Search

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]

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]

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]

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 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]

• 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 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]

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]

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]

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]

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]

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]

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]

• 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]

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]

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]

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]

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]

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]

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]

Highlights • Low-temperature driven absorption cycles are analyzed for air-cooled solar cooling. • Heat source temperatures of 75–100 °C and air temperatures of 20–40 °C are studied. • Optimized COPs of all the cycles are given in large temperature ranges. • Cycles with higher COP are given for air-conditioning and sub-zero conditions. Abstract Absorption chiller is a widely used technology owing to its capability to utilize low grade thermal energy including solar thermal energy and waste heat. Yet, most solar absorption cooling systems need cooling tower to dissipate heat rejection into ambient. The use of cooling tower increases both the initial investment and water consumption, which can be improved by air-cooled solar absorption cooling system. In this paper, to give the best absorption cycle options under different conditions, five absorption refrigeration cycles suitable for air-cooled solar cooling including three double lift absorption cycles and two semi-GAX (Generator-Absorber heat eXchange) absorption cycles were compared. Steady-state simulation is carried out. Efficiencies of these cycles were calculated with LiBr-water and water-ammonia working pairs in the scenario of air-cooled solar cooling. Heat source temperatures of 75–100 °C from non-concentrating solar collector and air temperatures of 20–40 °C were considered. Both air-conditioning condition with evaporation temperature of 5 °C and sub-zero condition with −10 °C were discussed. It is found that mass-coupled semi-GAX absorption cycle with ammonia-water is suitable for air-conditioning with higher heat source temperatures, mass-coupled double lift absorption cycle with water-LiBr is suitable for air-conditioning with lower heat source temperature and mass-coupled double lift absorption cycle with ammonia-water is suitable for sub-zero conditions. [ABSTRACT FROM AUTHOR]

Solar heating and cooling (SHC) systems are currently under rapid development and deployment due to their potential to reduce fossil fuel use and to alleviate greenhouse gas emissions in the building sector – a sector which is responsible for ∼40% of the world energy use. The available technologies on the market for thermally driven cooling systems are absorption and adsorption chillers, solid and liquid desiccant cooling systems, and ejector refrigeration cycles. Of these, absorption chillers are considered as the most desirable method for harnessing solar thermal energy due to their relative maturity, reliability, and higher efficiency. In addition, absorption chillers can take advantage of economies of scale in large buildings to obtain a relatively good levelized cost of cooling as compared to other thermally-driven air-conditioning systems. In this paper, the background theory on solar-powered absorption chillers is presented followed by a comprehensive literature review of the recent existing theoretical and experimental investigations on this technology is conducted. The review shows that the majority of solar absorption chillers installed and much of the research around the world is based on single-effect chillers and low-temperature solar thermal collectors, while less emphasis has been placed on the combination of high-temperature solar thermal collectors and multi-effect absorption chillers, especially triple-effect chillers. Research studies indicate the use of gas-fired backup systems for single-effect chillers is inefficient due to its very low primary energy savings. It was also found that the storage tank and piping can be major sources of heat losses in solar absorption cooling systems. Thus, special care should be taken to ensure sufficient and appropriate insulation for all heat loss components. In regions with low direct normal incidence solar resources (e.g. most of Europe), solar multi-effect chillers are relatively inefficient, so single-effect chiller-based solar cooling systems are the best techno-economic choice in such regions. Conversely, multi-effect absorption chillers with high-temperature collectors are indeed promising in regions with high solar resources. However, the review shows that using currently available technology, SHC absorption chillers are not able to economically compete with conventional cooling without government subsidies and incentives. Therefore, improving the economic performance of these systems is essential. While there is clearly more that can be done on chiller and solar collector components themselves, we believe some R&D emphasis going forward should also be dedicated to the balance of the system, including optimization of the system configuration, minimizing parasitic losses, improved design and integration of thermal storage and auxiliary system, and numerous controls and operational aspects. To date, many of these topics have been largely overlooked in favor of chiller performance studies. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel high-temperature solar assisted triple-pressure level combined cycle power plant. The system includes innovative high-temperature flat plate evacuated solar thermal collectors, a double stage lithium bromide/water absorption chiller, pumps, heat exchangers, storage tanks, mixers, diverters, controllers and a triple-pressure combined cycle power plant. This novel layout uses high-vacuum non-concentrating flat plate solar thermal collectors driving a double effect absorption chiller, leading to an overall high coefficient of performance for the solar cooling section. The provided cooling energy is used to cool gas turbine inlet air to enhance system efficiency and electrical capacity. This effect is mainly performed during central hours of the day when the conventional gas-fired combined cycles dramatically suffer for efficiency and capacity reduction, as a consequence of the corresponding increase of external air temperature. Such increase is related to the higher availability of solar radiation. This technology may be a viable solution, especially for hot and dry areas, in terms of primary energy savings and increased revenues. This prototypal system was numerically analysed for a combined cycle with a rated electrical power of 99 MWe and an electrical efficiency of 56%, developing a dynamic simulation model and detailed thermo-economic optimizations. Special attention is also paid to the design of novel control strategies aiming at maximizing the solar cooling effect. The results of the dynamic simulations show a very high average thermal efficiency of the solar collectors, equal to 34%. Implications of the performed work allowed an increase of the power output up to 5.5% and a satisfactory payback period equal to 10.7 years. [ABSTRACT FROM AUTHOR]

