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Renewable cooling via absorption chillers being supplied by various green heat technologies such as solar collectors has been widely studied in the literature, but it is still challenging to get positive economic outcomes from such systems due to the large expenses of solar thermal systems. This study offers the use of a new generation of solar collectors, so-called eccentric reflective solar collectors, for driving single-effect absorption chillers and thereby reducing the levelized cost of cooling. This article develops the most optimal design of this system (based on several different scenarios) using multi-objective optimization techniques and employs them for a case study in Brazil to assess its proficiency compared to conventional solar-driven cooling methods. For making the benchmarking analyses fair, the conventional system is also rigorously optimized in terms of design and operation features. The results show that the eccentric solar collector would enhance the cost-effectiveness by 29%. In addition, using optimally sized storage units would be necessary to get acceptable economic performance from the system, no matter which collector type is used. For the case study, at the optimal sizing and operating conditions, the levelized cost of cooling will be 124 USD/MWh and an emission level of 18.97 kgCO2/MWh.

A substantial share of the total energy in various countries is consumed by industries and manufacturing sectors. Most of the energy is used for low and medium temperature process heating (up to 3000C) as well as low and medium cooling capacity (up to 350kW). To meet the demand, the industrial sector consumes most of its energy in either thermal (heat) or electrical energy forms. The use of fossil fuels accounts for about half of the overall share. This resulted in a necessity to commercialize local and clean renewable energy sources efficiently considering the reduction of economic dependence on fossil fuels and greenhouse gases emission. As such, solar energy has proven potential and resulted in considerable development and deployment of solar heating industrial processes (SHIP) and solar cooling systems in recent times. Thus, an attempt to present a review of the available literature on overall energy intensiveness, process temperature levels, solar technology match, and solar thermal system performance and cost have been made in this paper. The review also includes identifying the potential and relevance of involving solar thermal for industrial heating and cooling demand. As a result, at least 624 SHIP including promising large-scale plants and 1350 solar cooling systems most of them in small and medium capacities in operation are identified. Though limited data is available for solar cooling potential and installation, investigations projected the global SHIP potential to 5.6 EJ for 2050. Consequently, given the presence of many low and medium temperature heating processes and cooling capacities in industries with immense solar energy potential, developing counties such as Ethiopia can take experience and pay attention to the development of sustainable industrial systems.

The rotary desiccant wheels application in the air conditioning systems are used for the air dehumidification by means of hygroscopic layers for water vapor adsorption. Nevertheless, external heat sources are required for water desorption to close the air treatment cycle. This paper investigates on the possibility to integrate in that cycle a new component, such as the trans-critical CO2 heat pump, to reduce the contribution of external thermal sources. In so doing, the high temperature waste heat discharged by the heat pump hot sink can be fruitfully exploited. Additionally, a PV array has been added to the typical layout based on the solar collectors, in order to assure the heat pump electrical driving. The energy analysis is carried out by calculating the energy performance indicators of the whole cooling system, simulating it by a dynamic model built in the MATLAB SIMULINK environment. Specifically, an air handling unit has been properly sized to supply cooling load to a reference conference hall of 1200 m3, with changes in boundary conditions (i.e. solar radiation, daily temperature and relative humidity variations). Indeed, three different cities representing the most typical Italian climatic zones, have been considered for assessing the proposed technical option suitability., Highlights • A quick overview on the Trans-critical CO2 heat pumps features has been presented. • Dynamic simulation model of a hybrid solar cooling systems with CO2 HP has been built. • Fundamental equations of each component have been reported and implemented in Matlab. • Hybrid system energy performance has been evaluated in three different Italian cities. • Other key performance indicators have been presented and discussed.

The cooling of the surface of the solar photovoltaic (PV) system is a major operative factor in achieving greater efficiency. Correct cooling can improve electrical efficiency and reduce cell degradation rates over time. This results in increasing the life of the solar PV modules. In industrial and domestic utilization, the cooling system is used for the removal of excess heat. This paper presents a new method for cooling systems for solar PV which results in the improvement in the collection of the solar insolation. The additional feature of the method has been the tracking of sunlight for efficient power generation. Further, the extra heat can be utilized for other purposes including heating and power generation through thermal means. The concept of the proposed system has been explained in detail with the pictorial representation. Also, for the validation of the improved performance of the proposed system, a detailed comparison with the conventional methods have been provided for five different cities of Saudi Arabia and an improvement of twice collection of insolation has been estimated compare to the conventional systems. The proposed system shows improved performance for all operating conditions.

A comparative study between two solutions which they usually work as a working pairs in pumpless absorption cooling system is achieved analytically with aid of ESS (Engineering Equation Solver) 9.43 software. The pump in this system is replaced by a vertical pipe (lift tube) to ensure the pressure difference between the condenser and the evaporator. These working pairs are Lithium Bromide-Water and Lithium Chloride-Water. The study intends Iraqi summer weather as an ambient circumstance. A thermodynamics model is designed to find the energy and Energy loss in each of system components. By solving the thermodynamic model, and assuming the same generator, absorber, condenser and evaporator temperatures in each case. It’s found that the system coefficient of performance is relatively the same while the probability of agglomeration in case of Lithium Bromide-Water system is higher because of the large salt concentration. It’s concluded that the Lithium Chloride-Water is most suitable in Iraqi circumstances in spite of high values of total energy loss which is obtained in case of Lithium Chloride-Water system if it is compared with the energy loss value in case of Lithium Bromide-Water 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). Nanyang Technological University The authors would like to thank the collaboration between NTU (Nanyang Technological University) Singapore & IIT Delhi (Indian Institute of Technology). The Ph.D. exchange programme is supported by Energy Research Institute@ NTU (Nanyang Technological University), Singapore. The author (Rupinder Pal Singh) acknowledges Punjab Agricultural University, India for granting study leave and QIP, IIT Delhi for providing a platform to carry out the research work.

