Analysis of Different Organic Rankine and Kalina Cycles for Waste Heat Recovery in the Iron and Steel Industry.

Parametric optimization of regenerative organic Rankine cycle (ORC) for low grade waste heat recovery using genetic algorithm

Process integration of organic Rankine cycle (ORC) and heat pump for low temperature waste heat recovery

Globally there are several viable sources of renewable, low-temperature heat (below 130°C) particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and promising system to generate electrical power from renewable sources based on its beneficial use of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference for/an inclination towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled by better matches of the temperature profiles of the WF and the heat source/sink. This paper demonstrates both the technical feasibility and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines the thermodynamic performance of ORC systems using zeotropic WF mixtures to generate electricity driven by low-temperature solar heat source for building applications. A thermodynamic model is developed with an ORC system both with and excluding a regenerator. Five zeotropic mixtures with varying compositions of R245fa/propane, R245fa/hexane, R245fa/heptane, pentane/hexane and isopentane/hexane are evaluated and compared to identify the best combinations of WF mixtures that can yield high efficiency in their system cycles. The study also investigates the effects of the volumetric flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane is selected for parametric study to examine the effects of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results showed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a significant increase in cycle efficiency can be achieved with a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also showed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar organic Rankine cycles.

Globally there are several viable sources of renewable, low-temperature heat (below 130 °C), particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and suitable system to generate electrical power from renewable sources based on its beneficial usage of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled through the greater matching of the temperature profiles of the WF and the heat source/sink. This paper demonstrates the thermodynamic, economic and sustainability feasibility, and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines first the thermodynamic performance of ORC systems using zeotropic mixtures to generate electricity powered by a low-temperature solar heat source for building applications. A thermodynamic model is developed with a solar-driven ORC system both with and excluding a regenerator. Twelve zeotropic mixtures with varying compositions are evaluated and compared to identify the best combinations of mixtures that can yield high performance and high efficiency in their system cycles. The study also examines the effects of the volume flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane and butane/propane are selected for parametric study to investigate the influence of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results disclosed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a substantial enhancement in cycle efficiency can be obtained by a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also revealed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar ORCs. Moreover, a detailed economic with a sensitivity analysis of the solar ORC system was performed to evaluate the cost of the electricity and other economic criteria. The outcome of this investigation should be useful in the thermo-economic feasibility assessments of solar-driven ORC systems using working fluid mixtures to find the optimum operating range for maximum performance and minimum cost.

An examination of super dry working fluids used in regenerative organic Rankine cycles

This review examines Organic Rankine Cycle (ORC) technology, which generates electricity using organic fluids at low temperature ranges. To enhance the efficiency of basic ORC systems, they are often adapted into Regenerative Organic Rankine Cycle (R-ORC) systems. The review highlights the dimensions of economic, energy, and exergy efficiency, which are critical for practical application. Factors like the choice of working fluid, heat source temperature, and heat exchanger efficiency significantly affect economic feasibility; suboptimal choices can reduce returns and hinder project viability. Strategic decisions can improve economic outcomes and make ORC technology more appealing, as improved efficiency often leads to better economic performance through increased energy output and reduced operational costs. ORC and R-ORC systems promote sustainable energy production by enhancing energy efficiency in various applications, including geothermal power plants, industrial waste heat recovery, biomass energy production, and solar power plants. By enabling electricity generation even at low temperatures, these systems efficiently utilize existing energy sources, reduce dependence on fossil fuels, and minimize environmental impacts, thus providing both economic and ecological benefits. Additionally, when the studies conducted are examined, R-ORC exhibits higher performance than basic ORC. R-ORC is significantly superior to ORC in terms of both energy and exergy efficiency. Specifically, in terms of energy efficiency, R-ORC has been found to be 1.83 %–25.5 % more efficient. Regarding exergy efficiency, R-ORC demonstrates approximately 7.69 % better performance. Furthermore, due to these increases in efficiency, it has been determined that R-ORC also provides a more positive economic contribution compared to ORC. Thus, comparisons between ORC and R-ORC systems play a significant role in sustainable energy production and offer valuable guidance for future research. The limitations of ORC and R-ORC systems include limited efficiency due to low temperature differentials, the environmental impact of the organic fluids used, and high costs.

