Energy consumption by cooling and desalination systems is huge and increasing with growing demand. The integration of two or more energy systems to form a hybrid system and work on a single energy source is one of the strategies for better energy utilization. This paper introduces a novel hybrid cooling-desalination system. The cooling unit is based on the ejector refrigeration cycle (ERC) and combined with water-heated humidification dehumidification (HDH) desalination cycle to make the hybrid system. A validated model of the hybrid system is developed and evaluated using the Engineering Equation Solver (EES) software. The basic ERC is analyzed with R134a as the refrigerant at different operating temperatures. The results show that the increase in the generator temperature improved the entrainment ratio (w) and the coefficient of performance (COP). The COP and entrainment ratio also increases with the increase in evaporator temperature. The increase in the condenser temperature resulted in a decrease in COP and entrainment ratio. The gain output ratio (GOR) of the HDH system is improved by 20%. This is due to the increase in the minimum temperature of the HDH system by 15 °C as a result of the hybrid configuration. This led to a 17% enhancement on the overall energy utilization factor.

The operation of solar driven air conditioning systems is limited to the availability of solar radiation. Consequently, to achieve extended cooling period, energy storage is necessary. This study presents performance evaluation and charging and discharging characteristics of an absorption energy storage coupled with solar driven double-effect water-lithium bromide (H2O-LiBr) absorption system through thermodynamic modeling and simulation. The absorption energy storage stores the solar heat in the form of chemical energy during the day and discharges later for cooling application. The integrated system achieved effective cooling for about fourteen hours on daily basis. The results indicate an average coefficient of performance (COP) of 1.35 for the integrated absorption chiller-storage unit and exergy efficiency of 25%. Furthermore, the overall COP of the integrated solar cooling system is 0.99 and the overall exergy efficiency is 6.8%, while the energy storage density for typical climatic conditions of Dhahran, Saudi Arabia is found to be 444.3 MJ/m3. The energy storage density obtained from the integrated solar driven H2O-LiBr double-effect absorption system is found to be higher by 13–54% compared to other integrated systems based on single-effect configuration.

This article presents simulation results of a solar cooling system that consists of a parallel-flow double-effect water-lithium bromide absorption chiller and parabolic trough solar collector. Parametric study of the cooling system is carried out considering a reference double-effect absorption chiller from Broad Company with nominal cooling capacity of 1163 kW. The aim for the analysis is to properly size the solar collector field and study the interaction of different operating conditions and parameters on the operation and performance of the system. Based on the operational constrains of the reference chiller, such as the minimum chilled water temperature and the cooling power, a solar collector field of 1350 m2 (1.16 m2/kW) is obtained from the range of 800–1800 m2. The reference system is then optimized where the exergy efficiency (second law efficiency) is maximized considering the flow rates of the external working fluid and solution distribution ratio of the parallel-flow double-effect absorption chiller as the decision variables. The system optimization is performed considering the risk of solution crystallization at various locations within the chiller. The optimum parameters together with other operating conditions are normalized per unit chiller nominal cooling capacity so that these values can be applied to other similar system configurations with different chiller nominal capacities. The reference system is simulated at optimum condition using a typical day climate data of Kuala Lumpur, Malaysia. The system achieved cooling effect in the range of 798–1223 kW under solar radiation levels of 600–944 W/m2. The procedure presented in this paper can be applied in sizing the solar collector field and evaluating the performance of similar systems under various climatic conditions having minimum solar radiation around 500 W/m2.

Solar desalination systems often have limited operating hours and their operation is significantly affected by the variation of solar radiation intensity. A model of a humidification–dehumidification (HDH) desalination system integrated with evacuated tube solar collectors and thermal storage is developed and validated against available data in the literature. Operating parameters such as the maximum temperature of water heater and the mass flow rate ratio of the HDH component are optimized. The thermal storage unit consists of separate hot and cold-water storage tanks, which allow control of the water temperature leaving the storage unit. Furthermore, performance of the system for six different geographical locations in Saudi Arabia, namely Riyadh, Jeddah, Dhahran, Qassim, Sharurah, and Tabuk, is studied. The system is evaluated for four different scenarios as follows: (i) 24-h operation; (ii) with the ideal flow rate; (iii) with the average flow rate; and (iv) with the maximum flow rate. The effect of flow rate on the number of operating hours and the rate of freshwater production is also evaluated. The maximum freshwater production is 9.346 L/h and the minimum is 3.01 L/h. For a service life of 20 years, the cost of freshwater produced varies from 0.021 to 0.034 $/L considering interest rate of 2%.