Solar cooling is one of the most promising technologies for covering the increasing needs of our society with a clean and sustainable way. This paper examines an ejector-absorption cooling system operating with the LiBr-H 2 O working pair which is driven by parabolic trough solar collectors. The main objective of this investigation is to optimize the total solar cooling system and to compare it with the respective optimum system with conventional absorption chiller and parabolic trough collectors. The generator temperature and pressure, as well as the pressure drop in the ejector, are the optimization parameters, while the maximization of the system performance is the objective function. According to the final results, the system with the ejector leads to higher COP (coefficient of performance) for the majority of the examined operating scenarios. Moreover, the optimized ejector-absorption system presents performance enhancement up to 60.9% compared to the conventional absorption system for the case with 12.5 °C evaporating temperature and 30 °C condenser temperature. For this optimum case, the system COP is about 1.01, the chiller COP is 1.65 and the system exergy efficiency is 4.76%. Generally, the system COP is ranged from 0.473 to 1.01 for the system with ejector, while the demanded specific collecting area from 0.987 to 2.11 m 2 /kW cooling . The analysis is performed with a developed model in Engineering Equation Solver which is validated with literature results. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The present paper deals with the performance prediction of Concentrated Solar Power plants integrated with cooling energy production. The plant configuration is based on a typical steam Rankine cycle (rated 62.1 MW e ). The thermal input is provided by two different solar fields: i) Parabolic Trough Collectors and ii) Central Receiver System with heliostats reflecting on the tower top. In the former case, both north-south and east-west oriented collectors are investigated and compared in the study. A Thermal Energy Storage system allows driving the power block 24-h per day also in periods with low solar irradiation. A steam flow rate extracted from the turbine low stages feeds a set of two-stage absorption chillers, and the produced chilled water is supplied to a district cooling network. A computer code integrating the commercial software Thermoflex and Trnsys has been developed to model and to simulate over 1-year period the solar field and the power block. The power plant is supposed to operate in island mode, having to meet power and cooling demand for a population of about 50,000 inhabitants in the Saudi desert region. Solar fields and storage system were sized according to a techno-economic optimization algorithm for the minimization of the investment costs. The simulation results show the beneficial effect of the combined power and cooling production in terms of peak load shaving. Compared to the troughs, solar tower exhibits a higher efficiency, thus requiring a lower aperture area and lower investment costs. The techno-economic analysis shows that the axis orientation has a strong impact on the trough collectors and that east-west oriented devices perform better for the investigated load-following application. [ABSTRACT FROM AUTHOR]

