Enhancement of solar desalination by humidification-dehumidification technique

Water desalination and air conditioning consumes huge amount of energy that mostly come from fossil fuels, which produces harmful emissions detrimental to the environment. This work is concerned with the use of a new hybrid cooling and water desalination system driven by solar thermal energy. The system primarily consists of an evacuated tube solar collector, LiBr absorption chiller, and a humidification-dehumidification (HDH) unit. Seawater is used to cool the condenser and absorber of the chiller as well as the condenser of the HDH unit. The heat rejected by the absorber is used to drive the HDH unit. Thermodynamic model of the system has been formulated and simulated using engineering equation solver (EES) software. The results show that the coefficient of performance (COP) of the chiller nearly remain constant with increase in seawater temperature at the absorber inlet. The average COP of the chiller is found to be 0.76. The hybrid system efficiency increases with increase in the seawater temperature mainly due the effect of latent heat of water condensation. The rate of fresh water production increases with increase in the seawater inlet temperature. This resulted in a higher outlet temperature at the absorber exit, leading to a higher energy input to the HDH unit. Gained output ratio (GOR) increases with increase in seawater temperature. This is due to the direct proportionality of the GOR to the amount of fresh water produced. The results also revealed that increasing the flow rate of seawater causes the decrease in the fresh water production due to the corresponding decrease in the temperature of the seawater.

This paper presents field testing results and economics analysis at pilot scale for a humidification- dehumidification (HDH) process, described in SPE 169526, and to demonstrate that the process is viable and cost-effective, using solar, latent geothermal, and waste heat to augment the process for continuous operation. The HDH process drops produced water heated to 145–185°,F down chambers with up-blowing ambient air which humidifies the air at elevated temperatures to relative humidity >99%. The water- laden air then drops into adjacent cooling chambers and fresh water condenses out. Additional fresh water yield is achieved by using a secondary air-cooled condenser. To accomplish pilot test goals, a field scale prototype was constructed and tested at a field test site near Artesia, New Mexico, to determine operational parameters with solar heating, and then at the Federal 00 well in Eddy County, New Mexico, an oil well that produces ~20 BBLs of water per day, to test unattended operation and economics. The HDH unit was sized for the Federal 00's water production and can process 51 BBls of produced water per day. The field setup utilizes latent geothermal heat in the produced and heat is added to the water using an array of 16 flat plate solar panels. Heated water passes into an insulated storage vessel, which then feeds the HDH unit. When the solar panels are not generating heat, produced water is fed directly into the heated storage. At night or on cloudy days, additional heat can be supplied to the storage tank by burning waste gas. An Arduino controller manages the process flow, switches fluid flow as needed, and monitors tank levels. The HDH unit can purify ~20% of the inlet water on each pass, and the outlet concentrate, at ~125°F, can be cycled back into the hot water storage tank. The system was tested in summer and winter conditions. Winter conditions have drier inlet air, but less solar energy, and conversely summer has wetter inlet air, but more available solar heating. Summer tests yielded ~8-9 BBLs per day of purified water, and winter tests produced ~11 BBLs per day, for an annualized average of 10 BBLs per day, potentially cutting the disposal needed for the Federal 00 in half. Purification costs are primarily from electrical use of small pumps, a blower, and an air-cooled condenser. These average $3.82 per day, corresponding to ~$0.55 per barrel in summer and ~$0.35 per barrel in winter to purify water. Cost offsets from selling the fresh water and reduced disposal costs yielded an 85% reduction in annualized produced water handling costs.

