Search

Data centers (DCs) are highly energy-intensive facilities, where about 30%–50% of the power consumed is attributable to the cooling of information technology equipment. This makes liquid cooling, especially in two-phase mode, as an alternative to air cooling for the microprocessors in servers of interest. The need to meet the increased power density of server racks in high-performance DCs, along with the push towards lower global warming potential (GWP) refrigerants due to environmental concerns, has motivated research on the selection of two-phase heat transfer fluids for cooling servers while simultaneously recovering waste heat. With this regard, a heat pump-assisted absorption chiller (HPAAC) system for recovering waste heat in DCs with an on-chip two-phase cooling loop driven by the compressor is proposed in the present paper and the low GWP hydrofluoroolefin refrigerants, including R1224yd(Z), R1233zd(E), R1234yf, R1234ze(E), R1234ze(Z), R1243zf and R1336mzz(Z), are evaluated and compared against R245fa as server coolant. For the HPAAC system, beginning with the development of energy and economic models, the performance is analyzed through both a parametric study and optimization using the coefficient of performance (COP), energy saving ratio (ESR), payback period (PBP) and net present value (NPV) as thermo-economic indicators. Using a standard vapor compression cooling system as a benchmark, the results indicate that with the evaporation temperature between 50°C and 70°C and the subcooling degree ranging from 5°C to 15°C, R1233zd(E) with moderate compressor suction pressure and pressure ratio is the best refrigerant for the HPAAC system while R1234yf performs the worst. More importantly, R1233zd(E) is also superior to R245fa based on thermo-economic performance, especially under work conditions with relatively lower evaporation temperature as well as subcooling degree. Under the given working conditions, the overall COP, ESR, NPV, and PBP of R1233zd(E) HPAAC with optimum subcooling degree range from 4.99 to 11.27, 25.53 to 64.59, 1.13 to 4.10 × 107 CNY and 5.77 to 2.22 years, respectively. Besides, the thermo-economic performance of R1233zd(E) HPAAC under optimum working conditions in terms of subcooling degree varying with the evaporation temperature is also investigated. [ABSTRACT FROM AUTHOR]

Over the past decades, combined heat and power production (CHP) has proven itself to be an efficient means of meeting both heat and power demands. However, high efficiency can be achieved with CHP plants when the heat load is sufficient, while lower-priority CHP plants must deal with the excess heat associated with power generation. This excess heat can be used for district cooling with absorption chillers. Although the absorption chiller is an efficient technology for using excess heat for cooling generation, its efficiency is very sensitive to driving hot water temperature. This paper provides a detailed analysis of how cooling generation in CHP plants using absorption chillers affects power generation and primary energy consumption. This study is based on the operational parameters of the Mustamäe CHP plant (Tallinn, Estonia) and the cooling demand of the Tehnopol science and business campus and proposes a sufficient cooling production capacity based on the estimation of the campus' cooling demand. Additional cooling production opportunities to meet district cooling demand are discussed and compared in this paper in terms of primary energy savings and economic profit. The study finds that for the effective use of CHP excess heat and efficient cooling production, the use of an 0.8 MW absorption cooler and 11.6 MW heat pumps is recommended. This system would use 1.9 times less primary energy for cooling generation than local cooling. [ABSTRACT FROM AUTHOR]

This research paper examined the operational performance and greenhouse gas (GHG) emissions of an existing gas treatment plant. Extensive data collection and analysis were undertaken to assess energy consumption and emissions and identify major emitter units. A GHG emission inventory was developed, and a benchmarking analysis was conducted. The gap analysis revealed excessive emissions, leading to the identification of potential GHG abatement alternatives for the turbo compressor and stabilizer heater. Technical feasibility assessments and economic evaluations were performed for the implementation of waste heat recovery systems, specifically an absorption chiller and a hot oil-driven re-boiler. The results demonstrated significant energy savings, emission reduction, and positive financial returns. The economic evaluation of the abatement opportunities revealed an estimated annual savings of $229,287 US with a simple payback period (SPBP) of 2.96 years and an internal rate of return (IRR) of 32%/year for the absorption chiller. The re-boiler heat system showed an estimated annual savings of $209,456 US with an SPBP of 5.14 years and an IRR of 14%/year. The total investment for both opportunities amounted to $1,755,773 US, with a total annual savings of $438,743 US. The combined SPBP for the opportunities was 4 years, with an IRR of 21%/year. Sensitivity analyses demonstrated the absorption chiller's financial viability, while the hot oil-driven re-boiler opportunity proved more sensitive to variations in investment costs and savings. Therefore, it is recommended to implement both opportunities together. [ABSTRACT FROM AUTHOR]

Solar heating and cooling (SHC) systems are currently attracting attention, especially in times of increasing energy prices and supply crises. In times of lower energy prices, absorption SHC systems were not competitive to compression cooling supported by photovoltaic (PV) modules due to the high investment costs and total energy efficiency. This paper aims to discuss the current changes in energy supply and energy prices in terms of the feasibility of the application of a small absorption SHC system in a mild Mediterranean climate. The existing hospital complex restaurant SHC system with evacuated tube solar collectors and a small single-stage absorption chiller was used as a reference system for extended analysis. Dynamic simulation models based on solar thermal collectors, PV modules, absorption chillers and air-to-water heat pumps were developed for reliable research and system comparison. The results showed that primary energy consumption in SHC systems designed to cover base energy load strongly depends on the additional energy source, e.g., boiler or heat pump. Absorption SHC systems can be price competitive to air-to-water heat pump (AWHP) systems with PV collectors only in the case of reduced investment costs and increased electricity price. To reach acceptable economic viability of the absorption SHC system, investment price should be at least equal to or lower than a comparable AWHP system. [ABSTRACT FROM AUTHOR]

The solar absorption-subcooled compression hybrid cooling system (SASCHCS) is tech-economically feasible for high-rise buildings. Since such a system operates with no auxiliary heat source, the performance coupling of its absorption subsystem and solar collectors is sensitive to the variation of hot water flow rate. In this regard, the relationship of system performance and hot water flow rate is required to be clarified exactly. Therefore, this paper aims to illustrate the effect mechanism of hot water flow rate and to propose the corresponding decision criterion. The case study is based on a typical high-rise office building in subtropical Guangzhou. The daily working process of this system with different hot water flow rates is simulated and analyzed. Subsequently, the useful heat of collectors and cooling capacity of the absorption subsystem with the hot water flow rate is discussed in detail. The results show that the SASCHCS operates with hot water temperatures ranging from 60 °C to 90 °C. The energy saving increases with the rise of hot water flow rate, but such variation tends to be flat for the excessively high flow rate. As the collector flow rate increases from 1 m3/h to 10 m3/h, the daily energy saving improves by 21% in August. Similarly, the daily energy saving increases by 37.5% as generator hot water flow rate increases from 1 m3/h to 10 m3/h. In addition, the collector flow rate of 3.6 m3/h (13.33 (kg/m2 h)) and the generator flow rate of 5.2 m3/h (19.26 (kg/m2 h)) are optimal for the annual operation, with considering power consumption of water pumps. This paper is helpful for the improvement of SASCHCS operating performance. [ABSTRACT FROM AUTHOR]

