Hybrid Solar-Driven Desalination/Cooling Systems: Current Situation and Future Trend

: Global warming and climate change, accompanied and assisted by rapid economic and population growth, are causing a sharp rise in cooling demands and stressing the already-limited supply of freshwater for many countries worldwide, especially those developing under hot-climate conditions. Thus, it is imperative to ﬁnd solutions to meet cooling and freshwater needs without negatively affecting the environment and exacerbating the global warming problem. Solar-driven hybrid desalination/cooling technologies are a promising solution that can help in reducing greenhouse gas emissions and increasing overall efﬁciency and energy savings. The present study summarizes research efforts in meeting cooling and freshwater demands using the available solar resources. Various solar desalination technologies, such as multi-effect distillation (MED), single and multi-stage ﬂash (MSF), reverse osmosis (RO), adsorption, absorption desalination, and membrane distillation (MD), and their integration with different cooling technologies, are reported. The study reported system performance indicators, such as water production rate, cooling capacity, Coefﬁcient of Performance, and freshwater cost.


Introduction
The increasing cooling and freshwater demands directly result from rapid economic and population growth, especially in developing countries with arid and hot climate conditions, which are a significant source of greenhouse gas emissions [1].Fossil fuel-based direct and indirect separate-production (SP) technologies are used extensively to supply these demands worldwide, which lead to massive energy waste and greenhouse gas emissions exacerbating the global warming (GW) problem [2,3].Electricity needs for powering different conventional heating, ventilation, and air conditioning (HVAC) technologies represent the dominant share of electricity consumption, especially in hot-climate countries [4].Since electricity production is still mainly dominated by fossil fuel power plants in these countries, the greenhouse gas emissions and GW problem is aggravated, leading to yearly rising temperatures, which require more cooling and electricity demand, and therefore, the cycle continues.
Furthermore, freshwater represents less than 3% of all available water on earth [5,6].However, this limited freshwater supply is not distributed fairly between all countries, and most of it journeys back to oceans and underground reservoirs.Additionally, the rising GW problem is disrupting the natural water cycle and threatening many countries with severe droughts and famine.That is why sustainable access to freshwater has been recognized as one of the great engineering challenges of the 21st Century.Consequently, numerous research efforts and different commercial technologies have been developed over the years to obtain freshwater from unconventional sources, such as seawater desalination and atmospheric water harvesting (AWH) [7][8][9][10].Unfortunately, most commercial desalination plants operating worldwide currently are powered by fossil fuels, and it is estimated that energy-intensive desalination technologies are consuming about 75.2 TWh annually.The expected equivalent CO 2 emissions from desalination plants will reach approximately 218 million tons annually by 2040.About 54 billion m 3 of freshwater is expected to be supplied worldwide by desalination technologies by 2030 [11].
Increasing the energy efficiency of current cooling and desalination technologies, while relying on renewable energy sources to supply the required electricity and heat for these technologies, is considered one solution to the greenhouse gas emissions and GW problem.Additionally, using integrated hybrid cooling/desalination systems helps in increasing driving energy utilization efficiency and improve energy and exergy efficiencies.Moreover, powering the hybrid systems by renewable energy sources, such as solar energy or wind, could also be an ultimate answer to meeting cooling and freshwater demands in a sustainable and green way.Therefore, significant research attention has been drawn to renewable energy-based hybrid desalination/cooling technologies in the last few decades [12].
Solar energy is a very abundant and clean energy source, especially for hot climate countries, and can be used for electricity production and heat supply without harmful impacts on the planet [13,14].It is estimated that about 140,000 TW of solar radiation is received daily by the Earth's surface, with the potential for utilizing 36,000 TW of them in useful applications [15,16].Hybrid solar-powered desalination and cooling systems represent a great option for countries with abundant solar radiation to supply the required cooling loads and freshwater needs without negatively affecting the planet, and in addition to the economic benefits; the energy source is available and free.
Cooling technologies powered by solar energy can be classified into electricity-driven technologies by the electricity generated by Photovoltaic (PV) or Photovoltaic/thermal (PVT) solar collectors or thermally-powered technologies driven by captured thermal energy [17][18][19][20].The main electrically-powered solar cooling technologies are conventional vapor compressionbased systems [21,22] or, to a lesser extent, thermoelectric systems [23,24].In contrast, the thermally-powered cooling technologies are sorption-based cooling systems, such as adsorption and absorption chillers [25,26], and thermomechanical systems, such as ejectors or Rankine cycles [27,28].Figure 1 illustrates the main solar cooling technologies reported in the literature.The desalination process is known for its energy-intensive nature, in which the excess total dissolved solids (TDS) are eliminated either by water evaporation/condensation using thermal energy or by using membranes.The main commercial desalination technologies available worldwide can currently be classified into thermal technologies, such as multi-stage flash (MSF) and multi-effect distillation (MED) [29,30], or membrane-based technologies, such as reverse osmosis (RO) [31].However, researchers have innovated many new and hybrid desalination technologies over the years to increase the efficiency of desalination technologies and reduce their energy requirements and carbon emissions.The main thermal and membrane desalination technologies are reported in Figure 2.  According to the literature review, a limited number of reviews have summariz and reported on solar hybrid cooling and desalination systems.Therefore, this revie summarizes recent studies for solar hybrid and cooling and desalination systems, a puts emphasis on their advantages over SP standalone systems in terms of energy a exergy efficiencies.Based on the perspectives above, this review paper summarizes a discusses state-of-the-art hybrid solar-powered desalination and cooling technologi According to the literature review, a limited number of reviews have summarized and reported on solar hybrid cooling and desalination systems.Therefore, this review summarizes recent studies for solar hybrid and cooling and desalination systems, and puts emphasis on their advantages over SP standalone systems in terms of energy and exergy efficiencies.Based on the perspectives above, this review paper summarizes and discusses state-of-the-art hybrid solar-powered desalination and cooling technologies.The paper is organized as follows: (i) Section 2 reports the recent advances in the integration of solar-powered adsorption desalination-cooling technologies; (ii) hybrid solar-powered RO desalination technologies with different cooling systems have been reviewed in Section 3; (iii) Section 4 summarizes the hybrid integration between solar-powered humidificationdehumidification (HDH) systems and different cooling technologies; (iv) Section 5 discusses the integration between MED system and different cooling technologies powered by solar energy; (v) Section 6 assesses the integration between solar-driven single-stage flash (SSF) desalination systems and various cooling technologies; (vi) membrane distillation (MD) desalination technologies integrated with different cooling systems are summarized in Section 7; (vii) and finally, the main conclusions and future recommendations are outlined in Section 9.