Introduction: Lack of water and deterioration in the quality of soil and water resources are considered to be the prime cause of reduced crop yield in arid and semi-arid regions ‘More crop per drop’ by trickle irrigation, deficit irrigation, and uncommon water are the best strategies for mitigating water crises. Different irrigation management strategies are needed to increase production in different areas. In areas where sufficient water is available, a full irrigation strategy could be a suitable option, while in areas where water is limited, deficit irrigation would be an appropriate method, and finally in areas where water resources are saline, management strategies for achieving sustainable production as well as economic yields would be suitable. Maize is the third most important grain crop in the world following wheat and rice and it is the main source of nutrition for humans and animals. Because of the importance of maize in the world, increasing maize production under environmental stresses is a big challenge for agricultural scientists. Different methods of irrigation and the use of saline water that had satisfactory results for increasing agricultural production have been studied by several investigators . The main objective of this study was to establish an efficient use of limited water resources as well as to explore the possibility of replacing saline water with fresh water using different management techniques. Materials and Methods: A field experiment was conducted over two maize cropping seasons (2012–2013) in northern Iran (Gorgan Agricultural Research Station) to compare different alternate irrigation scenarios using saline water on corn yield, salinity and soil moisture distribution in a randomized complete block design with three replications. Treatments were: T1 and T2 = 100 and 50 % of crop water requirement with non-saline water, respectively; T3 and T4 = variable and fixed full irrigation with saline and non-saline water in every other row, respectively; T5 and T6= fixed and variable deficit irrigation with non-saline water in every other rows, respectively and T7= full irrigation with saline water. To create the desired water salinity (8 dS/m), non-saline well water (1.5 dS/m) and drainage water (20–35 dS/m) were blended in different proportions. A T-tape drip irrigation system (20 m in length) was used in the field experiment. Results and Discussion: In general, corn yield in 2013 was about 1270 kg ha-1 higher than in 2012. From the weather records it can be seen that the second year was drier than the first year. Yield analysis showed that deficit irrigation treatments (T2, T5 & T6) and also alternate salinity treatments (T3 & T4) did not significantly difference. In other words, the deficit irrigation management had no effect on yield. Corn yield in T3 and T4 with 50% of saved fresh water was just reduced to 7 and 1 % of T1, respectively. As a result, comparing treatments T3 and T4 with full irrigation have shown that treatments T3 and T4 are the best option. Comparison of moisture distribution in deficit irrigation treatments showed the highest water content in surface and deep layers was related to the treatments T6 and T2, respectively. The distribution of salinity in the soil profile for treatments T3 and T4 showed that after two years of irrigation with saline water, there is the possibility of use saline water for corn production, but drainage and leaching of soil will need to maintain sustainability. Conclusion: Naturally, in water scarce areas that use some strategic management such as deficit irrigation or saline water use, there is available arable farmland to further develop the irrigated area, and thereby increase total production. According to the results of the two-years where there was a shortage of water to meet crop water requirement and saline water was not available, the use of deficit irrigation managements as described in this study can save fresh water resources and increase total production and farmer's income. If the region is facing a shortage of water resources and saline water is available nearby agricultural land, it is suggested to use alternate furrow irrigation with saline and non-saline water; with the crop water requirement being met by the saline water, the total output will be higher than using deficit irrigation management with non-saline water. Comparision of the distribution of moisture in deficit irrigation treatments showed that surface soil moisture was lower in the treatment of T5 because it was more lateral distribution. In the deeper layers, soil moisture of the treatment T2 was more than others, because it was the predominant infiltration. The two treatments T3 and T4 because of the combined matric and osmotic potential and the movement of water along the sides and deep percolation, resulting widely distributed in soil moisture and thus remaining lower moisture in the soil compare to full irrigation treatments. Consequently, this finding indicates that after two years of corn irrigation using saline (8 dS/m) and non-saline water in every other row (treatments T3 and T4) production can be increased, and in case of proper leaching and drainage management, agricultural sustainability will also preserve.

Innovative and efficient integrations of desalination plants coupled absorption, adsorption, and humidification-dehumidification desalination units employing external heat recovery techniques

Experimental thermal investigation of bubble column humidification-dehumidification (BC-HDH) desalination combined with submerged water-source heat pump for different salinities, Taguchi analysis

برای بررسی اثر سطوح شوری آب آبیاری و زمان شروع آبیاری با آب شور و لب‌شور بر خصوصیات کمی خربزه دیررس، آزمایشی با 7 تیمار و 3 تکرار در قالب بلوک‌های کامل تصادفی با استفاده از روش آبیاری قطره‌ای نواری، در مرکز تحقیقات کشاورزی و منابع طبیعی خراسان رضوی انجام شد. تیمارهای آبیاری عبارت بودند از: 1- آبیاری با آب شیرین (6/0 دسی‌زیمنس بر متر) از ابتدای کاشت تا انتهای فصل برداشت، 2- آبیاری با آب با شوری 3 دسی‌زیمنس برمتر از ابتدا تا انتهای فصل داشت، 3-آبیاری با آب با شوری 6 دسی‌زیمنس بر متر از ابتدا تا انتهای فصل، 4- آبیاری با آب با شوری 6 دسی‌زیمنس بر متر از 20 روز بعد از جوانه‌زنی تا انتها، 5- آبیاری با آب با شوری 3 دسی‌زیمنس بر متر از 20 روز بعد از جوانه‌زنی تا انتها، 6- آبیاری با آب با شوری 6 دسی‌زیمنس بر متر از 40 روز بعد از جوانه‌زنی تا انتها و 7- آبیاری با آب با شوری 3 دسی زیمنس بر متر از 40 روز بعد از جوانه‌زنی تا انتهای فصل داشت. نتایج نشان داد که، شوری آب بر عملکرد کل، عملکرد اقتصادی و کارآیی مصرف آب آبیاری تاثیر معنی‌داری داشت. بالاترین عملکرد کل و عملکرد اقتصادی و کارآیی مصرف آب آبیاری از تیمار شاهد بدست آمد که تفاوت آن‌ها با تیمارهای آب شور و لب‌شور معنی‌دار بود. در ضمن تفاوت بین عملکردهای تیمارهای شور و لب‌شور معنی‌دار نبودند. آبیاری با آب شیرین در اوایل دوره رشد باعث افزایش محصول نشده بلکه، باعث وارد شدن تنش بیشتر به گیاه می‌شود.