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

The electricity required for air conditioning is soaring worldwide. Absorption chillers represent an alternative to classical vapor compression systems, using heat instead of electricity. However, absorption chillers powered by renewable geothermal heat have received little attention so far. This paper introduces a system using a hot geothermal fluid (typically in the range of 80–110 °C) to produce cooling through a single-effect absorption chiller, and Domestic Hot Water (DHW) through a heat exchanger. It considers a hotel located in Martinique, a French Caribbean island. The electric consumption of every subsystem has been thoroughly estimated. The originality of this paper is twice: i) the system is modelled in TRNSYS software considering dynamic conditions, ii) the system undergoes surrogate modelling and multi-objective optimization to minimize both the cost and the CO 2 content of the delivered thermal energy. Several scenarios are considered, depending upon the geothermal temperature, mass flow rate, well remoteness, and demand size. The studied system appears to be systematically more expensive than a combination of a classical vapor compression chiller and a boiler for DHW. However, it can significantly decrease the CO 2 content of the provided energy, especially in an island where most electricity is generated from fossil fuels. The proximity of the geothermal well and the use of the warm water leaving the absorption generator (here for DHW production) appear to be key factors for system relevance, along with a hotter geothermal fluid (e.g., 110 °C instead of 80 °C). • A geothermal absorption chiller in tropical climate is modelled. • The influence of design parameters on electricity consumption is investigated. • The system undergoes multi-objective optimization. • The well proximity and geothermal temperature are keys to the system relevance. [ABSTRACT FROM AUTHOR]

The solar absorption-subcooled compression hybrid cooling system (SASCHCS), in which the cooling capacity of absorption subsystem serves as the subcooling power of compression subsystem, is energy-efficient for high-rise buildings. Because the existing design guideline of system is based on the conventional exergy theory and the advanced exergy analysis of absorption and vapor compression chillers is from the endogenous avoidable portion instead of the sum of the avoidable exergy destruction, it is incapable to design the SASCHCS exactly by such findings. As a result, the systematical advanced exergy analysis of SASCHCS is performed. The advanced exergy model of facilities is built at first. Subsequently, various exergy destructions for different conditions are analyzed. Finally, the improvement potential of components is assessed based on the sum of the avoidable exergy destruction, defined as the sum of endogenous avoidable portion of k-th component and exogenous one of remaining components led by irreversibilities of k-th component. Though the compressor concentrates the most exergy destruction of SASCHCS, 62% of its exogenous exergy destruction is caused by the irreversibilities of the condenser of the compression subsystem, making the condenser the most important component of SASCHCS. The paper is helpful to promote the design of SASCHCS. [ABSTRACT FROM AUTHOR]

As a novel solar cooling facility in the building with many floors, the solar absorption-subcooled compression hybrid cooling system (SASCHCS) is not evaluated economically and environmentally. Consequently, the paper mainly contributes to the above-mentioned study to show the potential of the SASCHCS. The evaluation, performing by the dynamic simulation based on the monthly typical cooling demand and meteorological data, is by the comparison of SASCHCS and the solar PV cooling which is thought to be the most economical solution recently. It is found that the SASCHCS is economically better than the solar PV cooling though the saving of CO2 emission in the SASCHCS is less. Besides, the SASCHCS becomes more economical and attractive as the performance of its compression subsystem is poor. The payback period of the SASCHCS drops to 17.6 yr when the performance of compression subsystem comes down by 20%. The paper is helpful to promote the application of the SASCHCS. [ABSTRACT FROM AUTHOR]

Refrigeration systems claim increasing research attention as the climate crisis intensifies. One of the most well-established viable and feasible solutions is solar cooling, as the necessary cooling energy is produced by exploiting the available solar irradiance. The utilization of solar thermal energy to produce cooling energy by absorption chillers fed by a driving heat source (such as solar energy) to produce cooling power. Existing works in the literature present mainly case studies and simulations for small-scale systems (less than 50 kWc). The case study presented investigates the performance of a single-effect 316 kWc absorption chiller under different renewable-only driving heat source scenarios (solar-driven, biomass-driven, and a hybrid approach). The results indicate a significantly advantageous performance in combined heat generation (solar field and biomass boiler connected in series) compared to the scenarios of biomass or solar energy as a sole heat source. Moreover, an absorption chiller's economic indicators appear more fetching than a centrifugal electric chiller of the same capacity, as the payback period is significantly reduced. The Net Present Value (N.P.V. – over 75% greater in the case of absorption chiller compared to the centrifugal electrical chiller) and Return on Investment (R.O.I.) values are increased in the case of the absorption chiller option (18.03% against 15.24% of the centrifugal electrical chiller). The system described in this paper operates in Eastern Macedonia and Thrace, Greece, and is part of one of the largest self-sufficient energy communities. The case study presented is the first attempt at performance evaluation of a large-scale (more than 250 kWc) cooling system operating in a local energy community. [ABSTRACT FROM AUTHOR]

This paper presents a detailed exergetic analysis of a novel high-temperature Solar Assisted Combined Cycle (SACC) power plant. The system includes a solar field consisting of innovative high-temperature flat plate evacuated solar thermal collectors, a double stage LiBr-H2O absorption chiller, pumps, heat exchangers, storage tanks, mixers, diverters, controllers and a simple single-pressure Combined Cycle (CC) power plant. Here, a high temperature solar cooling system is coupled with a conventional combined cycle, in order to pre-cool gas turbine inlet air in order to enhance system efficiency and electrical capacity. In this paper, the system is analyzed from an exergetic point of view, on the basis of an energy-economic model presented in a recent work, where the obtained main results show that SACC exhibits a higher electrical production and efficiency with respect to the conventional CC. The system performance is evaluated by a dynamic simulation, where detailed simulation models are implemented for all the components included in the system. In addition, for all the components and for the system as whole, energy and exergy balances are implemented in order to calculate the magnitude of the irreversibilities within the system. In fact, exergy analysis is used in order to assess: exergy destructions and exergetic efficiencies. Such parameters are used in order to evaluate the magnitude of the irreversibilities in the system and to identify the sources of such irreversibilities. Exergetic efficiencies and exergy destructions are dynamically calculated for the 1-year operation of the system. Similarly, exergetic results are also integrated on weekly and yearly bases in order to evaluate the corresponding irreversibilities. The results showed that the components of the Joule cycle (combustor, turbine and compressor) are the major sources of irreversibilities. System overall exergetic efficiency was around 48%. Average weekly solar collector exergetic efficiency ranged from 6.5% to 14.5%, significantly increasing during the summer season. Conversely, absorption chiller exergy efficiency varies from 7.7% to 20.2%, being higher during the winter season. Combustor exergy efficiency is stably close to 68%, whereas the exergy efficiencies of the remaining components are higher than 80%. [ABSTRACT FROM AUTHOR]

