Performance Evaluation of a Solar Still Integrated with a Greenhouse

Transcription

1 Performance Evaluation of a Solar Still Integrated with a Greenhouse Shristhi Shrestha 1, Sarad Shrestha 2, Pradip Bawari 3 1 Lecturer Electrical and Electronic, Centre for Computer and Communication Technology. Chisopani, South Sikkim 2,3 Bachelor in Mechanical Engineering, Bengal Engineering and Science University Abstract : The present work discusses the performance evaluation of a solar still integrated with a greenhouse for the climatic conditions of Gangetic Bengal which witness a hot and humid climate for greater part of a year. A thermal model as available in literature [3] has been used for analyzing the performance of the greenhouse integrated solar still for the climatic conditions of Gangetic Bengal. Plant and water temperature, as a function of climatic and design parameters, were obtained by solving coupled single-order differential equations using the Runge-Kutta method. A computer code has been developed using MATLAB software to compute the greenhouse room air temperature, temperature of the transparent cover, basin liner temperature and the mass of the distillate along with the plant and water temperature. The study revealed that the maximum amount of distillate production took place in the month of April and is significantly high during the other summer months. This distillate can be used as potable water for use in rural areas where it is scarce. Thus, this integrated system reinforces the viability of generation of substantial amount of fresh water along with sustainable crop production in the rural parts of Gangetic Bengal in Indian subcontinent. Keywords Stand still, green house, solar distillation, Runge Kutta I. INTRODUCTION In India the solar radiation is abundant and the climate in the plains is rather hot and dry for greater part of a year especially during the summer, while the coastal parts witness a hot and humid climate. The excessive heat is detrimental to the growth of the plants. So for a greenhouse installation located in the plains of Gangetic Bengal, the main objective is cooling. Also in the plains of Indian subcontinent, there is considerable scarcity of potable water. In the present work a greenhouse has been considered to be integrated with a solar still to facilitate a conducive microclimate for the growth of plants and simultaneous production of fresh water which can be utilized for drinking and irrigation. Thus, solar distillation unit integrated with greenhouse system may be a viable solution not only to provide the modest demand of good quality water to closed system cultivation, but also to maintain controlled temperature by reducing the effect of sensible heat load addition to the greenhouse. All the incoming solar radiation may not be the cooling load for the greenhouse. About 2% of the total transmitted solar radiation is used in photosynthesis. Though the rate of transpiration varies from crop to crop but 48% of the transmitted solar radiation is used for this process [2]. The rest of the 50% of solar radiation needs to be removed by the cooling system. The utilization of that 50% solar radiation in the distillation system in conjunction with greenhouse provides dual advantages of reducing cooling load for the greenhouse and also supplying fresh water to the inside plants [2]. If this technology is successfully implemented, the desalination of water can be produced in a cost effective manner and also our dependence on fossil fuels for desalination can be reduced. II. BASIC BLOCK OF THERMAL MODEL A. SOLAR ENERGY Solar energy, radiant light and heat from the sun, has been harnessed by human beings since ancient times using a range of ever-evolving technologies. Solar Energy is clean and environmental friendly renewable energy source. Solar energy is very large and inexhaustible. The power from the sun intercepted by the earth is about 1.8 x 1011 MW [1], which are many thousands of times larger than the present consumption rate of all commercial energy sources. Its major advantage is that it is an environmentally clean source of energy and is free and available in adequate quantities in almost all parts of the world. Solar energy technologies include solar heating, solar photo voltaic, solar thermal electricity and solar architecture, which can make considerable contributions to solving some of the most urgent problems the world now faces. B. SOLAR STILL: Fresh water is the essence of life and is a basic human requirement for domestic, industrial and agricultural purposes. Increasing human activities like urbanization, population explosion, pollution caused by industrial, agricultural and domestic wastes have resulted in large escalation in demand for fresh water in the recent years. Solar still can be ISSN: Page 151

