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• Inaugural integration of SBS-CPVT-TSORC to explore capabilities of proposed system. • The integrated system maximizes the utilization of solar energy for CHP generation. • Parametric analyses are carried out to gain insights into the system's performance. • Optimizations are conducted with varying working fluids, addressing optimal design. • Confirming the strong competitiveness of the proposed system with other CHP systems. As fossil energy reserves diminish and environmental concerns grow, there is increasing interest in solar-based combined heating and power systems. The organic Rankine cycle is a promising technology for efficiently converting heat from concentrated photovoltaic thermal systems into power. This study hypothesizes integrating a spectral beam splitting concentrated photovoltaic thermal system with the recent organic Rankine cycle advancements, the two-stage organic Rankine cycle, noted for its straightforward architecture and enhanced power outputs to optimize solar energy utilization for both electricity generation and thermal power. The aim is to explore the influence of key design factors on each subsystem's performance using EES and MATLAB, assessing the integrated system under various atmospheric conditions. The model's accuracy was confirmed by comparing the results of the two sub-systems to previously published data. The findings indicate that the total electrical efficiency increases from 8.98 % to 16.94 % as solar irradiance rises from 600 W/m2 to 1000 W/m2, leading to an overall efficiency improvement of 57.94 %. The integrated system can produce 2.14 kWh/day/m2 of electrical power and 6.17 kWh/day/m2 of thermal power, achieving a heat-to-power ratio of approximately 2.83, comparable to conventional systems. The research will yield actionable insights that can be utilized to enhance the design and performance of the system. [ABSTRACT FROM AUTHOR]

• Converting biomass to biofuels exergetically outperforms electricity generation. • An exergoeconomic trade-off was found between exergy content products and costs. • Thermochemical routes enhanced exergy efficiency and lowered exergy costs. • Biochemical routes showed lower monetary costs and potential economic viability. • The use and better distribution of biomass leads to better biorefinery design. This work, conducted exergy and thermoeconomic analyses of sugarcane biorefineries for different biomass allocations and conversion technologies. Using the Kriging method to determine biomass allocation, this article evaluated the performance of a sugarcane biorefinery based on the 2nd Law of Thermodynamics. By this combination of techniques, it is possible to provide better guidance to decision-making. Therefore, through exergy analysis, it is possible to improve the allocation of biomass and energy resources to be more appropriate. Therefore, biorefineries can be more efficient and synthesize products at lower costs. Moreover, the highest exergy efficiency, 43.7 %, occurred when all sugarcane bagasse was destined for the thermochemical route, 60 % for Fischer-Tropsch synthesis, and 40 % for a BIG-GTCC. On the other hand, the lowest exergy efficiency, 39.63 %, was observed in the conventional case, indicating that prioritizing biomass conversion to any kind of fuel is more productive than allocating it to produce electricity in a Rankine Cycle, regardless of technology and biofuel. Moreover, from the exergoeconomic insight, a promising trade-off was determined: the thermochemical routes proved to be better in efficiency, both energetically and exergetically, while the biochemical routes, indicated potential profitability. Furthermore, the exergoeconomic analysis demonstrated that increasing the exploration of second-generation biomass in the biorefinery lowers the exergy costs of every product. Overall, this research highlights the potential associated with sugarcane biorefineries going into expansion and modernization since its resources can be valorized in terms of efficiency and monetary value. [ABSTRACT FROM AUTHOR]

[Display omitted] • Integrating heat-only small reactors, district heating, and organic Rankine cycle. • Design capacities, and energy management employing energy storages are optimized. • The integration effectively enhanced the economics of heat-only small reactors. • This system is a promising solution for decarbonizing the district heating sector. • Interest rate, and electricity price are key factors in the system's economic. The heat-only small modular reactor (SMR) concept is one of the potential carbon-free solutions for replacing fossil fuel-based district heating systems (DHSs). This idea faces an economic challenge (high levelized cost of heat) due to high capital cost and low capacity factor (because of demand fluctuations) in stand-alone operation mode. This study proposes integrating DHSs with heat-only SMRs and organic Rankine cycle (ORC) electricity generation to maximize the system's economic profit. Heat storage, gas boiler, and electricity storage are candidate units for optimizing the system's energy management. The developed optimization method is a mixed-integer nonlinear problem (MINLP). The objective variables are the equipment's design capacities and hour-by-hour operation, and the net present value (NPV) is the objective function. Considering a typical DHS in Czechia (peak of 41 MW t), the optimized integration found comprises a heat-only SMR (Teplator-150 MW t), an ORC power plant of (20 MW e), heat storage of (10000 MW t h), a gas boiler of (3.4 MW t), and (20 MW e /120 MW e h) electricity storage. This system and its energy management optimization enhanced the SMR's capacity factor (from 10 % to 83 %), and the NPV changed from a loss of 50 M€ to a gain of 357 M€ compared to the basic heat-only supply system. The sensitivity analyses showed that the size and technology of ORC, the interest rate, and the electricity price are the most important factors in the system's economic viability. [ABSTRACT FROM AUTHOR]

• Flexible generation is increasing in value compared to baseload generation. • Thermal storage enables nuclear plants to respond nimbly to load variability. • Flexible nuclear power plants will operate in a more competitive energy market. • Average economics of nuclear can be improved by up to 41%. • Multidisciplinary analysis of thermodynamics, sizing, economic and off-design. Advanced nuclear power plants are well-positioned for future zero-carbon grids, however, the need for flexible power generation will be required over the traditional emphasis on baseload generation for meeting historical demands. To achieve such flexibility, this work examines viable configurations for coupling nuclear energy production with thermal energy storage. Previous designs on nuclear-thermal energy storage configurations for advanced reactor designs, which utilized reactor steam as the heat source for charging the thermal energy storage, are restricted by the heat diversion ratio and efficiency losses, thus their impacts can be limited. In this context, this study proposes configurations for fully decoupling the nuclear reactor from the power cycle and positioning the storage as an intermediate loop, thereby achieving an unconstrained heat diversion ratio and improved efficiency. Compared with a standard high-temperature gas-cooled reactor's power cycle, steady-state thermodynamic modeling and dispatch optimizations quantify the benefits of a steam reheat cycle within the fully decoupled thermal energy system to separate the plant cycle from the high-pressure primary side. These benefits are further detailed, compatible with required high-temperature and high-pressure conditions, through (1) open-source dynamic transient models that examine the impact of off-design operation on the systems, (2) the investigation of components design and costing and finally (3) sizing and dispatch optimization. The fully-decoupled design achieves a cycle efficiency of 43.1%, an enhancement over the vendor's standard efficiency of 42.2% (Xe-100 design). The proposed design offers strengthened physical barriers from the nuclear island as well as superior operational flexibility and power boosting. Dispatch optimization and market analysis reveal that thermal energy storage size is highly dependent on the peak patterns of electricity prices and the minimum generation level constraint imposed on the balance of plant. Evaluation of off-design operation demonstrates that the full decoupling design with the suggested fail-safe control mechanisms ensures a minimal impact on reactor parameters, even during rapid power ramping. [ABSTRACT FROM AUTHOR]

[Display omitted] • Integration potential between regasification terminals and methylcyclohexane dehydrogenation plants. • Proposed integrated terminal design for cold energy recovery and utility reduction. • 45.4 % reduction in reaction pre-heating and 104 % reduction in external power, based on a case study. • Hydrogen production capacity of 11.1–12.0 tonnes per 100 tonnes of liquified natural gas. • Up to 7.1 tonnes per hour of hydrogen produced without external power input. Methylcyclohexane (MCH) is a promising organic hydride carrier for hydrogen transport and storage. Recovering hydrogen from MCH is an energy intensive process. An innovative idea of integrating this process with liquified natural gas (LNG) regasification is proposed in this study and demonstrated via modelling and simulation to substantially reduce external energy use. The synergistic benefits are twofold. In addition to providing a cold energy source for an effective high recovery cryogenic flash separation, the organic Rankine cycle based electrical power generation potential from LNG cold energy is fully exploited to reduce/eliminate external electricity demand for hydrogen compression to the high (end use) pressure. The results is a major reduction in carbon dioxide emissions. The proposed design for an integrated LNG-H 2 terminal can supply (1) 99.99 mol% pure hydrogen to a Combined Cycle Gas Turbine (CCGT) power plant and (2) commercial-grade natural gas to a gas-grid, both at the desired pressures and temperatures. Subsequently, rigorous simulation-based optimization was performed to minimize external energy inputs. A case study with 100 tph MCH and 100 tph LNG showed that integrating regasification with dehydrogenation produced 6.2 tph of hydrogen while gasifying LNG with a net power generation of 310 kW and a hydrogen recovery cost of 0.282 $/kg H 2. Up to 7.3 tonnes of hydrogen can be produced per 100 tonnes of LNG without the use of external power. On the other hand, using external power, up to 11.3 tonnes of hydrogen can be produced per 100 tonnes of LNG without any external refrigeration. Overall, the superstructure proposed in this manuscript provides a generic initial approach for future MCH hydrogen supply chain projects, when considering integrations with LNG regasification plants. [ABSTRACT FROM AUTHOR]

• Design of a solar-assisted Ocean Thermal Energy Conversion plant for power and cooling generation. • Thermodynamic performance evaluation and validation of an Organic Rankine cycle and Vapor Compression cycle. • Sensitivity analysis on energy, exergy, and economic performance of various parameters. • Multi-objective optimization of the solar-assisted Ocean Thermal Energy Conversion system. Multi-generation systems based on renewable emerge as promising avenues to promote sustainability for the energy sector. This study introduces a novel concept: an Ocean Thermal Energy Conversion plant assisted by solar energy for both power and cold generation. Power generation is accomplished via an Organic Rankine cycle, while refrigeration needs are met through a vapor compression cycle. Employing Aspen Hysys for simulation, a comprehensive thermodynamic performance evaluation was conducted with extensive sensitivity analyses. Specifically, the effect of various parameters on energy, exergy and economic performance, including working fluids (R114, R134a, R600, and R600a), boiler outlet temperatures, and pressure ratios was investigated. Notably, pressure ratio was found to be the most critical design parameter significantly influencing both net work generated and exergy efficiency. R600 demonstrated the highest energy and exergy performances, with net work generation reaching 20.732 kW and exergy efficiency peaking at 77.07 % for R600a. Furthermore, R600 exhibited the highest COP of 5.24 in refrigeration. In terms of total costs, solar collectors accounted for a substantial portion, constituting 79.7 % of the total costs when using R134a as a working fluid. To optimize the system's performance, a multi-objective optimization was conducted, providing valuable insights into the integration of solar-assisted OTEC plants. This study not only showcases the potential of combining solar energy with OTEC technology but also underscores the critical design and economic considerations necessary for advancing these sustainable energy solutions. [ABSTRACT FROM AUTHOR]

