Search Results (112)

Shifting towards electrified industrial energy systems is pivotal for meeting global decarbonization objectives, especially since process heat is a significant contributor to greenhouse gas emissions in the industrial sector. This review examines the changing role of heat exchanger networks (HENs) within electrified process industries, where electricity-driven technologies, including electric heaters, steam boilers, heat pumps, mechanical vapour recompression, and organic Rankine cycles, are increasingly supplanting traditional fossil-fuel-based utilities. The analysis identifies key challenges associated with multi-utility integration, multi-pinch configurations, and low-grade heat utilisation that influence HEN design, retrofitting, and optimisation efforts. A comparative evaluation of various methodological frameworks, including mathematical programming, insights-based methods, and hybrid approaches, is presented, highlighting their relevance to the specific constraints and opportunities of electrified systems. Case studies from the chemicals, food processing, and cement sectors demonstrate the practicality and advantages of employing electrified heat exchanger networks (HENs), particularly in terms of energy efficiency, emissions reduction, and enhanced operational flexibility. The review concludes that effective strategies for the design of HENs are crucial in industrial electrification, facilitating increases in efficiency, reductions in emissions, and improvements in economic feasibility, especially when they are integrated with renewable energy sources and advanced control systems. Future initiatives must focus on harmonising technical advances with system-level resilience and economic sustainability considerations. Full article

Improvement of energy efficiency in technological processes at industrial enterprises is one of the key areas of energy saving. Reduction of energy costs required for the production of energy-intensive products can be achieved through the utilization of waste heat produced by high-temperature thermal furnace units. Generation of electric power based on the waste heat using power cycles with working fluids that are not conventional for large power engineering, may become a promising energy saving trend. In this paper, thermodynamic analysis and optimization of power cycles for the purposes of waste heat recovery are performed. The efficiency of combining several power cycles was also evaluated. It has been established that the combination of the Brayton recompression cycle on supercritical carbon dioxide with the organic Rankine cycle using R124 allows for greater electrical power than steam-power cycles with three pressure circuits under conditions where the gas temperature is in the range of 300–550 °C and the cooling temperature of is up to 80 °C. Additionally, when cooling gases with a high sulfur and moisture content to 150 °C, the combined cycle has greater electrical power at gas temperatures of 330 °C and above. At enterprises where the coolant has a high content of sulfur compounds or moisture and deep cooling of gases will lead to condensation, for example, at petrochemical and non-ferrous metallurgy enterprises, the use of combined cycles can ensure a utilization efficiency of up to 45%. Full article

Parabolic Trough Collectors (PTCs) are a well-established technology for efficiently generating hot water and low-enthalpy steam. For instance, PTCs can be used in steam power systems to drive small Organic Rankine Cycles (ORCs). This study evaluated the thermal efficiency of a PTC equipped with a receiver tube featuring a concentric annular cross-section. This receiver design consists of a tube with a concentric rod inside, forming an annular gap through which the working fluid flows. A thermodynamic model was developed to assess the PTC’s thermal efficiency in hot water and low-enthalpy steam applications. The evaluation considered the First and Second Laws of Thermodynamics, factoring in environmental losses. The model included a bare receiver tube with three-rod diameters—3/8, 1/2, and 3/4 inches—and a range of volumetric flow rates from 1 to 6 L per minute. The results showed improved heat transfer with the annular cross-section receiver compared to a conventional circular one, particularly at lower flow rates of 1 and 2 L per minute. The highest increase in thermal efficiency was observed with the 3/4-inch rod at a flow rate of 1 L per minute, where the maximum efficiency reached 40%. Full article