Solar-powered adsorption chillers are a particularly interesting alternative to energy-intensive conventional refrigeration systems. Integration of the adsorption chiller with solar collectors is a very promising concept since the increase in solar radiation coincides with the increased demand for cooling. Such a solution is very economical and environmentally friendly. It also fits in with current trends related to energy policy and sustainable development. The article presents the results of tests conducted for a two-bed adsorption chiller integrated with solar collectors. The tests were performed on selected days of the summer period (July and August) at the KEZO Research Centre PAS in Jablonna (Poland). Based on the results obtained, the performance parameters of the adsorption chiller were determined, and the problems associated with the integration of all components of the system were identified and discussed. The values of the determined Coefficient of Performance (COP) and cooling capacity for the tested adsorption chiller are, depending on the day on which the tests were conducted, from 0.531 to 0.692 and from 5.16 kW to 8.71 kW, respectively. Analysis of the test results made it possible to formulate conclusions related to the design of integrated systems of adsorption chillers with solar collectors.

This paper, illustrates a design and simulation of a solar powered absorption refrigeration system preserves food above freezing point. The main system is modified from a commercial conventional system located at Tajoura, Libya. The target is to design and operate the system at high solar fraction and efficiency. The simulation is performed by TRNSYS to evaluate the annual thermal performance of the solar system that consists of 50-kW absorption chiller producing cold for three refrigerated rooms. The model could be classified into two main parts; refrigeration load model and solar powered refrigeration system model. The results demonstrated that the optimum system achieves 51% solar fraction consists of 48 m2 of high performance evacuated tubes solar collectors and 5000-litre thermal storage tank, in order to power a 50-kW absorption chiller that offers cold for three refrigerated rooms of vegetables.

Heat pumps are one of the most promising technologies for residential and industrial applications in the perspective of a decarbonized society. Their role in climate change mitigation can be fully capitalized through their direct coupling with renewable energy sources, among which solar heat is the most abundant one. The systems that feature the integration of heat pumps and solar systems are known as solar-assisted heat pumps. In the present chapter, the fundamentals of mechanical compression and sorption heat pumps are given and their utilization in combination with solar thermal collectors is discussed, highlighting the relevant features of each possible layout according to the expected useful effect and field of application, showing that heat pumping technology has a central role in the reduction of emissions due to heating and cooling production.

Embargado hasta 23/11/2023 Solar heating ventilating air conditioning systems are useful tools to meet the objectives of the European Commission in terms of sustainability in buildings, since their use can reduce the environmental impact, including CO2 emissions, due to their low energy consumption. In order to quantify the improvement that in environmental terms the use of this type of system could entail, in this work it was carried out (a) a comparative life cycle assessment of a solar heating ventilating air conditioningsystem based on vaporative ooling and desiccant wheel with a conventional direct expansion system; and (b) an analysis of feasible modifications of the desiccant wheel based system and their influence on the life cycle analysis results. The experimental desiccant wheel based system showed a slightly higher environmental performance than the conventional direct expansion based system, between 2% and 10%, for the 3 impact categories evaluated: human health, ecosystem quality and resource consumption. When weight optimisation and the reuse of materials were considered, the environmental performance of the experimental based system became even up to between 22% and 50% higher than that of the conventional direct expansion based system. That involved a 60 % reduction in climate change potential indicator, which mainly was influenced by CO2 emissions.

En este trabajo se ha diseñado y construido un prototipo de refrigerador solar por adsorción basado en la pareja carbón activado / metanol. Sus características más novedosas son las siguientes: - Diseño original de concentrador parabólico compuesto (CPC), que permite conjugar una captación solar diurna eficiente con un adecuado refrescamiento nocturno del generador de la máquina. - Condensador refrigerado por agua procedente de un tanque anejo al prototipo. - Sistema de registro experimental continuo de la concentración de metanol en el lecho de carbón, que permite rastrear de forma muy detallada los intercambios térmicos en todos los elementos de la máquina. La máquina fue probada experimentalmente y ofreció un COP promedio de 0,09. Se ha elaborado un modelo computacional para simular el funcionamiento del prototipo. Con él pronosticamos cómo afectan a la eficiencia del ciclo diversas condiciones ambientales así como la variación de distintos parámetros de diseño. _______________________________________ A prototype of solid sorption solar chiller using the activated carbon / methanol couple has been designed and built. Its major features are: - A novel design of compound parabolic concentrator (CPC), allowing a good compromise between daily collection of radiation and an efficient nightly cooling of the reactor. - Water-cooled shell-and-tubes condenser, the cooling water coming from a water tank annex to the unit. - A continuous experimental record of the methanol concentration in the reactor, which permits a detailed analysis of the thermal exchanges in all the parts of the unit. The prototype was experimentally tested, and the average COP was 0.09. A mathematical model to simulate the operation of the unit has been implemented. This model is helpful to forecast the unit performance under a variety of environmental conditions, and as a result of a change in design parameters

This paper performs technical, economic and environmental feasibility analyses of two different solar cogeneration plants, consisting of a solar system (a parabolic trough collector field coupled with thermal energy storage), an Organic Rankine Cycle (ORC), and mechanical chillers, that should cover the electrical and cooling demands of a commercial center located in Zaragoza (Spain). System A is hybridized with an auxiliary biomass boiler that complements the solar system’s thermal production, providing a constant heat supply to the ORC, which operates at full load during the operating hours of the solar system. In contrast, system B is not hybridized with biomass, so the ORC is fully driven by the solar system, operating at partial load according to the solar resource availability. Both systems are connected to the electrical grid, allowing electricity purchases and sales when needed. The design procedure involves the sizing of the equipment as well as the modelling of the hourly behavior of each system throughout the year. The physical analysis is complemented by an economic assessment, which considers investment and variable costs, as well as an estimate of the significant environmental benefits of the proposed plants. The solar plants are compared to a conventional system in which all the electrical consumption is covered with electricity purchased from the grid. The costs of the electricity produced by systems A and B are estimated at 0.2030 EUR/kWh and 0.1458 EUR/kWh, which are about 49% and 7% higher than the electricity purchase price in Spain (0.1363 EUR/kWh). These results indicate that while none of the solar plants are presently competitive with the conventional system, system B (without biomass hybridization) is actually closer to economic feasibility in the short and medium term than system A (with biomass hybridization).