2 a method of production of pure water. The technology for distillation of water using solar energy was known to mankind since long. Earlier designs attempted to generate salt from the sea water. Documented use of solar stills began only in the sixteenth century for production of fresh potable water and to purify liquids [2]. An early large-scale solar still was built in 1872 to supply drinking water to a mining community in Chile. Mass production occurred for the first time during the Second World War when 200,000 inflatable plastic stills were made to be kept in life-crafts for the US Navy [2]. The solar still is a model of the water cycle on earth comprising of evaporation, condensation and precipitation. Solar still uses the greenhouse effect to trap energy from the Sun. Distillation can be a simple process heat is first added to a liquid to evaporate it and form vapour. Then heat is removed from the vapour to condense it back to liquid. The incident solar radiation is transmitted through the glass cover and is absorbed as heat by a black surface in contact with the water to be distilled. The water is thus heated and gets converted into water vapour. The vapour condenses on the glass cover, which is at a lower temperature due to contact with ambient air and this condensed water is pure which runs down into a gutter from where it is ultimately fed to a storage tank. C. GREENHOUSE Optimal growth of plants results when favourable environmental conditions in terms of temperature, humidity, intensity of light and carbon dioxide prevail. Thus, every type of flora grows successfully in a typical season. Greenhouse can be defined as an artificially constructed sophisticated structure that provides near to ideal conditions for plant growth and production round the year. Inside environment of a greenhouse is controlled by controlling the plant growth factors like light, temperature, humidity, air composition, air circulation rate etc. Cultivation of crops in greenhouse is increasing from high altitude and temperate regions to the warmer regions of tropics and subtropics. During summer months, cooling is considered to be the basic necessity for greenhouse crop production in tropical and subtropical regions to overcome the problems of high temperatures. III. LITERATURE REVIEW A lot of research and development works have been carried out in greenhouse cum solar still and related technologies for decades together and quite a good number of publications are available in the literature. Srivastava and Tiwari [3] developed a thermal model for performance evaluation of a distillation-cum-greenhouse system as a function of design and climatic parameters. Numerical computations were carried out for a typical day in January for Chennai, India. Plant and water temperatures, as a function of climatic and design parameters, were obtained by solving two simultaneous single-order differential equations using the Runge-Kutta method. Greenhouse air, transparent cover, basin liner temperature and distillate output were also worked out by using the value of plant and water temperature. Analysis showed that there was a significant effect in the plant, water temperatures and distillate output due to a change in the fraction of the solar radiation incident on the north wall, depth of water, and the inclination of the roof whereas the heat capacity of the plant had a marginal effect on the temperatures and distillate output. The study revealed that vegetables can be grown in a warm and humid climate in a coastal region by the construction of a distillation-cum-greenhouse unit. Eugenio et al. [4] studied the performance of a solar still integrated in a greenhouse for Mediterranean climatic conditions in south-eastern Spain. The desalination module was equipped with 28 water basins located at the top of an experimental greenhouse. The inner surface of the roof was used as a condensation surface and the fresh water produced was collected in a storage tank. Fresh water production and hourly variation of the distillate were evaluated. Contrary to what happens in traditional solar stills, distillation took place after solar noon and during the night due to the low absorption of solar irradiation when the solar still is integrated into a greenhouse. They concluded that installation of solar still reduced the radiation inside the greenhouses the temperature in crop area stayed below the proper limits. The solar still integrated in a greenhouse roof did not produce a considerable amount of fresh water compared to conventional solar stills, nor did it follow the same distillation pattern. This is because it was necessary to use transparent basins to transmit the maximum solar radiation to the crop area. Radhwan et al.[5] presented an experimental investigation of the thermal performance of an agricultural greenhouse with a built-in solar distillation system. A set of solar basins with saline water were placed on the greenhouse roof to reduce the greenhouse cooling load and to produce the required fresh irrigating water by solar distillation. The ventilation air entered the greenhouse through an evaporative cooler for cooling in summer, and was partially recirculated for heating in winter. The combined greenhouse-solar distillation system utilized abundant solar energy in hot climates to partially reduce greenhouse cooling load in summer, and to partially produce required irrigation water by solar distillation. The results indicated that the greenhouse inside temperature was 8 to10 degrees less than the ambient temperature. Chaibi et al. [6] carried out a study to analyze differences in seasonal crop yields between greenhouses with solar-still desalination and conventional roofs in arid climates because in greenhouses with roof-integrated water desalination, solar transmission is reduced by an absorbing glass sheet covered by a layer of flowing ISSN: Page 152

