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To mitigate costs and minimize environmental repercussions, integrated electric ship (IES) are an attractive option for developing greener, more efficient ships. Nevertheless, the service load uncertainty and the ineffective utilization of low-grade energy from diesel generators will hinder ships from attaining economical and low-carbon operation. Hence, an IES optimal joint scheduling model combining particle swarm optimization (PSO), waste heat recovery (WHR), and Latin hypercube sampling (LHS) is proposed. In this study, the mathematical modeling and reliability verification of the system are carried out, the performance of WHR is optimized, and the energy saving and emission reduction benefits of the combined system in IES's joint scheduling are explored. Simulation results illustrate that the innovative WHR integrated system can concurrently supply power, cooling capacity, and fresh water for IES, and the system yields 81.16 tons of fresh water during a single voyage. Finally, compared with Case 2, Case 1, which employs the transcritical CO 2 Rankine cycle and combined cooling and power system, reduces operating costs and CO 2 emissions by 2.3 % and 3.86 %, respectively, providing that the strategy proposed is effective in the IES's joint scheduling. [Display omitted] • A new energy recovery system is proposed to integrated electric ship joint scheduling. • The particle swarm algorithm is utilized to optimize the energy recovery system. • Latin hypercube sampling is applied to simulate uncertain scenes of service load. • The costs and CO 2 emissions of integrated electric ship decrease by 2.3 % and 3.86 %. [ABSTRACT FROM AUTHOR]

Liquid air energy storage is an efficient and clean energy storage technology. This paper studies an advanced integrated energy system that couples biomass and liquid natural gas complementary energy supply with liquid air energy storage. The system mainly includes two-stage organic Rankine cycle, liquid air energy storage, and gas-steam combined cycle. Adaptive genetic algorithm is used to perform the multi-objective optimization of the system's thermodynamic parameters. Under optimal configuration, the system undergoes exergoeconomic and exergy carbon evaluations. The impact of the mixed burning ratio, steam turbine pressure parameters, compressed air utilization rate, and fuel prices on the exergoeconomic and exergy carbon performance of the system is analyzed. Optimization results show that the system performs best with the mixed burning ratio of 0.44, maximum pressure parameters, and maximum compressed air utilization rate, achieving the unit exergy cost of 0.1674 $ (kWh exergy)−1 and the unit exergy carbon intensity of 0.362 kg CO 2 -eq (kWh exergy)−1. Sensitivity analysis shows that as the mixed burning ratio increases from 0 to 1, the exergy cost of the product rises from 0.0775 to 0.2905 $ (kWh exergy)−1. In contrast, the exergy carbon intensity decreases from 0.492 to 0.211 kg CO 2 -eq (kWh exergy)−1. • A novel LAES system with two-stage ORC is proposed. • The waste heat and liquefied natural gas cooling energy are fully utilized. • The thermodynamic parameters are optimized under multiple objectives. • Two optimization algorithms are proposed and compared. • Sensitivity analysis is conducted based on decision variables and fuel prices. [ABSTRACT FROM AUTHOR]

Supercritical carbon dioxide (sCO 2) cycle has high efficiency and fast response as load changes. It is important to examine whether the sCO 2 cycle is suitable in arid area. Hence, we explore the effect of air-cooler and water-cooler on the performance of a 300 MW sCO 2 coal fired generation system. Flow and heat transfer models were established for air-cooler and water-cooler. The later includes shell-tube-heat-exchangers and a cooling tower. We show a 0.8 % efficiency drop using air-cooler instead of water-cooler, at an air temperature of T a = 20 °C, which increases as T a rises. The increased temperature of sCO 2 and exergy destruction in air-cooler explain the efficiency penalty. Compared with cooling conditions for water-steam Rankine cycle, larger temperature difference exists in ∼30 K level between sCO 2 and cooling fluids, explaining weaker efficiency penalty for sCO 2 cycle. Besides, the usage of air-cooler creates a 3.66 million RMB cost reduction than water-cooler. The raised cost of shell-tube-heat-exchangers for the water-cooler accounts for cheaper construction of the air-cooler. Based on this study, the air-cooler induces mini efficiency drop and reduced cost, it is concluded that for sCO 2 cycle it is preferable to use the air-cooler, which is benefit to save the water resource in arid area. • Steady state model of a 300 MW sCO 2 coal-fired system with water-cooler and air-cooler is developed. • The performance and cost of the sCO 2 power generation with water-cooler and air-cooler are compared. • The efficiency penalty of sCO 2 cycle with air-cooler is explained, which is minor than which of water-steam Rankine cycle. • It's concluded that for sCO 2 cycle it is preferable to use the air-cooler, which is benefit to save the water in arid area. [ABSTRACT FROM AUTHOR]

Conventional carbon capture technologies utilized in SOFC-based distributed energy systems significantly elevate energy consumption and costs. To address the challenges, this study presents a concept of collaborative water-gas-shift membrane reactor (WGSMR) and oxy-fuel combustion technologies, and pioneers an engineering case to demonstrate its feasibility. By integrating the Rankine cycle, double-effect LiBr absorption chiller, multi-effect distillation unit and CO 2 capture plant, waste heat and materials from the prime mover unit are effectively recovered. A comparative analysis of cases with and without WGSMR is conducted to explore its performance improvement potential and mechanisms, while a techno-economic-environmental analysis is performed to comprehensively evaluate the performance of the WGSMR-integrated case. Under the design conditions, the system attains energy and exergy efficiencies of 79.08 % and 30.71 %, with corresponding levelized costs of products and global warming potential of 45.08 $/GJ and −0.21 kg/kWh. At an operating temperature of 700 °C and a current density of 3464 A/m2 of SOFC, the system achieves the minimum levelized cost. Compared with the case without WGSMR, the results demonstrate that the exergy and electrical efficiencies are improved by 2.39 % and 0.95 %, while the levelized cost of products is decreased by 5.29 $/GJ for the case with WGSMR. • Collaborative WGSMR and oxy-fuel combustion technologies for CO 2 capture. • Effectively recovering waste heat and materials from the SOFC-based energy system. • Evaluating the environmental impact of the system from a lifecycle perspective. • Elucidating the mechanisms of WGSMR for enhancing system performance. • Addressing the high expenditures and energy consumption of conventional methods. [ABSTRACT FROM AUTHOR]

The traditional classification of working fluid, which is based on the characteristics of saturated vapor curve in temperature-entropy (T-s) diagram, focuses more on the output power of organic Rankine cycle (ORC). The performance of an ORC is greatly influenced by pump power consumption, which is closely related to the subcooled region and saturated liquid curve of the working fluid. This paper proposes a new classification method of working fluids, which simultaneously considers the curved triangle area in subcooled region (A 1), the slope of saturated liquid curve (k), and the pump power consumption (w p). It is discovered that dry working fluids have a larger area of curved triangle in subcooled region and higher pump power consumption compared to isentropic working fluids. Among all the dry or isentropic working fluids studied, halogenated hydrocarbons have the steepest slope of saturated liquid curve. The more silicon in siloxane, the larger the values of A 1 and k , however, the smaller the value of w p. On this basis, the ratio of the curved triangle area in subcooled region (A 1) to the curved triangle area in superheated region (A 2), which is (A 1 :A 2), is used to evaluate the working fluid characteristics. Additionally, the ratio of the net output power (w net) to the condenser load (q c), which is (w net : q c), is used to evaluate the ORC performance. It can be determined that D5 (decamethylcyclopentasiloxane) and MD4M (tetradecamethylhexasiloxane) may be the essential working fluids for future ORC design and operation. • A new classification method simultaneously considering three indicators is proposed. • Pump power consumption of dry fluids is larger than that of isentropic fluids. • The slope of saturated liquid curve of halogenated hydrocarbon is the largest. • D5 and MD4M may be the essential working fluids for future ORC development. [ABSTRACT FROM AUTHOR]

In the essay, a waste-to-energy system architecture consisting of plasma gasification, waste tire pyrolysis, gas turbine cycle, HRSG, and steam turbine cycle is proposed. In the hybrid configuration, the syngas from the conversion of medical waste in the plasma gasifier enters the combustion chamber for further utilization. Meanwhile, waste tires are subjected to pyrolysis reaction in the reactor, which produces pyrolysis carbon and pyrolysis oil that are valuable in the chemical industry, machinery, and energy, and selling them can bring significant economic benefits. The generated pyrolysis gas is conveyed to the combustion chamber, serving as the primary fuel source for the combustion process. The flue gas from combustion enters the gas-steam combined cycle and drives generators to produce electricity. An analysis of the thermodynamics and techno-economics of this hybrid configuration is conducted, leveraging simulation outcomes as a foundation. The thermodynamic assessment reveals an energy efficiency of 66.68 % and an exergy efficiency of 74.40 %, indicating substantial performance. The techno-economic evaluation underscores the viability of the scheme, with a swift dynamic payback period of 3.35 years and a positive net present value of 179295.12 k$. Collectively, these findings underscore the favorable nature of this novel design, both thermodynamically and economically. • The work presents a waste-to-energy system architecture consisting mainly of plasma gasification and waste tire pyrolysis. • The energy efficiency of the system can reach up to 66.68 %. • The exergy efficiency of the system can reach up to 74.40 %. • The dynamic payback period is only 3.35 with a net present value of 179295.12 k$. [ABSTRACT FROM AUTHOR]