In this paper, the coupling of a high temperature heat pump with a combined cooling, heat, and power system is investigated. The plant converts the input energy source (natural gas) into electricity and useful thermal energy by means of a cogenerator. Part of the thermal energy feeds an absorption chiller that produces the cooling energy to satisfy the cooling load of an existing industrial building located in northern Italy. The heat pump enhances the low temperature heat from the condenser and absorber of the absorption chiller to high temperature heat to integrate the hot water produced by the cogenerator. The energy performance of the entire plant is analyzed by means of steady-state simulations at both fixed conditions and on an annual operation to meet the heating, cooling, and electric needs of the building varying different parameters and compared to traditional systems for energy production. As the main results, the integrated system provides flexibility and achieves valuable energy performances, in the range of a few tens of percent with respect to benchmark energy production systems. [ABSTRACT FROM AUTHOR]

In hot and humid areas with high solar radiation intensity, the use of air conditioning systems on the basis of desiccant materials such as solar desiccant cooling systems with a view to reducing energy consumption and economic saving can be a good alternative to conventional air conditioning units. In this paper, in order to offer a cooling load of a sample space in the city of Bandar Abbas, which has a high latent load and high radiation intensity, solar absorption cooling cycle has been considered as the base cycle, and two absorption cooling cycles were designed for comparison. Then the three cycles were modeled in the TRNSYS software, studied technically and economically, and at the end the best cycle has been selected. In terms of current energy prices, application of solar energy in Iran is not economically feasible, so the solar absorption refrigeration cycle has been considered as the basic system for the cycle's comparison. Modeling of the expressed cycles was done in TRNSYS software. The basic cycle has been composed of two main parts of cooling by absorption chillers and providing the required heat supply by the solar collector, and also two desiccant dehumidification cycles have been added by a desiccant dehumidification system. In the economic analysis of the three systems, the costs estimation during lifetime (LCC) method also has been used. As a result of this modeling and due to the Act to amend energy prices, the cooling system with the help of desiccant wheel and using returned water of chiller's generator as the regeneration source, with an annual energy saving of about 29.1%, 29.1% (1,371,980 m3) of natural gas consumption has been saved and the amount of 18/15% (156,667$) cost savings over 20 years compared to the base period, has been selected as the most efficient cooling system. [ABSTRACT FROM AUTHOR]

The paper proposes a diesel engine-based trigeneration system using a thermal storage for applications with simultaneous heating, cooling and power demand and where grid electricity is not available. A thermodynamic analysis is presented for the proposed trigeneration systems considering an 815 kWe diesel generator (DG) as a prime mover. Two configurations are considered. One configuration includes absorption chiller with an auxiliary hot water heater, while the other has a compression chiller in addition to the absorption chiller and water heater. Methodology of integrating a compression chiller is also presented. An analysis of both these options on primary energy savings basis for the considered DG shows that integrating a thermal storage and compression chiller enhances trigeneration performance. Without the compression chiller, the trigeneration system efficiency improves from 46% to 52% while with compression chiller integration, the improvement is much more from 46% to 72% when the power load decreases from 100% to 25%. [ABSTRACT FROM PUBLISHER]

• A new model of a thermosiphon desorber under sub-atmosphere was established. • The known correlations were checked to the validities of the model. • The heat transfer and mass flow rate behaviors have been investigated in the model. The thermosiphon desorber or bubble pump is advantageous in absorption cooling devices, since the processes of refrigerant desorption and solution pumping is combined in one hermetical unit. This supersedes the necessity of a mechanical solution pump. In the application with NH 3 /H 2 O the thermosiphon desorber typically operates at a pressure of around 15 bar with a liquid vapor density ratio in the range of 102, which is in a well-known regime of two phase flow. Nevertheless, for the application of thermosiphon desorbers in H 2 O/LiBr absorption chillers, which are commonly operated at a pressure below 0.1 bar with the liquid vapor density ratio in the range of 104, there is a lack of heat transfer correlations for two-phase flow. First attempts to fill this gap of flow boiling heat transfer correlations in the thermosiphon desorber at sub-atmospheric pressures is presented in this paper. A model is formed by solving simultaneously the mass, energy, and momentum equations. The well-known correlations for predicting single-phase and two-phase flow heat transfer coefficient and frictional pressure drop have been reviewed to find a possibility for applying them to the thermosiphon desorber. The mass flow rate and heat transfer behavior with the different flow length of the riser tube and with changing the pressure has been theoretically studied in the model. For verification, the model has been compared to experimental data using pure water. This will be presented in the second part of the paper. [ABSTRACT FROM AUTHOR]

In this paper, the effects of various compressor inlet air cooling methods to increase the performance of Shahid Hashemi-Nezhad gas turbines refinery were investigated. These methods included media, fogging, and absorption chillers as common inlet air cooling methods and pressure drop station as novel cooling method. By using the exergy, environmental, and economic analysis, the best method for compressor inlet air cooling was selected. Based on the results, the absorption chiller system had the highest compressor inlet air temperature drop and increased the thermal and exergy efficiencies of cycle by about 2.5 and 3%, respectively, in hot season. Using absorption chiller, pressure drop station, fogging, and media had further reduction in CO2 and CO than simple gas turbine, respectively. Finally based on the net present value and internal rate of return coefficients, the pressure drop station method is the most economically feasible option. [ABSTRACT FROM AUTHOR]

