Search

In this research, the thermodynamic (energy and exergy) analysis of a single slope solar still using graphite plates and block magnets (GPBMSS) was investigated during summer and winter climatic conditions of Coimbatore city (latitude: 11°01′68′′N and longitude: 76°95′58′′E), in India, 2019. The results observed in GPBMSS were compared with a conventional solar still (CSS) under the same climatic conditions. The outcomes observed that the hourly productivity in GPBMSS was 19.6% and 22.8% higher in summer and winter days, respectively, when compared to CSS. The cumulative productivity in GPBMSS was found to be about 3.93 kg/m2 and 3.56 kg/m2 respectively, for 12 h observations during summer and winter days. Furthermore, the energy and exergy efficiencies of GPBMSS were substantially improved by 20.6% and 18.1% when compared to CSS during summer days. Similarly, the energy and exergy efficiencies of GPBMSS were increased by 18 and 19% compared to CSS in winter days. In addition, the maximum basin exergy destruction was observed in CSS compared to other solar still components. The results observed that the heat storage ability of the graphite plates and water magnetization in GPBMSS greatly decreased the exergy destructions. Finally, the water quality analysis proved that the distillate collected from both GPBMSS and CSS satisfied the requirements recommended by the Bureau of Indian Standards. HIGHLIGHTS Graphite plates and block magnets are attached in a solar still basin (GPBMSS) and improved the productivity by 3.93 kg/m2 and 3.56 kg/m2 respectively, in summer and winter climatic days.; The energy efficiency of GPBMSS was substantially improved by 20.6 and 18%, respectively, compared to CSS during summer and winter days.; The exergy efficiency in GPBMSS was enhanced by 18.1 and 19%, respectively compared to CSS in summer and winter days.

In this research work, the productivity, energy, exergy, and economic and enviro-economic performance in crushed gravel sand heat storage and biomass evaporator-assisted solar still (CGS-BSS) have been investigated and compared the results with conventional solar still (CSS) under the similar climatic conditions of Coimbatore City during the year 2019. The heat accumulated in crushed gravel sand and biomass evaporator have been used to preheat the inlet saline water and air vapor before entering into the solar still. This results in enhanced air vapor mixture temperature and evaporative heat transfer rate of CGS-BSS significantly. The productivity, energy, and exergy efficiencies in CGS-BSS were improved by 34.6%, 34.4%, and 35%, respectively when compared to CSS. In economic analysis, the payback period (PBP) in both CGS-BSS and CSS was estimated to be about 4.7 months and 3.9 months, respectively. Furthermore, in enviro-economic analysis, the CO2 emission estimated in CGS-BSS and CSS was about 16.63 tons and 8.18 tons, respectively during its lifetime of 10 years.

In this paper, the performance of a single slope solar still has been improved using graphite plate fins and magnets (GPF-MSS) in the basin and compared with conventional solar still (CSS) under the same climate conditions. The experiments have been carried out at Coimbatore city in India during the summer months of 2019. The energy and exergy performances of solar stills have been assessed under the influence of solar irradiation, ambient temperature, and wind velocity. The economic and environmental benefits were evaluated for the period of 10 years. The quality of productivity collected was measured and compared with Bureau of Indian Standards (BIS). The results showed that the productivity, energy, and exergy efficiency of GPF-MSS were improved by 19.6%, 21.4%, and 18.1%, respectively, when compared to CSS. The exergy destruction in basin was reduced significantly in GPF-MSS due to sensible heat absorption by graphite plate fins and magnets when compared to CSS. The payback period of GPF-MSS and CSS was estimated as 3.4 and 3.6 months, respectively. The enviro-economic analysis revealed that the net CO2 emissions of GPF-MSS and CSS were estimated as 14.1 tons and 8.42 tons, respectively. The carbon credits earned for GPF-MSS and CSS were estimated as 338.4 USD and 202.1 USD, respectively. The quality of distillate obtained from both the solar stills has met the requirements of BIS.Graphical abstract.