This research presents the experimental and numerical results of a humidification dehumidification (HDH) unit driven by solar energy. The HDH unit is based in a CAOW water-heated configuration. The water is heated using solar thermal flat collectors. The desalination unit is located in the Renewable Energy Laboratory (LER) of the Universidad Técnica Federico Santa Maria (33°02’22.4“S 71°29’09.1”W) in Chile. The first section of the study is focused in the design of the solar HDH unit. The experimental facility has been instrumented and several operation parameters may be measured. Also, several variables may be adjusted to attempt finding an optimal performance. The modeling of the HDH unit is reviewed in the second section. The numerical model has been developed using Engineering Equation Solver (EES). The performance of the HDH unit is evaluated using mass and energy balances, and mass and heat transfer equations. Three loops are studied: water, air, and solar collector loop.

Salinity in soil and irrigation water is a major environmental stress in arid and semi-arid regions affecting soil organic carbon and its pools. A pot experiment was carried out in India to investigate distribution of soil carbon and its dynamic pools and nutrients under saline water irrigation in seed spice crops. Soil samples were analyzed for physicochemical properties (pH1:2, EC1:2), soil carbon (inorganic and organic), its pools (vey labile, labile, less labile and non-labile), and soil nutrients. Soil pH and EC varied between 7.70–8.72 and 0.45–8.25 dS m−1, respectively. Soil organic carbon and total soil carbon were higher by 15.2 and 22.4% with alternate application of saline and fresh water compared with continuous application of saline or fresh water and increased the less labile and non-labile carbon pools. Alternate application of saline and fresh water increased both the active and passive pools of carbon. Calcium carbonate and inorganic carbon were decreased by 35% with the continuous application of saline and fresh water. Similarly, alternate application of saline and fresh water increased carbon stock, carbon management index, and carbon pool index compared with sole application of fresh or saline water. Available nitrogen, phosphorous, and potassium varied from 310 to 629 kg ha−1, 39 to 87 kg ha−1, and 87 to 430 kg ha−1, respectively. Micronutrients were found to be highest with alternate application of saline and fresh water. Zinc, iron, manganese, and copper varied from 2.66 to 5.24, 2.64 to 6.67, 4.60 to 13.07, and 1.36 to 3.66 mg kg−1 soil, respectively. Alternate application of saline and fresh water helps in the build-up of soil carbon while maintaining the soil nutrient pools compared to sole application of saline or fresh water application.

چکیده کیفیت آب آبیاری در اکثر مناطق ایران پائین بوده و به درجات مختلف با شوری همراه می‌باشد که بروز خشکسالی این مشکل را تشدید کرده است. با اعمال مدیریت‌های صحیح کشاورزی می‌توان از این آبها برای کشت گیاهان متحمل و نیمه متحمل به شوری استفاده کرد. یکی از روش‌های مدیریتی جهت استفاده از آب‌های شور و لب‌شور، تلفیق آب شور و معمولی می‌باشد. هدف این تحقیق، بررسی چهار روش تلفیق آب شور (هدایت الکتریکی 11 دسی زیمنس بر متر) و معمولی (هدایت الکتریکی 2 دسی زیمنس بر متر) و تأثیر هر رژیم روی عملکرد و اجزای عملکرد دو رقم آفتابگردان بود. آزمایش به صورت کرت‌های خرد شده در قالب طرح بلوک کامل تصادفی با 4 تکرار اجرا گردید که در آن کرت‌های اصلی شامل 2 رقم آفتابگردان ( هایسان 33 و آلستار) بوده و در کرت‌های فرعی از 4 رژیم آبیاری (1ـ تیمار شور ـ معمولی، 2ـ تیمارآب معمولی ـ شور، 3ـ آبیاری یک در میان و 4ـ آبیاری مخلوط) استفاده شد. بذر هر دو رقم هایسان 33 و رقم آلستار، به طور مساوی در 32 کرت کاشته شده و از مرحله‌ی کاشت تا ساقه‌دهی گیاهان، سه مرتبه با آب معمولی جهت استقرار بهتر آبیاری شدند. بعد از این مرحله تا زمان برداشت برای آبیاری، رژیم‌های آبیاری مورد اشاره به کار گرفته شد. نتایج نشان داد که در میان چهار رژیم اعمالی، رژیم آبیاری شور ـ معمولی از نظر عملکرد روغن، وزن صد دانه، عملکرد دانه، عملکرد دانه در طبق، قطر ساقه، ارتفاع بوته، قطر طبق، مساحت برگ و املاح موجود در برگ بیشترین شاخص را داشته است. برای رقم هایسان 33 رژیم آبیاری یک در میان و برای رقم آلستار رژیم آبیاری مخلوط بعد از رژیم آبیاری شور ـ معمولی دارای بهترین عملکرد دانه و روغن بوده است. واژه های کلیدی: شوری، مدیریت آبیاری تلفیقی، آفتابگردان، عملکرد

