Combined Power Research Articles

Modeling of calculations on the performance optimization of a double-flash geothermal renewable energy-based combined heat/power plant coupled by transcritical carbon dioxide rankine cycle

This study investigates the integration of a double-flash geothermal system with a transcritical CO2 Rankine cycle, presenting a groundbreaking approach for enhancing efficient and sustainable energy generation. By harnessing renewable geothermal resources, this combined heat and power system aims to minimize greenhouse gas emissions, contributing to a more sustainable future. The research emphasizes multi-objective optimization to maximize net power output, net heating capacity, and overall system efficiency. The expanded stream pressures from the expansion valves, denoted as P2 and P6, are systematically varied to evaluate their impact on system performance. Significant findings reveal that as P6 increases from 260 kPa to 640 kPa, net power output rises dramatically from 2688 kW to 3163 kW. The optimal conditions for peak performance are identified at P2 of 820 kPa and P6 of 640 kPa, resulting in impressive outcomes: a net power output of 3392 kW, a net heating capacity of 14,586 kW, and an overall efficiency of 52.65 %. By delineating these relationships and establishing benchmarks for performance, this research offers valuable insights for the scientific community, policymakers, and industry stakeholders aiming to advance geothermal energy technologies.

Bi-Level Operation Optimization and Performance Analysis for a Distributed Energy System with Energy Network

The increasing energy crisis and environmental problems promote the development of distributed energy systems (DESs) that utilize combined heat and power technology, renewable energy technology, and waste heat recovery technology to meet various load requirements. Although there is existing work and research on a variety of DESs, most previous studies tend to focus on energy production with little consideration of a distributed energy network and its energy loss, which results in large errors in energy-efficiency calculations and performance analyses. In this paper, a new DES model is proposed with full consideration of an energy network and the full use of solar energy, terrestrial heat, and exhaust gases. At the same time, an effective bi-level optimization method is also proposed for the daily operation of the DES in order to improve the system performance and benefits in the energy, the economy, and the environment. Specifically, the co-generation energy station and water heating network in the DES are optimized separately with two different optimization models. The first-level optimization model is used to seek the optimal values of water mass flow rate and water temperature of the water heating network, and the second-level optimization model is built to determine the optimal energy purchasing strategy and the optimal energy outputs of the co-generation energy station. In order to verify the advantages and effectiveness of the proposed system and method, a contrastive simulation study is undertaken to provide a comparison of the global optimization method. Simulation results show that energy loss, energy cost, and energy consumption of the DES using the bi-level optimization operation strategy only account for 22.51%, 33.42%, and 51.31% of the quantities of the global optimization method, respectively. The hourly curves of the optimal operating variables also demonstrate that the proposed bi-level optimization method can improve the operating stability of the DES better than the global optimization method.

Closing the Loop between Plastic Waste Management and Energy Cogeneration: An Innovative Design for a Flexible Pyrolysis Small-Scale Unit

This study proposes a simplified unit that can be employed in an industrial facility for the utilization of its own abundant plastic waste, primarily from discarded packaging, to achieve full or partial energy autonomy. By converting this waste into synthetic pyrolysis oil equivalent to 91,500 L, the industry can power a combined heat and power generation unit. The proposed unit was designed with a focus on maintaining high temperatures efficiently while minimizing oxygen exposure to protect the integrity of hydrocarbons until they transform into new compounds. Pyrolysis stands as a foundational procedure, paving the way for subsequent thermochemical transformations such as combustion and gasification. This study delves into the factors affecting pyrolysis and presents analytically the mathematical formulations and relevant calculations in order to effectively design and apply a real-life system. On this basis, fuels from plastic waste can be produced, suitable for utilization in typical equipment meant to produce heat, estimated for six months’ operation and 800 MWh of electricity. This study enhances the transition towards a more circular and resource-efficient economy with technologies that unlock the latent energy contained within the discarded matter. Additionally, it demonstrates the feasibility of a moderate investment in a co-generation system for industries utilizing 568 tonnes of plastic waste per year. The design and accurate calculations of this study highlight the theoretical potential of this technology, promoting environmental sustainability and resource conservation.

