Solar Absorption Chiller Research Articles

A Review of single-effect solar absorption chillers and its perspective on Lebanese case

Solar cooling systems, specifically solar absorption cooling systems, are becoming an attractive subject since they are great alternatives to the conventional cooling systems which lead to high electrical consumption. In addition, this system can provide cooling without greenhouse gas emissions. Hence, many combinations of different components might be adopted to apply the solar absorption cooling system. This paper will discuss the absorption chiller working cycle, the absorption chiller working fluids, the solar collectors to be combined with solar cooling systems and the single-effect absorption chiller. Furthermore, the variation of the coefficient of performance, the solar fraction and the economic study will be discussed. The goal of this review is to present previous studies and analyze their results; highlight the environmental, energetic, and economic viability of such systems and tackle future challenges regarding solar absorption cooling system and discuss the application of this system on new climates and more specifically on Lebanon.

Optimization of an integrated combined cooling, heat, and power system with solar and wind contribution for buildings located in tropical areas

Combined cooling, heat, and power systems present higher energy efficiency and consequent financial benefits due to the reduced consumption of energy resources. In addition, there is the possibility of combining renewable and non-renewable energy resources. This study develops an economic optimization to identify the optimal configuration and operation for an energy supply system. The optimal configuration is a subset of the available equipment, which includes solar collectors, fuel lines, electric grid, photovoltaic panels, wind turbines, gas boilers, engine-generator sets, recovery boilers, and absorption and compression chillers. The optimization method consists of four steps: pre-selection of the set of equipment to be evaluated, generation of all possible equipment combinations, optimization of the operation of each configuration based on a linear programming model, and exhaustive search to identify the lowest Net Present Value (objective function). A sensitivity analysis verified the optimal system in different β values, where β is a multiplier of the fuel (βfuel) and electricity (βele) tariffs. By systematically varying the β value, it is possible to identify the optimal system for different fuel and electricity tariffs. For example, for an optimization with βele = 1 and βfuel = 1.2, this assumes that the electricity tariff has not changed and the fuel tariff has increased by 20%. The optimal system (optimization with βfuel = 1 and βele = 1) meets the electricity and chilled water demands with electricity from the electric grid. A gas boiler meets the hot water demand. Due to the dependence on the electric grid, the optimizations with different β values result in systems with different configurations. For βele > 1.03 the solution is based on photovoltaic panels, when βele > 1.2 the solution is based on wind turbines and photovoltaic panels, and for βele > 1.33 the solution includes all equipment initially available. For βfuel < 0.48 the solution is constituted by an engine-generator set, recovery boiler, absorption and compression chiller, and a gas boiler. The optimal system obtained in the optimization with βele = 1 and βfuel = 1 showed a high risk of investment in the resilience analysis, indicating that other systems can be installed, bringing satisfactory results in the long term.

Application of Business Model Canvas for Solar Thermal Air Conditioners

Growing populations, burgeoning economies, and technology-driven lifestyles demand an increasing supply of energy. The existing energy supply pattern primarily depends on fossil fuels that have initiated climate change–provoking myriad problems. Integration of renewable energy sources in the existing energy supply system is a complex and challenging task keeping in view the depleting fossil fuels and prevailing environmental challenges. The existing cold storage farms are working on traditional compressors and the HVAC system, causing more use of electricity. Similarly, existing data centers and supermarkets are also using conventional refrigerants. These systems also use hazardous environmental refrigerants, which make these systems more dangerous. In the summer season, comfort cooling and refrigeration requirements rise to peak in hot climate areas forcing utilities to supply more electrical energy to meet the demand. Therefore, a solar thermal cooling system employing a solar absorption chiller operated through a hot water stream generated by a solar evacuated glass tube collector with CO2 as a refrigerant is simulated in the TRNSYS® simulation environment. The results are generated for the hot climate of Multan, Pakistan, and the average obtained temperatures of the three rooms, cold storage, office, and kitchen room, were 18.43, 26.25, and 29.83°C, respectively. However, every startup or new idea needs a proper business model before entering into the market. This article offers a complete insight and a future perspective for the reader to develop a precise business model for the commercialization of his or her project. A business model is designed for solar thermal air conditioners for domestic, cold storage, and data centers applications in the world, after reviewing and interviewing manufacturers and customer segment in air conditioning fields. Data were collected through semi-structured one-to-one interviews from a convenient sample of 10 national and international respondents, and their views were thematically analyzed. The implementation of a business model using a case for the Pakistani market is presented. A business model for a solar cooling system utilizing abundant CO2 as a refrigerant is presented in this article. This business model is equally suitable for designing a business model for any renewable energy product in the world.

