Organic Rankine Cycle Evaporator Research Articles

Energetic/exergetic study of Kalina and refrigeration bottoming cycles on different solar‐driven organic Rankine cycles

AbstractCombination of different power cycle scenarios is of prime importance in achieving maximum energy utilization from solar‐driven multigeneration systems. To fulfill such objective, the present article proposes a novel energy distribution system, leveraging a combination of direct‐fed organic Rankine cycle (ORC) and a bottom‐cycled arrangement of Kalina cycle system (KCS) and double‐effect absorption refrigeration cycle (DEARC) within a parabolic trough solar collector powered trigeneration system. The study explores three different ORC configurations: simple ORC; ORC equipped with internal heat exchanger (ORC‐IHE) and regenerative ORC (RORC). It is shown that although higher efficiencies are achievable from a larger portion of PTSC energy absorbed by the ORC, the ORC energy absorption is limited by ORC evaporator temperature differences, and there is unused energy that can be recovered by the KCS, based on the proposed energy system. The results indicate that the addition of bottoming KCS leads to a considerable increase in the exergy efficiency of ORC, ORC‐IHE and RORC‐based systems by 11.7%, 30.7% and 32.6%, respectively. The impact of different ORC configurations, key ORC parameters and various organic working fluids on the energetic/exergetic efficiencies is also examined to find the optimal configuration. In terms of overall energetic/exergetic efficiencies, the highest performance belongs to ORC (78.4%/30.4%) while the lowest energetic and exergetic efficiencies belong to ORC‐IHE and RORC, respectively (56.3% and 25.65%). On the basis of a comparative study with the available literature, these values are higher than what is already reported for similar solar‐driven multigeneration systems. Appropriate thermal match and lower exergy destruction in the KCS, and bottoming cycle arrangement of the DEARC are the main reasons for such enhanced performance. This research not only contributes valuable insights into efficient solar‐driven systems but also sets a new benchmark for performance metrics in the existing literature.

Comparative study of thermally integrated pumped thermal energy storage based on the organic rankine cycle with different working fluid pairs

Thermal integrated pumped thermal energy storage (TIPTES) systems with the features of high efficiency, flexibility, and reliability, have attracted increasing attention since they can integrate low-grade heat sources to further improve the utilization and economic viability of renewable energy. In this study, a typical TIPTES system driven by waste flue gas is established, and the heat pump and organic Rankine cycle (ORC) are chosen as the charging and discharging cycle, respectively. Four organic fluids, including R600, R245fa, R601a, and R1336mzz(Z), are selected to compose sixteen different working fluid pairs for thermodynamic analysis. The effects of key parameters, like heat pump system evaporation temperature and hot storage tank temperature, on system performance were analyzed, and the single-objective optimization was conducted. A comparative study was carried out to identify the best working fluid pair according to the optimization results. Results show that the system’s power-to-power efficiency goes up as the evaporation temperature increases while an increase in the heat storage temperature decreases the exergy efficiency of the TIPTES system. Optimization results show that the R245fa + R245fa is the best working fluid pair, and in this system, the ORC evaporator has the largest exergy destruction at about 260.84 kW, which is 20.2% of the total. On the other hand, the ORC pump has the smallest exergy destruction only about 0.5%. This study also finds that the system’s power-to-power efficiency of using different working fluids in either heat pump cycles or ORC cycles is lower than that of using the same working fluid throughout the entire system.

Energy-saving installation of a river vessel

This article relates to diesel engineering and can be used by design organizations and river fleet vessels in operation. The device of the energy-saving installation of a river vessel uses a heat pump with a high-temperature two-stage compressor and an Organic Rankine Cycle (ORC). In a two-stage compressor, the temperature of the low-boiling substance reaches 100°C. Further, this steam is condensed in the ORC condenser, while the coolant is heated to 95-98°C and the resulting coolant is distributed through a three-way valve: part of the coolant flow enters the heating object, the other part of the coolant enters the ORC evaporator through a three-way valve, where heat exchange with a low-boiling substance takes place. The resulting high-pressure steam then enters the turbine. In this case, the steam turbine is driven with a generator and electrical energy is generated. The proposed energy-saving installation can be used by river vessels during cargo operations and forced stops, during which the power plant: the main marine diesel engine, diesel generator and auxiliary boiler plant are inoperative, which leads to significant fuel savings of the ship power plant.

