Solar Cooling Research Articles

Modeling and simulation of absorption solar air conditioning in Morocco weather conditions

The air conditioning of most buildings is provided by compression refrigeration machines, which clearly goes against the objectives of saving energy and protecting the environment.In this work, we have established a modeling and simulation of absorption solar air conditioning with a simple effect, equipped with a distillation column to purify the ammonia vapor leaving the boiler, which has a negative effect on the performance of the machine, operating with the water-ammonia pair (Absorbent fluid - Refrigerant fluid). The numerical resolution carried out with the computer program made it possible to show the thermodynamic feasibility of this machine.The results of the modeling and numerical simulation of the distillation column absorption machine were compared with the results of the machine without distillation column. These results showed that the machine equipped with a distillation column is better adapted to the use of energy at low energy level (simple flat plate collectors, evacuated tube collectors, concentrating solar collectors, thermal effluents …).These efficient and quiet technologies, which involve fewer rotating machines, have a longer life than conventional refrigeration systems while having very low power consumption, even negligible for certain configurations.

Studies of solar air conditioning system based on triple effect refrigeration

A solar powered air-conditioning system designed for heating and cooling was put into operation and studies regarding the same triple effect refrigeration through solar thermal energy was carried out. Water, lithium bromide and other chemicals were used in the vapor absorption machine. Chiller having a capacity of 100kw i.e. 30TR was operated on the temperature of 210 0C obtained from solar field depending upon the solar radiations. This is the main part of the whole system because the heat produced by the solar field is used here for converting it into the chilling effect. The generator design of the machine allowed the use of hot water in the temperature range of 140-210 0C. The measured volumetric flow rate of hot water delivered by generator pump was ranging from 2 to 5.6m3/h.

Performance Analysis of Solar Absorption Cooling Systems in Iraq

The feasibleness of using an absorption solar cycle in Najaf, Iraq is evaluated in this study. In the system proposed, a 105,6kW Single Effect Absorption Chiller (SEAC) is powered by Evacuated Tube Collectors (ETC). TRNSYS (version 18) simulation is performed to select the various system parameters and optimize them to increase solar system efficiency, and this simulation develops a solar cooling model that simulates reality and is used effectively for cooling service buildings. The optimized solar air-conditioner for a building consists of a 35 m 2 collector area and number collector in series eight tilted at 32 o for Najaf, Iraq, from the horizontal and 1.5 m 3 HWST. It has been found that in effect, the solar absorption cycle reduces the annual electricity consumption where the solar fraction is high by 79% at Tehran and 77% at Najaf, Iraq. Also Utilizing solar energy can provide further benefits to the governments in the form of CO2 reduction, as the thermal energy generated by solar evacuated tube can reduce the energy used when the greatest percentage of CO2 reduction moreover 70.33 tons of CO2 for Tehran and 68.88 tons of CO2 in work period in each year.Â

Effect of Hot Water Setting Temperature on Performance of Solar Absorption-Subcooled Compression Hybrid Cooling Systems

The solar absorption-subcooled compression hybrid cooling system (SASCHCS) displays outstanding advantages in high-rise buildings. Since the performance coupling of collectors and absorption subsystems is stronger due to the absence of backup heat and the effect of generator setting temperature has not been realized adequately, it is highly important to study the relationship of SASCHCS operation and the set point temperature of hot water to prevent performance deterioration by inappropriate settings. Therefore, the paper mainly deals with the effect of collector and generator setting temperature. The investigation was based on the entire cooling period of a typical high-rise office building in subtropical Guangzhou. The off-design model of hybrid systems was built at first. Subsequently, the impact mechanism of setting temperature in two hot water cycles on facility operation was analyzed. It was found that the excessive rise of collector setting temperature deteriorated the energy saving, while the appropriate improvement of generator set point temperature was beneficial for the solar cooling. Besides, global optimization by the genetic algorithm displayed that 71.6 °C for the collector setting temperature with 64.5 °C for the generator was optimal for annual operation. The paper is helpful in enhancing the operation performance of SASCHCS.