3 water and a top glass sheet. A simulation model of the thermal and optical performance of this system was detailed. The yield reduction was about 25% for a desalination case with the capacity to cover the water demand corresponding to a lettuce crop. Goosen et al. [7] developed a thermodynamic model with an aim to develop humidification dehumidification desalination technology for farms in arid coastal regions who suffer from salt infected soils and shortages of potable groundwater. The specific aim of their research was to determine the influence of greenhouse-related parameters on a process, called Seawater Greenhouse, which combines fresh water production with growth of crops in a greenhouse system. A thermodynamic model was developed based on heat and mass balances. The dimension of the greenhouse had the greatest overall effect on the water production and energy consumption. Sablani et al.[8] performed a thermodynamic simulation study on the influence of greenhouse-related parameters on a desalination process that combines fresh water production using humidification-dehumidification with the growth of crops in a greenhouse. In this system, the surface seawater trickles down a porous front wall evaporator through which air is drawn into the greenhouse. The saturated air passes through a condenser, which is cooled using cold deep seawater or cool seawater coming out of the evaporators. Analyses showed that the dimensions of greenhouse (i.e., width to length ratio) had the greatest overall effect on water production and energy consumption. The overall water production rate increased from 65 to 100 m3.d-1 when the width to length ratio increased from 0.25 to Similarly the overall energy consumption rate decreased from 4.0 to 1.4 kwh.m-3 when the width to length ratio increased from 0.25 to Ghosal et al. [9] developed a mathematical model for the analysis of solar desalination system combined with a greenhouse for both composite and warm humid climate of India. They derived analytical expressions for water temperature, greenhouse room air temperature, glass cover temperature, flowing water mass flow rate over the glass cover, hourly yield of fresh water and thermal efficiency in terms of design and climatic parameters for a typical day of summer and winter period. Temperature rise of flowing water mass with respect to distance and time in solar still unit were also incorporated in the mathematical modeling. The yield of fresh water was found to be higher in warm humid climate than composite climate. It was found that the yield and the fall in greenhouse maximum room air temperature decreased with increase of flow rate. The yield in Chennai (warm humid climate) was higher than that in Delhi (composite climate). A detailed simulation model was developed for analysis of the thermal and optical characteristics of the desalination system concept by Chiai [10]. The work described laboratory experiments with a small roof module and presented measurements compared to simulations obtained in order to validate the thermal model of the system. The laboratory work was carried out with artificial light from a solar simulator operated in a nicely controlled thermal environment. The main conclusion was that a good agreement was obtained between simulated and measured variations of fresh water production values for various design and operational parameters of the system. The most important indication was that geothermal water at elevated temperatures combined with this roof technology was the alternative with the highest water production capacity. M.T. Chiai [11] presented a simulation model for fresh water production and derived performance parameters for a water desalination system integrated in a greenhouse roof. Several typical daily weather patterns taken from a 10-year period for three arid regions in Tunisia were analyzed.the most important conclusion was that the roof-integrated still concept had a fresh water production capacity on a sufficient level for irrigation of plants in a greenhouse environment. Thermal modeling, based on heat and mass transfer relations, of a greenhouse integrated with a solar still were discussed in details by Lawrence et al. [12].The effect of the system (viz. heat capacity of plants/pot mixture, water mass, and orientation, etc.) as