Steam Cycle Research Articles

Machine learning-based optimization and 4E analysis of renewable-based polygeneration system by integration of GT-SRC-ORC-SOFC-PEME-MED-RO using multi-objective grey wolf optimization algorithm and neural networks

This study introduces a new solar-methane-driven setup that recovers waste heat from flue gases to produce electricity, hydrogen, oxygen, fresh water (FW), and domestic hot water (DHW) while reducing the environmental impact of gas turbines. This integration includes the Brayton cycle and solid oxide fuel cell as motive cycles, the steam and organic Rankine cycle, a parabolic trough solar collector (PTC), a proton exchange membrane electrolyzer, multi-effect distillation, and reverse osmosis. Using Engineering Equation Solver software, analyses in energy, exergy, exergoeconomic, and exergoenvironment (4E) are conducted to identify critical system evaluation parameters in thermodynamics, economics, and the environment. Additionally, the proposed system is optimized using an artificial neural network and the multi-objective grey wolf optimizer algorithm, utilizing decision variables identified through sensitivity analysis to enhance system performance. The results of six-objective optimization show energy and exergy efficiencies at 49.48 % and 47.21 %, with a net power production of 133 MW and a total cost rate of $7903/h. Among all the components, the combustion chamber and PTC have the maximum exergy destruction, with values of 58.87 MW and 17.29 MW, respectively. Also, hydrogen, FW, and DHW production rates are 201.6 kg/h, 43.88 kg/s, and 40.98 kg/s, respectively. Moreover, the costs of hydrogen, FW, and DHW are $953.64/h, $57.35/h, and $82.48/h, respectively. Finally, Bloemfontein, Las Vegas, and Tunis are the most favorable regions economically, with a low levelized cost of electricity of $0.05931, $0.06006, and $0.05932 per kWh, along with payback periods of 0.6144, 0.5524, and 1.069 years, respectively.

Combining Exergy and Pinch Analysis for the Operating Mode Optimization of a Steam Turbine Cogeneration Plant in Wonji-Shoa, Ethiopia.

In this research, the simulation of an existing 31.5 MW steam power plant, providing both electricity for the national grid and hot utility for the related sugar factory, was performed by means of ProSimPlus® v. 3.7.6. The purpose of this study is to analyze the steam turbine operating parameters by means of the exergy concept with a pinch-based technique in order to assess the overall energy performance and losses that occur in the power plant. The combined pinch and exergy analysis (CPEA) initially focuses on the depiction of the hot and cold composite curves (HCCCs) of the steam cycle to evaluate the energy and exergy requirements. Based on the minimal approach temperature difference (∆Tlm) required for effective heat transfer, the exergy loss that raises the heat demand (heat duty) for power generation can be quantitatively assessed. The exergy composite curves focus on the potential for fuel saving throughout the cycle with respect to three possible operating modes and evaluates opportunities for heat pumping in the process. Well-established tools, such as balanced exergy composite curves, are used to visualize exergy losses in each process unit and utility heat exchangers. The outcome of the combined exergy-pinch analysis reveals that energy savings of up to 83.44 MW may be realized by lowering exergy destruction in the cogeneration plant according to the operating scenario.

Repowering strategies: Analysis of gas turbine integration with steam cycle for enhanced power plant performance

Repowering strategies: Analysis of gas turbine integration with steam cycle for enhanced power plant performance

