Search Results (8)

Flat plate collectors (FPCs) are the leading solar thermal technology for low-medium range temperature applications. However, their expansion in developing countries is still lacking because of their poor thermal performance. Improving the thermal performance of flat plate collectors (FPCs) is a crucial concern addressed in this review This study comprehensively discussed the performance improvement methods of FPCs, such as design modification, reflectors, working fluid, and energy storage materials, by covering current issues and future recommendations. Design factors such as coating and glass cover thickness, thickness of absorber plate and material, air gap between the glass cover and absorber plate, and riser spacing, along with insulation materials, are examined for their impact on FPC performance. Absorber design changes with selective coatings for improving the heat transmission rate between the working fluid and absorber are critical for enhancing collectors’ thermal output. The nanofluids utilization improved FPC’s thermal performance in terms of energetic and exergetic outcomes in the 20–30% range. Moreover, adding a heat storage unit extends the operating hours and thermal output fluctuations of FPCs. Research suggests that employing turbulators and nanofluids as heat transfer fluids are particularly effective for enhancing heat transfer in FPCs. This comprehensive review serves as a critical tool for evaluating and comparing various heat transfer augmentation techniques, aiding in the selection of the most suitable option. Full article

Solar energy’s most promising application is in water heating, followed by other solar thermal applications. In this investigation, a novel method of incorporating a phase-change material (PCM) between the annulus space of an evacuated tube and an aluminum finned heat pipe is employed. During day time, the PCM stores the excess amount of heat and releases it in order to heat the flowing water during high-demand/insufficient solar radiation. This study aims to evaluate the detailed heat transfer assessment and energetic and exergetic efficiencies of the developed PCM-integrated solar water heater in both clear and cloudy weather conditions at 20 LPH. The outcomes of the study found that the maximum useful amounts of energy collected daily for the clear and cloudy days were 10.65 MJ and 8.52 MJ, respectively, whereas temperatures of the stored water were found to be 45.2 °C and 41.4 °C on the next day at 6:00 a.m. for the corresponding days. The daily energetic and exergetic outputs of the designed system were 76.57% and 79.64%, and 2.37% and 1.38%, respectively, at fixed mass flow rate for the clear and cloudy day conditions. The overall heat transfer coefficients (U_L) for both days were 0.75 and 0.72 W/m² K, respectively. The findings show that the proposed system overcomes the issue of overheated heat pipes and can provide hot water even in cloudy/low-sunshine conditions. Full article

The overheating of heat pipes, poor transfer of heat across the absorber and finned heat pipes, and inability to provide hot water in the late evening hours are major problems associated with conventional heat pipe vacuum collector systems. The amalgamation of highly conductive storage material between the absorber tube (heat collecting surface) and the heat pipe is an effective way to overcome these problems. In this study, a stearic acid amalgamated vacuum tube solar collector system was designed and fabricated and its thermal output compared with a conventional vacuum tube system without storage material under the same environmental conditions. The experimental results showed that the amalgamation of stearic acid as storage material enhanced the thermal output of the solar system compared to the conventional one. The desired heat gain of the solar system with storage material increased by 31.30, 23.34, and 18.78% for Test 1_40 °C, Test 2_45 °C, and Test 3_50 °C, respectively. The technoeconomic analysis showed that almost 118.80 USD in revenue could be earned by the proposed solar system at the end of 15 years. The total running cost of ELG and the developed solar system was observed to be 202.62 and 86.70 USD, respectively. On average, the cost of hot water production using the solar system and ELG was found to be 0.0016 and 0.004 USD/L, respectively. The value of LEC was found to be 0.062 USD/electricity unit, which was much lower than the LEC value of ELG (0.116 USD/electricity unit). The value of NPW (73.73 USD) indicated high acceptability of the proposed system. The payback time is lower than the life of the system, indicating its suitability for use in the commercial sector. Therefore, the proposed solar system is highly recommended over conventional water heating systems in urban and rural areas. Full article

In recent years, building energy consumption has increased every day due to population growth and an increased human desire for a healthy and pleasant lifestyle, and this is responsible for a crisis of energy shortages worldwide. Therefore, use of solar water heating (SWH) systems in buildings for hot water demand is the prime need of the hour to maintain sustainability. The novelty of this work was in developing a phase change material (stearic acid)-filled U-tube based evacuated tube solar collector (collector A). In addition, another collector B, left without energy storage material, was considered a reference unit for comparing the energy and exergy outputs. The study’s main aim was to examine the energy, exergy, enviro- and exergoeconomic analysis of newly developed water heating systems. The findings of study revealed that the maximum daily energy outputs of collector A were found to be 85.86% (simultaneous mode) and 84.27% (midday charging mode) at a high mass flow rate (0.5 LPM), and exergy outputs were 19.41% and 21.35%, respectively, at a low flow rate. The thermal output of collector A was higher than that of collector B. The per liter cost of hot water produced from collector A with PCMs was found to be INR 0.1261 and INR 0.1276, respectively, under both modes, which is less compared with the electric geyser (0.325 INR). The levelized energy cost, net present worth, and the payback time of the developed collector A obtained were 4.61 INR/kWh, INR 49710, and 4.49 years (simultaneous), and 4.67 INR/kWh, INR 48130, and 4.64 years (mid-day charging), respectively. Furthermore, the amount of CO₂ mitigation from the energy and exergy perspective for collector A was found to be 24.30 and 23.76 tCO₂/lifetime and 5.31, 5.58 tCO₂/lifetime, respectively. Full article