The use of solar thermal collectors is one of the promising options for heating and/or cooling due to the green nature (pollution free) and abundance of the solar energy in many parts of the world. Improvement of thermal performance of solar collectors is important for better energy conversion. In this regard, many studies reported in literature tried to modify geometry of the collectors. On the other hand, nanofluids as heat transfer fluids could be a promising option for the efficiency enhancement of solar collectors. In this study, heating performance of an evacuated tube solar collector system initially operated with water is considered for improvement using nanofluid. The collector (about 20 kW heating capacity) is a part of an absorption cooling system. The aim of the present study is to analyze the effect of Single Walled Carbon Nanotube–water nanofluid on the collector performance. Thermal efficiency improvement is assessed based on comparative analyses between collector working with ordinary water and that with nanofluid. The results indicate that up to 56.7% and 66% of efficiencies are observed when the collector is operated with water and 0.2 vol% nanofluid, respectively. Therefore, nanofluids are promising to enhance the efficiencies of solar collectors.

Air-conditioning systems consume large amount of energy and generate considerable amount of condensate when operated in hot and humid climates. This study considers utilizing the generated condensate to pre-cool the air entering evaporators to improve systems performance. Experimental and analytical investigations are carried out by using an air-conditioning system of 4.75 kW (16207 BTU/h) cooling capacity incorporated with an air pre-cooler and a condensate tank that acts as a thermal storage. During the pre-cooling-on period, the air inlet temperature of the evaporator is decreased by 5.7°C (10.3°F) and the compressor power consumption is reduced by 5.1% because of the decrease in discharge pressure. The coefficient of performance increases by 30.7% and second-law efficiency by 24.2%. The air pre-cooling is practical for 4–5 hours daily during the daytime if a 450–1000 kg of condensate cold thermal storage is employed. The deviation is 6.7% between the analytical and experimental results.

The conventional vapor compression air conditioning systems remove moisture from the air by cooling to a very low temperature. This dehumidified air is then reheated to an appropriate supply temperature for occupants comfort. These two processes of excessive cooling and reheating of process air remarkably increase the air conditioning load. To avoid the excessive waste of energy an alternative way to achieve desired moisture reduction is the use of liquid desiccant dehumidification system in which a desiccant material absorbs moisture from the humid air. Thermal energy is used to regenerate the desiccant material and cycle continues. A good desiccant should have better moisture absorption capability and lower temperature of regeneration. Different types of new desiccant materials with high dehumidification performance have been proposed in past few years. These materials have the potential to improve the performance of liquid desiccant cooling systems because of lower heat input required for regeneration. In this article, liquid desiccant cooling systems have been discussed from variety of aspects including the need of liquid desiccant technology as an alternative way of cooling, working of liquid desiccant cycle, as well as developments of this technology. The research indicated that the technology of liquid desiccant cooling has a great potential of energy saving and providing human thermal comfort conditions in hot and humid climatic conditions with the utilization of alternative energy resources.

A humidification-dehumidification (HDH) desalination system integrated with solar evacuated tubes was optimized. Then, the optimized system was assessed for the operation in different geographical locations, and the rate of freshwater production and cost per liter were determined in each location. The system design proposed in this paper uses a heat pipe design evacuated tube collector, which performs significantly better based on cost. An HDH desalination system with a closed-air/open-water loop, connected to the collector, was evaluated to determine the optimum operating parameters and the system performance during daytime (from 8 am to 3 pm), as well as the average day of each month for an entire year. The impact of the effectiveness of the humidifier and the dehumidifier, as well as, the number of collectors, were also studied. The analyses were performed for Dhahran, Jeddah, Riyadh, Sharurah, Qassim, and Tabuk to determine the effects of varying the geographical location. Sharurah has the highest calculated productivity of freshwater and Dhahran has the lowest at 19,445 and 16,430 L, respectively. To have a comprehensive study of the system proposed, a cost analysis was also performed to determine the feasibility of the system and the cost of water production. Results show that the price varied from $0.032 to $0.038 per liter for the locations evaluated.