Turbine modeling plays a critical role in assessing system power output and performance in CO₂ transcritical power cycle (CTPC) systems, particularly under dynamic operating conditions. Conventional turbine models often fail to provide accurate predictions when inlet parameters deviate from the design point, leading to discrepancies in system behavior. This paper introduces a novel methodology by integrating a Pham-based corrected turbine performance map into a regenerative CTPC dynamic system. This approach enhances turbine modeling accuracy compared to traditional models, such as the uncorrected turbine performance map, nozzle model, and empirical model. The proposed Pham-corrected model method improves system response stability, particularly in terms of inlet pressure and CO₂ mass flow rate under heat source temperature reductions, offering more reliable performance predictions. In contrast, the empirical model shows substantial deviations in net power output (32 kW or 4.0 %) and thermal efficiency (1.36 %), leading to longer system stabilization times. The Pham-corrected and uncorrected turbine performance map models exhibit similar responses under cooling water mass flow rate reductions but diverge in turbine inlet pressure trends compared to the nozzle and empirical models. Additionally, the uncorrected turbine performance map model shows significant deviations in net power (25.6 kW or 3.17 %) and thermal efficiency (0.5 %) under a 10 % reduction in pump speed. This study highlights the importance of correcting turbine inlet parameters and addressing prediction deviations in conventional models. The Pham-corrected turbine model improves reliability, performance prediction, and design optimization, especially under fluctuating heat sources. With its potential to enhance system stability and efficiency, this methodology offers significant prospects for future CTPC applications, including waste heat recovery and renewable energy integration. • Integration of the Pham-corrected turbine model improves the dynamic accuracy of CTPC. • Comprehensive analysis of CTPC system responses to external disturbances. • Comparative evaluation of Pham-corrected and traditional turbine models in dynamic performance. • Pham-corrected model reveals discrepancies in dynamic responses of conventional turbine models. [ABSTRACT FROM AUTHOR]

The primary aluminum industry dissipates more than 50 % of its energy as waste heat. This study delves into an innovative application of the Double-Pressure Organic Rankine Cycle (DPORC) to recover waste heat from flue gases and smelter sidewalls, employing both high-temperature (HT) topping and low-temperature (LT) bottoming cycles. The research aims to assess its technical and economic viability. The study investigates operational considerations, such as intermediate pressure and working fluid type, with economic factors to evaluate both the thermodynamic and economic performance of the system. The findings reveal notable improvements in power output and exergetic efficiency by leveraging two distinct heat sources within the DPORC framework. Integrating an LT bottoming cycle yields a notable 33 % increase in thermal efficiency. Economic analysis underscores substantial efficiency gains and financial returns compared to conventional ORC setups, with the DPORC achieving a maximum net output power increase of 2844 kW, varying between 7200 kW and 7310 kW across various scenarios. Moreover, by assessing the temperature range of both heat sources and introducing a pre-heater, further performance enhancements were noted. Furthermore, the DPORC system demonstrates a considerably shortened payback period of 0.44–0.5 years, enhancing its economic appeal. This research underscores the potential of the DPORC for efficient energy recovery and economic viability in industrial waste heat applications, paving the way for future advancements in two-stage ORC systems. • DPORC recovers 50 % waste heat from aluminum smelters, boosts power. • DPORC nets 2844 kW increase, outpacing single ORC setups. • Pay-back period slashed to 0.44–0.5 years with implementing DPORC. • Economic analysis favors DPORC for integrated sources waste heat. • Two-stage ORC systems show promise for industry waste heat recovery. [ABSTRACT FROM AUTHOR]

In the underwater environment, a nuclear-powered CO₂-based transcritical recuperative power cycle can effectively utilize the low temperature of seawater to achieve high-efficiency. To address the challenge of non-condensable working fluids in the epipelagic zone, a self-condensing subloop offers an effective solution. This study introduces a configuration for a self-condensing CO₂-based transcritical recuperative power cycle, establishes a thermodynamic model, investigates the negative impacts of the self-condensing subloop, and analyzes its operational strategies at various underwater depths. Results indicate, when CO₂ can condense in the cooler, the subloop consumes between 17.4 % and 36.9 % of generated power, which decreases as seawater temperatures rise at a cooler pressure of 8.5 MPa. Since the high heat capacity of the heat source, increasing turbine inlet temperature and pressure significantly improves system efficiency. Activation of the self-condensing subloop enhances power output with higher storage tank temperatures. Furthermore, when seawater temperatures exceed 23.4 °C, a linear functional relationship between seawater temperature and optimal cooler pressure is specifically proposed, which effectively optimizes system power output. The study recommends activating the self-condensing subloop when CO 2 at cooler outlet exceed 28 °C, broadening applicable temperature range of transcritical power cycle systems in the ocean. Methods in this research include first-principle modeling and optimization. • Numerical simulation of self-condensing carbon dioxide transcritical recuperative power cycle system(SC-CTRC) is applied. • An optimal relationship between the cooler pressure and seawater temperature is proposed to maximum the power output. • Parameter analysis reveals the impact of varying parameters in self-condensing subloop on overall system performance. • The proposed models improve system's adaptability at different depths where the cooling temperatures vary from 4°C to 31°C. [ABSTRACT FROM AUTHOR]

In the field of isolated island energy supply, the OTEC system is considered promising due to its large storage capacity, and pollution-free characteristics. To improve energy efficiency, polygeneration systems have gradually become a research hotspot for their low cost and high return features. In this context, a novel Ocean Thermal Energy Conversion system integrated with an air conditioning unit (OTEC-AC) is introduced, demonstrating capabilities in electricity, cooling capacity, and fresh water production by experiments. The effects of various flow rates and temperatures of the heat and cold sources, along with the air-conditioning system water flow rate on the system performance is explored. Besides, the overall performance of the OTEC-AC is compared with four representative OTEC models. The results indicate that there is a threshold for the influence of cold and heat source flow rate on the performance of power generation system. The OTEC-AC system shows a highest net power of 132.6 W, cooling capacity of 2.14 kW, condensate production of 3.24 kg/h, and achieves a system exergy efficiency and CO 2 reduction of 34.7 % and 5801 kg/year, respectively. The annual CO 2 reduction per kilowatt of installed capacity of the system is increased by 135.6 %, compared with the conventional OTEC system. • A novel experimental OTEC – AC system has been constructed. • Effect on flow rates and temperature of heat and cold sources are examined. • There is a threshold effect of heat and cold sources flow rate on thermal cycling. • Energy, exergy and environment analysis on the system performance is carried out. • The overall system performance is 135.6 % higher than the traditional OTEC system. [ABSTRACT FROM AUTHOR]

This study investigates the application of organic Rankine cycle (ORC) on ships to reduce fuel oil consumption and assess improvements in the Energy Efficiency Existing Ship Index (EEXI), and carbon intensity indicator (CII). A cascade ORC(C-ORC) configuration is designed to utilize the exhaust gas from a diesel engine. Thermodynamic simulation identified a combination of toluene and R1233zd as the optimal working fluids for the C-ORC. Exergy analysis was conducted to evaluate the performance difference between the C-ORC system and a version with an internal heat exchanger (C-IHX ORC). The results showed a maximum exergy efficiency of 56.78 % for the C-IHX ORC, compared to 49.33 % for the C-ORC. Further evaluations of the C-IHX ORC, including fuel savings, energy generation, EEXI, and CII, demonstrated that average vessel fuel consumption decreased by 1.02 %, and average attained EEXI improved by 0.93 %. Additionally, the attained CII value was enhanced by 0.98 % on average, depending on operating loads and traveled distances. Although the improvements of EEXI, and CII offered were modest, they present the potential for further enhancement through the utilization of additional waste heat sources, such as economizer steam, and jacket cooling water. • Identified toluene and R1233zd as optimal working fluids for the derived C-ORC application. • Demonstrated energy and exergy efficiency of 20.16 % and 56.78 % with C-IHX ORC. • Achieved average fuel consumption reduction by 1.02 % and improved EEXI by 0.93 %. • Investigated potential attained CII rating improvements by 0.98 % with C-IHX ORC. • Highlighted the potential of ORC for enhancements using additional waste heat sources. [ABSTRACT FROM AUTHOR]

Combined flash binary geothermal cycle (CFBGC) is an efficient geothermal energy conversion technology. Natural gas (NG) is a preferred fuel in the current energy scenario. LNG gasification is a needed step for delivering NG among the end users. In the present study, a self-superheated single-flash geothermal steam cycle, a transcritical CO 2 power cycle and an LNG gasification unit are integrated into a CFBGC. This study shows that the LNG gasification rate and power output can be increased simultaneously by increasing the steam turbine inlet pressure. At a higher steam turbine inlet pressure, desirable steam quality (i.e., 0.9) at the steam turbine exit is maintained by implementing self superheating of the steam. It is observed that 15 °C DSH of steam enables the CFBGC to operate at a steam turbine inlet pressure that substantially enhances the output power without a noticeable increase in levelized electricity cost (LEC). The CFBGC operating at this condition yields 9.97 % higher power output compared to that of the CFBGC operating at steam turbine inlet pressure requiring no DSH of steam. As a geothermal-based power plant emits very low CO 2 , the proposed energy system may emerge as a future sustainable energy option. • A novel combined flash binary geothermal cycle is proposed. • Self –superheated single flash steam cycle is integrated with a T-CO 2 power cycle. • LNG gasification unit is employed as the heat sink of the T-CO 2 power cycle. • Increasing steam turbine inlet pressure enhances power output and LNG gasification rate. • Self-superheating ensures desired steam quality at the steam turbine exit. [ABSTRACT FROM AUTHOR]