Experimental and theoretical assessment of the effects of electrical load variation on the operability of a small-scale Organic Rankine Cycle (ORC)-based unit equipped with a hermetic scroll expander

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

Home energy management system for residential fuel cell-based combined heat and power system

The goal of this paper is to propose an optimization scheme for enhancing power dispatch and load scheduling for residential fuel cell-based combined heat and power systems (FC-CHPS) using mixed integer linear programming (MILP), considering the lifetime degradation of both the fuel cell system (FCS) and battery energy storage systems (BESS). The scheme is applied in the home energy management system that oversees the electric and thermal power of residential FC-CHPS. First, the nonlinearity in the relationship between the natural gas consumption and output electric power, and between the residual thermal power and output electric power of the fuel cell system (FCS) in the FC-CHPS is approximated using piecewise linearization. Then, the piecewise linearization is integrated with MILP to derive optimal power dispatch and load scheduling solutions, while accounting for the nonlinearity of the FCS. Next, cost functions representing the lifetime degradation of FCS and BESS are formulated. These cost functions result in nonlinear optimization constraints. Therefore, innovative methods are proposed to linearize these constraints, allowing the continued use of MILP as the optimization method and factoring in the lifetime degradation of FCS and BESS. Compared to the mixed-integer non-linear programming (MINLP) method that does not linearize the non-linearity in the FCS or the lifetime degradation of the FCS and BESS, the proposed MILP scheme achieves the identical objective function value. Furthermore, the computation time for the proposed MILP scheme is 99.94 % lower than that required by the MINLP method. The proposed scheme provides accurate results in short computation times.

A theoretical thermodynamic investigation on solar-operated combined electric power, heating, and ejector cooling cycle driven by an ORC turbine waste heat, tri-generation cycle system

The current study investigated a solar thermal power plant to simultaneously produce multiple energy outputs, including electric power, process heating, and cooling. This integrated approach aligns with the concept of a tri-generation system, where three different forms of energy are produced from a single source. The study involves a parametric analysis, where the impact of each influencing parameter including, turbine inlet temperature, and turbine inlet pressure is systematically varied with DNI ranging from 600 W/m2 to 1000 W/m2 to understand its effects on both first-law and second-law efficiencies. Further, the exergy analysis shows the irreversibility's occur within the system. Notably, the central receiver and heliostat are identified as major sources of exergy loss. The comparison to a combined power and heating (CPH) cycle without an ORC-ejector indicates that the additional technologies significantly contribute to improving the system's performance, approximately 3.97 % and 2.3 % for both efficiencies, respectively.

Quantifying the informativity of emission lines to infer physical conditions in giant molecular clouds. I. Application to model predictions

Observations of ionic, atomic, or molecular lines are performed to improve our understanding of the interstellar medium (ISM). However, the potential of a line to constrain the physical conditions of the ISM is difficult to assess quantitatively, because of the complexity of the ISM physics. The situation is even more complex when trying to assess which combinations of lines are the most useful. Therefore, observation campaigns usually try to observe as many lines as possible for as much time as possible. We have searched for a quantitative statistical criterion to evaluate the full constraining power of a (combination of) tracer(s) with respect to physical conditions. Our goal with such a criterion is twofold. First, we want to improve our understanding of the statistical relationships between ISM tracers and physical conditions. Secondly, by exploiting this criterion, we aim to propose a method that helps observers to make their observation proposals; for example, by choosing to observe the lines with the highest constraining power given limited resources and time. We propose an approach based on information theory, in particular the concepts of conditional differential entropy and mutual information. The best (combination of) tracer(s) is obtained by comparing the mutual information between a physical parameter and different sets of lines. The presented analysis is independent of the choice of the estimation algorithm ( neural network or $ minimization). We applied this method to simulations of radio molecular lines emitted by a photodissociation region similar to the Horsehead Nebula. In this simulated data, we considered the noise properties of a state-of-the-art single dish telescope such as the IRAM 30m telescope. We searched for the best lines to constrain the visual extinction or the ultraviolet illumination field . We ran this search for different gas regimes, namely translucent gas, filamentary gas, and dense cores. The most informative lines change with the physical regime ( cloud extinction). However, the determination of the optimal (combination of) line(s) to constrain a physical parameter such as the visual extinction depends not only on the radiative transfer of the lines and chemistry of the associated species, but also on the achieved mean signal-to-noise ratio. The short integration time of the CO isotopologue $J=1-0$ lines already yields much information on the total column density for a large range of ( ) space. The best set of lines to constrain the visual extinction does not necessarily combine the most informative individual lines. Precise constraints on the radiation field are more difficult to achieve with molecular lines. They require spectral lines emitted at the cloud surface ( and lines). This approach allows one to better explore the knowledge provided by ISM codes, and to guide future observation campaigns.