• A splitting organic Rankine cycle prototype is established. • Experiment proof that there is a splitting ratio that maximizes the performance. • Compared to single-loop ORC, splitting ORC's performance increases by 8.3%. • Splitting configuration has been proven feasible in improving system performance. The organic Rankine cycle (ORC) is an effective method for internal combustion engines' waste heat recovery. The waste heat from internal combustion engines primarily includes exhaust gas and engine cooling water. However, single-loop preheating and dual-loop ORC configurations are difficult to balance the recovery efficiency of the dual heat sources and the complexity of the equipment. The splitting ORC, as an effective method for enhancing the utilization of waste heat sources, has been proposed. This study developed for the first time a test bench for a splitting ORC with a recuperator (SR-ORC) for internal combustion engines' waste heat recovery, aiming to verify the enhancement effect of the system's performance by splitting the working fluid into two branches to recover the engine cooling water and exhaust gas waste heat respectively. The research results indicate that there exists an optimal working fluid pump speed and splitting ratio to maximize the net output power and efficiency of the system. Moreover, under the engine condition of rotating speed of 1100 rpm and torque of 600 N·m, the system achieves a maximum net power output of 2.81 kW, a maximum internal combustion engine efficiency improvement of 1.6 %, and a maximum thermal efficiency of 10.1 % at the maximum heat source safety operating range. Compared to the non-splitting mode of this test bench with the same engine and heat source condition, these values represent a relative improvement of 8.3 %, 9.6 %, and 27.9 %, respectively. [ABSTRACT FROM AUTHOR]

• Carnot battery using organic Rankine cycle (ORC) as power unit is studied. • Optimal heat storage temperatures and efficiencies are given for various scenarios. • Highest efficiency reaches 1.09, over common scheme combining battery and ORC. • Heat source temperature above 60℃ determines the optimal heat storage temperature. • All the heat exchange processes account for 69.4% of the total exergy loss. Long-term electricity storage technology is essential to achieve a high proportion utilization of fluctuating renewable energy. Carnot battery is an emerging long-term electricity storage technology with lower cost, larger capacity, and no geography restrictions. Using organic Rankine cycle (ORC) as the power unit is beneficial to integrate the low-grade waste heat, achieving a higher energy efficiency for Carnot battery. Heat storage temperature is a key parameter influencing the optimization and performance of ORC-based Carnot battery, but its optimal selection is affected by working fluid type and heat source temperature. For various application scenarios, the optimal heat storage temperatures and the highest power-to-power efficiencies of ORC-based Carnot battery are still unclear. This paper focuses on the ORC-based Carnot battery with various heat source temperatures and working fluid types. Influences of heat storage temperature on the optimization and performance of system are analyzed. Optimal heat storage temperature and the highest power-to-power efficiency at various application scenarios are given. Exergy performance characteristics of ORC-based Carnot battery are revealed, and its energy efficiency superiority is evaluated. Results indicate that the effects of heat storage temperature on system performance differ remarkably for using various working fluid types. The heat source temperature greatly affects the optimal heat storage temperature when it exceeds 60 °C. Exergy loss of system is mainly distributed in heat exchange processes, accounting for 69.4 % of the total exergy loss. The highest power-to-power efficiency of ORC-based Carnot battery can reach 1.09, exceeding the energy efficiency of combining battery and single ORC system. [ABSTRACT FROM AUTHOR]

• Dual heat source high efficiency Organic Rankine cycle system. • Energy management strategies for complex power source vehicle systems. • Strategy parameter optimization and tuning for road condition adaptation. • Results of hybrid and integrated system selection for different road conditions. Developing hybrid electric vehicle architectures and Organic Rankine Cycle-based waste heat recovery for heavy commercial vehicles can improve engine efficiency and reduce energy consumption. Previous studies have focused on a single type of hybrid integrated with a simple Organic Rankine Cycle system, with engine efficiency to be further improved. In order to investigate the applicability of different hybrid configurations in different road conditions, this paper establishes series, parallel and 48 V mild hybrid simulation models based on SIMULINK software, as well as a model integrated with an efficient Organic Rankine cycle system, and operates them on highway and suburban road conditions respectively. The optimal selection of hybrid and integrated configurations under different road conditions is derived: the parallel hybrid and integrated system is selected for highway conditions. For suburban road conditions, hybrid only is selected in series, and 48 V mild hybrid configuration is selected after integrating the Organic Rankine Cycle system. The modelling of the waste heat recovery system and the derived hybrid selection basis provide a reference for energy saving and emission reduction of heavy-duty vehicles. [ABSTRACT FROM AUTHOR]

• Thermodynamic cycle with isothermal expansion. • Isothermal nozzles: theory and design. • Simulation and experimental studies on nozzles with isothermal expansion. • Innovative gas isothermal turbine: design, simulation calculations and experimental studies. The efficiency of power plants with steam or gas turbines depends on the efficiencies of a thermodynamic cycle and devices implementing this cycle. In the case of high power outputs, we cannot expect a significant increase in the efficiency of individual devices. Therefore, what remains is to increase the efficiency of the implemented thermodynamic cycle − the complex Rankine cycle in the case of steam turbines or the extended Brayton cycle in gas turbine units. The efficiencies of these cycles depend on the hot reservoir temperatures, limited by the materials used. The solution seems to be the thermodynamic cycles with the highest efficiency within given temperature limits, the „generalized Carnot cycles". About gas turbines, such a cycle is the Ericsson cycle. The most difficult element of this cycle is carrying out high-temperature expansion. So far, there is no literature data on a technical device implementing this process. In this article, we present a method for designing turbine nozzles for isothermal expansion and the results of experimental tests of the first isothermal turbine. In the case of gas microturbines with a regenerator, isothermal expansion can increase efficiency from 24% to 28% up to 36%. An increase in efficiency of several to a dozen percentage points is expected for Organic Rankine Cycle (ORC) turbines. Due to such significant increases in energy generation efficiency, an isothermal turbine may become a future solution for energy systems. [ABSTRACT FROM AUTHOR]

• An artificial intelligence-based (AI) analysis of a multi-vane expander was done. • Isentropic internal efficiency was observed and predicted in this investigation. • AI prediction used pressure ratio, density ratio, vapor quality, and other parameters. • The validation used experimental data from a retrofitted organic Rankine cycle (ORC). • Vapor quality in an ORC system was measured using capacitive sensors. This study delves into experimental research on a retrofitted organic Rankine cycle (ORC), focusing on the performance of the expansion process near saturated vapor states (from two-phase to superheated conditions). A multi-vane expander was selected for its relevance in small-scale partially evaporated ORC. Several sensors were installed to monitor key parameters, including pressure, temperature, vapor quality, and rotational speed of the expander. The results show that the isentropic efficiency spans a range of 0.37 to 0.49. This variability was observed within an inlet vapor quality of 0.93–0.98, pressure ratios ranging from 5.67 to 10.67, and density ratios ranging from 7.4 to 13.3. In response to the challenge of time-consuming experiments and identification, this research employed deep learning techniques to predict the isentropic efficiency. Two different prediction scenarios were explored: one based on pressure ratio and the other based on density ratio. The results show that predictions based on density ratio offer better accuracy for isentropic efficiency compared to those based on pressure ratio. Three different scenarios for prediction were explored: initially utilizing two input parameters (density ratio and vapor quality), which show root mean squared error (RMSE) and coefficient of determination (R 2) values in the ranges of 0.0136–0.0148 and 0.5832–0.6474, respectively. Subsequent enhancements were achieved by introducing inlet temperature as a third input parameter, improving performance with RMSE of 0.0033–0.0034 and R 2 of 0.9780–0.9793. Moreover, incorporating rotational speed as a fourth input parameter, the prediction was performed with nearly similar RMSE and R 2 values compared to using only three input parameters; it significantly reduces computing times in some cases, achieving speeds relatively 2.25–49.70% faster. This approach demonstrated a well-fitted line and an accurate performance map, establishing its effectiveness in predicting isentropic efficiency. [ABSTRACT FROM AUTHOR]

• An improved self-condensing transcritical CO 2 Rankine cycle was put forward. • The ejector-based method was developed for the self-condensing of CO 2. • Thermodynamic and economic analysis for the system was performed. • Multi-objective optimization and comparative study were carried out. An improved self-condensing transcritical CO 2 Rankine cycle (TCRC) with two-stage ejector on the basis of the preliminarily designed one with an ejector is proposed in this study, aiming to enable the condensation of CO 2 using conventional cooling source and achieve desirable performance. Thermodynamic and economic mathematical models of the improved self-condensing TCRC are developed, and detailed parametric analysis is carried out to investigate the effect of main parameters on both thermodynamic and economic performances of the system. Then the multi-objective optimization is conducted to examine the potential for performance enhancement. Thereafter, a comparative analysis of the performances between the improved self-condensing TCRC and preliminary self-condensing TCRC is performed. Results show that the improved self-condensing TCRC with two-stage ejector outperforms the preliminary one with an ejector in both thermodynamic and economic aspects, achieving a 3.93% increase in maximum exergy efficiency and a 13.84% reduction in minimum unit net power cost through multi-objective optimization. Under optimal conditions, the exergy efficiency for the improved self-condensing TCRC is 45.48% with a unit net power cost of 0.1241$/kWh. [ABSTRACT FROM AUTHOR]