Energy efficiency as an accelerator to environmental and operational performance

As oil and gas operators continue to enhance and start implementing their plans to meet their regulators’ and customers’ net-zero related demands, the industry should not overlook those low-hanging fruit that will bear results in the short term and, if done well, also contribute to long-term objectives. An effective approach to energy management will contribute to environmental, operational and financial outcomes, by addressing resource scarcity and price volatility, delivering on licence-to-operate considerations, complying with regulations, and delivering a competitive advantage through greater efficiency and enhanced reputation. Key considerations are as follows. Data quality: fuel, power, steam, condensate balances will highlight data gaps and inconsistencies. Energy usage: inefficiencies in operations such as boilers, turbines, as well as systemic issues, such as cycle efficiency and steam and condensate losses, can be identified. Emissions monitoring and reporting: clear and consistent data about fuel and power consumption directly feeds into greenhouse gas corporate reporting schemes. Quality assurance of monitoring and reporting processes: review and challenge dashboards and reports for completeness, accuracy and clarity. Management operating system: redesign management processes to improve workflows and optimise operations. Loss accounting: Production and Energy Loss Accounting (PELA) improves staff collaboration and effectively tackles hidden losses. In this paper, dss+ will share how, using a mix of operational efficiencies and capex, an integrated oil and gas company active in 30 countries identified potential to reduce its emissions by 38 m tonnes of CO2 leading to over US$6 m in savings per annum over 4 years for just four of its assets.

Development a policy for the production of Bitcoins with renewable energy sources

Bitcoin, the first decentralized digital currency introduced by an anonymous person or group since 2008, has attracted worldwide attention. A significant number of economists have introduced Bitcoin as a new phenomenon in the 21st century that could reduce global inflation. Given the tens of thousands of digital currencies that have emerged since the advent of Bitcoin and its price growth trend over more than a decade, which are signs of the growth of this business. In addition to being money, Bitcoin has always been considered a tool for investing and storing value, which is why it is called digital gold. One of the most important problems in the production or extraction of Bitcoins is the high-power consumption by miners. If the energy sources of electricity generation are supplied by non-renewable energy sources, in addition to emitting air pollutant gases, it will increase greenhouse gases and consequently contribute to climate change. In this research, based on the idea of the authors, which is that the economic support of Bitcoin is energy, a strategy for producing Bitcoin from renewable energy sources is considered. First, the amount of electrical energy consumption by Bitcoin production is calculated based on statistical data, and then based on the price of electricity in different countries of the world and its global average, the base price of Bitcoin is calculated. In the following, four scenarios are proposed for the production of Bitcoin by electricity supplied from non-renewable energy sources. These scenarios include coal-fired steam power plants, natural gas-fired power plants, natural gas/oil gas-fired power plants, and dual-cycle (steam and gas cycles) natural gas-fired power plants. Based on the amount of electricity required to produce one Bitcoin, the amount of pollutants emitted to produce Bitcoin and its social costs are calculated. These costs should be added to the base cost of Bitcoin production if non-renewable energy sources are used to produce Bitcoin. Then, renewable energy sources for Bitcoin production based on the price of electricity generated by renewable energy sources are examined. Based on the analyses, how to choose the best renewable energy source to produce Bitcoin is presented as a scenario. This article briefly answers two key questions: 1. At what price of Bitcoin is it cost-effective for governments to produce it? 2. What is the best renewable energy source to produce it? These two questions can be useful in creating a roadmap and strategy for economists and governments.

Performance assessment and comparison of a catalytic steam reforming enhanced closed-brayton-cycle power generation system for hypersonic vehicles

Hypersonic vehicles as next-generation aircraft have broad applications, but existing technologies of onboard power generation are hardly applicable due to the change of engines. In this research, a catalytic steam reforming enhanced closed-Brayton-cycle power generation system based on is developed. This system combines the closed Brayton cycle (CBC) and catalytic steam reformed fuel vapor turbine (CSRFVT) to supply electric power. The zero-dimensional models of CBC and the CSRFVT are established to evaluate system performance. Results indicate the products with a water content of 30% have the strongest working ability, which can reach 330 kJ/kg. Moreover, the thermal efficiency and electric power of the parallel arrangement are higher than that of the series arrangement. Besides, the lower pressure of water is beneficial to the electric power. However, the difference in electric power between various pressures is less than 1 kW. In addition, under the same heat absorption, the total electric power of the system based on fuel and water is higher, and the former's outlet temperature of cooling channels is lower. The maximum total electric power of the novel system is about 120 kW. This research provides an innovative technical solution for the power generation of hypersonic vehicles.

