Adsorption Desalination Cycle Research Articles

Performance investigations of hybrid adsorption and thermo electric dehumidification desalination system

In recent years, thermally driven Adsorption Desalination Systems (ADS) have been gaining attention as an eco-friendly and energy saving solution for water scarcity. However, ADS faces challenges related to low water productivity and scalability issues associated with the adsorbent. To overcome these challenges, it is advantageous to integrate ADS with other desalination technologies, thereby creating a decentralised, small-scale hybrid desalination system. The current study introduces an innovative approach to enhance the performance of ADS by integrating it with a Thermo Electric Dehumidification (TED) unit that utilises the cold side of Thermo Electric Coolers (TECs). The proposed hybrid system is designed to operate at the elevated evaporator temperature ranges from 35 °C to 60 °C. This is achieved by connecting the hot side of the TECs to the evaporator of the ADS. This approach facilitates a fundamental shift from the conventional adsorption desalination cycle, enabling the system to work at higher evaporator temperature and pressures. A small-scale hybrid ADS integrated with a Thermo Electric Dehumidification unit (hybrid AD-TED desalination system) has been designed and developed to investigate performance parameters such as Coefficient of Performance (COP) and water productivity. Experimental study of the hybrid AD-TED system has been carried out in two operating modes: open flow and closed flow modes of water between the hot side of TEC and the evaporator. These operating modes are tested with and without implementing humidification process in the humidifier. The results have shown that the hybrid AD-TED desalination system working in open flow mode with humidification process has produced the highest water productivity of 1.25 l during one cycle of operation, lasting one hour. Furthermore, when operating in open flow mode without humidification, the hybrid AD-TED system can generate dehumidified air within a temperature range of 16–28 °C, making it suitable for cooling applications. Closed flow mode is the preferred choice for desalination applications. In the closed flow mode with and without humidification condition, the water productivity is found to be 1.15 l/hr and 1.05 l/hr, respectively. The significant feature of this hybrid AD-TED system is that it can be operated in two working modes with an elevated adsorption desalination cycle, making it a unique option compared to the single operating mode of standalone ADS in desalination and cooling applications. The study also compares the elevated adsorption desalination cycle with the conventional adsorption desalination cycle and reveals that the elevated cycle increases water uptake by 45 %.

Experimental analysis on hybrid adsorption and open air cycle humidification dehumidification (AD–OHD) desalination system

In the current status, an Adsorption Desalination System (ADS) has been found to have lower water production capacity than conventional desalination technologies. This study proposes a hybrid desalination system integrating the Adsorption (AD) and Open air cycle Humidification-Dehumidification (OHD) process to overcome the challenge of lower water production capacity in ADS. This hybrid system known as AD-OHD system comprises of a single bed ADS and a Humidification-Dehumidification (HDH) unit. The main objective of this work is to analyse the performance of the hybrid AD-OHD system based on parameters such as Gain Output Ratio (GOR) and amount of desalinated water production. The performance of the hybrid AD-OHD system is studied under three different operating conditions of switching (tswt) and sorption time (tspt), namely, tswt > tspt, tswt = tspt, and tswt < tspt. The results indicate that the optimal working condition is achieved when the hybrid AD-OHD system operates at condition tswt < tspt. The amount of desalinated water and GOR under the optimal condition is found to be 1.12 l/h and 0.78, respectively. The study also conducts experimental investigations to evaluate the GOR of the hybrid AD-OHD system under different operating conditions, including the temperature of the water entering the evaporator and the temperature of the hot and cooling water input to the adsorbent bed. Experimental data indicates a positive correlation between GOR and hot water temperatures, while increased cooling water temperature reduce GOR due to reduced adsorption behaviour. Although the evaporator inlet water temperature initially boosts GOR, it declines as the adsorption capacity diminishes. The study highlights the superior performance of the hybrid AD-OHD system compared to both the standalone single-bed ADS and open cycle HDH desalination systems. The hybrid AD-OHD desalination system exhibits an 80 % improvement over the single-bed ADS system and a 50 % improvement over the open cycle HDH system in desalinated water production. Additionally, a theoretical model of the adsorption desalination cycle is developed and validated, demonstrating the viability of the AD-OHD system for desalination applications.