Feasibility study on the solar absorption cooling system for a residential complex in the Australian subtropical region

The negative impacts of the increasing number of air conditioning systems in Australia include excessive strain on grids and associated blackouts, higher electricity costs and associated carbon emission issues. The installation of sustainable cooling technologies such as solar absorption cooling systems provides a promising alternative. However, the feasibility of the system for the Australian subtropical climate has not systematically studied. The paper aims to investigate the feasibility of implementing solar absorption cooling technology in student residential building in Australia's subtropical climate region. The feasibility study allows the user to determine if the solar cooling system is technically, economically and environmentally sustainable in the long term. Through the simulation, the key performance parameters such as power consumption data and component performance details were determined. The simulation results showed that the solar absorption chiller can provide comfort in the building by maintaining room temperature within 20–24 °C. The system's performance optimisation studies were conducted, and it was found that the collector area 20 m2 paired with a storage ratio of 0.02 m3/m2 had provided a high solar fraction (SF) of 0.91. The economic analysis is also carried out to determine the annual savings in energy cost, carbon emission reduction, and the payback period.

Shell-and-Tube Latent Heat Thermal Energy Storage Design Methodology with Material Selection, Storage Performance Evaluation, and Cost Minimization

Shell-and-tube latent heat thermal energy storage units employ phase change materials to store and release heat at a nearly constant temperature, deliver high effectiveness of heat transfer, as well as high charging/discharging power. Even though many studies have investigated the material formulation, heat transfer through simulation, and experimental studies, there is limited research dedicated to the storage unit design methodology. This study proposes a comprehensive methodology that includes the material assessment with multi-attribute decision-making and multi-objective decision-making tools, epsilon-NTU method, and cost minimization using Genetic Algorithm. The methodology is validated by a series of experimental results, and implemented in the optimization of a storage unit for solar absorption chiller application. A unit cost of as low as USD 8396 per unit is reported with a power of 1.42 kW. The methodology proves to be an efficient, reliable, and systematic tool to fulfill the preliminary design of shell-and-tube LHTES before the computational fluid dynamics or detailed experimental studies are engaged.

Thermo-Economic Comparisons of Environmentally Friendly Solar Assisted Absorption Air Conditioning Systems

Absorption refrigeration cycle is considered a vital option for thermal cooling processes. Designing new systems is needed to meet the increasing communities’ demands of space cooling. This should be given more attention especially with the increasing conventional fossil fuel energy costs and CO2 emission. This work presents the thermo-economic analysis to compare between different solar absorption cooling system configurations. The proposed system combines a solar field, flashing tank and absorption chiller: two types of absorption cycle H2O-LiBr and NH3-H2O have been compared to each other by parabolic trough collectors and evacuated tube collectors under the same operating conditions. A case study of 200 TR total cooling load is also presented. Results reveal that parabolic trough collector combined with H2O-LiBr (PTC/H2O-LiBr) gives lower design aspects and minimum rates of hourly costs (5.2 $/h) followed by ETC/H2O-LiBr configuration (5.6 $/h). H2O-LiBr gives lower thermo-economic product cost (0.14 $/GJ) compared to the NH3-H2O (0.16 $/GJ). The absorption refrigeration cycle coefficient of performance ranged between 0.5 and 0.9.

Thermo-Economic Comparisons of Environmentally Friendly Solar Assisted Absorption Air Conditioning Systems

Absorption refrigeration cycle is considered a vital option for thermal cooling processes. Designing new systems is needed to meet the increasing communities’ demands of space cooling. This should be given more attention especially with the increasing conventional fossil fuel energy costs and CO₂ emission. This work presents the thermo-economic analysis to compare between different solar absorption cooling system configurations. The proposed system combines a solar field, flashing tank and absorption chiller: two types of absorption cycle H₂O-LiBr and NH₃-H₂O have been compared to each other by parabolic trough collectors and evacuated tube collectors under the same operating conditions. A case study of 200 TR total cooling load is also presented. Results reveal that parabolic trough collector combined with H₂O-LiBr (PTC/H₂O-LiBr) gives lower design aspects and minimum rates of hourly costs (5.2 $/h) followed by ETC/H₂O-LiBr configuration (5.6 $/h). H2O-LiBr gives lower thermo-economic product cost (0.14 $/GJ) compared to the NH₃-H₂O (0.16 $/GJ). The absorption refrigeration cycle coefficient of performance ranged between 0.5 and 0.9.