A novel small dynamic solar thermal desalination plant with a fluid piston converter

In this paper, the cooling and freshwater generation performance of a novel hybrid configuration of a solid desiccant-based M-cycle cooling system (SDM) combined with a humidification–dehumidification (HDH) desalination unit is analysed and compared in three operational modes: ventilation, recirculation, and half recirculation. The HDH unit in this system recycles the moist waste air sourced from the M-cycle cooler and rotary desiccant wheel of the SDM system to enhance water production. A mathematical model was established and solved using TRNSYS and EES software. The results of this study indicate that the recirculation mode exhibited superior cooling performance compared to the other two modes, producing up to 7.91 kW of cooling load and maintaining a supply air temperature below 20.85 °C and humidity of 12.72 g/kg under various ambient conditions. All the operational modes showed similar water production rates of around 52.74 kg/h, 52.43 kg/h, and 52.14 kg/h for the recirculation, half-recirculation and ventilation modes, respectively, across a range of operating temperatures. The recirculation mode also exhibited a higher COP compared to the other modes, as the environmental temperature and relative humidity were above 35 °C and 50%. However, it should be noted that the implementation of the recirculation mode resulted in a higher water consumption rate, with a maximum value of 5.52 kg/h when the inlet air reached 45 °C, which partially offset the benefits of this mode.

Experimental and theoretical investigation on a hybrid LCPV/T solar still system

New experimental aspects of the carrier gas process (CGP)

Produced water (PW) treatment is a daunting significant challenge that continues to have negative impacts on the oil and gas industry, especially, small oil producers. The total dissolved solids (TDS) in produced water from most oil fields can be higher than 250,000ppm (parts per million) in concentration and may also contain a significant percentage of dissolved organic carbons. Many small oil producing companies operate at the edge of profitability; the current cost of treating a barrel of produced water can exceed $2.50 if the operator has to pay for hauling and disposal. This can make it uneconomical to operate mature producing wells which tend towards high watercuts. As part of a RPSEA (Research Partnership to Secure Energy for America) research project, a Humidification-Dehumidification (HDH) Unit (figure 3) has been built tested and optimized to treat PW using co-produced heat and active solar energy. This has very low electricity consumption and has been tested to process PW at a cost less than $0.50 per barrel if co-produced, or latent heat sources are used. The HDH Unit effectively treats produced water with varying degrees of inorganic dissolved solids concentration and yields fresh water with TDS in the neighborhood of 400ppm when optimized for maximum throughput which is suitable for most oil field activities, irrigation, and could satisfy other basic human needs of water. The existing 80ft3 HDH Unit can process about 50 barrels of PW per day with high total dissolve solids concentration, and reducing this waste stream into concentrated waste and fresh water. Each pass of PW through the system has approximately 19% efficiency with some variations due to changes in seasonal humidity and temperature. The process works using simple thermodynamic principles. Air (at atmospheric pressure) has the capacity to tremendously increase water vapor saturation pressure to about 50Kpa when the temperature is about 180°F. Consequently, the efficiency of the unit is primarily contingent on ambient temperature and relative humidity. The system uses the high solar radiations prevalent in the Southwest United States to heat PW to about 180°F which is then pumped into an 80ft3 stainless steel that has evaporation and condensation compartments; air is then pumped into the Unit through the opposite direction (to the water) for the humidification of the air at elevated temperature. The heated and humidified air is then cooled to or below dew point to produce fresh water.

Solar-powered water desalination is one of the promising approaches for addressing fresh water scarcity in the Middle-East, North Africa, and areas of similar climate around the world. Humidification-dehumidification (HDH) is a scalable, commercially-viable technology that primarily utilizes thermal energy in order to extract fresh water from a high salinity water source. Because of inherent variability and uncertainty in solar energy availability due to daily and seasonal cycles, solar-powered HDH desalination systems may benefit from installing thermal energy storage (TES). TES can allow higher utilization of the installed system components and thus reduce the overall lifecycle cost of fresh water production. This work presents a configuration for a HDH desalination system augmented by TES. The system is optimized using Genetic Algorithms (GA) for minimum total annual cost (TAC) per unit volume of produced potable water while satisfying a preset potable water demand. The optimum results for the same location and cost function are compared with results from a previous system which does not have TES. The comparison shows a considerable reduction in potable water production cost when TES is utilized in addition to the benefit of smaller variation in water production across the day.