Improving the photovoltaic/thermal (PV/T) system by adding the PCM and finned tube heat exchanger

In this study, we aimed to improve the performance of the photovoltaic-thermal (PV/T) system by incorporating phase change material (PCM) into the heat exchanger. A new design for the finned tube heat exchanger layout was introduced, and a comprehensive mathematical model was developed to analyze the heat transfer process and operational efficiency of the PV/T system. The temperature variation of the PV/T system was simulated and validated using real climatic conditions in Baghdad and Tehran. To conduct our analysis, we utilized the OpenFOAM software and enhanced our solver to accurately capture the melting process in the PCM. We also investigated the effects of wind velocity and atmospheric pressure on the performance of the PV/T system. Our findings showed that an increase in wind velocity led to an increase in PV/T efficiency, while an increase in atmospheric pressure resulted in a decrease in efficiency. Additionally, we observed that the Baghdad climate was more sensitive to variations in wind velocity compared to Tehran. In Baghdad and Tehran, the highest obtained water temperatures were 54.3 and 50.1 °C, respectively. Furthermore, a study was conducted to assess the viability of using PV/T (photovoltaic-thermal) technology for hot water production in the Multi-Effect Desalination and Adsorption Desalination cycle. The proposed PV/T system demonstrated an average performance improvement of 26% compared to traditional PV/T systems. During warmer months, the system was capable of producing 0.11 and 0.10 m3/h of potable water per month in Baghdad and Tehran, respectively. Furthermore, the system had the potential to generate 170 and 140 kW h of electricity for the respective cities.

Comparative analysis of four metal-organic frameworks for adsorption desalination

The adsorption desalination cycle is a promising technique to address water scarcity. However, its production rate is low due to the low capacity of adsorbent materials. In this study, four metal organic frameworks namely aluminum fumarate, MOF–801, MIL–100(Fe), and CAU–10 H are synthesized and characterized and are tested for an application in adsorption desalination. After synthesizing the adsorbents, powder x-ray diffraction patterns for the samples are obtained to ensure a successful synthesis. The samples then undergo thermogravimetric water adsorption measurements at three different temperatures of 30 °C, 50 °C, and 70 °C at varying evaporator pressures. The water adsorption isotherms are also correlated with the Sun-Chakraborty adsorption isotherm model. It is found that the maximum water uptakes of aluminum fumarate, MOF–801, MIL–100(Fe), and CAU–10 H are 0.47, 0.35, 0.72, and 0.31 kg of water/kg of adsorbent, respectively. The highest water uptake of MIL–100(Fe) is due to its largest BET surface area and pore volume of 1634 m2/g and 0.47 m3/g, respectively. Consequently, MIL–100(Fe) provides the highest specific daily water production for adsorption desalination. Adsorption desalination cycles using MIL–100(Fe) could produce 2.2 and 2.3 times the freshwater obtained employing silica gel and CAU–10 H, respectively, with a heat recovery loop between the evaporator and condenser sections.

Novel synergetic integration of supercritical carbon dioxide Brayton cycle and adsorption desalination

High ambient conditions and high energy desalination technologies could penalize power cycle performance and this synergistic integration is proposed as a solution to address this challenge. A novel integration of closed loop recuperative supercritical carbon dioxide Brayton cycle with low temperature adsorption desalination cycle is investigated. Brayton cycle provides the heat source for the adsorption desalination cycle and the latter provides the cooling required for heat rejection in Brayton cycle. The integrated system is modeled and the performance is analyzed through energy, exergy analysis, and parametric studies. Finally, the integrated system performance is compared against a stand-alone cycle and literature for performance gains. A maximum improvement of about 9.1%, 21.1%, and 10.7% for energy efficiency, exergy efficiency, and overall system effectiveness were observed for the lowest chilled water temperature of 25 °C over typical ambient conditions of 35 °C. Maximum specific daily water production and specific cooling output at these conditions were 11.3 kgofwaterkgofSG and 195 WkgofSG, an improvement of about 26% and 28% over typical ambient conditions. Finally, overall system effectiveness improvement of about 14.3% over a stand-alone system is achieved, compared to a maximum of 10% improvement for supercritical carbon dioxide and multi-effect desalination integrations. Better performance improvement achieved at lower turbine inlet temperatures compared to multi-effect systems warrant the advantage of synergetic integration of power cycles like the supercritical carbon dioxide Brayton cycle with less energy-intensive adsorption desalination.