Optimum operational strategies for a solar absorption cooling system in an isolated school of Mexico

In this work, we present the simulation study of a LiBr-H2O solar thermal absorption air conditioning system, installed in an isolated primary school in the community of Puertecitos, Mexico. The collection system consists of 110 m2 of evacuated tube solar collectors that produce the thermal energy needed to activate the chiller, while four cooling coils of 8.75 kW each cool the classrooms of the school with the chilled water produced. The characteristics of the system's equipment are used and a simulator is developed to determine the optimum operational strategies, given the conditions to which it will be subjected before the start-up of the plant. This is intended to ensure the comfort conditions of the students within the classrooms during the weekly class periods. The results show that the installed system is capable of satisfying the cooling needs of the school with the simulated strategies, but for a stable operation, periods of time must be dedicated for the recovery of energy inside the thermal storage tank. Some experiences are mentioned, both of the start-up and economic, related to an installation in an isolated community. The cost of the balance of plant was the highest with 36% of the total project, followed by the chiller and the solar field with 25 and 18%, respectively. The preliminary experimental results obtained during the implementation of the system are presented, where some of the operational strategies resulting from the simulation study can be confirmed.

Thermodynamic and Economic Contrast of an Ionic Solution Operated Solar Absorption Cooling System with LiBr+H2O Pair for a Business Building in India

The current study assesses the thermo-economic performance of a H2O[Formula: see text][EMIM][DMP] (1-ethyl-3-methylimidazolium dimethyl phosphate) working fluid-based absorption machine coupled with various solar collectors to cater the cooling load to business building at Gandhinagar city, India. H2O[Formula: see text][EMIM][DMP] could be an alternative to conventional LiBr[Formula: see text]H2O working fluid pair of absorption machines as it can operate without problem of crystallization which is perquisite for the continuous operation of the system. A mathematical model is developed to simulate the proposed system with 10[Formula: see text]kW cooling capacity at 5∘C. The sensitivity assessment is carried out to find the effect of various parameters including heat source temperature on the coefficient of performance (COP) and exergetic efficiency for each collector case. The optimum SCOP of parabolic trough collector (PTC)-based system is 11.43% higher compared to ETC-based system, whereas the ETC-based system is 25.10% economical than the PTC-based system. Furthermore, payback period for ETC-based system is only one month higher than FPC-based system, which altogether exhibits the superiority of ETC-coupled H2O[Formula: see text][EMIM][DMP] absorption refrigeration system over FPC-based system.

Review of latent thermal energy storage systems for solar air‐conditioning systems

Solar air-conditioning is an important approach to satisfy the high demand for cooling given the global energy situation. The application of phase-change materials (PCMs) in a thermal storage system is a way to address temporary power problems of solar air-conditioning systems. This paper reviews the selection, strengthening, and application of PCMs and containers in latent thermal storage system for solar air-conditioning systems. The optimization of PCM container geometry is summarized and analyzed. The hybrid enhancement methods for PCMs and containers, and the cost assessment of latent thermal storage system are discussed. The more effective heat transfer enhancement using PCMs was found to mainly involve micro-nano additives. Combinations of fins and nanoadditives, nanoparticles and metal foam are the main hybrid strengthening method. However, the thermal storage effect of hybrid strengthening is not necessarily better than single strengthening. At the same time, the latent thermal storage unit has less application in the field of solar air-conditioning systems, especially regarding heat recovery, because of its cost and thermal storage time. The integration of latent thermal storage units and solar air-conditioning components, economic analysis of improvement technology, and quantitative studies on hybrid improvement are potential research directions in the future.

Performance enhancement of a solar powered air conditioning system using passive techniques and SWCNT /R-407c nano refrigerant

This work presents a novel solar powered air-conditioning system that operates under UAE climate conditions. Distinct passive techniques and refrigerant-based nanofluids, termed as ‘‘Nano refrigerants’’ were investigated to enhance the system performance. Results suggest that the proposed design of using passive techniques such as: roofing reflective material, trees, double-glazed windows, and overhang, reduces the space cooling load by 31.5%. Nano refrigerants effect on the coefficient of performance (COP) resulted in improving COP by adding of 5 vol % single wall carbon nanotube (SWCNT) into R407c refrigerant at temperatures of 283–308 (K). The results indicate that the thermal conductivity of SWCNT/R-407c nano refrigerant increased by about 15.6% compared to the base refrigerant (R-407c) at 305 K. The usage of nano refrigerant reduces consumption of compressor work by 4%. Furthermore, SWCNT/R-407c nanorefrigerant shows the notable improvement of COP of at about 17.02% for thermal conductivity and at about 10.06% for specific heat, respectively compared to R-407c refrigerant. Finally, comparisons between the proposed design and the conventional system as well as with previous literature. Results demonstrate that the proposed system reduces the compressor work by 34% and the COP is increased by 4.59% compared to the conventional air-conditioning system.