4E dynamic analysis of a water-power cogeneration plant integrated with solar parabolic trough collector and absorption chiller

This paper attempts to improve a power-water cogeneration system by combining the existing plant with solar and inlet air cooling systems. The investigations were performed under the climatic conditions of Qeshm Island in Iran. In this regard, the Qeshm power-water cogeneration plant is considered to be improved. This plant consists of two gas turbine units, each with the nominal capacity of 25 megawatts in ISO conditions, two heat recovery steam generators (HRSG), and four MED-TVC desalination policies.Absorption chillier for inlet air cooling of a compressor and parabolic trough collector for solar heating has been considered to integrate with the existing unit. In this regard, different scenarios were examined in each hour in a year. Furthermore, dynamic energy, exergy, exergoeconomic, and exergoenvironmental analyses (4E) have been performed for the base case and proposed scenarios hourly in a year. The high accuracy of the simulation results was confirmed in Thermoflex software and plant data. With the desired changes, the thermal efficiency reaches 68%, and the exergy efficiency increases to about 50%. The economic and environmental shows that the base case's environmental impacts have been reduced by the use of inlet air cooling system and solar heating. Furthermore, dynamic transient 4E evaluations in each hour in a year were determined.

Modeling and simulation analysis of solar absorption chiller driven by nanofluid-based parabolic trough collectors (PTC) under hot climatic conditions

The performance of solar air conditioning system (SACS) using Lithium-Bromide/water (Li–Br/H2O) solution and nanofluid -based parabolic trough collectors (PTC) under hot and humid climate conditions is presented in this study. The main objectives are to investigate the effects of different types of nanofluid (Al2O3/H2O and Cu/H2O) and the concentration of nanoparticle Cu (0.2 and 0.5 wt %) on the coefficient of performance (COP) of SACS system during a winter and summer days in desert regions. Mathematical models of the SACS system including the solar PTC, tank storage and the single-effect Li–Br/H2O absorption chiller are developed. The numerical simulation results show a good agreement with the experiment data accessible in literature. The results show that Cu/H2O nanofluid has the best performance. For the cold day and at noontime, the COP for pure water, 0.5 vol% Al2O3/H2O nanofluid and 0.5 vol% Cu/H2O nanofluid are 0.64, 0.68, and 0.74, respectively. The COP during the cold day increases by 12.5% and 15.5% when the concentration of Cu nanoparticle is 0.2 %vol and 0.5 %vol respectively. For the hot day and between 9:00 a.m. to 3:00 p.m. the maximum COP obtained is 0.77, and the effect of nanofluids is negligible. The single LiBr–H2O air absorption system reaches its maximum operation. A double effect of LiBr–H2O air absorption is needed to improve the performance of the system.

Performance assessment and optimization of a solar cooling system to satisfy renewable energy ratio (RER) requirements in multi-family buildings

In order to meet European targets for decarbonisation in 2050, the amount of building energy needs that must be covered through RES is going to increase. Considering the increasing needs for space cooling, mainly due to climate change, technical solutions involving renewable sources of energy for cooling purposes are of great interest. Solar absorption chillers represent a valid answer, but their use in the residential sector is at early stage.This work explores the ability of a solar cooling system to meet the summer energy demand of a multi-family building located in the Mediterranean area. An energy model was developed in TRNSYS® and a simulation-based optimization framework was used to optimize the system design, maximize its energy benefits and relate energy performance to investment and operational costs.The resulting optimal design has reduced the initial non-renewable primary energy demand by 48%, increasing the renewable energy ratio up to 83%. Results demonstrate the ability of the proposed approach to support valuable design choices in this field and reveal the potential of solar cooling to reach the NZEB target in view of future climate change and the future developments of energy requirements for buildings.

A state of the art on solar-powered vapor absorption cooling systems integrated with thermal energy storage.

The intermittent nature of solar energy is a dominant factor in exploring well-designed thermal energy storages for consistent operation of solar thermal-powered vapor absorption systems. Thermal energy storage acts as a buffer and moderator between solar thermal collectors and generators of absorption chillers and significantly improves the system performance. Vapor absorption chillers are available in half, single, double, and triple-effect modes of operation and operate at temperatures ranging from 75 to 220°C to produce a cooling effect with COPs ranging from 0.3 to 1.8. Thus, the selection of appropriate solar collectors and thermal energy storages are two significant decisions affecting the consistency of output of a vapor absorption refrigeration system. The present review of state of the art is focused on the appropriate selection, from among different types of solar collectors available to meet the demand of capacity and degree of thermal energy required in operating absorption chillers at optimum performance. Characteristics of various thermal energy storage systems and their integration with solar thermal collectors and absorption chillers are also investigated to meet the demand for heat during non-sunshine hours or periods of low solar intensity. In the latter section, economic feasibility is explored so that a sustainable solar cooling system can be proposed which can work consistently with the best performance throughout its entire life.