Optimisation is drawing more and more attention in the organic Rankine cycle (ORC) research field. However, as the complexity of the ORC scenarios increases, it poses challenges on operational parameter, working fluid, and configuration optimisation levels. This work first proposes an improved optimisation method, termed the One-shot Optimisation (OSO) method, which can simultaneously optimise the working fluid and configuration. Then, a two-objective optimisation is performed using the OSO method in combined ORC–LNG systems, considering up to eight operational parameters, 11 working fluids, and 16 system configurations to maximise energy efficiency and minimise the electricity production cost (EPC). Finally, the result of the optimisation is divided according to the thermodynamic weight (W 1), and two typical conditions are analysed in detail: the maximum case (W 1 = 1) and the balanced case (W 1 = 0.5). The results show that the OSO method is capable of identifying the optimal working fluid and optimal configuration within a single optimisation process. The basic ORC configuration is preferred when W 1 is lower while the recuperative ORC is preferred when W 1 is higher. The balanced case can achieve an energy efficiency comparable to that of the maximum case but with a significantly lower EPC. The balanced case can achieve as much as 87. 48% of energy efficiency, requiring only 19.77% of the EPC compared to those of the maximum case. • The time complexity of the OSO method can greatly reduce the optimisation efforts. • 8 operational parameters are included as the optimisation variables. • 11 working fluids and 16 configurations are optimised within a single optimisation. • Two typical operating conditions are analysed and compared. • The balanced case can achieve 87.48% of the energy efficiency, requiring only 19.77% of the EPC. [ABSTRACT FROM AUTHOR]

The energy-saving capabilities and efficient operation of marine low-speed diesel engines (MLDE) is a key emphasis for the main power source for ocean transportation. The purpose of the supercritical carbon dioxide recompression Brayton cycle (SCRBC) is to capture and utilise waste heat emitted by the engine's exhaust gas. However, the SCRBC performance will be severely affected by the large temperature fluctuations of ocean-going vessels during operation and high ambient temperatures in the cabin. A SCRBC model was built using the exhaust gas test data as the boundary conditions and validated using the Sandia National Laboratory (SNL) test data. The physical characteristics of the working fluids were evaluated by adding other fluids to CO 2 in specific proportions to modify the critical point and increase cycle efficiency. The results demonstrated that employing CO 2 -based binary working fluids with low alkane and hydrogen sulfide (H 2 S) enhanced the recovery power, with the most significant increase obtained by the addition of 16.48 % H 2 S, which increased the power by 9.72 kW and improved the Brayton cycle efficiency by 3.31 %. Compared to the MLDE at 100 % load, the total efficiency increased by 1.77 % and the BSFC decreased by 6.76 (g kW−1 h−1) using CO 2 -H 2 S as the working fluid. The analysis of the SCRBC system component exergy losses showed that the cooler had the highest exergy losses. Adding other fluids to CO 2 reduced the exergy losses of each component with the SCRBC system exergy losses decreasing from 162.97 to 129.90 kW and the exergy loss efficiency decreasing from 24.24 % to 22.65 %. The use of CO 2 -based binary working fluids specifically designed for ambient temperature may be expanded to other engines to enhance the efficiency of waste heat recovery. • Optimizing the SCRBC for marine low-speed engines by adding CO 2 -based mixing medium. • The compressor inlet temperature is controlled by the CO 2 -based binary mixed working fluids. • The composition of CO 2 -based binary mixture was selected optimize the cycle efficiency. • With 16.48 % H 2 S added, the Brayton cycle efficiency was improved by 3.31 % in 310K. • The exergy losses of each component were reduced by the addition of other fluids to the CO 2. [ABSTRACT FROM AUTHOR]

To enable the widespread exploitation of intermittent, low-cost, and non-dispatchable renewable energy technologies, energy storage plays a key role in providing the required flexibility. This study introduces maps of optimal combination of Thermal Energy Storage (TES) and power cycles, supporting decision-making in power-to-heat-to-power applications. These maps span a wide temperature range from 200 to 1200 °C and are proposed for different charging costs, installed capacities, and storage durations. For thermal-to-electricity reconversion, this study explores power blocks including steam Rankine cycle, supercritical CO 2 (sCO 2) Brayton cycle, Organic Rankine Cycle (ORC), and combined gas turbine with Rankine and sCO 2. Results highlight that, in a grid-based plant with a 50 EUR/MWh charging cost, the most cost-effective pairing involves sCO2 cycles with recompression and intercooling, with particle TES at 600–800 °C. Air packed-bed suits scenarios where TES contributes significantly to capital costs or involves low charging costs. Molten salt TES is the optimal choice when the design temperatures align with salt temperature limitations. Particle TES proves cost-effective across a broad temperature range and scales (10–200 MW). For solar-based systems, the integration of molten salt TES with simple sCO2 recuperated cycles demonstrates market potential for southern European locations. • Mapping optimal TES and power cycle coupling for heat source at 200–1200 °C. • Aiding decision-making for power-to-heat-to-power applications. • Impact of charging costs, installed capacities, and storage hours on optimal maps. • Grid Carnot battery with 12 h of particle TES and sCO 2 cycle yield 160 EUR/MWh. • Solar Carnot battery with 6 h of molten salt TES and sCO 2 cycle yield 125 EUR/MWh. [ABSTRACT FROM AUTHOR]

The ambitious green revolution to renewable energy sources in global power grids necessitates massive integration of solar and wind energy, which involves intermittent and unpredictable challenges. Thermal power plants are crucial in stabilizing the grid and addressing these challenges through flexibility reformation including deep peak shaving and frequent load variations since the unsteady state energy transfer and thermal dynamics during combustion and heat transformation in thermodynamic processes vary significantly. These conditions lead to issues such as furnace instability and latent heat of phase transition. This study introduces a novel approach to modeling phase transitions of supercritical steam cycle, and investigatesthe length, position, temperature, and energy transfer of the working medium and components under normal and low operational states. Conducting and analyzing the thermal feasible region associating the security of components and working medium this study establishes a control strategy for dynamic heat transfer to reduce component degradation effects andenhance load variation rate under flexible operations. Simulation model of a supercritical power unit based on the proposed method demonstrates an accuracy of 97.94%. Results from the optimal approach in maximizing load variation rate show the effectiveness and achieve 1.2%p.e./min most under transition process. • A dynamic modeling of supercritical coal fire plant focusing on steam cycle is deployed. • Critical components are examined to characterize the gasification latent heat. • The state equation is established to conduct the feasible region associating security margin. • A model predictive control strategy is proposed to enhance the load variation rate. [ABSTRACT FROM AUTHOR]

This research investigates the multi-objective optimization of a geothermal-driven multi-generation system designed to produce liquid hydrogen and oxygen as its primary outputs. The system incorporates a Proton Exchange Membrane (PEM) Electrolyzer alongside a modified ejector-based Organic Rankine Cycle to generate the required Energy (heating bar, cooling bar, electricity and hydrogen). Case studies were conducted in three distinct locations: Zanjan in Iran, Aarhus in Denmark, and San Bernardino in the United States, utilizing actual geological and meteorological data for accuracy. Simulations were executed applied Engineering Equation Solver & optimization of the system was carried out to enhance performance by focusing on the objective functions of system exergy efficiency and cost reduction. This was accomplished by utilizing response surface methodology (RSM) along with Minitab software (MS).To optimize the system, six decision variables were identified as critical parameters influencing performance. The optimization results indicated that the system can achieve an exergy efficiency of 53.74 % while maintaining a cost rate of $31.56 per hour. The overall cost rate for the geothermal system was determined to be $54.50 per hour, with $10.10 per hour allocated to hydrogen production and $44.40 per hour to electricity generation. Site-specific analyses highlighted San Bernardino as the most favorable location for implementing this system, projecting an annual production of 90.8 tons of liquid hydrogen and 208.3 kg of oxygen. In August, the geothermal system in San Bernardino can produce up to 7691.6 kg/h of liquid hydrogen, while in December, production decreases to 7402.8 kg/h, marking the lowest output for the year. In contrast, Zanjan and Aarhus demonstrated lower production capacities, underscoring the system's feasibility as dependent on site-specific conditions. • A new Co-generation energy system. • Production of Liquid Hydrogen. • Response surface method as a machine learning. • Forecasting-Multi Objective Optimization. [ABSTRACT FROM AUTHOR]

Due to the damage they have caused to the ozone layer, first-generation refrigerants known as chlorofluorocarbons have been phased out, and second-generation refrigerants known as hydrochlorofluorocarbons are being phased out. Third-generation refrigerants known as hydrofluorocarbons are also being phased out due to their high global warming potential. As successors to the above three generations of refrigerants, hydrofluoroolefins and hydrochlorofluoroolefins were designed and created in laboratories. They have been attracting increasing research interest because they are safe and environmentally friendly. In this paper, various aspects of the recent research on hydrofluoroolefin and hydrochlorofluoroolefin refrigerants, including applications in refrigeration systems and heat pump systems, applications in organic Rankine cycles, flow patterns and heat transfer characteristics, thermophysical properties, persistent degradation product, toxicity, flammability and ignitability, thermal stability and decomposition mechanisms, are reviewed and discussed. The most commonly studied hydrofluoroolefins are still HFO-1234yf and HFO-1234ze(E). HFO-1336mzz(Z) is also worthy of further attention because it may be a suitable replacement for HFC-123. Attempts can be made to establish a dedicated equation of state for commonly used hydrofluoroolefins to better predict the thermodynamic properties. Further studies on the persistent degradation product, toxicity, flammability and ignitability, thermal stability and decomposition mechanism are needed. • Applications of HFOs/HCFOs in refrigeration and heat pump systems are described. • Applications in organic Rankine cycle are introduced. • Flow pattern and heat transfer characteristics are analyzed. • Thermophysical properties are discussed. • Some concerns about HFOs are presented. [ABSTRACT FROM AUTHOR]