In this work, the energy, exergy, economic and enviro-economic assessments of gravel coarse aggregate sensible heat storage-assisted single-slope solar still are performed. The gravel coarse aggregate sensible heat storage bed preheats the saline water before entering the basin of the solar still and also stores the excess sensible heat. The experimental observations have been made under the climatic conditions of Coimbatore city in India during the year 2018. The experimental results showed that the maximum energy and exergy efficiency of about 32% and 4.7% were observed for 1 cm water depth. The maximum productivity of about 4.21 kg m−2 per day was observed for 1 cm water depth during the period of 12 h of observation. The economic analysis revealed that the cost of distillate per litre was estimated as 0.0618$ with a payback period of 4.3 months. Moreover, it is observed that the proposed solar still configuration has reduced 8.27 tons of CO2 emissions for 1 cm water depth during its life cycle. The parametric analysis results confirmed that the solar irradiation and water depths are the two major parameters influencing the performance of a solar still. Furthermore, the water quality assessment revealed that all the water samples collected from the solar stills are suitable for drinking and also meet the requirements of the Bureau of Indian Standards.

The explosion of the population is alarming as the demand increases exponentially for resources. The freshwater resources are being exploited, and innovative and economical methods are analyzed experimentally to extract freshwater from various sources. Desalination performed using solar energy is an economical method to obtain fresh water from seawater and brackish water, which are available prolifically in nature. Since the phenomenon of desalination demands solar irradiation, which is an intermittent source of energy, distillation is not feasible in some places where the solar intensity is low. In the solar desalination, the saturation temperature of the saline water is very less at low saturation pressure thereby requiring large latent heat of evaporation. Hence, vacuum pressure could be the most appropriate choice to extract drinkable water in territories where the intensity of solar irradiation is poor. In order to this, the utilization of evacuated tube collectors and vacuum technology in the solar desalination unit has been considered for discussion as it is the most sought-after subject of interest in the current scenario. Methods for implementing the vacuum technology are also introduced with plenty of experimentations. Vacuum technology implemented in the evaporator of desalination system has been supplemented with nano-fluids and phase change materials to accelerate the evaporation process, increase efficiency, and obtain a greater productivity. In this review, the performance of the solar desalination unit under the vacuum effect were discussed in detail. Furthermore, in economic analysis, the cost effectiveness and cost per liter of distillate (CPL) were discussed to estimate the payback period. Finally, this review also suggests the vision to identify the future scope for additional implementations.

In this research, the thermodynamic (energy and exergy) and economic assessments of heat pump-assisted solar still with paraffin wax was investigated under the climatic conditions of Coimbatore city in India during the year 2020. The observed experimental results in heat pump solar still (HPSS) was compared with conventional solar still (CSS) in the same climatic conditions. This model works on the principle of latent heat observed during condensation which was regenerated by heat pump to preheat the inlet basin saline water of solar still. The observed maximum productivity of HPSS was about 14.5 kg/m2, which was 83.7% higher than CSS. The energy and exergy efficiency improvement in HPSS were about 65% and 82.3%, respectively, higher than CSS. The observed maximum coefficient of performance (COP) of heat pump was about 2.61. The payback period (PBP) of CSS and HPSS was estimated to be about 4.1 months and 3.2 months, respectively. The results observed in HPSS have significantly improved the daily productivity than CSS.

In this simulation, the parametric performance of basin saline water in single slope solar still has been analyzed using computational fluid dynamics (CFD). The two-phase and three dimensional solar still model has been created using ANSYS FLUENT v19.2 software to analyze the water volume, water density, water temperature, vapor velocity, vapor density and vapor volume. The entire solar still model was considered under the quasi-static conditions and the results observed in mid, right and left planes. The prediction of heat, mass and momentum transfers in saline water and vapor were differed in each planes. The maximum hourly productivity of about 680 ml was observed during the simulation. The predicted results confirmed that, the CFD is a much effective tool for design and modeling the thermal equipment.