Today, most of the world’s electric energy is generated by burning hydrocarbon fuels, which causes significant emissions of harmful substances into the atmosphere by thermal power plants. In world practice, flue gas cleaning systems for removing nitrogen oxides, sulfur, and ash are successfully used at power facilities but reducing carbon dioxide emissions at thermal power plants is still difficult for technical and economic reasons. Thus, the introduction of carbon dioxide capture systems at modern power plants is accompanied by a decrease in net efficiency by 8–12%, which determines the high relevance of developing methods for increasing the energy efficiency of modern environmentally friendly power units. This paper presents the results of the development and study of the process flow charts of binary and trinary combined-cycle gas turbines with minimal emissions of harmful substances into the atmosphere. This research revealed that the net efficiency rate of a binary CCGT with integrated post-combustion technology capture is 39.10%; for a binary CCGT with integrated pre-combustion technology capture it is 40.26%; a trinary CCGT with integrated post-combustion technology capture is 40.35%; and for a trinary combined-cycle gas turbine with integrated pre-combustion technology capture it is 41.62%. The highest efficiency of a trinary CCGT with integrated pre-combustion technology capture is due to a reduction in the energy costs for carbon dioxide capture by 5.67 MW—compared to combined-cycle plants with integrated post-combustion technology capture—as well as an increase in the efficiency of the steam–water circuit of the combined-cycle plant by 3.09% relative to binary cycles. Full article

The increasing environmental challenges posed by the widespread use of fossil fuels and the fluctuating nature of renewable energy have driven the need for more efficient and sustainable energy solutions. Current research is actively exploring hybrid energy systems as a means to address these issues. One such area of focus is the integration of Organic Rankine Cycles (ORCs) with gas and steam turbines, utilizing both natural gas (NG) and solar parabolic trough collectors (PTCs) as energy sources. This study examines the performance of a hybrid system implemented in Kirkuk, Iraq, a region known for its substantial solar radiation. Previous research has shown that hybrid systems can effectively enhance energy conversion efficiency and reduce environmental impacts, but there is still a need to assess the specific benefits of such systems in different geographical and operational contexts. The analysis reveals a thermal efficiency of 59.32% and an exergy efficiency of 57.28%. The exergoeconomic analysis highlights the optimal energy cost at USD 71.93/MWh when the compressor pressure ratio is set to 8 bar. The environmental assessment demonstrates a significant reduction in ${\mathrm{C}\mathrm{O}}_2$/emissions, with a carbon footprint of 316.3 kg ${\mathrm{C}\mathrm{O}}_2$/MWh at higher compressor pressure ratios. These results suggest that integrating solar energy with natural gas can substantially improve electricity generation while being both cost-effective and environmentally sustainable. Full article

Growing environmental concerns have driven the installation of renewable systems. Meanwhile, the continuous decline in the levelized cost of energy (LCOE), alongside the decreasing cost of photovoltaics (PVs), is compelling the power sector to accurately forecast the performance of energy plants to maximize plant profitability. This paper presents a comprehensive analysis and optimization of a hybrid power generation system for a remote community in the Middle East and North Africa (MENA) region, with a 10 MW peak power demand. The goal is to achieve 90 percent of annual load coverage from renewable energy. This study introduces a novel comparison between three different configurations: (i) concentrated solar power (parabolic troughs + thermal energy storage + steam Rankine cycle); (ii) fully electric (PVs + wind + batteries); and (iii) an energy mix that combines both solutions. The research demonstrates that the hybrid mix achieves the lowest levelized cost of energy (LCOE) at 0.1364 USD/kWh through the use of advanced transient simulation and load-following control strategies. The single-technology solutions were found to be oversized, resulting in higher costs and overproduction. This paper also explores a reduction in the economic scenario and provides insights into cost-effective renewable systems for isolated communities. The new minimum cost of 0.1153 USD/kWh underscores the importance of integrating CSP and PV technologies to meet the very stringent conditions of high renewable penetration and improved grid stability. Full article