Thermodynamic investigation of a novel organic Rankine cycle including partial evaporation, dual-phase expander, flash tank, dry expander and recuperator for waste heat recovery

The optimum exploitation of low-grade waste heat sources is a critical issue for producing clean electricity and promoting sustainability. Organic Rankine Cycle (ORC) is an emerging technology to produce electricity exploiting various energy sources like waste heat recovery, solar irradiation and geothermal energy. The present work suggests a novel ORC architecture that combines different solutions for increasing electricity production from low-grade waste heat sources (e.g., industrial waste heat up to 200 °C). More specifically, the present cycle includes the solution of partial evaporation, dual-phase expansion, flash tank separator, dry expander and recuperator. All these concepts together create a global optimal design which is examined with the environmentally friendly working fluid R1233zd(E). The present work examines the suggested ORC parametrically, and then the design is optimized. According to the results, the present novel configuration was found to outperform compared to the trilateral cycle, classical ORC without superheating, flash tank cycle, and partial evaporation ORC, for waste heat stream temperatures from 80 °C up to 200 °C. Furthermore, the analysis for the novel systems proved that the optimal system energy efficiency was found to range from 2.3% for Tin = 80 °C up to 13.3% for Tin = 200 °C, while the respective exergy efficiency from 27.3% for Tin = 80 °C up to 62.5% for Tin = 200 °C.

Optimization of a solar energy system integrating cooling, hot water, and power units in Australian cities: A climate-based analysis and cost-efficiency investigation

This study presents an investigation into the analysis and optimization of a solar energy system that integrates cooling, hot water, and power units. The system employs PV/T (photovoltaic/thermal) modules to generate electricity and provide thermal energy simultaneously. Using the response surface methodology (RSM), the system is subjected to multi-objective optimization to enhance its performance and decrease costs. The first optimization scenario focuses on maximizing net output power and minimizing the cost of the thermoelectric generator (TEG). Six choice factors are identified to improve the system's cost and exergy efficiency. Results indicate an optimal exergy efficiency of 19.704% and a favorable cost rate of 1.774 $/h for the proposed system. Economic analysis reveals that the most expensive subsystems are the proton exchange membrane (PEM) electrolyzer and organic Rankine cycle (ORC). Exergy analysis highlights the PV panels, absorption chiller, PEM electrolyzer, and ORC evaporator as components with significant exergy devastation. To assess the system's viability in Australian cities, it is analyzed across six climate zones. The city of Maitland emerges as the most optimal candidate for system implementation. The study demonstrates that the proposed approach performs best in cities with similar climates to Maitland. Considering the impact of environmental factors such as temperature and sunlight radiation is crucial for determining system costs, net output power, and exergy efficiency on a global scale. Overall, this research contributes to the understanding of solar energy systems by integrating cooling, hot water, and power units. It emphasizes the importance of climate-based analysis and optimization for efficient system performance. The findings provide valuable insights for the design and implementation of solar energy systems, facilitating their widespread adoption and contribution to sustainable energy solutions.

Thermodynamic investigation of a solar-driven organic Rankine cycle with partial evaporation

The partial evaporation organic Rankine cycle (PE-ORC) is an emerging technology for the efficient exploitation of low-temperature heat sources. The purpose of the present study is the energy and thermodynamic analysis of a solar-fed PE-ORC with a solar field of evacuated flat plate collectors coupled to a sensible storage tank. The studied PE-ORC operates with the environmentally friendly working fluid R1233zd(E) with variable evaporation percentage in the expander inlet. The thermodynamic investigation is done with a validated model in Engineering Equation Solver, and the transient analysis is performed with the TRNSYS tool by coupling it with the thermodynamic model. According to the dynamic analysis, the annual electrical yield is found at 6243 kWh, while the maximum obtained value is found at 3.81 kW. Moreover, the annual mean solar field efficiency was calculated at 45.0%, the annual mean thermodynamic cycle efficiency at 8.71% and the annual mean system efficiency at 3.68%.

