Solar energy performance analysis of basin-type solar still under the effect of vacuum pressure

ABSTRACT

This paper deals with a solar still for distilled water, using the heat of the sun to evaporate, cool and then collect the water. They are used in areas where drinking water is unavailable, so that clean water is obtained from dirty water or from plants by exposing them to sunlight; vacuum pressure is delivered to still-type solar. The reason for selecting vacuum pressure is that during the monsoon and cloudy days, solar intensity will not be high as it leads to evaporation at lower temperature saline water under the soar still. The basin area for the production of 5 litres per day of fresh water is determined as 1.44?m²and the solar still basin area of 1.44?m² and 21.5° tilt angle are designed. Solar energy be may used full to alternate in electrical power and to purify water in future. Finally, the performance was analysed for the solar still with a vacuum pressure at 0.6 bar. The outcome of the theoretical analysis shows that adoption of 0.6 bar pressure inside the solar still improves the average performance by 30%. In order to overcome this problem, vacuum could be applied for the better performance of the solar still during the low solar intensity periods.     

Year-round numerical simulation of a parabolic solar collector under Lebanese conditions: Beirut case study

A detailed thermal and optical numerical model is developed to simulate the performance of a small-scale parabolic collector having an evacuated receiver line with selective coating, taking into account different energy balances and interactions with the surrounding. An analytical model is developed to estimate the direct, diffuse and global solar radiation intensities on inclined surfaces. The collector performance model was validated using published experimental data. A year-round dynamic simulation for the collector performance under Beirut climatic conditions was carried out with an economic and environmental analysis. The outlet water temperature could reach a maximum of 114°C in July and 52°C in December by employing a collector of about 6 m² aperture area with 0.01 kg/s water flow rate. The maximum daily thermal energy production is attained in July with 22.267 kWh while January exhibits the lowest thermal energy production with 6.704 kWh per day with a maximum thermal efficiency of 72%.     

Theoretical analysis of a triangular pyramid solar still integrated to an inclined solar still with baffles

This paper presents the theoretical analysis of a triangular pyramid solar still integrated to an inclined solar still with baffles. The performance of the solar still depends on water mass inside the basin. The yield of triangular pyramid solar still is increased by integrating it to an inclined solar still with baffles. Analytically, the water mass inside the basin is increased from 20 to 100?kg. Theoretical results show that the increase in water mass decreases the yield from 6% to 46% during the daytime, whereas due to thermal energy storage at higher mass, the yield during the nighttime increases from 46% to 86% with integration. Similarly, a triangular pyramid solar still is theoretically analysed for its performance.     

Effect of forced cover cooling technique on a triangular pyramid solar still

In the present study a triangular pyramid solar still is theoretically analysed by flowing air over the entire surface of the glass from the top to analyse the improvement in yield of fresh water. The effect of water mass and wind velocity was theoretically analysed. The results show that there is a significant improvement in the yield of fresh water to about 10.1?kg/m² with a maximum velocity of air (U?=?40?m/s) at a least water mass of 20?kg inside the basin. For practical cases the yield of fresh water depends on naturally occurring wind velocity and the results show that the improvement in yield is 104% with an increase in velocity from 0.5 to 4?m/s.     

Mathematical modelling of solar radiation incident on tilted surface for photovoltaic application at Bhopal,M.P., India

In general, solar radiations are the combination of beam plus diffuse and ground-reflected radiation. The availability of recorded data on a tilted surface is very rare due to lack of measuring equipment and techniques involved. In this study, a standard procedure is adopted for estimation of solar radiation on a tilted surface for a location in Central region of India. Solar radiation is estimated for three tilted positions: First, solar collector tilt equal to latitude angle, second, solar collector tilt equal to latitude angle +15° and third, solar collector tilt at latitude ?15°. Total global solar radiation estimated on the inclined surface for various photovoltaic (PV) modules was used to obtain the annual energy yield based on the estimated value. It was found that on an average, 14?kWh/m² of annual energy output can be obtained for monocrystalline solar PV module corresponding to the inclination of 23.26° latitude at Bhopal.     

