiative cooling has been known for centuries, providing sub-ambient radiative cooling during daytime was a challenge until recent years Recent advances in nano-fabrication technologies, have made it possible to manufacture structures with tailored radiative properties for various energy applications like daytime clear sky radiative cooling It has been shown that photonic and plasmonic selective emitters can be tuned efficiently to emit heat through clear sky to the outer space and cool terrestrial objects providing passive cooling There is a renewed interest in clear sky radiative cooling among researchers Providing continuous day and night sub-ambient cooling and dissipation of low grade heat from renewable power systems without use of water or external energy under direct sunlight and other applications have made clear sky radiative cooling a hot research topic This paper reviews relevant publications on clear-sky radiative cooling methods An overview of radiative cooling fundamentals and a detailed literature survey of published studies on selective emitter structures for daytime and nighttime cooling purposes is presented Furthermore, a detailed energy analysis is performed identifying key performance indicators and evaluating the cooling performance under various conditions Findings from studies that have used empirical equations for numerical energy analysis and selective emitter structure designs for daytime and nighttime applications are summarized in tables for easy comparison