Solar Absorption Refrigeration System Research Articles

Multi-Objective Optimization Research on the Integration of Renewable Energy HVAC Systems Based on TRNSYS

Well-designed passive buildings can drastically reduce building energy consumption, and optimal design of air conditioning systems is the key to achieving low operating energy consumption in near-zero energy buildings. TRNSYS was used to build the simulation model for a near-zero-energy building and its air conditioning system in Beijing. The Taguchi method was used to sort the design parameters that affect system performance according to the degree of influence and find the best combination of design parameters to optimize the system, which increased the solar fraction of the system by 4.6% and reduced the annual operating energy consumption by 7.32%. For the optimized system, a multi-objective optimization function of the life cycle costs and carbon emissions was established. By comparing the energy consumption, life cycle costs, and carbon emissions of the air conditioning system under different system configurations, optimal configuration solutions under different design target weights were obtained. It was found that using a ground source heat pump system + solar collector system had better energy-savings benefits, but the operating costs were slightly higher. The application of absorption refrigeration can reduce the system operating costs but will increase the initial investment. The best economic benefits were achieved using the ground source heat pump system + solar collector system for heating in winter and the ground source heat pump system for cooling in summer, and the best environmental benefits were obtaining using the ground source heat pump system + solar collector system for heating in winter and the ground source heat pump system + solar absorption refrigeration system in summer, which provides a reference for the optimization design and research of air conditioning systems in near-zero energy buildings.

Energy–exergy analysis for performance improvement of Brayton–Rankine combined cycle system by utilizing a solar absorption refrigeration cycle (case study: Kahnuj Combined Cycle Power Plant)

AbstractGas–steam combined cycle power plants are the most efficient electricity‐generation units based on fossil fuels. However, these power plants are prone to efficiency decrease in hot climates as high ambient temperatures adversely influence the gas turbine's output. The present study investigated the effect of incorporating a solar absorption refrigeration (SAR) system into an actual combined cycle power plant for the first time. First, the energy and exergy analyses were performed using THERMOFLOW software. Then, the influence of the ambient temperature (10°C–52.5°C) on the power plant's performance and its components was investigated. The SAR system was then used to cool the compressor's input air and improve the power generation capacity by employing TRNSYS software. The results showed that the power plant reached its maximum efficiency at an ambient temperature of 26.6°C. However, its overall efficiency and net power generation were dropped with a further increase in the ambient temperature. Employing the SAR system for each gas turbine in the power plant on a sunny day until 2 p.m. would decrease the compressor's input air temperature. For example, for the refrigeration capacities of 450, 700, and 1000 tons for each gas turbine, the temperature was reduced by nearly 3°C, 5°C, and 7°C, respectively. Under the same condition, power generation capacity improved by 12.5, 24, and 32.5 MW, and the overall efficiency rose by 0.6%, 1.4%, and 2%. Such an increase in power and efficiency occurred during peak demand, which was significant.

Enhancement of Condenser Performance in Vapor Absorption Refrigeration Systems Operating in Arid Climatic Zones—Selection of Best Option

Generators and condensers are the two vital equipment items that determine the output of vapor absorption refrigeration systems. Arid weather conditions produce a significant reduction in the performance of the vapor absorption refrigeration cycle due to low condenser heat dissipation despite high generator temperatures. Although numerous studies on condenser cooling methods in vapor compression systems have been reported in the literature, solar-operated vapor absorption systems have not been studied. Limitations in generator temperatures of solar-operated vapor absorption systems necessitate a focused study in this area. This study makes the selection of the best choice for condenser cooling from among four different condenser cooling methods which have an impact on the performance of the vapor absorption refrigeration system for effective cooling using solar energy. A solar vapor absorption refrigeration system working with low-grade heat using a compound parabolic collector is considered in this study. Analysis of a vapor absorption refrigeration system for cooling in arid weather conditions is carried out using different condenser cooling methods with Engineering Equation Solver. Initially, the model used in the study is compared with a similar study reported in the literature. Techniques considered are air, water, evaporative, and hybrid cooling techniques. The performance of the vapor absorption cooling system was analyzed using experimental values of a solar compound parabolic collector obtained from real-time measurements for simulating the model. Results show that water cooling can provide suitable condenser cooling and improve the coefficient of performance of the solar vapor absorption refrigeration system using the solar collector. The water-cooled condenser has 1.9%, 3.3%, and 2.1% higher COP when compared to air-cooled condensers for spring, summer, and autumn seasons respectively, whereas the water-cooled condenser cooling recorded 6%, 14%, and 8% higher COP relative to the evaporative cooling method. Cost comparison showed maximum cost for water-cooled condensers and minimum cost for hybrid-cooled condensers. The effect of each cooling method on the environment is discussed.

