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It has been shown by many researchers that over a long term there has been a slow but steady rise of ambient temperature within the Indian sub-continent. Due to an increased economic prosperity there has been an accompanied increase in the urban heat island effect. Furthermore, urbanisation of large cities in India has also led to higher population...
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... 'Heat Balance (HB) Method' for obtain- ing cooling load involves calculating a surface- by-surface conductive, convective and radiative heat balance for each room surface and a con- vective heat balance for the room air. The Radiant Time Series (RTS) method is a simpli- fied method for performing design cooling load calculations that is derived from the heat bal- ance method. It replaces the historical 'transfer function' method that was used by ASHRAE for several decades. Figure 7 presents a synopsis of the ASHRAE procedure for obtaining build- ing cooling load. Note that one of the essential element in this regard is the knowledge of sol-air temperature for the opaque elements of the building ...
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... Dominguez et al. (2011) found that photovoltaic arrays can reduce roof temperatures by up to 2.5 K, achieving a 38% reduction in annual cooling. Similarly, Kotak et al. (2014) showed that cooling products provided savings of up to 34.8% in an Indian city, with roof cooling loads falling from 73 to 90% after PV installation. In hot and dry climates such as Saudi Arabia, Zubair et al. (2018) reported energy savings of up to 23% in cooling products, demonstrating the potential of photovoltaic shading in arid environments. ...
Energy efficiency in buildings is a key area of focus in the path towards net zero energy goals and mitigating climate change. Among various passive strategies for energy efficiency in buildings, building envelope shading is considered a key strategy to control solar heat gain and reduce the cooling loads in buildings. While significant focus has been given to shading glazing components of buildings, this paper addresses a critical gap by investigating the potential of shading the opaque envelope components (OECs), which include opaque walls and roofs. OECs can reduce cooling load by managing the heat ingress into the buildings. Although OECs are not widely used in energy-efficient building strategies, the passive strategies in OECS help control heat gains and decrease cooling loads, especially in hot climates. This study investigates the shading strategies of opaque OECs in a two-stage review, initially reviewing the global building energy codes to assess the inclusion of OEC shading strategies and then identifying effective shading techniques for walls and roofs through a systematic literature review. The review of energy codes reveals that very few energy codes explicitly address OEC shading with a single instance mentioned in the energy codes of Australia and India. In contrast, all the codes explicitly specify window shading as a passive strategy. The SLR further demonstrates that the shading OECs can significantly reduce cooling demands, with strategies such as overhangs, green facades, double-skin roofs, and photovoltaic panels showing up to 77% energy savings. The shading potential provides considerable scope for integrating the shading of OECs as a passive strategy that can be incorporated into the energy for better adoption in the buildings.
... A small-scale prototype was tested throughout the summer, and the results showed an increase in the interior air temperature of roughly 3 to 4 K during the sunniest hours when compared to the situation without the device. A computer simulation model was developed by Kotak et al. [32] to investigate the cooling load profile for five Indian locations for a relevant design day. The computer simulation showed that the energy needed for the cooling load caused by the roof dropped by between 73% and 90% after the PV system was installed. ...
... The use of roof shading in combination with a water pond and ventilated tunnel can reduce internal temperatures by more than 10°C and cooling load by up to 88% in hot-arid climates (Kharrufa and Adil 2012). Studies focusing on the impact of shading by rooftop solar photovoltaic modules highlight the reduction of cooling loads in tropical climates (Kotak et al. 2014). In semi-arid climates, the rooftop PV can reduce heating and cooling loads by up to 72% and 75%, respectively (Y. ...
... Kotak et al. [156] analyzed roof integrated BIPV by considering five different cities that covered Bsh and Aw climate conditions. The annual PV energy production varied from 11920 to 13011 kWh with a 73-90% reduction of cooling electricity due to installed PV shading. ...
Despite the technical maturity and substantial potential cost reduction of BIPV technologies, there are still challenges to overcome for the expansion of BIPV applications and their wider adaptation at global level. Among these, the alignment of PV integration with particular climate and environmental conditions of the local solar architecture is crucial. This will facilitate the transition to sustainable buildings and the mitigation of climate change. In this context, this study proposes for the first time, a novel BIPV climatic design framework for PV buildings positioning and adaptation to local climate towards the minimization of energy expenditure and use of resources. With the review and analysis of a large numbers of BIPV studies globally for seventy parameters grouped in eight main categories of an open-access database, the global horizontal irradiation (GHI) value is selected as an additional index to the Köppen-Geiger classification scheme. The extension accounts for the urban suitability and vulnerability and prioritize the building integration of photovoltaics. Four zones of cold (low GHI), moderate (medium GHI), warm (high GHI) and hot (very high GHI) climatic regions are considered and applied for 127 cities globally. In this framework, the sequence of PV building component integration is proposed according to local climate of each zone and the energy performance of buildings is maximized towards their positive energy contributions and sharing in local, district and city grids. Barriers and limitations of the BIPV implementation at a larger scale are discussed and the emerging research needs are revealed.