Highlights • Exergoeconomic off-design model is built and the maximum deviation is less than 9% • Design of system in low-rise building relies on working condition strongly. • Component with large size is attractive for system in high-rise building. • Design for different decision variables is usually different for low-rise building. • Design for different decision variables is usually similar for high-rise building. Abstract The solar absorption-subcooled compression hybrid cooling system (SASCHCS) is subjected to the off-design operation due to the variation of solar irradiance and cooling load. Therefore, the recent design based on the specific condition is difficult to make the system cost-effective in the entire working range. This paper mainly deals with the exergoeconomic design criterion of hybrid system based on the variable working conditions to access the trade-off of investment cost and performance in the whole working condition. The SASCHCS employed in the low-rise building and the high-rise building is considered. Besides, twenty-four cases with different important parameters, i.e., the size of absorption subsystem, condenser and evaporator of compression subsystem as well as isentropic efficiency of compressor, are analyzed in detail. The product cost flow rate and relative cost difference are taken as the decision variables. The exergoeconomic off-design model is developed at first. Subsequently, the decision variables for different temperatures of hot water and cooling water as well as load level is obtained and analyzed. It is found that the difference of the design guideline for the system used in the low-rise building and high-rise building lies in the size of absorption subsystem and condenser, i.e., the lowest scale of absorption chiller is appropriate when the temperature of hot water is less than 75 °C for the facility applied in the low-rise building, but the largest size of absorption subsystem is attractive in the entire range of hot water temperature as the hybrid system is used in the high-rise building. This paper is positive for the development of design theory and helpful to design the cost-effective SASCHCS under the entire working range. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the various optimized generators for H 2 O/LiBr absorption chiller with multi-heat sources are discussed. While the previous optimization has been mainly conducted for a single element, the integrated generation system including high/low temperature generator and waste heat recovery generator is optimized in this paper. A practical modeling method is proposed for the high/low temperature generator and it has been verified by comparing with experimental results. Meta-models for the volume and the generation rate are built with kriging method, and the generators are optimized by multi-objective optimization technique using the meta-models. The total volume is minimized and the total generation rate is maximized according to five design variables of the generators. It is found that from the optimization process the total volume is decreased by 59.06% and the total generation rate is increased by 31.46% compared to the baseline point. It is concluded that the contribution of the waste heat recovery generator and the high temperature generator are dominant for the total volume reduction and the total generation rate improvement, respectively. Moreover, the effects of the key variables on the performance of each generator are analyzed according to the optimization of the integrated generation system. Highlights • A practical modeling method is proposed for generators with multi-heat sources for tri-generation systems application. • The generators are optimized by multi-objective optimization technique using the meta-models. • The total volume is decreased by 59.06% while total generation rate is increased by 31.46% by the optimization. • The waste heat recovery generator is dominant for the total volume reduction. • The high temperature generator is dominant for the total generation rate improvement. [ABSTRACT FROM AUTHOR]

Copyright of Ingenius, Revista Ciencia y Tecnología is the property of Universidad Politecnica Salesiana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Over the past decades, combined heat and power production (CHP) has proven itself to be an efficient means of meeting both heat and power demands. However, high efficiency can be achieved with CHP plants when the heat load is sufficient, while lower-priority CHP plants must deal with the excess heat associated with power generation. This excess heat can be used for district cooling with absorption chillers. Although the absorption chiller is an efficient technology for using excess heat for cooling generation, its efficiency is very sensitive to driving hot water temperature. This paper provides a detailed analysis of how cooling generation in CHP plants using absorption chillers affects power generation and primary energy consumption. This study is based on the operational parameters of the Mustamäe CHP plant (Tallinn, Estonia) and the cooling demand of the Tehnopol science and business campus and proposes a sufficient cooling production capacity based on the estimation of the campus’ cooling demand. Additional cooling production opportunities to meet district cooling demand are discussed and compared in this paper in terms of primary energy savings and economic profit. The study finds that for the effective use of CHP excess heat and efficient cooling production, the use of an 0.8 MW absorption cooler and 11.6 MW heat pumps is recommended. This system would use 1.9 times less primary energy for cooling generation than local cooling.

The building sector has great potential for contributing to the 2030 EU goals of decreasing greenhouse gas emissions and increasing production from renewable sources. This is even more important considering the increasing cooling energy needs. Among the available technologies, solar cooling (SC) represents a good alternative to traditional electric chillers. However, its use in residential buildings is still limited. The aim of this paper is to analyse the potential of solar cooling system in multi-family buildings. A dynamic model of a complete SC system with auxiliary components was developed in TRNSYS to meet the energy demand of a representative nearly zero energy multi-family building in Italy. The performance of different system design alternatives was analysed in eight different climates with special focus on energy storages. The results show how solar cooling should be optimally designed and provide quantification of achievable renewable energy ratios and related costs in the different climates. • Weather is a determining factor for the design of Solar Cooling (SC) systems. • Solar Cooling represent a valuable alternative for nZEB space cooling. • Dynamic modelling for optimization of thermal storage is crucial to ensure SC performance. • Global design choices should include cost-optimal analysis. • A best design scenario has been identified economically and energetically. [ABSTRACT FROM AUTHOR]

This paper proposes the first application of a split-range control technique on a concentrating solar collector to improve an absorption plant production. Solar absorption plants have solar power availability in phase with cooling demand under design conditions. Thus, it is a powerful cooling technology in the context of renewable energy and energy efficiency. These plants need control systems to cope with solar irradiance intermittency, reject irradiation disturbances, manage fossil fuels backup systems and dump closed-loop thermal-hydraulic oscillations. In this work, control techniques are proposed and simulated in an absorption plant in Spain. The plant consists of a concentrating Fresnel solar collector connected to an absorption chiller. The objectives are to operate with 100% renewable solar energy and avoid safety defocus events while reducing temperature oscillations and control actuators effort. Firstly, the current available plant controllers are defined, then two modifications are proposed. The first modification is a split-range controller capable of manipulating both flow and defocus of the Fresnel collector, the second modification is a PI controller to substitute the original chiller on-off controller. The results compare, through validated models, the different control systems and indicate that using both proposed controllers reduces 94% of the sum of actuators effort and 43% of the integral of absolute set-point tracking error compared to the plant's factory pre-set controllers. The suggested controllers increase 66% of energy production and 63% of exergy production. Besides, the split-range technique can be extended to any concentrating solar collector control. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • LAES discharges as heat almost 70% of the total heat from the compression phase. • Waste heat is re-used in ORC and/or absorption chillers (ABS). • ORC integration improves the round trip efficiency by 20%. • ABS slightly reduces the specific consumption with almost no effect on round trip efficiency. • In trigenerative mode, LAES + ORC + ABS improves the round trip efficiency by 30%. Abstract In this paper, the potential of improving the round trip efficiency of Liquid Air Energy Storage was investigated through modelling and simulations using the numerical software EES-Engineering Equation Solver. Liquid Air Energy Storage is a novel energy storage concept whose performance is actually limited both by the inefficiencies of the charging (liquefaction cycle) and discharging (regasification and expansion) leading to a low value of round trip efficiency when compared to other energy storage solutions. In order to further improve the round trip efficiency, the opportunity to recover the waste heat released during the compression has been considered in this paper. Different integrated energy systems consisting Organic Rankine Cycle and/or Absorption Chiller were compared against a stand-alone Liquid Air Energy Storage used as a baseline. The integrated systems are compared in terms of different performance indices such as electric power output , ORC efficiency , round trip and overall efficiency of the stand-alone and integrated systems and utilization factor of the waste heat recovery systems. The results show that a tight integration between Liquid Air Energy Storage and Organic Rankine Cycle allows to significantly improve the round trip efficiency (up to 20%). Although the introduction of the absorption chiller decreases the specific consumption, the round trip efficiency is not improved due to the lower quality of waste heat available at the LAES discharge phase. The most remarkable results are achieved when the LAES is operated in trigenerative configuration: the introduction of both Organic Rankine Cycle and Absorption Chiller in combination with Liquid Air Energy Storage was found to improve the round trip efficiency by 30% due to a better utilization of the available waste heat. [ABSTRACT FROM AUTHOR]