• A rule-based control strategy was developed to schedule a Carnot battery operation. • Coupling of a Carnot battery and district heating allows for thermal peak shaving. • Sensitivity analysis by varying integrated system's key parameters was performed. • The Carnot battery allows for a 47 % downsizing of the district heating substation. • 13 m3 optimal storage size for reference 10 kWe-sized Carnot battery was assessed. To encourage decarbonization and promote a widespread penetration of renewable energy sources in all energy sectors, the development of efficient energy storage systems is essential. Interesting grid-scale electricity storage technologies are the Carnot batteries, whose working principle is based on storing electricity in the form of thermal energy. The charging phase is performed through a heat pump cycle, and the discharging phase is conducted through a heat engine. Since both thermal and electric energy flows are involved, Carnot batteries can be adopted to provide more flexibility in heat and power energy systems. To this aim, efficient scheduling strategies are necessary to manage different energy flows. In this context, this work presents a detailed rule-based control strategy to schedule the synergetic work of a 10-kWe reversible heat pump/organic Rankine cycle Carnot battery integrated to a district heating substation and a photovoltaic power plant, to satisfy a local user's thermal and electric demand. The coupling of a Carnot battery with a district heating substation allows for shaving the thermal demand peaks through the thermal energy stored in the Carnot battery storage, allowing for a downsizing of the district heating substation, with a considerable reduction of the investment costs. Due to the multiplicity of the involved energy flows and the numerous modes of operation, a scheduling logic for the Carnot battery has been developed, to minimize the system operating costs, depending on the boundary conditions. To investigate the influence of the main system design parameters, a detailed and accurate model of the Carnot battery is adopted. Two variants of the reference system, with different heat pump cold source arrangements, are investigated. In the first case, the heat pump absorbs thermal energy from free waste heat. In the second case, the heat pump cold source is the return branch of the district heating substation. The simulation results show that, in the first case, the Carnot battery allows the downsizing of the district heating substation by 47 %, resulting in an annual gain of more than 5000 €. About 70 % of the economic benefit is due to the possibility of reducing the power size of the district heating substation, which can be from 300 to more than 500 kW. The payback period is estimated to be lower than 9 years, while in the second case, the Carnot battery is not able to provide a gain. Eventually, the influence of some parameters, such as the photovoltaic power plant surface, the storage volume, the electricity price profile and the reversible heat pump/organic Rankine cycle specific investment cost, on the techno-economic performance of the system, is investigated through a wide sensitivity analysis. According to the results, the photovoltaic panels surface does not significantly affect the economic gain, while the storage capacity strongly affects the system scheduling and the operating costs. Indeed, it is possible to identify that 13 m3 is the size of the storage volume that minimizes the payback period to 8.22 years, for the considered application. An increase in the electricity price without an increase in the thermal energy price leads to a decrease in economic gain because the benefit brought by the downsizing of district heating is less significant on the economic balance. The specific investment cost of the reversible heat pump/organic Rankine cycle does not influence the operating cost; thus, it does not change the Carnot battery management, nor the economic gain. The specific investment cost affects the payback period, which increases from 8.6 years for a specific cost of 2000 €/kWe to 15.7 years for a specific cost of 5000 €/kWe. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two hydrogen liquefaction cycles are compared thermodynamically & economically. • Waste heat is used to generate both refrigeration & power in two distinct scenarios. • Waste heat recovery in the form of refrigeration is more appropriate than power. • Energy consumption & exergy efficiency for best scenario are 4.32 kWh/kgLH 2 & 53.34%. • Payback period & net benefit for best scenario are 5.942 years & 26.25 MMUS$/year. One of the main problems of hydrogen storage by the liquefaction method is the high specific power consumption. Waste heat recovery from different industries can be used to reduce the power consumption of hydrogen liquefaction cycles. In this paper, industrial waste heat is applied for two distinct purposes: to generate refrigeration using the diffusion-absorption refrigeration cycle (the first scenario), and to produce electricity with the support of the organic Rankine cycle (the second scenario). The diffusion-absorption refrigeration integrated structure generates 0.5786 kg/s liquid hydrogen. Two new integrated scenarios have been compared regarding energy, exergy, and economic analyses to use waste heat. The specific power consumption in the first and second scenarios are 4.320 and 4.359 kWh/kgLH 2 , respectively. The results of the exergy analysis show that the exergy efficiency of the first and second structures are 53.35 and 50.82 %, respectively. Economic analysis of integrated structures developed based on the annualized cost of system method shows that the annualized cost of the product in the first and second systems are calculated at 88.53 MMUS$/year and 82.68 MMUS$/year, respectively. Also, the prime cost of the product in the first and second processes are computed at 4.401 US$/kgLH 2 and 4.320 US$/kgLH 2 , respectively. The findings indicate that utilizing wasted heat for refrigeration production, as opposed to electricity generation in the liquid hydrogen pre-cooling system, is a thermodynamically preferable choice, but it may not be economically viable. The sensitivity analysis of the integrated diffusion-absorption refrigeration structure shows that the payback period and prime cost of liquid hydrogen decrease to 5.041 years and 4.115 US$/kgLH 2 , respectively when the price of electricity decreases from 0.400 to 0.040 US$/kWh. The payback period and levelized cost of liquid hydrogen decrease to 2.886 years and 4.295 US$/kgLH 2 , respectively with a reduction in capital cost from 374.4 to 93.60 MMUS$. [ABSTRACT FROM AUTHOR]

[Display omitted] • Green hydrogen production from biomass waste heat with PEME was investigated from a thermo-enviro-economic point of view. • In the ORC unit of the 'Biomass waste heat - SRC - ORC – PEME' combined system, four different layouts (basic, regenerative, recuperative, regenerative with recuperator) and two different organic fluids (R245fa and R152a) were investigated. • The maximum hydrogen production was 93.81 tons per year, at which point the LCOH was 1.74 $/kg. • With CO2 emission reduction, a carbon gain of 37,527 $ was obtained. In this study, thermodynamic, thermo-economic and enviro-economic analyses of green hydrogen production with biomass waste heat-Steam Rankine Cycle (SRC)-Organic Rankine Cycle (ORC)-Proton Exchange Membrane electrolyzer (PEME) combined system were carried out. After the high-temperature biomass waste heat is used in the SRC unit, the mid-low temperature waste heat released is used in the ORC unit, which is more suitable for these temperatures, to generate electricity. Hydrogen production was investigated by transferring the power generated in the SRC and ORC unit to the PEME unit. Eight different configurations were created by using two organic fluids (R245fa-dry and R152a-wet) in four different layouts of the ORC unit. These layout are basic, regenerative, recuperative, regenerative with recuperator. The effect of turbine inlet temperature variation on system efficiency and hydrogen production rate at different evaporation pressure/critical pressure (Pe/Pcr) ratios in the ORC unit was determined. After determining the maximum hydrogen production point in each configuration, thermo-economic and enviro-economic analysis was performed. With the thermo-economic analysis, the payback period of the system, specific investment cost (SIC-$/kW) and levelized cost of hydrogen (LCOH-$/kg) were determined. For this, the amount of hydrogen produced per year, purchase equipment and other costs (installation, structural, contingencies, etc.) were taken into consideration. Finally, an enviro-economic analysis was carried out to determine the amount of CO2 reduction and the corresponding carbon credit gain (CCG-$). As a result of the study, the best performance was obtained in Conf-4a (Biomass waste heat-SRC-Regenerative recuperator ORC with R245fa-PEME). The amount of hydrogen produced per year, LCOH and CCG were 93.81 tons, 1.74 $/kg and 37,527 $, respectively. [ABSTRACT FROM AUTHOR]

• • Two novel multi-pressure evaporation Brayton combined cycles are proposed. • • Detailed modeling is conducted based on a one-dimensional radial turbine. • • Machine learning is employed to streamline the cycle simulations and improve speed. • • Genetic algorithm is utilized for multi-objective cycle optimization. • • Detailed analysis of the proposed cycles, based on thermal and exergy, is conducted. The Supercritical Carbon Dioxide Brayton combined cycle is one of the most important ways to enhance the performance of the cycle. Since the considerable exergy loss resulting from large temperature differences in the heat exchangers of combined cycles, the multi-pressure evaporation concept was adopted from Organic Rankine cycle research. Two novel multi-pressure evaporation configurations, namely parallel evaporation Brayton combined cycle and series evaporation Brayton combined cycle, are designed with the purpose of enhancing SCO 2 Brayton cycle performance. The performance of the two new cycles was compared with that of the baseline cycle. Moreover, Printed Circuit Heat Exchangers were employed to improve the overall compactness of the cycles. The results from model calculations were utilized to train an Artificial intelligence neural network model using machine learning techniques which allowed to simplify the cycle and improves the computational speed. Subsequently, genetic algorithm was employed to conduct multi-objective optimization on the three cycles. Finally, a detailed exploration was conducted from the perspective of thermal and exergy to elucidate the reasons for the advantages and differences between the two new cycles compared to the baseline cycle. The results indicate that the series Brayton combined cycle exhibits the highest performance, and the combined cycle of multi-pressure evaporation helps to improve the performance of the combined cycle. Compared to the baseline cycle, the combined cycle efficiency of both series and parallel combined cycles has increased from 45.54% to 46.18% and 46.29%, respectively, while the bottom cycle efficiency has improved from 3.81% to 4.93% and 5.03%. The ratio of heat exchange area to net output power increased from 0.6051 to 0.6614 and 0.6740 for the parallel and series cycles, respectively. Thermal analysis shows that, the fundamental purpose of changing the layout is to improve the specific power per unit of working medium in the cycle. Exergy analysis shows that, the two new combined cycles improve cycle efficiency by reducing exergy losses in the intermediate heat exchanger. Compared to the parallel version, the series version's staged compression allows for a lower temperature difference in intermediate heat exchanger 1, resulting in smaller exergy losses and higher cycle efficiency. This work will contribute to an enhanced understanding of Supercritical Carbon Dioxide combined cycles within the academic community and the introduction of multi-pressure evaporation will further improve the performance of these important cycles. [ABSTRACT FROM AUTHOR]

• Novel cascade: Kalina & Organic Rankine cycles for cooling, green hydrogen. • Solar-biomass hybrid, Kalina & ORC power generation, dual evaporator system. • Payback: 2 years (ORC-VCRS), 3 years (Kalina topping, bottoming ORC) at $6/kg H 2 , $4/kW cooling. • Achieves energy ratio of 0.76, 21.56% exergy efficiency, $58,677 total cost. A novel cascade system of Kalina and Organic Rankine cycle for cooling and green hydrogen production was proposed. The cascade system is designed to utilizes the heat effectively with heat recovery components for sustainable cooling and green hydrogen. The proposed system consists of a solar-biogas hybrid heat source, Kalina and ORC power generation system, dual evaporator vapor compression cooling system and solid oxide electrolyser. The system's performance is evaluated based on the availability of low-temperature heat sources (90 to 150 °C) and medium-grade heat sources (190–280 °C). It is assessed for its capability to provide cooling only or in combination with hydrogen production, and their efficient utilization is compared from energetic, exergetic, environmental, and economic perspectives. To optimize this innovative system, a multi-objective evolutionary approach is employed, considering operating conditions as constraints and incorporating performance metrics for all criteria as objectives. Utilizing multi-objective decision-making techniques, diverse optimal points are pinpointed within the trade-off space, enabling real-time adaptive responses to changes in weather, energy demands, and biogas availability. The net present value analysis demonstrates that, assuming a hydrogen selling price of $6 per kilogram and cooling costs of $4 per KW the payback periods are calculated to be 2 years for the ORC-VCRS cycle and 3 years for the integrated Kalina topping with bottoming ORC cycle. The multi-objective optimization results indicate that the optimum operating conditions for the cascade system involve boiler, absorber, and condenser temperatures set at 196 °C, 110 °C, and 25 °C, respectively. Under these conditions, the system achieves an energy utilization ratio of 0.76, an exergy efficiency of 21.56 %, and a total cost of $58,677. [ABSTRACT FROM AUTHOR]