In this paper, the potential of a small scale concentrated solar Organic Rankine Cycle unit coupled with an absorption chiller for trigeneration purposes is investigated using a simulation analysis. At the moment, only few research works encompass small-scale solar trigeneration systems and most of them do not refer to real plant. On the contrary, in this work electric, heating and cooling maximum generation of a real and experimental small scale prototype system composed of a 50 m 2 CPC solar field, a 3.5 kWe ORC plant and a 17 kWc absorption chiller is investigated by means of TRNSYS. In particular, this work relies on the evaluation of the dynamic performance of the mentioned plant varying some selected system parameters to provide proper modifications of its design configuration and operation. More precisely, working temperature ranges, heating and intermediate fluid flow rates as well as volume of the storage tanks and size of the solar field have been varied within the simulation model. Results have shown that operating temperature ranges of the storage tanks considerably affect the overall performance of the system; by appropriately choosing these ranges the primary energy production can be increased by 6.5% compared to the baseline configuration without any additional investment costs. Moreover, setting suitably some design parameters can significantly contribute to extend the operating hours and the feasibility of a such small scale integrated system for residential applications. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate a solar cooling system with an absorption chiller driven by nanofluid based flat plate collectors. Pure water and water/Cu nanofluid (2% volumetric concentration) are the examined working fluids on the solar field and they are compared for steady-state conditions, as well as for daily operation. The system is optimized for steady-state conditions using a multi-objective procedure with energetic and exergetic criteria. The mean thermal efficiency enhancement by the use of nanofluids it is found close to 2.5%. The optimized system is further examined on a daily basis for operation with pure water and nanofluid. According to the final results, the use of nanofluids in the solar collector is able to enhance the exergetic performance of the system close to 4.0% and to increase the refrigeration production approximately 0.84% on a daily basis. The analysis is conducted with a developed model in Engineering Equation Solver. [ABSTRACT FROM AUTHOR]

Conventional coal-based CCHP system currently is believed to be less efficient than separate vapor compression cooling system in summer. In this paper, new configurations of CCHP system (N-CCHP) are proposed and studied which apply comprehensive methods to improve the system performance. In the N-CCHP, an absorption heat pump is applied in power plant to heat the primary water instead of a traditional heat exchanger. And, a small turbine is used to improve system performance with high bleeding steam pressure. In substation, the primary water is used to drive an absorption chiller and liquid desiccant equipment in series. The domestic water is also produced by the primary water after regeneration of liquid desiccant. Key influencing factors of the N-CCHP system have been fully discussed. In this way, a highly efficient N-CCHP system configuration is obtained and is analyzed to compare with the electricity driven vapor compression (VC) refrigeration system in summer. Results show that the N-CCHP is energy saving and own better performances when the primary water transmission distance is less than 60 km, or the COP of the vapor compression chiller is lower than 7. [ABSTRACT FROM AUTHOR]

Providing electric power and managing the thermal condition for the astronaut are two of the essential functions of the spacesuit life support system in a distance extravehicular activity. This paper proposed a new conceptual portable life support system which combines the cooling and power supply functions for the astronauts with the metal-hydride, fuel cell and absorption chiller. The cooling and power balance models were developed on basis of the first-law of thermodynamics. The second-law based entropy generation, exergy destruction and exergetic efficiency models of the integrated life support system were established. A parametric study was performed to evaluate the effects of varying working conditions, including the hydride metal types, operating temperatures of the fuel cells, heat transfer effectiveness of the evaporator and the concentration of the working fluid pair used in the absorption chiller, on the exergy-based performance of the new life support system. Results indicate that the energetic efficiency and the exergetic efficiency of the integrated PLSS can up to 86.98% and 59.07% respectively. [ABSTRACT FROM AUTHOR]

Solar assisted absorption chiller is one of efficient cooling production systems for large cooling capacities. The main drawback of this system is that in addition to the electricity consumption, it demands for a lot of heat in relatively high temperature range of 90–120 °C, though the solar system may provide a significant portion of this heating demand. On the other hand, in gas transmission systems, there are some expansion stations in which gas pressure is reduced considerably and this pressure drop causes temperature collapse in gas stream. Power productive gas expansion station (PPGES) is the most recent design proponed for these stations in which the unit is equipped with power generation systems. In this work, taking advantage of this temperature fall for cooling production is proposed by coupling the station with an absorption chiller. In this case, the chiller could also provide the heating demand of the expansion station. In order to evaluate the effectiveness of the proposed configuration, it is simulated for a case study in Denmark, i.e. Aarhus University (AU) hospital absorption chiller and Viborg gas station. The results show that the expansion station could provide an annual cooling production contribution of 27%. In addition, the paper presents an extensive economic assessment to prove the impact of the proposed system economically. The results show a great enhancement in the levelized cost of energy (LCOE) of the case study in case of employing the hybrid system instead of the conventional chiller. [ABSTRACT FROM AUTHOR]