Experimental optimization of the cycle time and switching time of a metal organic framework adsorption desalination cycle

The thermally driven adsorption desalination cycle has been considered a promising solution to mitigate the gap between freshwater needs and demands. Silica gel and zeolite are commonly used in the cycle however, they have low capacity. So, metal–organic framework adsorbents have been proposed as a replacement for silica gel and zeolite. Performance of the adsorption desalination cycle using metal–organic framework materials has been extensively investigated numerically with limited available experimental measurements in the open literature. In this work, a lab-scale adsorption desalination cycle using heat recovery was built using a metal organic framework (CPO-27(Ni)) as an adsorbent. Effect of the cycle time, switching time, condenser type, and cooling water temperature is assessed from the viewpoint of the cycle’s specific daily water production and gained output ratio. This investigation aims to specify the optimal cycle time and switching time. The experimental measurements identify that the optimal cycle time and switching time are 12 min and 30 s, respectively. At these conditions, the cycle produces a specific daily water production of 9.5 m3/ton/day at a gained output ratio value of 0.46. Using a coil condenser is found to be more efficient than using a finned-tube condenser. The specific daily water production decreases by 26% and the gained output ratio drops by about 22% when the cooling temperature increases from 15 to 35 °C. The present results indicate the importance of optimizing the operating conditions to achieve higher efficiency.

A novel cycle for adsorption desalination system with two stages-ejector for higher water production and efficiency

In this paper, a novel hybridization between adsorption desalination cycle and two ejectors is proposed to increase the freshwater productivity by several folds. Silica gel/water is used as a working pair for this integration. The proposed hybrid system, donated as AD2EJ, has two sorption beds, two evaporators, two condensers, and two ejectors. Performance of the hybrid cycle is evaluated numerically in terms of specific daily freshwater production (SDWP) and Coefficient of Performance (COP). Mathematical models of the adsorption desalination cycle and ejectors are validated. The numerical results reveal that the optimal half-cycle time is about 400 s, at which the SDWP of the AD2EJ system is calculated as 23.0 m3 per ton of silica gel at a COP of 1.64 using a regeneration temperature of 85 °C. This amount of freshwater is 3 times higher than that of the basic adsorption desalination system (ADS). Further enhancement is achieved by linking the condenser and evaporator of the AD2EJ cycle via an internal heat recovery circuit. The SDWP of this system (AD2EJ-HR) is found to be 79.4 m3/ton at a COP of 2.22 at a regeneration temperature of 95 °C and 400 s half-cycle time.

A new approach integration of ejector within adsorption desalination cycle reaching COP higher than one

For the first time, ejector technology has been integrated with the adsorption technology in a single cycle to increase productivity of desalinated water. In this paper an innovative idea of allocating an ejector before the condenser of an adsorption water desalination system is presented. This work lays down the basic rules for using ejector technology along with the adsorption technology. The innovative hybrid system has been investigated theoretically to work under different conditions of driving and cooling temperatures. Employing the ejector with heat recovery between the condenser and the evaporator has been also studied. The idea of employing the ejector within the adsorption desalination cycle has proved its worth where the daily water productivity is increased by 51% using the ejector if heat recovery has been considered. A desalinated water of 16 and 40 m3/day/ton of silica gel have been achieved by integrating the ejector with and without heat recovery respectively at 95 °C driving temperature. The coefficient of performance of the cycle has been also increased by employing the ejector alongside the heat recovery where it's reached a value of 1.1.