well as climatic parameters (solar insolation, ambient air temperature and ventilation due to wind, etc.) were incorporated in the energy balance for various components of the system in order to validate the theoretical results. An experiment was carried out for a typical greenhouse in Port Moresby. It was observed that the amount of distilled water obtained was sufficient to grow the plants inside the greenhouse. K.Voropoulos et al. [13]experimentally investigated the validity of a basic model widely used for the simulation of dynamic behaviour of solar stills in the case of a real-scale greenhouse-type still. The different modes of heat and mass transfer were analyzed on the basis of continuous measurements of the main working parameters of the still. Davies et al. [14] developed a prototype seawater greenhouse which combined a solar desalination system within environment for cultivating crops in which transpiration is minimized. Results from the prototype greenhouse were used to calibrate a computational fluid dynamic model. The model was used to evaluate three proposed options for improving the performance. Sampath Kumar et al. [15] reviewed different studies on active solar distillation system. Thermal modelling was done for various types of active single slope solar distillation system. From this review of literature, it is inferred that considerable work in terms of experimental and model development have been done with respect to greenhouse integrated solar still in the last few decades. ISSN: Page 153

4 IV. THERMAL MODEL DEVELOPMENT A schematic diagram of a solar still integrated greenhouse, indicating the solar energy absorbed by the roof and wall is shown in Fig. 1. The absorbed solar radiation by the basin liner is partially transferred to water mass and the rest is transferred to the greenhouse through conduction, convection and radiation. The stored energy in the water causes evaporation of the same, which later condenses to form fresh water. The remaining solar energy that is transmitted is absorbed by the plants and the floor. The absorbed energy is finally transferred to the air inside the greenhouse through convection and radiation from the plants and thus the greenhouse air gets heated. A part of the energy absorbed by the floor is also conducted to the ground. Fig1. Schematic diagram of a solar still integrated with greenhouse A. Basic Assumption: Following assumptions have been made while developing the thermal model of the greenhouse integrated solar still: i) The analysis is based upon quasi-steady-state condition. ii) Heat capacity of air inside the greenhouse is neglected in comparison to the heat capacity of plants. iii) Properties of the plant mass have been considered to be equivalent to water mass for all thermal analyses proposed due to a high content of water in the plant. iv) Moist air in the solar still and greenhouse cover, solar still bottom, plant and soil surfaces are saturated. v) No stratification in temperature of the basin liner, water, transparent cover, plant and greenhouse enclosure has been considered due to the low unit operating temperature range. vi) Ground heat loss from the floor to the ground is considered in the steady-state mode. B. Thermal Model Development : In this section a thermal model as available in literature [3] has been used for analysing the performance of the greenhouse integrated solar still for the climatic conditions of Gangetic Bengal. The details of the thermal model have been discussed in the subsequent paragraphs. Table I: Input Parameters to the Thermal Model SL. Area Value(m 2 ) SL. Area Value(m 2 ) No. No. 1 A d 3 6 A r A e 15 7 A s 45 3 A g 90 8 A sr 52 4 A n 45 9 A w 18 5 A nr A p 200 The energy balance for the different components of the solar still-cum-greenhouse is as follows: Basin liner: The amount of energy incident in the form of radiation is partly absorbed by the water mass and the rest is transferred to the room. Thus, mathematically (1) The L.H.S of Eq. (1) denotes the rate of energy absorbed by the basin liner, while the first term in R.H.S of Eq. (1) represents the rate of energy transferred to the water and the second term represents the rate of energy transferred to the room. In Eq. (1), denotes the absorptive of the solar still basin, denotes the transmissivity of the basin liner and represents the transmissivity of the water mass,represents the fraction of solar radiation which is incident on the roof of the greenhouse, while is the Convective heat transfer coefficient from basin liner to water. In the present work the value has been considered to be 0.2 [3], and has been considered to be 0.9 [3] and has been taken as 100 W/m2 0C [3]. Water mass: The amount of energy available in water is partly stored in water as thermal energy and the rest is transferred from water to the transparent cover. Thus mathematically, The L.H.S of Eq. (2) denotes rate of energy absorbed by the water mass while the first term in R.H.S of Eq. (2) represents rate of energy