The study described in this paper results from the observation that, when dealing with solar-driven absorption chillers, a compromise situation very likely exists between the collector efficiency and the coefficient of performance (COP) of the absorption cycle. An idea of a control strategy pursuing this objective, and thereby increasing the solar fraction for a solar absorption cooling cycle is consequently presented. The advantage of operating the solar chiller on a variable driving temperature is demonstrated. The theoretical analysis considers a solar chiller operated under moderate climate conditions of Poland. The model of the ammonia-water absorption chiller is described in detail, and the main assumptions of the iterative control procedure are explained. The effects of its application are computationally tested for one location and one type of solar collector, for representative days of three months during the cooling season. The results of the simulation are compared with the reference case of fixed driving temperature. According to the simulation results, it is possible to increase the cooling power yield at various levels, up to 34 W per 1 m 2 of solar collector, by adjusting the chiller driving temperature throughout the cooling season. The same, it is possible to more than double the cooling effect for some hours, with respect to fixed-temperature control operation. [ABSTRACT FROM AUTHOR]

In the present paper a combined cooling heating and power cycle is proposed to recover exhaust and compression heat of a 35.5 MW industrial gas turbine rated in summer operation. The cogeneration cycle comprises of double stage compressor, a regenerative gas turbine, absorption chiller, pumps and heat recovery units. The thermodynamical and environmental mathematical model of the cycle is developed using the Engineering Equation Solver software. The epsilon-number of transfer unit method is used to analyze the heat recovery system. A fitness function is proposed to aggregate five thermodynamical and environmental criteria and genetic algorithm is used for optimization. The results of the gas turbine and absorption chiller models are validated with the available data in the references and good agreement is achieved. Four design parameters of combustion temperature, compression ratio, pinch point temperature difference, and evaporator temperature are used for optimization. In the optimum state, the overall energy and exergy efficiencies are about 56% and 69%. Electricity production is 42.8 MW and 6.6% and 9.4% of the fuel energy can be recovered from the compression heat and exhaust gases. This heat recovery corresponds to producing 24.5 tons/h of superheated steam at 134.8 ° C and 167.4 kPa. The chiller produces 7.8 MW of cooling and its coefficient of performance is 0.68. The carbon monoxide, carbon dioxide and nitrogen oxides reduction are more than 87%, 17%, and 13% respectively. [ABSTRACT FROM AUTHOR]

In this paper, a detailed numerical analysis of a Combined Cooling, Heating and Power system is presented, aiming at determining its optimal operating strategy in a real industrial application. The system layout includes a reciprocating engine, fuelled by natural gas, heat exchangers for waste-heat recovery, pumps, storage tanks, a single-effect water lithium bromide absorption chiller, a cooling tower, a back-up vapour-compression electric chiller, mixers and valves. A dynamic simulation model of the whole system was developed in TRNSYS. A case study was analysed, referred to a real industrial application, where the system under evaluation should be installed in the near future, providing electricity, mainly used for the production process, and space cooling. Real measured data were used to estimate the electric energy demand of the factory. A detailed building simulation model was used to calculate heating and cooling demands. A detailed economic analysis was carried out, aiming at evaluating: (i) the optimal size of the Combined Cooling, Heating and Power system; (ii) the optimum control strategy, from a thermo-economic point of view, comparing three different cases: Base-Load operation, electric load tracking and a new hybrid strategy based on the simultaneous tracking of electric and thermal-loads. The results showed that the optimal capacity of the system was lower than that selected by the designers of the real unit to be installed. The hybrid control strategy obtained the best profitability, achieving a simple pay-back period equal to 3.8 years, compared to 4.1 years achieved in case of electric-load tracking. [ABSTRACT FROM AUTHOR]

This paper presents and discusses the performance improvement and operational flexibility of a Single-Stage Combined Absorption Power and Refrigeration Cycle (SSAPRC) with an integrated compression booster. The compression booster is placed between the absorber and the evaporator. A mechanical compressor and later a thermal compressor (vapor-ejector) are used as a compression booster. This added feature is very interesting for this type of cycle, because they generate power that could be used in the cycle itself to produce the compression needed to enhance the cycle’s performance. The energetic and exergetic performance of these new modified combined absorption cycles have been analyzed for typical thermal boundary conditions and design parameters. The integration of a mechanical compressor or a vapor ejector reduces the required driving temperature of the cycle, and when a certain split ratio is exceeded the system can work in dual-output mode producing power and cooling. The use of a vapor ejector further improved the net power output of the system. The proposed cycle configurations have an outstanding adaptability and flexibility to respond to the variation of heat source and heat rejection temperatures by adjusting the compression ratio. These cycles are therefore excellent candidates to provide simultaneous power and refrigeration, using renewable energy sources such as solar thermal energy, biomass or waste-derived fuels in polygeneration systems for remote locations or those with difficult access to the electrical grid. [ABSTRACT FROM AUTHOR]