Feasibility analysis of distributed solar electricity penetration in cement manufacturing plants

Industrial manufacturing units like cement and steel are benefited little by solar electricity. This paper presents feasibility of application of solar electricity in cement manufacturing plants in a distributed manner. Distributed solar PV systems without battery have been simulated using HOMER Pro micro grid design software to see the effects on net present cost (NPC), levelised cost of energy (COE), pollutant emissions, coal consumption and cost of cement production. The daily solar radiation ranges from 3.79 to 6.71?kWh/m²/day and the total distributed load supplied by solar electricity is 8876.4?kWh/day which is 0.82% of overall plant load. The results show that proposed system reduces pollutant emissions by almost 23% with an increase of NPC by 3.075% and COE by 0.6436% only. It saves 709,139?kg coal per year with 0.6437% increase in cement production cost. Proposed system will be beneficial economically too when PV prices come down in future.     

Annual performance analysis of a single-basin passive solar still coupled with evacuated tubes: comprehensive study in climate conditions of Mahesana,Gujarat

A solar still is very simple device to convert available brackish or saline water into drinkable water by use of solar energy. But due to its lower distillate output, it is not used widely for industrial and domestic potable water application. In the present research paper, annual performance analysis of a single-basin passive solar still with vacuum tubes (SBSWVT) is carried out in climate conditions of Mahesna, Gujarat, India, during July 2011–June 2012. From constant research work of 1 year, energy payback time of 176 days and cost of water produced of around 0.716?Rs per litre have been found.     

Performance study of underground thermal storage in a solar-ground coupled heat pump system for residential buildings

This paper is performed to analyze the performance of underground thermal storage in a solar-ground coupled heat pump system (SGCHPS) for residential building. Based on the experimental results, the system performance during a longer period is simulated by the unit modeling, and its parametric effects are discussed. The results show that the performance of underground thermal storage of SGCHPS depends strongly on the intensity of solar radiation and the matching between the water tank volume and the area of solar collectors. Compared with the solar radiation, the variations of the water tank temperature and the ground temperature rise lag behind and keep several peaks during the day time. For the case of Tianjin, the efficiency of underground thermal storage based on the total solar radiation and absorbed solar energy by the collectors can reach over 40% and 70%, respectively. It is suggested that the reasonable ratio between the tank volume and the area of solar collectors should be in the range of 20–40 L/m².     

Economic and exergy investigation of triangular pyramid solar still integrated to inclined solar still with baffles

This paper presents the detailed exergy and economic investigation of triangular pyramid solar still under passive and active mode of operation. For validation, experiments were carried out at different water depth maintained inside the basin under a continuous flow of water from an inclined solar still. Results confirm that the effect of integration rises the exergy efficiency during the offshine period, whereas during the sunshine hours the exergy efficiency decreases when the maintained the depth of water inside basin decreases. Similar study on economic analysis shows that the net pay back period increases from 5.6 to 11.4 with an increase in the water depth at an average selling price of water Rs 5/kg in a standalone triangular pyramid solar still.     

An Analytical Study on global radiation and meteorological parameters for India

ABSTRACT

A study is carried out for global radiation (global horizontal and global tilted radiation) and meteorological parameters (humidity and temperature) recorded for a period of one year (2011) at the National Institute of Solar Energy (NISE), Gwal Pahri (28.42°N, 77.15°E), India. Maximum global horizontal radiation of 7.22?kWh/m² is recorded in the month of June while minimum of 0.91?kWh/m² is observed in February. The highest value of the tilted radiation 7.27?kWh/m² is recorded in March and the lowest value 0.90?kWh/m² is noticed in February. The maximum temperature of 36.5°C and humidity of 87.6% are observed in the months of June and July, respectively. Conversely, minimum temperature of 6.1°C and humidity 21.7% are noticed in the months of January and April, respectively. Furthermore, meteorological parameters have been correlated with global radiation on horizontal and tilted surface. The study is vital for the performance analysis of different solar energy applications.     