Hybrid Technology Incorporated Into Colombian Heavy Oil Field Development Plan

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 213199, “Incorporating Hybrid Technology of CSS and Foam in Heavy Oil Field Development Plans: Practical Experiences and Lessons Learned,” by Romel A. Perez, SPE, Hector A. Rodriguez, and Jorge E. Romero, Ecopetrol, et al. The paper has not been peer reviewed. _ A research and development project was conducted to study the use of preformed foams to improve cyclic steam stimulation (CSS). The field results showed benefits in incremental oil production, improvements in energy efficiency, and reduction in carbon intensity. Based on those outcomes, and with the goal of extending the production life of mature assets, the hybrid technology of CSS plus foam improvements was incorporated into the heavy oil field development plans of the Middle Magdalena Valley (MMV) basin in Colombia. Pilot Results: 2019–2022 CSS maturity is one of the major challenges in the MMV. Many wells report more than 10 steam cycles, decreasing oil productivity, and a trend of shorter steam cycles (less than 10 months). Most injected steam drained the higher-flow-capacity intervals based on the permeability contrast within the pay zone and openhole completions. Therefore, the bullhead injection of preformed foam improvements implemented before the steam cycle was proposed as part of a conformance strategy. The main goal of the pilot test was to demonstrate the efficiency of the hybrid technology, extend the production life of steam cycles, increase oil recovery, and improve energy efficiency and carbon footprint. The CSS pilot was implemented in six wells of the Teca-Cocorna field (Fig. 1). Performance was evaluated in terms of incremental oil, carbon intensity, and energy efficiency. A similar approach was proposed to evaluate energy efficiency and greenhouse emissions of CSS and hybrid CSS based on numerical simulations and the performance of two wells in Block D-80 in China. By the end of this stage, an incremental oil of approximately 32,000 STB was confirmed. Only one well recorded almost 50% of the total incremental oil of the pilot, and one well was only evaluated for 6 months because of a mechanical failure. Incremental oil recoveries and geochemical analysis confirmed the potential of this hybrid steam method to target unswept zones in idle or marginal wells operating since the 1980s. Additionally, the Teca-Cocorna pilot reduced carbon intensity and improved energy efficiency by 56% and 54%, respectively. The reduction of the carbon intensity from 83 (baseline) to 46 kg CO2/STB represents an important achievement in terms of environmental benefits and highlights the fact that the volume of natural gas used to generate steam was optimized by using less gas by extending steam cycles to a minimum of 9 months. In other words, the CCS/foam cycle can produce as much oil as two CCS cycles in the pilot wells.

FEEDWATER TREATMENT AT THERMAL POWER PLANT

As a rule, water is used as the working fluid of thermal power equipment, which undergoes a series of phase transformations in steam cycles. Water is useful for its properties and as a result gained such wide popularity. It is important to consider that water is the most accessible, widespread and environmentally friendly substance on Earth. Water has low viscosity, high density, good heat transfer coefficient, low cost, and water does not require disposal. In addition to these properties, water also has a high heat capacity, which makes it an efficient heat transfer medium. This means that it is able to absorb and transfer large amounts of heat without a significant change in temperature. This is especially important in heat transfer systems where heat transfer efficiency plays a key role. It worth noting that water is responsive to temperature regulating. Natural water also has disadvantages, such as the possibility of corrosion processes with the formation of metal oxides (rust) and thus destruction of equipment surfaces, limescale formation on heating surfaces when heated to temperatures above 80 degrees Celsius. Therefore, it is necessary to carry out appropriate physical and chemical treatment of water to ensure all the requirements that applied to the water coolant. Certain quality indicators, processing methods and schemes, as well as equipment protection methods have been established for water. The article presents data on determining the dependence of a number of indicators of water quality taken from the water of the Irtysh River for use at Semey CHPP-1.