Solar Sorption Desalination/Cooling (SSDC) Systems
Thermally-powered sorption-based desalination and cooling systems, such as adsorption (SADDC) systems [32], have been considered by numerous researchers over the years to supply cooling and freshwater needs due to their many advantages.Their ability to be driven by low-temperature energy sources makes them perfect candidates for solar energy or waste heat utilization.Furthermore, adsorption-based systems have been reported to be able to supply cooling and fresh water by utilizing heat sources at temperatures as low as 50 • C [33].These features have attracted numerous researchers to experimentally and theoretically investigate these systems to enhance their performance [34][35][36][37][38][39][40][41][42].Various adsorbent materials have been developed to increase freshwater productivity and cooling production in adsorption systems [43][44][45][46][47].The main examples of adsorbent materials used with water for adsorption desalination/cooling systems are silica gel (SG), Metal-Organic Frameworks (MOF), Zeolites, and activated carbons as innovative composite adsorbents to help improve the system performance [48][49][50][51][52].
Ng et al. [53] expressed the solar adsorption desalination-cooling (SADDC) cycle performance experimentally derived by solar collectors (SCs).The SADDC outcomes produced chilled water at 7-10 • C with a specific cooling power (SCP) from 25 to 35 RT/ton SG .Simultaneously, the SADDC system produces a specific daily water production (SDWP) from 3 to 5 m 3 /ton SG , with a performance ratio (PR) from 0.8 to 1.1.Alsaman et al. [54] designed a new proposed SADDC system, as illustrated in Figure 3, and experimentally tested it in Egypt's weather conditions using a commercial SG as an adsorbent material.The SADDC outcomes reported that the average SCP, SDWP, and coefficient of performance (COP) were 112 W/kg, 4 m 3 /ton SG , and 0.45, respectively.The COP is defined as the evaporator capacity divided by driving energy input.
Ali et al. [55] studied the effect of employing the SADDC system in Egypt's weather conditions by using TRNSYS numerical software.The theoretical results revealed that the maximum SDWP, SCP, and COP were 10 m 3 /ton SG , 134 W/kg, and 0.5, respectively.The SDWP and SCP were increased by 70% using the optimum working conditions with the same system design and materials.Elsheniti et al. [56] explored the thermal and adsorption characteristics of aluminum fumarate (AL-Fum) MOF and SG adsorbents on the performance of the SADDC system.Raj and Baiju [57] studied SADDC operating and performance parameters under equilibrium conditions.The condenser, cooling, and regeneration temperatures significantly impacted water production (WP), COP, and energy consumption, as the highest SADDC outcomes could be achieved at the lowest cooling and condensation water temperatures and highest regeneration temperatures.Table 1 summarizes the main research regarding the adsorption desalination/cooling (ADC) systems.

Solar Reverse Osmosis/Cooling (SROC) Systems
Reverse osmosis desalination technology is currently the leading desalination system (60% worldwide) due to its economic performance compared to other conventional thermal desalination technologies, such as the MED and MSF technologies [10].The RO desalination system is driven by electrical power to operate the high-pressure pumps.Consequently, RO systems are considered a perfect candidate to be powered by solar energy via the generated electricity by PV or PVT collectors [31,83].Numerous researchers have investigated the integration of solar-powered conventional RO desalination systems and different cooling technologies to obtain a higher energy efficiency multigeneration system and/or increase its freshwater productivity.
Ali et al. [84] investigated a novel hybrid reverse osmosis-adsorption desalination and cooling (RO-AD) system, as shown in Figure 4, to evaluate the reutilizing of RO brine using an ADC unit for enhancing WP recovery by 25%.The RO-ADC system had a 100 W/kg SG SCP with a COP of 0.46.Hassan et al. [85] investigated an SROC system comprising PVT/evacuated tube hybrid solar collectors driving RO and adsorption chiller for cooling production under Alexandria, Egypt; climate conditions are illustrated in Figure 5.The system with 100% PVT collectors had annual energy savings of 32.95 MWh and an emissions cut of 18.06 ton CO2 , with a 10.3 years payback period.

Harby et al.
[86] investigated a new hybrid RO-absorption desalination and cooling (RO-ABDC) system, as illustrated in Figure 6, to evaluate the reutilizing of RO brine using an ABDC unit for enhancing WP recovery.The results indicated an increase in RO-ABDC system recovery and water quality by about 72.86% and 59.3%, respectively, reducing electricity consumption by 49.1% compared to the single RO system.Additionally, the system can produce a 0.346 kW cooling capacity (CC), 0.77 COP, and 13.89 m 3 potable water per day.

Harby et al.
[86] investigated a new hybrid RO-absorption desalination and cooling (RO-ABDC) system, as illustrated in Figure 6, to evaluate the reutilizing of RO brine using an ABDC unit for enhancing WP recovery.The results indicated an increase in RO-ABDC system recovery and water quality by about 72.86% and 59.3%, respectively, reducing electricity consumption by 49.1% compared to the single RO system.Additionally, the system can produce a 0.346 kW cooling capacity (CC), 0.77 COP, and 13.89 m 3 potable water per day.

