Similarly, Mohaisen and Ma developed and simulated asolar assisted liquid dehumidification air conditioning system using LiCl solution on Matlab Simulink platform. Their result has been validated with experimental results by Fumo and Goswami. The simulation results based on three consecutive sunny summer days in Sydney show daily COP of 0.5-0.55 by the proposed system and 73.4% of thermal energy required for thermal regeneration was provided by the solar collectors. Croffot and Harrisson experimentally evaluated the performance of a solar driven system installed in Canada. The system includes a low-flow parallel plate liquid desiccant air conditioner, and a 95m2 evacuated tube solar collector array. Results from five test days have shown an overall solar collector efficiency of 56%, solar fraction of 63% and a thermal COP of 0.47. The average total cooling was 12.3kW and average latent cooling was 13.2kW. Peng et al.studied a solar air pre-treatment collector/regenerator. Their simulation results showed that the storage capacity of proposed system could be improved by 50%, when the regeneration temperature was 60℃, and the inlet air specific humidity was 2.33kg/kg. In another study, Lychnos and Davies performed experimental and theoretical simulation for a solar powered liquid desiccant system using MgCl2. The theoretical model was developed and verified with the experimental results. Compared with conventional evaporative cooler,dutch buckets system the proposed system could further lower the average daily maximum temperature by 5.5-7.5oC. Alizadeh fields tested implementing polymer plate heat exchanger into LDAC in Australia summer weather condition. Lithium chloride with 43% was used in the experiments and a scavenger air regenerator concentrates the dilute solution from the dehumidifier using hot water from flat plate solar. Alizadeh experimentally analyzed the effects of various air flow rate and desiccant flow rate on the system performance.

The experimentally obtained data was compared with a developed model. The comparison showed a good agreement between the experiments and model predictions. The results showed that the proposed system could provide cooling capacity up to 20kW with dehumidification efficiency up to 72%. Qi et al.simulated yearly system performance of solar assisted LDAC for commercial application in five cities . In this study, the effects of various solar collector areas and monthly solar radiations, ambient air conditions on the electricity consumption saving and monthly average COP were theoretically analyzed.Results shows that for buildings located in humid areas with low sensible-total heat ratio, the electricity energy reduction of the system was high and about 450MWh in Houston and Singapore and payback was approximately 7 years. For building in dry climate, although the total cooling load was low, up to 45% of electricity of AC can be saved because of significant improve in chiller COP during more than 70% of operation time and the payback was around 22 years. However, for the buildings with mild outdoor humidity, such as those in Beijing and Los Angeles the electricity energy saved only around 100MWh and the cost payback period was more than 30 years, and the application of LDAC was not that suitable. Li and Zhang investigated a solar energy driven hollow fiber membrane-based desalination system. The system consists of a membrane-based humidifier, a fin-and-tube type dehumidifier and a solar heating unit, which consists of a U-tube evacuated solar collector and a heat storage tank. The hollow fiber membrane-based humidifier is similar to a shell-and-tube heat mass exchanger. Through numerical modelling and experimental tests, they found that the COP of the system can reach about 0.75 and electric COP of 36.13 is achievable, which means electrical energy consumption is much less due to solar energy reclamation. Results show that solar accounts for 92.0% of the electric energy consumption by the entire system.

Sensible heat losses account for most of the energy losses from the system. Chen et al. proposes solar assisted liquid desiccant dehumidifier and regenerative indirect evaporative cooling system for fresh air treatment. The hot and humid fresh air is firstly dehumidified by LDD and then sensibly cooled by RIEC. The thermal energy captured by solar collectors is used for desiccant solution regeneration. In this study, they have looked into the influences of solar collector area and inlet air conditions and optimizing the extraction air ratio of RIEC. The energy saving ratio is quantitatively evaluated with respect to a conventional A/C system. Results shows that the energy saving ratio ranges from 22.4% to 53.2% under various inlet air conditions. This characteristic of liquid desiccant dehumidification system that the dilute liquid desiccant can be regenerated by low grade heat makes it attractive option for integrating with thermal sources. Many studies have been done on integration of liquid desiccant system with solar, vapor compression, heat pump, and CHPs. But only two research has been done integrating liquid desiccant with SOFCs. The typical SOFC system exhaust temperature matches very well with the required temperature for liquid dehumidification. Elmer has looked into design, development and proof of concept combined generation of power, cooling and heating based on SOFC and Liquid desiccant air conditioning technology for building application. A 1.5kW SOFC integrated with liquid desiccant has been proposed for providing heating, cooling and electricity to low carbon buildings. Elmer et al.used empirical SOFC and liquid desiccant component data for an energetic, economic and environmental analysis. They have used a simple 0D model in Engineering Equation Solver platform for regeneration, dehumidifier and fuel cell. The model is based on dimensionless vapor pressure and temperature difference ratio designed for packed bed liquid desiccant. The results show the moisture removal of the supply rate is mainly controlled by desiccant temperature and cooling water temperature in constant flow rates. 