Sustainable approach to integrate a conventional power plant and renewable energies, coupled with the Goswami cycle and Maisotsenko heat exchanger

AbstractThis paper presents a pioneering investigation into an integrated power generation cycle that combines gas turbines, steam turbines, Goswami cycles, biomass fuel, solar energy sources, and advanced Maisotsenko heat exchangers. Biomass gasification has been applied to partially fuel the gas turbine, while the M‐Cycle serves as the gas turbine inlet air cooling system. Solar parabolic collectors are utilized to elevate the compressed air temperature for combustion, and the Goswami cycle generates both power and cooling through waste heat recovery. This research addresses a critical gap by undertaking a holistic examination of the integrated power generation cycle, modelling the overall system performance by considering interactions and synergies between various components. The base model has been implemented, and the impacts of influential parameters on system efficiency, such as ambient temperature, seasonal variation, and steam‐to‐biomass ratio, have been taken into consideration. Remarkably, the incorporation of the M‐Cycle, solar parabolic systems, steam cycles, and the Goswami cycle into the base gas cycle results in substantial energy efficiency enhancements of 1.59%, 1.96%, 16.87%, and 6.06%, respectively, highlighting the transformative potential of this integrated approach for sustainable and efficient power generation.

Supercritical CO2 recompression Brayton power cycle for hybrid concentrating solar and biomass power plant

The supercritical CO2 Brayton cycle has great potential in various renewable energy systems. The supercritical CO2 recompression Brayton power cycle for hybrid concentrating solar and biomass power plant is proposed and analyzed in this paper. The supercritical CO2 is heated by both the molten salt and flue gas from the biomass boiler. The inlet temperature of the turbine in the supercritical CO2 recompression Brayton power cycle for hybrid power plant rises to 620 °C. The waste heat from the system is recovered by the steam turbine to improve energy utilization efficiency. The efficiency of the supercritical CO2 recompression Brayton power cycle increases from 0.382 to 0.41. The efficiency of the steam cycle is 0.46, and the efficiency of the combined cycle is 0.427.

Design Optimization of a Horizontal Particle Receiver for a Modular Beam Down Receiver CSP

CSP research is focused on increasing the economic competitiveness of this technology as compared to conventional and emerging energy generators. Higher temperature operation conditions represent a pathway toward cost reductions since they enable a relatively smaller solar field area (typically ~40-50% of the plant cost) for the same electrical output. For example, supercritical CO2 power cycles with solid particles as the HTF could enable >600°C operations and a ~50% power bloc cycle efficiency (considerably higher than steam cycles, <40%). Additionally, small modular systems could increase competitiveness through reduced financial risk, increased system flexibility, and the value of additional services that a modular CSP could offer to the electricity grid (frequency control, peaking supply, etc.). This study investigates the Beam Down Receiver (BDR) configuration as a design that could be well-suited to meet these goals while also overcoming some of issues with particle receivers, such as particle attrition, advective losses, and operation control. In particular, this work introduces a novel horizontal particle receiver (HPR) and analyzes the main design parameters, including tower height, BDR size, radiation flux on the receiver, and receiver nominal power. The analysis shows that tower heights between 35m to 60m are ideal for high temperature receiver capacities of 8-15 MWth, and that this configuration can achieve a minimized LCOH of ~24 USD/MWth. These results suggest that BDRs combined with particle mediums could represent a viable high temperature, high efficiency CSP alternative.

Simulation and Control of Solar Thermal Power Plants

In this paper, first the overall modeling approach for an optimized control of a hot-gas cycle for solar thermal power plants in the Modelica language is pointed out. The emphasis of the modeling work lies on the development of dynamic component models to be used in control systems. Depending on the control task, the discretization of the models has to be adapted. Main components of the hot-gas cycle are the solar thermal receiver and the storage system. The steam cycle is preliminarily only included as heat sink. Second, for control purposes a linear model-based controller (MPC) was implemented in Modelica based on an external state-of-the-art QP solver [2] linked to the Modelica model. The performance of the MPC is compared with a basic automation scheme based on classical PID controllers.