An optimized design for a solar absorption-subcooled compression hybrid cooling system used in low-rise buildings is complicated because of the overall considerations involving increases in investment costs and energy savings, which are associated with an increase in the size of the absorption subsystem. To this end, this paper’s main contribution lies in its exergoeconomic-optimized design of a solar absorption-subcooled compression hybrid cooling system employed in low-rise buildings for different design cases. In this paper, not only the minimum product-cost flow rate but also the lowest relative cost difference is taken as the objective function owing to the notable changes in fuel cost flow rates. The results of the exergoeconomic optimization shows that the actual cooling capacity of the absorption subsystem should not be designed based only on the maximum collector area. Instead, the actual installed collector area should be determined by the optimal cooling capacity of the absorption subsystem. It was also found that the optimal cooling capacity of the absorption subsystem strongly depends on solar irradiance and cooling demands. In addition, optimal sizes for the absorption subsystem should be designed according to the different minimum product cost flow rates or the lowest relative cost difference, and this difference is sensitive to the local mean solar irradiance but weakly relies on the cooling demand. The paper is helpful in its cost-effective design for a solar absorption-subcooled compression hybrid cooling system used in low-rise buildings. [ABSTRACT FROM AUTHOR]

In hot coastal regions where fresh water is scarce, absorption chillers driven by industrial waste heat and cooled by seawater are suitable to achieve cooling demands, and it contributes to improving energy efficiency and reducing CO 2 emissions. However, seawater cooling strategy is a trade-off between performance and cost for practical applications, and there are few direct seawater-cooled absorption chillers. In addition, the integration of absorption chillers into a waste heat utilization network is often not well planned, and thus the waste heat is usually not used efficiently. This paper presents the direct seawater cooling strategy for the absorption chiller in terms of high performance and low cost by comparing different seawater cooling strategies numerically and experientially. To realize efficient energy utilization, an existing waste heat utilization network is analyzed graphically based on pinch method, and the available heat for absorption chillers is obtained by the position of the pinch point. According to the available heat, the direct seawater-cooled absorption chiller with a designed cooling capacity of 4200 kW is developed by using titanium tubes, anticorrosive paints and rubber covers to construct the corrosion-resistant condenser and absorber. The site testing results show an average cooling capacity of 3043 kW and an average COP of 0.77 of the absorption chiller when the temperatures of the hot water, seawater and chilled water varies from 98.7 °C to 80.7 °C, from 30.2 °C to 34.2 °C, and from 14.4 °C to 8.6 °C, respectively. Due to the integration, the energy and exergy efficiencies of the waste heat utilization network is improved by 55.9% and 86.1%, respectively. The application demonstrates that the direct seawater-cooled absorption chiller holds the promise for waste heat utilization in coastal regions. • Different seawater cooling strategies for an absorption chiller are compared. • Direct seawater cooled absorption chiller of 4200 kW is developed. • Titanium tubes, anticorrosive paints and rubber covers are employed for anti-corrosion. • The direct seawater cooled absorption chiller is integrated into a waste heat utilization network. • The energy and exergy efficiencies of the network is improved by 55.9% and 86.1%. [ABSTRACT FROM AUTHOR]

The main concept of combined cooling, heating and power (CCHP) generation systems, which produce three energy commodities simultaneously, is based on using absorption chillers fired by the waste heat from the engine instead of electricity for air conditioning or for any other cooling purpose where electricity could have been used. Proper selection and design of the heat recovery system plays an important and challenging role in achieving this goal. Minimum exergy destruction in the waste heat recovery process increases the thermal performance. This paper introduces the modulating flow cascade heat recovery system (CHRS) to improve the coefficient of performance (COP) of the absorption chiller at part load engine operation. Due to this novel feature, it is possible to obtain a percentage increase of over 13% in COP at 50% engine load compared to the conventional fixed flow waste heat recovery. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel Solar Assisted Combined Cycle power plant. The system includes a solar loop equipped with a double stage absorption chiller driven by high-temperature high-vacuum non-concentrating flat-plate solar thermal collectors. The solar loop is coupled to a single-pressure Combined Cycle power plant. The cooling energy produced by the absorption chiller is used to cool gas turbine inlet air, aiming at enhancing system efficiency and electrical capacity. This Solar Assisted Combined Cycle arrangement is analysed through a dynamic system simulation and a thermoeconomic analysis is also performed aiming at determining the optimal set of design and operating parameters. The paper has the objective to prove the technical, energetic and economic feasibility of this technology, especially for hot and dry areas, with respect to other alternative air cooling configurations. In addition, solar collectors operating temperatures are high enough to drive a two stage absorption chiller, showing a Coefficient of Performance roughly two times higher than the one of a conventional single stage absorption chiller. This original configuration was numerically analysed in TRNSYS environment, developing a suitable dynamic simulation model in order to predict system performances. Suitable dynamic models are implemented for all the components included in the system. Special attention is also paid to the design of novel control strategies aiming at maximizing the utilization of solar energy for cooling purposes. In particular, a special control strategy managing cooling water flow is implemented in order to limit as much as possible water condensation within the cooling coil. The simulation also includes a detailed thermoeconomic model which accurately evaluates system capital and operating costs as a function of design and operating parameters. The simulations results show that a very high thermal efficiency of solar collectors, on average equal to 34%, is achieved. Results from the economic point of view were also satisfactory. In fact, the pay back period was about 8 years in the best case. Finally, in order to analyse the effects of the variation of the main design parameters, a parametric analysis is also presented. Such analysis shows that high solar radiation and low ambient humidity are crucial in order to achieve acceptable economic profitability indexes. [ABSTRACT FROM AUTHOR]