The performance of renewable energy systems can be significantly improved if power is produced from low-temperature heat sources. The organic Rankine cycle (ORC) is suitable for producing power from low-temperature heat sources. ORC finds applications alongside solar power, geothermal power, waste heat and biomass. ORC-enabled systems can contribute significantly to raising the effectiveness of renewable power sources. Solar power, for example, can deliver affordable electricity to remote locations and small industries. By employing ORC, power generation is possible at lower temperatures on cloudy days. Its main difference from the steam Rankine cycle is its working fluid. The ORC makes use of an organic, high molecular mass fluid as the working fluid. Compared to steam Rankine cycles, ORC works at a lower temperature (<250°C) and pressure. The only working fluid in the steam Rankine cycle is water, but the ORC can operate on hundreds of different working fluids. The design and performance of ORC systems are entirely dependent upon the suitable working fluid and, hence identification of the working fluid for ORCs is of utmost importance for diverse applications. Properties of working fluid have a considerable impact on the efficiency of the system. The main objective of this study is to identify the most suitable organic fluids having characteristics necessary for use in solar ORCs. In addition, a detailed review of the various types of heat transfer fluids now available in the market that are often used in ORC systems was conducted. This research assists in selecting the most appropriate organic fluids for various solar ORC applications in terms of operating circumstances.

Design optimization and analysis of a multi-temperature partition and multi-configuration integrated organic Rankine cycle for low temperature heat recovery

The last decade (2013–2023) was the most prolific period of organic Rankine cycle (ORC) research in history in terms of both publications and citations. This article provides a detailed review of the broad and voluminous collection of recent internal combustion engine (ICE) waste heat recovery (WHR) studies, serving as a necessary follow-on to the author’s 2013 review. Research efforts have targeted diverse applications (e.g., vehicular, stationary, and building-based), and it spans the full gamut of engine sizes and fuels. Furthermore, cycle configurations extend far beyond basic ORC and regenerative ORC, particularly with supercritical, trilateral, and multi-loop ORCs. Significant attention has been garnered by fourth-generation refrigerants like HFOs (hydrofluoroolefins), HFEs (hydrofluoroethers), natural refrigerants, and zeotropic mixtures, as research has migrated away from the popular HFC-245fa (hydrofluorocarbon). Performance-wise, the period was marked by a growing recognition of the diminished performance of physical systems under dynamic source conditions, especially compared to steady-state simulations. Through advancements in system control, especially using improved model predictive controllers, dynamics-based losses have been significantly reduced. Regarding practically minded investigations, research efforts have ameliorated working fluid flammability risks, limited thermal degradation, and pursued cost savings. State-of-the-art system designs and operational targets have emerged through increasingly sophisticated optimization efforts, with some studies leveraging “big data” and artificial intelligence. Major programs like SuperTruck II have further established the ongoing challenges of simultaneously meeting cost, size, and performance goals; however, off-the-shelf organic Rankine cycle systems are available today for engine waste heat recovery, signaling initial market penetration. Continuing forward, next-generation engines can be designed specifically as topping cycles for an organic Rankine (bottoming) cycle, with both power sources integrated into advanced hybrid drivetrains.

As the increase of the energy consumption and the deterioration of environment, a carbon tax will be imposed in China to reduce carbon emissions strictly and the industrial waste heat recovery has been getting more attention. The Organic Rankine Cycle (ORC) system has been proven to be a promising solution for the utilization of the low-grade heat sources. There are five waste heat sources from a 1.2 million ton reforming and extraction unit in Shijiazhuang Refining &amp; Chemical Company of China. The temperatures of the waste heat sources are 98∼80°C, 104∼80°C, 147∼80°C, 205∼80°C and 205∼80°C, and the heat loads are 6.5MW, 11.5MW, 8.6MW, 3.8MW and 2.2MW, respectively. This paper studies the thermal design and performance optimization of a comprehensive utilization system for these waste heat sources, using ORC technology. The selection of suitable organic fluid is studied and the working parameters are designed and optimized with the application of the first law and the second law of thermodynamics. When the ORC systems are designed separately for the recovery of five waste heat sources, and the total power output is 3338.89kW with different organic working fluids. However this kind of designs leads to a very complex recovery system which needs large investment and space occupation. To reduce the overall system complexity, a single ORC system is proposed to recover all five heat sources, and the total amount of output power will only be 2813.02kW, due to the large exergy loss. With the above results shown, and for the purpose of simple system with large power output, this paper further studies the dual ORC systems heat recovery plan, with R245fa as the top cycle working fluid and R141b as the bottom cycle working fluid. The total amount of power output to 3353.27kW. The dual systems with single working fluid heat recovery plan is also studied, and with R141b as the working fluid for both the top cycle and the bottom cycle, the total amount of power output is 3325.03kW, and the heat recovery system is simple and compact, with good economical benefit.