A Review of the Research Progress and Application of Key Components in the Hydrogen Fuel Cell System

The hydrogen cycle system, one of the main systems used for hydrogen fuel cells, has many advantages. It can improve the efficiency, the water capacity, and the management of thermal fuel cells. It can also enhance the safety of the system. Therefore, it is widely used in hydrogen fuel cell vehicles. We introduce the structure and principles of hydrogen cycle pumps, ejectors, and steam separators and analyze and summarize the advantages of the components, as well as reviewing the latest research progress and industrialization status of hydrogen cycle pumps and ejectors. The technical challenges in hydrogen circulation systems and the development direction of key technologies in the future are discussed. This paper aims to provide a reference for research concerning hydrogen energy storage application technology in hydrogen fuel cell systems.

Comprehensive analysis and optimization of a low-carbon multi-generation system driven by municipal solid waste and solar thermal energy integrated with a microbial fuel cell

Abstract In this article, a novel multi-generation plant is addressed and assessed from the energy, exergy, exergoenvironmental and exergoeconomic points of view. The multi-generation plant is composed of two main units: one unit for energy production and another unit for carbon capture and methanol synthesis. Biomass fuel, solar energy and seawater are the main nutrients in the plant. Steam, Brayton, organic Rankine and Kalina cycles have been employed to generate electricity. A linear Fresnel collector-driven solar farm is considered as an auxiliary heat source. In addition, an integrated desalination unit based on a multi-effect desalination unit, a microbial fuel cell and a reverse osmosis unit has been installed in the multi-generation plant. The proposed structure for the offered multi-generation plant is designed under a new configuration and layout that had not been reported in the publications. From the outcomes, the multi-generation plant can produce 69.6 MW of net electricity, 0.53 kg/s of methanol, 0.81 kg/s of oxygen gas, 73.8 kg/s of fresh water and ~0.015 kg/s of hydrogen gas. Under such performance, the offered multi-generation plant can be 51.72 and 27.5% efficient from the points of view of energy and exergy, respectively. Further, the total cost rate and environmental impact of the plant are ~3378 US$/h and 294.1 mPts/s, respectively. A comparative analysis is developed to exhibit the superiority of the planned multi-generation plant. A five-objective optimization is also developed to achieve the optimum design data and outcomes of the plant.

Temperature evolution law and strain characteristics of rapid freeze-thaw coal impacted by liquid CO2 -high temperature steam cycles

In view of the fact that the natural melting time of frozen coal is too long in the process of low temperature pneumatic antireflection, and the migration path of unconventional oil and gas is blocked by porous ice. A rapid freeze-thaw antireflection technique for coal seams using liquid CO2 and high temperature water vapor as the medium is proposed. The results show that high temperature steam can significantly promote the melting of liquid CO2 frozen coal. The coal strain changes suddenly when the temperature changes suddenly, and the strain decreases continuously with the temperature conduction becoming stable. With the increase of the number of cold and hot cycle impacts, the time of a single cycle increases first and then decreases. As the degree of metamorphism increases, the strain of coal decreases, and the strain of lignite is 2.71 times that of anthracite. After 6 times of cold and hot cycle impact, the lignite is broken, and the bituminite and anthracite appear macroscopic cracks. In the process of temperature shock, the coal produces residual strain, which first increases and then decreases with the increase of the number of cold and hot cycles.

Energy Recovery from Residual Municipal Solid Waste: State of the Art and Perspectives within the Challenge to Climate Change

Among the technologies for the recovery of energy from waste, in particular residual municipal solid waste (rMSW), combustion is the most widely used thermo-chemical treatment process associated with thermal and electric power production by a steam cycle, named, shortly, Waste to Energy (WtE). Today, more than 500 WtE plants in the EU, about 400 in China and 76 in the USA are in operation, based on efficient technologies and advanced air pollution control systems. Energy recovery can be accomplished also by means of gasification; however, the presence of impurities together with the atmospheric pressure, at which syngas is normally produced, impose the feeding of syngas to a conventional steam cycle, leading to generally lower performances than WtE. The energy recovered by WtE offsets traditional energy sources such as fossil fuels and related emissions, providing savings in term of climate change. However, the savings obtainable by replacing electricity and/or heat will diminish as the energy systems will hopefully become increasingly renewable. Over this medium–long-term horizon, one possibility is to capture the CO2 from WtE flue gases and to store/use it. From the life cycle assessment perspective, it has been calculated that the introduction of CO2 capture and storage in WtE, despite energy penalties, is able to reduce the impact on climate change. The alternative approach, proposed to contain the emissions of greenhouse gases in the thermal treatment of waste, is using the carbon contained in it to produce commonly used chemical compounds (waste to chemicals). The benefits, in terms of reductions of greenhouse gases, are expected from the possibility of obtaining chemicals that can replace their analogue normally produced from fossil sources. To date, only one WtC demonstration plant is operating by being fed by rMSW-derived waste, and some similar initiatives are planned, but still adequate assurances in terms of robust knowledge of the involved complex processes, above all, if applied to highly inhomogeneous feed streams such as those obtained from rMSW, are not available. Once the several initiatives come to completion, it will enable waste management professionals to assess performance and to begin to consider such a facility in their planning.