In this paper a general model for the steady state simulation of a solar absorption chiller is proposed. The novelty of this model is to calculate the physical state of all the streams rather than fix them (especially at the outlet of the condenser and evaporator). The thermodynamic properties of the mixture can be calculated by suitable predictive thermodynamic models, hence the working pair can be changed easily. Using this thermodynamic model, a general Positive Flash model is able to describe all the possible states (sub-cooled, super-heated, biphasic) of the various streams which are all considered as multicomponent mixtures. In the positive flash the same set of governing equations is valid for all phase regions. Another originality of the present study is that the generator is modelled as a distillation column, using the theoretical plate concept: MESH equations (Mass balance, Equilibrium, Summation, Heat balance) were written for each stage. Despite the modular structure of the software, a global solution strategy was implemented, using a Newton-Raphson method. This model is successfully compared to an example in the literature which deals with a GAX (Generator-Absorber heat eXchange) configuration absorption chiller using ammonia/water as the working pair. [ABSTRACT FROM AUTHOR]

Due to the production of hydrogen, using fuel cells for energy conversion and storing encounters safety problems. Combining high-temperature solid oxide fuel cells with photovoltaic solar panels or zinc oxide solar panels can be a good candidate to produce/convert and store the energy more efficiently for using at peak times. The current paper intends to analyze the efficiency of integration of zinc oxide solar panels and fuel cells to produce hydrogen directly. Therefore, the excess step of converting electricity to hydrogen and re-converting it to electricity, which is customarily used for the integration of the photovoltaic and solid oxide fuel cells, could be skipped. The new method paves the way for providing the required energy for heating/cooling through the floor heating and ceiling cooling systems as well as generating electricity. The article also demonstrates that it is possible to have heat during the day and night for an area of 1920 m 2 and 542 m 2 . It is also possible to create coolness during the day and night for an area of 925 m 2 and 260 m 2 . [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]

Solar heating and cooling (SHC) systems are currently under rapid development and deployment due to their potential to reduce the use of fossil fuel resources and to alleviate greenhouse gas emissions in the building sector – a sector which is responsible for ∼40% of the world energy use. Absorption chiller technology (traditionally powered by natural gas in large buildings), can easily be retrofitted to run on solar energy. However, numerous non-intuitive design choices must be analyzed to achieve the best techno-economic performance of these systems. To date, there has been little research into the optimal configurations among the long list of potential solar-driven absorption chiller systems. To address this lack of knowledge, this paper presents a systematic simulation-based, multi-objective optimization of three common, commercially available lithium bromide-water absorption chillers – single-effect, double-effect and triple-effect – powered by evacuated tube collectors (ETCs), evacuated flat plate collectors (EFPCs), and concentrating parabolic trough collectors (PTCs), respectively. To the best of authors’ knowledge, this is the first study of its kind that compares the optimized designs of the most promising configurations of solar-assisted absorption chillers against a common set of energy, economic, and environmental metrics from a holistic perspective. A simulation model of these three configurations is developed using TRNSYS 17. A combined energy, economic, and environmental analysis of the modeled systems is conducted to calculate the primary energy use as well as the levelized total annual cost of each plant, which are considered as two conflicting objective functions. By coupling TRNSYS and MATLAB, a multi-objective optimization model is formulated using a genetic algorithm to simultaneously minimize these objectives, thereby determining a set of optimal Pareto solutions corresponding to each SHC configuration. The performance of the proposed systems at their optimal designs is then compared to that of a reference conventional system. A sensitivity analysis is also performed to assess the influence of fuel cost, capital cost of innovative components, and the annual interest rate on the Pareto front of optimal solutions. Overall, the optimization results reveal that of the proposed configurations, the SHC double-effect chiller has the best trade-off between the energetic, economic and environmental performance of the system, having a total cost of ∼0.7–0.9 M$ per year and reducing the annual primary energy use and CO 2 emissions by 44.5–53.8% and 49.1–58.2% respectively (relative to the reference conventional system). With the high capital cost associated with these systems, government subsidies and incentives are still required in order for them to achieve satisfactory payback times and become cost-competitive with conventional HVAC systems. [ABSTRACT FROM AUTHOR]