Optimization analysis of Organic Rankine Cycle powered by waste heat of a supermarket transcritical CO2 multi-ejector refrigeration cycle

The exploitation of low-grade heat sources that are available from existing thermal systems processes consists a promising concept for the production of energy. In this research, the integration of an Organic Rankine Cycle (ORC) unit on a supermarket transcritical CO2 refrigeration system with ejectors is investigated, which is supplied with low-grade heat by the common discharge of the compressors. The optimization analysis proves that for different combinations of CO2 temperature and pressure in the ORC evaporator, as well as for different ORC condensation temperatures, there is a different optimum ORC evaporation temperature that leads to the highest energy production. Concerning the annual performance analysis conducted for the city of Athens, Greece, operation with isopentane is found to provide the greatest energy production with 10.36 MWh annually, which corresponds to a 3.69% reduction in the refrigeration system's energy consumption. For operation under the ambient temperature of 40 °C, the corresponding reduction of the refrigeration system consumption due to the presence of ORC is 7.54%. Finally, the financial analysis reveals that toluene is the most advantageous solution, leading to a payback period of 3.9 years, with a net present value by the end of the project's lifetime equal to 34.32 k€.

Optimization of exergetic performance and payback period of organic rankine cycle integrated vapor compression refrigeration system based on exergy, economic, and environmental criteria

In this paper, a multi-objective optimization study is carried out to determine the optimal exergetic performance (𝜂𝑒𝑥) and the payback period (PB) of the organic Rankine cycle (ORC) integrated vapor compression refrigeration (VCR) system based on exergy, economic, and environmental criteria using non-dominated sort genetic algorithm-II (NSGA-II). Moreover, a sensitivity analysis is carried out to improve the exergetic performance of the system. The working fluid, the pinch-point temperature difference of the ORC evaporator (ΔToep ), con-denser (ΔTpcond), and the VCR evaporator (ΔTpve), cooling water inlet temperature (Tcw1), chilled fluid temperature (Tcf2), and heat-source inlet temperature (Th1) are taken as the decision vari-ables. The results of this study indicate that butane is the most suitable working fluid for op-timal exergetic efficiency, 𝜂𝑒𝑥 (33.7%) and payback period, PB (4.9 years) of the system. The optimal values of other decision variables such as Th1, Tcw1, Tcf2, ΔToep , ΔTpve , and ΔTpcondare 378 K, 313 K, 276 K, 10 K, 5 K, and 5 K respectively.

Selection of a suitable working fluid for a combined organic Rankine cycle coupled with compression refrigeration using molecular approaches

A vapor compression refrigeration cycle (VCRC) driven by an organic Rankine cycle (ORC) is an alternative to generating cold through a renewable energy source such as solar, residual thermal, and geothermal energy. The system analyzed in this work consists of an ORC coupled with a VCRC by a shaft where each one of the cycles uses an independent working fluid. This manuscript analyses 8 working fluids resulting in 16 combinations. These fluids include common refrigerants, such as R22 (HFCF) and R134a (HFC), with other low or null global warming potential (GWP) substances, such as hydrocarbons (HCs) and hydrofluoroolefins (HFOs). The PC-SAFT EOS is used as a predictive tool to obtain the equilibrium condition and thermophysical properties at each point in the cycle. The choice of the best combination of working fluids is done under the criteria that the ORC boiler and evaporator temperatures work in a range of 60.0 to 100.0 °C and −15.0 to 0.0 °C, respectively. The compressor outlet temperature, the VCR-ORC system Coefficient of Performance (COP), and the VCRC COP are the selected key parameters analyzed. The results show that the combination of n-pentane and R1233zd provide a good performance in terms of COP compared to other refrigerants.