Manufacturing and mining sectors are serious pollution sources and risk factors that threaten air quality and human health. We analyzed pollutants at two study sites (Talcher and Brajrajnagar) in Odisha, an area exposed to industrial emissions, in the pre-COVID-19 year (2019) and consecutive pandemic years, including lockdowns (2020 and 2021). We observed that the annual data for pollutant concentration increased at Talcher: PM_2.5 (7–10%), CO (29–35%), NO₂ and NO_x (8–57% at Talcher and 14–19% at Brajrajnagar); while there was slight to substantial increase in PM₁₀ (up to 11%) and a significant increase in O₃ (41–88%) at both sites. At Brajrajnagar, there was a decrease in PM_2.5 (up to 15%) and CO (around half of pre-lockdown), and a decrease in SO₂ concentration was observed (30–86%) at both sites. Substantial premature mortality was recorded, which can be attributed to PM_2.5 (16–26%), PM₁₀ (31–43%), NO₂ (15–21%), SO₂ (4–7%), and O₃ (3–6%). This premature mortality caused an economic loss between 86–36 million USD to society. We found that although lockdown periods mitigated the losses, the balance of rest of the year was worse than in 2019. These findings are benchmarks to manage air quality over Asia’s largest coalmine fields and similar landscapes. Full article

The World Health Organization (WHO) estimates that around 3 billion people today are exposed to smoke from the household combustion of solid fuels. While the household use of solid fuels has decreased over the last few decades, it remains a leading modifiable risk factor for the global burden of disease. This systematic review analyzed the impact of Household Air Pollution (HAP) on lung function in children (under 18 years of age), as this is the time period of accelerated growth rate until full skeletal maturity. Data from 11 published studies demonstrated that exposure to smoke from solid fuel was associated with a lower growth rate of several lung function indices (FVC, FEV₁, FEF_25–75) in children. However, there was no observed association between HAP and the FEV₁/FVC ratio over time. Although the evidence suggests an inverse association between high exposure to HAP and lung function indices, there is a lack of longitudinal data describing this association. Therefore, precaution is needed to reduce the smoke exposure from solid fuel burning. Full article

An irreversible cycle model of a Braysson heat engine operating between two heat reservoirs is used to investigate the thermoeconomic performance of the cycle affected by the finite-rate heat transfer between the working fluid and the heat reservoirs, heat leak loss from the heat source to the ambient and the irreversibility within the cycle. The thermoeconomic objective function, defined as the total cost per unit power output, is minimized with respect to the cycle temperatures along with the isobaric temperature ratio for a given set of operating parameters. The objective function is found to be an increasing function of the internal irreversibility parameter, economic parameters and the isobaric temperature ratio. On the other hand, there exist the optimal values of the state point temperatures, power output and thermal efficiency at which the objective function attains its minimum for a typical set of operating parameters. Moreover, the objective function and the corresponding power output are also plotted against the state point temperature and thermal efficiency for a different set of operating parameters. The optimally operating regions of these important parameters in the cycle are also determined. The results obtained here may provide some useful criteria for the optimal design and performance improvements, from the point of view of economics as well as from the point of view of thermodynamics of an irreversible Braysson heat engine cycle and other similar cycles as well. Full article

An ecological optimization along with a detailed parametric study of an irreversible regenerative Brayton heat engine with isothermal heat addition have been carried out with external as well as internal irreversibilities. The ecological function is defined as the power output minus the power loss (irreversibility) which is ambient temperature times the entropy generation rate. The external irreversibility is due to finite temperature difference between the heat engine and the external reservoirs while the internal irreversibilities are due to nonisentropic compression and expansion processes in the compressor and the turbine respectively and the regenerative heat loss. The ecological function is found to be an increasing function of the isothermal-, sink- and regenerative-side effectiveness, isothermal-side inlet temperature, component efficiencies and sink-side temperature while it is found to be a decreasing function of the isobaric-side temperature and effectiveness and the working fluid heat capacitance rate. The effects of the isobaric-side effectiveness are found to be more than those of the other parameters and the effects of turbine efficiency are found to be more than those of the compressor efficiency on all the performance parameters of the cycle. Full article