Harby et al. [86] investigated a new hybrid RO-absorption desalination and cooling
(RO-ABDC) system, as illustrated in Figure 6, to evaluate the reutilizing of RO brine using an ABDC unit for enhancing WP recovery.The results indicated an increase in RO-ABDC system recovery and water quality by about 72.86% and 59.3%, respectively, reducing electricity consumption by 49.1% compared to the single RO system.Additionally, the system can produce a 0.346 kW cooling capacity (CC), 0.77 COP, and 13.89 m 3 potable water per day.Hunt et al. [87] investigated a combination of RO desalination and seawater air conditioning (SWAC) to produce drinkable and chilled water.The results found that the system can produce a CC of 49 MWth and desalinated water of 1 m 3 /s with 12 MWe electrical consumption (EC).Hussain [88] investigated a hybrid desalination-cooling system in Kuwait.The hybrid system was analyzed by integrating RO and MSF desalination systems with absorption refrigeration (ABR) and vapor compression (VC) refrigeration air conditioners.The hybrid RO-ABR system provided the highest fuel savings.Assareh et al. [89] investigated a hybrid RO-ABR system, as displayed in Figure 7.It provided potable water, cooling/hot water, and electricity.The study results illustrated that the system produced 9147 kW of electricity and 240.23 m 3 of potable water.Additionally, the cost rate and the exergy efficiency (EEF) were 10.41 $/GJ and 20.52%, respectively.
Abbasi et al. [90] studied a novel hybrid system using an RO desalination unit and ABR cycle for generating power, fresh water, and cooling.Energy storage by a Phase Change Material (PCM) was investigated for the night work.Organic Rankine Cycle (ORC) was employed to recover the gas turbine's output heat (GT).The maximum EEF, energy, and total product cost rate were 14.40%, 40.52%, and 30.524 $/GJ, respectively.The CC and WP were about 1.62 MW and 5209.5 m 3 /day, respectively, with electricity of 2.4 MW.The electricity levelized cost was 0.234 $/kWh, demonstrating encouraging performance.Hunt et al. [87] investigated a combination of RO desalination and seawater air conditioning (SWAC) to produce drinkable and chilled water.The results found that the system can produce a CC of 49 MW th and desalinated water of 1 m 3 /s with 12 MW e electrical consumption (EC).Hussain [88] investigated a hybrid desalination-cooling system in Kuwait.The hybrid system was analyzed by integrating RO and MSF desalination systems with absorption refrigeration (ABR) and vapor compression (VC) refrigeration air conditioners.The hybrid RO-ABR system provided the highest fuel savings.Assareh et al. [89] investigated a hybrid RO-ABR system, as displayed in Figure 7.It provided potable water, cooling/hot water, and electricity.The study results illustrated that the system produced 9147 kW of electricity and 240.23 m 3 of potable water.Additionally, the cost rate and the exergy efficiency (EEF) were 10.41 $/GJ and 20.52%, respectively.
Abbasi et al. [90] studied a novel hybrid system using an RO desalination unit and ABR cycle for generating power, fresh water, and cooling.Energy storage by a Phase Change Material (PCM) was investigated for the night work.Organic Rankine Cycle (ORC) was employed to recover the gas turbine's output heat (GT).The maximum EEF, energy, and total product cost rate were 14.40%, 40.52%, and 30.524 $/GJ, respectively.The CC and WP were about 1.62 MW and 5209.5 m 3 /day, respectively, with electricity of 2.4 MW.The electricity levelized cost was 0.234 $/kWh, demonstrating encouraging performance.

Solar Humidification-Dehumidification/Cooling (SHDC) Systems
The Humidification-Dehumidification (HDH) desalination system is one type of thermal desalination method that works similarly to the natural rain cycles and is usually used as a small-scale desalination technology that can work with different salinity levels.The HDH system comprises a humidifier, in which the air is moistened by direct contact with hot saline water.In the dehumidifier, the air is cooled with indirect contact with the cool saline water before it enters the humidifier, leading to the condensation of the freshwater [91,92].Many researchers have attempted to integrate HDH with different cooling technologies to increase heat recovery in such systems and increase energy efficiency, while producing freshwater.
Several studies have investigated the benefits of the hybridization of VC-based cooling systems and HDH techniques for WP and conditioned air.Nada et al. [93] studied the performance of a hybrid desalination-cooling system employing the HDH and VC (HDH-VC) cycle.The evaporator surface works as a dehumidifier in the VC system to condensate the vapor, producing fresh and cooling water, as shown in Figure 8.
Elattar et al. [94] evaluated solar hybrid HDH-air conditioning (AC) systems performance by integrating heat storage and heating systems for stable operation.Several designs and operating parameters explained WP rate and recovery, CC, power consumption, COP, and economic indicators.The results showed that the decreases in outdoor conditions (temperature and humidity) decreased the additional heater's EC, opposite to the WP and recovery rates, CC, and the system power consumption.Compared with traditional systems in hot and humid regions, the results explained that the hybrid HDH-AC system has higher WP, CC, COP, and lower power consumption.Fouda et al. [95] theoretically investigated a solar hybrid HDH-AC system performance.The power, WP, CC, system COP, and water recovery were estimated as performance parameters.Additionally, Nada et al. [96] also studied HDH-VC system performance enhancement under dry and hot climatic conditions using an evaporative cooler, humidifier, and heat recovery unit at different arrangements.The results showed increased WP and power-saving by increasing the freshwater to recirculated air ratio and supplying air temperature.