In recent years, fusion energy has assumed an important role in the energy scenario, being a sustainable, environmentally friendly, and practically inexhaustible energy source. Fusion energy could play a crucial role in fully decarbonized electricity production in the second half of this century, helping to meet the increasing energy demand. One of the studied reactors is ARC, a tokamak fusion device characterized by a compact and high-field design initially conceived by researchers at the Massachusetts Institute of Technology, which the Commonwealth Fusion System (CFS) plans to construct in the next decade. This paper is focused on the analysis and development of different configurations for the ARC Balance of Plant Power Conversion System, with the aim of improving the thermodynamic efficiency, which is one of the pillars of sustainability. Three cycles were studied by using the General Electric GateCycle^TM software: a supercritical steam Rankine cycle, a supercritical CO₂ Brayton cycle, and a supercritical helium Brayton cycle. The thermal efficiency of the three options was compared to select the most promising solution. The results showed that the supercritical steam cycle is the best configuration in terms of cycle efficiency for the ARC FNSF Pilot phase. Full article

A Type 22 Broadsword class of frigate uses a combined gas or gas (COGOG) propulsion system that utilizes four different gas turbines, depending on the mode of operation. Its twin ST40M cruise gas turbines are operational most frequently, and an increase in their efficiency would significantly impact fuel usage and ship range. This study evaluates the option to upgrade the cruise gas turbines to a combined gas turbine–electric and steam (COGES) system, which utilizes a steam Rankine cycle to recover energy from the exhaust gases of the gas turbine. An alternative system using hot air is also analyzed for performance comparison. The analysis contains calculations for the energy extraction and dimensions of heat exchangers, for the power extracted from the additional steam or air turbine and for pressure losses of the exhaust gas. Different configurations for the heat exchangers were investigated, as well as various parameters for the steam and hot air. The size and mass of the system were an important aspect of the analysis. It was concluded that an auxiliary system operating at a maximum steam pressure of 20 bar could generate an additional 771 kW of power while adding a mass of 7.4 tons to the frigate. These findings suggest that upgrading to a COGES system could cover the electricity needs of the entire ship and thus reduce the overall fuel consumption, resulting in lower operational costs and less emissions. Full article

Day after day, stricter environmental regulations and rising operating costs and fuel prices are forcing the shipping industry to find more effective ways of designing and operating energy-efficient ships. One of the ways to produce electricity efficiently is to create a waste heat-driven liquid metal–water binary vapor power plant. The liquid metal Rankine cycle systems could be considered topping cycles. Liquid metal binary cycles share characteristics like those of the steam Rankine power plants. They have the potential for high conversion efficiency, they will likely produce lower-cost power in plants of large capacity rather than small, and they will operate more efficiently at design capacity rather than at partial load. As a result, liquid metal topping cycles may find application primarily as base-load plants onboard ships. In this study, a waste heat-driven liquid metal–water binary vapor power plant onboard a ship is designed and thermodynamically analyzed. The waste heat onboard the vessel is the exhaust gas of the LM2500 marine gas turbine. Mercury and Cesium are selected as liquid metals in the topping cycle, while water is used in the bottoming cycle in binary power plants. Engineering Equation Solver (EES) software (V11.898) is used to perform analyses. For the turbine inlet temperature of 550 °C, while the total net work output of the binary cycle system is calculated to be 104.84 kJ/kg liquid metal and 1740.29 kJ/kg liquid metal for mercury and cesium, respectively, the efficiency of the binary cycle system is calculated to be 31.9% and 26.3% for mercury and cesium as liquid metal, respectively. This study shows that the binary cycle has a thermal efficiency of 26.32% and 31.91% for cesium and mercury, respectively, depending on liquid metal condensing pressure, and a binary cycle thermal efficiency of 25.9% and 30.9% for cesium and mercury, respectively, depending on liquid metal turbine inlet temperature, and these are possible with marine engine waste heat-driven liquid metal–water binary vapor cycles. Full article