Sky localization of space-based detectors with time-delay interferometry

The accurate sky localization of gravitational wave (GW) sources is an important scientific goal for space-based GW detectors. The main differences between future space-based GW detectors, such as Laser Interferometer Space Antenna (LISA), Taiji, and TianQin, include the time-changing orientation of the detector plane, the arm length, the orbital period of the spacecraft and the noise curve. Because of the effects of gravity on three spacecraft, it is impossible to maintain the equality of the arm length, so the time-delay interferometry (TDI) method is needed to cancel out the laser frequency noise for space-based GW detectors. Extending previous work based on equal-arm Michelson interferometer, we explore the impacts of different first-generation TDI combinations and detector's constellations on the sky localization for monochromatic sources. We find that the sky localization power is almost unaffected by the inclusion of the TDI Michelson (X, Y, Z) combination in the analysis. We also find that the variation in the sky localization power for different TDI combinations is entirely driven by the variation in the sensitivities of these combinations. For the six particular TDI combinations studied, the Michelson (X, Y, Z) combination is the best for source localization.

A novel configuration optimization approach for IES considering exergy-degradation and non-energy costs of equipment

Improving the exergy utilization and economic performance is the core goal for the configuration optimization of the integrated energy system (IES). Achieving such a goal requires accurate evaluation of the exergy efficiency and economy. However, IES is a multisource heterogeneous and strongly coupled system. The development of reasonable exergy efficiency-economy characteristic evaluation indicators is a complex issue that limits its application in IES configuration. This article proposes a novel IES configuration optimization approach based on the concept of the equipment exergyeconomic cost coefficient. The exergyeconomic cost coefficient consists of the exergy-degradation and non-energy costs, which can quantitatively characterize the exergy efficiency and economy of the IES under a unified benchmark. A mechanism model for the equipment exergyeconomic cost coefficient, output of various equipment and total exergyeconomic cost is established. Furthermore, exergy flow attribute classification method is proposed to obtain the equipment exergyeconomic cost coefficient in the IES. The proposed method is verified in a real-world study case located in Yancheng, China. Compared to the conventional configuration method, the capacity of the renewable energy and combined heat and power generation (CHP) are enhanced, while the capacity of purchased electricity and electric boiler (EB) are reduced. It can obtain the minimum total exergyeconomic cost (TEC) for the IES. This study offers a new direction for the optimal configuration of IES.

Probing the physics of star formation (ProPStar)

Context. Turbulence is a key component of molecular cloud structure. It is usually described by a cascade of energy down to the dissipation scale. The power spectrum for subsonic incompressible turbulence is ∝k−5/3, while for supersonic turbulence it is ∝k−2. Aims. We determine the power spectrum in an actively star-forming molecular cloud, from parsec scales down to the expected magnetohydrodynamic (MHD) wave cutoff (dissipation scale). Methods. We analyzed observations of the nearby NGC 1333 star-forming region in three different tracers to cover the different scales from ∼10 pc down to 20 mpc. The largest scales are covered with the low-density gas tracer 13CO (1–0) obtained with a single dish, the intermediate scales are covered with single-dish observations of the C18O (3–2) line, while the smallest scales are covered in H13CO+ (1–0) and HNC (1–0) with a combination of NOEMA interferometer and IRAM 30m single-dish observations. The complementarity of these observations enables us to generate a combined power spectrum covering more than two orders of magnitude in spatial scale. Results. We derive the power spectrum in an active star-forming region spanning more than 2 decades of spatial scales. The power spectrum of the intensity maps shows a single power-law behavior, with an exponent of 2.9 ± 0.1 and no evidence of dissipation. Moreover, there is evidence that the power spectrum of the ions to have more power at smaller scales than the neutrals, which is opposite to the theoretical expectations. Conclusions. We show new possibilities for studying the dissipation of energy at small scales in star-forming regions provided by interferometric observations.