Scroll expanders are widely adopted in small-scale Organic-Rankine-Cycles-(ORCs)-units integrated with renewable energy sources for low power residential Combined Heat and Power Production (CHP). These expanders are often connected to variable direct loads without the possibility to impose its speed externally. Despite the effect of electric load variation on expander speed is known, a minor attention is focused on its impact on the plant operability and regulation. To fill this gap, a wide experimental analysis is carried out on a solar micro-cogenerative ORC-based power unit equipped with a 1 kW hermetic scroll expander connected with a variable electric load. The experimental behaviour of the ORC-unit was assessed for different values of load resistance (from 20 Ω up to 80 Ω). Results show that properly acting on the load resistance the ORC-power unit can be improved up to 50 % in terms of efficiency and power production. Moreover, if the expander is properly designed its self-regulatory capability allows to achieve similar performance of an equivalent speed-controlled expander tested on the same plant. Finally, a new theoretical model reproducing the impact of main operating quantities on expander behaviour was developed and experimentally validated paving the way to a novel model-based control approach. • Assessment of load variation on Organic Rankine Cycle (ORC)-unit performance. • Experimental analysis of ORC unit varying load resistance and mass flow rate. • Experimental comparison between controlled and uncontrolled expander speed. • Power and efficiency 50 % improve with a proper set of operating parameters. • Development of an experimentally validated theoretical tool for ORC-unit control. [ABSTRACT FROM AUTHOR]

The Organic Rankine Cycle (ORC) is a widely-used waste heat recovery approach, that converts low-grade heat into shaft work. This paper introduces a graphical methodology using Exergy-Enthalpy (Ex-H) diagrams, for evaluating and designing ORCs. ORC thermodynamics can be represented by approximate triangular exergy profiles without compromising accuracy. The exergy profile of the heat-absorbing process is crucial to ORC performance. Approximate triangular exergy profiles can be constructed for any ORC configuration to predict ORC performances, such as work output, exergy loss, and thermal efficiency. Furthermore, a systematic graphical approach is developed for integrating waste heat streams and ORCs, with step-by-step procedures outlined. The evolution procedure of the ORC exergy profile can determine working fluid selection and operating conditions. This visually intuitive yet scientifically rigorous tool clarifies the complex relationships between fluids, parameters, and system performance. Two case studies demonstrate the method's effectiveness, confirming it as a valuable tool for ORC design. • A visually intuitive and theoretically robust tool is developed for design of ORCs. • Triangular exergy profiles are constructed to predict key performance metrics. • Two cases validate the accuracy and effectiveness of the Exergy-Enthalpy Diagram. • Simplified ORC designs achieve better performance than complex literature designs. [ABSTRACT FROM AUTHOR]

Organic Rankine Cycle (ORC) integrated systems with heat sources consist of heat exchange processes and thermodynamic power conversion processes. Fully exploring feasible system configuration while considering fluid selection is crucial for enhancing ORC power generation and balancing economic costs. This study innovatively proposes a theoretical framework that decomposes the Rankine cycle into basic thermodynamic processes. The design of system configuration is regarded as the adjustment of the series-parallel relationships of these basic processes, aiming to achieve simultaneous optimization of the cycle structure and the HEN structure, thereby greatly expanded the search space for feasible ORC system configurations. The optimization problem is solved using a bi-level strategy, The outer layer determines the number of thermal power conversion components, operating parameters, and working fluid selection, then provides the associated stream information to the inner layer for optimizing the heat exchange scheme. Applying this method to two different case studies from the literature validated its effectiveness in optimizing scenarios with single and complex heat sources. The Pareto frontier obtained under the conditions of Case I indicates that the investment cost can be reduced by $33.04 k/yr while maintaining the same net power output. In exchange for an increase of $1.51 k/yr in investment cost, the maximum net power output can be improved by 124.74 kW. Under the conditions of Case II, the maximum net output power can increase by 9.71 %–52.5 %, and the Pareto frontier featuring outputs exceeding 50 kW is provided. By analyzing the relative positions of literature schemes and Pareto front within the solution space, the impact of system configuration improvements on the objective functions is explained. These results confirm the effectiveness of the proposed approach for designing optimal ORC energy recovery systems for heat sources. This contribution advances optimization methods for similar closed cycle configurations, which is significant for advancing the utilization of waste heat and addressing sustainability challenges. • A generic multi-stage Rankine cycle structure model has been proposed. • The relationship between heat exchange and thermal power conversion is explained. • Simultaneously optimized the cycle structure and heat exchange network. • Fluid selection and operating parameters are considered as design parameters. • Considered multi-objective optimization of output power and economic cost. [ABSTRACT FROM AUTHOR]

When siloxanes are used as the working fluids of organic Rankine cycle systems, there is a possibility of air infiltration due to the large vacuum present in the condenser. To address this issue, experimental and simulation studies were conducted on the thermal stability and pyrolysis product characteristics of octamethyltrisiloxane (MDM) in the presence of air. The results indicated that air significantly promotes the decomposition of MDM at the temperatures above 250 °C. Air was helpful in increasing the formation of CH 2 O, CO, and CO 2 , and also enhanced polymerization of decomposition product of siloxane, leading to higher yields of MD 2 M, MD 3 M, MD 4 M, D 3 , D 4 , and D 5. By combining reactive force field molecular dynamics (ReaxFF-MD) simulations with density functional theory (DFT) calculations, the microscopic mechanisms of MDM's oxidative decomposition by O 2 in air and H 2 O under humid conditions were elucidated. O 2 can easily combine with unsaturated Si atoms to form Si-O bonds, combine with CH 3 radicals to form C-O bonds, and undergoes hydrogen extraction reactions to initiate decomposition. H 2 O mainly undergoes initial decomposition through CH 3 radical hydrogenation and binding with unsaturated Si atoms. The generated O 2 H, O, and OH radicals tend to bind with Si atoms in molecules and radicals, facilitating polymerization reactions. • The presence of air significantly exacerbates MDM decomposition above 250 °C. • The presence of air promotes the generation of CH 2 O, CO, and CO 2. • The presence of air promotes the formation of D 3 , D 4 , D 5 , MD 2 M, MD 3 M and MD 4 M siloxanes. • O 2 H, O and OH radicals promote siloxane chain elongation and polymerization. [ABSTRACT FROM AUTHOR]

Organic Rankine cycles (ORCs) facilitate the utilisation of low-grade heat sources (e.g., geothermal and industrial waste heat) for power generation, thereby improving energy efficiency in industrial processes and expanding the application of renewable energy. Using multiple ORCs instead of a single cycle provides more flexibility in heat integration and can increase the power output. This paper presents a mathematical model for designing multi-ORC systems; the design task involves the determination of ORC configurations and operating conditions whilst synthesising the associated heat exchanger network. Two case studies on geothermal and industrial waste heat ORC applications illustrate the developed optimisation formulation. In the geothermal case study, the maximum net power output for a single regenerative n-butane cycle can increase by 11.2 % as a result of optimising the ORC operating conditions. With two independent n-pentane cycles, a 7.6 % increase in the maximum net power output can be reached by optimising the ORC configurations. In the industrial waste heat case study, a 14.3 % increase in the maximum net power generation is found with a second n-butane cycle, and a further 5.7 % increase with a third. For comparison, the total annual cost and the payback period are also calculated in both case studies. • An optimisation model for designing multi-organic Rankine cycle systems is presented. • The model allows the selection of configurations and working fluids for each cycle. • The model is applied to case studies considering geothermal and waste heat sources. • Higher power outputs can be achieved through structural and parameter optimisation. • Multi-cycle systems can be more profitable than single-cycle ones in the long run. [ABSTRACT FROM AUTHOR]

The fluctuating heat sources and seasonal condensing environments are critical to the operation of Organic Rankine Cycle (ORC) under off-design conditions. This paper presents a comprehensive steady-state mathematical model developed using a newly built experimental platform. Focusing on the operational characteristics, including the evaporation pressure, condensation temperature, mass flow rate, and the performance of key equipment during the regulation of the expander, working fluid pump, and cooling water pump. Results show that the net efficiency initially increases before decreases, with both evaporation pressure and mass flow rate rising alongside the working fluid pump frequency. The quasi-two-stage single screw expander achieves an isentropic efficiency above 65 %. Additionally, flexible adjustments to the cooling water pump effectively regulate the cooling system, with timely cleaning of cooling pipelines enhancing net efficiency by up to 3.27 %. Optimization using the particle swarm algorithm improves system performance, achieving net efficiency enhancements of 1.8 % and 12.3 % under specific conditions. The novelty of this study lies in directly regulation of the expander, working fluid pump, and cooling water pump, significantly enhancing the off-design performance. This research provides valuable insights for researchers and designers, enabling flexible regulation of ORC operations to ensure efficient performance under varying conditions. • A comprehensive steady-state model of organic Rankine cycle was developed. • The variation rules of optimal working point were explored. • The operating characteristics under various working conditions were analyzed. • The optimal matching relationships among adjustable devices were obtained. [ABSTRACT FROM AUTHOR]