Utilizing renewable energies is the promising solution to the environmental problems which are brought about due to fossil fuel consumption. The fact that these kinds of energies are intermittent can be overcome with using energy storage systems. Wind energy coupled with compressed air energy storage systems is one of the best candidates in this respect. The main objective of this paper is to study the integration of this system with a Combined Cooling, Heating and Power cycle comprised of a gas turbine, an organic Rankine cycle and an absorption refrigeration system. Energy and exergy analyses are applied to the system and the effect of key parameters on the system performance are analyzed. The results show that under design condition, the system can generate 33.67 kW electricity, 2.56 kW cooling and 1.82 ton per day hot water with a round trip energy efficiency of 53.94%. Also exergy analysis reveals that wind turbine, combustion chamber and compress air storage system have the highest amount of exergy destruction respectively. Finally, sensitivity analysis shows that parameters related to gas turbine are the most prominent parameters of the system which can change performance of the system considerably. [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]

Two novel configurations are proposed to replace the conventional Rankine cycle based steam power plants (SPP) with natural draft wet cooling towers (NDWCT) as cooling units. Closed feedwater heater unit of the base SPP-NDWCT system is eliminated in order to combine a vapor compression refrigeration (VCR) and an absorption heat pump (ABHP) with the base SPP-NDWCT system. Both VCR-SPP-NDWCT and ABHP-SPP-NDWCT systems are integrated to decrease the NDWCT load which could result in water losses decrease. In part one of the presented two-part paper, model-based energy and economic analyses are performed to compare systems performance and applicability. The temperature difference at pinch point and temperature difference between the hot and cold sides of the heat exchangers which were used for systems integration in VCR-SPP-NDWCT, and the absorber pressure and temperature in ABHP-SPP-NDWCT system are studied using parametric analysis procedure. A water-fuel management strategy is also introduced for the ABHP-SPP-NDWCT system according to the influence of the absorber pressure changes on system water and fuel consumption. In part 2, environmental and thermoeconomic analyses are performed to complete a comprehensive study on designing steam power plants. The results of part 1 showed that water losses and total annual costs decreased by 1–18% and 0–4.7% for the ABHP-SPP-NDWCT system but increased by 11% and 60% for the VCR-SPP-NDWCT system, respectively. [ABSTRACT FROM AUTHOR]

The demands for space air conditioning and clean drinking water are relatively high in Middle East North African (MENA) countries. A sustainable and innovative approach to meet these demands along with the production of domestic hot water is experimentally investigated in this paper. A novel solar thermal poly-generation (STP) pilot plant is designed and developed for production of chilled water for air conditioning using absorption chiller, clean drinking water with membrane distillation units and domestic hot water by heat recovery. The STP system is developed with a flexibility to operate in four different modes: (i) solar cooling mode (ii) cogeneration of drinking water and domestic hot water (iii) cogeneration of cooling and desalination (iv) trigeneration. Operational flexibility allows consumers to utilize the available energy based on seasonal requirements. Performance of STP system is analyzed during summer months in RAKRIC research facility. Energy flows in STP pilot plant during peak load operations are analyzed for all four modes. STP system with trigeneration mode utilizes 23% more useful energy compared to solar cooling mode, which improves overall efficiency of the plant. Economic benefits of STP with trigeneration mode are evaluated with fuel cost inflation rate of 10%. STP plant has potential payback period of 9.08 years and net cumulative savings of $454,000 based on economic evaluation. [ABSTRACT FROM AUTHOR]