Solar Humidification-Dehumidification/Cooling (SHDC) Systems
The Humidification-Dehumidification (HDH) desalination system is one type of thermal desalination method that works similarly to the natural rain cycles and is usually used as a small-scale desalination technology that can work with different salinity levels.The HDH system comprises a humidifier, in which the air is moistened by direct contact with hot saline water.In the dehumidifier, the air is cooled with indirect contact with the cool saline water before it enters the humidifier, leading to the condensation of the freshwater [91,92].Many researchers have attempted to integrate HDH with different cooling technologies to increase heat recovery in such systems and increase energy efficiency, while producing freshwater.
Several studies have investigated the benefits of the hybridization of VC-based cooling systems and HDH techniques for WP and conditioned air.Nada et al. [93] studied the performance of a hybrid desalination-cooling system employing the HDH and VC (HDH-VC) cycle.The evaporator surface works as a dehumidifier in the VC system to condensate the vapor, producing fresh and cooling water, as shown in Figure 8.
Elattar et al. [94] evaluated solar hybrid HDH-air conditioning (AC) systems performance by integrating heat storage and heating systems for stable operation.Several designs and operating parameters explained WP rate and recovery, CC, power consumption, COP, and economic indicators.The results showed that the decreases in outdoor conditions (temperature and humidity) decreased the additional heater's EC, opposite to the WP and recovery rates, CC, and the system power consumption.Compared with traditional systems in hot and humid regions, the results explained that the hybrid HDH-AC system has higher WP, CC, COP, and lower power consumption.Fouda et al. [95] theoretically investigated a solar hybrid HDH-AC system performance.The power, WP, CC, system COP, and water recovery were estimated as performance parameters.Additionally, Nada et al. [96] also studied HDH-VC system performance enhancement under dry and hot climatic conditions using an evaporative cooler, humidifier, and heat recovery unit at different arrangements.The results showed increased WP and power-saving by increasing the freshwater to recirculated air ratio and supplying air temperature.Furthermore, other studies have investigated the integration between the cooling effect of the ABR system with HDH desalination systems for WP and conditioned air.For instance, Chiranjeevi and Srinivas [97][98][99][100] investigated the performance of a hybrid desalination-cooling system employing the HDH and ABR (HDH-ABR) cycle.First, dehumidifiers were used to produce fresh water in two stages.Next, the ABR cooling effect produced more fresh water and supplied the location adapted by conditioned air.Solar energy was used in the heat process for each HDH-ABR unit.The system produced two effects (desalination and cooling).The results indicated that the higher effectiveness of the humidifier and exit evaporator temperature improves the system performance and provides a higher temperature of saltwater with lower evaporator temperature.
Picinardi [101] investigated a hybrid HDH-ABR system's water productivity and COP for desalination and cooling production with different water temperatures and mass flow rates.Almahmoud et al. [102] investigated a novel hybrid HDH-ejector refrigeration cycle (HDH-ERC) driven by solar energy.The results demonstrated that the ejector COP and entrainment ratio (ω) were 0.55 and 0.72, respectively.The entrainment ratio (ω) was the ratio between the mass flow rate coming from evaporator to the mass flow rate of fluid driving the ejector.The gained output ratio (GOR) and the WP for the HDH system were 2.76 and 20.58 L/h, respectively.Elbassoussi et al.
[103] developed a novel hybrid HDHadsorption desalination (AD) system to produce two effects (potable water and cooling) using low-grade heat sources.The system was driven by natural gas.At the same time, solar cells were used to run the blowers and pumps.The system WP was 21.75 kg per hour with a GOR of 2.50 (350% more than the standalone HDH).For the cooling effect, the CC and COP were 2.53 kW and 0.46, respectively.Significant savings of 30-40% in the cost of freshwater have also been achieved.Ali et al. [104] developed a novel hybrid solarpowered desalination system consisting of two ejectors (EJ), HDH, and AD systems, as shown in Figure 9.The system WP and GOR were 83.1 m 3 /tonSG per day and 2.76, respectively.The cost of WP was 1.49 $/m 3 .Furthermore, other studies have investigated the integration between the cooling effect of the ABR system with HDH desalination systems for WP and conditioned air.For instance, Chiranjeevi and Srinivas [97][98][99][100] investigated the performance of a hybrid desalinationcooling system employing the HDH and ABR (HDH-ABR) cycle.First, dehumidifiers were used to produce fresh water in two stages.Next, the ABR cooling effect produced more fresh water and supplied the location adapted by conditioned air.Solar energy was used in the heat process for each HDH-ABR unit.The system produced two effects (desalination and cooling).The results indicated that the higher effectiveness of the humidifier and exit evaporator temperature improves the system performance and provides a higher temperature of saltwater with lower evaporator temperature.
Picinardi [101] investigated a hybrid HDH-ABR system's water productivity and COP for desalination and cooling production with different water temperatures and mass flow rates.Almahmoud et al. [102] investigated a novel hybrid HDH-ejector refrigeration cycle (HDH-ERC) driven by solar energy.The results demonstrated that the ejector COP and entrainment ratio (ω) were 0.55 and 0.72, respectively.The entrainment ratio (ω) was the ratio between the mass flow rate coming from evaporator to the mass flow rate of fluid driving the ejector.The gained output ratio (GOR) and the WP for the HDH system were 2.76 and 20.58 L/h, respectively.Elbassoussi et al.
[103] developed a novel hybrid HDHadsorption desalination (AD) system to produce two effects (potable water and cooling) using low-grade heat sources.The system was driven by natural gas.At the same time, solar cells were used to run the blowers and pumps.The system WP was 21.75 kg per hour with a GOR of 2.50 (350% more than the standalone HDH).For the cooling effect, the CC and COP were 2.53 kW and 0.46, respectively.Significant savings of 30-40% in the cost of freshwater have also been achieved.Ali et al. [104] developed a novel hybrid solar-powered desalination system consisting of two ejectors (EJ), HDH, and AD systems, as shown in Figure 9.The system WP and GOR were 83.1 m 3 /ton SG per day and 2.76, respectively.The cost of WP was 1.49 $/m 3 .Al-Mahmoud et al. [105] theoretically combined and studied a novel hybrid HDH-ERC system.The results showed an increase in the COP and ω by increasing the temperatures of each generator and evaporator, and vice versa with the condenser temperature.By increasing the HDH minimum temperature by 15 °C, the GOR was increased by 20%.Ghiasirad et al. [106] developed a hybrid HDH-ABR system driven by a geothermal heat source, as illustrated in Figure 10, for generating power, desalination, cooling, and heating.The results found that the HDH-ABR can produce power, WP, cooling, and heating of 78.5 kW, 92 m 3 per day, 4991 kW, and 6251 kW, respectively.
Sadeghi et al. [107] analyzed a novel hybrid HDH-ERC system utilizing a zeotropic mixture working fluid.The HDH-ERC could produce power, CC, and total EEF of 52.2 kW and 120 kW, and 16.46%, respectively, slightly increasing distilled water.Habeebullah [108] investigated a hybrid dehumidification-heat pump (HP) experimentally to condensate the vapor from the atmospheric air in KSA.The hybrid system performance was examined for one year.The maximum WP was 2.23 m 3 /day in September, and the minimum WP was 0.618 m 3 /day in January.The average specific power rate was 0.42 kWh/liter of condensate water.The maximum water and electricity rate costs were 23 $/m 3 and 0.045 $/kWh.Nada et al. [109] experimentally investigated a hybrid HDH-AC system with a strips-finned helical coil dehumidifier type and cellulose paper in a bee-hive structure pad type for high performance.The HDH-AC system has a better performance for WP and cooling compared to other systems.The WP, CC, COP, and WP-specific costs were 17.42 kg/h, 3.9 kW, 4.35, and 0.7 ¢/kg of water, respectively.Al-Mahmoud et al. [105] theoretically combined and studied a novel hybrid HDH-ERC system.The results showed an increase in the COP and ω by increasing the temperatures of each generator and evaporator, and vice versa with the condenser temperature.By increasing the HDH minimum temperature by 15 • C, the GOR was increased by 20%.Ghiasirad et al. [106] developed a hybrid HDH-ABR system driven by a geothermal heat source, as illustrated in Figure 10, for generating power, desalination, cooling, and heating.The results found that the HDH-ABR can produce power, WP, cooling, and heating of 78.5 kW, 92 m 3 per day, 4991 kW, and 6251 kW, respectively.
Sadeghi et al. [107] analyzed a novel hybrid HDH-ERC system utilizing a zeotropic mixture working fluid.The HDH-ERC could produce power, CC, and total EEF of 52.2 kW and 120 kW, and 16.46%, respectively, slightly increasing distilled water.Habeebullah [108] investigated a hybrid dehumidification-heat pump (HP) experimentally to condensate the vapor from the atmospheric air in KSA.The hybrid system performance was examined for one year.The maximum WP was 2.23 m 3 /day in September, and the minimum WP was 0.618 m 3 /day in January.The average specific power rate was 0.42 kWh/liter of condensate water.The maximum water and electricity rate costs were 23 $/m 3 and 0.045 $/kWh.Nada et al. [109] experimentally investigated a hybrid HDH-AC system with a strips-finned helical coil dehumidifier type and cellulose paper in a bee-hive structure pad type for high performance.The HDH-AC system has a better performance for WP and cooling compared to other systems.The WP, CC, COP, and WP-specific costs were 17.42 kg/h, 3.9 kW, 4.35, and 0.7 ¢/kg of water, respectively.Figure 10.A schematic of the HDH-ABR system (adapted from [106]).