As a mature technology for utilizing surplus exhaust pressure energy, turbo-compounding can significantly redistribute multigrade waste heat in marine two-stroke engines. This paper aims to provide a comprehensive thermodynamic study and design criteria for the combined organic Rankine cycle (ORC) and turbo-compounding system. Firstly, the turbo-compounding system applied to the 6EX340 two-stroke engine and ORC systems designed with double-source and three-source configurations are described. The thermodynamic performance of ORC systems using four working fluids is then analyzed, followed by a thermodynamic and environmental assessment of various combined systems. The results show that utilizing the power turbine bypass results in an additional 10.5 % increase in exhaust energy at the rated condition, while the scavenging air waste energy decreases by around 26.4 % compared to the base engine. For the base engine, the three-source ORC using R245ca shows the greatest potential with a 5.4 % improvement in fuel economy, a CO 2 emissions reduction of 579.7 t, and a payback period of 7.4 years. Further combined with a power turbine, the double-source ORC using toluene as the working fluid outperforms the three-source ORC, resulting in a 9.3 % improvement in fuel economy, a CO 2 emission reduction of 950.6 t, and a payback period of 4 years. • The influence of the power turbine bypass on the waste energy distribution was quantified. • Thermodynamic performance of the organic Rankine cycle system recovering multigrade waste heat was investigated. • Fuel-saving potential of different combined cycle power plants was studied. • The design criteria for the combined system was provided. [ABSTRACT FROM AUTHOR]

This study aims to develop and assess a new multigeneration system where nuclear heat is utilized as the energy source. The multigeneration system is further designed to generate power, cooling, freshwater and hydrogen. In the present multigeneration system, five main subsystems, including high-temperature gas-cooled pebble bed nuclear reactors, a Rankine cycle, a cobalt-chlorine thermochemical cycle, a multi-effect desalination system and an ammonia-water absorption refrigeration system are integrated for synchronized operation. The analyses of the present system are carried out with the approaches of energy and exergy. This integrated system uses a total of 1000 MW thermal energy that is obtained from four units of high-temperature gas-cooled pebble bed nuclear reactor. Using all the thermal energy that comes from the nuclear reactors, a total of 346.99 MW of electricity, a total of 1.59 MW of cooling, a total of 384.67 kg/s of freshwater, and a total of 0.25 kg/s of hydrogen are produced. The energetic and exergetic performance coefficients of the ammonia-water absorption refrigeration system are 0.74 and 0.83, respectively. While the energy efficiency for the overall system is calculated as 37.83%, the exergy efficiency is found to be higher as 46.32% with the multiple useful outputs which help exergetically improve the overall system. [ABSTRACT FROM AUTHOR]

The world has seen an increase in the popularity of renewable-based energy systems. However, because of their erratic nature, fossil fuels cannot be entirely phased out. Utilizing carbon dioxide in greenhouses close to power plants and generating extra power electricity from dissipated thermal energy are appealing strategies that cause us to have a cleaner environment and affordable power electricity. To exploit the high enthalpy of expelled gases from a gas turbine, the gas turbine was coupled with an absorption refrigerant cycle and an organic Rankine cycle and analyzed. Additionally, a deep artificial neural network method was used to calculate all functions in a rapid optimization and accurate 4E analysis. The carbon dioxide emissions subsided from 0.9183 to 0.41 kg CO2/s, and the optimization time improved 257 times after using the trained machine learning model. An adsorption technique for CO2 separation is used for the proposed system because of its lower energy consumption. The maximum exergy and energy efficiencies were attained at 36.71 % and 49.2 %, respectively, and parametric studies are being assessed. Due to increases in harvests and efficiencies, the net annual interest has increased by 21.8 %, up to 22.5 million dollars. • Capturing CO2 from conventional systems integrated into a greenhouse causes a cleaner environment and more crops. • Preventing release of 0.5083 kg CO2/s into the environmental by absorbing it in a greenhouse. • Using a deep learning model of the system decreases optimization time by up to 257 times. • Using excessive energies in the system for greenhouse and optimization increases efficiencies by almost 10 percent and total interest. [ABSTRACT FROM AUTHOR]

The organic Rankine cycle (ORC) combined heat and power (CHP) system, driven by biomass direct-fired hot water boilers, can effectively address the technical challenges of miniaturizing biomass power generation system. In this study, a biomass-fired ORC-CHP system using biomass as a stationary heat source and R123 as the working fluid is experimentally analysed. The effect of evaporation pressure on ORC thermal efficiency and comprehensive energy utilization efficiency is examined. Results indicate that the maximum exergy loss of 15.129 kW is obtained by the evaporators 1 and 2, which accounts for 63.943 % of the total system exergy loss. The evaporator 3 owns an exergy loss of 6.769 kW, whereas the minimum exergy loss of 0.154 kW is yielded by pump. The maximum electrical power is 782 W with a generation efficiency of 37 % for an evaporation pressure of 10 bar. The ORC thermal efficiency increases along with the evaporation pressure, with values varying between 8 % and 11 %, while the system comprehensive energy utilization efficiency tends to decrease and then increase, ranging between 79 % and 85 %. • A biomass-fired ORC-CHP system is experimentally analysed. • Effect of evaporation pressure on ORC thermal efficiency and comprehensive energy utilization efficiency is examined. • Maximum electrical power is 782 W with a generation efficiency of 37 %. • ORC thermal efficiency is in range of 8–11 %. • System comprehensive energy utilization efficiency is ranging from 79 % to 85 %. [ABSTRACT FROM AUTHOR]

Applying thermal energy storage in a Regenerative Organic Rankine Cycle system is a possible combination of energy storage for renewable and waste energy sources. This research presents an experimental analysis of a regenerative organic Rankine cycle pilot plant, incorporating a thermal energy storage chamber based on a phase change materials to obtain thermal inertia in the system. The primary heat source is the residual heat of combustion gases at a temperature of approximately 320 °C coming from a generating set that operates within a thermal power generation plant. The prototype uses a twin-screw expander modified to work as a turbine. Novec 649 was used as the working fluid which is an organic compound. The experimental evaluation of the regenerative organic Rankine cycle with thermal energy storage has been carried out through energy and exergetic efficiency analysis to verify the operation of the pilot plant. Values of 13.2 % were obtained for the exergetic efficiency and 2.67 % for the global efficiency of the cycle, with a maximum expander work of 11.8 kW. It was demonstrated that the thermal energy storage system provides energy in response to the plant's operating inertia for 17.5 min, sufficient time for the gradual shutdown of the plant equipment, maintaining the working power of the regenerative organic Rankine cycle. • Use of Waste heat recovery in a Thermal Energy Storage for thermal maintenance for operating inertia. • Phase Change Material 54 % KNO 3 and 46 % NaNO 3 applied in a heat storage chamber. • Design and experimental viability to implementation of a TES-RORC prototype. • Energy and exergetic analysis of a TES-RORC plant with experimental exploitation data. • A time of 17.5 min was experimentally obtained for an operating inertia with TES. [ABSTRACT FROM AUTHOR]

For cold energy utilization in the liquefied natural gas (LNG) regasification process, integrated cryogenic CO 2 capture using high-grade cold energy is a mainstream method. However, high-grade cold energy for carbon capture may lead to a decrease in cold energy utilization efficiency. This paper aims to propose a hybrid system in which high-grade cold energy is used for liquid air energy storage (LAES) and post-combustion amine scrubbing technology is considered to replace cryogenic carbon capture for improved working efficiency. The medium and low-grade cold energy is utilized for similar working processes, e.g., organic Rankine cycle (ORC), carbon dioxide liquefaction, and data center cooling for comparison. Results show that the proposed hybrid system can produce 437.7 MW of power, 28.8 t·h−1 of CO 2 capture capacity, and 23.0 MW of cooling capacity, respectively. The levelized cost of electricity and the annual revenue are 112.3 $·MWh−1 and 2.17 million $, respectively. LNG cold energy utilization efficiency, system energy efficiency, and cold exergy efficiency are 53.4 %, 24.0 %, and 51.5 %, higher than similar processes using cryogenic CO 2 capture. It is demonstrated that the proposed system could be a promising method for cold energy utilization and post-combustion capture. • A hybrid system is proposed for LNG cold energy utilization and post-combustion capture. • Cold energy efficiency of the system is much improved when compared with cryogenic capture. • Cold energy utilization efficiency of the hybrid system could achieve 53.4 %. • The LCOE and the annual revenue are 112.3 $·MWh−1 and 2.17 M$, respectively. [ABSTRACT FROM AUTHOR]