In this paper, the thermodynamic (energy and exergy) analysis and water analysis of a modified solar still augmented with copper tube heat exchanger in coarse aggregate have been carried out and compared with conventional still performance under the same climatic conditions. Basin water temperature, solar intensity, wind velocity, cumulative yield, water conductivity, total hardness, pH value and fluoride concentration are obtained from experimental results for saline, basin and distilled water. Energy efficiency, evaporation and convective heat transfer coefficient, exergy evaporation rate and exergy efficiency are determined from energy and exergy analysis. The results show that the modified still has an efficiency of 28% and 17% greater than the conventional still. The productivity of modified and conventional still is 6.23 kg m−2 and 2.41 kg m−2, respectively. The exergy efficiency depends on the time of the test day and reaches a maximum value of 5.5% and 1.1%, respectively, for the modified and conventional still. From the water analysis, it is observed that the maximum distilled water pH, water conductivity, hardness and fluoride content are 7.5, 0.8 × 10−4 S m−1 (0.8 µS cm−1), 0.5 × 10−3 kg m−1 (0.5 mg L−1) and 0.7 × 10−3 kg m−3 (0.7 mg L−1), respectively, with the still salinity removal efficiency of 99%. The results indicate that the modified still has higher energy and exergy efficiencies and better water quality with cumulative yield.

Population density and automation is the main reason for the demand of drinking water. Water purification without affecting an ecosystem is the important need for daily life. Desalination is the best and effective way to satisfy the demand of fresh water. It is the most effective application of the solar energy. There are many conventional and non-conventional techniques available to make drinking water from the saline water. Among these solar desalination proves to be both economical and eco-friendly system particularly for rural areas. Solar stills are simple device which is used to provide pure water from the saline water by the principle of evaporation and condensation. This article reviews on the several research done on the solar stills to enhance productivity. Different designs of solar still and energy storage materials have been used to increase the yield and also this study proved the fact that efficiency of the solar still is majorly influenced by design and operating parameters.

In this paper, the performance and economic analysis of a heat pump water heater assisted regenerative solar still using latent heat storage was experimentally studied. The heat released during condensation of water vapour inside the solar still was regenerated using a heat pump to pre-heat the saline water before entering the basin and producing hot water for domestic use. The experimental observations have been made under the influence of solar irradiation, ambient temperature and ambient wind speed. The results showed that the heat pump water heater assisted regenerative solar still has attained cumulative productivity between 14.0 and 16.0 kg/day during 12 h of operation. Moreover, the system delivers more than 100 L of hot water at 46.8–52.8 °C for domestic use. The monthly average coefficient of performance of the heat pump was estimated in the range between 2.21 and 2.55. The cost per litre of distillate obtained from the system is estimated as 0.05471 USD. The payback period was estimated as 21.46 months for 275 days of operation in a year at 12% interest and distillate selling price of 0.08 USD/litre. The water samples obtained from the experiments are suitable for drinking and met the Bureau of Indian Standard requirements.

In the present scenario many developing countries are depending on oil producing nations for their fuel resources. Due to demand and scarcity of the fuel, there has been a huge increase in fuel prices. The vehicular population is also continuously increasing and becoming a great menace to peoples. This paper aims to provide an alternate solution for petroleum based fuels. It suggests that biodiesel produced from lemon and lemon grass oil can be used as an alternative fuel. This work investigates the thermal performance of four stroke diesel engine using blends of biodiesel and diesel as a fuel. Performance parameters like brake thermal efficiency, mechanical efficiency and specific fuel consumption were measured at different loads for diesel and various combination of biofuel (L10, L20, and L30). The maximum brake thermal efficiency obtained is about 26.12%for L20 which is slightly higher than that of diesel (24.91%). Engine experimental results showed that exhaust emissions including CO2 and HC were reduced by 6% and 5% for L20 mixture of biodiesel whereas CO emission was as same as diesel. However, there was increase in NOxby 26% to the diesel fuel.