Solar Powered Air-Conditioning Using Absorption Refrigeration Technique

The present work includes design, construction and operates of a prototype solar absorption refrigeration system, using methanol as a refrigerant to avoid any refrigerant that cause global warming and greenhouse effect. Flat plate collector was used because it’s easy, ninexpensive and efficient. Many test runs (more than 50) were carried out on the system from May to October, 2013; the main results were taken between the period of July 15, 2013 to August 15, 2013 to find the maximum C.O.P, cooling, temperature and pressure of the system. The system demonstrates a maximum generator temperature of 93.5 oC, on July 18, 2013 at 2:30 pm, and the average mean generator temperature Tgavr was 74.7 °C, for this period. The maximum pressure Pg obtained was 2.25 bar on July 19, 2013 at 2:00 pm. The current system shows cooling capacity of 0.15 ton with coefficient of performance of 0.48, and minimum evaporator temperature obtained was 14.2oC. A comparison of the present with previous works, showed that most of the previous work used ammonia as the main refrigerant, and even that used methanol it was as aqua methanol, or to be part of pair refrigerant, while the present work use the methanol as the main and the only refrigerant in the system. The results and the factors that provided by the current work, give a good understanding for using the methanol as a refrigerant with the solar absorption system. And the system can work in continuous operation cycle. This work gave fundamental understanding for designing solar refrigeration system, by using the results of present study to design air-conditioning unit, with one ton capacity, using the solar energy, and the methanol as a refrigerant.

Performance of Solar Hybrid Cooling Operated by Solar Compound Parabolic Collectors under Weather Conditions in Riyadh, Kingdom of Saudi Arabia

The scientific aim of this work is to encourage energy conservation. This article offers a fresh perspective on renewable energy in the air conditioning sector, the country’s economic growth, and environment-friendly techniques to overcome global warming challenges. In this research, a solar vapor absorption refrigeration (SVAR) system was combined with a conventional vapor compression refrigeration (VCR) system to analyze their combined performance, employing a compound parabolic collector (CPC). The goal was to assess the performance of a solar hybrid cooling system using this non-tracking solar collector. CPC was validated for heat output with 2.9% uncertainty by utilizing an engineering equation solver (EES). Other system components were also validated with EES and then extended to a larger-capacity solar hybrid cooling system. The results of this research indicate that CPC is effective in providing the required heat to SVAR throughout the year without any tracking, and the integration of SVAR in series with the VCR condenser produces 83% higher COP than the system that integrates VCR with the condenser of the SVAR system for Riyadh. The configuration results in high values of exergy COP and an efficiency of 88% and 84%, respectively, increases the cooling capacity of the VCR by 68%, and decreases the carbon emission by 166.4%.

Optimization and Analysis of an Integrated Liquefaction Process for Hydrogen and Natural Gas Utilizing Mixed Refrigerant Pre-Cooling

Liquefying hydrogen is an efficient way to store and transport hydrogen. However, the hydrogen liquefaction process is energy intensive. Therefore, an integrated liquefaction process of hydrogen and natural gas utilizing the mixed refrigerant cycle and the hydrogen Claude cycle is proposed. The process not only couples a steam methane reforming process to produce hydrogen and a carbon dioxide refrigeration cycle to assist in pre-cooling, but also employs a solar energy absorption refrigeration system to enhance energy efficiency. The proposed process is simulated and optimized using HYSYS and the particle swarm optimization algorithm, and energy, exergy, and economic analyses are performed. The energy analysis shows that the specific energy consumption of the proposed process is 5.2201 kWh/kg, a reduction of 10.67% compared to the base case. The exergy loss and exergy efficiency are 64,904 kW and 62.21%, which are 13.63% and 6.63% lower than the base case, respectively. The economic analysis shows that the total annualized cost of the process is USD 28.6 million per year. The proposed integrated liquefaction process not only realizes the high efficiency of energy utilization but also follows the development trend of integrated energy systems.

Analytical modelling of food storage cooling with solar ammonia-water absorption system, powered by parabolic trough collectors. Method

The study presents a new analytical model capable to reveal the thermal behaviour of all the components of the solar ammonia-water absorption system, powered by parabolic trough collectors, serving different types of food storages: refrigeration chamber, refrigerated food storage, freezing chamber and frozen food storage. The heat inputs, that determine the total cooling load, for each food storage spaces consist of: heat gains through walls, heat gains through ventilation (fresh air), heat that must be dissipated from the stored products (technological cooling load required to cool down the products) and heat gains through operation. The influence of the number of solar parabolic trough collectors and of the storage tank size on different parameters of the refrigeration plant are investigated under low and high storage temperatures.•Food cooling with solar absorption refrigeration system.•Hourly based variation of NH3-H2O solar absorption system performances.•Long term simulation of solar absorption cooling for refrigeration and cooling.