In the pursuit of sustainable energy systems, integrating storage technologies is crucial. Compressed air energy storage (CAES) emerges as a significant option for ensuring reliable power supply during peak hours. This study focuses on a configuration combining a CAES unit with two integrated organic Rankine cycle and ejector refrigeration units (ORCERC). The primary objective is to ensure adequate power supply during peak hours in the discharge period, while also providing cooling capacity to enhance system flexibility and efficiency. The proposed system is evaluated from thermodynamic, exergoeconomic, and exergoenvironmental perspectives to determine optimal operating conditions for the CAES unit. A fluid selection process identified a suitable zeotropic mixture, R141b/Hexane, as the working fluid for both ORCERCs. The results demonstrate a net power production of 20,749.91 kW and a cooling load of 1448.23 kW, with cost and exergoenvironmental impact rates of $1193.59/h and 143.42 Pt/h, respectively. Additionally, the configuration achieves an exergy round-trip efficiency of 65.85 % and a payback period of 2.88 years. Increasing the HTES temperature from 1150 to 1250 K improved both the round-trip efficiency (RTE) and exergetic round-trip efficiency (ERTE) from 52.22 % to 53.39 % and 62.98 %–63.71 %, respectively, while reducing the product cost and exergoenvironmental impact rate from $1128 to $1117/h and 134.35 to 127.93 Pt/h, respectively. Three triple-objective optimization scenarios were considered, yielding diverse outcomes, each contributing unique insights into the system's performance and potential improvements. • Efficient CAES with two ORCERC subsystems for 20 MW peak shaving. • Thermodynamic, economic, and exergoenvironmental analyses conducted. • ORCERC subsystems' working fluids selected from six zeotropic mixtures. • RTE, ERTE, and payback period achieved: 58.63 %, 65.85 %, and 2.88 years. • Produced power and cooling result in 143.42 Pt/h environmental impact. [ABSTRACT FROM AUTHOR]

The present study aims to develop a novel configuration of hydrogen and electricity co-production based on a small modular nuclear reactor (SMR) by synergistically integrating the Vanadium Chloride thermochemical (V–Cl) and helium-closed Brayton cycles. For the V–Cl thermochemical cycle, a steady-state simulation model is developed for the first time in the Aspen Plus environment. The entire system is assessed thermodynamically by calculating the exergy destruction rate and exergy efficiency of major components employed in different subsections (nuclear power production, clean hydrogen production, supporting Rankine cycle, hydrogen compression, and storage) of the plant. Various parametric studies are conducted to identify the scope of improvement and evaluate suitable operating parameters that exhibit optimized system performance. It is found that a maximum H 2 production rate is achieved when the VCl 4 flow is 3.6 kmol/h. A specific hydrogen production rate of 9.63 g/kWh is achieved. The reduction reactor and Deacon reactors are responsible for the highest and lowest exergy destruction with a value of 155.46 kW and 37.60 kW accounting for 49 % and 11.86 % of the overall exergy destruction within the V–Cl cycle. The share of power production from the secondary Rankine cycle in the overall hydrogen compression train is 16.48 %. The parametric study results show that with an outlet helium pressure of 15 bar, the overall work output and electrical efficiency peaked with a value of 4.6 MW and 15.64 % respectively. The overall energy and exergy efficiencies of the proposed system are found to be 16.94 % and 21.42 % respectively. • Process simulation of a four-step V–Cl thermochemical cycle is performed. • A small modular nuclear reactor is integrated. • Aspen Plus process simulator is used. • Energy and exergy efficiencies are determined. • Several sensitivity analyses are conducted under different scenarios. [ABSTRACT FROM AUTHOR]

The study focuses on achieving energy self-sufficiency in Wastewater Treatment Plants by proposing a comprehensive model for integrating, sizing, and optimizing an Organic Rankine Cycle system. The Organic Rankine Cycle system is designed to utilize waste heat from the gensets at As Samra Wastewater Treatment Plant in Jordan, where it will contribute to the overall electrical energy supply of the plant. Real data from As Samra Wastewater Treatment Plant is used to model and calculate the available waste heat using TRNSYS® software. The Organic Rankine Cycle model is then developed using ASPEN PLUS® software to explore the impact of operational parameters and determine their optimal values for maximizing the plant's energy profile. An economic analysis is conducted to assess the feasibility of the proposed model, considering system components, installation, operation, and maintenance costs. To optimize the Organic Rankine Cycle system, the study employs the Multi-Output Support Vector Regression technique to capture nonlinear relationships between independent variables (fluid type, turbine inlet pressure, turbine inlet temperature, turbine outlet pressure, and mass flow rate) and dependent variables (pump power input, waste heat input, and turbine specific work). The Osprey optimization algorithm is used to address the multi-objective optimization problem, with the proposed Pareto-based Osprey Optimization Algorithm and the Multi-Objective Particle Swarm Optimization technique being employed to evaluate critical performance and economic parameters such as system thermal efficiency, net power output, and the levelized cost of electricity. The results of the optimization strategies indicate that the M-SVR model's prediction accuracy is significantly improved after parameter optimization, with the model returning high R2 and low Mean Square Error values of 0.991 and 0.00216, respectively. The Pareto-Based Osprey Optimization Algorithm optimizer identifies the best working fluid as Isobutane/Isopentane in a ratio of 66:34, with optimal turbine inlet pressure and temperature of 15 bars and 218 °C, respectively. The Organic Rankine Cycle model at these optimal conditions achieves a cycle efficiency of 19.93 % and an Levelized Cost of Electricity value of 0.0353 USD/kWh. • Integration of ORC system enhances energy self-sufficiency in WWTPs. • Advanced modeling and optimization methods boost prediction accuracy and efficiency. • Multi-Objective Optimization was performed using M-SVR and the Osprey algorithm. • Optimal ORC configuration achieves cycle efficiency of 19.9 % and LCOE of 0.035 $/kWh. • Economic analysis confirms feasibility, considering investment and operational costs. [ABSTRACT FROM AUTHOR]

With ever increasing fossil fuel price and growing demands in cutting emissions, waste heat recovery (WHR) appears as a promising pathway to improve propulsion system performance, which can be potentially achieved by incorporating a recuperator. This paper explores the advantages and potentiality of further recovering exhaust heat from recuperated turboshaft engine through the concept of organic Rankine cycle (ORC) to improve fuel economy and thermal efficiency. For the intended application, working fluid selection is conducted after systematic consideration of thermophysical properties, environmental impact, health and safety issues. Furthermore, parametric analysis is carried out from the viewpoint of thermodynamics, and the genetic algorithm is also employed to obtain the maximum net power output. Targeting the implicit coupling between recuperator effectiveness and ORC performance, the potential advantages of the combined engine-ORC system are comprehensively evaluated at different operational regimes. The influence of flight condition is also discussed through sensitivity simulations for different altitudes. Results reveal that the combination of the recuperated engine with ORC cycle operated using acetone generally offers the greatest benefits, significantly reducing specific fuel consumption by 46%–59 % relative to the baseline simple-cycle engine, depending on the availability of heat source. This analytical work contributes to provide valuable insights into WHR technologies in the aviation industry. • ORC is proposed to recover exhaust heat from turboshaft engine with a recuperator. • Working fluid selection procedure suitable for aeroengine is conceived and applied. • Parametric investigation is conducted and GA is employed for optimization. • System performance is comprehensively evaluated at different operational regimes. [ABSTRACT FROM AUTHOR]

Integrating flat solar thermal collectors and organic Rankine cycle (ORC)-based power units in micro-cogeneration systems ensures a reduction in CO 2 emissions in domestic applications. The key component of these systems is the expander, which must withstand frequent off-design operating conditions owing to the intermittent nature of the solar source. Despite being in the first stage of technological development, scroll expanders are widely adopted in small-scale applications owing to their operating flexibility and robustness. In this study, a domestic micro-cogeneration unit equipped with a scroll expander is characterised experimentally. The experimental data are used to calibrate the expander and ORC unit models. The models are used to evaluate the operating limits of the units as functions of the main operating parameters. The maximum power and efficiency are obtained as 300 W and 3 %, respectively, for hot water temperatures between 90 °C and 100 °C, close to the rated performances. Finally, the effect of adopting a dual-intake port on the expander and unit performance is assessed. The technology facilitates the widening of the operating range (20–140 g/s mass flow rate of WF) and a peak power production of 1.2 kW. • Development of novel operating maps of solar ORC unit for micro-cogeneration. • Assessment of the impact of scroll expander improvement on ORC unit operability. • Development of a novel regulating strategy based on Dual Intake Port (DIP) technology. • DIP regulation ensures a wider operability than expander variable speed regulating approach. • DIP regulating strategies avoid unworking region with a power peak of 1.2 kW. [ABSTRACT FROM AUTHOR]

The organic Rankine cycle coupled vapor compression refrigeration system is an attractive refrigeration technology that converts low-grade thermal energy into cooling capacity to improve waste heat utilization efficiency. Due to the inevitable change in ambient temperature and cooling demand, the dynamic characteristics of the combined system are worth studying. In this paper, a small experimental apparatus with a common condenser is designed and developed. The dynamic characteristic experiments under different disturbances are carried out to understand the response characteristics of operating parameters and the variation of system performance. The results show that the maximum response time of the system under different disturbances ranges from 493 s to 694 s. The impact of throttle opening on the response characteristics of refrigeration subsystem parameters is significantly higher than that of the organic Rankine cycle. The mass flow rate of organic Rankine cycle has the fastest response to pump frequency, while the compressor inlet temperature changes rapidly with the cooling water temperature. Under a step cooling water temperature, it is important to control the compressor inlet temperature to avoid liquid droplets in its inlet. In addition, the mass flow rate of organic Rankine cycle should be controlled reasonably to achieve the maximum coefficient of system performance. The cooling capacity of the system is mainly affected by the cooling water temperature and the throttle valve opening. During the experiment, the maximum cooling capacity and performance coefficient of the system are 3.75 kW and 0.275, respectively. This work can provide guidance for the design of the control strategy of the combined system. • An organic Rankine cycle coupled vapor compression refrigeration system was built. • Dynamic characteristics of the combined system under various disturbances were tested. • Response time and change rate of main parameters were provided. • System has a large thermal inertia with a maximum response time of 694 s. [ABSTRACT FROM AUTHOR]