Air conditioning systems contribute to the largest share of energy consumption in building sector. On the other hand, the systems produce reasonable amount of condensate, especially when operating in humid climates. The aim of this study is to minimize the energy consumption and improve the performance of air conditioning systems utilizing condensate. Experimental investigation has been carried out to improve the performance of an air-cooled vapor compression system by pre-cooling air entering the condenser using condensate. A pre-cooler is incorporated on a 1.5 ton-cooling capacity split-type air conditioning system to lower the air temperature entering the condenser sensibly. Performances of the air conditioning system with and without air pre-cooling are compared and reported in this paper. The results show that pre-cooling the air by about 4 °C before entering the condenser lowers the compressor discharge pressure. The decrease in the discharge pressure resulted in the decrease in compressor power consumption by 6.1% and the cooling effect of the system is enhanced. The combined effect of the increase in the cooling effect and decrease in compressor power resulted in an increase in the coefficient of performance (COP) and second law efficiency of the system by about 21.4 and 20.5%, respectively.

Energy storage plays a vital role in shifting cooling energy load from period of peak demand to that of low demand. This paper reports performance data of an ice-storage unit in solar absorption cooling system for cooling an office space. The cooling system consists of ammonia-water absorption chiller, evacuated tube solar collectors and ice-storage. Experiments were carried out on two consecutive days in each of the month of March and October in Dhahran, Saudi Arabia. The ice-storage unit was charged on the first day and the cool energy discharged on the other day. The results showed average coefficient of performance (COP) of the chiller during charging as 0.43 and 0.47 for the months of March and October, respectively. The results also indicate that the ice-storage can provide a backup time of about 5–6 h, which is sufficient to cool the given space during the early hours of chiller warm-up.

The use of solar–assisted absorption chiller for space cooling is limited to availability of solar radiation; hence, energy storage is very crucial in order to achieve extended hours of cooling operation. In this study, operational and performance characteristics of a solar driven lithium bromide-water absorption chiller integrated with absorption energy storage of the same working fluid are investigated. The integrated system simultaneously provides cooling and charging of the absorption energy storage during the hours of solar radiation. Simulation of the integrated system is carried out based on first law of thermodynamics. Effects of weather variables such as solar radiation and the influence of coupling absorption energy storage with an absorption chiller are investigated. The results indicate that cooling effect of the chiller varies with the variation of solar radiation, with maximum value of 20 kW for a collector area (Ac) of 96 m2 on a typical day in July, Dhahran, Saudi Arabia. The cooling COP of the integrated system during cooling/charging and discharging is found to be 0.69 and the energy storage density of the absorption energy storage is 119.6 kWh/m3. Furthermore, the operational characteristics of the proposed system showed that the internal operating parameters of the integrated chiller-absorption energy system such as solution temperatures and pressures are within reasonable levels. Hence, this indicates the possibility of integrating the absorption energy storage with absorption chiller.

This study aims to investigate water extraction process from a solar cooling system using a vapor absorption chiller under variable fresh air ratios. The system consists of an evacuated tube solar collector, lithium bromide absorption chiller and a fan coil unit (FCU). A parametric study is carried out to investigate the effects of flow rate of the fluid in the collector, solar insolation, fresh air volume ratio, temperature and humidity on the system performance and rate of water production. The operating conditions for the best performance are identified in this work. The results showed maximum collector efficiency of 0.66 at an optimum flow rate of the collector fluid of 0.3 kg/s at Ac = 28 m2, Tf = 45 °C, I = 800 W/m2 and R = 50%. For the same conditions, useful energy to the generator was found to be 14.8 kW and water production rate was 8 L/h. Using the climate data of a typical day of August for Dhahran, Saudi Arabia, the findings indicated that the chiller COP and water production rate, respectively, reached maximum (0.73 and 6.6 L/h) at noon when the incident solar flux is peak (935 W/m2) for 45% fresh air volume ratio.