Thermodynamic and Economic Analysis of a Standalone Supercritical Thermal Power Plant Integrated with Molten Carbonate Fuel Cell

A detailed technoeconomic analysis of a standalone steam cycle integrated with molten carbonate fuel cell and an organic Rankine cycle is presented herein. The modeling and thermodynamic analysis of the proposed plant is performed using a commercially available software tool called Cycle Tempo. The response surface methodology tool is employed to develop regression models to predict the plant's energy, exergy efficiencies, and levelized cost of electricity (LCOE) for varying independent factors: fuel utilization factor (uf) CO2 utilization factor (ϕ), and current density (i) of the fuel cell. The response surfaces developed from the models are used to conduct the parametric analyses on the plant. The desirability test performed for multiobjective optimization has shown the optimum plant configuration, with higher energy, exergy efficiencies, and a lower LCOE is obtained for uf = 0.85, ϕ = 60%, and i = 1000 A m−2 With an intent to reduce CO2 emissions, monoethanolamine‐based carbon capture system is implemented to the plant configuration, that exhibits maximum energy efficiency for ϕ = 90%, and results in an LCOE of 6.53 Rs kWh−1.

Subcritical and supercritical Rankine steam cycles, under elevated temperatures up to 900°C and absolute pressures up to 400 bara

The Rankine cycle is a conceptual arrangement of four processes as a closed vapor power thermodynamic cycle, where a working fluid (especially water as a liquid, as a vapor, and as a liquid-vapor mixture) can be used to convert heat into mechanical energy (shaft rotation). This cycle and its variants are widely used in electric power generation through utility-scale thermal power plants, such as coal-fired power plants and nuclear power plants. In the steam-based Rankine cycle, water should be pressurized and heated to be in the form of very hot high-pressure water vapor called “superheated steam,” before the useful process of expansion inside a steam turbine section occurs. If the absolute pressure and temperature of the superheated steam are both above the critical values for water (220.6 bara and 374.0°C), the cycle is classified as “supercritical.” Otherwise, the cycle is classified as “subcritical.” This study considers the impact of the temperature and pressure, independently, on the performance of a steam Rankine cycle. Starting from a representative condition for a subcritical cycle (600°C peak temperature and 50 bara peak absolute pressure), either the peak temperature or the peak absolute pressure of the cycle is increased with regular steps (up to 900°C, with a temperature step of 50°C, and up to 400 bara, with a pressure step of 50 bar). The variation of five scale-independent performance metrics is investigated in response to the elevated temperature and the elevated pressure. Thus, a total of 10 response curves are presented. When the temperature increased, all the five response variables were improved in a nearly linear profile. On the other hand, increasing the pressure did not give a monotonic linear improvement for each response variable. In particular, the cycle efficiency seemed to approach a limiting maximum value of 45% approximately, where further increases in the pressure cause diminishing improvements in the efficiency. When varying the peak pressure, an optimum minimum ratio of (water-mass-to-output-power) is found at 203 bara, although the cycle efficiency still increases beyond this value. In the present research work, the web-based tool for calculating steam properties by the British company Spirax Sarco Limited, and the software program mini-REFPROP by NIST (United States National Institute of Standards and Technology) were used for finding the necessary specific enthalpies (energy content) of water at different stages within the steam cycle. Both tools were found consistent with each other, as well as with the Python-based software package Cantera for simulating thermo-chemical-transport processes. The results showed that if the peak temperature reaches 900°C, a gain of about 5 percentage points (pp) in the thermal cycle efficiency becomes possible (compared to the case of having a base peak temperature of 600°C), as the predicted efficiency was found to increase from 38.60% (base case) to 43.67%. For the influence of the steam peak pressure, operating in the subcritical regime but close to the critical point appears to be a good choice given the gradual decline in efficiency gains at higher pressures. About 4.7 percentage point increase was found at the high subcritical peak pressure of 200 bara (compared to a base subcritical peak pressure of 50 bara). The results of this study also showed that the liquid water droplet mass fraction at the steam turbine exit diminishes from 11.00% at 600°C to only 1.48% at 900°C, which is favorable. This mass fraction grows from 11.00% at 50 bara to 27.89% at 400 bara, which is not acceptable. Every 100°C increase in the superheating temperature between 600°C and 900°C was found to cause aa increase in the cycle thermal efficiency by about 1.69 percentage points, and simultaneous a beneficial increase in the steam quality at the turbine exit by about 3.17 percentage points.