This study discusses the technical, environmental, and economic feasibility of using absorption chillers driven by solar energy and/or natural gas, in selected shopping malls in Barranquilla, Caribbean region of Colombia. The high solar irradiation and the low prices of natural gas in the cities of the Caribbean region of Colombia are attractive conditions for the use of absorption chillers. To prove the feasibility of absorption chillers in the Caribbean region of Colombia, the use of water/LiBr absorption chillers of 352 kW cooling capacity was investigated considering the cooling loads in selected malls. A thermodynamic model was developed to study the performance of the absorption chiller and evaluate different scenarios proposed. The results evidenced that the absorption chiller could reach a maximum COP and SCOP of 0.77 and 0.52, respectively. The different alternatives could reduce gas emissions between 17% and 76% depending on the cooling load covered by the absorption chillers and driving energy input as compared to the current use of mechanical compression chillers. The economic results indicated that the best scenario, considering a lifetime of 20 years, is the gas-driven absorption chiller with IRR varying from 40% to 54.6% depending on the mall cooling load covered.

Summary: Worldwide cooling energy demands will increase by four times by 2050. Thermally driven cooling technology is an alternative solution to electric heat pumps in removing hazardous refrigerants and harnessing renewables and waste heat. We highlight the advantages of water-stable microporous aluminum-carboxylate-based metal-organic frameworks, or Al-MOFs, as sorbents in the application of producing cold from heat. Here, we synthesize the Al-MOFs with green and scalable processes, which are prerequisites for exploring various industrial and civil applications. A proof-of-concept full-scale adsorption chiller with different Al-MOFs is built up with optimized configurations derived from various characterization techniques. The tested Al-MOFs achieve thermal efficiency above 0.6 and specific cooling power over 1 kW/kg in typical cooling scenarios. Notably, when solar thermal energy is used as the heat source in an outdoor validation, Al-MOFs are weather-resilient solutions that exhibit a stable energy conversion efficiency under fluctuating operating conditions (ambient temperature and solar irradiation).

A large fraction of cooling demand depends on solar radiation intensity, therefore a strong attention was directed toward solar cooling immediately after the 1973 energy crisis. Whereas pilot solar cooling plants were built up and experimented, this technology never really took off. A recent survey reported something more than 1000 plants operating, a very modest number with respect the great potential of solar cooling. A review of technologies as they developed in the past, operate in the present with a forecasting for the future is here proposed to follow how the technology evolved during almost half a century regarding the solar section and the relative refrigeration equipment. The analysis allows to take stock of the situation selecting solar sections, cooling machines and their coupling which seem nowadays more suitable for wide application in the near future. A study is proposed at the end to put together some energy evaluations in different climates and much more difficult economical evaluations to investigate whether a possible fossil fuel parity cost can be attained, if not today, in a near future.

The present paper aims to evaluate the performance of a solar district cooling system in typical Middle East climate conditions. A centralized cooling station is supposed to distribute chilled water for a residential compound through a piping network. Two different solar cooling technologies are compared: two-stage lithium-bromide absorption chiller (2sABS) driven by Parabolic Trough Collectors (PTCs) vs. single-stage lithium-bromide absorption chiller (1sABS) fed by Evacuated Tube Collectors (ETCs). A computer code has been developed in Trnsys® (the transient simulation software developed by the University of Wisconsin) to simulate on hourly basis the annual operation of the solar cooling system, including building thermal load calculation, thermal losses in pipes and control strategy of the energy storage. A solar fraction of 70% was considered to size the solar field aperture area and the chiller capacity, within a multi-variable optimization process. An auxiliary compression chiller is supposed to cover the peak loads and to be used as backup unit. The two different solar cooling plants exhibit strongly different performance. For each plant configuration, the model determined the optimal size of every component leading to the primary cost minimization. The solar district cooling configuration based on 2sABS and PTCs shows higher performance at Riyadh (KSA) climate conditions and the overall cost is 30% lower than the one of the single-stage absorption chiller plant.

The present paper presents the development of a thermal energy storage system for application with non-concentrating solar plants using phase change materials (PCMs). The outcomes of an experimental analysis on commercial and non-commercial PCMs suitable for the desired temperature range is presented, with main focus on to the enthalpy and the cycle stability of the materials. Particularly, a first evaluation of possible degradation mechanisms in hydrated salts was investigated by means of Nuclear Magnetic Resonance (NMR) spectroscopy. The best performing materials have been implemented in a numerical model, based on the enthalpy method, used for the design of a thermal storage system. The configuration of the system, starting from a simple shell-and-tube layout, has been optimised by inserting asymmetric fin-and-tubes and the results with two selected materials have been compared. The analysis has shown that the most promising materials are the commercial ones belonging to the classes of paraffinic materials and hydrated salts and that, with the designed configuration, it is possible to store up to 200 kJ/m3 and get a peak power during discharge of about 1.5 kW.

Absorption chillers can use waste heat, solar heat, or excess heat by cogeneration facilities to supply chilled water. Therefore, absorption chillers are important components for poly-generation, which can improve plant utilization and efficiency of the overall energy supply system. Currently, 27 new small and medium-scale (30–160 kW cooling capacity) absorption chillers with high efficiency in full- and part-load as well as low specific size and weight are the focus of two research projects sponsored by German Federal Ministries. The chillers are located in 20 different sites, four of them in Jordan and the rest in Germany. The main objective of these projects is to enhance trigeneration and solar cooling system efficiency. The Jordan projects and more than 70% of the German installations use dry cooling towers. Combined heat and power (CHP) plants or district heating grids provide the driving heat for regeneration at the German installations. Solar thermal collectors drive one German and all Jordan installations. Within the projects, the chillers are provided with an intelligent control algorithm that allows achieving several objectives at the same time. One of the objectives, of course, is to match the desired chilled water temperature as well as the cooling capacity. Another objective is, for instance, to fit the hot water outlet temperature. This is commonly essential in cogeneration to avoid emergency shutdowns of the CHP engine. The field operation shows that the deviation of said temperatures from the set point is usually less than ±0.5 K in operation. In those operational hours in which the temperatures of the heat source or heat sink do not allow to reach all objectives, a set of hierarchical aims can be established within the algorithm so that the chiller can be controlled to match its prioritized objectives. Furthermore, the designed absorption chiller performs dynamically and autonomously in a very large range of temperatures and flow rates. These can vary from 20% up to 150% of nominal conditions. This flexibility can be used to achieve up to 80% savings of electrical power consumption using speed-controlled pumps in part load conditions. In contrast to the common opinion that small and medium-scale absorption chillers are not competitive as compared to compression chillers, this paper shows applications in which absorption chillers are advantageous because of synergies with and multiple benefits within the rest of the energy supply system.