transferred to water mass by conduction and the second term represents the rate of energy transferred to the condensing cover. In Eq. (2) h1 denotes the overall heat transfer coefficient from water to the condensing cover whose value in has been assumed to be 12.5 W/m2 0C [3]. Condensing cover: The amount of energy available to the transparent cover from the water is lost to the surrounding by radiation. Thus mathematically, (3) The L.H.S of Eq. (3) denotes rate of thermal energy available on condensing cover from water mass while R.H.S of Eq. (3) denotes the rate of thermal energy lost from transparent cover to ambient. It denotes the convective and radiative heat transfer coefficient from cover to ambient. In the present work, its value has been assumed to be 9.5 W/m2 0C [3]. ISSN: Page 154

5 Greenhouse plants: The amount of solar flux absorbed by the plants is partly stored as thermal energy within the plants and the remaining part of it is radiated, convected and evaporated to the greenhouse. Thus mathematically, (4) L.H.S of Eq. (4) represents the rate of solar flux absorbed by plants in the greenhouse, while the first term in R.H.S of Eq. (4) denotes the amount of solar energy stored by plant and the second term denotes the rate of thermal energy transferred to the greenhouse by radiation, convection and evaporation. In Eq.(4) α p denotes the absorptivity of the plant, F n denotes the transmitted fraction of solar energy available to north wall, τ denotes the relative humidity, S w the intensity of solar radiation available on the wall and h p represents the heat transfer coefficient between the plant and enclosure air of the greenhouse. In present work the value of α p, and have been considered to be 0.4, 0.2, 0.05 and 0.7 [3] respectively. The value of has been considered to be 5.7 W/m2 0C [3]. Greenhouse floor: The amount of solar flux available to the floor is conducted and convected to the enclosed air of the greenhouse. Thus mathematically, The L.H.S of Eq. (5) denotes rate of solar energy absorbed by the greenhouse floor and the first term in R.H.S denotes rate of energy transferred to the greenhouse by conduction and the second term denotes the rate of energy transferred to the greenhouse by convection. In Eq. (5) denotes the absorptivity of the floor is the heat transfer coefficient between the floor and the air of the greenhouse. In the present work the value of has been considered to be 0.3 [1] and the value of has been considered to be 5.7 W/m 2 0 C [1]. Greenhouse enclosed air: The amount energy available to the enclosed air of the greenhouse from the sun, plants, floor and basin liner is partly transferred to the room by convection and radiation, partly stored in the room and rest lost to the ambient from canopy cover, door and ventilators. Thus mathematically, The first term in L.H.S of Eq. (6) denotes rate of solar energy absorbed by enclosed air of the greenhouse, second term denotes rate of energy radiated, convected and evaporated from plants to enclosed air of the greenhouse and the third term denotes rate of energy transferred to enclosed air by radiation and convection. The first term in R.H.S of Eq. (6) denotes rate of thermal energy stored by greenhouse air and the final term denotes rate of energy lost by the greenhouse air to ambient through canopy cover, door and ventilators. In Eq. (6) is the overall heat transfer coefficient from inside of the greenhouse to ambient through walls and roofs, is the heat transfer coefficient between room air and ambient through the door of the greenhouse, is the number of air changes taking place in the greenhouse to maintain the required condition, is the volume of greenhouse and denotes the evaporative heat transfer coefficient from the plant to the enclosed room. In our present work as per our assumptions ~ 0.0 and the value of N has been taken as 1 [1]. Also, and are considered to be 5.4, 3.99, W/m 2 0 C [1]. Our objective is to find the plant temperature, and water temperature, from the six equations which have been deduced from the energy analysis of the model [1]. We substitute the other temperature terms (viz.,,, ) by expressing them as a function of plant temperature and water temperature. Doing so we get two differential equations in terms of and which can be represented as follows: + + = (t) (7) And + + = (t) (8) In Eq. (7) = - ( ) / ( ) (9) = ( + - ) /( (10) In Eq. (8) (11) (12) (13) (14) Here denotes absorptivity, is product of absorptivity and denotes the fraction of solar energy absorbed by the plants. In Eq. (9) (15) In Eq. (10) In eq. (11) (16) (17) (18) (19) ISSN: Page 155