Supercritical CO2 power cycle

The article is focused on summarizing the issue of energy circuits working with supercritical carbon dioxide sCO2. Carbon dioxide is currently coming to the forefront of many research institutions with regard to its possible use in its supercritical conditions, thanks to which higher efficiency and compactness of equipment can be achieved compared to conventional steam-water cycles. The article describes the basic properties of this medium, including a description of sCO2 cycles (Brayton, Rankine, etc.). Furthermore, the possible use of energy cycles with sCO2 is discussed, especially in solar and nuclear power plants and in power plants burning fossil fuels. In the case of solar power plants, the sCO2 Brayton cycle can offer higher cycle efficiencies than using super-critical steam cycles. The use of sCO2 in nuclear or coal power plants in turn increases efficiency and reduces water consumption. In addition, the use of the sCO2 circuit in new nuclear reactors of the IV generation is currently being considered, in which the operating temperatures are in the range of 500 - 900 °C, i.e. they are generally higher than operating water-cooled reactors. Even though the use of CO2 refrigerant in power systems has been known for a long time (e.g. use in the first Czechoslovak power plant in Jaslovské Bohunice), they are still not used commercially in the energy industry. One of the reasons is the ongoing research into the behavior of materials at high temperatures in sCO2, corrosion protection, or the effect of carbon dioxide purity on behavior in the supercritical region.

Thermodynamic Analysis of the Integrated System that Produces Energy by Gradual Expansion from the Waste Heat of the Solid Waste Facility

The rapid increase in consumer societies leads to a rise in waste facilities. Especially when considering the amount of power used in waste plants and the corresponding waste heat generated, an approach to recover waste heat from these facilities has been proposed. Initially, the waste heat from the solid waste facility was assessed using the Rankine cycle. Subsequently, an Organic Rankine Cycle (ORC) system was integrated into the lower cycle of the steam Rankine cycle. The integrated system was completed by harnessing waste heat from the Rankine steam cycle in the carbon dioxide cycle. These power generation systems are designed with two turbines, each with gradual expansion. Using sub-cycles, 1 kg/s of air at 873.2 K was obtained by evaluating the waste heat. In terms of energy efficiency, it can be observed that the R744 gradual expansion cycle exhibits the highest energy and exergy efficiency. Cooling with water in heat exchangers reduces exhaust efficiency. The highest mass flow requirement is found in the ORC system when the R123 fluid is used. The energy efficiency for the entire system was calculated as 22,4%, and the exergy efficiency for the entire system was calculated as 60.7%. When Exergo Environment Analysis was made, exergy stability factor was found to be %60.7, exergetic sustainability index was found to be 2.66. There is also 370K waste heat available, which is recommended for use in drying units. These calculations were performed using the Engineering Equation Solver (EES) program.