A solar cooling system with an optimized air-cooled double-effect water/LiBr absorption machine is proposed as a sustainable alternative to meet cooling demands in dry hot climates. This system allows eliminating the cooling towers in those regions of the planet where water is scarce. This work analyses the environmental benefits of this air-cooled system, as well as its environmental foot-prints, compared to a solar water-cooled single effect. In this regard, a methodology has been applied to calculate the annual saving in water consumption produced in a case study: a hospital located in Almer?a, in South of Spain. Further-more, the reduction in energy consumption and CO2 emissions is also quantified since this machine can be driven by solar energy and with higher efficiency than those of single effect.

Copyright: © 2021 by the authors. In solar-thermal adsorption/desorption processes, it is not always possible to preserve equal operating times for the adsorption/desorption modes due to the fluctuating supply nature of the source which largely affects the system’s operating conditions. This paper seeks to examine the impact of adopting unequal adsorption/desorption times on the entire cooling performance of solar adsorption systems. A cooling system with silica gel–water as adsorbent-adsorbate pair has been built and tested under the climatic condition of Iraq. A mathematical model has been established to predict the system performance, and the results are successfully validated via the experimental findings. The results show that, the system can be operational at the unequal adsorption/desorption times. The performance of the system with equal time is almost twice that of the unequal one. The roles of adsorption velocity, adsorption capacity, overall heat transfer coefficient, and the performance of the cooling system are also evaluated. Iraqi Ministry of Higher Education and Scientific Research / Research and Development Department / Program of Renewable and Sustainable Energy Projects, grant number 1613.

The result of the joint efforts of University of Bergamo and Mohammed Bin Rashid Space Centre (a Dubai Government institute) is the first Energy+ building in Dubai, virtually off-the-grid and PassivHaus certified. The present work deals with the computer models developed to predict the energy performance and to guide the design choices of the two floor office building unveiled to the public in November 2016. Trnsys software has been used to revise and validate the architectural ideas and the energy design.

This paper seeks to present a panorama of cooling related research in office buildings, categorising reported research experiences from the past 25 years in order to identify knowledge gaps and define current paths and trends for further exploration. The general goal behind this research is to support the design of sustainable office buildings in warm climates through examination of past experiences, thus the paper focuses on strategies at building level and specially related with façade design. Peer reviewed journal articles were selected as the source for the study, given the reliability of the information published under peer-review processes. Several queries were carried out throughout three online journal article databases (Web of Science, SCOPUS and ScienceDirect), considering published papers from 1990 onwards. The resulting article database was then explored trough descriptive analysis and in-depth review of some articles to expand on specific topics in order to thoroughly visualise scientific interest and tendencies within the field of study for the last 25 years. As results of the review it is possible to state the high current relevance of cooling research, having experienced an increase of publications under different climate contexts and varied topics ranging from passive to solar cooling, which is seen as a research field on its own. Also, in terms of research methods, software simulations seem to be the primary tool for cooling research, which makes sense for performance driven developments. On the other hand, the main knowledge gaps identified are the need for specific research regarding possibilities for application and architectural integration of cooling systems; the lack of articles addressing some specific cooling strategies, such as the use of evaporative and ground cooling; and the need for more information about the operation of cooling systems, especially taking users’ perception and their behaviour into account.

Solar cooling technology is an attractive way to use solar thermal energy to produce cooling for buildings. The employment of taphase change materials (PCMs) as heat storage medium, to increase the range of utilization of solar thermal energy, thus improving the overall system performance, is considered very attractive. Nevertheless, in order to allow the development of latent heat storage prototypes for such an application, it is mandatory to verify the thermo-physical performance as well as the long-term stability of the available materials. To this aim, in the present paper, the most attractive commercial PCM as well as neat chemical compounds operating in the temperature range between 80 °C and 100 °C, perfectly suitable for non-concentrating solar cooling systems, have been identified and completely characterized. In particular, several cycles have been performed on each material, to verify possible instabilities in their behavior. Most of the neat materials have confirmed to be promising for this application, thanks to their really high melting enthalpy, up to 255 J/g as showed for Aluminum Ammonium Sulfate Dodecahydrate. Nevertheless, all these materials are still not stable, showing high supercooling, allotropic phase transition, incongruent melting and even absence of re-crystallization, which makes necessary an intense work to bring them to a reliability level sufficient for real application. On the contrary, the commercial PCMs, even if mostly characterized by lower melting enthalpy, ranging between 120 and 150 J/g, confirmed their stability, which makes them ready for practical applications.