The present work investigates the feasibility of solar heating and cooling (SHC) absorption systems based on combining three types of LiBr–H 2 O absorption chillers (single-, double-, and triple-effect) with common solar thermal collectors available on the market. A single-effect chiller is coupled with evacuated tube collectors (ETCs) – SHC1. A double-effect chiller is integrated with parabolic trough collectors (PTCs), linear Fresnel micro-concentrating collectors (MCTs) and evacuated flat plate collectors (EFPCs) respectively – SHC2, SHC3, and SHC4. PTCs are employed to provide high-temperature heat to a triple-effect absorption chiller (SHC5). Although triple-effect chillers have been around for a while, this paper represents the first system-level analysis of these chillers coupled with high-temperature solar concentrating collectors for air-conditioning applications. A simulation model for each configuration is developed in a transient system simulation environment (TRNSYS 17). Furthermore, a unique, comprehensive perspective is given by investigating the impact of characteristic solar beam radiation to global radiation ratios on the techno-economic performance of the proposed SHC plants for a wide variety of climatic regions worldwide. The results of parametric study suggest that a storage volume of around 70 L/m 2 is a good choice for SHC1, while 40–50 L/m 2 storage capacity is sufficient for the other configurations (SHC2 to SHC5). The simulation results reveal that when the fraction of direct normal irradiance (DNI) is less than 50%, SHC2, SHC3, and SHC5 require larger collector area compared to SHC1, showing there is no advantage in using concentrating collector powered multi-effect chillers over solar single-effect chillers in climates with low DNI level. However, in climates with DNI fractions above 60%, the smallest solar field is achieved by SHC5, followed by SHC2. SHC4, which benefits from both relatively high COP of double-effect chiller and the diffuse component in the solar field, results in the most reasonable trade-off between energetic and economic performance of the system in a wide range of climatic conditions. [ABSTRACT FROM AUTHOR]

In this paper, a novel solar thermal polygeneration (STP) system for production of cooling, clean water and domestic hot water is modeled and analyzed for the weather conditions of United Arab Emirates (UAE). The system comprises of solar collectors for production of thermal energy, single stage LiBr–H 2 O absorption chiller (VAC) for providing air conditioning to office cabins and membrane distillation (MD) modules for clean water production along with domestic hot water generation as by-product. The performance of STP is analyzed with three different solar collectors – flat plate collectors (FPC), evacuated tube collector (ETC) and compound parabolic collector (CPC). The system is modeled and dynamically simulated using TRNSYS software for optimization of various design parameters like slope of the collectors, mass flow rate through the collector loop, storage capacity and area of collectors. Combined and system efficiency of the STP system has been determined for optimum conditions. Economic benefits are analyzed for different collectors and fuel costs savings. A lowest payback period of 6.75 years is achieved by STP with evacuated tube collector field having gross area of 216 m 2 . STP system has cumulative savings of $520,000 over the life time of the project through roof top solar collector installation. In terms of environmental benefits, 109 metric tons/year of CO 2 emissions would be avoided and hence the overall payback period would be reduced by 8% based on cost saving through carbon credits. Economic and environmental benefits were aided by steady system performances of absorption chiller (35 kW), membrane distiller (80 l/day) and heat recovery system (1.2 m 3 /h) throughout the year. The complete simulation results of the STP system is utilized for the development, installation and testing of a polygeneration system at RAKRIC. [ABSTRACT FROM AUTHOR]

Thermal cooling systems are particularly attractive in locations supplied by district heating based on cogeneration heating plants (CHP). Moreover, solar thermal energy is a major renewable source for the provision of thermal energy, fulfilling demands for space heating, domestic hot water, process heat, and cooling. This energy source can be suitably used also in Nordic Countries. The presented paper focuses on two configurations of a cooling solar-driven thermal system for an office building located in Finland. Dynamic simulation approach has been used through TRNSYS software. In particular, the configurations differ from the connection between the hot storage tank, the solar collectors and the chiller. Particularly, in the first configuration only the tank can supply the chiller (Case 1), while in the second, the chiller can be supplied either by the tank or the solar collectors directly (Case 2). System performance indexes, in case of district heating as main building heating supply system in winter and as auxiliary heating system for the chiller in summer, have been evaluated as a function of the tank and solar thermal field sizes. Results show that Case 2 has better performance than Case 1, because of the versatility shown in summer. Particularly, when the solar irradiance is low, Case 2 solutions perform far better than Case 1 solutions, benefitting from the direct connection between the solar collectors and the chiller. This study has highlighted also the potential of this technology in cold climate areas supplied by means of DH based on CHP plants. Indeed, the adoption of such cooling technology, in addition to reduce both heating and cooling consumed energy and to shave summer electricity peaks, can potentially allow some CHP plants to operate also in summer, fulfilling the future energy networks aims: being able to provide electricity, heat and cooling energy. [ABSTRACT FROM AUTHOR]