The air inlet condition has a large effect on cooling output performance and the unit performs better in a hot and humid climate. By increasing the regeneration heat source temperature more water vapor vaporizes from the weak solution. The model they used have limitation such as not including the effectiveness of heat and mass exchanger effectiveness, geometry of the contactor, and desiccant carry over. For desiccant air conditioning system Elmer developed an Integrated Desiccant air Conditioning System . This system combines regenerator, dehumidifier and evaporative inter-cooler into a single membrane-based heat and mass exchanger to reduce the size, complexity and leakage. The IDCS operates with a KCOOH desiccant working fluid. The liquid desiccant is sprays through nozzle from the top where regenerator is located and flows downward due to gravity. In this design instead of preheating desiccant before regeneration and precooling it before dehumidification, thermal energy is supplied to the regenerator through airstream and an evaporative inter-cooler is designed. This is because all desiccant flow is contained within one complete Heat and Mass Exchanger the solution cannot be extracted for prior heating and cooling. This feature is weakness of this design as precooling and preheating of liquid desiccant increases the performance of the system.Their design was supposed to significantly reduces the number of heat exchangers, pipes, and ducting in liquid desiccant air conditioning systems. The main issue with this integrated system was imbalance between moisture removal rate in the dehumidifier and moisture addition rate in the regenerator. This mass imbalance is primarily due to the available surface area for heat and mass exchange in the regenerator being too small and an insufficient vapor pressure differential between the air and desiccant solution. In order to regenerate the desiccant solution back to its original condition following the dehumidification process,dutch buckets the regenerator needs to operate for extended time periods. Across the variables investigated there is a greater instantaneous moisture removal rate in the dehumidifier than moisture addition rate in the regenerator. Desiccant solution leakage/carry-over on the dehumidifier side of the HMX has been noticed during the experiment as well. In response to the highlighted shortcomings of the novel IDCS Theo Elmer developed a Separated liquid Desiccant air Conditioning System for trigeneration system integration. SDCS consist of three separate cores including dehumidifier, regenerator, and an evaporative cooler. The SDCS uses a semi-permeable, microporousmembrane-based cross flow contactor, operating with KCOOH desiccant solution. The solution channel consists of polyethylene sheet, with fiber membrane attached on either side to allow diffusion of water but prevent the liquid desiccant entering the air side. In evaporative cooler, air and water come into contact in a cross flow HMX. Before liquid desiccant entering the dehumidifier, a plate heat exchanger is used to precool the desiccant to increase its potential. After dehumidifying the air, the weak solution enters the dehumidifier tank.

Desiccant is preheated before entering the dehumidifier. The strong desiccant flows to regenerator tank after regeneration. In this design, because the entire SDCS is placed within the environmental, the water for the evaporative cooler and desiccant for dehumidifier are at the ambient temperature which has an impact on moisture absorption capacity of the desiccant and the sensible cooling. This design causes little to no sensible cooling achievable. Also, the evaporative cooler only provides around 80–150W of cooling over their study range. As a result, the evaporative cooling provided is not enough to produce a sufficient solution temperature decrease and to provide sensible cooling to the supply air in the dehumidifier. Elmer et al. experimental results on SDCS show effective instantaneous balancing of the dehumidifier and regenerator across a range of environmental and operational values, operation of the dehumidifier is dictated, to some degree by the available SOFC thermal exhaust, COP values in the range of 0.4–0.66 are achievable with a low-grade thermal input typical of an SOFC CHP system and potential for non-synchronous operation in a tri-generation system context, bringing about improvements to peak cooling output and total system efficiency. Elmer et al. used empirical SOFC and liquid desiccant component data for an energetic, economic and environmental analysis. The 1.5kW BlueGen SOFC systems is electrically connected to the grid to import or export as required. The waste heat recovery circuit is connected to a home’s 300L hot water cylinder which also includes an auxiliary gas boiler. Experimental results shows that the electrical efficiency of SOFC system increases from 14% at 200W to maximum of 60% at 1500W and then decreases to 56% as 2000W capacity. Thermal output from fuel cells varies linearly from 320Wth at 200We to 540Wth at 1500W. The calculated water heat recovery temperature for 2l/min flow based varies between 47 C at 100We to 52℃ at 2000We. Be Power Tech, Inc. developed BeCool, a natural gas-powered air-conditioning system that produced electricity as by product on the site. The innovative idea shifts some grid powered electricity for cooling demand to natural gas which would substantially reduce peak summer power demand and help to reduce the need for costly peaking power plants. Their studies showed that their 5ton BeCool unit eliminates ~ 10kW of peak electricity demand, generates 43MWh/yr electricity and saves ~ 10MWh/yr compared to conventional air conditioning. They build a prototype and the test results showed that the electrical power efficiency was 45% to 60%. The primary potential energy saving is 4.1 Quads, and the technology has the potential to reduce 222 million metric tons of CO2. Their analysis for California climate 7 and 14 shows 53% CO2 reduction in a 50% electrical efficiency for fuel cell and 90% combined heat and power efficient fuel cell system is used. BeCool uses exhaust heat from the fuel cell and heat from the burner to increase the concentration of LiCl to 42% mass fraction in the regeneration process. Be Power Tech designed and built an experimental prototype BeCool system integrating a 2.5kW SOFC system , a boost natural gas burner, and a custom-made liquid desiccant air conditioner designed to produce from 2.5-tons to 4-tons of cooling. The system was tested under multiple outdoor air conditions. Their study showed that, in all cases the heat supplied by the fuel cell was not sufficient to provide the heat required for the air conditioning process, since these isolated tests could not rely on storage from daily continuous regeneration. For this reason, the supplemental natural gas burner was used to supply the heat required [80]. Integrated fuel cell dehumidification systems have never previously been studied for data center application. The only two studies that have looked at integration of SOFC with dehumidification systems were focused on building applications of the technology.