The Value of Biomarkers in Major Cardiovascular Surgery Necessitating Cardiopulmonary Bypass.

The use of biomarkers in cardiovascular surgery is an evolving field with promising potential; however, current research remains largely limited, requiring further validation for routine clinical application. This review explores the application of biomarkers in cardiovascular surgery, focusing on heart failure, cardiac ischemia, and organ dysfunction, including renal, cerebral, pulmonary, and splanchnic impairments. Additionally, it examines the significance of biomarkers in assessing the inflammatory state and oxidative stress during the perioperative period, particularly in the context of major surgical trauma and cardiopulmonary bypass (CPB). From January 2018 to June 2024, we reviewed 133 studies and four systematic reviews and meta-analyses using the Medline, Embase, and Central databases, screening for pre- or postoperative biomarker levels in patients undergoing cardiac surgery. Outcomes of interest were postoperative mortality, nonfatal myocardial infarction, stroke, congestive heart failure, and major adverse cardiovascular events (MACEs). Studies reporting multivariable-adjusted risk estimates were included. The findings revealed that cardiac troponins (cTns) and creatine kinase isoenzyme MB (CK-MB) remain the most widely utilized biomarkers for assessing myocardial injury post-surgery. These elevated biomarker levels were consistently associated with an increased risk of postoperative complications, including low cardiac output syndrome, prolonged ventilation, and mortality. Emerging biomarkers, such as heart-type fatty acid-binding protein (h-FABP) and high-sensitivity C-reactive protein (hs-CRP), demonstrated promising early detection and risk stratification results. In particular, h-FABP increased rapidly within one hour of myocardial injury, peaking at 4-6 hours and returning to baseline within 24 hours. This rapid clearance makes h-FABP a valuable tool for early myocardial injury detection, potentially allowing for timely interventions. Inflammatory biomarkers, including hs-CRP and pentraxin 3 (PTX3), were found to be associated with poor outcomes, such as increased morbidity and mortality. Elevated preoperative levels of these markers were indicative of a heightened inflammatory response, correlating with worse postoperative recovery and higher rates of complications. Furthermore, the neutrophil-to-lymphocyte ratio (NLR) emerged as a cost-effective and easily accessible predictor of postoperative outcomes. Elevated NLR values were linked to an increased risk of adverse events, including prolonged ventilation, low cardiac output syndrome, and overall mortality. Further, the practicality of measuring NLR through routine blood tests makes it viable for widespread clinical use. In conclusion, integrating biomarkers in cardiovascular surgery significantly advances predicting postoperative outcomes for cardiac surgery patients. Therefore, it is essential to categorize these biomarkers into two distinct groups in the future, inflammatory and non-inflammatory (related to organ damage), to improve understanding and enhance their clinical applicability. Future research should focus on standardizing the use of these biomarkers and exploring their combined predictive power to enhance risk stratification and improve patient prognosis.