• A novel onboard CO 2 capture system is proposed based on zero energy increment. • Ship waste heat and LNG cold energy are recovered for the proposed system. • 4E analyses and multi-objective optimization of the system are carried out. • CO 2 capture cost and payoff period are optimized at 95.6 $/tonCO 2 and 11.3 years. • Zero energy increment CO 2 capture system is feasible in maritime industry. In this paper, a novel zero energy increment onboard carbon capture (ZEIOCC) system was proposed. With LNG cold energy and waste heat recovery, the ZEIOCC system integrated organic Rankine cycle (ORC), CO 2 liquification, and CO 2 capture unit. The ZEIOCC system performances were evaluated via energy, exergy, economic, and environmental (4E) analyses. Parametric studies were performed to investigate the effects of the flue gas mass flow rate (m fg), liquid to gas ratio (L/G), and the pinch point temperature difference at the outlet of the ORC condenser (T pin) on the system performance indicators. Furthermore, multi-optimization was conducted with the product of energy-exergy efficiencies (η en,sys * η ex,sys), the total capital investment cost (C I,tot), and the carbon reduction capacity (ξ) as objective functions. Two decision methods TOPSIS and LINMAP were introduced to find the most optimal point from the Pareto front. Under the basic condition, the proposed system proved its advantages of high efficiency, diversified energy output, fast return on investment, and efficient CO 2 capture capacity. The results of optimization showed that the system performances meet all the requirement of the design goal. The optimal energy-exergy efficiencies is 10.06 %, the carbon reduction capacity is 28.01 %, and the total capital investment cost is 7.06 × 106 $. Under the optimal condition, the system net output power (W net), energy efficiency, and exergy efficiency are 12 kW, 20.53 %, and 49.02 %, respectively. Meanwhile, the payoff period (POP) and the CO 2 capture cost (CCC) are 12.0 year and 99.9 $/tonCO 2 , respectively. [ABSTRACT FROM AUTHOR]

• A waste heat recovery for an offshore oil platform was analyzed. • The heat recovery device is the most irreversible in the organic Rankine cycle. • The organic Rankine cycle contributes to electricity generation up to 20.3%. • The organic Rankine cycle contributes to increase up to 11% in overall efficiency. • A net present value of up to USD 16.84 million is possible with the proposed change. The organic Rankine cycle has been widely explored for energy recovery from several heat sources. In this paper, the maximization of the energy recovery of the exhaust gases from the General Electric LM 2500 gas turbines in a floating production offloading unit is studied in order to meet the demands of heat (pressurized hot water) and electricity over oil production lifetime. An off-design model of the system is developed to check the viability of an organic Rankine cycle under dynamic operating conditions. Energy and exergy analysis of the proposed system are conducted to determine main irreversibilities and performance characteristics of the system and, finally, the economic benefits of the energy recovery system application are discussed. The organic Rankine cycle is very flexible in the heat recovery in dynamic demand conditions, contributing up to 20.3% in electricity generation, which causes an increase in overall system efficiency of up to 11.3% and up to 18.3% in the utilization factor, as well as an average reduction of 22.0% in carbon dioxide emissions in the floating production offloading unit electricity generation process. The exergy efficiency of the system reaches 55.8% and the heat recovery devices are the most irreversible equipment in organic Rankine cycle, contributing up to 68% of the total exergy destroyed. The economic analysis demonstrated the attractiveness of the organic Rankine cycle implementation, allowing a net present value to Brazil's current economic scenario of up to USD 16.8 million. [ABSTRACT FROM AUTHOR]

• Biomass retrofit for existing solar ORC plants can improve efficiency and flexibility. • Retrofit can increase working hours and economic competitiveness of solar ORC plants. • Relative deviation of implemented ORC off-design models from real plant data is 3%. • The proposed hybridization strategies can be extended to new plant designs. • The benefits of implemented hybrid solar-biomass schemes are higher for new designs. This study aims to investigate techno-economic benefits of biomass retrofit for practical concentrated solar power (CSP) organic Rankine cycle (ORC) power plants. In this regard, technical parameters of an existing CSP-ORC plant currently running in Ottana (Italy) have been adopted for analyses. The plant consists of linear Fresnel collectors solar field, coupled with a two-tank oil-based thermal energy storage (TES) device, feeding a 630 kWe ORC plant. Fixed and modular biomass hybridization approaches were proposed for retrofit. In the fixed approach, biomass furnace constantly supplies thermal energy to ORC such that a pre-determined minimum power production is guaranteed, with or without solar thermal energy availability. In the modular approach, biomass furnace is regulated to supply balance thermal energy needed to continuously operate the ORC at its full capacity. Furthermore, beyond the biomass retrofit case study, a newly integrated design case study was introduced, with modified solar field and TES capacity. By using the meteorological conditions of Ottana, results of techno-economic performance for the retrofit case study showed that annual net electrical efficiency increases by 4–5 percent points, relative to the solar-only ORC plant. Marginal levelized cost of electricity (LCOE) of between 103 €/MWh and 109 €/MWh were obtained. Also, marginal net present value (NPV) ranges from 1.83 M€ to 3.22 M€. For the newly integrated design case study, results showed that design case with modular hybridization approach represents the highest annual net electrical efficiency, at 19.8%. For this approach, economic results showed that LCOE ranges between 130 €/MWh and 146 €/MWh. Beyond current state-of-the-art, the results obtained in this study show that biomass retrofit for existing CSP-ORC plants can lead to higher full-load operation hours and more prospective plant economics. Moreover, the implemented modular approach enables scheduled power profile to be followed, thereby enhancing plant dispatchability. [ABSTRACT FROM AUTHOR]

• A novel trigeneration system is proposed to recover diesel engine waste heat. • ORC has been combined with absorption-compression cooling and power system. • Thermo-economic analysis and parametric study have been carried out. • Applying screw expander improves the total exergy performance. • Applying compressor causes total performance to decrease. A novel trigeneration system consisting of organic Rankine cycle (ORC) and absorption-compression cooling and power system (ACCPS) is proposed to recover diesel engine waste heat. A compressor is used between evaporator and absorber in ACCPS. Moreover, a screw expander is applied in ACCPS to increase power generation and domestic hot water (DHW) is prepared by DHW heat exchanger (HX) in ORC. Exergoeconomic analysis using the specific exergy costing (SPECO) method is implemented for system assessment. Base case and parametric analysis as well as the effects of using expander and compressor in ACCPS on total performance of the system are examined. The results show that the best thermo-economic performance of the system is achieved when ORC condensation temperature and generator outlet temperature have respectively the lowest (85 °C) and the highest (80 °C) values. It is difficult to select the proper ORC evaporation temperature, because the lower this temperature is, the higher net power output is obtained while higher ORC evaporation temperature leads to less total cost rate and more total energy efficiency of system. Moreover, system exergy efficiency has an optimum point versus variation of ORC evaporation temperature. By increasing expander inlet steam quality, ACCPS coefficient of performance (COP) and total energy efficiency of system decrease; however, due to increase in net power output and system exergy efficiency respectively equal to 18.23% and 3%, total system performance improves from exergy viewpoint. By utilizing a compressor in ACCPS and increasing its pressure ratio, the performance of ACCPS improves from energy viewpoint; however, system thermo-economic performance decreases. [ABSTRACT FROM AUTHOR]

• A novel CCHP-ST-ORC system was introduced and compared with CCHP, CCHP-ST systems. • Three CCHP systems were evaluated thermodynamically. • Effect of operating parameters on system thermodynamic performance is presented. • A new operation strategy for CCHP-ST-ORC system was proposed and adopted in a studied case. Combined cooling, heating and power systems (CCHP) have received wide attention recently because of its prominent role in energy utilization. It could both decrease the energy consumption and improve the overall energy efficiency. In this paper, a novel coupled CCHP system was proposed which is composed of a conventional CCHP system, a solar thermal utilization (ST) subsystem and an organic Rankine cycle (ORC) subsystem. The CCHP-ST-ORC system has been evaluated thermodynamically, and compared with CCHP system and CCHP-ST system, which is based on the G ICE (rated internal combustion engine capacity) of 100 kW. Further, through the parametric study for CCHP-ST-ORC system, the effect of several operating parameters on the system thermodynamic performance is explored. Finally, a new operation strategy for CCHP-ST-ORC system was proposed and adopted in a residential building, which presents a better thermodynamic economy than CCHP-ST system. As the result, CCHP-ST-ORC system could generate an additional electricity of 5.1 kW compared with other two systems, which is at the expense of 39.3 kW heat. Further, it could expand the maximum power generation to 108 kW. The case study shows that the primary energy ratio of CCHP-ST-ORC system is 60.2% that is much higher than the 37.6% of CCHP-ST system. The results also indicate that the CCHP-ST-ORC system consumes 9.81 × 104 m3/year of natural gas, with a 12.4% reduction in energy consumption than CCHP-ST system. Therefore, these findings can promote the sustainable development of new energy utilization models, especially the coupling CCHP system. [ABSTRACT FROM AUTHOR]

• To Propose a novel renewable CCHP system. • To apply a dynamic model of thermal storage system to proposed CCHP. • To Apply different evolutionary algorithms on proposed CCHP system. • To investigate the effect of different interest rates on Pareto frontier. • Comparison of Pareto frontier of different evolutionary algorithms. In this research paper, a novel combined, cooling, heating and, power (CCHP) system is proposed consisting of Parabolic trough solar collectors (PTSC) field, a dual-tank molten salt heat storage, a Proton exchange membrane electrolyzer (PEME), an Organic Rankine Cycle (ORC) and a single effect Li/Br water absorption chiller. The first law of thermodynamics was applied for analyzing the proposed CCHP system. A multi-objective optimization is conducted with respect to exergy efficiency and total cost rate as two objective functions. In order to determine the optimal point in multi-objective optimization, NSGA-II algorithm was applied for the optimization purpose. Matlab software and python are employed to determine the system optimum operating conditions. The optimum solutions for the NSGA-II multi-objective optimization are 79% and 0.058 ($/s) for exergy efficiency and total cost rate, respectively. The results of single objective optimization are 0.0447 ($/s) for the economic objective function and 87.53% for the exergy efficiency objective function. The sensitivity of the Pareto frontier for different interest rates is also investigated and the results show that at the lower system exergy efficiency, the influence of the interest rate is more significant. In addition, Generalized Differential Evaluation (GDE3), Indicator-based evolutionary algorithm (IBEA), speed-constrained Multi-objective (SMPSO), and strength Pareto Evolutionary algorithm (SPEA) algorithms are also applied for the optimization of the proposed CCHP and the results of the algorithm are compared with each other. The IBEA algorithm was found the best approach to obtain the Pareto optimum solution. The comparison between NSGA-II and IBEA shows that the IBEA exergy efficiency of the optimum solution increase by 2.5% in comparison with NSGA-II and the IBEA cost rates decrease by 7% in comparison with NSGA-II. [ABSTRACT FROM AUTHOR]