Thermo-economic assessment of sub-ambient temperature pumped-thermal electricity storage integrated with external heat sources

Thermally integrated pumped-thermal electricity storage (TI-PTES) offers the opportunity to store electricity as thermal exergy at a large scale, and existing studies are primarily focused on TI-PTES systems based on high-temperature thermal energy storage. This paper presents a thermo-economic analysis of a “cold TI-PTES” system which converts electricity into cold energy using a vapor compression refrigeration (VCR) unit and stores it at sub-ambient temperatures during the charging process, and generates electricity by using an organic Rankine cycle (ORC) working between the sub-ambient temperature and an external low-grade heat source during the discharging process. The effects of key parameters, i.e., mass flowrate and temperature of the storage medium, ORC evaporation temperature, component efficiencies, and pinch-point temperature differences, on the system performance are evaluated based on a whole-system thermo-economic model. The results reveal that the roundtrip efficiency and levelized cost of storage (LCOS) of the system increases while the electrical energy storage capacity decreases as the temperatures of the two cold storage tanks approach each other. When the temperature of the cold storage tank 1 rises from 1 °C to 8 °C while the cold storage tank 2 remains as 13 °C, there is an increase of 25% and 20% in the roundtrip efficiency and LCOS respectively while the energy storage capacity decreases by 69%. A roundtrip efficiency of 0.74 and LCOS of 0.32 $/kWh are achieved with a heat source temperature of 85 °C, using a mass flowrate and temperature of the cold storage medium of 50 kg/s and 1 °C. Furthermore, any change in cold storage medium mass flowrate changes both electrical energy storage capacity and power output by the same proportions. With a continuous high-flowrate external heat source, the LCOS can be as low as 0.17 $/kWh. By providing sufficient heat from an external heat source, the proposed system possesses a high potential for medium-to-large scale energy storage with a unique hybrid nature for electricity storage and thermal integration.

Experimental investigation on the dynamics of an Organic Rankine Cycle evaporator with large-mass fins for the purpose of reducing heat input fluctuations

Waste heat recovery from energy-intensive processes using Organic Rankine Cycle (ORC) is a promising effective method to reduce large quantities of energy waste and emissions in the planet. However, one of the main technical challenges that remain for its widespread implementation is related to the intermittent and fluctuating nature of the thermal power available from waste heat sources.This paper presents a test rig to study the effect of the geometry of an ORC evaporator to mitigate the adverse effects of thermal power fluctuations of a waste heat source. An experimental campaign is carried out to analyse the dynamic behaviour of the ORC evaporator, which has a custom geometry aimed at increasing its energy storage capacity. The experimental results show that the evaporator is able to dampen fluctuations of the heat source with cycle durations of up to 12 min. It is shown that an evaporator design consisting of a finned tube heat exchanger with large mass of the fins can have a dramatic effect on the thermal inertia of the system. Such a design can help to dampen or reduce some of the variation of the heat source that is transmitted to the ORC system. This, in turn, can allow the ORC system to work in more stable conditions and reduce the need for aggressive control measures or additional heat storage equipment.

Technical assessment of novel organic Rankine cycle driven cascade refrigeration system using environmental friendly refrigerants: 4E and optimization approaches.

Hydrocarbons are a promising working fluid for organic Rankine cycles and refrigeration systems that have gained increasing attention in recent decades as a replacement for the currently used higher global warming potential fluids. A novel standalone cascade refrigeration system (CRS) has been developed in this study for simultaneous ultra-low temperature cooling and heating production to medical applications most suitable for rural and power outages. Using the energy utilization factor (EUF) metrics, neopentane was chosen as the working fluid for the organic Rankine cycle (ORC) system among the selected hydrocarbon (HC) refrigerants. The standalone ORC-CRS system performance was investigated in terms of cooling and heating capacity, EUF, exergy, and environmental metrics by varying both ORC and CRS key temperature parameters. The exergy destruction of individual components was evaluated, and it was found that the ORC evaporator has the highest exergy destruction, followed by the expander. The highest EUF and exergy efficiency for a combined ORC-CRS system was about 0.64 and 38%. The maximum cooling and heating capacity of novel standalone CRS system was achieved by 70kW and 225kW respectively at a typical operating condition. At a higher ORC evaporation temperature, the exergy efficiency of the ORC-CRS system is decreased, leading to reduction in SI. The standalone ORC-CRS system at ORC evaporator temperature of 150°C achieved the maximum CO2 emission tax savings of $ 6.4 × 107 over a 15-year lifetime period. The total annualized cost index of the combined cooling heating system is in the range between 35 and 60 $/h for the variable operating condition. Non-dominated sorting genetic algorithm II (NSGA-II) method was used to conduct the multi-objective optimization analysis, and the technique for order of preference by similarity to ideal solution (TOPSIS) method used to found the optimal point, which had the following values of TAC 42.22 $/h and exergy efficiency was around 46.10%.