ARCHITECTURAL AND CIRCUIT MODEL OF NAVIGATION DEVICE FOR ULTRA-LIGHT LAUNCH VEHICLE

The paper considered the architectural and circuitry model of a navigation device for an ultra-lightweight launch vehicle designed to improve the accuracy and reliability of positioning and orientation in flight conditions. The study utilized modern approaches to the integration of global navigation satellite system (GNSS) and inertial navigation system (INS) to achieve high accuracy and stability of the system. The key components of the device including UM980 module, LSM6DSV32X inertial measurement module, STM32 F7 series microcontroller, E220-400T30S radio module, LMR50410XDBVR converter based power supply and RS422 interface were described in detail. The UM980 module, including SAW and LNA filter blocks, demonstrated the ability to efficiently process incoming RF signals. The NebulasIV main function block combined GNSS BB, GNSS RF, interfaces and power management unit (PMU) modules, supporting multiple communication interfaces such as UART, SPI and I²C, as well as RTK and PPS signals. The study analyzed the integration and accuracy aspects of the module in navigation systems. The signal processing scheme of the inertial navigation system module was also presented, including digital filters, free-fall and activity/inactivity detection functions, and interfaces for data communication. User bias functions and filter modes are considered to ensure the accuracy and stability of the navigation device. The work lays the groundwork for further improvements in navigation technology, especially in the context of increasing availability and accuracy for small scale space launches.

Coordinated control algorithm of hydrogen production-battery based hybrid energy storage system for suppressing fluctuation of PV power

Photovoltaic (PV) power generation has issues of volatility and intermittency. Currently, PV plants are generally equipped with 10% rated capacity lithium-ion (Li) battery energy storage systems in China, who often fail to suppress fluctuation in the output power of PV plants effectively and meet the grid-connected standard. The hybrid energy storage system (HESS) combining with hydrogen production and Li battery system can produce hydrogen by water electrolysis during the peak period of PV power generation, effectively improving PV utilization efficiency, while smoothing PV power fluctuation and improving grid connection electricity quality. Firstly, models of the solid oxide electrolysis cell (SOEC) and alkaline electrolysis cell (AEC) systems for hydrogen production, and Li battery energy storage system are established, and the transient response characteristics of each system are analyzed. Secondly, an adaptive wavelet packet decomposition (AWPD) method for PV power signal decomposition is proposed based on the wavelet packet decomposition (WPD) method. Thirdly, a capacity configuration method for HESS are proposed based on the APWD method. Fourthly, a coordinated control strategy for HESS is proposed with the transient response characteristics of different energy storage systems and the state of charge for Li battery system. Finally, the proposed method is validated through simulation experiments based on the actual power data of the PV plant. The results show that the developed methods can effectively utilize partial PV power generation to produce hydrogen, improve PV utilization, and the combined output power of PV plant and HESS can fulfill the grid-connected standard.

Hydrogen vs. conventional sector-coupling residential energy systems: An economic and environmental comparison based on multi-objective design optimization

Planning residential energy systems faces economic, environmental, and technical challenges, necessitating cost-effective and environmentally friendly solutions. Hydrogen technologies in districts have recently gained interest. However, their economic and environmental potential relative to conventional technologies remains largely unexplored. Therefore, we quantitatively compared the impacts of designing hydrogen-based and conventional sector-coupling systems on total costs and CO2 emissions.We developed a multi-objective optimization model for the design and operation of generation and storage units, aiming to minimize total costs and CO2 emissions. We created three energy system configurations for an exemplary German district, each involving photovoltaics, heat storage, and batteries, while varying the main heat supplier. The first configuration includes a gas combined heat and power unit, the second features a heat pump, and the third incorporates a fuel cell, an electrolyzer, and hydrogen storage.Our comparison of the Pareto fronts revealed that the hydrogen system’s cost is 83% higher than the gas-based system and 33% higher than the heat-pump-based system. Environmentally, the hydrogen system emits 11% less than the gas-based system but 47% more than the heat-pump-based system. In conclusion, hydrogen units offer environmental benefits through improved photovoltaic utilization but perform poorly economically due to high investment and operating costs.