Xu et al.
[110] experimentally developed a solar hybrid HDH-HP system.The maximum WP of the hybrid system was 12.38 kg/kWh at 0.3 m 3 /h cooling seawater flow rate and 450 m 3 /h process air flow rate.Lawal et al. [111] experimentally expressed HDH-HP system performance, as depicted in Figure 11.The hybrid system provides heat exchange between the HDH and HP as a condenser-humidifier and evaporator-dehumidifier to yield fresh water and cooling.System performance and cost were studied at different operating parameters (like flow rates and temperatures).The maximum GOR, RR, COP, energy utilization factor, and WP values were 4.07, 4.86%, 4.85, 3.04, and 287.8 L/day, respectively, with a minimum specific electrical energy consumption of 160.16 kWh/m 3 of freshwater.In addition, the hybrid system gave a CC of 3.07 kW.10.68-20.39US$/m 3 of freshwater as the price of water production.

Xu et al.
[110] experimentally developed a solar hybrid HDH-HP system.The maximum WP of the hybrid system was 12.38 kg/kWh at 0.3 m 3 /h cooling seawater flow rate and 450 m 3 /h process air flow rate.Lawal et al. [111] experimentally expressed HDH-HP system performance, as depicted in Figure 11.The hybrid system provides heat exchange between the HDH and HP as a condenser-humidifier and evaporator-dehumidifier to yield fresh water and cooling.System performance and cost were studied at different operating parameters (like flow rates and temperatures).The maximum GOR, RR, COP, energy utilization factor, and WP values were 4.07, 4.86%, 4.85, 3.04, and 287.8 L/day, respectively, with a minimum specific electrical energy consumption of 160.16 kWh/m 3 of freshwater.In addition, the hybrid system gave a CC of 3.07 kW.10.68-20.39US$/m 3 of freshwater as the price of water production.

Solar Multi-Effect Distillation/Cooling (SMEDC) Systems
MED is one of the first thermal desalination techniques widely used in industry.The basic working principle is that the saline water is sprayed over a tube bundle to be heated at low operating pressure by the steam generated in the previous stage flowing inside these tubes, leading to the evaporation of water vapor, which is condensed in the last stages by cool saline water to form the freshwater [112].
Numerous researchers have investigated the integration of solar-driven MED units with various cooling technologies to make use of the excess thermal energy used to drive the MED units instead of wasting it to the surrounding environment, thus increasing system overall energy efficiency.Abdelhay et al. [113] numerically developed a hybrid solar desalination-cooling system employing a MED unit with an ABR system, as expressed in Figure 12.The solar power system (SPS) was a parabolic trough collector (PTC) unit, which uses thermal oil and ORC.In addition to a backup heater running on natural gas.ARS and MED units were driven by turbine-rejected steam.The first steam stream drove the ARS system, while the other steam line was adjusted before driving the MED system with the required heat.A hot well was used to collect MED, ARS, and condenser, and then the condensate was returned to the boiler.The hybrid system (SPS-ABR-MED) was developed to serve about a thousand residential homes.The operating parameters and design effects on the exergetic and plant energetics have been presented.The suitable area for PTC can be determined by selecting the capacities of the units (ABR, MED, and SPS) dependent on the flow rate of the steam condenser.Due to the heater, the highest percentage of total costs and operational expenditure was 54.83% and 87.68%, respectively.The hybrid system provides the lowest price for water and cooling production of 1.247 $/m 3 and 0.003 $/kW hr, respectively, with 23.95% exergetic efficiency compared to the single desalination and cooling systems or without solar system.