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.

Effective utilization of natural convection via novel fin design & influence of enhanced viscosity due to carbon nano-particles in a solar cooling thermal storage system

The present work proposes a novel fin design for high temperature solar cooling thermal storage system (TES) which utilizes natural convection more effectively. Different fin structures are investigated for quick heat absorption, and their thermal performance is compared with carbon nanoparticles based TES. It has been observed that the dispersion of carbon nanoparticles increase the effective viscosity of the nano-composite which severely deteriorates the natural convection heat transfer. Moreover, the effective viscosity correlations available in the literature are limited to spherical nanoparticles (without surfactant). Huge discrepancies would result using the same correlations for non-spherical particles like Graphene nanoplates (GNP) dispersed in the Phase change material (PCM). So, the empirical viscosity equations (at different concentration of GNP) are developed in the present work through a series of experimental trials carried on rotational Rheometer. Dynamic Differential scanning calorimetry (DSC) tests are performed to obtain the melting curve and specific heat correlations. The best eutectic PCM for double effect solar cooling system is suggested through systematic and comprehensive methodology using Multi attributes decision making (MADM) tools. The thermal performance of TES with a combination of both fins and GNP is further studied to propose a highly efficient storage system. The case study of a 23 kW solar absorption chiller is also presented to analyze the cost reduction using the proposed fin design. It is concluded that decreasing fin size configuration gives the highest rate of heat transfer. A maximum reduction of 43% in the melting time is observed for TES with the novel finned configuration (at 5% GNP).

Solar absorption chiller performance prediction based on the selection of principal component analysis

In this paper, a method to predict the performance of an absorption chiller using solar thermal collectors as the energy input is analyzed rigorously. Artificial Neural Network (ANN) is developed based on experimental data to predict the performance of the solar absorption chiller system at Universitas Indonesia. In order to perform ANN accurately, some parameters such as chilled water inlet and outlet temperatures, cooling water inlet and outlet temperatures, solar hot water inlet and outlet temperatures, hot water inlet and outlet temperatures, ambient temperature and fuel consumption flow rate are chosen as the input variables. In addition, a Principle Component Analysis (PCA) is used to reduce the number of input variables for performance prediction. Without sacrificing the ANN's prediction accuracy, PCA identified the sensitive variables from all input variables. The developed ANN model combined with PCA (ANN + PCA) shows good performance which has a comparable error with ANN model, specifically the configuration 9–6-2 (9 neurons, 6 inputs, 2 outputs) of the ANN + PCA model leads to a COP root-mean-square error of 0.0145.

Municipal solid waste based multigeneration system for different districts of Karachi

In this study, a novel multi-generation system comprising of municipal solid waste powered Rankine cycle, solar parabolic trough collector, absorption chiller, electrolyser and reverse osmosis, all integrated together to produce useful outputs namely electricity, drinkable water, cooling, warm water, heating, hydrogen and dry air, is proposed and thermodynamic assessment is carried out. Energy analysis and exergy analysis has been carried out by setting up multiple parameters. System performance for different districts in Karachi is then investigated by performing a parametric study by changing system parameters such as municipal solid waste input, calorific values, and ambient temperature, the corresponding changes in system outputs and efficiencies are then compared. The system's average energy and exergy efficiencies are found out to be 88.6% and 60.3% respectively.

Prospects for absorption chillers in Finnish energy systems

Increasing trend in space cooling together with demand of CO2 emission reduction in energy production directs towards environmentally friendlier cooling options. Absorption chillers utilize waste heat in cold production and could, therefore, fit to this need. Finland has a well established district heating system and growing district cooling markets. The trend is towards renewable options in both heat and electricity production. In this study, after introducing basics of absorption chillers, cooling trends in Finland are discussed and prospects of absorption chillers in Finnish district and building energy systems are defined. A number of potential applications are identified and discussed. After an extensive review of literature, the authors conclude that solar driven absorption chiller applications have not been widely examined in Finnish conditions. Particularly absorption systems in trigeneration systems could be feasible also in Finland. Still, further technical and economic analyses for all potential applications are needed.