Model-based evaluation of ammonia energy storage concepts at high technological readiness level

Ammonia is a promising carbon-free energy carrier since it can be stored as a liquid at mild conditions and its production process from hydrogen and nitrogen is established and efficient. Several Ammonia-to-Power concepts have been proposed in the literature, many of which employ not-yet-mature electrochemical technologies. We model the charging and discharging phases of three ammonia energy storage concepts in Aspen Plus seeking a compromise between efficient concepts and mature technologies. In the charging phase, ammonia is produced via the Haber–Bosch process using hydrogen from low-temperature water electrolysis for all the considered concepts. For the discharging phase, three ammonia conversion processes are modeled: (i) ammonia is thermally decomposed into nitrogen and hydrogen by using thermal energy from storage, and hydrogen is converted into electricity in a fuel cell; (ii) ammonia is thermally decomposed by using heat generated through the combustion of a fraction of the ammonia stream, and the produced hydrogen is supplied to a fuel cell; (iii) ammonia is used as a fuel in a combined power cycle. We compare these concepts with respect to roundtrip efficiency and levelized cost of electricity. The roundtrip efficiency and the levelized cost of electricity of the modeled concepts are ca. 30–34 % and 0.28–0.31 €kWh−1 (for an electricity purchase price of 0.03 €kWh−1). Concept (i) has both the highest roundtrip efficiency and the lowest levelized cost of electricity. We identify the process bottlenecks via an exergy analysis.

JWST MIRI Detections of Hα and [O iii] and a Direct Metallicity Measurement of the z = 10.17 Lensed Galaxy MACS0647−JD

JWST spectroscopy has revolutionized our understanding of galaxies in the early Universe. Covering wavelengths up to 5.3 μm, NIRSpec can detect rest-frame optical Hα emission lines out to z = 7 and [O iii] to z = 9.5. Observing these lines in more distant galaxies requires longer wavelength spectroscopy with MIRI. Here we present MIRI Medium Resolution Spectrograph integral field unit observations of the lensed galaxy merger MACS0647–JD at z = 10.165. With exposure times of 4.2 hr in each of two bands (SHORT and LONG), we detect Hα at 9σ, [O iii] λ5008 at 11σ, and [O iii] λ4960 at 3σ. Combined with previously reported NIRSpec spectroscopy that yielded seven emission lines including the auroral line [O iii] λ4363, we present the first direct metallicity measurement of a z > 10 galaxy: 12+log(O/H)=7.79±0.09 , or 0.13−0.03+0.02Z⊙ . This is similar to galaxies at z ∼ 4–9 with direct metallicity measurements, though higher than expected given the high specific star formation rate log(sSFR/yr−1) = −7.4 ± 0.3. We further constrain the ionization parameter log(U) = −1.9 ± 0.1, ionizing photon production efficiency log(ξ ion) = 25.3 ± 0.1, and SFR = 5.0 ± 0.6 M ⊙ yr−1 within the past 10 Myr. These observations demonstrate the combined power of JWST NIRSpec and MIRI for studying galaxies in the first 500 million years.

Population data for 12 X-STRs loci in Malaysian Malay and Chinese populations

The utilization of X-chromosome short tandem repeats (X-STRs) for human identification particularly in resolving complex kinship cases has been advocated. Since, forensic statistical parameters vary among different populations, and because the X-STRs population data representing the diverse population of Peninsular Malaysia remain unavailable, the specific attempt reported here for the Malays (n = 224) and Chinese (n = 201) populations appears forensically relevant to support the evidential value of the 12 X-STRs markers for human identification in Malaysia. Results derived from the Qiagen Investigator® Argus X-12 kit revealed that DXS10135 as the most polymorphic locus with high genetic diversity, polymorphic information content, heterozygosity as well as power of exclusion. Based on allele frequencies, the combined power of discrimination as well as the mean exclusion chance (MECKrüger, MECKishida, MECDesmarais and MECDesmaraisDuo) values for the Malays and Chinese were individually ≥0.999995532964908. As for the combined power of discrimination as well as the mean exclusion chance (MECKrüger, MECKishida, MECDesmarais and MECDesmaraisDuo) calculated based on haplotype frequencies, the values were ≥0.9999986410567 for the Malays and Chinese populations. In addition, results from the genetic distance, neighbor-joining phylogenetic tree and principal component analysis revealed close biogeographical distributions of the studied populations with other South East Asian populations. Hence, the utilization of the X-STRs data for identifying individuals among the Malays and Chinese populations in Peninsular Malaysia for forensic application appears as highly supported.