An Improved Multievaporator Adsorption Desalination Cycle for Gulf Cooperation Council Countries

AbstractIn Gulf Cooperation Council (GCC) countries, cogeneration‐based desalination processes consume almost 25 % of the total annual energy, and this number increases annually by 2.2 %. The high demand for fresh water can be attributed to the high gross domestic product growth rate, 24 %, and high water languishes, which are more than 10 %. Over the past two decades, GCC countries have spent tens of billions of dollars to expand their present and planned desalination capacities. It is foreseeable that with a business‐as‐usual scenario, the domestic oil consumption of Saudi Arabia may exceed its production capacity by 2040. Innovative and sustainable water production solutions are urgently needed for future water supplies without an environment impact. In this paper, a hybrid desalination cycle is proposed by integrating a cascade evaporator (CE) system with an adsorption (AD) cycle. In this new innovative cycle, desorbed vapors from the AD are supplied to the CE to exploit the latent condensation energy within the evaporators arranged in both pressure and temperature cascades to improve the performance ratio of the cycle. Water production is improved more than tenfold with the hybrid cycle relative to that observed for the conventional AD cycle owing to a synergetic effect. This concept is demonstrated in a laboratory pilot plant with a cascade of three evaporators and simulation of eight evaporators.

Experimental investigation of adsorption water desalination/cooling system using CPO-27Ni MOF

Although many adsorbent materials have been used in adsorption systems, only silica-gel was tested experimentally for desalination applications. This work experimentally and numerically investigates the use of CPO-27(Ni) an advanced Metal Organic Framework-MOF adsorbent material in a 1-bed adsorption system for water desalination and cooling applications. Operating parameters as switching time, half cycle time, evaporator and condenser water inlet temperatures were studied to investigate their effects on cycle water production and cooling. Moreover, a mathematical simulation model is developed, validated and used to predict cycle outputs at other operating conditions. Results showed that as evaporator temperature increases and condenser temperature decreases, cycle outputs increase. Also, it was shown that adsorption desalination cycles can work with condenser pressure lower than evaporator pressure as the cycle is an open loop one (i.e. no refrigerant is flowing back from condenser to evaporator). A water production of 22.8m3/tonne·ads/day was achieved using 40°C evaporator temperature, 5°C condenser temperature and 95°C desorption temperature. Similar water production can be achieved using 30°C condensing temperature but at 120°C desorption temperature. For space cooling applications (Tevap<20°C), cycle cooling produced was found to be 65Rton/tonne·ads. This work highlights the potential of using advanced MOF materials for water desalination/ cooling applications.

Performance investigation on a 4-bed adsorption desalination cycle with internal heat recovery scheme

Multi-bed adsorption cycle with the internal heat recovery between the condenser and the evaporator is investigated for desalination application. A numerical model is developed for a 4-bed adsorption cycle implemented with the master-and-slave configuration and the aforementioned internal heat recovery scheme. The present model captures the reversed adsorption/desorption phenomena frequently associated with the unmatched switching periods. Mesoporous silica gel and water vapor emanated from the evaporation of the seawater are employed as the adsorbent and adsorbate pair. The experimental data and investigation for such configurations are reported for the first time at heat source temperatures from 50°C to 70°C. The numerical model is validated rigorously and the parametric study is conducted for the performance of the cycle at assorted operation conditions such as hot and cooling water inlet temperatures and the cycle times. The specific daily water production (SDWP) of the present cycle is found to be about 10m3/day per tonne of silica gel for the heat source temperature at 70°C. Performance comparison is conducted for various types of adsorption desalination cycles. It is observed that the AD cycle with the current configuration provides superior performance whilst is operational at unprecedentedly low heat source temperature as low as 50°C.