Solidification behavior of binary eutectic phase change material in a vertical finned thermal storage system dispersed with graphene nano-plates

Thermal energy storage systems (TES) find their extensive application in industrial and solar-powered thermal systems due to their high energy storage density and ability to deliver heat at isothermal conditions. But, the lower thermal conductivity of phase change materials (PCM) reduces the overall rate of heat transfer. In the present work, solidification behavior in a medium temperature (160–200 °C) finned TES with varying proportion of Graphene nano plates (GNP) is presented. The effect of anisotropy, aspect ratio, concentration, interfacial thermal resistance and non-linearity has been included to evaluate the overall thermal conductivity of GNP-PCM composite. The objective of the present study is to enhance the solidification process of a binary eutectic salt LiNO3-KCl in an optimized finned TES dispersed with the different volume fraction of GNP. The detailed experimentation process starts with the preparation of binary eutectic mixture, followed by dynamic Differential scanning calorimetry analyses along with rheology testing. Empirical correlations have been developed using quadratic and cubic polynomials for viscosity and specific heat respectively. Several numerical models are analyzed to study the solidification enhancement of binary eutectic PCM using the real-time plant data of a high-temperature solar absorption chiller. Effects of Stefan and Reynolds number on the thermal performance of storage system has also been studied. Reducing the Stefan number and increasing the Reynolds number of heat transfer fluid (HTF) results in enhancing the rate of solidification process. It has been observed that natural convection currents enhances the rate of solidification and causes faster solidification in the upper annulus of TES. A reduction of 49% in the solidification time has been observed with finned TES dispersed with 5% GNP as compared to pure binary eutectic PCM.

Technical and economic assessment of solar heating and cooling – Methodology and examples of IEA SHC Task 53

Assessing the performance of solar heating and cooling systems, especially cooling systems using solar thermal or photovoltaic driving energy, in a common comparable format, is complicated by the numerous, alternative energy sources and design possibilities. A generalized technical and economic assessment methodology was developed and tested in the course of IEA SHC Task 53. This paper is summarizing the key facts for the assessment and showing the evaluation on the basis of two simulated cases including sensitivity analysis of main boundary conditions.One case is comparing an air/water heat pump with photovoltaic and solar thermal support for a small multifamily house located in Madrid. The second case is comparing a solar thermal driven absorption chiller with a photovoltaic supported heat pump system for a hotel with dominant domestic hot water demand in Innsbruck.The sensitivity analysis shows that photovoltaic and solar thermal systems are cutting across with the same trends. Lower costs have to be derived first, followed by the efficiency of the system. Cost competitiveness is achievable for both technologies with appropriate system design and control strategies.

Boosting Gas Turbine Combined Cycles in Hot Regions Using Inlet Air Cooling including Solar Energy

Cooling the air before entering the compressor of a gas turbine of a combined cycle power plant is an effective method to boost the output power of both the gas and the steam turbines in hot regions. Usually, in hot area, the time at which the demand of power is highest coincides with the time of the largest drop of power generation due to the weather conditions, which shows the importance of air inlet cooling. However, fortunately, the daily peak period of electrical power demand coincides with the peak of solar radiation that is abundant in Saudi Arabia. This paper presents a novel system of cooling the gas turbine inlet air using a solar assisted absorption chiller. The study includes also a comparative analysis of a gas turbine combined cycle power plant performance when it is integrated with conventional and solar-assisted absorption chillers for inlet air cooling with the performance of the plant operating without inlet air cooling. The effect of ambient air temperature on the output power is investigated and reported. The advantage of air inlet cooling in boosting the power of the combined cycle in Dhahran is evident especially in summer. The study revealed that at the design hour under the weather conditions of Dhahran, KSA (July 17th at 1 p.m.), the net power output of the plant drops from 267878 kW to 226361 kW at 48 °C (15.5% drop). While the gross power output of the gas turbine drops from 189472 kW to 151469 KW (20.1% drop) and the steam turbine from 84798 KW to 80495 KW (5.1% drop). Integrating conventional and solar-assisted absorption chillers increased the net power output of the combined cycle by 34964 KW and 37999 KW, respectively. Average and hourly performance during typical days have been conducted and presented. The plants without air inlet cooling system show higher carbon emissions (0.73 kg CO2/KWh) compared to the plant integrated with conventional and solar-assisted absorption chillers (0.509 kg CO2/KWh) and (0.508 kg CO2/KWh), respectively. Also, integrating a conventional absorption chiller shows the lowest levelized electricity cost.

蓄電・蓄熱を考慮したスマート化実証 ソーラー吸収冷温水機を用いた潜熱蓄熱槽の運転実績

蓄電・蓄熱を考慮したスマート化実証 ソーラー吸収冷温水機を用いた潜熱蓄熱槽の運転実績