Seawater bitterns as a source of liquid desiccant for use in solar-cooled greenhouses

Davies, Philip A.; Knowles, Paul

doi:10.1016/j.desal.2006.03.010

Cited by 46 publications

(31 citation statements)

References 17 publications

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“…Preliminary test results, including the amount of permeate (fresh water) collected from the laboratory tests, are shown in the following table (Table 7). The final concentration by weight of the CaCl 2 desiccant solution was used to estimate the equilibrium relative humidity of the solution [26].…”

Section: Hollow Fiber Vacuum MD Laboratory Resultsmentioning

confidence: 99%

Liquid desiccant dehumidification and regeneration process to meet cooling and freshwater needs of desert greenhouses

Lefers

Bettahalli

Nunes

et al. 2016

Desalination and Water Treatment

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20Agriculture accounts for ~70% of freshwater usage worldwide. Seawater desalination alone cannot meet 21 the growing needs for irrigation and food production, particularly in hot, desert environments. 22Greenhouse cultivation of high-value crops uses just a fraction of fresh water per unit of food produced 23when compared with open field cultivation. However, desert greenhouse producers face three main 24 challenges: fresh water supply, plant nutrient supply and cooling of the greenhouse. The common 25 practice of evaporative cooling for greenhouses consumes large amounts of fresh water. In Saudi 26Arabia, the most common greenhouse cooling schemes are fresh water-based evaporative cooling, 27 often using fossil groundwater or energy-intensive desalinated water, and traditional refrigeration-28 based direct expansion cooling, largely powered by the burning of fossil fuels. The coastal deserts have 29 ambient conditions that are seasonally too humid to support adequate evaporative cooling, 30 necessitating additional energy consumption in the dehumidification process of refrigeration-based 31cooling. This project evaluates the use of a combined-system liquid desiccant dehumidifier and 32 membrane distillation unit that can meet the dual needs of cooling and fresh water supply for a 33 greenhouse in a hot and humid environment. 34

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Section: Hollow Fiber Vacuum MD Laboratory Resultsmentioning

confidence: 99%

Liquid desiccant dehumidification and regeneration process to meet cooling and freshwater needs of desert greenhouses

Lefers

Bettahalli

Nunes

et al. 2016

Desalination and Water Treatment

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show abstract

“…are corrosive to metals. This limits the reliability of the system, putting serious issues in term of system longevity and related costs [17], which prevents the worldwide development and utilisation of LDAC systems. In the case of solution carry-over, the corrosion of liquid desiccant will not just influence the piping and the solution heat exchanger, but also any downstream metallic component involved in the transport of the air, such as ducting, solution heat exchanger, etc., sensibly reducing the lifespan of the equipment [38].…”

Section: Corrosionmentioning

confidence: 99%

“…Moreover, since the development of the Liion batteries the price of Lithium-based salts is largely increased [32]. Conversely, CaCl2 and MgCl2 solutions present a lower dehumidification potential but they are extremely cheap and readily available because produced from industrial processes and as a by-product from seawater processing, respectively [17]. The HCO2K price still represents a sensible economic saving respect LiCl and LiBr solutions.…”

Section: Economics Of Liquid Desiccantmentioning

confidence: 99%

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Thermodynamics and economics of liquid desiccants for heating, ventilation and air-conditioning – An overview

Giampieri

Smallbone

et al. 2018

Applied Energy

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In an effort to minimise electricity consumption and greenhouse gases emissions, the heating, ventilation and airconditioning sector has focused its attention on developing alternative solutions to electricallydriven vapour-compression cooling. Liquid desiccant airconditioning systems represent an energyefficient and more environmentally friendly alternative technology for dehumidification and cooling, particularly in those cases with high latent loads to maintain indoor air quality and comfort conditions. This technology is considered particularly efficient in hot and humid climates. As a matter of fact, the choice of the desiccant solution influences the overall performance of the system. The current paper reviews the working principle of liquid desiccant systems, focusing on the thermodynamic properties of the desiccant solutions and describes an evaluation of the reference thermodynamic properties of different desiccant solutions to identify which thermodynamic, physical, transport property influences the liquid desiccant process and to what extent. The comparison of these thermodynamic properties for the commonly used desiccants is conducted to estimate which fluid could perform most favourably in the system. The economic factors and the effect of different applications and climatic conditions on the system performance are also described. The paper is intended to be the first step in the evaluation of alternative desiccant fluids able to overcome the problems related to the use of the common desiccant solutions, such as crystallization and

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“…Therefore it could be used potentially as a liquid desiccant in solar refrigeration systems providing low grade cooling in particular systems for cooling greenhouses in hot and humid climates. Davies (2005) theoretically demonstrated a solar powered liquid desiccant cooling system that lowers summer maximum summer temperatures by 5 o C. The use of bitterns (brines rich in Mg +2 ) as the liquid desiccant in such a system was proposed by Davies and Knowles (2006). The feasibility of the system has to be investigated thoroughly at the laboratory scale by conducting experiments.…”

Section: Introductionmentioning

confidence: 99%

A Solar Powered Liquid-Desiccant Cooling System for Greenhouses

Lychnos

Davies

2008

Acta Hortic.

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Liquid desiccant systems are of potential interest as a means of cooling greenhouses to temperatures below those achieved by conventional means. However, only very little work has been done on this technology with previous workers focussing on the cooling of human dwellings using expensive desiccants such as lithium salts. In this study we are designing a system for greenhouse cooling based on magnesium chloride desiccant which is an abundant and non-toxic substance. Magnesium chloride is found in seawater, for example, and is a by-product from solar salt works. We have carried out a detailed experimental study of the relevant properties of magnesium rich solutions. In addition we have constructed a test rig that includes the main components of the cooling system, namely a dehumidifier and solar regenerator. The dehumidifier is a cross-flow device that consists of a structured packing made of corrugated cellulose paper sheets with different flute angles and embedded cooling tubes. The regenerator is of the open type with insulated backing and fabric covering to spread the flow of desiccant solution. Alongside these experiments we are developing a mathematical model in gPROMS® that combines and simulates the heat and mass transfer processes in these components. The model can be applied to various geographical locations. Here we report predictions for Havana (Cuba) and Manila (Philippines), where we find that average wet-bulb temperatures can be lowered by 2.2 and 3°C respectively during the month of May.

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Seawater bitterns as a source of liquid desiccant for use in solar-cooled greenhouses

Cited by 46 publications

References 17 publications

Liquid desiccant dehumidification and regeneration process to meet cooling and freshwater needs of desert greenhouses

Liquid desiccant dehumidification and regeneration process to meet cooling and freshwater needs of desert greenhouses

Thermodynamics and economics of liquid desiccants for heating, ventilation and air-conditioning – An overview

A Solar Powered Liquid-Desiccant Cooling System for Greenhouses

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