Solar thermal energy is one of the viable options for space cooling in the quest of greener environment and energy efficiency. The major challenge in actualizing the use of solar energy to drive cooling systems such as absorption chillers is its intermittent nature, thereby not able to cover significantly the period of cooling demand in most situations. In order to achieve continuous cooling energy supply from solar driven absorption chillers, the present study considered two alternative storage units in the form of chilled water and ice, integrated to the main chiller installed in Dhahran, Saudi Arabia. The system is designed to allow different operational modes in accordance with the cooling demands. The system is tested experimentally where the storage units are used alternatively and the results are presented. A mean chiller COP for cooling the space and chilling the water was found to be 0.8 whereas it was 1.3 for only making ice. Maximum COP (0.8) was found at Tgen = 120 °C at an average condenser and evaporator temperatures of 34.5 °C and −2.2 °C, respectively.

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.

Comparative study on flat photovoltaic (PV) string and symmetric compound parabolic concentrator (CPC) photovoltaic system has been presented in this paper. Two flat PV strings and two unglazed PV-CPC systems are considered. The cells of each of the flat PV and PV-CPC strings are subjected to cooling to reduce temperature. The performance of the two configurations with and without cooling is evaluated numerically and experimentally. The numerical models for the flat PV string and the PV-CPC systems are solved using Engineering Equation Solver (EES) software and the concentration ratio of the CPC system is considered as 2.3X. Absorbed energy is calculated with and without cooling for the PV-CPC and flat PV systems. The absorbed energy is used to solve the energy balance equations on different nodes of the system from which the cell temperature was determined. The results showed that the maximum power output of the flat PV string with cooling was approximately 21. W which gives about 49% more than the power obtained without cooling. The maximum power output of the PV-CPC system with cooling was approximately 34. W which is about twice of the power obtained in the absence of cooling. It was found that the power output of the PV-CPC system is higher than that of the flat PV string with and without cooling by 39% and 23% respectively. Comparison of the numerical results with experimental data showed good agreement for the two configurations. The maximum percentage differences between the numerical and experimental power output for the flat PV with and without cooling are 5% and 7%, respectively. While those of the PV-CPC system with and without cooling are 9% and 11%, respectively.

Water is one of the basic necessities in life and its preservation is essential, particularly in hot and humid regions. Air conditioning systems operating in these regions usually produce a considerable amount of condensate. In this paper, analytical and experimental investigations in determining the condensate from a vapor compression air conditioning system as an additional water source are presented. A split type air conditioning system (1.5. tons) located in Dhahran, Saudi Arabia, where the dry bulb temperatures and relative humidity range from 25 to 50. °C and from 15 to 90%, respectively, is used for the study during summer months. Based on the hourly data, the monthly condensate yields during June, July, August and September are 1.26, 1.29, 2.50 and 2.33. kg/ton per CDD, respectively. The condensate is dominantly affected by the air humidity and temperature. The variation pattern of the condensate extraction is similar to that of the relative humidity. The collected condensate can be used as an additional water source. The chemical analysis of the condensate indicates that the water can be used for human consumption. The analytical model predictions of the condensate correlate well with the experimental data with a correlation factor of more than 90%. © 2014 Elsevier B.V.

Cooling load is the energy needed to be removed from a space by a cooling system to provide the desired level of comfort. Large space load requires high energy from the cooling system. A new technique of reducing the cooling load using condensate to pre-cool air stream entering the evaporator of a vapor compression air-conditioning system is presented in this paper. In a cooling process, water vapor condensation normally occurs when the evaporator coil surface temperature becomes lower than the dew point temperature of the humid air entering the evaporator. The cooling process results in appreciable amount of condensate in climatic conditions with high relative humidity and temperature such as those in Dhahran, Saudi Arabia. The rate of condensate yield is calculated using actual climate data of three typical summer days of Dhahran area for the months of June, July and August. These months are the most humid and hottest during the year. Each month is represented by a typical day determined by the average of the three hottest and humid days during the same months of the past three years. It is found that the condensate obtained during night time is more than the day time because of the high relative humidity at night. The results indicate that the cooling load can be reduced up to 10 % when the air entering the evaporator is pre-cooled by 4 °C using the condensate. In addition, the daily condensate yields from the evaporator coil in June, July and August are 1.27, 0.92 and 1.31 kg/kW-CDD, respectively. Copyright © 2013 by ASME.