Solar Multi-Effect Distillation/Cooling (SMEDC) Systems
MED is one of the first thermal desalination techniques widely used in industry.The basic working principle is that the saline water is sprayed over a tube bundle to be heated at low operating pressure by the steam generated in the previous stage flowing inside these tubes, leading to the evaporation of water vapor, which is condensed in the last stages by cool saline water to form the freshwater [112].
Numerous researchers have investigated the integration of solar-driven MED units with various cooling technologies to make use of the excess thermal energy used to drive the MED units instead of wasting it to the surrounding environment, thus increasing system overall energy efficiency.Abdelhay et al. [113] numerically developed a hybrid solar desalination-cooling system employing a MED unit with an ABR system, as expressed in Figure 12.The solar power system (SPS) was a parabolic trough collector (PTC) unit, which uses thermal oil and ORC.In addition to a backup heater running on natural gas.ARS and MED units were driven by turbine-rejected steam.The first steam stream drove the ARS system, while the other steam line was adjusted before driving the MED system with the required heat.A hot well was used to collect MED, ARS, and condenser, and then the condensate was returned to the boiler.The hybrid system (SPS-ABR-MED) was developed to serve about a thousand residential homes.The operating parameters and design effects on the exergetic and plant energetics have been presented.The suitable area for PTC can be determined by selecting the capacities of the units (ABR, MED, and SPS) dependent on the flow rate of the steam condenser.Due to the heater, the highest percentage of total costs and operational expenditure was 54.83% and 87.68%, respectively.The hybrid system provides the lowest price for water and cooling production of 1.247 $/m 3 and 0.003 $/kW hr, respectively, with 23.95% exergetic efficiency compared to the single desalination and cooling systems or without solar system.

Figure 12.
The hybrid SPS-ABR-MED system (adapted from [113]).Kerme et al. [114] developed a theoretical analysis of the solar distillation-cooling system.The system includes a MED, ABR unit, and ORC with PTCs as thermal energy sources.The study includes many examinations, analyses, and effects on the proposed system, such as power configurations, turbine and pump inlet temperatures, total exergy loss, fuel depletion ratio, and improvement potential.The results showed that the performance increases and total exergy reduces by increasing the inlet temperature of the turbine; 49.3% and 9.6% of the input exergy destructed in the collector and desalination systems, respectively.The overall system improvement percentage was 64.8%.Mehrpooya et al. [115] studied an integrated system of desalination and refrigeration powered by solar energy.The system consists of a MED and ABR system with parabolic collectors and a steam turbine as a thermal energy source.The ABR and MED cycles produced a refrigeration power of 820.8 kW and potable water of 22.79 kg/s.The results also illustrated that the total cycle electrical energy efficiency and the total net thermal efficiency of the integrated system were 66.05%, and 80.70%, respectively.The integrated system had 5.738 years as an investment return period and 6.828 million US$ as a net annual profit per year.
Sahoo et al. [116] proposed hybrid solar-biomass power-based desalination-cooling and heating, as shown in Figure 13, to overcome renewable energy intermittence and reduce the greenhouse gas emissions and cost of power generation.The results showed decreased turbine output due to steam extraction from the turbine for ABR cooling and slightly declined COP.The net energy equivalent increased to 18.24% compared to a simple power plant with low CO2 emissions.The initial energy savings were brought to 15.3% for the hybrid system.Kerme et al. [114] developed a theoretical analysis of the solar distillation-cooling system.The system includes a MED, ABR unit, and ORC with PTCs as thermal energy sources.The study includes many examinations, analyses, and effects on the proposed system, such as power configurations, turbine and pump inlet temperatures, total exergy loss, fuel depletion ratio, and improvement potential.The results showed that the performance increases and total exergy reduces by increasing the inlet temperature of the turbine; 49.3% and 9.6% of the input exergy destructed in the collector and desalination systems, respectively.The overall system improvement percentage was 64.8%.Mehrpooya et al. [115] studied an integrated system of desalination and refrigeration powered by solar energy.The system consists of a MED and ABR system with parabolic collectors and a steam turbine as a thermal energy source.The ABR and MED cycles produced a refrigeration power of 820.8 kW and potable water of 22.79 kg/s.The results also illustrated that the total cycle electrical energy efficiency and the total net thermal efficiency of the integrated system were 66.05%, and 80.70%, respectively.The integrated system had 5.738 years as an investment return period and 6.828 million US$ as a net annual profit per year.
Sahoo et al. [116] proposed hybrid solar-biomass power-based desalination-cooling and heating, as shown in Figure 13, to overcome renewable energy intermittence and reduce the greenhouse gas emissions and cost of power generation.The results showed decreased turbine output due to steam extraction from the turbine for ABR cooling and slightly declined COP.The net energy equivalent increased to 18.24% compared to a simple power plant with low CO 2 emissions.The initial energy savings were brought to 15.3% for the hybrid system.Sahoo et al. [117] developed an innovative hybrid desalination-cooling system driven by solar-biomass to achieve higher energy efficiency and reduce greenhouse gas emissions.The desalination-cooling system consists of MED, HDH, and ABR cycles.System initial energy savings were achieved by 50.5%.The power output was increased to 78.12% compared to the simple power plant.Aly et al. [118] presented a novel integration of MED-ABR in Qatar to reduce cost and energy consumption.For the MED-ABR plant with a 25 m 3 /day capacity, the specific energy consumption (SEC) was 4.8 kWh/m 3 , lower than the MED-thermal vapor compression (TVC) plant of 60% (13 kWh/m 3 ).The results also illustrated that the MED-ABR pumping power and the feed seawater were 55% and 70%, respectively, lower than MED-TVC.The MED-ABR unit cost was 0.46 $/m 3 (22% lower than the MED-TVC).Son et al. [119] investigated a MED-AD hybrid system in KAUST, KSA, illustrated in Figure 14, to maximize energy input utilization in desalination.The WP and PR were 2-5 times enhanced to the MED.The developed MED-AD hybrid system demonstrated its applicability to industrial processes.Sahoo et al. [117] developed an innovative hybrid desalination-cooling system driven by solar-biomass to achieve higher energy efficiency and reduce greenhouse gas emissions.The desalination-cooling system consists of MED, HDH, and ABR cycles.System initial energy savings were achieved by 50.5%.The power output was increased to 78.12% compared to the simple power plant.Aly et al. [118] presented a novel integration of MED-ABR in Qatar to reduce cost and energy consumption.For the MED-ABR plant with a 25 m 3 /day capacity, the specific energy consumption (SEC) was 4.8 kWh/m 3 , lower than the MED-thermal vapor compression (TVC) plant of 60% (13 kWh/m 3 ).The results also illustrated that the MED-ABR pumping power and the feed seawater were 55% and 70%, respectively, lower than MED-TVC.The MED-ABR unit cost was 0.46 $/m 3 (22% lower than the MED-TVC).Son et al. [119] investigated a MED-AD hybrid system in KAUST, KSA, illustrated in Figure 14, to maximize energy input utilization in desalination.The WP and PR were 2-5 times enhanced to the MED.The developed MED-AD hybrid system demonstrated its applicability to industrial processes.Figure 14.Schematic of a hybrid MED-AD system (adapted from [119]).