Parametric and economic analysis of high-temperature cascade organic Rankine cycle with a biphenyl and diphenyl oxide mixture

High-temperature organic Rankine cycle (ORC) systems have the potential to improve the heat-to-power conversion efficiency and expand the temperature range for heat recovery, heat battery and solar power generation. Restricted by the critical temperature of the commonly used organic working fluids, the current ORC technology has a maximum working temperature of around 300 °C. This paper proposes a high-temperature cascade organic Rankine cycle (CORC) system using a biphenyl and diphenyl oxide (BDO) mixture as the top cycle fluid and conventional organic fluids for the bottom cycle. The BDO mixture has excellent heat stability over a wide operation condition from 12 °C to 400 °C in single-phase and binary-phase states. However, at present a detailed study on the ORC using the mixture is lacking. In this paper, a parametric analysis of the high-temperature CORC system is conducted. A mathematical model based on the equivalent hot side temperature is built to simulate the ORC efficiency. The thermodynamic and exergetic performances of the novel CORC system under different bottom ORC working fluids, mixing chamber temperatures, evaporation temperatures, and condensation temperatures are investigated. The results show the maximum thermal efficiency of the CORC system is 38.74 % and 40.26 % at top ORC evaporation temperatures of 360 °C and 400 °C. The largest exergy destruction takes place in the heat exchanger between the top and bottom ORCs. Besides, the heat regenerators have a significant impact on the thermodynamic performance and can elevate the CORC efficiency by about 4 %. The proposed system has a higher efficiency and a lower equipment cost than conventional steam Rankine cycle at 400 °C while eliminating the challenges of wet steam turbines.

Enhancement effects of adding internal heat exchanger on dual-pressure evaporation organic Rankine cycle

Dual-pressure evaporation organic Rankine cycle shows a good outlook in the power generation of medium-to-low temperature heat. Adding internal heat exchanger (IHE) is an important potential way to enhance its performance. While, the impacts of adding IHE have not been analyzed especially. The effectiveness, quantitative enhancement effects, and suitable scenarios of adding IHE need to be studied. This paper quantitatively evaluates the enhancement effects of adding IHE in the typical series dual-pressure evaporation ORC (SDORC). Impacts of heat source temperature, outlet restraint, corrosion of cold source and heat source, and organic fluid type on the enhancement effects are analyzed. The suitable scenarios for adding IHE in SDORC are revealed. Results show that adding IHE can effectively enhance the thermo-economic performance of SDORC at a sufficiently high heat source temperature, and the specific investment cost will be reduced by 3.9%. Adding IHE is also effective in enhancing the thermodynamic performance of SDORC for heat sources with outlet restraint, with a net power growth of 6.1%. For SDORC, adopting IHE fits better in the application scenarios with high heat source temperature, restrained outlet temperature, corrosive fluids, and large molecular complexity of organic fluid. The enhancement effects are more significant.

A parametric study of a renewable energy based multigeneration system using PEM for hydrogen production with and without once-through MSF desalination