6 (20) (21) (22) In Eq. (12) (23) In Eq. (20), The fraction of solar energy absorbed by greenhouse air is given by, (24) The fraction of solar energy absorbed by greenhouse floor is given by, (25) And the fraction of solar energy absorbed by basin liner is given by, (26) In Eq. (21) (27) The value of and can be worked out from Eq. (7) and Eq. (8) by application of classical fourth order Runge - Kutta method by using the input parameter of table 1 [1] and the climatic condition as provided [1]. After knowing the value of the plant and water temperature, the other parameters like the value of the enclosed room air temperature, condensing cover's, basin liner temperature,, and the mass of the distillate output can be determined with the help of following expressions: (28) (29) (30) (31) In Eq. (31) denotes the rate of evaporative heat transfer from water surface to the condensing cover. Now, (32) is the mass of distillate output. RESULT AND CONCLUSION Computer codes were generated using MATLAB software to analyse the performance of the system using the thermal model discussed above. The model considers ambient temperature and intensity of solar radiation as input and predicts the greenhouse room air temperature, condensing cover temperature, basin liner temperature and the mass of the distillate for a given set of constant parameters. In present work the analysis has been done for three different months representing three different seasons of a year, while cumulative distillate output has been computed and presented graphically for all the months of a year. Fig 2 shows the hourly variation of intensity of global and diffused solar radiation for a representative day in April in Kolkata. The same has been used to calculate the sensible heat load to the system. As evident from the figure, the solar radiation intensity increases from 6:00 AM to 12 Noon and then it again decreases. The maximum solar intensity of radiation is about 776 W/m2. The graph also shows the hourly variation of corresponding ambient temperature which also shows a similar trend, first increasing with time of the day, reaching a peak and then again decreasing. Fig. 2: Hourly variation of solar intensity It, Id and ambient temperature Ta for a typically warm and humid day of April. Fig3 shows the variation of plant and water temperature for the month of April considering the data plotted in Fig.2. It is observed that there is a significant variation in water temperature and the maximum temperature reaches nearly to 50 0 C around 3 PM which leads to better evaporation of water from the still resulting in higher amount of distillate. It is also found that the plant temperature varies very less compared to the variation in ambient temperature and water temperature. It is seen from the curve that the development of a greenhouse integrated solar still. Fig.3: hourly variation of plant temperature (Tp) and water temperature (Tw) of a day in April. Fig 4 shows the hourly variation of intensity of global and diffused solar radiation for representative day in June (representing hot and humid climate) in Kolkata. The same has been used to calculate the sensible heat load to the system. As evident from the figure, the solar radiation intensity increases from 6:00 AM to 12 Noon and then it again decreases. The maximum solar radiation intensity is around 659 W/m2 at 12 noon and the maximum ambient temperature is 35 0 C at 1:30 PM. ISSN: Page 156

7 Fig. 4 Hourly variation of solar intensity It, Id and ambient temperature Ta for a typically warm and humid day of June. Fig.5 shows the variation of plant and water temperature for the month of June considering the data plotted in Fig.4 as input. It is observed that there is a significant variation in water temperature and the maximum temperature reaches nearly to 47 0 C around 3 PM which leads to better evaporation of water from the still resulting in higher amount of distillate. It is also found that the plant temperature varies very less compared to the variation in ambient temperature and water temperature. It is seen from the curve that the plant temperature varies between 28 to 32 0 Cwhich is very conducive for cultivation. Fig.5 : Hourly variation of plant temperature (Tp) and water temperature (Tw) in a day of June. Fig 6 shows hourly variation of intensity of global and diffused solar radiation for a representative day in November (representing hot and humid climate) in Kolkata. The same has been used to calculate the sensible heat load to the system. As evident from the figure, the solar radiation intensity increases from 6:00 AM to 12 Noon and then it again decreases. The maximum solar radiation intensity is only about 560 W/m2 at 12 noon and the maximum ambient temperature is 30 0C at 1:30 PM. and the maximum temperature reaches nearly to 31 0 C around 3 PM which leads to better evaporation of water from the still resulting in higher amount of distillate. It is also found that the plant temperature varies very less compared to the variation in ambient temperature and water temperature similar to what is observed for the month of April and June. It is seen from the curve that the plant temperature varies between 18 to 26 0 C which is very conducive for cultivation of target plants. Fig.7: Hourly variation of plant and water temperature in a day of November. Considering the three cases discussed above it can be seen that