• Performances of four transcritical CO 2 cycles are analyzed. • Thermo-economic performance of the CO 2 cycle with a reheater is higher. • The transcritical CO 2 cycle with a reheater is compared with Kalina and ORC. • The net power of the CO 2 cycle is the largest. • The economic performance of the Kalina cycle is the best. The utilization of low-temperature heat energy can improve energy conservation and protect the environment effectively. A transcritical CO 2 power cycle is normally considered not competent with an organic Rankine cycle (ORC) for low-temperature applications. In this study, the advantages of transcritical CO 2 power cycle for low-temperature heat sources are explored from a thermo-economic viewpoint. The performances of four different transcritical CO 2 power cycles are evaluated theoretically and then compared with an ORC and a Kalina cycle. First, a mathematical model is established to estimate the thermodynamic and economic performances of the power cycles including a basic cycle, a recuperated cycle, a regenerative cycle with an open-feed heater, and a cycle with a reheater. Printed circuit heat exchangers are used for the evaporators and air-cooled heat exchangers are adopted for the condensers. Aspen EDR is used to obtain the areas of the air-cooled condensers and the overall thermo-economic performance is determined by Matlab. Then, one suitable cycle is selected and compared with the ORC and the Kalina cycle for a low-temperature heat source. The results indicate that the cycle with a reheater is preferable among the four transcritical CO 2 cycles. Compared with the ORC and the Kalina cycle, the net power output of the transcritical CO 2 cycle is the largest and the economic performance is between the Kalina cycle and the ORC. However, CO 2 is cheaper, more environmentally-friendly, and safer than organic fluids. Therefore, from a thermo-economic viewpoint, transcritical CO 2 power cycle is competent with ORC for low-temperature heat sources. [ABSTRACT FROM AUTHOR]

• Systems of medium temperature fluegas energy utilization are compared and optimized. • Influence of reheat stages on power plant efficiency are calculated. • Cold end systems including intercooling and waste heat recovery are compared. • Efficiencies of complex and simple optimized systems achieve 49.32% and 48.52%. The integration of supercritical CO2 (SCO2) cycle instead of steam Rankine cycle may be a revolutionary technique to increase the efficiency of coal-fired power plants. To effectively extract exergy from the fluegas and convert exergy to power, the characteristics of hot end (heat reservoir) and cold end (heat sink) should be fully considered, and the system multi-parameters should be optimized. In this study, based on a benchmark coal-fired power plant integrated with a recompression SCO2 power cycle, quantitative efficiency enhancements of system improvements of the hot end and cold end for SCO2 power cycle are calculated and compared. The optimized efficiency of benchmark coal-fired plant integrated with recompression SCO2 power cycle is 45.43%. When the fluegas at the economizer outlet is effectively used, the power plant efficiency can be increased by 1.32%. With single and double reheats to decrease the heat transfer irreversibility of the hot end, the power plant efficiency can be increased by 1.77% and 2.24%, respectively. Cold end optimization with single intercooling and cold air preheating can increase the power plant efficiency by 0.32% and 0.33%, respectively. Finally, a simple structure system and a complex structure system are proposed. With optimal system parameters, the power plant efficiencies of the complex and simple systems are 49.32% and 48.52%, respectively. [ABSTRACT FROM AUTHOR]

• Possibility of integrating thermoelectric with gasifier cycle is investigated. • Different locations for adding TEG in a biomass power generation is investigated. • Adding thermoelectric to the condenser section increases efficiency from 16.76% to 17.93%. • Economic evaluation indicated the conditions under which the system is profitable. Thermoelectric waste heat recovery systems (WHRSs) can be used appropriately to recover wasted heat from various industrial processes. In the current work, new thermodynamic modeling was developed to harvesting waste heat from an integrated system includes an externally fired gas turbine and a biomass gasifier by three thermoelectric WHRSs. The biomass system consisted a gas turbine cycle, an organic Rankine cycle (ORC) and a domestic water heater were first thermodynamically modeled, and then effects of adding thermoelectric WHRSs to different locations of the system were investigated. It is observed that first law efficiency of the system (η 1) will become 17.11% (an increase of 0.35%) if the total output heat from the stack enters W H R S s. The efficiencies of the system can be increased from 16.76% to 17.93% by placing a WHRS on the condenser of ORC. Moreover, the operating parameters have a significant effect on the integrated system efficiency; the influence of increasing α G E on the efficiencies is in contrast to the effect of enhancing α c o n d . In addition, an economic assessment of integrating WHRSs with the biomass gasifier integrated system is conducted and the conditions are indicated under which the proposed system is profitable. Furthermore, the results of genetic algorithm based multi-objective optimization shows that with the use of γ DU = 2 and γ L , O R C = 30 defined thermal efficiencies are at their optimum state. [ABSTRACT FROM AUTHOR]

• Transcritical-subcritical dual-loop organic Rankine cycle is proposed. • Zeotropic mixtures are selected as working fluid of dual loop. • System without and with regenerator is analyzed and compared. • Optimization and design of parameters are carried out. • Zeotropic mixtures show 5.48–20.00% higher power output than pure fluids. Dual-loop organic Rankine cycle is a great potential technology to recover engine waste heat for energy saving. Transcritical cycle can improve exergy efficiency of heat transfer process in the evaporator, and zeotropic mixtures furtherly can improve thermal match with heat source and sink. Thus, a transcritical-subcritical dual-loop organic Rankine cycle system using zeotropic mixtures is adopted for engine waste heat recovery, and system without and with regenerator is considered. The whole system is assumed in the steady state, R600a/R601a and R134a/R245fa mixtures are used as working fluid of transcritical and subcritical cycle, respectively. Parametric analysis and optimization about turbine inlet temperature and pressure of high-temperature loop, evaporation temperature of low-temperature loop are carried out. According to the results, the designed parameters have great effect on performance of system, and for the system without and with regenerator, the optimal turbine inlet temperature, pressure and evaporation temperature are 260 °C, 11 MPa, 85 °C and 250 °C, 10 MPa, 85 °C respectively. Moreover, the effects of components of mixtures on the performance of system are analyzed. The results demonstrate that system with zeotropic mixtures can significantly improve the performance of system. The system without regenerator using R600a/R601a (0.2/0.8) and R134a/R245fa (0.4/0.6) shows the maximum power output of 97.49 kW which is higher 5.48–20.00% than pure fluids, and system with regenerator using R600a/R601a (0.3/0.7) and R134a/R245fa (0.4/0.6) achieves the maximum power output of 97.95 kW, increment of 6.52–19.78% compared with using pure fluids. And the power output of engine can be improved by 9.79% and 9.83% for the system without and with regenerator, respectively. Furthermore, the exergy destruction analysis demonstrates that zeotropic mixtures can reduce heat transfer exergy destruction and total exergy destruction of system. [ABSTRACT FROM AUTHOR]

• A direct evaporator for an organic Rankine cycle plant was designed and tested. • Exhaust waste heat from a biogas combined heat and power plant was exploited. • A detailed design method for a shell and helical coils evaporator was presented. • The heat exchanger was manufactured and tested to validate the design method. • The apparatus had a reliable operational behavior and a compact size. A direct evaporator for a high temperature organic Rankine cycle (ORC) plant with toluene as a working fluid is designed and tested. The exhaust gas from a 800 kWe combined heat and power plant is cooled on the shell side of the present heat exchanger, while the working fluid is heated and evaporated within eight helically coiled tubes, constituting a tube bundle. A method to obtain optimal design parameters for this type of heat exchanger is presented, considering the heat source, the ORC and the available space at the test site. After manufacturing, the apparatus is tested to validate the design procedure, focusing on the employed heat transfer and pressure loss correlations on the shell side. It is shown that the predicted values of the overall heat transfer coefficient and the shell side Nusselt number are in good agreement with experimental data, showing a maximum deviation of 5.5%. The measured shell side pressure loss is slightly higher than the predicted value, indicating that the correlation underestimates the pressure loss coefficient by up to 7% at low Reynolds numbers, but has a good accuracy at higher Reynolds numbers. It is observed that it is essential to adjust the mass flow rate of the working fluid in each coil to obtain a homogenous vapor quality. A reliable operation of the direct evaporator with a maximum heat flow of 225 kW is shown. [ABSTRACT FROM AUTHOR]

• Dual-pressure evaporation cycle and zeotropic mixtures were efficiently combined. • Application potential and reached exergy efficiency were evaluated. • Characteristics and variations of irreversible loss distribution were revealed. • Proposed cycle obtains the highest exergy efficiency for heat sources below 180 °C. • Relative increment in efficiency exceeds 11.6% compared with conventional cycles. Organic Rankine cycle is a power system for the widely use of medium- to low-grade (<200 °C) thermal energy. Adopting the dual-pressure evaporation cycle and zeotropic mixtures are important approaches to increase the efficiency of organic Rankine cycle system. The combination of two approaches presents considerable potential to integrate their advantages and further increase the system efficiency significantly. However, for the dual-pressure evaporation organic Rankine cycle using zeotropic mixtures, the studies on the exergy performance are blank up to now. The obtained efficiency increments by combination, reached exergy efficiency, and characteristics of irreversible loss distribution remain unclear. This study carried out a comprehensive exergy analysis on the dual-pressure evaporation organic Rankine cycle using isobutane/isopentane mixtures. The exergy efficiency and irreversible loss distribution were analyzed. The superiority of combining dual-pressure evaporation cycle and zeotropic mixtures was evaluated. Results show that the largest exergy efficiency of dual-pressure evaporation cycle using isobutane/isopentane mixtures is 43.1%–61.7% for heat sources of 100–200 °C, and the largest exergy efficiency initially increases and then decreases with increasing heat source temperature. The largest irreversible loss occurs in the heat absorption, expansion, and heat release processes for heat sources of 100–160 °C, 170–180 °C and 190–200 °C, respectively. The exergy efficiency of dual-pressure evaporation cycle using isobutane/isopentane mixtures is the largest for heat sources below approximately 180 °C, and the maximum relative increments are 11.6% and 25.6% compared with the dual-pressure evaporation cycle using isobutane and single-pressure evaporation cycle using isobutane/isopentane mixtures, respectively. [ABSTRACT FROM AUTHOR]