The importance of renewable energy compared to fossil fuels is increasing due to growing energy demand and environmental challenges. Multi-generation systems use one or more energy sources and produce several useful outputs. The present study aims at investigating and comparing solar energy based multi-generation systems with and without once-through MSF desalination unit from the thermodynamic point of view. Firstly, hydrogen, electricity, and hot water for space heating and domestic usage are produced using the system, which consists of a parabolic trough collector, an organic Rankine cycle (ORC) and a PEM electrolyzer and heat exchanger as sub-systems. The performance of the entire system is evaluated from the energetic and exergetic points of view. Various parameters affecting hydrogen production rate and efficiency values are also investigated with the thermodynamic model implemented in the Engineering Equation Solver (EES) package. The system can produce hydrogen at a mass flow rate of 20.39 kg/day. The results of the study show that the energy and exergy efficiency values of the ORC are calculated to be 16.80% and 40% while those for the overall system are determined to be 78% and 25.50%, respectively. Secondly, once-through MSF desalination unit is integrated to the system between ORC evaporator and heat exchanger producing domestic hot water in the solar cycle in order not to affect hydrogen production rate while thermodynamic values are compared. Fresh water production capacity of the system is calculated to be at a volumetric flow rate of 5.74 m3/day with 10 stages.

Analysis of organic Rankine cycle integrated multi evaporator vapor-compression refrigeration (ORC-mVCR) system

In this study, a multi evaporator vapor-compression refrigeration (mVCR) system driven by Organic Rankine Cycle (ORC) is proposed as a refrigeration system for supermarkets, restaurants, etc. The system is analyzed for its thermodynamic performance in terms of coefficient of performance (COPs) and exergetic efficiency (ηex). A zeotropic mixture of hexane and R245fa is used as working fluid over pure fluid to assess its impact on the thermodynamic performance of the system. Moreover, the system is optimized using an evolutionary algorithm called genetic algorithm (GA) to determine the optimal values of the operating parameters for the maximum exergetic efficiency of the system. The results indicate that COPs and ηex are maximum at the mass fraction of 0.5 of the zeotropic mixture. The maximum values of COPs and ηex are 0.425 and 31.1% respectively. The system can achieve an exergetic efficiency of 58% at the optimal set of operating parameters. The corresponding optimal values of the temperature of the ORC evaporator, VCR evaporator 1, VCR evaporator 2, and the condenser are 388 K, 268 K, 268 K, and 303 K respectively.

Automated configuration of organic Rankine cycle system based on process simulations

In organic Rankine cycle (ORC) system, the selection of the structure and the optimization of operating parameters are usually studied separately, which makes the existing design principles inadequate to describe the impacts of the structure on ORC performance, and thus greatly limits its practical applications. To this end, this paper addresses an automated scheme for the optimal configuration of the ORC system, aiming to simultaneously determine the working fluid, the structure and the operating parameters corresponding to the maximal system efficiency. In this work, a comprehensive simulation and optimization of four common ORC structures is first conducted with 18 working fluid candidates and the most common heat sources with the inlet temperature ranging at 200–120 °C. The influence mechanisms of the ORC structure on the thermodynamic performance of the ORC system are then explored to generalize the qualitative and quantitative principles for ORC configuration. Results show that, for the single-pressure evaporation ORC (SPC) with a given inlet temperature of the heat source, the Pinch point type formed by the working fluid and the heat source changes from vaporization Pinch point (VPP) to VPP&PPP (preheat Pinch point) and then to PPP as the critical temperature of the working fluid decreases. The system efficiency of SPC reaches its maximum when the double Pinch point of VPP and PPP is formed and double-pressure evaporation ORC (DPC) reaches its maximum system efficiency when the double Pinch points of HVPP and LVPP are formed. Besides, it is found that when compared with the basic ORC, the regenerative ORC enables to improve the thermal efficiency and system efficiency of the system at the same time, whereas the bleeding regenerative ORC increases the thermal efficiency while reduces the system efficiency. For the DPC, the type of Pinch point formed by the heat source and the working fluid in the optimal working condition is the key to determine whether a system has multiple evaporation potential. Specially, for the heat source with variable inlet temperature, a linear relationship between the inlet temperature of the heat source and the critical temperature of the working fluid can be established to determine the multiple evaporation potential of a certain working fluid. Based on these results, an automatic scheme for ORC configuration is developed and expected to provide an effective guidance for the selection of working fluid, configuration optimization and parameter determination of the actual ORC heat recovery process.