... Higher the difference higher heat transfer and lower the difference lower heat transfer either the way. Many researchers used − for estimating the inside enclosure's temperature for thermal comfort prediction [5][6][7][8]. The movement of air-conditioned passenger train compartment subjected to receive solar radiation from all direction. ...
The sol-air temperature is an important parameter in building heat transfer. This is estimated based on solar radiation and outdoor air temperature (). This work aimed to find the effect of various parameters on sol-air temperature. A theoretical sol-air temperature has been predicted with various ranges of parameters like solar radiation, material absorptivity, convective heat transfer coefficient. As per ASHRAE guidelines, the ratio of absorptivity to the convective heat transfer coefficient values ranges from 0.026 to 0.052 also considered to estimate the same. In this work, the wide range of from 15°C to 50°C was considered and the solar radiation maximum of 1000 W/m 2 was considered. The results show that the theoretical sol-air temperature reaches 102°C with maximum solar radiation of 1000 W/m 2 and the absorptivity to the convective heat transfer coefficient ratio of 0.052.
... It was suggested that in a building with a well-ventilated attic, improvement in ceiling insulation and reduction in air leakage are more beneficial interventions rather than reducing the solar absorptance of a roof with the use of BIPV. Kotak et al. (2014) [6] performed a computational study and compared the cooling load of building at five Indian locations using the CIBSE and ASH-RAE standard methods. Their results showed 73e90% cooling load decrement after PV installation. ...
... It was suggested that in a building with a well-ventilated attic, improvement in ceiling insulation and reduction in air leakage are more beneficial interventions rather than reducing the solar absorptance of a roof with the use of BIPV. Kotak et al. (2014) [6] performed a computational study and compared the cooling load of building at five Indian locations using the CIBSE and ASH-RAE standard methods. Their results showed 73e90% cooling load decrement after PV installation. ...
Photovoltaics panels are generally used on rooftop for electricity generation. However, installation of PV on the rooftop also has potential impact on the heating and cooling load of the building. This work studied these indirect benefits of rooftop PV panels by conducting experiments in Raipur, India, and compared the results with the exposed roof. Further, mathematical model is presented to analyze the annual effect of PV shading in terms of thermal load saving and power generation. Annual variation of cooling/heating load, PV power generation and overall energy-saving efficiency index is presented for different climatic zones of India. Average annual reduction in the roof and ceiling temperatures for different cities are in the range 6.05–10.96 °C and 3.94–7.15 °C, respectively. Annual cooling load reduced by 70.33–94.37%. Although PV panels shading shows negative impact during the winter season by increasing the heating load of building in all the climatic zones, the overall thermal load of building may reduce up to 22.76–74.07%. Furthermore, the overall energy-saving efficiency index varies from 21.27 to 25.12%, with maximum efficiency observed for Jodhpur city followed by Raipur. Overall, this study highlights the potential of rooftop PV application in buildings under different climatic zones of India.
... Similarly, a study in Mumbai suggests that the combination of 50% concrete and 50% vegetation and green roofs can reduce around 25% heat in the area (Dwivedi and Mohan, 2018). (III) Roof-top solar PV modules: Energy required for roof-induced cooling load decreased between 73% and 90% after installation of the PV system (Kotak et al., 2014). (IV) Alternate construction materials: Kandya and Mohan (2018) investigated the thermal performance (in terms of energy consumption for space cooling) of composite materials such as Bamcrete (bambooeconcrete composite) and natural materials such as Rammed Earth. ...
Research for urban heat island (UHI) in India has accelerated in past few years covering not only megacities but small towns as well. This chapter presents a discussion on the UHI scenario in India, which is the second largest populated country and one of the top growing economies in the world. It examines UHI quantification across India from multiple assessment methods, possible impacts, mitigation strategies and finally, identifies future research directions. In India, UHI intensities up to 8–10°C have been reported in areas with dense urban and commercial pockets. The varied methods of determination of UHI (such as fixed instruments, mobile surveys, and satellite-derived measurements) at surface and canopy layer are discussed while noting the paucity of research for the boundary layer UHI in India. Measurements alone are not adequate due to limitations of instrumental installation and errors and spatiotemporal continuity. Hence, mathematical tools such as empirical models and numerical mesoscale weather prediction models are used to understand the UHI phenomenon at region of interest, assess major causative factors, and design mitigation strategies. Case studies of such model applications are presented in this chapter. UHI effect has shown significant implications on spatiotemporal rainfall patterns, perceived thermal comfort, and heat-related morbidity and mortality for Indian cities. The review brings out emergence of concepts such as regional heat island and UHI based on local climate zones. Efficacy of various mitigation measures such as increasing green cover/plantation, thermally resistant building materials, reflective coating, etc., on surfaces is discussed in detail. The comprehensive review of different aspects of UHI in this chapter should help the scientific community as well as the regulatory bodies to determine future research focus and action plans with regard to UHI effect, its impact and mitigation in India.