Mathematical modeling and performance analysis of a solar assisted vapour absorption refrigeration system

Climate change is the hottest topic today on earth. Traditional HVAC’s harm the environment and stand out to be a major contributor to global warming. One of the many techniques to mitigate the current climate crisis is by utilizing the abundantly available solar radiation. Solar evacuated tube collectors are used to absorb solar radiation. This solar power is used to provide solar cooling technologies. Unlike the conventional HVAC’s thermally driven absorption cooling is a boon in today’s era. In the following research work, the study aims to provide numerical modeling of a solar assisted air-conditioning unit through the first law of thermodynamics using mass balancing equations for the province of Delhi in July. This research work’s aim is to build and evaluate a Li-Br absorption cooler with a capacity of 1 KW. This paper aims to provide characteristic design features of components and measures the efficiency of the system at operating conditions. PCM based thermal energy storage tank is adopted which helps to supply cold air even at no sunlight hours. As a result of this research study, such solar assisted air conditioners turn out to be a chosen solution for sustainability.

Simulation of an improved solar absorption refrigeration system with phase change materials

Aiming at the problems of low solar energy utilization rate, poor intermittent, low stability and poor energy saving effect in traditional solar absorption refrigeration system, a lithium bromide-water absorption refrigeration system driven by solar in Tai’an was taken as the research object. An improved solar absorption refrigeration system with phase change was presented. In typical day and whole refrigeration period, the traditional solar absorption refrigeration system with and without phase change were simulated by TRNSYS transient simulation software. Their collector efficiency, unit cooling capacity and COP were comparatively analyzed. The results showed that the collector efficiency of the improved solar absorption refrigeration system with phase change was 4.2% higher than that of the traditional solar absorption refrigeration system without phase change. The unit cooling capacity was 2.8% lower than that of the traditional system, which store the excess cooling capacity with the help of PCMs. The average COP of traditional absorption system and improved solar absorption refrigeration system were 0.737 and 0.679, respectively. This manuscript provides a theoretical basis for the development of solar phase change heat storage absorption refrigeration system.

Influence of disturbances in the operating conditions on the refrigeration performance of a regenerative solar absorption refrigeration system with a biomass assisted combustion device

To reduce the fluctuation of the heat source water temperature and ambient temperature caused by variations in solar radiation, a solar absorption refrigeration system with a supplementary biomass combustion device for the office area of a factory was designed. A numerical model of the solar energy absorption refrigeration system based on the Aspen Plus software was developed. In particular, the effects of the heat source water temperature, condenser temperature, evaporation temperature, and dilute solution flow rate on the cooling capacity, coefficient of performance, unit equipment duty, and generator temperature during actual operation were investigated. The heat load of each piece of equipment in the unit were found to increase correspondingly with the increase of the heat source temperature when the evaporating temperature and condensing temperature are constant. The coefficient of performance of the unit decreased as the condensing temperature increased keeping the temperature of the heat source constant. The results demonstrated that the flow rate of the dilute solution has effects on the occurrence temperature, cooling capacity, and the unit performance coefficient.

Analysis of Energy Consumption of the Lyophilizer System Using Solar Absorption Refrigeration

To design a lyophilizer plant in Guangzhou, the author of this paper used a solar energy absorption refrigeration system and a waste heat of solar absorption refrigeration system. Using Trnsys software, the simulation results show that the solar assurance rate of 74.96% on July 28th can save coal quantity of about 236.8 kg, a solar assurance rate of 53.48% in July can save coal quantity of about 4790.9 kg, and an annual solar assurance rate of 39.06% can save about 40657.1 kg, and each have good environmental benefits.

Research on Solar Adsorption Refrigeration System

In order to achieve solar adsorption refrigeration, this paper studies the surface water source solar absorption refrigeration system combined with surface water source cooling and solar absorbent refrigeration techniques: the solar radiation intensity is adjusted by changing the distance between iodine tungsten lamps and solar cold tubes. The results show that the entire cycle has a range of solar radiation intensity of 400 to 1000 W/m2, and the indoor ambient temperature ranges from 19 to 25∘C, and the humidity is maintained around 40%. The highest temperature in the solar cold tube adsorption bed is 12∘C; during the adsorption process, the temperature drops to about 20∘C; the solar cold tube is 160 kJ in one cycle of the solar cold tube, and the cooling coefficient is about 0.15. Conclusion: solar cold tubes can effectively utilize solar refrigeration, it is a refrigeration method for environmentally friendly, no greenhouse effects and ozone destruction, which has potential application value and has energy saving and environmental protection.