Producción Científica, In this work, we present an absorption cooling system with 35 kW capacity driven by solar thermal energy, installed in the school of Puertecitos, Mexico, an off-grid community with a high level of social marginalization. The cooling system provides thermal comfort to the school’s classrooms through four 8.75-kW cooling coils, while a 110-m2 field of evacuated tube solar collectors delivers the thermal energy needed to activate the cooling machine. The characteristics of the equipment installed in the school were used for simulation and operative analysis of the system under the influence of typical factors of an isolated coastal community, such as the influence of climate, thermal load, and water consumption in the cooling tower, among others. The aim of this simulation study was to determine the best operating conditions prior to system start-up, to establish the requirements for external heating and cooling services, and to quantify the freshwater requirements for the proper functioning of the system. The results show that, with the simulated strategies implemented, with a maximum load operation, the system can maintain thermal comfort in the classrooms for five days of classes. This is feasible as long as weekends are dedicated to raising the water temperature in the thermal storage tank. As the total capacity of the system is distributed in the four cooling coils, it is possible to control the cooling demand in order to extend the operation periods. Utilizing 75% or less of the cooling capacity, the system can operate continuously, taking advantage of stored energy. The cooling tower requires about 750 kg of water per day, which becomes critical given the scarcity of this resource in the community., CONACYT-SENER-SUSTENTABILIDAD ENERGÉTICA (project P09), Programa Iberoamericano de Ciencia y Tecnología para el Desarrollo (project 518RT0558)

Due to recent changing climate conditions and glazing of building facades, a rapid increase in the requirement of cooling systems can be observed. Still the main energy source for cooling are fossil fuels. In this article we report on a fully integrated approach of running a heat pump for actively cooling a test room by electric energy, generated by facade integrated photovoltaic modules, the “COOLSKIN” system. Photovoltaic facades are emission free in the operation phase, efficiently utilize otherwise unused surfaces, and portray a favorable method in terms of construction physics and the architectural design of buildings. Compared to existing systems, COOLSKIN is an entirely autonomous system where every component is located inside the facade structure which introduces a high level of plug and play character. In this article the analysis of the electric performance of the COOLSKIN system with respect to its operation under different environmental conditions is presented. The over all system efficiency was determined with 73.9%, compared to a simulated efficiency (PV*SOL) of 68.8%, and to the theoretically expected value of 85%. The system behavior is evaluated depending on photovoltaic output and the cooling demand. The analysis shows that a considerable amount of cooling demand could be decentrally fulfilled with photovoltaic energy, but environmental conditions as well as system layout have a considerable impact on system performance.

Adsorption cooling systems (ACS) may contribute towards a sustainable way of satisfying the increasing cooling demand, as they utilize solar thermal energy and employ non-ozone-depleting substances. Apart from the intrinsic ACS performance, the successfulness of its operation depends on its integration within the entire thermal system (solar collectors, thermal storage and building), which is not straight-forward due to thermal inertia effects and its inherent cyclic operation. Numerical simulations can contribute in understanding the system behavior, its adequate dimensioning and the implementation of optimized control strategies. A computational model was developed, capable of performing conjugate, dynamic simulations of the entire thermal system. The influence of the control criteria is investigated and quantified through three simulation phases, conducted for various solar collectors areas and storage volumes. Higher solar fraction is achieved for lower auxiliary heater activation temperature and lower temperature difference activation of the solar pump. Subsequently, simulations with variable cycle duration were performed, using optimized cycle duration according to the instantaneous operating temperatures. This approach reduces significantly the auxiliary consumption or satisfies the demand with less solar collectors. The potential CO 2 emissions avoidance is calculated between 28.1–90.7% with respect to four scenarios of electricity-driven systems of different performance and CO 2 emission intensity.

In many countries, solar cooling systems are one of the best candidates to tackling global warming and summer peak loads of building air conditioning systems. In this work, based on the collaboration with the Saudi research institute “King Abdullah City for Atomic and Renewable Energy”, two types of solar driven cooling systems are investigated and compared: the open-circuit Desiccant Evaporative Cooling technology and the system based on single-stage LiBr absorption chillers. A computer code has been developed in Trnsys® to simulate a well-insulated single-family residential building, starting from a 3D model of the building architecture, and the solar cooling systems. The simulations have been carried out for two different locations: one in a dry desert area (Riyadh, KSA), the other one on the seaside (Abu Dhabi, UAE). The results show that absorption chillers need a very effective heat rejection system to work properly, whilst DEC systems exhibit a dramatic performance reduction in wet climates.

Solar cooling is a state of the art technology in the last years, especially for countries with high irradiation level as Greece. The objective of this study is to determine the performance of an efficient solar cooling system for Athens, the most populated city in Greece. The examined solar cooling system is a one stage water/lithium-bromide absorption chiller driven by a parabolic trough collector coupled with a storage tank. A numerical model is developed in order to simulate the dynamic performance of this system. Many parameters have been investigated through sensitivity analyses and their optimum values are determined. The mass flow rates and the storage tank volume are the parameters that have been examined parametrically. The final results proved that by using a PTC module with an aperture area of 14 m 2 , a building area of about 25 m 2 can be cooled for 13 h daily during the summer period. The optimum specific mass flow rate was determined to 0.03 kg/sm 2 and the optimum storage tank volume to 0.3 m 3 . Moreover, a case study for a typical building of 100 m 2 is presented with very satisfying results, where four PTC modules are used in parallel connection.

This paper presents an innovative system for solar thermal process steam and chilled water production. The system consists of a 2-stage solar thermally driven steam jet ejector chiller with latent heat and cold storage driven by motive steam from evacuated tube collectors with compound-parabolic-concentrator (CPC-collectors). Within this paper the design and the functionality of the demonstration plant and essential aspects of the system control are discussed. In addition, operational experiences, the operational behaviour of the entire system as well as performance figures are presented and evaluated.

Double-lift absorption cycles represent a suitable solution for air-cooled thermally driven cooling applications. Among the several existing double-lift configurations, semi-GAX cycles are known as the most promising in terms of efficiency. These cycles incorporate the GAX effect in a pressure staged cycle, by means of a split on the solution leaving the low pressure absorber. Two configurations of the semi-GAX cycle have been proposed in the past, the semi-GAX 1 and the semi-GAX 2. The former achieves the GAX effect between the intermediate and the high pressure levels, the latter between the low and the intermediate. Within this paper, the semi-GAX cycles are numerically investigated at operating conditions suitable for a low temperature driven (e.g., by flat plate solar collectors) air conditioning application. The peculiarities of the two cycles are described and the factors affecting their performances are underlined. The COP resulted to be strongly influenced by the split ratio, which determines the intermediate pressure and the possibility to achieve the GAX effect. If the split ratio is optimized to achieve the maximum COP, the COP is higher for semi-GAX 2 for air temperatures below 27 °C and for semi-GAX 1 above. In both cases, the maximum air temperature which allows a circulation ratio below 15 is 40 °C, with chilled water at 7/12 °C and driving temperature of 90 °C.