Theoretical Investigation on Transient Heat Transfer through Building for PV-powered Solar Summer Air Conditioning

Theoretical Investigation on Transient Heat Transfer through Building for PV-powered Solar Summer Air Conditioning

Simulation of Lithium Bromide- Water (LiBr-H2O) Vapor Absorption System (VAS) powered by Solar Flat Plate Collector (SFPC)

Solar energy may probably prove to be best option for future in air conditioning system. With growing need of energy consumption, the solar air conditioning system stands as a useful alternative. The objective of this work is to simulate a single effect LiBr-H2O absorption system, coupled with solar flat plate collector (SFPC), to supply heat to the generator of Vapor Absorption System (VAS). Case studies have been taken from India, particularly New Delhi and Mumbai, which are, respectively, known for their hot and humid climate. The influence of different parameters like inlet generator temperature, heat supplied to the generator and cooling load have been investigated. The design day of 15th of April, May and June has been considered. The thermodynamic analyses have also been carried out. An outlet solar collector temperature between 68°C and 78°C was maintained for New Delhi, whereas between 67°C and 79°C for Mumbai. The maximum efficiency of SFPC was found to be 50 percent and 51 percent in case of New Delhi and Mumbai, respectively, on 15th April and 15th of May. A coefficient of performance of 0.857 was obtained at 4.1033 kWof heat supplied to the generator, at an inlet generator temperature of 68°C and cooling load of 3.5167 kW. It was observed that at constant ??????, any increase in supply heat, increases the flow rate of vapor and cooling load. Furthermore, the analysis for various stages of single effect LiBr-H2O (VAS) is presented including the design of the evaporator, absorber, condenser, heat exchanger and generator.

Solar powered air conditioner using BLDC motor

This paper present a load compressor fed Brushless DC motor for solar power air conditioner under variable air conditions. At current scenario, air conditioners are manufactured according to room size and space with available of objects present in the room.The output of the air conditioner cannot be alternatively changed. This problem is overcome by modify the fixed output of the air conditioner using BLDC motor. The BLDC motor performance is superior when compared to other motor. Solar power is used as the main source which is a renewable energy and readily available and also very useful for the future generation. This work deals with the output of the air conditioner can be alternatively changed according to the size of the room by varying the speed of Brushless DC motor.

Cost-effectiveness of Solar Cooling for Office and Hypermarket

Cost-effectiveness of Solar Cooling for Office and Hypermarket

Study on the characteristics of charging/discharging processes in three-phase energy storage coupling in solar air conditioning system

A new combination system of “three-phase energy storage” and solar absorption refrigeration has been developed in this paper. The operation process of LiBr-H2O three-phase energy storage system is described in detail. Thermodynamic analysis models of charging/discharging processes based on the absorption principle are established in order to understand the dynamic characteristics of three-phase energy storage and release processes. The dynamic simulations of charging/discharging processes are carried out by using MATLAB. The influences of operation parameters on the characteristic parameters of three-phase charging/discharging are analyzed, and the performance evaluation indexes of three-phase energy storage system are obtained. The simulation results showed that the lower initial concentration of LiBr-H2O solution, the smaller mass flow rate of LiBr-H2O sprayed on the heat exchanger in the energy storage tank and the higher heat conductance of the heat exchanger (KA) result in the higher energy storage efficiency and energy storage density. The smaller mass flow rates of LiBr-H2O and the cooling water can make the more stable discharging process with longer cooling time. The research results can provide theoretical guidance for further improving and optimizing the operation performance of three-phase energy storage system coupling in solar air conditioning.