Internal combustion engines (ICEs) are one of the significant sources of wasted energy, with approximately 65% of their input energy being wasted and dissipated into the environment. Given their wide usage globally, it is necessary to find ways to recover their waste energies, addressing this inefficiency and reducing environmental pollution. While previous studies have explored various aspects of waste energy recovery, a comparative analysis of different bottoming configurations has been lacking. In this research, an extensive review of the existing literature was conducted by an exploration of four key bottoming cycles: the steam Rankine cycle (SRC), CO₂ supercritical Brayton cycle, inverse Brayton cycle (IBC), and air bottoming cycle. In addition, these four main bottoming systems are utilized for the waste energy recovery of natural gas-fired ICE with a capacity of 584 kW and an exhausted gas temperature of 493 °C. For the efficient waste heat recovery of residual exhausted gas and heat rejection stage of the main bottoming system, two thermoelectric generators are utilized. Then, the produced power in bottoming systems is sent to a proton exchange membrane electrolyzer for hydrogen production. A comprehensive 4E (energy, exergy, exergy-economic, and environmental) optimization is conducted to find the best main bottoming system for hydrogen production. Results showed that the SRC-based system has the highest exergy efficiency (21.93%), while the IBC-based system results in the lowest efficiency (13.72%), total cost rate (25.58 $/h), and unit cost of hydrogen production (59.91 $/GJ). This combined literature review and research article underscore the importance of finding an economically efficient bottoming cycle in the context of waste energy recovery and hydrogen production. Full article

Rising energy demands, the depletion of fossil fuels, and their environmental impact necessitate a shift towards sustainable power generation. Concentrating solar power (CSP) offers a promising solution. This study examines a hybridization of a combined cycle power plant (CCPP) based on solar energy with fossil fuel and energy storage in rock layers to increase Saudi Arabia’s electricity production from renewable energy. The fuel is used to keep the temperature at the inlet of the gas turbine at 1000 °C, ensuring the power produced by the Rankine cycle remains constant. During the summer, the sun is the main source of power generation, whereas in the winter, reliance on fuel increases significantly. The Brayton cycle operates for 10 h during peak solar radiation periods, storing exhaust heat in rock beds. For the remaining 14 h of the day, this stored heat is discharged to operate the Rankine steam cycle. Simulations and optimizations are performed, and the system is evaluated using a comprehensive 4E analysis (energy, exergy, exergoconomic, and environmental) alongside a sustainability assessment. A parametric evaluation examines the effect of key factors on system performance. The rock bed storage system compensates for solar intermittency, enabling power generation even without sunlight. The study reveals that the system generated 12.334 MW in June, achieving an energy efficiency of 37% and an exergy efficiency of 40.35%. The average electricity cost during this period was 0.0303 USD/kWh, and the carbon footprint was 0.108 kg CO₂/kWh. In contrast, during January, the system produced 13.276 MW with an energy efficiency of 37.91% and an exergy efficiency of 44.16%. The average electricity cost in January was 0.045 USD/kWh, and the carbon footprint was 0.1 kg CO₂/kWh. Interestingly, solar energy played a significant role: it contributed 81.42% of the heat in June, while in January, it accounted for 46.77%. The reduced electricity costs during June are primarily attributed to the abundant sunshine, which significantly powered the system. Full article

Worldwide, the growing demand for energy has been largely met through power cycles utilizing fossil fuels. Combined cycles, which integrate a gas turbine with a steam cycle, prove to be the best alternative due to their power generation capacity and high efficiencies. This efficiency is primarily attributed to the ability to harness exhaust gases to generate steam in the heat recovery boiler, allowing additional power generation through the steam turbine. Currently, there is a quest for the integration of low-temperature power cycles to maximize the utilization of residual thermal energy flows for power generation. Therefore, this work conducts an exergetic optimization of a power trigeneration system aimed at maximizing exergetic efficiency. This system includes a gas turbine and a steam cycle coupled with three different configurations of the Organic Rankine Cycle (ORC): a simple ORC, a supercritical ORC, and an ultracritical ORC. The ORC configurations are analyzed using eight organic working fluids, namely R1234yf, R290, R134a, R1234ze, R152a, R600a, R245fa, and R123. The results show that the maximum exergetic efficiency is achieved by using R152a in the ultracritical ORC configuration coupled with the combined cycle, achieving an exergetic efficiency of 55.79%. Furthermore, the maximum power generated is attained by the steam cycle with 85,600.63 kW and 3101.21 kW for the ultracritical ORC. Full article