Solar Single-Stage Flash/Cooling (SSSFC) Systems
The single and multi-stage flash (SSF and MSF) desalination technologies were developed to overcome some drawbacks of MED, such as the scale formation and corrosion on the tubes that increases the resistance to the heat transfer between steam and saline water, and thus reducing plant efficiency and lifetime.Consequently, MED operation is limited to driving temperatures in MED below 80 °C to overcome these problems [120,121].However, this low-driving temperature gives the MED technologies lower thermal power consumption and more suitable solar energy and waste heat at temperatures below 100 °C.The MSF technology is the dominant thermal desalination technology.It mainly depends on heating the feed saline water in one or more stages to above 100 °C, then letting it flows in consecutive stages at low pressures leading to flashing of water vapor that is condensed by the feed saline water to allow thermal energy recovery and increase system efficiency.However, some researchers have only investigated a singlestage flash system to make it more suitable for solar energy utilization with a similar operating principle [122,123].The saline feed water is heated, and then flashing occurs with the help of an expansion valve to separate the generated water vapor and the liquid brine.
Many studies have considered integrating solar-driven SSF desalination technology with different cooling technologies.Hogerwaard et al. [124] integrated a solar-driven gas turbine (SGT) with an ORC, an ABR system, and SSF desalination.The waste heat from the compressor and exhaust streams was exploited as a heat source for the ABR system generator, desalination process, and ORC boiler.The system indicated 0.27 and 0.284 exergetic and energetic efficiencies, respectively.Furthermore, the desalination process provided other commodities like cooling and hot water, and secondary power generation.
Velázquez-Limón et al. [125] investigated a solar-driven hybrid SSF/ABR system for a hotel, as illustrated in Figure 15.The SSF/ABR system comprised an open cycle absorption cooling system, in which the saline feed water was used as the cooling water for the ABR cycle.It passed through the SSF, where the water vapor was absorbed in the ABR absorber to be extracted after the ABR evaporator using an ejector.The results showed a 13.88% increase in ABR average COP, while the SSF desalination performance ratio was about 0.83.

Solar Single-Stage Flash/Cooling (SSSFC) Systems
The single and multi-stage flash (SSF and MSF) desalination technologies were developed to overcome some drawbacks of MED, such as the scale formation and corrosion on the tubes that increases the resistance to the heat transfer between steam and saline water, and thus reducing plant efficiency and lifetime.Consequently, MED operation is limited to driving temperatures in MED below 80 • C to overcome these problems [120,121].However, this low-driving temperature gives the MED technologies lower thermal power consumption and more suitable solar energy and waste heat at temperatures below 100 • C. The MSF technology is the dominant thermal desalination technology.It mainly depends on heating the feed saline water in one or more stages to above 100 • C, then letting it flows in consecutive stages at low pressures leading to flashing of water vapor that is condensed by the feed saline water to allow thermal energy recovery and increase system efficiency.However, some researchers have only investigated a single-stage flash system to make it more suitable for solar energy utilization with a similar operating principle [122,123].The saline feed water is heated, and then flashing occurs with the help of an expansion valve to separate the generated water vapor and the liquid brine.
Many studies have considered integrating solar-driven SSF desalination technology with different cooling technologies.Hogerwaard et al. [124] integrated a solar-driven gas turbine (SGT) with an ORC, an ABR system, and SSF desalination.The waste heat from the compressor and exhaust streams was exploited as a heat source for the ABR system generator, desalination process, and ORC boiler.The system indicated 0.27 and 0.284 exergetic and energetic efficiencies, respectively.Furthermore, the desalination process provided other commodities like cooling and hot water, and secondary power generation.
Velázquez-Limón et al. [125] investigated a solar-driven hybrid SSF/ABR system for a hotel, as illustrated in Figure 15.The SSF/ABR system comprised an open cycle absorption cooling system, in which the saline feed water was used as the cooling water for the ABR cycle.It passed through the SSF, where the water vapor was absorbed in the ABR absorber to be extracted after the ABR evaporator using an ejector.The results showed a 13.88% increase in ABR average COP, while the SSF desalination performance ratio was about 0.83.