Water quality assessment of solar-assisted adsorption desalination cycle

This study focuses on the water quality assessment (feed, product and brine) of the pilot adsorption desalination (AD) plant. Seawater from the Red Sea is used as feed to the AD plant. Water quality tests are evaluated by complying the Environmental Protection Agency (EPA) standards with major primary and secondary inorganic drinking water pollutants and other commonly tested water quality parameters. Chemical testing of desalinated water at the post desalination stage confirms the high quality of produced fresh water. Test results have shown that the adsorption desalination process is very effective in eliminating all forms of salts, as evidenced by the significant reduction of the TDS levels from approximately 40,000ppm in feed seawater to less than 10ppm. Test results exhibit extremely low levels of parameters which are generally abundant in feed seawater. The compositions of seawater and process related parameters such as chloride, sodium, bromide, sulfate, calcium, magnesium, and silicate in desalinated water exhibit values of less than 0.1ppm. Reported conductivity measurements of desalinated water are comparable to distilled water conductivity levels and ranged between 2 and 6μS/cm while TOC and TIC levels are also extremely low and its value is less than 0.5ppm.

Performance investigation of advanced adsorption desalination cycle with condenser–evaporator heat recovery scheme

Energy or heat recovery schemes are keys for the performance improvement of any heat-activated cycles such as the absorption and adsorption cycles. We present two innovative heat recovery schemes between the condensing and evaporating units of an adsorption desalination (AD) cycle. By recovering the latent heat of condenser and dumping it into the evaporative process of the evaporator, it elevates the evaporating temperature and hence the adsorption pressure seen by the adsorbent. From isotherms, this has an effect of increasing the vapour uptake. In the proposed configurations, one approach is simply to have a run-about water circuit between the condenser and the evaporator and a pump is used to achieve the water circulation. This run-around circuit is a practical method for retrofitting purposes. The second method is targeted towards a new AD cycle where an encapsulated condenser–evaporator unit is employed. The heat transfer between the condensing and evaporative vapour is almost immediate and the processes occur in a fully integrated vessel, thereby minimizing the heat transfer resistances of heat exchangers.

Numerical simulation and performance investigation of an advanced adsorption desalination cycle

Low temperature waste heat-driven adsorption desalination (AD) cycles offer high potential as one of the most economically viable and environmental-friendly desalination methods. This article presents the development of an advanced adsorption desalination cycle that employs internal heat recovery between the evaporator and the condenser, utilizing an encapsulated evaporator–condenser unit for effective heat transfer. A simulation model has been developed based on the actual sorption characteristics of the adsorbent–adsorbate pair, energy and mass balances applied to the components of the AD cycle. With an integrated design, the temperature in the evaporator and the vapor pressurization of the adsorber are raised due to the direct heat recovery from the condenser, resulting in the higher water production rates, typically improved by as much as three folds of the conventional AD cycle. In addition, the integrated design eliminates two pumps, namely, the condenser cooling water and the chilled water pumps, lowering the overall electricity consumption. The performance of the cycle is analyzed at assorted heat source and cooling water temperatures, and different cycle times as well as the transient heat transfer coefficients of the evaporation and condensation.

Thermo-physical properties of silica gel for adsorption desalination cycle

Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A++) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer–Emmett–Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A++ silica gel (granular type) possesses the highest surface area of 863.6 m2/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A++ silica gel exhibits a highest equilibrium uptake at 537 cm3/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles.

Study on an advanced adsorption desalination cycle with evaporator–condenser heat recovery circuit

This paper presents the results of an investigation on the efficacy of a silica gel–water based advanced adsorption desalination (AD) cycle with internal heat recovery between the condenser and the evaporator. A mathematical model of the AD cycle was developed and the performance data were compared with the experimental results. The advanced AD cycle is able to produce the specific daily water production (SDWP) of 9.24 m 3/tonne of silica gel per day at 70 °C hot water inlet temperature while the corresponding performance ratio (PR) is comparatively high at 0.77. It is found that the cycle can be operational at 50 °C hot water temperature with SDWP 4.3. The SDWP of the advanced cycle is almost twice that of the conventional AD cycle.