Many installed solar thermally driven cooling systems suffer from high auxiliary electric energy consumption which makes them not more efficient than conventional compression cooling systems. A main reason for this is the use of non-efficient controls with constant set points that do not allow a chiller power modulation at partial-load and therefore lead to unnecessary high power consumption of the parasitics. The aims of this paper are to present a method to control efficiently solar thermally driven chillers, to demonstrate experimentally its applicability and to quantify the benefits. It has been shown that the cooling capacity of a diffusion absorption chiller can be modulated very effectively by adjusting both the temperature and the flow rate of the cooling water. With the developed approach and the use of optimization algorithms, both the temperature and the flow rate can be controlled simultaneously in a way that the cooling load is matched and the electricity consumption is minimized. Depending on the weather and operating conditions, electricity savings between 20% and 60% can be achieved compared to other tested control approaches. The highest savings are obtained when the chiller is operated at partial load. The presented method is not restricted to solar cooling systems and can also be applied to other conventional heating ventilation and air conditioning (HVAC) systems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Absorption cooling technology is an environmentally friendly method to generate continuous chilled water making use of multiple thermal sources, such as waste heat and renewable thermal energy. In this study, two absorption chillers (nominal capacity of 400 kW) with series and parallel connections are evaluated. To research the ideal configuration of chillers after thermodynamic analysis, the structures of the chillers are optimized using the particle swarm optimization algorithm by considering the heat transfer area (HTA), exergy efficiency and total annual cost as single-objective functions. The impact of temperature differences between external and internal flows, heat exchanger efficiencies and the solution allocation ratio is estimated. The optimized HTA, coefficient of performance, exergy efficiency and total annual cost are 149.0 m2, 1.56, 29.44% and $229 119 for the series-connected chiller, and 146.7 m2, 1.59, 31.45% and $234 562 for the parallel-connected type, respectively. Under the lowest HTA condition, compared with the reference simulation results, the energy and exergy performances are improved, while the annual total cost is higher. The annual total cost is highest when maximizing the exergy efficiency, which is attributed to the increase in the HTA. The operating cost accounts for 27.42% (series type) and 26.54% (parallel type) when the annual cost is the lowest. [ABSTRACT FROM AUTHOR]

As a novel solar cooling facility in the building with many floors, the solar absorption-subcooled compression hybrid cooling system (SASCHCS) is not evaluated economically and environmentally. Consequently, the paper mainly contributes to the above-mentioned study to show the potential of the SASCHCS. The evaluation, performing by the dynamic simulation based on the monthly typical cooling demand and meteorological data, is by the comparison of SASCHCS and the solar PV cooling which is thought to be the most economical solution recently. It is found that the SASCHCS is economically better than the solar PV cooling though the saving of CO2 emission in the SASCHCS is less. Besides, the SASCHCS becomes more economical and attractive as the performance of its compression subsystem is poor. The payback period of the SASCHCS drops to 17.6 yr when the performance of compression subsystem comes down by 20%. The paper is helpful to promote the application of the SASCHCS.

A simplified transient dynamic model for a single-effect absorption refrigeration chiller using LiBr/H2O as the working pair is developed in this paper. The model contains a series of sub-models presenting the components composing the chiller. The development of the sub-models of the four main components (i.e. generator, condenser, evaporator, and absorber), where the solution or refrigerant goes through phase change with complex heat and mass transfer progress, is based on the conservation of mass and energy, by means of dynamic modeling approaches. The throttling devices, solution pump, and solution heat exchanger (SHE) adopt quasi-steady models because their thermal inertia is much smaller compared with the main components. The system model proposed in this study is finally simplified and expressed in the form of state space matrix, which enhances the model portability and computational efficiency. Two approaches are carried out to verify the model accuracy at the end of the paper, static comparison between the steady simulation results and the design parameters under the on-design condition, the dynamic comparison between the simulation results and experimental data under the same inputs. Both comparison results show the model accuracy.

Innovative hybrid source for electricity, cooling and desalinated water production based on a mixed fossil fuel/solar energy supply, equipped with triple-component chiller configuration, has been presented in the paper. The system was erected and recently commissioned in King Abdulaziz City for Science and Technology (KACST) in Kingdom of Saudi Arabia to operate as a working laboratory supplying media to adjacent buildings of the Solar Village complex. In the Arabian Gulf region, increased demand, especially for cooling and desalinated water, as well as fluctuating availability of electricity from the grid in summer period is visible, what makes such a stand-alone installation operation justified especially in remote areas. Abundant availability of intermittent solar energy correlated with cooling demand led to development of novel triple-component chiller configuration consisting of absorption, adsorption and compressor chiller. Two Diesel internal combustion engines had been selected to supply electricity and heating when solar energy is not available. Paper presents results of installation commissioning, during which the performance of the system for three different operating scenarios was assessed. Maximum efficiency was achieved for maximum renewable energy production option reaching 324.91% with renewable share at a level of 89.99%. For the maximum cooling capacity production, the efficiency of the system was 124.89% with 18.6% share of renewable energy. The lowest efficiency, of 93.09%, system obtained for the night scenario. • Novel, patented triple-component configuration of chillers has been presented. • Hybrid source for energy and desalinated water production has been commissioned. • Solar panels integration enabled maintaining cooling and distillate production. • Efficiency in max. Renewable energy scenario has reached 325% during commissioning. • Renewable energy share has reached 90% during commissioning. [ABSTRACT FROM AUTHOR]

With non-renewable energy sources depleting quickly, solar energy could prove a viable option owing to its abundance and eco-friendliness. Modeling and simulation of a solar energy-driven single-stage absorption chiller was carried out using the transient simulation software 'TRNSYS' . An evacuated tube collector coupled with an insulated tank served as heat source for the absorption chiller. Experiments were conducted to evaluate the efficiency parameters of the collector as well as the loss coefficient for the storage tank. These parameters along with standard chiller performance data were used to model the system. The influence of climatic conditions, storage capacity and various control schemes with and without auxiliary heating on the output of the system is analyzed and presented in the paper. [ABSTRACT FROM AUTHOR]