The paper investigates the introduction of a solar heating and cooling system in an office building characterized by low energy demand with respect to the current national building stock and located in Southern Italy. Dynamic simulations are carried out in order to evaluate the thermo-economic performance of the analyzed system considering different solar panel technologies (flat plate and evacuated tube), tilt angles (10–70°), collecting areas (30–60 m 2 ), hot and cold storage sizes, reference emission factors, electricity and natural gas unitary prices. To satisfy cooling demand a small scale adsorption chiller activated by thermal energy available from solar collectors is considered. The solar heating and cooling system demonstrated primary energy saving and equivalent dioxide carbon emission reduction higher than 23% in comparison to the reference conventional system. The results show that the solar energy system will be competitive when the electricity and natural gas prices will be high and strong government incentives will be provided.

Solar thermal cooling technology is currently facing a very exciting challenge. Air conditioning is a large and growing energy consumer, especially in sunny and developing countries. Worldwide efforts to develop renewable energy solutions must address this critical cooling application. Solar thermal energy presents a natural and strong opportunity to do just this. However, even if reliable technologically advanced products are presently available, the solar cooling sector must leap from a pre-industrial and demonstration status into a competitive mass market. Despite this, some applications, particularly for large buildings with combined cooling and domestic hot water production, are already very close to cost competitiveness without any incentives. This paper will concentrate on introducing an international collaborative R&D activity called IEA SHC Task 48 in the field of solar cooling and the methodology, participating entities and initial outcomes.

Within IEA-SHC Task 48 “Quality assurance and support measures for Solar Cooling” the most crucial components of solar thermal cooling plants have been analyzed in detail aiming at improving their quality. Test procedures for characterizing continuous and discontinuous chillers have been developed; market available heat rejection devices have been investigated, rating their performance through monitoring data and comparing them; pump efficiency has been also investigated and design guidelines for pump selection and hydraulic configuration are now available; a detailed and updated database of medium temperature collectors has been built.

The greenhouses cultivation causes in summer season inner conditions characterized by high thermal levels such as to generate problems that can damage crops. Always more frequently for this reason it is common to provide greenhouse with air conditioning plants. In this work it will be presented an application of a solar cooling plant with absorption cooling machine for thermal control of a greenhouse and an advanced simulation model able to evaluate optimal plant configurations and controls. Solar cooling systems can be applied for greenhouse climate control in regions with high values of solar irradiation as alternative to traditional evaporative systems, allowing the reduction of primary energy consumption by exploiting the contemporaneity between the cooling requirements and the solar energy availability. The plant consists of a single effect LiBr-H2O absorption chiller fed by evacuated-tube solar collectors; the model was developed in Matlab-Simulink and is able to simulate dynamically, with time steps up to 15 minutes, the greenhouse cooling demand and the production of the solar field. Present study proposes a plant configuration with a distribution system in which the cooling power is not provided for the entire volume of the greenhouse, but only for the air volume surrounding the crop with a considerable saving of reduction of energy demand and an extremely efficient use of solar energy. The simulation study is based on the experimental data collected at the experimental center of the University of Bari, Southern Italy. The aim of the work is to demonstrate that solar cooling system could provide significant energy-saving opportunities for cooling greenhouses allowing the reduction of primary energy consumption by exploiting the contemporaneity between the cooling requirements and the solar energy availability.

This papers discusses solar powered absorption cycle performance by simulating different component temperatures. The main components that were investigated included a generator, condenser, absorber and evaporator. The COP was optimized against the generator temperature while varying the other temperatures one at a time. The considered range for the generator temperature was 55–85 °C (131–185 F). The optimum value for the evaporator temperature was 10 °C (50 F), while that for the condenser and absorber was 30 °C (86 F). The optimized COP was around 0.776 with the above selected components' temperatures and for generator temperatures higher than 70 °C (158 F). A simulation for the proposed optimized system was run for a 250 m2 (2691 ft2) house located in Indiana, USA and it was found that 13 solar collectors, having a 2 m2 (21.5 ft2) surface area each, were needed to run the generator along with a storage tank ranging in size from 1300 to 1700 L (343–450 gallons). The initial cost for such systems is much higher than that for conventional cooling systems, but the savings from the sustainable running cost offsets such higher initial costs over the long time. With the significant drop in collector prices and available incentives from the government and state agencies to use such sustainable systems, the payback period could be significantly improved.

Performance assessment of a two-bed silica gel-water adsorption refrigeration system driven by solar thermal energy is carried out under a climatic condition typical of Perth, Australia. A Fourier series is used to simulate solar radiation based on the actual data obtained from Meteonorm software, version 7.0 for Perth, Australia. Two economic methodologies, Payback Period and Life-Cycle Saving are used to evaluate the system economics and optimize the need for solar collector areas. The analysis showed that the order of Fourier series did not have a significant impact on the simulation radiation data and a three-order Fourier series was good enough to approximate the actual solar radiation. For a typical summer day, the average cooling capacity of the chiller at peak hour (13:00) is around 11 kW while the cyclic chiller system coefficient of performance (COP) and solar system COP are around 0.5 and 0.3, respectively. The economic analysis showed that the payback period for the solar adsorption system studied was about 11 years and the optimal solar collector area was around 38 m2 if a compound parabolic collector (CPC) panel was used. The study indicated that the utilization of the solar-driven adsorption cooling is economically and technically viable for weather conditions like those in Perth, Australia.

