Dibakar Rakshit

Quantitative assessment of orientation impact on heat gain profile of naturally cooled buildings in India

ABSTRACT This paper reports a comparison of heat gain profile of various types of buildings with different climatic conditions and orientations. The objective of the present analysis is to extend the findings for improving energy performance for energy conservation. The buildings are modelled and simulated as per the guidelines of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Orientation impact on building performance, in terms of heat gain, is examined for all the eight directions, namely North, South, East, West, North East, North West, South East and South West, for four metrological stations where buildings have a higher cooling demand as compared to heating. The stations identified for the study are New Delhi, Jodhpur, Mumbai and Kolkata. The effect of solar exposure on building envelope is studied through heat gain estimation. For the given set of parameters, the best orientation of the building is quantitatively established. The deviation of the best possible orientation from other building orientations is elucidated. The proposed buildings, therefore, have the maximum advantage in terms of the orientation chosen and hence it can be concluded that orientation optimization is the primary step that must be considered in designing an energy-efficient building.

Experimental Study of Tubular Light Pipe System: Influence of Light Reflector on Its Performance

Daylighting is an important passive method of building design in achieving energy savings in buildings. Tubular light pipe system is a modern and innovative technique which utilizes the sunlight to lighten the living space. It is one of the most promising options to provide daylight into deep spaces of not only buildings but also for lighting the road and railway tunnels. The use of light pipe system can save significant amount of energy by providing natural illuminance to interior spaces.

Energy Conservation and Sustainability Due to Passive Daylight System of Light Pipe in Indian Buildings

With continuous increase in energy usage in Indian building sector, share of electricity has risen to 35% of total electricity consumption. Therefore, achieving energy efficiency in buildings by adopting solar passive design strategies is lucrative. It is important to mention that in India, electricity consumption in lighting a commercial building is high and about 25% of the total electricity consumption. It is therefore imperious to evolve techniques that cut down the energy consumption for lighting load and thus develop energy efficient buildings. Tubular light guide is modern and innovative system which can be used to improve illumination for buildings that require more electrical light during daytime. This is done by utilizing the natural light to illuminate the interior space and save a significant amount of lighting energy. The study involves analytical and experimental investigation of a tubular light pipe for prediction of illuminance distribution inside a room of 3 × 3 × 2.7 m3. For this purpose, predictive performance of existing empirical models has been compared with two commercially available software EnergyPlus and Holigilm. The daylight penetration factor (DPF) has been evaluated on the horizontal working plane through available empirical models. The DPF obtained by these empirical models and software is compared with experimental values and is found to have a good agreement. Besides this, annual energy saving potential having windows and light pipe in a room for different Indian climatic conditions has been evaluated.

Thermal Performance Evaluation of Building Roofs Embedded PCM for Multi-climatic Zones

Phase change material (PCM) is used as a thermal energy storage medium in building roofs and walls, which reduces heat gain and temperature fluctuation inside buildings by virtue of latent heat property. Different geographical regions experience different values of climatic parameters such as ambient temperature, sky clearness, intensity of solar radiation, precipitable water quantity. All these parameters affect the thermal performance of the PCM used in a particular geographical region. As the performance of PCM is sensitive to a large number of climatic parameters, estimation of the performance of a PCM in a particular region requires the knowledge of the variation of the thermal performance of PCM with respect to each of the climatic parameters and then computing the performance of the PCM for specific values of the parameters for that region. The estimation of the performance of PCM will be less tedious if the thermal performance can be assessed as a function of a single parameter rather than a set of parameters. This study aims at finding such a composite parameter which alone can determine the thermal performance of PCM in a particular climate. In this study, a mathematical model is developed for the purpose of computing and comparing the thermal performances of three different PCMs in three different climatic conditions. The study specifically focuses on variation of climatic parameters in hot atmosphere where PCM is used to reduce interior heat gain and temperature fluctuation.

Visual Comfort Based Algorithmic Control for Roller Shade and Assessment of Potential Energy Savings

Offices which are mostly operated during day-lit hours are fascinated toward incorporation of solar daylighting systems so as to get benefitted of energy savings along with intangible benefits like good health, well-being, and productivity of their occupants. But discomfort glare is usually ignored in front of rigorous energy load optimization practices and researches, or even if considered, is not properly quantified, which leads to a false evaluation of the performance of daylighting in the context of lighting energy savings. Blinds when operated with optimum visual comfort prevention measures, then only can create a functional day-lit environment. The present study includes modeling and analysis of an east facing office building located in New Delhi, India. It utilizes drafting tool Rhinoceros 3D 5.0 and simulation tool DIVA 4.0 to mathematically analyze the utilization of natural lighting for the office. The analysis includes properly arranged viewpoints similar to that experienced by any occupant, being placed in simulation environment so as to visualize and evaluate realistic glare scenario. The study further deals with the observation and analysis of the illuminance patterns inside the test space and glare values for different blind positions modeled. An algorithm has been developed to analyze the required visual comfort level of the space and suggests an appropriate blind position for every occupancy hour that eventually leads to estimate the potential energy savings through the utilization of daylight. It was observed that even after providing visual comfort to the occupants, the reduction in savings was marginal, measured to be 1% as compared to the case when visual discomfort is overlooked in daylighting utilization.

Evaluation of impact of passive design measures with energy saving potential through estimation of shading control for visual comfort

Residential and commercial buildings together account for one-third of world’s final energy consumption, thus making energy management in buildings of considerable significance. Passive design concept that depends on climate and location can be used as an effective and economical method to reduce the energy consumption in buildings. Seven cities in India, each representative of different geographic and climatic conditions, were selected for analysis. This article studies how the peak cooling and heating load are affected by varying some of the passive design parameters for each of the seven cities. The parameters varied are wall insulation thickness, roof insulation thickness, overhang depth, window orientation, and window-to-wall ratio. Results show that optimized passive design could reduce the peak cooling and heating loads by about 50%. Shading reduces cooling loads but is found to increase heating loads. In some of the locations, both heating in winter and cooling in summer are needed and designers should adopt appropriate passive measures depending on the location. Also for the same building, evaluation of shading is done in the context of lighting energy savings. An algorithm has been developed to iteratively alter and analyze set of roller blind positions to maintain visual comfort; as a result, the corresponding potential annual energy savings due to lighting were estimated. It was also observed that even after providing visual comfort to the occupants, energy savings only reduced by approximately 1% as compared to the case when visual comfort was overlooked.

Characterization of Interfacial Mass Transfer Rate of Stored Liquids

A thermodynamic analysis of the two-phase physics involving a liquid–vapor combination has been studied under the regime of conjugate heat and mass transfer phenomena. An experiment has been designed and performed to estimate the interfacial mass transfer characteristics of a liquid–vapor system by varying the liquid temperature. The experimental setup consists of an instrumented tank partially filled with water and maintained at different temperatures. The evaporation of liquid from the interface and the gaseous condensation has been quantified by calculating the interfacial mass transfer rate for both covered and uncovered tanks. The dependence of interfacial mass transfer rate on the liquid–vapor interfacial temperature, fractional concentration of the evaporating liquid, the surface area of the liquid vapor interface, and the fill level of the liquid has been established through the present experimental study. An estimation of the overall mass transfer rate from the interface due to a concentration gradient shows an analogy with the multiphase heat transfer that takes place across the interface due to temperature gradient. It was seen that at low fill levels and with a temperature difference of about 30 °C between liquid and ullage, the mass transfer rate of a closed system was nearly doubled when compared to its open system counterpart.