The lower coefficient of performance and higher risk of crystallization in the higher surrounding temperature is the primary disadvantage of air cooled lithium bromide–water double effect absorption chiller. Since the coefficient of performance and risk of crystallization strongly depend on the heat load ratio of generator, the appropriate heat load ratio of generator can improve the performance as the surrounding temperature is higher. The paper mainly deals with the appropriate heat load ratio of generator of air cooled lithium bromide–water double effect absorption chiller. Four type systems named series, pre-parallel, rear parallel and reverse parallel flow configuration were considered. The corresponding parametric model was developed to analyze the comprehensive effect of heat load ratio of generator on the coefficient of performance and risk of crystallization. It was found that the coefficient of performance goes up linearly with the decrease of heat load ratio of generator. Simultaneously, the risk of crystallization also rises slowly at first but increases fast finally. Consequently, the appropriate heat load ratio of generator for the series and pre-parallel flow type systems is suggested to be 0.02 greater than the minimum heat load ratio of generator and that for the rear parallel and reverse parallel flow chillers should be 0.01 higher than the minimum heat load ratio of generator. Besides, the changes of minimum heat load ratio of generator for different type systems with the working condition were analyzed and compared. It was found that the minimum heat load ratio of generator goes up with the increase of temperature of high pressure generator as well as surrounding temperature and it goes down with the rise of evaporator temperature and effectiveness of high temperature heat exchanger. The dependence of minimum heat load ratio of generator for the series and rear parallel flow system on the effectiveness of low temperature heat exchanger is weak. While the minimum heat load ratio of generator of pre-parallel and reverse parallel flow chiller rises with the increase of effectiveness of low temperature heat exchanger. The minimum heat load ratio of generator of reverse parallel flow configuration is independent upon the distribution ratio. The minimum heat load ratio of generator of pre-parallel flow system goes up fast with the rise of distribution ratio when the distribution ratio exceeds to 0.55. But the minimum heat load ratio of generator of rear parallel flow configuration just rises slightly with the increase of distribution ratio as the distribution is greater than 0.5. The paper is helpful to the development and performance improvement of air cooled lithium bromide–water double effect absorption chiller. [ABSTRACT FROM AUTHOR]

Even under the powerful thrust of 20–20–20 measures, solar thermal systems are experiencing a slow-down in their development in most EU countries. One reason is their traditional confinement to sanitary hot water (SHW) production; another one is the growing competition with photovoltaic (PV) systems. In order to widen the use of solar thermal collectors, they should also be able to contribute to space heating and cooling and become Multi-Purpose Solar Thermal Systems (MPSTS). This paper addresses the issue of optimal sizing of MPSTS. The criterion adopted is based on maximization of Net Present Value and has been applied to some cities in Italy and in Pakistan with diverse climate conditions. Results show that optimal thermal collector areas per peak cooling demand ( A c / P c ) can be conveniently expressed as a function of Peak Heating to Cooling Ratio ( P h / P c ). Optimum A c / P c varies between 3 and 5 m 2 /kW c and decreases with increasing P h / P c . The paper also analyses and compares a MPSTS with a multi-purpose PV-based heat pump system using a traditional one (boiler and compression chiller) as reference. Results show that steadily decreasing prices have made PV systems more favorable, even without consideration of public subsidies. [ABSTRACT FROM AUTHOR]

• Optimization of a solar air-conditioning process in Morocco based on energy and economic indicators for various cooling profiles and building categories. • Possible energy cooling costs saving when electricity is used as auxiliary backup for solar fractions between 40% and 70% in residential house and hotel. • ETC technology provides a reduction in collector's area between 20 % and 45% while FPC allows a higher economic viability especially for the hottest zones. • Reduction of exploitation costs between 25% and 50% for annual solar fraction of 70%. This paper investigates the energetic performance of solar air-conditioning by absorption chiller applied for building sector in Morocco. The combined effects of cooling profiles (Morning, Day and Morning), building categories (residential house, building office and hotel) and collector's technology on the potential of solar cooling installation operating under various meteorological conditions (Fez (Z3), Marrakech (Z5) and Zagora (Z6)) were assessed. It is found that it is possible to save in costs of produced cooling energy for the studied zones when electricity is used as auxiliary backup for annual solar fractions between 40% and 70%. A solar fraction of 70% each year can provide between 25% and 50% as a minimization of exploitation costs between 25% and 50%. Taking into consideration the present Moroccan costs of energy resources, it is highly recommended that the costs of solar cooling equipments, especially solar collectors and absorption machines, are more decreased to become more used for both domestic and industrial sectors. [ABSTRACT FROM AUTHOR]

• A new integration approach of solar energy and fossil fuel is proposed. • The inlet air in combined cycle is cooled by the waste heat from concentrating PV. • Investigate the performance enhancement mechanism of the system. • Investigate the influence of several key parameters on the system performances. • The annual performance potential of the new system is evaluated. A novel integration approach of solar energy and fossil fuel in the combined cycle power system is proposed in this paper. The system consists of concentrating PV/thermal collectors, absorption chiller, Brayton cycle and Rankine cycle. Apart from power generated by the spectral response, the waste heat from concentrating PV is used to drive an absorption chiller for cooling the ambient air, then the cooled air is compressed for fossil fuel combustion, achieving power production in the combined cycle. The reduction in work consumption of the compressor results in the increment of the power output of the combined system, realizing an indirect conversion process from solar energy to power. In this work, the heat transfer model of the PV/thermal collector and the mathematical model of a gas turbine with air-cooling are developed, and the performance enhancement mechanism of the system is investigated. Under the design conditions, the primary energy efficiency of the new system is 50.8%, and the conversion efficiency from solar energy to power reaches 85.8%, which is increased by 63.5% compared with conventional PV systems. The influences of several key parameters on the system performances are investigated, including inlet-air temperature of combined cycle, concentrating PV temperature and ambient parameters (solar radiation intensity and sky air temperature). Compared with the reference system that combines a concentrating PV subsystem and a combined cycle subsystem without absorption chiller, the proposed system achieves a 1.3% increment in the energy efficiency. As a result, the new integration form of solar energy and fossil fuel can significantly improve the conversion efficiency from solar energy to power and the thermodynamic performances. [ABSTRACT FROM AUTHOR]

The cascade utilization of waste heat for air conditioning system is still considerably lacking in the literature, especially for waste heat below 80.0 °C. In this paper, the experimental and simulation studies are carried out on an air conditioning system that integrates the absorption refrigeration subsystem (ARS) with the liquid desiccant dehumidification subsystem (LDDS). The waste heat at 80 °C is first used to drive the ARS to produce chilled water for air cooling, and then drive the LDDS for air dehumidification to realize heat cascade utilization. Firstly, the experimental study is conducted to compare CaBr 2 –LiCl–H 2 O with LiBr–H 2 O in the ARS and CaBr 2 –CaCl 2 –H 2 O with LiCl–H 2 O in the LDDS. The results show that the multicomponent solutions perform comparably to the single-component solutions. Then, a mathematical model is established to simulate the entire system using the appropriate multicomponent solution for each subsystem. It is found that the COP of the system reaches 0.77 at a driving temperature of 80.0 °C, with the supply air temperature of 23.0 °C and the humidity ratio of 10.5 g/kg. The waste heat can be recovered down to 61.0 °C, achieving a heat recovery depth of 19.0 °C. This system is expected to have significant potential in the applications due to its efficient heat utilization capability and low-cost multicomponent solutions. • An air conditioning system cascade driven by waste heat at 80 °C is studied. • The multicomponent solutions for each subsystem are selected by experimental study. • The COP of the system can reach 0.77 at the driving temperature of 80 °C. • Waste heat at 80 °C can be utilized down to 61 °C, achieving a heat recovery depth of 19 °C. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a method to determine the optimum capacity of distributed generation technologies for buildings. The Combined Heat and Power (CHP) unit has both absorption and electric chiller for cooling loads, and a supplementary boiler for heating loads. The demand is uncertain in the model. The underlying uncertainty is modeled using probabilistic theory. In this method, the expected value of the objective function is evaluated using numerical approaches. A simulation based optimization method is presented which can estimate the cost of system operation and find the appropriate design by means of stochastic programming. The effect of minimum economic turn-down of the facilities is also discussed in this paper. The optimum capacity of distributed generation technologies has a great effect on the cost of the building. Therefore, the proposed method is applied for a hospital in Iran as a case study. The results show that the optimum capacities of CHP and absorption chiller decreases and the capacities of the electric chiller and boiler rise by an increase in demand uncertainty. In addition, the appropriate minimum economic turn-down of facilities has a considerable effect on the overall system cost. [Copyright &y& Elsevier]