In the contemporary context, significant importance is attributed to micro and small-scale Organic Rankine Cycle (ORC) units that are specifically designed for decentralized electricity generation. An essential component within each ORC system is the expander, available in both volumetric and turboexpander configurations. In the existing biogas plant with an Internal Combustion Engine (ICE), the ORC, functioning as a bottoming cycle (BORC) on ICE waste heat, is installed. The BORC utilizes the heat from exhaust gases and the cooling water of the ICE. The paper investigates the effects of various working fluids on both the thermodynamic efficiency of the BORC and the isentropic efficiency of the turboexpander, thus influencing the design parameters of the turboexpander (e.g., number of stages, stator and rotor blade heights, etc.). The BORC, employing the working fluid R141b, has exhibited superior thermodynamic performance, demonstrating a commendable 63.5 kW in net power with a thermodynamic efficiency of 13 %, and ultimately increased the power of the ICE (537 kW) by approx. 12 %. Regarding the turbine component, the turbine operating with the R141b working fluid demonstrated the highest power output and isentropic efficiency, achieving values of 64.14 kW and 67.4 %, respectively. A design was developed for the same turbine, with aerodynamically perfect profiles specially designed for the stator and rotor blades. • In recent decades there has been a significant increase in interest in the use of waste heat (WH). • For the use of WH from internal combustion engine (ICE) the organic Rankine cycle (ORC) comes to the fore. • An important component of every ORC is the expander. • The working fluid influences both on efficiency of ORC and turbine design. • ORC increased the power of the ICE (537 kW) by approx. 12 % (63.54 kW). [ABSTRACT FROM AUTHOR]

This study implements a comprehensive dynamic simulation using a moving-boundary method to characterize an organic Rankine cycle under assumption-free operating conditions. The novelty of the model lies in its unique methodology for determining the state vector variables and initial conditions of the system, particularly in integrating sub-models, notably the model of liquid receiver. Consequently, the implemented dynamic model accurately forecasts the system's performance, focusing solely on the boundary conditions. A comprehensive dynamic model is constructed, encompassing a wide range of scenarios and facilitating the interchangeability of models as required. One notable advantage of the model is its systematic approach, which begins each simulation by determining the system's initial conditions before conducting the dynamic model in parametric and dynamic studies. The capability and accuracy of model is confirmed through comparison with experimental data under various steady-state and dynamic conditions, while adhering to the main rules of mass and energy conservation. The prediction accuracy of the model is evaluated by mean absolute percent error. According to the results, the maximum deviations of simulation results mostly are less than 11 %. • Using moving-boundary method to simulate an ORC under assumption-free conditions. • Using unique method for determining state vector variables and initial conditions. • Dynamic model precisely forecasts system performance, focusing on boundary conditions. • The maximum deviations between the simulation and experimental results are 11 %. • The simulation shows ORC's dynamic behavior when input conditions vary. [ABSTRACT FROM AUTHOR]

A novel integration of molten carbonate fuel cell (MCFC) stacks in a biomass-based Rankine cycle power plant with CO 2 separation has been proposed, and techno-economic and environmental analyses have been performed for the plant configuration. Both a biomass gasifier and a biomass combustion fluidized boiler (CFB) have been considered for the proposed plant, which has a unique configuration of MCFC stacks placed in the back-pass of the CFB to achieve an efficient plant configuration. Parametric variations of the key performance parameters with varying input variables have been observed, and a best-case operating condition has been identified from the parametric study. It is observed that the proposed plant can produce 12.645 MW of power with 60.22 % electrical efficiency at a unit electricity cost of 0.09497 $/kWh at best-case operating condition. Moreover, 137701 tons/year of CO 2 cutting is observed at the best-case condition, which results in 20.66 million $/year of total environmental benefit. Cost sensitivity suggests that the plant can yield a unit electricity cost of 0.03314 $/kWh at the best economic conditions, and the payback analysis outlines that the plant can recover its initial investment in 3.467 years when there is a 50 % capital subsidy. • A novel integration of MCFC stacks in a Rankine cycle plant with CO 2 separation. • Thermo-economic and environmental analyses have been performed. • 60.22 % efficiency with unit electricity cost of 0.09497 $/kWh is observed. • 137701tons/year CO 2 cutting & 20.66 million$/year environmental benefit achieved. Novel Integration of Molten carbonate fuel cell Stacks in a Biomass-based Rankine Cycle Power Plant with CO 2 Separation: A Techno-economic and Environmental study. [ABSTRACT FROM AUTHOR]

The expansion device is considered the crucial equipment in Organic Rankine cycle (ORC). Due to the structure limitation, the scroll expander would be critical affected by the external load characteristics. In this work, to fit the development trend of small-scale ORC and fill the research blank of load resistance, the ORC system with rated power of 300 W e was experimentally studied, the dynamic operation characteristics, the direct and indirect influence on each device, and the overall system performance with rated load of 175 W e , 200 W e and 225 W e were evaluated. By adjusting the frequency of the pump, the system dynamic operation characteristics are developed, and the behaviors of the devices are analyzed. According to the system analyses, despite the system with a rated load of 225 W e could reach the highest output of 707 W net , the system with the lower rated load has the favorable performance, caused by the superior expander and generator behaviors with lower Ampere force. The overall system performance shows that the thermal efficiencies exhibits an increase trend of about 6.67 %, 7.01 %, and 7.27 % sequentially for the system with rated load of 225 W e , 200 W e , and 175 W e. • The ORC system with rated power of 300 W e was experimentally studied. • Effect of resistive load with 175 W e , 200 W e and 225 W e on system behaviors were evaluated. • The coordination of the rated load, system capacity and operating parameters is highlighted. • Thermal efficiencies are about 7.27 %, 7.01 %, 6.67 % for system with 175 W e , 200 W e , and 225 W e. [ABSTRACT FROM AUTHOR]

The thermal stability of working fluids is a crucial property studied in the selection of organic Rankine cycle fluids, as they may undergo decomposition at elevated temperatures. In previous studies, siloxanes have been identified as promising choices for ORCs. However, research on the thermal stability of siloxanes in ORCs has been relatively limited. This study investigates the thermal stability and pyrolysis mechanism of MD 2 M through a combination of experiment, DFT simulation, and ReaxFF-MD calculation. The experiment revealed that MD 2 M exhibits poor thermal stability, with a decomposition rate of approximately 1.82 % at 200 °C in 72h. Consequently, it is unsuitable for operating in ORCs at temperatures of 200 °C and above. The primary gas products in the pyrolysis of MD 2 M include CH 4 , C 2 H 6 , C 2 H 4 , CO, and CO 2 , among others. ReaxFF-MD and DFT elucidated the thermal decomposition mechanism of MD 2 M. The Gibbs free energy barriers for Si–C bond cleavage reactions are relatively lowest, measured at 352.98 and 341.33 kJ mol−1, respectively. Simultaneously, methylation of the terminal Si atom is likely to represent the primary reaction pathway for the initial decomposition. • Under thermal stress conditions at 200 °C, MD 2 M undergoes significant decomposition. • The main gas products include CH 4 , C 2 H 6 , C 2 H 4 , CO, and CO 2 , among others. • MD 2 M may exhibit polymerization reactions solely within the liquid phase at lower temperatures. [ABSTRACT FROM AUTHOR]

This study investigates methods to reduce heat losses, CO 2 emissions, and improve the overall efficiency of micro gas turbine power plants, considering economic viability as gas turbines are a major component of the global energy supply chain. Heat recovery and carbon capture techniques were employed to achieve these goals. First, a steam Rankine cycle and a greenhouse were designed to integrate with an existing micro gas turbine. Second, the entire system was simulated using thermodynamic, economic, and environmental models. Finally, an optimization process was conducted through a machine learning model using the integrated model. By adding a Rankine cycle, 80 % of the heat losses in a traditional power plant were recovered, converted into electricity and cooling, and resulted in a 3 % efficiency improvement. Additionally, implementing a CO 2 separation and capture unit with utilization in a nearby greenhouse not only enhanced greenhouse profitability but also significantly reduced CO 2 emissions into the atmosphere. While the system's cost rate increased by $40/hour, the investment payback period is only 0.97 years. Furthermore, CO 2 emission rate was reduced by 15 %. [Display omitted] • Propose and analyze an integrated system for CO 2 capturing from a gas turbine. • Employing a techno-economo-environmental analysis for the integrated system. • Optimizing the proposed system and compare it with the existing power plant. • Determining the possibility of implementing such a system as a case study. [ABSTRACT FROM AUTHOR]

In the present research a cogeneration cycle based on a solid oxide fuel cell (SOFC), and Organic Rankine Cycle (ORC) is proposed. The cycle is fed with biogas in different molar ratios of carbon dioxide to methane (RCTC). In addition, the cycle is examined for both dry reforming (DR) and steam reforming (SR). A thermochemical model is presented for both cycles of SR–SOFC–ORC, and DR–SOFC–ORC. The model is coded in MATLAB coupled with Engineering Equation Solver software. The model was verified with both experimental and theoretical research and agreement was achieved. The energy and exergy performance of the cycle is presented and carbon deposition on the cathode due to different reactions of methane cracking, Boudouard reaction, and vapor formation are studied. The results show that for RCTC<1.2 steam reforming produces more hydrogen, while for RCTC>1.2 dry reforming is advantageous. At RCTC = 1.2 the DR and SR work the same. The overall thermal efficiency of DR-SOFC and SR-SOFC has reached 67 % and 70 %. Carbon deposition due to the Boudouard reaction, and vapor formation for both SR and DR are negligible while due to methane cracking is serious. The DR-SOFC deposits less carbon because of methane cracking due to higher operating temperatures. • A cogeneration cycle based on a biogas fueled SOFC and ORC is proposed. • The cycle is assessed with both dry and steam reforming. • The impact of different biogas compositions on cycle performance is evaluated. • Carbon deposition on the cathode is investigated. • The cycle based on steam reforming has higher efficiency. [ABSTRACT FROM AUTHOR]