• A triple ORC system for LNG-fueled vessels with waste heat and cold energy recovery was proposed. • The system was optimized by two synthetic objectives with 15 working fluids. • The best operating point was obtain by multi-objective adaptive firefly algorithm. • The exergy and pinch analysis were carried out to make further improvement. Due to the high level of pollutant emissions from traditional marine diesel engines, Liquefied Natural Gas (LNG) as clean energy is becoming a better choice for main engines to replace the traditional fuels. Meanwhile, in order to improve the energy efficiency of the marine power system, the Organic Rankine Cycle (ORC) has been regarded as the most suitable solution to recover the waste heat for the power generation of vessels. In this paper, both the waste heat of the main engine and the cold energy of LNG have been fully considered, and a novel triple ORC process has been proposed for the waste heat and cold energy recovery of LNG-fueled vessels. It adopts the exhaust gas of the main engine and the cooling water from the engine jacket as heat sources, and uses the cold energy of LNG and the sea water as cold sources. Based on the 15 optional working fluid conditions, the heat source utilization rate, system exergy efficiency, net output power, and system cost are, respectively, combined as two objectives, and the multi-objective adaptive firefly algorithm is used to optimize the thermodynamic performance of the system. The optimization results of different heat and cold sources as well as the design parameters have been discussed. Finally, the system's exergy loss has been analyzed to make suggestions for further improvement. The results show that this novel ORC system can better meet the energy recovery requirements of LNG-fueled vessels, with higher net output power, lower cost, and greater energy recovery efficiency. The largest exergy loss of the system exists in the condensers of the stages 2 and 3, and the expanders in the various stages. Therefore, subsequent cooling energy recovery and the use of Stirling engines can be considered to further improve the system efficiency. [ABSTRACT FROM AUTHOR]

• A new designed multi-generation system is investigated. • Thermodynamic, thermoeconomic and exergoenvironment analyses are conducted. • Multi-criteria optimization is implemented to specify optimum design of the system. In the present work, a new design of a multi-generation system based on biomass and solar energy with the purpose of generating electric power, heating, cooling, hydrogen, and potable water is introduced. The system comprises a steam Rankine cycle, double effect absorption chiller, proton exchange membrane electrolyzer, multi-effect desalination, and parabolic trough solar collector. A thermodynamic analysis is carried out to present the thermodynamic feasibility and deficiencies by calculating the irreversibilities occurring in the components. Exergoeconomic modeling yields the product cost rate of different products and cost flow in the studied system. Also in order to determine the amount of environmental effect of the suggested system, the exergoenvironmental study is performed and discussed. Results demonstrate that energy efficiency, exergy efficiency, total product cost rate and exergoenvironmental impact improvement of 82.4%, 14%, 0.84 $/s and 0.15 are achievable for the multi-generation system respectively. Finally, multi-criteria optimization approach based on a genetic algorithm is applied to specify the optimum design of the system considering the improvement of thermodynamic and thermoeconomic performance. By extracting the Pareto frontier, a design scheme related to exergy efficiency of 16.53% and product cost rate of 0.71 $/s is selected as an optimal design. [ABSTRACT FROM AUTHOR]

• The main objective is to introduce an economic and feasible hybrid energy system. • The hybrid ORC has a lower COE and NPC, compared to the stand-alone ORC. • The overall exergy efficiency of the hybrid ORC is 7.29%. • The optimum energy system is the hybrid PV-wind-diesel-battery. The main objective of this investigation is to introduce an economic and feasible hybrid energy system to provide the required load for a household in Rayen, Iran. The case study is a building with 20 families. The power consumption of a family at a peak is considered by 4 kW. So, this combined system must provide a power of 80 kW. First a hybrid organic Rankine cycle is proposed and assessed by exergy and exergoeconomic methods. The results of exergy analysis indicate the overall exergy efficiency of the system is 7.29%. As well as, the greatest exergy destruction is related to the photovoltaic panels with a value of 337.16 kJ. The outcomes of the exergoeconomic assessment showed that, the highest and lowest capital investment cost rate belong to the photovoltaic panels (54233 $/year) and condenser (7092 $/year), respectively. Also, the product cost rate is calculated by 5.2 million $/year. In continue, to identify the key parameters which influence on the total performance of the ORC system, a parametric analysis is done. Because of the hybrid organic Rankine cycle has a high amount of the cost of energy, seven renewable hybrid energy systems are proposed and modeled by HOMER software. The results show the optimum energy system for this residential area is the hybrid PV – wind-diesel – battery. This configuration has a net positive cost of 268,592 $ and a cost of energy of 0.197 $/kWh. At the end of this study, to find the impact of the variations of the fuel cost and peak load on system performance, a parametric analysis was carried out. [ABSTRACT FROM AUTHOR]

• Dynamic characteristics of ORC using mixture fluid are analyzed. • The improved dynamic model is better adapted to the phase change process. • The areas required for different evaporation stages are investigated. • Different control strategies are proposed from external controllable conditions. The Organic Rankine Cycle (ORC) system is a rather promising technology for waste heat recovery. However, waste heat source generally presents a fluctuating behavior, which is a big challenge to the security and efficiency of the ORC. An improved dynamic model of ORC system with zeotropic mixture is firstly developed, which can be better adapted to the phase change process of working fluid. Accordingly, dynamic behavior of the ORC and dynamic distribution of evaporation stages are investigated. Besides, three control strategies are proposed to improve the performance of steadiness with external controllable conditions. Results show that a sudden abnormal change occurs in specific enthalpy of working fluid at the evaporator outlet when different disturbances are imposed to the system. It is found that the proposed control strategies are adapted to different heat source fluctuation. The control strategies with feedforward control system work well with low frequency variation of heat source temperature. [ABSTRACT FROM AUTHOR]

• Development of a 1000 W micro-turbine for an organic Rankine cycle. • Polymeric materials used as the functional parts of the micro-turbine. • Achieved steady rotational speed of 32,000 rpm and peak speed of 40,000 rpm. • Aerodynamic efficiency predicted to be up to 0.66. This paper presents the experimental advances on the implementation of structural polymeric materials in a micro-turbine-generator for an organic Rankine cycle (ORC) and through testing provides an insight of its performance. The aim is to create awareness of the huge techno-economical potential that polymers represent as metal replacement in ORC applications. A micro-turbine-generator is developed considering R245fa as the working fluid. The unit is built using polymeric components; these components include an impeller made from polyether-ether-ketone and a nozzle body made from polyethylene. A program for the simulation of the micro-turbine performance is developed, a series of tests are conducted with compressed air and the performance with R245fa is predicted. The impeller was experimentally demonstrated to be able to withstand a rotational speed of 32,040 rpm whereas the predicted results showed the aerodynamic efficiency and the aerodynamic power to be around 0.65 and 1200 W respectively. The future of polymeric materials in ORC looks promising though a long-term test using the refrigerant as the working fluid is still needed to verify material-fluid compatibility, lifespan and resistance to fatigue. [ABSTRACT FROM AUTHOR]

Highlights • Introducing a novel geothermal driven multi-generation system. • Using a cascade of two ORC cycles between geothermal heat source and LNG heat sink. • Carrying out a parametric study to illustrate the influences of different parameters. • Techno-economic optimization of the proposed system by coupling ANN with GA. Abstract LNG re-gasification process usually occurs through heat exchange with seawater, causing a large amount of exergy destruction. However, in this study, this process is employed as the heat sink of a geothermal driven multi-generation system. Because of the high temperature difference between the heat source (geothermal fluid) and the heat sink (LNG re-gasification process), a cascade of two organic Rankine cycles is placed between them. The system also includes an absorption refrigeration cycle and a PEM electrolyzer to form an efficient multi-generation system. A comprehensive analysis is carried out to assess the performance of the system both thermodynamically and economically. Furthermore, the paper presents a parametric study to illustrate the influences of major parameters on the system performance. To simultaneously optimize total cost rate, hydrogen production capacity, and exergy efficiency of the system, a multi-objective optimization procedure is developed (through coupling Genetic Algorithm with Artificial Neural Network) and applied to the system. Consequently, a system design with a total cost rate of 423.5 ($/hr), hydrogen production capacity of 276.1 (kg/hr), and exergy efficiency of 24.92% is obtained as the optimal solution. The proposed system shows great improvements in cooling, power generation, and hydrogen production capacities compared to literature. [ABSTRACT FROM AUTHOR]

Highlights • Triple Gas-Mercury-Steam combined system is developed. • Performance simulation of combined system is conducted based on thermo-ecology. • Influence of design and operating parameters on system performance is investigated. • Parametrical variations are carried out to optimize system performance. Abstract In this study, thermo-ecology based performance investigations for a combined system consists of Brayton gas cycle, Rankine mercury cycle and Rankine steam cycle, which is called Gas/Mercury/Steam power generation system (GMSPGS), are carried out depending on the most used performance characteristics such as power generation, density of power generation, destructed exergy, second law efficiency (exergetic performance efficiency) with respect to destructed exergy and power generation, ECOP and EFECPOD. The impacts of system design and operating parameters for gas cycle part, mercury cycle part and steam cycle part on the performance characteristics are parametrically examined in detailed. The used parameters are inlet temperature and pressure of the air, mass flow rate of the air, pressure ratio, equivalence ratio, turbine speed, residual gas fraction (RGF), mercury temperature of the gas-mercury heat exchanger (GM-HEX), low-pressure mercury turbine (LPMT), medium-pressure mercury turbine (MPMT), high-pressure mercury turbine (HPMT), steam temperature at the mercury-steam heat exchanger (MS-HEX), the pressures of low-pressure steam turbine (LPST), medium-pressure steam turbine (MPST), high-pressure steam turbine (HPST), open feed water heater (OFWH) and condenser (COND). The results demonstrated that the performance specifications are substantially affected by the component properties. Beside the theoretical model examined in the paper, a data obtained from artificial neural networks (ANNs) is also presented to model the system. It is shown that a limited number of parameters is enough for good approximations. [ABSTRACT FROM AUTHOR]

Highlights • A thermodynamic empirical correlation is obtained based on the separability of ORC. • Ω ORC , o p t = C wf · T cri m · ω wf n · T hs o is established for predict the performance of ORC. • Critical temperature and acentric factor are the key properties for working fluid selecting and designing. Abstract This paper establishes an empirical correlation based on the separability of thermodynamic cycle, which could characterize the thermodynamic performance of organic Rankine cycle (ORC), resembling heat transfer empirical correlation. In this research, we found that the thermal efficiency, exergy efficiency and net output power of ORC can be expressed by the heat source characteristics (T hs , heat source temperature) and two key physical properties of working fluids (T cri , critical temperature; ω , acentric factor). That is, Ω ORC , o p t = C wf · T cri m · ω wf n · T hs o.Taking subcritical ORC as an example, the empirical correlation of the optimal power generation and its corresponding optimal evaporation temperature could be provided through proposed method. The results reveal that the empirical correlations have the high prediction accuracies (the determination coefficient R2 are both about 0.97) when comparing with traditional numerical calculation. The application of correlation could avoid the complex process of iteration for calculation convergence and calling properties, so it is more convenient and faster than traditional methods when used to predict the performance of ORC or to select and design the working fluids. [ABSTRACT FROM AUTHOR]

