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Abstract Solar chimney power plant (SCPP) is one of the promising power generation approaches for future applications of solar energy. An unsteady comprehensive mechanism model and a streamlined unsteady mechanism model of SCPPs are derived to analyze the energy conversion and transmission of the system in this paper. The streamlined unsteady mechanism model with concise expressions clearly indicates the correlations among the power output and geometric parameters. Both of the two models are verified by the experimental data from the Spain Manzanares demonstration plant. Moreover, a power quality factor is defined to evaluate the power generation quality of SCPPs both from the points of generation efficiency and power stability. The suitability of the geometric optimization of SCPPs based on the streamlined unsteady mechanism model is finally verified by an example. The coupling optimization results show that there are a strong positive correlation between the chimney height and the power quality factor, as well as a negative correlation between the solar collector radius and the power quality factor. Furthermore, the optimal solar collector height is a quadratic function relation with the chimney diameter, while the optimal thickness of the heat storage layer is little associated with other geometric parameters.

Abstract Conventional jaggery making process utilizes the bagasse for boiling of sugar cane juice which releases pollutants into the atmosphere and high particulate matter from these emissions causes air pollution. In this article, solar powered jaggery industry with freeze pre-concentration is proposed with conventional and modified heating pans. The system performance, environmental impacts and economic feasibility were assessed by carrying out 4E (Energy-Exergy-Environment-Economic) analyses using the developed mathematical model. These systems were designed to produce 300 kg of jaggery per day when operated for 7.5 h in 3 batches with average solar direct normal irradation of 662 W/m2 and 343 °C. These systems are integrated with auxiliary heating for uninterrupted production in the absence of sunlight. These systems can mitigate nearly 2015.95 to 3062.15 tons of CO2 emission during its 25 years of lifespan under 300 clear days of operation each year. Jaggery produced by this technique is rich in its colour and completely safe for human consumption as no artificial clarificants are used. Amount invested in these systems can be recovered in a span of 12.03 to 13.45 years for jaggery selling price of USD.0.514/kg or INR.36/kg.

Abstract The solar reflectance of common building surfaces is generally low in urban areas, which can cause a heat island effect. Creating a cool surface of the building, i.e., cool roofs and cool walls are commonly-used ways to achieve this goal. A traditional, so-called “cool coating”, which is a layer of the cool roofs and cool walls, is made by mixing an organic solvent with a high-solar-reflectance inorganic additive. However, ceramic tiles have better performance in terms of durability, environment protection, and aesthetical characteristics than organic cool roofs. The development of a high-reflectance ceramic tile containing titanite crystals was carried out, and the reaction sintering mechanism of the tile was confirmed. The relationship between the crystal content and reflectance is also explained.

Abstract The aim of this paper is to examine the energy consumption of and determine energy-efficient design strategies for mid-rise and high-rise office buildings in composite climate. For this purpose, a comparative study is performed of six energy-efficient office buildings in composite climate in India. The selected energy-efficient office buildings are situated in the major cities (Delhi, Gurgaon, and Hyderabad) of India with a composite climate. This study investigates the effectiveness of different design strategies for reducing the heating, ventilation, and air-conditioning (HVAC) and lighting loads of the six buildings. The effect of factors such as the building form, envelope configuration, placement of the service core, window-to-wall ratio (WWR), and percentage of air-conditioned space on the HVAC load are analyzed. Similarly, the effect of the plan depth and WWR on the lighting load is also determined. Finally, the findings of the study are used to recommend effective design strategies for high-rise office buildings in composite climate. Moreover, the energy performance data are compared with the national energy consumption benchmarks for composite climate. The comparison indicates the design strategies performed well, that lead to a decrease in the energy consumption of high-rise office buildings in composite climate.

Abstract The random installation of various solar energy equipment on building roofs has caused visual damage to the cityscape. Keeping the rooftop equipment out of sight of the pedestrians is a new solution to eliminate visual pollution. Based on the complex urban street canyons, this paper describes a physical and mathematical model relating to the limiting height of equipment installations at any position on the roof. It is found that the limiting height of equipment varies with the building roof height, the street width, and other factors. In addition, for a case with four main urban roads, the variation patterns for the limiting height of rooftop equipment changed with the street width and the distance from the installation to the parapet have been established, which is of great relevance for determination of the limiting equipment height in actual installations. The research can not only help to remove visual pollution from rooftop equipment in street canyons, and provide a guide for the selection and installation of solar equipment, but can also provide significant information for urban space planning and building design.