Solar Membrane Distillation/Cooling (SMDC) Systems
MD is a thermal desalination technology in which a porous membrane is used to separate the water vapor, which is allowed to pass through the membrane, and the hot saline water, which is not allowed to pass.Then, the water vapor is condensed to form the produced freshwater [126,127].Many studies have investigated solar-powered MD systems integrated with various cooling technologies to increase overall system energy efficiency while supplying cooling and freshwater needs.Mohan et al. [128] investigated a new hybrid desalination-cooling-heating system powered by solar energy by different SC types in the United Arab Emirates weather conditions.The hybrid system included a solar energy unit, ABR, and MD modules, as shown in Figure 16.The system optimizes various design parameters (like water mass flow rate, slope, area of the collectors, and storage capacity).The lowest recovery period was achieved with 216 m 2 of evacuated tube SCs (6.75 years).The system saves 520,000$ throughout the project life.The system can produce a CC of the ABR of about 35 kW and freshwater 80 liters per day from the MD unit with heat recovery of 1.2 m 3 /h per year.
Byrne et al. [129] developed a theoretical model of a hybrid MD-HP for a desalinationcooling system to estimate producing the potable water depending on a refrigerator cooling load.The results showed that the hybrid MD-HP system offers more exciting perspectives than the RO plant for the same WP with a HP with the same cooling load.Ghaffour et al. [61] by solar energy, geothermal, or waste heat.The results showed a SEC of the MD-AD system of less than 1.5 kWhe/m 3 with 8 m 3 per day solar-driven AD cycle.Shafieian et al. [130] theoretically studied a novel MD-ABR system powered by wasted heat from exhaust fumes and heat from cooling submarine engines.The results showed that the optimum cooling power was 160 kW at diesel exhaust mass ratio and the refrigerant mass flow rate in the ranges of 0.8-0.95 and 0.27-0.34kg/s, respectively.Ayou et al. [131] nu-

Solar Membrane Distillation/Cooling (SMDC) Systems
MD is a thermal desalination technology in which a porous membrane is used to separate the water vapor, which is allowed to pass through the membrane, and the hot saline water, which is not allowed to pass.Then, the water vapor is condensed to form the produced freshwater [126,127].Many studies have investigated solar-powered MD systems integrated with various cooling technologies to increase overall system energy efficiency while supplying cooling and freshwater needs.Mohan et al. [128] investigated a new hybrid desalination-cooling-heating system powered by solar energy by different SC types in the United Arab Emirates weather conditions.The hybrid system included a solar energy unit, ABR, and MD modules, as shown in Figure 16.The system optimizes various design parameters (like water mass flow rate, slope, area of the collectors, and storage capacity).The lowest recovery period was achieved with 216 m 2 of evacuated tube SCs (6.75 years).The system saves 520,000$ throughout the project life.The system can produce a CC of the ABR of about 35 kW and freshwater 80 liters per day from the MD unit with heat recovery of 1.2 m 3 /h per year.

Comparison between Different Reported Hybrid Desalination/Cooling Systems
Table 2 summarizes the main research studies on hybrid solar desalination/cooling systems.The table shows available systems performance indicators, such as water production, cooling capacity, COP, and water cost.According to the review, the lowest cost of water production is 0.455 $/m 3 Aly et al. [122] for the hybrid MED-ABR system.Byrne et al. [129] developed a theoretical model of a hybrid MD-HP for a desalinationcooling system to estimate producing the potable water depending on a refrigerator cooling load.The results showed that the hybrid MD-HP system offers more exciting perspectives than the RO plant for the same WP with a HP with the same cooling load.Ghaffour et al. [61] by solar energy, geothermal, or waste heat.The results showed a SEC of the MD-AD system of less than 1.5 kWh e /m 3 with 8 m 3 per day solar-driven AD cycle.Shafieian et al. [130] theoretically studied a novel MD-ABR system powered by wasted heat from exhaust fumes and heat from cooling submarine engines.The results showed that the optimum cooling power was 160 kW at diesel exhaust mass ratio and the refrigerant mass flow rate in the ranges of 0.8-0.95 and 0.27-0.34kg/s, respectively.Ayou et al. [131] numerically studied the energy and exergy performance of a hybrid MD-ABR system powered by renewable energy (solar collector and biomass-fired) to provide WP, CC, and electricity.The system produced WP, CC, and electricity of 41.4 m 3 /day, 130 kW at 11 • C, and 6.4 kW, respectively.The results showed that the hybrid system could increase thermal energy conversion efficiency and decrease the effective cost of using solar energy.

Conclusions and Future Recommendations
This study reported on the state-of-the-art solar-driven hybrid desalination/cooling systems.Numerous studies have presented thermal and membrane desalination technologies, such as RO, MED, SSF, MD, and adsorption, absorption desalination, and HDH systems, and their integrations powered by solar energy were summarized.System performance indicators, such as water production rate, cooling capacity, COP, and water cost were presented to compare between these technologies.According to the review, the HDH-AC system had the highest COP of 4.35, at a specific water production cost of 0.7 ¢/kg.The lowest cost of water production was 0.455 $/m 3 for the hybrid MED-ABR system.The paper recommends the following points to be addressed in future research: The study of more adsorbent materials to enhance solar adsorption desalination system performance and increase the fresh water and desalination effects.
Experimentally study theoretical combinations, such as AD-RO, AD-HDH, ABR-RO, and AD-EJ to realize their performance.
Set up a pilot scale and cost study of these solar hybrid systems to attract investors.

Figure 2 .
Figure 2. Main desalination technologies reported in the literature.

Figure 2 .
Figure 2. Main desalination technologies reported in the literature.

Table 1 .
Summary of main research covering ADC system performance.

Table 1 .
Summary of main research covering ADC system performance.

Table 2 .
Summary of main research covering the performance of hybrid solar desalination/cooling systems.

Table 2 .
Summary of main research covering the performance of hybrid solar desalination/cooling systems.