Highlights • A combined sensible, latent, and thermochemical energy storage system. • High energy storage density of up to 1600 kJ/kg. • Round trip efficiency is found to be about 50% • Combined storage mechanism is validated in cycling thermogravimetric analyses. Abstract In this article, a unique phase change redox (PCR) system capable of converting surplus electricity to sensible, latent, and thermochemical energy is proposed as an alternative technology for utility-scale energy storage. During the energy charging period, the system utilizes external heat to reduce and melt solid CuO into molten CuO/Cu 2 O at a high temperature in a reduction reactor. The external heat can be provided by Joule heating using the surplus electricity from the power grid or renewable energy plants (solar/wind). In this way, the surplus electricity is stored in the forms of sensible, latent, and thermochemical energy. A high value-added by-product, oxygen, can be produced simultaneously, which further enhances the economic competitiveness of the proposed system. During the energy discharging period, the molten CuO/Cu 2 O is oxidized and cooled in an oxidation reactor using air. In this step, the stored energy is released and transferred to the high-pressure and high-temperature air, which can be further converted into power via an air Brayton cycle coupled with a bottoming organic Rankine cycle. The simulation package, Aspen Plus v10, is used to develop a thermodynamic model of the PCR system, in which its technical performance and influential parameters are examined in details. The simulation study shows that the PCR process can achieve a round trip efficiency of about 50% with an energy storage density of up to 1600 kJ/kg. The parametric analysis reveals that the round trip efficiency of the PCR system is greatly influenced by the compression ratio, while the energy storage density and oxygen production are affected by the temperature and oxygen partial pressure of the reduction reactor. Apart from the simulation study, thermogravimetric analyses on phase change redox cycles are also carried out. The experiment results are found to successfully validate the key energy storage mechanism behind the PCR process, namely the reduction, melting, solidification, and oxidation processes. The reversibility and stability of the PCR process over 10 cycles are found to be excellent with minor degradation and enthalpy changes. [ABSTRACT FROM AUTHOR]

Highlights • Two-objective optimization of a waste heat recovery system is proposed. • Maximization of power output and minimization of heat exchangers areas are applied. • Significant reduction in area with acceptable reduction in power is obtained. • Four working fluids are considered and ethanol is suggested as the best one. Abstract Recovering waste heat from the exhaust gases of heavy-duty diesel truck engines by using the organic Rankine cycle can reduce both fuel consumption and greenhouse gas emissions. The design of such systems is constrained by the space available for installation; thus, an optimization procedure is required. In this research work, a two-objective optimization, based on the maximization of power output and minimization of the total heat exchanger surface area, is implemented in the Engineering Equation Solver software package. Application of the developed procedure is illustrated in a case with an exhaust gas temperature of 394.2 °C and mass flow rate of 0.306 kg/s. Configurations both with and without a recuperator are analyzed, and four working fluids (water, ethanol, toluene, and hexamethyldisiloxane) are compared. Of these fluids, ethanol could be recommended as the best when considering the organic Rankine cycle power output and the total area/volume of heat exchangers. For a total surface area of 10 m2 in the case without the recuperator, the power output values for ethanol, water, and toluene are 17.6 kW, 17.2 kW, and 15.8 kW, respectively; with the recuperator, the power output is slightly higher, but the total area of heat exchangers is considerably larger. Again, the best working fluid is ethanol: for a total surface area of heat exchangers of 24 m2, the power output values for ethanol, toluene, and hexamethyldisiloxane are 18 kW, 17.1 kW, and 15.8 kW, respectively. The presented procedure is useful both for the conceptual design of a complete waste heat recovery unit and for the optimization of all heat exchangers. [ABSTRACT FROM AUTHOR]

Highlights • A novel solar powered trigeneration energy system is proposed. • The superiority of hydrocarbons and NH 3 -LiNO 3 as working fluid is debated. • The system performance is theoretically evaluated by energy and exergy methods. • High irreversibility rate occurs in the heliostat field, HRVG, and process heater. Abstract The present study focuses on energy and exergy analyses of the trigeneration system consisting of heliostat field, organic Rankine cycle with the heat exchanger, and ejector-absorption chiller which has the merits of refrigerating a thermal load of below than 0 °C with solar energy more efficiently along with the generation of process heat and electric power in an eco-friendly manner. A parametric study is carried out to investigate the effect of varying the influencing operating variables on trigeneration system output, and its energy and exergy efficiencies. It is found that the exergetic output of isobutane operated system increases from 2562 kW to 4314 kW while for propane operated system it is raised from 1203 kW to 2028 kW when the direct normal irradiations are increased from 600 to 1000 W/m2. Results of energy and exergy utilization show that for isobutane ORC fluid, out of 100% solar energy supplied to the system 65.42% can be produced as energetic output and rest 34.58% is lost via thermal exhaust to ambient. On the other hand, out of 100% solar exergy supplied only 13.98% is the produced exergy, 84. 89% is the exergy destroyed due to irreversibilities, and rest 1.13% is the exergy loss. [ABSTRACT FROM AUTHOR]

• A flexible and multi-functional experiment facility of organic Rankine cycle is constructed successfully. • Desired expander isentropic efficiency is achievable in the facility with verifications. • The improvement potential is quantified by using the advanced exergy analysis. • The system power output and thermal efficiency range at 2.42–3.55 kW and 5.2%–7.3%, respectively. In the present study, a novel and flexible experimental facility of an organic Rankine cycle system is constructed. Four extra heat exchangers than traditional test bench are equipped for the system performance testing with different evaporator and condenser or heat transfer examinations of the evaporator and condenser. The combination of an expansion valve and a cooler is designed to simulate the expander with desired type and expansion characteristic. Meanwhile, a scroll expander is installed in parallel. Preliminary investigations are motivated to explore the operating characteristics of the novel experimental facility under different conditions and to quantitatively discover the system improvement potentials for further optimizations. After the steady-state operation evaluation, the system is investigated by varying the heat source temperature and heat sink temperature as well as the working fluid pump stroke. The constant expander isentropic efficiency scenario is simulated through the combination of the expansion valve and cooler, and it is also validated by the installed expander. Results show that the power output of the system and electricity consumption of the working fluid pump are in the ranges of 2.42–3.55 kW and 0.44–0.49 kW, respectively, and the system thermal efficiency varies from 5.2% to 7.3%. Moreover, the system is then deeply explored by using exergy analyses to reveal the potential for performance improvement. The conventional exergy analysis tells that the evaporator has the largest exergy destruction. However, the advanced exergy analysis gives a more realistic improvement potential and suggests that the expansion process should be firstly improved. [ABSTRACT FROM AUTHOR]

• The waste heat recovery in an innovative waste-CHP-ORC plant is proposed. • Two alternative working fluids are considered to make the system environmentally friendly. • The combined configuration is designed and analyzed techno-economically. • The energy and exergy efficiencies increase up to 20% and 10%, respectively. • The payback period of the system is improved by about 10%. A smart hybrid power plant comprising a waste-fired CHP (combined heat and power) plant accompanied by a small-scale organic Rankine cycle was recently designed and analyzed thermodynamically. The objective of this hybridization is to maximize the share of electricity production of waste-CHP plants rather than a higher heat production rate in a cost-effective manner. In this work, utilization of the exergy of the hot flue gas of the waste-fired CHP unit in order to increase the potential of the organic Rankine cycle for maximizing the net power output of the hybrid cycle is proposed and techno-economically analyzed. In addition, the effect of using alternative environmentally-friendly organic working fluids on the performance of the system was investigated. The results of the study show that by the flue gas potential utilization of the same CHP unit, the size of the organic Rankine cycle may increase significantly, leading to a larger power output of the plant. As such, the net exergy and energy efficiency values of the combined plant in various operational conditions are improved compared to its primary configuration by, respectively, about 10% and 20%, when both of the main CHP cycle and the organic Rankine cycle are working at nominal load. In addition, this exergy utilization is beneficial economically as well, decreasing the payback period of the parallelization project by about 10% (from 7.4 years to 6.7 years). The alternative organic working fluid does not make a significant change in the technical and economic performance indices of the system. [ABSTRACT FROM AUTHOR]

• A novel operating mode is proposed for stable output of a solar power system. • Efficiency of novel operating mode exceeds that of unstable output operating mode. • The maximum system efficiency reaches 17.9% with recuperative ORC using toluene. Solar organic Rankine cycle (SORC) is a promising approach for solar energy utilization under low and moderate temperatures due to low investment and small-to-medium scale. The stable output of the SORC system under variable solar irradiation conditions is necessary to weaken the impact on the power grid and provide a base load. A novel operating mode was designed to obtain the stable output of 1 MWe for a SORC system operated under variable solar irradiation for 1 day. The parabolic trough collector was selected for solar heat reception, and a two-tank direct thermal storage unit was used for heat storage. Given the variations in solar irradiation, the mass flow rate of the heat transfer fluid (HTF) in the solar collectors was adjusted to guarantee a constant HTF inlet temperature for the ORC unit, and the mass flow rate of the HTF from the hot tank to the ORC unit was kept constant. Thus, the SORC system could operate under stable conditions. Four organic working fluids and two cycle types were subjected to thermodynamic analysis and parametric optimization. Results show that as the HTF inlet temperature increases, the optimal efficiency of system with non-recuperative cycle and toluene increases, whereas those of systems with non-recuperative cycles and cyclohexane, hexamethyldisiloxane, and pentane as working fluids first increase and then remain constant. The increment in the superheat degree increases the efficiency of the system with recuperation. By contrast, the system with non-recuperation demonstrates the maximum system efficiency in the absence of or at a low superheat degree. The maximum system efficiency reaches 17.9%. The system efficiency of this novel operating mode is 4.2% higher than that of an unstable output operating mode when operated for 1 day. [ABSTRACT FROM AUTHOR]