Energy and exergy analysis of parallel flow double effect H2O-[mmim][DMP] absorption refrigeration system for solar powered district cooling

Solar thermal energy-driven double effect absorption refrigeration system (DE-ARS) for district cooling in smart cities is an efficient, and sustainable alternative for centralized air conditioning and concurrently harnesses low-grade solar energy. This work investigates ionic liquid based H2O-[mmim][DMP] mixture as an alternative working fluid to overcome the drawback of H2O–LiBr driven DE-ARS. The thermodynamic properties of H2O-[mmim][DMP] mixture is evaluated using the excess Gibbs free energy model. Performance modeling and simulation of DE-ARS is based on both energy and exergy analysis by applying the first and second laws of thermodynamic. The performance, and solution circulation ratio of parallel flow DE-ARS is assessed and optimized under various temperatures and solution distribution ratios. In comparison to the conventional H2O–LiBr, the proposed H2O-[mmim][DMP] working fluid achieves 5.22% and 4.95% improvement in COP and ECOP, respectively at Th/Te/Ta/Tc of 140/5/30/30°C . An optimization of generator temperature to achieve maximum COP and ECOP is performed for a wide range of evaporation temperature from 5 to 20°C and Ta/Tc from 30 to 40°C. An optimization of H2O-[mmim][DMP] mixture driven DE-ARS reveals the uppermost COPmax and ECOPmax of 1.81 and 0.69 for Te of 20°C and TaTc=30°C.

A New Computational Tool for the Development of Advanced Exergy Analysis and LCA on Single Effect LiBr–H2O Solar Absorption Refrigeration System

A single effect LiBr–H2O absorption refrigeration system coupled with a solar collector and a storage tank was studied to develop an assessment tool using the built-in App Designer in MATLAB®. The model is developed using balances of mass, energy, and species conservation in the components of the absorption cooling system, taking into account the effect of external streams through temperature and pressure drop. The whole system, coupled with the solar energy harvesting arrangement, is modeled for 24 h of operation with changes on an hourly basis based on ambient temperature, cooling system load demand, and hourly solar irradiation, which is measured and recorded by national weather institutes sources. Test through simulations and validation procedures are carried out with acknowledged scientific articles. These show 2.65% of maximum relative error on the energy analysis with respect to cited authors. The environmental conditions used in the study were evaluated in Barranquilla, Colombia, with datasets of the Institute of Hydrology, Meteorology and Environmental Studies (IDEAM), considering multiannual average hourly basis solar irradiation. This allowed the authors to obtain the behavior of the surface temperature of the water in the tank, COP, and exergy efficiency of the system. The simulations also stated the generator as the biggest source of irreversibility with around 45.53% of total exergy destruction in the inner cycle without considering the solar array, in which case the solar array would present the most exergy destruction.

Experimental Investigation of Solar Absorption Refrigeration System.(Dept.M)

In this paper, an investigation of aqua-ammonia solar absorption refrigeration system for domestic use is presented. The refrigeration system investigated here is a conventional aqua-ammonia absorption refrigeration system powered by solar heater. The solar heater used is a stationary, hyperbolic sprial solar concentrator equipped with a glass tube for convection loss suppression. A generator temperature as high as 140°C is reached. The lowest temperature reached in evaporator is 2°C, with an additional external heating Source. The various parameters affected the cycle performance and cooling ratio, such as, the generator temperature, evaporator temperature, collector performance and condenser temperature are presented. For fixed initial conditions, higher generator temperature and lower condenser temperature increases the coefficient of performance and improves the operation of the system.

Study on characteristics of the cavitation bubble dynamics of lithium bromide aqueous solution with ultrasonic interaction