A new generation of compressor-free heat pumps based on adsorption technology and driven by solar energy is available. Performance and costs are, however, the main obstacles to their commercial diffusion, and more material and system developments are required. In this work, a new coating made of microfibres produced by the electrospinning of polymer/zeolite mixtures is presented. Three different polymer carriers, polyvinyl acetate, polyethylene oxide and polystyrene, have been used together with zeolite SAPO-34 as an adsorbing material. Electrospun microfibres showed a mean diameter ranging from 0.75 &mu, m to 2.16 &mu, m depending on the polymer carrier, with a zeolite content from 60 wt.% to 87 wt.%. Thermal analysis (TGA-DSC) results showed that water desorption from microfibres at T = 150 &deg, C was close to 17 wt.%, a value in agreement with the adsorption capacity of pure SAPO-34. The morphology characterization of coatings demonstrated that the microfibre layers are highly porous and have an elevated surface area.

This paper presents the dynamic modelling of a hybrid cascade chiller for solar cooling in industrial applications driven by Fresnel solar thermal collectors. The chillercomprises an adsorption module, which is directly connected to the bottoming vapor compression chiller. This cascade configuration allows enhancing theoverallelectric COP, since the adsorption module is operated to dissipate the heat rejected by the vaporcompression chiller, thus reducing the condensation temperature quite below the ambient temperature. The model was implemented in Dymola/Modelica, allowing describingheat and mass transfer phenomena insideeach component. The complete model was then validated against experimental data obtained on a cascade chiller prototype at the CNR ITAE lab. Finally, a reference daily simulation was performed to evaluate the ability of the developed chiller in providing cooling energy to a typical industrial application.

Utilising solar energy as the main energy source for air conditioning systems can reduce coal fired electricity consumption and greenhouse gas (GHG) emissions. This thesis explored a novel approach to apply photovoltaic thermal (PV/T) technology for desiccant air dehumidification and cooling systems (refer to as 'desiccant cooling system' from here onwards). A desiccant cooling system and a flat plate PV/T water heating application were tested separately. Theoretical models were developed and validated against experimental results. Through a parametric analysis of a coupled flat plate PV/T collector and desiccant air dehumidification system, results showed that by keeping inlet air temperatures low, the dehumidification performance can be enhanced. And thus, lower desiccant regeneration temperatures can be used. Furthermore, this analysis utilised the dimensionless parameter of number of transfer units (NTU) to determine optimal conditions. That is, optimal conditions that reduce heat source temperatures for the desiccant regeneration process. A novel ground coupled flat plate PV/T desiccant cooling cycle was examined. This cycle implements approaches to keep the heat source temperature low which allows the use of flat plate PV/T collectors to provide thermal energy for the desiccant regeneration process, as well as generating electricity. This contributed to high annual system coefficient of performance (COP). Results showed that the novel design, when optimized, can provide sufficient dehumidification while being more energy efficient than the dew point dehumidification approach. In addition, it was found that the examined solar desiccant cooling system can achieve indoor thermal comfort in most climates in Australia. This research demonstrated the feasibility of utilising flat plate PV/T collectors as the main energy source for desiccant cooling systems.

International audience; This paper presents a smart design named PV COOLING to produce solar cooling using low GWP heat pump system coupled with a standard photovoltaic plant. A maximum of self-consumption is promoted by means of a light bank of batteries and chilled water tank. For this, a test bench has been installed on the building roof in the south of France with the originality to be entirely controllable in terms of building load injected. Thereafter, this new system aims to be used for airconditioning and/or dehumidification in the tertiary sector and positive cold storage in the industrial sector in countries where climatic, regulatory and technical conditions are suitable. PV COOLING potential is developed within a market study. The aim of this study is to assess the thermal / electrical performances of our test bench with the purpose to airconditioning a building by means of several sensors and meters.

In last decades, much effort has been made to drive cooling cycles exploiting renewable energy sources. The use of solar energy is one of the most attractive solutions especially for air conditioning, as availability of solar radiation and cooling loads are approximately in phase. Solar cooling based on water-lithium bromide absorption chillers is the most promising technology for low-medium temperature heat sources (80-100 °C). Small (15-40 kW cooling capacity), medium (50-250 kW) and large scale (up to tens of MW) units are currently at commercial stage. In the present work, the development of a novel micro-scale LiBr absorption chiller (around 5 kW) is presented. The objective is to demonstrate the technical feasibility and to investigate the performance under different operating conditions. A computer code has been developed to simulate a LiBr absorption chiller. The model computes mass flow rates, temperatures, pressures and mass concentration of LiBr-water solution in all the chiller components, both in design and off-design conditions. Giving as inputs inlet temperature and mass flow rate of the external circuits (hot water source, cooling water and chilled water), the computer code is able to evaluate the efficiency (COP) and the actual cooling capacity. The simulation code has been used to size the heat exchangers and to design a prototype of a micro-scale chiller. The chiller prototype with a 5 kW nominal cooling capacity has been manufactured and fully instrumented in order to monitor all physical quantities in the internal and external circuits. The prototype is installed on a test rig at the Energy System and Turbomachinery Laboratory of Bergamo University. Measurement devices, data acquisition system and in-house monitoring software are described in the paper. Preliminary results of the experimental investigation are presented.

The paper reports the preliminary experimental results of an hybridization between a classic ventilated facade and photo-voltaic panels powering a Peltier cells system to improve the inner summer comfort with an environmental friendly approach. The outer layer of the facade is made of photovoltaic panels while a pair of light alloy heat exchanger, coupled on the opposite sides of the Peltier cells, are fitted between the internal space and the air chimney of the facade. The Peltier cells are electrically wired directly with the solar cells: the more the sun affects the front, the more the solar cells produce power to feed the Peltier cells that work as a static heat pump, cooled by the air flowing through the interspace of the ventilated facade. This will result in an inside cooling effect and this effect shall be summed with the well-known passive good performance of the ventilated facade in summer sunny days. During the winter, a simple switch of the power polarity would result in a free inner heating effect, partially using the solar energy incident on the front: the risk of icing on the cold exchanger in the chimney would be reduced because of the heat transmitted by the rear side of the photo-voltaic cells. A small scale prototype has been tested during summer, showing an improvement of the inner air temperature of about 3-4 K during the sunniest hours, in comparison with the unequipped case.