Economic Analyses of a New Power and Cooling System at Low Temperature Applications

Recent research suggests that the implementation of more efficient combined cooling and power systems, which enable the cogeneration of electricity and cooling, can enhance the efficiency of hybrid plants. The present investigation is motivated by finding that, in the literature review on combined power and cooling systems, there is very limited information on the coupling of the organic Rankine cycle (ORC) and the ejector refrigeration cycle (ERC) with low sink temperatures. A suggested approach to do this involves using hot exhaust gas and waste heat engines to power an ORC hybrid system. To enhance the ORC–ERC system's performance, three heater configurations use waste heat from the ORC turbine exhaust, ejector, and engine waste heat to heat the working fluid. Renewable energy sources are the primary focus of most current research initiatives. The present research focuses on unique ORC and ERC systems, considered as combined power and cooling systems, with the goal of improving exergy performance at low temperatures. The suggested ORC–ERC can generate energy destruction of 69.85 kW at a source temperature of 155 °C, with an exergetic efficiency of 76.9% at the turbine. Setting the entrainment ratio at 0.5 results in a total sum unit cost of products (SUCP) of 465 $/kW‐h for the ORC–ERC. Furthermore, the 37.83% exergy destruction ratio introduces heat exchanger 2 (HE2) as the primary cause of the suggested ORC–ERC's irreversibility. A detailed parametric study reveals that altering the hot source temperature and entrainment ratio improves the system's SUCP. The current examination at high sink temperatures may be expanded to an advanced exergoenvironmental investigation.

Determining optimal component configurations for flexible biogas plants based on power prices of 2020–2022 and the legislation framework in Germany

The aim of this study is to find optimal component configurations for flexible biogas plants considering electricity prices in Germany, for maximum annuities considering costs and revenues. Cases for solely power-price driven operation and cogeneration-led operation were investigated for electricity prices in 2020, 2021, and 2022 in hourly resolution.Additional revenue from flexible operation increases as price volatility increased from 2020 to 2022. Interestingly, the choice of capacity for the combined heat and power unit (CHPU) is determined by the expected service life of the CHPU. Irrespective of electricity market signals, power quotients (PQ) of at least PQ = 4 avoid reinvestment for the CHPU within 20 years.Another result is that the the optimality region for CHPU capacity flattens for 2022 and shift to capacities above PQ = 4. Thus, high price volatility will allow plant operators to amortise even larger CHPUs, which could stimulate the installation of peak load by flexible biogas plants. Considering the day-ahead market can provide clear recommendations for optimal component configurations.The presented Smart-Force-Optimisation (SFO) combines a prefiltering of schedules matching given constraints and a brute force optimisation to the filtered subset. Thus, SFO has an improved performance comparing to bare brute force approaches.

Dynamic simulation and optimal design of a combined cold and power system with 10 MW compressed air energy storage and integrated refrigeration

A combined cold and power system with 10 MW compressed air energy storage and integrated refrigeration (CCR) is proposed. In traditional 10 MW compressed air energy storage (CAES) system, outlet pressure of air tank is throttled to a low pressure by throttling device. In CCR system, the throttling device is replaced by a piston turbine to achieve control of pressure and mass flow. Meanwhile, pressure potential energy of compressed air is converted to mechanical work, which is used to drive refrigeration subsystem. The dynamic mathematic model of proposed CCR system is built up. According to energy and exergy analysis of the whole dynamic process, it is confirmed that the proposed model obeys the first and second laws of thermodynamics. The optimal solution for T23 and γAC are calculated to be 259.6896 K and 1.2335, respectively. The Pareto frontier of multi-objective optimization of energy and exergy efficiencies are conducted. Energy efficiency of proposed CCR system is higher than that of CAES system by at least 32.8 %. The electrical efficiency of proposed CCR system is also higher than that of CAES system. It suggests that the pressure potential energy wasted in the throttle process is well utilized by the piston turbine in CCR system.