there is a little difference between the plant and greenhouse inside air temperature especially during the off peak hours of a day. With the increase in ambient temperature, the room air temperature increases and thus the plant temperature also increases. The maximum plant temperature is recorded in between 1:00 pm and 2:00 pm. After this interval the plant temperature begins to decrease. The water temperature increases with the increase in solar intensity of radiation. Also, as the ambient temperature increases with the time of the day, the heat transfer rate increases and thus the water temperature also increases. Fig 8 shows the monthly variation of mass of distillate output in Kolkata. The mass of distillate increases during the first three months and attains a maximum value in April with a collection of approx kg of distillate. There is a marginal decrease in distillate production in May followed by a sharp increase in the month of June. Again in September, the mass of the distillate production increases and after that it goes on decreasing for subsequent months. It is maximum for the month of April as in the month of April the intensity of solar radiation is high coupled with high ambient temperature and low relative humidity which favours quick evaporation of water from the solar still which later condenses to give fresh water. Fig. 6 Hourly variation of solar intensity It, Id and ambient temperature Ta for day in November. Fig7 shows the variation of plant and water temperature for the month of June considering the data plotted in Fig.6 as input. It is observed that there is a significant variation in water temperature ISSN: Page 157

8 Fig.8: Monthly variation of mass of distillate output. V. SUMMARY OF WORK AND CONCLUSION In this project work, a thermal model of a greenhouse integrated solar still as available in literature [3] has been presented and analyzed for the climatic conditions of Gangetic Bengal that witness abundant solar radiation for greater part of a year. From the study it is observed that for various seasons of a climatic cycle, the variation in greenhouse inside air and plant temperature is much less compared to the temperature of the water in the solar still. This will help to maintain a favourable climate in the greenhouse for cultivation of target flora and at the same time maximize the yield of fresh water through distillation. The results of the thermal model also indicate that the distillate output is maximum during the month of April and is significantly higher during the summer months which can be used for generation of potable water for use in rural areas where it is scarce. Thus, this integrated system reinforces the viability of generation of substantial amount of fresh water using solar energy which would otherwise increase the cooling load on the structure along with cultivation of target plantation in greenhouses in the rural parts of Gangetic Bengal in Indian subcontinent. [12] Yusuf Bilgiç, Cengiz Yıldız"The Effect of Extended Surfaces on the Heat and Mass Transfer in the Solar Distillation Systems", International Journal of Engineering Trends and Technology (IJETT), V22(3), April ISSN: published by seventh sense research group REFERENCES [1] P.K Nag, Power Plant Engineering, Tata McGraw Hill Publication. [2] Available online at (accessed on 11/10/2012) [3] N.S.L. Srivastava, M. Din, G.N. Tiwari, Performance evaluation of distillation-cum- greenhouse for a warm and humid climate Desalination 128 (2000) pp [4] Eugenio García Marı, Rosa Penélope Gutiérrez Colomer, Carlos Adrados Blaise-Ombrech, Performance analysis of a solar still integrated in a greenhouse, Desalination 203(2007) pp [5] Abdulhaiy M. Radhwan, Hassan E.S. Fath, Thermal performances of greenhouses within built in solar distillation system: Experimental study Desalination 181(2005) pp [6] M.T. Chaibi, T. Jilar, Effects of a Solar Desalination Module integrated in a Greenhouse Roof on Light Transmission and Crop Growth Bio-systems Engineering (2005) 90(3), pp [7] M.T. Chaibi, T. Jilar, System design, operation and performance of roof-integrated desalination in greenhouses Solar Energy 76 (2004) pp [8] M.F.A. Goosena, S.S. Sablania, C. Patonb, J. Perreta, A. Al- Nuaimic,I. Haffara, H. Al- Hinaid, W.H. Shayya, Solar energy desalination for arid coastal regions: development of a humidification dehumidification seawater greenhouse Solar Energy 75 (2003) pp [9] S.S. Sablani, M.F.A. Goosen, C. Patonb, W.H. Shayya, H. Al- Hinai, Simulation of fresh water production using a humidification-dehumidification seawater greenhouse Desalination 159 (2003) pp [10] M.K. Ghosal, GN. Tiwari, N.S.L. Srivastava, Thermal modeling of a controlled environment greenhouse cum solar distillation for composite and warm humid climates of India Desalination 151 (2002) pp [11] M.T. Chiai, Validation of a simulation model for water desalination in a greenhouse roof through laboratory experiments and conceptual parameter discussions Desalination 142 (2002) pp ISSN: Page 158