Highlights • New arrangement of Combined Cooling Heating and Power system with Stirling engine is presented. • Energy and exergy models of Stirling engine and absorption chiller is presented. • Effect of rotational speed on fuel consumption, carbon dioxide emission and fuel costs are analyzed. • The highest overall efficiency of the system is obtained at average rotational speeds. • The payback period for the system is calculated at different rotational speeds. Abstract Combined Cooling, Heating and Power system is one of the methods for improvement of primary energy using, reducing emissions and energy consumption costs compared to other usual energy supply systems. Because of the ability to use different fuel sources, lower noise and high efficiency, the Stirling engine has a great potential for Combined Cooling, Heating and Power system as prime mover. Hence, in this paper, a comprehensive analysis of this system with Stirling engine and absorption chiller has been proposed. This system has been evaluated from perspectives of energy, exergy, fuel consumption, carbon dioxide emissions and fuel costs at various rotational speeds of the Stirling engine and has been compared to usual energy supply system for buildings. Also, for the proposed system in different working conditions, the payback period is estimated. The modeling results illustrated that that the Coefficient of Performance (useful cooling capacity to required energy input) of absorption chiller, power output, heat loss, and exergy destruction reach to their maximum values during high rotational speeds. Also, the thermal efficiency, exergy efficiency, fuel consumption reduction, carbon dioxide emission reduction, and fuel costs reduction reach to their higher values at lower rotational speeds and the overall efficiency of the system reach to its maximum value at moderate rotational speeds. Therefore, based on different priorities, this system can be used at different engine rotational speeds. Also, with system operation of 6 h per day at the average engine rotational speeds, the payback period has been estimated less than 3 years. [ABSTRACT FROM AUTHOR]

Decentralized electricity production by cogeneration can result in primary energy economy, as these systems operate with a high-energy utilization factor (EUF), producing electricity and recovering energy rejected by the prime mover to meet site thermal demands. Because energy demands in buildings vary with such factors as the hour of the day, level of activity and climatic conditions, cogeneration case studies should consider different system configurations, energy demand profiles and climatic profiles. This paper analyzes an engine cogeneration system as an integrated thermal system by means of a computational simulation program. The simulation takes into account characteristics of the system, characteristics of the pieces of equipment, design choices and parameters, the variability of operating conditions, site energy demand profiles and climatic data to evaluate the performance of the cogeneration plant. Performance evaluation is based on: (i) the EUF, (ii) the exergy efficiency and (iii) primary energy savings analysis. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The hot water temperature that maximizes the overall instantaneous efficiency of a solar cooling facility is determined. A modified characteristic equation model is used and applied to single-effect lithium bromide–water absorption chillers. This model is based on the characteristic temperature difference and serves to empirically calculate the performance of real chillers. This paper provides an explicit equation for the optimum temperature of vapor generation, in terms of only the external temperatures of the chiller. The additional data required are the four performance parameters of the chiller and essentially a modified stagnation temperature from the detailed model of the thermal collector operation. This paper presents and discusses the results for small capacity machines for air conditioning of homes and small buildings. The discussion highlights the influence of the relevant parameters. [Copyright &y& Elsevier]

Abstract: In the last few years the solar-powered air-conditioning systems have been in intensive development and more often are considered as the viable application for the thermal solar systems in the regions of southern Europe. This is mainly due to the increasing higher electrical consumption in many countries (especially in Spain) which is moving from the winter to summer months due to expanding usage of cooling systems in this period of the year. In this paper we will analyze the behaviour of the solar-assisted air-conditioning system installed in the CIESOL building. This system consists mainly of flat-plate solar collectors and the simple effect LiBr–H2O absorption chiller. Different operation modes were analyzed. Coefficient of performance (COP) at various generator, absorber, condenser and evaporator temperatures is investigated and experimental results show that in practice it is easy to obtain values of about 0.6. The main goal of this paper is to describe the characteristics of the developing building and the solar-assisted air-conditioning system. Another useful purpose is to find the optimum conditions and operation parameters for the solar system through analyzing various systems'' operation strategies. [Copyright &y& Elsevier]

When the typical operation temperature of the Proton Exchange Membrane Fuel Cell (PEMFC) reaches 333.15–363.15 K, the ratio of electrical energy to waste heat generated by the PEMFC is about 1. In this paper, an absorption chiller with LiBr/[BMIM]Cl/CH 3 OH as the working pair is proposed to convert the waste heat into cooling capacity. The PEMFC and absorption chiller (AC) systems have been studied from the energy and efficiency point of view. The COP of the integrated system can reach a maximum of 0.85, which is remarkably 0.35 higher than that of the individual PEMFCs. The electrochemical process of the PEMFC and the thermodynamic process of the AC systems are calculated using MATLAB. The results show that the PEMFC operation temperature of 353.15–358.15K is sufficient to drive the AC and meet the requirement of 273.15–283.15K evaporation temperature and 308.15–313.15K condensation temperature. Meanwhile, when the electric power output from the PEMFC is 100 kW, the AC can output approximately 60 kW cooling capacity, which is sufficient to meet the cooling demand of the commercial bus. • Absorption chiller utilizing low-temperature PEMFC waste heat was proposed. • LiBr/[BMIM]Cl/CH 3 OH was used as a novel working pair in the absorption chiller. • Overall efficiency of the absorption chiller - PEMFC integrated system exceeds 0.8. [ABSTRACT FROM AUTHOR]

The mentioned paper has some incorrectness in the calculation of exergy and cost. For example, the auxiliary equations have been prepared for calculating cost but have not been fulfilled in the results. In some cases, the thermodynamic constraints of the expansion process have not been satisfied in the results.