The concept of reducing the cooling load of airconditioned building by maintaining a water film spray over the roof is a well known proposition in the literature and has been exploited both experimentally and theoretically by several workers. The conscious scientific application of air ventilation in summer has also been suggested for passive space airconditioning. Since the ventilation is controlled by opening windows/door and hence depends on ventilation timings or its duration, a periodic analysis for variable ventilation is also desirable if the window on south-facing wall is opened/closed on daily cycle. In this communication the authors have developed a periodic heat transfer model which incorporates the effects of furnishings (assumed isothermal mass), air ventilation through window/door (assumed time dependent) and the basement ground heat storage. Explicit expression for the indoor air temperature as a function of time in a building with a water film over the roof and controlled ventilation has been obtained. Numerical calculations for a typical hot summer day in Delhi using the relevant parameters have been made to study the feasibility of the proposed model. The effects of the presence/absence of water spray over the roof, continuous and intermittent ventilation rates and timings on the indoor air temperature have been examined. It is found that the maintenance of a water film spray over the roof and the ventilation control systems in a building in hot sunny climates significantly reduces the indoor air temperature.

Abstract Accurate prediction of building energy performance requires precise information of the local climate. Typical weather year files like test reference year (TRY) and typical meteorological year (TMY) are commonly used in building simulation. They are also essential for numerical analysis of the sustainable and renewable energy systems. The weather year file of one city is often employed by the nearby cities for such purposes. In this paper, the developments of customized weather year formulation are reviewed. The key issues are discussed making reference to two neighboring cities, Hong Kong and Macau, using their weather data records over a century, and the typical weather year files developed. The findings support the preference of TMY over TRY. It is also suggested that the TMY selection process should include the most recent meteorological observations, and should be periodically reviewed to well reflect the long-term climate change.

Abstract Microencapsulated n-octadecane with titanium dioxide (TiO2) shell was prepared by a sol–gel method in a nonaqueous oil-in-water (o/w) emulsion using a green solvent as the dispersion medium. The morphology, chemical structure, and crystalloid phase of the resultant microcapsules were determined by scanning electronic microscope (SEM), Fourier transformation infrared spectroscope (FT-IR), and X-ray diffractometer (XRD), respectively. The differential scanning calorimeter (DSC) and the thermogravimetric analyzer (TGA) were used to investigate the thermal properties and thermal stabilities of the samples. The resulting microcapsules presented spherical shape with average size of 2–5 μm. The results of FT-IR and XRD showed that n-octadecane was well microencapsulated in TiO2 shell. DSC and TGA results indicated that the samples exhibited good performance of storing and releasing the latent heat during phase-change cycles and high thermal reliability. The microencapsulation process in this study is simple, high-efficiency, and environmentally friendly. The microencapsulated n-octadecane with TiO2 shell will be a potential candidate material for thermal energy storage applied in the fields of solar energy storage, building energy conservation, air-conditioning systems, and waste heat recovery.

Abstract In this effort, 10 μm thick rear contact (RC) silicon–germanium (SiGe) based solar cell device has been discussed with SiC (20 nm)-based front surface passivation for the suppression of interface recombination as well as improvement of short circuit current density ( J SC ) and open-circuit voltage ( V OC ). The design principles presented here balance the electronic and photonic effects together and is a significant step to design highly efficient thin solar cells. Photo reflectance is significantly reduced in the UV/visible spectral region due to the presence of SiC. This results in external quantum efficiency (EQE) >90% in the spectrum range of 400–650 nm wavelength. Also, at wavelengths equivalent to 300 nm, SiC passivated device shows record EQE of 85%. The presence of SiC as a surface passivating layer shows enhanced surface characteristics in terms of reduced surface recombination and higher photon absorption rate. This results in 15.4% power conversion efficiency (PCE) under standard air mass 1.5 illuminations. Further, the proposed device has also been analyzed for concentrator photovoltaics (CPV) applications, resulting in 18.4% and 19.3% efficiencies at 1 W/cm 2 (10 suns, 27 °C) and 2 W/cm 2 (20 suns, 27 °C) respectively. Till date, the proposed design proves to be highly efficient in the sub 10 μm regime. All the simulations have been done using DEVEDIT and ATLAS device simulator