With the development of polymer flooding technology, polymer-containing oily sludge (PCOS) has become a major pollutant on offshore oil platforms. Supercritical water gasification system is an efficient and pollution-free technology compared to conventional PCOS treatment. However, the system model for PCOS has not yet been established and the theoretical model for system optimization is insufficient. In this work, a novel auto-thermal system is established based on supercritical water gasification technology for the treatment of PCOS. Through the thermodynamic analysis, an optimization plan is concluded and used for the establishment of a modified system with Organic Rankine Cycle. Results show that the two-stage reactor reduces the gasification reaction temperature from 652 °C to 502 °C, and the Organic Rankine Cycle system using Isopropanol recover 9.1 % chemical exergy of feedstock with the optimal parameters (superheat, evaporation temperature and circulating pressure). The energy and exergy efficiency of the modified system has increased by 52.4 % and 42.4 % compared to the original system. Besides, a life cycle assessment is adopted for the environment analysis. The results show that the increasing gasification temperature and PCOS slurry concentration can reduce system unit exergy loss. Global Warming Potential reaching the minimum value of 26.1 at 65 wt%. • Two-stage gasification system of polymer-containing oily sludge was proposed. • Waste heat utilization system was simulated based on Organic Rankine Cycle. • Optimal parameters on exergy efficiency was obtained. • Life cycle assessment of sludge gasification was conducted. • Modified system reduced the gasification temperature of sludge. [ABSTRACT FROM AUTHOR]

Gas-fired power generation, characterized by high efficiency, low carbon emissions, and flexibility, contributes significantly to the global energy transition. In the present work, a novel dual-stage intercooled and recuperative gas turbine system integrated with transcritical organic Rankine cycle (dICR-GT-tORC) was proposed. System modeling was carried out based on Thermoflex software for different configurations to evaluate the energetic and exergetic performances. It was found that the dICR-GT-tORC exhibited improved thermodynamic performance compared to the gas turbine simple cycle and dICR-GT system, with the system net energy efficiency/exergy efficiency/specific work increasing from 43.88%/41.80%/567 kJ·kg air −1 and 57.21%/54.49%/684 kJ·kg air −1 to 62.48%/59.52%/745 kJ·kg air −1, respectively. An energy utilization diagram analysis revealed that the energy cascade utilization was achieved by coupling a bottoming tORC to fully utilize the waste heat from intercoolers and the exhaust gas. Furthermore, the dICR-GT-tORC demonstrated enhanced environmental performance, reducing the CO 2 emission rate by a maximum value of 29.8%. Additionally, the impacts of key parameters, including the organic working fluid selection, the minimum temperature difference at the pinch point of recuperators and the terminal exhaust gas temperature on the system performance were investigated. It was indicated that the proposed system could be applicable in various practical scenarios from thermodynamic and environmental perspectives. • Dual-stage intercooled and recuperative gas turbine system integrated with transcritical ORC was proposed. • System modeling was conducted for energetic and exergetic performances evaluation. • The energy efficiency of the proposed gas-fired power system reached up to 62.48%. • Influence of key parameters on the system performance was analyzed quantitatively. [ABSTRACT FROM AUTHOR]

As a clean energy source with high calorific value and low pollution, liquefied natural gas (LNG) has gained much attention and increased fast in the current energy market. It also has considerable cold energy resources that can be used to generate electricity during the regasification process. To fully utilise the cold energy of LNG, a double-Rankine cycle power generation system that incorporates heat exchange between LNG cold energy utilisation and a propane-ethylene cycle working medium is proposed and optimised. The optimisation is based on the Process Integration method, which uses Pinch Analysis to develop a Heat Exchange Network. Upon a specified LNG flow rate of 15.6 kg/s and natural gas delivery pressure of 7.85 MPaG, a retrofit case of the optimised LNG cold energy system generates a power of 1917.21 kW. A 28.6 % increase in power generation efficiency compared with the existing case. The result showed that by employing the Process Integration method, this study maximises the use of LNG cold energy through heat exchange with various working media, effectively addressing power generation efficiency issues. This approach is important in reducing power generation costs, minimising environmental impact, and advancing resource sustainability. Furthermore, it serves as a valuable reference for enhancing power generation efficiency by utilising LNG cold energy. [ABSTRACT FROM AUTHOR]

Organic Rankine cycle (ORC), biomass combustion and single-effect lithium bromide absorption refrigeration are appealing and promising technologies for combined heat, cool and power (CCHP) system. A novel biomass-fired CCHP system incorporating ORC and single-effect lithium bromide absorption refrigeration integrated with monoethanolamine (MEA)-based CO 2 capture is proposed in this paper, in which the pressurized hot water is used as heat source for ORC system and refrigeration cycle. Specifically, the condensation heat of ORC can be properly harvested for domestic hot water supplying. The refrigeration coefficient of r C is defined to characterize energy distribution relationship between ORC and refrigeration cycle. Results show the optimal evaporating temperature and heat source temperature are determined with refrigeration efficiency and net present value through gray correlation method when achieving excellent thermo-economic performance simultaneously. Besides, the optimal condensation temperature is directly affected by domestic hot water temperature. It further suggests that biomass-fired CCHP system incorporating ORC with cyclopentane owns the best thermo-economic performance with the maximum power efficiency of 7.4 %, refrigeration efficiency of 14 %, thermal efficiency of 81.5 % and primary energy saving ratio of 13.3 %. The optimized bioenergy system is thermodynamically and economically attractive, environment-friendly with negative CO 2 emissions substantially attributed to CO 2 capture. • A novel biomass-fired ORC-CCHP system integrated with SeBrLi absorption refrigeration and CO 2 capture is developed. • Optimal evaporation temperature and heat source temperature are determined with η C and NPV through gray correlation method. • Condensation temperature of the bioenergy system is optimized with a thermo-economic evaluation. • Thermo-economic comparison of different candidate working mediums concerning CO 2 capture is conducted. • Bioenergy system is thermodynamically and economically attractive with negative carbon dioxide emissions. [ABSTRACT FROM AUTHOR]

In the background of global efforts to reduce carbon emissions, mixed working fluids could mitigate flammability concerns of low global warming potential (GWP) working fluids for organic Rankine cycles (ORCs) and compression refrigeration cycles. In this study, the combustion and interaction mechanisms of R152a/R1216 and R1270/R1216 were investigated. Density functional theory (DFT) and ReaxFF molecular dynamics (MD) methods were employed to analyze the combustion processes of the two binary working fluids and the formation pathways of the toxic substance HF. Additionally, the influence of R1216 on the combustion of R152a and R1270 was evaluated and compared at different reaction temperatures and component ratios. The results showed that, R1216 did not inhibit but rather promoted the consumption of R152a and R1270. Corresponding experiments demonstrate that the combustion of R152a and R1270 becomes more complete and occurs more quickly after the addition of low proportions of R1216. Subsequently, the flammability limits of the two binary working fluids were determined through experiments at different ambient temperatures. The experimental results indicated that the rise in ambient temperature expands the flammability limit ranges of both binary working fluids, and the higher the proportion of R1216, the more sensitive the flammability is to changes in ambient temperature. • The combustion mechanisms of R152a/R1216 and R1270/R1216 were analyzed and compared. • The flammability of the two working fluids was tested at different temperatures. • The n(H/F) ratio in binary systems affects the generation of HF. • R1216 promotes the consumption of R152a and R1270 during combustion. • A higher proportion of R1216 is more sensitive to ambient temperature change. [ABSTRACT FROM AUTHOR]

The present work focuses on vessel engine waste heat recovery (WHR) architectures for cooling, heating and power production based on the combination of an Organic Rankine Cycle (ORC) and a thermally assisted ejector cooling cycle-vapor compression cycle (EVCC), integrated into an ORC-EVCC. Their advantages and disadvantages are analyzed and their performance is evaluated using numerical models developed according to boundary conditions corresponding to a vessel diesel engine WHR micro-scale (100 kW th thermal input) application considering R1233zd(E), R1234yf and R1234ze as working fluids. Ultimately, a parallel ORC- parallel/serial EVCC layout operating with R1233zd(E) is determined as the most promising configuration, considering its superior thermodynamic performance and practical aspects (simplicity, space and weight requirements and cost). The ORC and EVCC are integrated in parallel and operate with the same fluid. Furthermore, the EVCC compressor and ejector are connected in a parallel/serial layout. Under the design point, the net power output of the system is 10.30 kW e in electricity-only mode and 7.68 kW e in CHP mode. In CHP mode, the heating output is 88.97 kW th. In the two cooling modes, electricity and cooling are produced simultaneously by the ORC and EVCC, respectively. The cooling output ranges between approximately 4.48 and 7.82 kW c. [ABSTRACT FROM AUTHOR]