Economic comparison of reference solar thermal systems for households in five European countries

This study presents a methodology developed in the framework of Task54 of the Solar Heating and Cooling (SHC) Program of the International Energy Agency (IEA) to calculate the heat cost per kWh final energy of solar thermal systems. Based on the concept of levelized cost of energy, three indicators are introduced depicting the heat cost of the solar part of the heating system only (LCoHsol,fin), the conventional part (LCoHconv,fin) or the overall solar assisted heating system (LCoHov,fin). The LCoHov,fin enables a comparison with other heating systems using different technologies. Applied to eleven residential systems in five European countries, the results show that the heat cost differs widely, depending on countries and system types. The solar heating system raises the heat cost of the overall solar assisted heating system compared to a reference system without solar assistance (subsidies are not considered) in most studied cases, but some solar domestic hot water systems and solar heating systems for multi-family houses are close to parity under current economic conditions and the assumptions considered in the paper. This work also highlights the importance of calculating the heat cost with a standardized methodology to enable a comparison between different systems.

Influence of window area and thermal transmittance in the consumption of electric energy in mid-western Brazil

The opening of windows allows the entrance of natural light, however, allows the transfer of thermal load from inside to outside the building and vice versa. Currently, despite the technological advances, it is still not possible in many buildings to integrate natural and artificial light. The design of a building, its geometry, size and properly orientation of the openings can result in great energy savings. Hence, defining the ideal window area for an ambient in which there is a balance between solar thermal load, air conditioning and natural and artificial lighting would lead to an environment whereby the energy consumption is optimized. This research presents the already consolidated methodology for calculation of ideal window area, which aims at the lower consumption of artificial lighting and air conditioning, considering a residential living environment. The analysis of energy consumption was carried out using the DesignBuilder software and the climate file of the city of Cuiabá - MT was considered, in order to quantify the impact of the climate on the supply of natural light and energy consumption. The methodology was divided into 3 stages, the first one consists of the determination of the base case and the constitution of the types of materials for analysis of the different thermal transmittance. In the second part of the method the simulations were performed and in the last stage the results were analysed. The simulations were performed considering the opening area at each 10% of the facade, for three geometries (1: 2, 1: 1 and 2: 1) considering three construction systems. The results showed that the openings in the south facade consume less and that this orientation allows larger openings, as well as the use of geometries with greater depth. Also, the thermal properties of the envelope influence the ideal window area, and the larger the thermal capacity the larger the openings that can be used. The present research showed the importance of considering the adequate areas and implementation of windows in the projects through the simulation. The potential of using sunlight for lighting has also been proven, by integrating natural and artificial light.

The performance of a desiccant wheel air conditioning system with high-temperature chilled water from natural cold source

A novel desiccant wheel air conditioning system that uses high-temperature chilled water from natural cold source (DWACS + HCW) is proposed. The proposed system integrates the renewable regeneration heat source and natural cold source, which are beneficial for energy saving. A model of the proposed system was developed, and the main components and the overall model were experimentally validated. The performance and the effects of the important parameters of the system under high humidity (32 °C, 80% RH), moderate humidity (32 °C, 60% RH) and low humidity (32 °C, 40% RH) conditions was studied numerically. The results showed that the system could achieve the supply air to the required temperature and humidity ratio in high, moderate and low humidity conditions, and compared to conventional solar desiccant wheel air conditioning systems (SDWACS), the energy performance is more efficient mainly due to high cooling and dehumidification capacity of surface air-cooler with high temperature chilled water.

Mathematical modeling of an integrated system for regeneration of solid desiccants using a solar parabolic dish concentrator

In this work, an integrated system is introduced to regenerate the desiccant materials in solar air conditioning systems. A solar parabolic dish collector and a helically baffled cylindrical cavity receiver were coupled to two series finned-tube heat exchangers, and a fixed bed filled with silica gel. A silicone oil as heat transfer fluid absorbs the solar energy and heats the air to regenerate the silica gels in the bed. The system was studied both experimentally and theoretically. A comprehensive mathematical model was developed for the entire system, and the proposed model was validated with experimental data. The regeneration rate of the desiccant materials and the average daily thermal regeneration efficiency of the system were obtained up to 0.4 kg water/h m2 and 30% respectively, which compared to the other solar systems, the present system has a good performance and is more efficient. Based on the weather conditions of the installed location of the system, the operational or even geometrical parameters of the system can be designed in such a way that for specified required cooling capacity, the system can provide the required energy for regeneration of desiccant materials. The system performance was studied during a sample day based on real solar irradiation intensity and ambient conditions, and the influence of the effective parameters was investigated on the regeneration rate of the silica gels.