Energy production and storage from a polygeneration system based on parabolic trough solar collector, proton exchange membrane fuel cell, organic Rankine cycle, and alkaline electrolyzer

Due to the limitations with fossil fuels consumption, it is necessary to pay more attention to clean energy sources such as solar energy. Using solar energy systems as a driven of hybrid systems and integrating with an energy storage technology can alleviate some of the problems. In the present paper, a novel solar driven-polygeneration energy system with electrical energy storage is introduced and investigated. The cycle power generation section is composed of parabolic trough collector field, proton-exchange membrane fuel cell, organic Rankine cycle, alkaline electrolyzer, and thermoelectric generator. The light energy of the sun is converted into thermal energy by the solar collector. This thermal energy prepares the necessary thermal duty of the organic Rankine cycle's evaporator. Then, the electricity generated by the organic Rankine cycle is used to electrify an electrolyzer. The oxygen and hydrogen obtained from electrolyzer are used to generate power and heat by the fuel cell. Then, the waste heat of the fuel cell goes to the hot end of the thermoelectric generator and electricity is generated. The electricity generated from the fuel cell, thermoelectric generator, and surplus of the organic Rankine cycle is stored via a hybrid storage system for times of need (at night, cloudy days and/ or peak consumption hours). Findings revealed that the proposed polygeneration cycle is capable of generating 22.5 kW of power. Furthermore, 140.8 kW of thermal power and 97.3 g/h of hydrogen fuel are generated by the solar collector field and electrolyzer, respectively. Moreover, sum exergy destruction, system efficiency, and net capacity of the storage system are 18.83 kW, 60.3%, and 89 m3, respectively. Three different scenarios are considered for the solar field design based on the determined collector numbers.

Synthesis and simultaneous optimization of multi-heat source multi-pressure evaporation organic Rankine cycle with mixed working fluid

The organic Rankine cycle (ORC)’s performance relies on heat source properties, cycle structures, and working fluids. Influences of these factors, however, are often interdependent, making it difficult to determine the optimal design of ORC systems. To address this issue, we propose a mixed-integer nonlinear programming model for the multi-pressure evaporation ORCs driven by multiple heat sources that not only optimizes operating conditions, but also identifies the best working fluid composition and cycle structure. Results demonstrate that the proposed model is accurate and effective. The dual-pressure evaporation ORC driven by multi-heat source shows a 10.87% rise in the net power output (NPO) compared to the one with single pressure evaporation. In general, 0.9/0.1 n-pentane/n-heptane is the optimal mixed working fluid generating 2.71–12.11% more power than the pure working fluids for the numerical studies. Dual-pressure evaporation ORC is found to be a balanced design for the multi-heat source driven ORC in terms of its NPO and cycle complexity.

Integrated Vapor Compression Chiller with Bottoming Organic Rankine Cycle and Onsite Low-Grade Renewable Energy

The present study offers a scheme to improve the performance of existing large-scale chillers. The system involves raising the temperature of the chiller’s cooling water stream using renewable energy sources by incorporating an organic Rankine cycle (ORC). The thermal analysis was conducted by raising the temperature of one-third of the approximately 200 ton chiller’s cooling water. The investigation was considered for ORC evaporator inlet temperature of 90~120 °C by the step of 10 °C. Various working fluids for the different ORC evaporator inlet temperatures were examined. Sensitivity analyses conducted on the degree of superheating, degree of subcooling, condenser saturation temperature, pinch point temperature differences of the ORC evaporator and condenser, and the mass flowrates of the heating and cooling streams were also reported. Genetic algorithm was employed to carry out the optimization. The best options for the ORC working fluid at the heating source ORC evaporator inlet temperatures of 90 °C was found to be DME, presenting an improvement of 48.72% in comparison with the rated coefficient of performance (COP) value of the VCC, with a renewable energy input requirement of 710 kW. At the heat source temperatures of 100 °C and 110 °C, butene, which presented an improvement in the COP equal to 48.76% and 68.85%, respectively, with the corresponding renewable energy requirements of 789.6 kW and 852 kW, was found to be the ideal candidate. Meanwhile, at the heat source inlet temperature of 120 °C, R1233zd (E), representing an improvement of 140.88% with the renewable energy input of around 1061 kW, was determined to be the most favorable ORC working fluid candidate.