Solar absorption refrigeration (SAR) system occupies large building energy consumption, due to its low generation efficiency. Depending on the mechanism of enhanced disturbance and convection, this paper proposes the application of ultrasound heat-transfer enhancement technology in the boiling heat-transfer of LiBr/H2O solution in the generator to enhance system performance. At present, there are few theoretical and experimental studies about the ultrasound on heat-transfer enhancement in the salt solution, especially in the field of multi-frequency ultrasound (MFU) bubble dynamics. The motion of a cavitation bubble has significant impact on the disturbance and convection in the solution. Thus, the mathematical models of cavitation bubble dynamics (CBD) are constructed to evaluate the solution cavitation characteristics, the CBD on boiling heat-transfer in the generator is investigated, and the effect of the number of ultrasonic vibrators (UVs) on the cavitation bubble radius (CBR) is investigated to explore the cavitation characteristics of MFU. The results indicate that: the low-frequency ultrasound on the heat-transfer in vacuum generator is more obviously effect, due to enhance solution mixing around the heating surface; the maximum CBR could be increased by increasing the number of UVs, while the maximum CBR is increased by no more than 1% at the number of UVs of 24–25 and the total sound intensity of 1 W/cm2, respectively; the solution in vacuum generator could produce transient-cavitation with MFU. This study, not only reaffirms the benefit of using the MFU for generator of SAR system, but also provides some rules of the cavitation characteristics of MFU.

An integrated absorption cooling technology with thermoelectric generator powered by solar energy

A novel integrated solar absorption refrigeration system with a thermoelectric generator and thermoelectric cooler is presented. The proposed system is of a 20-kW single-stage lithium bromide absorption cycle driven by solar evacuated tube collectors or by the heat rejected by the thermoelectric cooler module. The governing equations of the thermodynamic model are solved, and the results are validated. It was found that the coefficient of performance of the system approaches a constant value at a generator temperature of 100 °C. The best performance of the system was found in the case of placing the thermoelectric cooler between the generator and the condenser. The coefficient of performance and the overall thermal efficiency were found to be 1.12 and 73.4%, respectively. Furthermore, a 20% rise in the generator temperature would increase the power produced by thermoelectric generator modules by 60%. An increase of 20% in the thermoelectric generator modules would result in a reduction of 11.5% in its efficiency, while doubling the temperature difference would increase the generated power by a factor of three.

Review on performance enhancement of solar absorption refrigeration system using various designs and phase change materials

Recent trend of increasing global warming throughout the world rising at very alarming rate. In leu of that, several efforts have been made by various researchers, among this solar refrigeration is one of the areas which required to be explored further. Conventional refrigerator consumes electricity which is mostly produced by power plant and most of the power plants in India running on coal, oil etc., which leads to rise of greenhouse gas production, that directly contribute to global warming. Several efforts have been made by researchers to enhance the performance of solar absorption refrigeration system. It has been found that the utilization of waste heat either from the marine ship engine or from the economizer can be used to run the ammonia water absorption refrigeration system. Few studies have been done on using phase change material to enhance the latent heat of fluid by various method which can be further used at night to supply it to generator of refrigeration system. The performance of vapour absorption refrigeration system has been enhanced significantly by using nanoparticles. Simulations studies gives interpretation of various design changes effect on the performance of solar refrigeration system and that can be used for further experimentation works. The effect of various design and operating parameters on the COP of refrigeration system have been reported by various researchers.

A novel vacuum wastewater treatment plant integrated with a solar absorption system

In this investigation, a novel use of the solar absorption refrigeration systems was introduced by using it to enhance the operation of vacuum wastewater treatment plant. Wastewater treatment systems require a source of heat for evaporation, a cooling section for condensation and a mean of evacuation to facilitate evaporation. The solar absorption system can take over the first two tasks. Among the commercially available vacuum evaporators, one was selected and modified by replacing the conventional heat pump with the solar absorption system. Two validated mathematical models available in the literature, one for solar absorption subsystem and one for vacuum evaporation subsystem, were integrated together to perform the analysis. The impacts of solar absorption subsystem parameters along with vacuum evaporator subsystem parameters on the overall performance were investigated using the developed program. System performance was evaluated in terms of evaporation rate and condensate rate production. It was found that the degree of superheat had the greatest impact on the rate of evaporation. At low levels of supply temperature to the vacuum chamber, using only heat provided by the absorption system, the evaporation rate exceeded 60 kg/h. If the hot water was further heated by passing through the solar collector storage tank, the evaporation rate exceeded 200 kg/h.

Energy-saving evaluation of a solar integrated vacuum freeze-dryer and building air conditioning system

Vacuum freeze-dryer has been widely used in many fields such as food, medicine, and beverage. In the actual operation process, the freeze-dryer and factory buildings need to consume a lot of cold energy. In order to reduce energy consumption, this paper presents a freeze-dryer system using solar energy absorption refrigeration in conjunction with buildings. Through the solar absorption refrigeration system, the cooling capacity is supplied to the freeze-dryer and the building at the same time, so that the cold can be cascaded utilization. The simulation of the system by TRNSYS software shows that the system can greatly reduce the consumption of conventional energy, and it is a new energy-saving measure of vacuum freeze-dryer and building air conditioning.