Automated configuration of organic Rankine cycle system based on process simulations

In this study, the optimal design and operation of an Organic Rankine Cycle (ORC) system driven by solar energy is investigated. A two-tank sensible thermal energy storage system is configured to overcome the intermittency of solar energy. A circulating fluid, also termed as heat transfer fluid (HTF) that connects the solar collector and the ORC system plays a critical role in this system. The mass flowrate of the HTF determines both the temperature of the HTF and the amount of heat absorbed from the solar collector. A simulation-based optimization model is developed in this work. Process simulation of the ORC is performed in Aspen HYSYS, and the mathematical models of the energy storage system and the parabolic trough collector are developed in Matlab. The optimal design of the system including the hot tank temperature, cold tank temperature, mass flowrate of the HTF, and operating conditions of the ORC are determined simultaneously based on the simulation-based optimization framework. The control strategy of the solar collector can be determined as well. The system efficiency of the solar energy driven ORC system is maximized with the proposed optimal operation strategy. With the simulation-based optimization framework, the system efficiency of the recuperative ORC power plant with toluene as the working fluid is increased from 17.9% to 24.8% compared with a previous study in the literature. The recuperative ORC performs much better than the basic ORC. Toluene performs best among all the investigated working fluids ignoring the problem with vacuum condensation. The cycle type (subcritical vs. supercritical) exerts great influence on the system performance. The supercritical ORC can improve the thermal efficiency by 11.3% and the overall system efficiency by 10.8% compared with the subcritical ORC with n-pentane as the working fluid.

Selection of organic Rankine cycle working fluids in the low-temperature waste heat utilization

The intercooling of multi-stage compressors contributes to reducing the power consumption of compressors and the waste heat is generally taken away by cooling water, which is a great waste of energy. This paper employs an organic Rankine cycle (ORC) or a Kalina cycle to recover the waste heat of compressor intercooling. The mathematical models of ORC and Kalina cycle are established by MATLAB software to simulate the ORC system and the Kalina cycle system under steady-state conditions. A parametric analysis is conducted to evaluate the effects of several key thermodynamic parameters on the system performance. In addition, a parametric optimization is carried out to find the optimum performance of waste heat recovery system from thermodynamic aspect. The results showed that, for the ORC system, there is an optimum value of turbine inlet pressure with the state of working fluid being saturated vapor that yields the minimum net power consumption of the system; whereas for the Kalina cycle system, in some ranges of accessible operation conditions, a higher turbine inlet pressure, a lower turbine inlet temperature and a lower ammonia mass fraction of basic solution could obtain a less net power consumption of the system. The optimization results indicated that the Kalina cycle system shows a better performance than the ORC system.

Organic Rankine Cycle (ORC) is one of the alternative technologies for generating electricity from low to medium level heat sources. ORC operates at low temperatures and pressures using two types of organic working fluids. The organic working fluids as the refrigerants were chosen in the ORC system instead of water, which is suitable for high pressure and temperature applications. Since the performance and configuration of the ORC system rely on its working fluids, the selection of the working fluid for the ORC system becomes crucial. The system utilizes low-temperature heat sources as a supply of heat energy that flows through the evaporator and is then received by the working fluid to operate the cycle. In this study, two dry type working fluids, namely butane (R600) and isobutane (R600a), were used to thermally design an ORC to recover geothermal waste heat. The working fluids were designed using mathematical calculations based on thermodynamic laws. The results revealed that a slightly higher thermal efficiency value was achieved when using R600 as the working fluid, which was 12.8% compared to R600a.