Adopting biomass energy as an alternative to fossil fuels for electricity production presents a viable strategy to address the prevailing energy deficits and environmental concerns, although it faces challenges related to suboptimal energy efficiency levels. This study introduces a novel combined cooling and power (CCP) system, incorporating an externally fired gas turbine (EFGT), steam Rankine cycle (SRC), absorption refrigeration cycle (ARC), and organic Rankine cycle (ORC), aimed at boosting the efficiency of biomass integrated gasification combined cycle systems. Through the development of mathematical models, this research evaluates the system’s performance from both thermodynamic and exergoeconomic perspectives. Results show that the system could achieve the thermal efficiency, exergy efficiency, and levelized cost of exergy (LCOE) of 70.67%, 39.13%, and 11.67 USD/GJ, respectively. The analysis identifies the combustion chamber of the EFGT as the component with the highest rate of exergy destruction. Further analysis on parameters indicates that improvements in thermodynamic performance are achievable with increased air compressor pressure ratio and gas turbine inlet temperature, or reduced pinch point temperature difference, while the LCOE can be minimized through adjustments in these parameters. Optimized operation conditions demonstrate a potential 5.7% reduction in LCOE at the expense of a 2.5% decrease in exergy efficiency when compared to the baseline scenario. Full article

Libya is facing a serious challenge in its sustainable development because of its complete dependence on traditional fuels in meeting its growing energy demand. On the other hand, more intensive energy utilization accommodating multiple energy resources, including renewables, has gained considerable attention. This article is motivated by the obvious need for research on this topic due to the shortage of applications concerning the prospects of the hybridization of energy systems for electric power generation in Libya. The 283 MW single-cycle gas turbine operating at the Sarir power plant located in the Libyan desert is considered a case study for a proposed Integrated Solar Combined Cycle (ISCC) system. By utilizing the common infrastructure of a gas-fired power plant and concentrating solar power (CSP) technology, a triple hybrid system is modeled using the EES programming tool. The triple hybrid system consists of (i) a closed Brayton cycle (BC), (ii) a Rankine cycle (RC), which uses heat derived from a parabolic collector field in addition to the waste heat of the BC, and (iii) an organic Rankine cycle (ORC), which is involved in recovering waste heat from the RC. A thermodynamic analysis of the developed triple combined power plant shows that the global power output ranges between 416 MW (in December) and a maximum of 452.9 MW, which was obtained in July. The highest overall system efficiency of 44.3% was achieved in December at a pressure ratio of 12 and 20% of steam fraction in the RC. The monthly capital investment cost for the ISCC facility varies between 52.59 USD/MWh and 58.19 USD/MWh. From an environmental perspective, the ISCC facility can achieve a carbon footprint of up to 319 kg/MWh on a monthly basis compared to 589 kg/MWh for the base BC plant, which represents a reduction of up to 46%. This study could stimulate decision makers to adopt ISCC power plants in Libya and in other developing oil-producing countries. Full article

Waste heat recovery from exhaust gas is one of the most convenient methods to save energy in internal combustion engine-driven vehicles. This paper aims to investigate a reduction in waste heat from the exhaust gas of an internal combustion engine of a serial Diesel–electric hybrid bus by recovering part of the heat and converting it into useful power with the help of a split-flow supercritical CO₂ (sCO₂) recompression Brayton cycle. It can recover 17.01 kW of the total 33.47 kW of waste heat contained in exhaust gas from a 151 kW internal combustion engine. The thermal efficiency of the cycle is 38.51%, and the net power of the cycle is 6.55 kW. The variation in the sCO₂ temperature at the shutdown of the internal combustion engine is analyzed, and a slow drop followed by a sudden and then a slow drop is observed. After 80 s from stopping the engine, the temperature drops by (23–33)% depending on the tube thickness of the recovery heat exchanger. The performances (net power, thermal efficiency, and waste heat recovery efficiency) of the split-flow sCO₂ recompression Brayton cycle are clearly superior to those of the steam Rankine cycle and the organic Rankine cycle (ORC) with cyclopentane as a working fluid. Full article