Long-term building thermal performance of enclosed large-span swimming stadiums with retractable membrane ceilings

Building performance of enclosed large-span swimming stadiums is related to structural behavior, serviceability and energy demands. To ensure safety performance and enhance energy performance, a retractable membrane ceiling is proposed in relation to building complexity and multi-functions. Spatial- and time- dependent characteristics of large-span swimming stadiums suggest that the field measurement is a feasible way to assess building thermal performance. In this study, long-term experiments are carried out to measure temperature values. The statistical analysis to obtain stable performance is conducted with respect to several essential factors.Building thermal performance of large-span swimming stadiums mainly depends on solar irradiance, air conditioning and retractable membrane ceiling. Average temperatures for three selected periods in terms of individual and combined analysis demonstrate that using membrane ceiling can provide temperature enhancement effects for swimming stadiums. To propose suitable temperature ranges for engineering applications, an approach on the basis of statistical analysis is employed to determine confidence interval, which is a reliable index for evaluating long-term building thermal performance. A useful finding from confidence intervals of membrane ceilings and air conditioning (0.77–1.03 °C and 0.37–1.27 °C) is that passive and active ways are beneficial for indoor thermal environment. Therefore, one practical and effective suggestion is that the utilization of membrane ceilings to replace traditional heavy ceilings of swimming stadiums can achieve structural safety and energy saving.

Thermal Performance of Phase Change Material Based Heat Sink for Solar Photovoltaic Cooling

Solar photovoltaic panels can receive only eighty percent of total incident solar radiation. A small amount of incident energy is transformed into electrical energy based on the efficiency of the photovoltaic (PV) cell. The remaining energy leads to an increase in photovoltaic cell operating temperature which affects its life and power output. Cooling of PV panel is the best way to improve the efficiency either by passive or active cooling methods. PV cooling by Phase change materials (PCM) is the best effective technique. Paraffin wax is a non toxic material having high latent heat of fusion used for many thermal applications. In this study, paraffin wax is taken as phase change material in aluminum heat sink with fins. Using DSC, the melting point of paraffin wax is analysed. The flat plate heater is used instead of solar PV panel. Different wattages are used for the experiments. Different inclinations such as horizontal (00), vertical (900) and intermediate (450) were taken in to consideration. The melting starts at 50oC and complete melting occurs at a temperature around 60oC for the paraffin based heat sink. The heat sink surface temperatures, fin temperatures and PCM temperatures are measured. The transient temperature distribution of heat sink, PCM is analysed at different wattage inputs. The total thermal performance of this paraffin PCM based heat sink was analysed experimentally. This infers that the cooling of high temperature of PV panels can be done by using paraffin based PCM to increase the efficiency and life of the panels.

New Perspective on Performances and Limits of Solar Fresh Air Cooling in Different Climatic Conditions

The study carried out by simulation, concerns the thermal behavior of an office building’s solar fresh air cooling system, based on a LiBr-H2O absorption chiller in different climatic conditions. The coefficient of performance (COP) and the solar fraction were considered performance parameters and were analyzed with respect to the operating limits—the risk of crystallization and maintaining at least a minimum degassing zone. A new correlation between the required solar hot temperature and the cooling water temperature was established and then embedded in another new correlation between the COP and the cooling water temperature that was used in simulations during the whole cooling season corresponding to each location. It was found that—the solar hot water should be maintained in the range of (80–100) °C depending on the cooling water temperature, the COP of the solar LiBr-H2O absorption chiller with or without cold storage tank could reach (76.5–82.4)% depending on the location, and the solar fraction could reach (29.5–62.0)% without cold storage tank and could exceed 100% with cold storage tank, and the excess cooling power being available to cover other types of cooling loads—through the building envelope, from lighting, and from occupants, etc.