Experimental analysis of thermal performance of evacuated tube solar air collector with phase change material for sunshine and off-sunshine hours

An experimental investigation of an evacuated tube solar air collector coupled to a latent thermal energy store for generating hot air when no solar radiation is incident was undertaken. Acetamide was used as a phase change material (PCM). The latent thermal energy store was integrated with the manifold of the solar collector and water was used as the working fluid transferring solar gain to the air being heated. The maximum measured temperature differential between the heated air and the ambient air was 37°C and 20.2°C during conditions of incident and non-incident solar radiation, respectively. This occurred using a circular fin configuration at a flow rate of 0.018?kg?s^?1. The efficiency at low (0.018?kg?s^?1) air flow rates was 0.05–0.50 times less as compared to high (0.035?kg?s^?1) air flow rates. This system has advantages over systems using sensible storage as it can be used after sunset due to better heat storing capacity of the PCM.     

Life cycle cost analysis of a double-effect solar still

In this present paper, the study focuses on the development of a double-effect solar still with evacuated tubes for water desalination considered for small-scale applications at remote locations where only saline water or brackish water is available. In this present paper, the potable water cost per litre has been evaluated. The payback periods for different conditions of the distribution of distilled water, namely at the cost it is produced and at the selling price on market rate, have been evaluated. The cost of water per litre was a minimum of Rs. 0.19 with the average distillate output being about 20?l/day, when the interest rate and the lifetime of the solar still are taken as 4% and 50 years, respectively. The lowest payback time of 45 days was obtained when the selling price of water was Rs. 20?per litre.     

Experimental investigation of a passive solar still with and without tetrahedral sponge in basin

In this work, an experimental study is carried out to investigate the influence of the presence of porous media on the performance of solar still. Two different shapes of sponge pieces, namely cube and tetrahedron, are considered for this study. Experiments are conducted on a single-slope solar still with condensing cover of 30° inclination. This study was performed in Indian coastal climatic condition for 24?h. The experimental study emphasises on the overall distillate yield, and the efficiency of the still with sponge cubes and tetrahedrons is compared with the conventional still. The size of the pieces is selected such that the volume of both shapes is the same. As the surface area to volume ratio is more for tetrahedral sponge piece, the highest distillate production is observed in that of sponge cube. It is observed that the maximum distillate yield is produced at optimum values of water depth at 5?cm, single piece sponge volume of 216?cm³ and sponge volume of 30% of the basin water volume. The increase in yield is due to the capillary effect and high evaporation rate and it varies from 45% to 219% with tetrahedral sponge pieces when compared to conventional still.     

Study on phase change material and its appropriate thickness for controlling solar cell module temperature

ABSTRACT

Appropriate thickness of phase change material (PCM) to control the solar cell module temperature for increasing power generation was carried out. A PCM, RUBITHERM RT42, with the melting point at 42°C and a thickness of 50?mm was used to absorb heat at the back of a 250?W_p polycrystalline solar cell. A numerical enthalpy method to predict the melting phenomenon of the PCM, RT35, 42, 47, and 55, and the solar cell module temperature was developed. The results agreed well with those of the experimental data. It was found that the maximum generated power was around 167?W in comparison with 147?W of the normal unit at a solar radiation of 867?W/m². The daily power outputs were 0.707 and 0.642?kWh, respectively. From the simulation under Chiang Mai climate, for RT42 PCM, it was found that the appropriate thickness was around 40?mm.     

Performance analysis of evacuated tubes coupled solar still with double basin solar still and solid fins

ABSTRACT

Experimental set up of double basin solar still with evacuated tubes has been fabricated by locally available materials and then carry out research work by use of solid fins. Here 2.5?cm constant depth of water maintained and 3?cm depth mild steel fins are used. Experimental results have been obtained during month of March and April 2018 during clear sky days. Month of March 2018 is chosen for experiments on double basin solar still with evacuated tubes only and April 2018 is chosen for experiments on double basin solar still with evacuated tubes and fins. After series of experiments, it has been found that, the fins increase 25% distillate output compared with alone double basin solar still with evacuated tubes. It also increases distillate output during sunshine hours as well as off-sunshine hours.     