... They considered the retrofitting of old buildings with a roof-top PV installation as an effective method for improving their energy efficiency. The idea of installing PV cells on the facades and roof-tops of newly erected and existing buildings in order to improve their long-term sustainability of energy was also studied in [31]. Atmaja [32] analyzed building-integrated photovoltaic (BIPV) systems for optimizing electricity production from a building envelope. ...
A building’s facade is its main interface with the external environment, as it controls almost all energy flows in the building—losses and gains. In this context, the most recent invention of adaptive façades allows for the introduction of an optimized system for both daylight management and electrical energy production. The authors of the presented paper propose a novel adaptive façade system that is equipped with vertical shading fins of 1 × 4 m that are covered with PV panels. The fins are kinetic and rotate around a vertical axis in order to optimize solar irradiation for producing electricity. The presented adaptive façade is analyzed in two stages. Firstly, the number of vertical shading fins is optimized in the context of useful daylight illuminance (UDI) and daylight glare probability (DGP) using Radiance-cored software. Next, two scenarios of PV installation are verified for fixed and the Sun-tracking solution. The results show that the Sun-tracking system is more efficient than the fixed one, but electricity production is only increased by 3.21%. The reason for this is the fact that—while following the Sun’s azimuth position—fins shade each other and reduce the effective area of the adjacent PV panels. Based on this, the authors conclude that the Sun-tracking system might be justified due to its protective or decorative function and not because of its improved effectiveness in generating electrical energy.
... Thereby, rooftop PV systems, installed primarily to reduce dependence on National Grid and electricity cost, can also alter HVAC requirements due to their shading effect. 22,23 B. Literature review Large scale impact of rooftop PV systems for urban environments is available in the literature to gauge the potential of energy generation 24 and to compare it to the ground-based PV setups. 22 The impact of environmental conditions and thermal insulation levels on the heating and cooling loads of individual buildings is presented in ASHRAE Fundamentals Handbook. ...
Solar energy is one of the most abundant and widely available renewable energy sources. It can be harnessed using photovoltaic panels on top of buildings to reduce dependence on the electrical grid and to achieve the status of net-zero energy building. However, the rooftop coverage by solar panels can modify the heat interface between the roof surface and its surrounding environment. This can alter the building's energy demand for heating, ventilation, and air conditioning. Such an impact on building's energy demand is highly correlated with its roof structure and climate. In this work, three-dimensional distributed thermal models of the bare and photovoltaic added rooftop ensembles are developed to simulate the heat gain/loss associated with the roof structure for monthly mean diurnal cycles. This work considers the low-rise, high-density building style and hot semi-arid climate of Faisalabad city, Pakistan to quantify the impact of rooftop photovoltaic on the roof-related thermal load of a building. Results depict a 42.58% reduced heat loss from the photovoltaic added roof structure during winter and a 1.98% increase in heat gain during summer. This reduces the electricity demand for indoor heating during winter and slightly increases it for indoor cooling during summer. The obtained results prove the significance of this work and provide guidelines to energy policymakers, the construction industry, and energy consumers. Moreover, this work provides a better understanding of the building's energy demand for heating, ventilation, and air conditioning with rooftop photovoltaic system and its net-zero energy requirements which is pivotal for modern construction.
... According to a study of JunHan et al. [13], the outdoor performance of photovoltaic (PV) compared to normal glass when fitted to the building surface by a small-scale test system, measured data showing that the maximum indoor air temperature for normal glass was close to 34 °C, while it was only 29 °C for PV in the same summer weather condition. The efficiency of rooftop PV systems in electricity generation and building cooling of five major cities in India were studied by Y. Kotak's [14] research group. Their simulation results demonstrated that the PV system reduced the energy for roof cooling loads from 73 to 90%. ...
At present, renewable energy sources are considered to ensure energy security and combat climate change. Vietnam has a high potential for solar power development, especially in the central region and the southern region. However, the northeast region has the lowest solar radiation value, so it can cause difficulty for rooftop solar power investment. In this paper, the study results analyze the financial efficiency of the grid-tied rooftop solar power system with battery storage and compared it to the grid-tied rooftop solar power system without battery storage. The experimental data of a grid-tied solar power system with battery storage at an office building in the northeast region of Vietnam is collected to evaluate the system’s operation performance in real conditions. The study results present that the financial efficiency of rooftop grid-tied power project with and without storage is viable since the benefit-cost ratio (B–C) is larger than one, and internal rate of return (IRR) and net present value (NPV) are positive. However, the grid-tied rooftop solar power system with storage is not quite feasible in case of changing the electricity selling price and investment cost even though the grid-tied solar power system using the storage device can operate more flexibly. The payback period of the grid-tied solar power system with storage is 6.2 years longer and the total profit is nearly 1.9 times lower than the solar power system without battery storage due to the difference in the price of the inverters and the battery. In contrast, the grid-tied solar power system without battery storage shows better financial efficiency but strongly depends on the operation of the utility grid.