In hot dry climates, due to the high demand for space air conditioning during summer and the abundance of solar radiation, solar air conditioning is a promising approach to reduce the energy consumption and negative environmental impact of buildings. Solar cooling systems have used various types of collectors to drive chillers. In this paper, a salinity gradient solar pond is suggested as a collector to drive an absorption chiller, to provide cool air for a house during hot and dry weather. A coupled simulation between MATLAB and TRNSYS has been used to solve the problem. MATLAB code was written to solve the governing equations for the salinity gradient solar pond and the ground underneath it. TRNSYS software was used to model the solar cooling system including the absorption chiller and building. The weather data used was for Baghdad in Iraq. It was found that the salinity gradient solar pond could be used to drive the absorption chiller and produce cool air for a single family house during the summer period. Different solar pond areas were tested with the same chiller capacity. It was found that a solar pond area of approximately 400 m 2 was required to provide satisfactory cooling for a typical house with a floor area of approximately 125 m 2 .

This article describes the development of the SolabCool®. The SolabCool® is an air-conditioning unit for one family dwellings and or small offices. It is based on solar or waste heat driven adsorption cooling. The process is intermittent, so 2 tanks with silica gel at reduced pressures are used. To make the machine cost-effective and easy to use, two completely new valves were developed, patented and implemented, in combination with an advanced control unit. A pilot manufacturing plant is in operation since end of 2013. The first modules were produced and tested. The maximum so-called cold factor for the SolabCool® is 0.55. The cold factor is rather stable at a large variety of operation conditions, i.e. climate conditions. This is a very good result compared to other semi-intermittent air-conditioners. Demonstration in the market in The Netherlands started in 2014. The design freeze of the SolabCool® is carried out in the summer of 2014 and the pilot production will start.

In this study, an experimental investigation on performance of solar driven with direct current (DC) motor vapor compression refrigerator through indoor and outdoor tests with/without thermal storage and with/without loading is carried out in hot arid areas. The experimental setup main components are multi-crystalline Photovoltaic (PV) module, battery as a buffer for constant 12 V DC and 50 liter portable refrigerator with/without PCM thermal energy storage. In addition, a theoretical model is established to evaluate the refrigerator performance when operated under different environmental conditions of the design point. Thereafter the model is used to size a larger cooling capacity solar driven refrigerator. The results show that this system can be used in remote hot arid areas for refrigeration of post-harvest crops transportation activities. From outdoor results at PCM – full load condition, a COP of 1.22 is achieved and storage temperature of 5 °C is achieved at third day and 0 °C at sixth day.

Summer air conditioning represents a growing market in buildings worldwide, with a significant growth rate observed in European commercial and residential buildings. Available heat driven cooling technologies can be used in combination with solar thermal collectors to reduce the load caused by air conditioning on the electric utilities and to reduce the environmental impact. This work reports a performance analysis of an open cycle solar cooling plant. The plant, installed in Northern Italy, is based on a liquid desiccant evaporative cooler coupled with a solar field. Experimental tests run during summer show average primary energy ratio and primary energy saving index of about 1.6 and 30%, respectively. Though this performance is satisfactorily, the regeneration unit always operated near the lower bound of the nominal temperature range. Therefore, optimization of the solar system design could lead to higher performance.

Within the framework of the French program called Emergence aimed at financing high quality solar heating and cooling demonstration projects, a first solar cooling installation was designed in 2011, then installed and monitored since the beginning of 2013. This installation is based on an innovative and energy efficient concept to optimize solar energy valorization all year long: hybrid solar Domestic Hot Water and cooling strategy. This installation has been fully monitored from spring 2013 until spring 2014 with cooling / DHW production and permits to show the high interest of such strategy to combine long term quality, simplicity of use and economical efficiency. In summer 2013, the hybrid strategy led to a very promising electrical efficiency (or Electrical COP) of more than 12 (ratio between useful solar energy (cooling and DHW) and electrical parasitic consumption).

Solar cooling has been proved to be technically feasible. It is particularly an attractive application for solar energy, because of the near coincidence of peak cooling loads with the available solar power. Currently, most of the solar cooling systems commonly used are the hot water driven lithium bromide absorption chillers. Solar absorption cooling systems are available from various reports, in large capacities up to several hundred kilowatts. In this paper, a minitype solar absorption cooling system was designed and installed in Shanghai Jiao tong University. The system mainly contains 96 m2 solar collector arrays, one absorption chiller with the rated cooling capacity of 8 kW, and a heat storage water storage tank of 3 m3 in volume. The chilled water can be delivered either into fan coils or into radiant cooling panels which are installed to satisfy the indoor thermal environment of the test room. As for the fan coil cooling mode, it was found that the average cooling output reached 3.62 kW during 8 h operation under typical weather condition of Shanghai. With regard to radiant cooling mode, an individual fresh air unit was installed for the purpose of preventing the cooling panels from condensation. Compared with the experimental results of the fan coil cooling mode, the average cooling output of the radiant cooling mode reached 4.47 kW, which increased by 23.5%. Furthermore, the PMV inside the test room was between -0.5 and 0.5, which showed great advantage in meeting the indoor thermal comfort.

The aim of this paper is to define and implement a continuous commissioning methodology that can be effectively applied to a solar driven desiccant and evaporative cooling (DEC) system. The objective is to assess the energy performance of the system's components and identify possible operation faults. The methodology consists in the breakdown and analysis of the DEC into sub-systems; for each of them a simplified dynamic mathematical model based on experimental data has been developed. A possible fault is detected when the difference between the theoretical and measured performances is higher than the accuracy of the methodology. The proposed methodology has been successfully implemented for a hybrid solar DEC system comprising a non-conventional DEC air-handling unit, a solar thermal system and an electrical heat pump. The results of the methodology's application to the first experimental data of summer 2014lead to the following conclusions: the solar sub-system operated as expected whereas the heat pump and the desiccant rotor did not. In particular, the electrical heat pump has a higher cooling capacity than the one predicted at partial load but with a similar COP value, this deviation is mainly due to the assumed partial load performance coefficient. The desiccant rotor presents a much lower performance than the one expected. However, the rotor inefficiency is difficult to highlight due to the high measurement uncertainties on the air side.