Characteristic parameters of a hypocaust construction

Hypocaust, an ancient Roman concept for keeping the inside of buildings warm, has been explained with a survey of a few modern buildings based on these concepts and using solar heat employing a number of design variations. Results expressed in terms of energy requirements per m² of floor area per degree day comes out to be minimum (15.4 kJ m⁻² per DD per annum) for a solar chimney and maximum for solar air collectors (128.4 kJ m⁻² per DD per annum). The basic parameters that determine the performance of a hypocaust construction are size of the cavity determining the heat transfer between the flowing fluid and the building component and the storage capacity of the hypocaust element. The optimum width of the cavity comes out to be between 50 mm and 100 mm. Heat storage capacity of the building element used as hypocaust corresponds to 0.125°K temperature rise per hour in relation to the building heat load.     

Performance analysis of solar still with different energy-absorbing materials

Solar still is a simple device which can convert available waste or brackish water into potable fresh water by utilising solar energy. In the present research work, an attempt has been made to store excess heat energy in solar stills during the daytime for the continuation of the process at late evening and night hours for increment distillate output. To investigate the effect of energy storage materials on the productivity under the same climatic conditions, three same-size single-basin single-slope solar stills with an area of 1?m² made of fibre reinforced plastic (FRP) sheet were tested with 0.04?m layer of water level to investigate effects on solar still. Different energy storage materials like marble pieces and sandstones were used for easy availability and lower price. It has been found that sand stones are more productive compared with marble pieces and without materials inside solar still.     

Performance assessment of empirical models for prediction of daily and monthly average global solar radiation: the case study of Ibadan,Nigeria

In this study, the performance assessment of empirical models for modelling global solar radiation in Ibadan is presented. The empirical models are derived from the three basic models: Angstrom–Prescott model, Garcia model and Hargreaves–Sammani model. The data used in the analysis consist of daily average global solar radiation, daily average sunshine hours, daily average maximum temperature and daily average minimum temperature collected over a period of nine years (2000–2008). Regression constants are determined for each of the model for each months of the year. The study reveals that Garcia Quadratic model puts up the best overall performance. The model can predict the daily average global solar irradiation with Mean Absolute Error of 1.86?MJ?m^?2?day^?1, Root Mean Square Error of 2.7?MJ?m^?2?day^?1, Mean Absolute Percentage Error 9.34% and Coefficient of Determination (R²) of 0.68.     

Effect of co-digestion agricultural-industrial residues: various slurry temperatures

The main objective of this study is to investigate the effect of co-digestion using industrial-agro waste and operating temperature of digester slurry to enhance the biogas and methane yield. The anaerobic digestion process is carried out by using a floating dome type bio-digester with the capacity of 1?m³. The co-digestion of press mud and rice straw with the ratio of 1:1, slurry temperature mesophilic range of (30–40°C) and thermophilic raange of (41–55°C) is used in this study. The maximum generation of daily biogas and weekly methane yield obtained were about 190?L/day and 55% in the case of the thermophilic condition. The lowest generation of daily biogas and weekly methane yield obtained were about 130?L/day and 33% in the case of mesophilic condition. The 10 percentage of cow dung is used as an inoculum of the digester and 30 days of hydro retention time for both the temperature ranges. The methane and biogas yield is at its peak and there was a faster hydro retention time in thermophilic range temperature at 52°C.     

Water generation from atmospheric air by using different composite desiccant materials

In this communication, new composite desiccant materials having 37% concentration of CaCl₂ have been compared for water production from atmospheric air. The vermiculite–saw wood, jute and burnt-clay have been used as host materials and CaCl₂ as a hygroscopic salt. All the desiccant materials have been tested with the solar glass desiccant box type system (SGDBS) with a collector area of 0.36?m². Design parameters for water production are: height of the glass from the desiccant bed to be 0.22?m, an inclination angle of 30°, the effective thickness of the glass as 3?mm and the number of glazing is single. It has been found that on the experimental day, the maximum amount of fresh water generated by the vermiculite–saw wood/CaCl₂ is 130?ml/kg/day.