• Optimization and control of ORC for WHR from HD Diesel engines are investigated. • Powertrain electrification-oriented layouts for integration of ORC are proposed. • Pump and turbine of ORC unit are controlled to obtain maximum net power output. In the last years an increasing interest has grown about the organic Rankine cycle (ORC) for waste heat recovery from the engine exhausts, as a feasible way to improve the efficiency of internal combustion engines (ICE). However, the highly variable working conditions in which an engine usually works make the operation of the ORC unit very challenging. In the management of ORC units, optimization and control are considered as an essential step in order to attain good performance during the whole operation of the ICE on a driving cycle. In this paper a GT-Power model of a 12.6 l turbocharged Diesel engine is used as a typical heavy duty Diesel engine to retrieve the temperature and the mass flow rate of the exhaust gases during a heavy heavy-duty driving cycle. An optimization process is performed to maximize the power output of the ORC as a function of the revolution speeds of the pump and of the turbine. For powertrain electrification purposes, two different ORC layouts are proposed in this paper, both seeking to store the recovered energy into a battery pack. The first layout is optimized based on mean values of exhausts temperature and mass flow rate, while the second layout is designed to control independently the revolutions of the pump and of the turbine of the ORC unit toward optimal values for maximum net power output. Both the layouts allow to recover an interesting amount of energy, in spite of a straightforward control strategy. Nonetheless, results show that optimizing the net power of the ORC cycle by decoupling the turbine and the pump may not ensure the maximization of the recovered energy. In fact, the storable energy from the ORC unit is strongly affected by the conversion efficiencies related to the specific layout. [ABSTRACT FROM AUTHOR]

Highlights • A novel CCHP system integrated Organic Rankine Cycle is first proposed. • The Analytic Hierarchy Process is applied in selection of working fluids. • The effects of superheat degree and chilled water mass flow rate are discussed. • The condenser temperature ranges from 25 °C to 40 °C. Abstract The extensive use of organic Rankine cycle (ORC) in waste heat recovery motivates the employment of ORC technique to recover the waste heat in coal-fired plants. A novel combined cooling-heating and power (CCHP) system integrated Organic Rankine Cycle (CCHP-ORC) for recovering the waste heat of bottom slag in coal-fired plant is first proposed in this paper. A MATLAB procedure with REFPROP database is developed for the proposed system based on the mass, energy and exergy balances of each component. With the application of Analytic Hierarchy Process (AHP) method, R1234ze(E) and heptane/R601a are adopted as the optimal working fluids for the Sing Fluid CCHP-ORC and Dual Fluid CCHP-ORC systems, respectively. Parametric studies are conducted to investigate the effect of superheat degree of turbine inlet temperature, chilled water mass flow rate and condenser temperature on the coefficient of performance, thermal efficiency, heat exergy, cooling exergy, total exergy production and exergy production rate. The results show that the superheat degree of turbine inlet temperature benefits the enhancement of the exergy production rate. The enhancement of chilled water mass flow rate leads to an increase in coefficient of performance and refrigerating capacity while the cooling exergy, total exergy production and exergy production rate decrease. Except for exergy production rate in Dual Fluid CCHP-ORC system, the rise of condenser temperature leads to a decrease of performance parameters. As the condenser temperature rises from 25 °C to 40 °C, the thermal efficiency of Cycle2 declines 19.4% and 18.3% respectively in the Sing Fluid CCHP-ORC system and Dual Fluid CCHP-ORC system. [ABSTRACT FROM AUTHOR]

Highlights • A novel coal gasification-based multigeneration system is developed. • A hydrogen production and liquefaction unit are integrated. • Energy and exergy efficiencies of proposed plant are descripted and calculated. • The energetic and exergetic performance results of overall system are investigated. Abstract The primary subject of this paper to investigate the coal gasification-based integrated power process for multigeneration aim, such as electricity, heating, cooling, fresh and hot water, hydrogen production and liquefaction. This suggested work consists of the gasification process, Rankine cycle with two turbines, organic Rankine cycle, single effect absorption cooling cycle, membrane distillation process, PEM electrolyzer and hydrogen liquefaction cycle. The thermodynamic assessment is utilized to examine the investigated system efficiency, and also the effects of some process indicators on the energetic and exergetic performance of integrated plant and its sub-systems are investigated. The energy and exergy efficiencies of the proposed plant are calculated as 58.47% and 55.72%. In addition, the overall irreversibility of system is found as 65126 kW. The outcomes of thermodynamic evaluation show that the varying temperature of coal gasifier, combustor and exhaust gas affect the whole system performance. [ABSTRACT FROM AUTHOR]

Highlights • A 34 kW gas engine considered as prime-mover of various thermodynamic cycles. • In all configuration, toluene is the better fluid for organic Rankine cycle. • This cycle with internal heat exchanger recovers 4.7 kW power from exhaust gas. • Trilateral flash cycle recovers almost 1.98 kW power from engine coolant. • Rankine with open feed heater is better one for combination with Kalina cycle. Abstract In the present work a 34.3 kW stationary gas engine considered as prime-mover of bottoming thermodynamic cycles. The waste heat recovery cycles of engine exhaust gas consist of several configurations of organic Rankine cycle and combination of Rankine/Kalina cycles, also the engine jacket water heat is recovered by trilateral flash cycle. The performance of bottoming cycles was investigated from thermodynamic and thermo-economic points of view. For the organic Rankine cycle, three fluids including Benzene, Toluene and Cyclohexane have been compared. Also, considering that the trilateral flash cycle is a suitable cycle for heat recovery from a low temperature heat source due to its better matching between the temperature profiles of cycle working fluid and heat source fluid, this cycle is considered as bottoming waste heat recovery cycle for engine jacket water. In order to compare different working fluids and cycle configurations, three objective functions including energy efficiency, exergy efficiency and specific investment cost for the 18 studied cases are compared. The results reveal that, energy, exergy efficiency and specific investment cost of all configurations with toluene as working fluid of organic Rankine cycle is the highest and least compared to the other working fluids, respectively. But for configuration Rankine with Open Feed Heater-Kalina-Trilateral Flash Cycle, benzene fluid is better in terms of specific investment cost, however the energy and exergy efficiency of this cycle is also maximal with toluene fluid. Also, the results depict that configurations Rankine with Internal Heat exchanger – Trilateral Flash Cycle and Rankine with Open Feed Heater_Kalina_Trilateral Flash Cycle thermodynamically, and configurations Rankine with Internal Heat exchanger – Trilateral Flash Cycle and Rankine with Open Feed Heater – Trilateral Flash Cycle exergo-economically show the better performance. In this regard, employing configurations Rankine with Internal Heat exchanger – Trilateral Flash Cycle, Rankine with Open Feed Heater-Kalina – Trilateral Flash Cycle and Rankine with Open Feed Heater – Trilateral Flash Cycle in base mode leads to 6.85 kW, 6.48 kW and 6.54 kW increment in net power produced imposing 3318 $/kW, 4090 $/kW and 3377 $/kW specific investment cost, respectively. [ABSTRACT FROM AUTHOR]

Highlights • A non-azeotropic mixture combines with ORC for the waste heat recovery. • Working conditions of ORC and TSORC using the mixture are optimized. • The ORC and TSORC with mixture are compared. Abstract Nowadays, gas turbines (GTs) are increasingly used in China, with a relatively low performance. Organic Rankine cycle (ORC) is promising to recover the flue gas heat recovery from GT. To efficiently enhance the heat recovery, two-stage series evaporation is combined with non-isothermal phase change of non-azeotropic mixtures. Thus, two-stage series organic Rankine cycle (TSORC) with six non-azeotropic mixtures, composed of R245fa and hydrocarbons, as the working fluids are investigated. The cycle performances of TSORC with non-azeotropic mixtures are compared with those of the ORC with pure working fluid. Moreover, a case study was conducted to illustrate the performance enhancement by TSORC with the non-azeotropic mixture for fuel gas waste heat from C200HP. The results show that the net power output, thermal and exergy efficiencies of the TSORC are superior to those of the ORC at the same mass fraction, especially for the net power output. Comparing with the stand-alone gas turbine of C200HP, the TSORC with cyclohexane/R245fa[0.8/0.2] increases the efficiency of C200HP system by 35.48%, and the power generation efficiency of the C200HP-TSORC system achieves 44.71%. The TSORC with non-azeotropic mixtures as the working fluids is advisable and can be popularized in engineering applications. [ABSTRACT FROM AUTHOR]

Highlights • Comparison of an ORC system with different turbine efficiency models was conducted. • Both thermodynamic and economic performance was considered. • The reasons leading to the deviation in the optimization results was analyzed. • Sensitivity analysis of the CTORC system and the VTORC system was conducted. Abstract The radial-inflow turbine is a key component of the organic Rankine cycle (ORC) system, and its efficiency is related to working fluid properties and working conditions. In this paper, multi-objective algorithm was employed to conduct a comparative analysis of an ORC system with different turbine efficiency models (constant and variable). The system thermal efficiency and multi-objective optimization results between the constant turbine efficiency ORC system (CTORC) and the variable turbine efficiency ORC system (VTORC) were compared, and the reasons for the difference between the CTORC and VTORC system were analyzed. Sensitivity analysis was performed to compare the difference between the CTORC system and the VTORC system at different waste flue gas inlet temperature. The results show that the system thermal efficiency of both the CTORC and the VTORC increases with the increasing evaporation temperature and decreases with the increasing condensation temperature, while the variation rate of system thermal efficiency is different between CTORC system and VTORC system. The predicted turbine efficiency is significantly different for different working fluids and different working conditions. Considering the system comprehensive performance, R236ea is the optimal working fluid for the CTORC system, while R365mfc is for the VTORC system. For different working fluids, the error caused by using constant turbine efficiency model is different. With the increasing waste flue gas inlet temperature, the error caused by using constant turbine efficiency increases for R236ea, while the error caused by using constant turbine efficiency increases first and then decreases for R365mfc. [ABSTRACT FROM AUTHOR]

Highlights • A novel non-imaging concentrator was adapted to a regenerative ORC. • The effect of organic working fluids on collector and cycle performances were evaluated. • The best performance was seen in the case of R-141b for small scale applications. • For the case of R-141b, collector shows better performance. • The best improvement was obtained in the case of water for large scale applications. Abstract A non-imaging concentrator compound by involute and parabolic concentrator was considered in a regenerative organic Rankine cycle (ORC). The concentrator was covered by vacuumed glass tube to reduce heat loss from the absorber, and to extend the effective life-cycle of optical components. Using the non-imaging concentrator can eliminate the necessity of sun tracking system due to its large acceptance angle. A simulation was carried out for low temperature solar thermal electric generation for various working fluids including dry, isentropic and wet fluids. The results showed the best efficiency of concentrator was observed for the case of R-141b and followed by methanol, R-113, water, benzene and cyclohexane, respectively. The best overall system efficiency was seen in the case of R-141b to be 16.7%. The evaporator pressure was changed as a calculation parameter. The best improvement was obtained for water and R-141b to be 8.8% and 8.3%, respectively. R-141b has a preferable performance because of its low boiling point and can be appropriate for small scales. The increase in evaporator pressure persuades the performance improvement for the case of methanol, water and benzene. It proves that these working fluids can be used for larger scale applications with a better thermal performance. [ABSTRACT FROM AUTHOR]