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Growing demand for electricity due to economic development contributes to increased greenhouse gas production, especially CO 2. However, emissions can be limited by enhancing the efficiency of primary energy conversion, such as integrating geothermal energy into coal-fired power plants. Therefore, this paper proposes replacing conventional feed-water heaters with geothermal preheaters to create a hybridized system. This study was based on a numerical model validated at a selected Polish power unit. The model was subsequently calibrated for off-design conditions to facilitate partial load analysis. The obtained characteristics outperformed those of the non-hybrid unit, generating over 18 MW of electric power output. Such an improvement could potentially boost the unit's net efficiency by more than 2.6 %. This enhancement is significant as power units typically operate under part load for approximately 90 % of the time, hence the need to evaluate the performance characteristics of hybridized units in those states. Furthermore, the research outlines the potential decrease in the plant's CO 2 emission factor, with reductions reaching up to 6.5 % under off-design conditions. Based on a gap analysis of the existing literature, this paper's comprehensive partial load evaluation serves as a new addition to research on hybridized systems. • An in-depth analysis of feed-water heaters operation is performed. • Turbine performance calculations for both design and off-design states is validated. • The comprehensive study of hybridized systems integrates three major factors. • Hybrid geothermal-fossil power cycle is vital for specific CO 2 emissions reduction. [ABSTRACT FROM AUTHOR]

• A dynamic model for a 300 MW subcritical power plant boiler is developed. • A novel dynamic exergy analysis and assessment model is proposed. • The influence of drum level control on dynamic exergy behavior is evaluate. • The asynchronous responses are discussed in flow and heat transfer processes. • The dynamic exergy analysis reveals exergy destruction rates of heating surfaces. In the era of high penetration of renewable energy sources (RESs), traditional coal-fired power plants are facing increasing requirements of operational flexibility which is limited by the inherent slow dynamics of boiler. To this end, this paper presents a comprehensive dynamic model of the heating surfaces for a 300 MW power plant boiler and analyzes the exergy performance from the perspective of transient responses. Based on the object-oriented modelling language Modelica, the multi-domain first-principal model is developed by unifying the equations of thermal, mechanical, liquid and control components and interfaces. The model accuracy is validated by the field measurements. The model takes into account the multi-scale time constants in terms of the flow and heat transfer processes and drum level control. As an extension to the conventional steady-state thermodynamic analysis, a methodology of dynamic exergy analysis and evaluation is proposed. Dynamic simulation results well describe the initial reverse response of the drum level, i.e., false water level indicator, as a result of which the mass flow rate of feedwater exhibits the oscillatory performance. It is revealed that the step disturbances of flue gas mass flow and feedwater temperature, respectively, renders the temperature responses in different positions being of multi-scale setting-time and magnitudes. The exergy evaluation reveals that the water-wall suffers from the largest dynamic exergy destruction, approximately 8.2 and 8.5 times higher than the superheater and economizer, respectively. Economizer is the most sensitive component to the drum level control performance, whose dynamic exergy performance oscillates significantly. The proposed dynamic modelling and analysis method in this paper lays a solid foundation for the development of dynamic optimal control in power plants. [ABSTRACT FROM AUTHOR]

• The government's clean electricity subsidy and carbon utilization subsidy have pushed the timing of CCS retrofitting significantly forward, but the initial investment subsidy has little impact on it. • Under the cooperation mode of coal-fired power plants and oilfield enterprises, the optimal cost-sharing ratio of the initial investment for coal-fired power plants is about 0.4 to promote both sides to reach cooperation faster. • The carbon tax policy effectively propels the development of CCS-EOR technology. When the carbon tax rises from 30 CNY/t to 120CNY/t, power plants will conduct CCS retrofitting investment two years in advance. Carbon capture and storage with enhanced oil recovery (CCS-EOR) technology plays a crucial role in achieving dual carbon targets in China. And the rapid diffusion of technology requires collaboration among various stakeholders involved in industrial chain of CCS-EOR project and then it will cause conflict of interest among the participants. In order to solve the problem existing in CCS-EOR promotion and propel the rapid deployment of low-carbon technology in China, the paper constructs a tripartite evolutionary game model by incorporating the strategic choices of coal-fired power plants, oilfield enterprises and governments into the framework, explores the respective dynamic evolutionary path of three parties and analyzes the impact of each parameter change on the system evolution results Through the numerical simulation, the paper identifies the optimal evolutionary path to spur the application of CCS-EOR and determine their strategy choices of three involved subjects in the game framework. Based on the sensitivity analysis, results are given as follows: (1) The government's clean electricity subsidy and carbon utilization subsidy have pushed the timing of CCS retrofitting significantly forward, but the initial investment subsidy has little impact on it; (2) Under the cooperation mode of coal-fired power plants and oilfield enterprises, the optimal cost-sharing ratio of the initial investment for coal-fired power plants is about 0.4 to promote both sides to reach cooperation faster. Once it exceeds 0.4, the probability of cooperation between them will be significantly reduced; (3) The carbon tax policy effectively propels the development of CCS-EOR technology. When the carbon tax rises from 30 CNY/t to 120CNY/t, power plants will conduct CCS retrofitting investment two years in advance. [ABSTRACT FROM AUTHOR]

• Phasing out coal-fired power is inevitable, but a deeply complex process from a social-institutional standpoint. • The nature of the coal-fired power transition is comparable to the automotive industry closures observed in Australia's recent industrial past. • This paper draws on just transitions and the transition management analytical frameworks. • Four key insights offer pointers for policymakers to support the transition away from coal-fired power in Australia and globally. Nearly three-quarters of Australia's electricity generation is coal-dependent with fossil fuel-led electricity contributing to over a third of Australia's CO 2 emissions. Climate change imperatives are calling for permanent shifts to these patterns, leading to early closure announcements of several coal-fired power plants across the country. Although the pace and scale of the energy transition are unprecedented, the closure of large-scale industries is not uncommon. The most recent closure in Australia's industrial past that remains vivid in the nation's collective memory was the end of nearly 70 years of automotive manufacturing. Drawing on expert consultations, and applying just transitions and transition management thinking, this paper identifies four key insights from the auto sector closure experience. These offer compelling pointers to guide socio-economic transformations in frontline regions that are likely to face challenging, often deeply personal, impacts resulting from the closure of coal-fired power stations over the coming decades. [ABSTRACT FROM AUTHOR]

With the high proportion of renewable energy connected to the grid, the problem of insufficient flexibility in the power system has emerged. Renewable energy and controllable distributed resources can be aggregated and managed through virtual power plants, reducing the need for flexibility to a certain extent. Although building new energy storage systems can compensate for the lack of flexibility, it requires high initial investment costs. To address this, this paper proposes a lease mechanism for coal-fired units based on the combination of carbon credits and prices, providing the right to use coal-fired units for virtual power plants. Subsequently, different demand response strategies are utilized to control the controllable loads of various users, thereby providing certain controllable resources for the virtual power plant. Additionally, to ensure the optimal decision-making of the virtual power plant operator, a cost model accurately describing the capacity degradation state of the energy storage system is adopted. Moreover, a multi-time scale scheduling strategy of virtual power plant is implemented to fully utilize controllable resources of different time scales, effectively dealing with the power imbalance caused by multiple uncertainties. The results show that utilizing the leasing mechanism of coal-fired units and employing demand response strategies from different users can provide flexibility to the virtual power plant. The accuracy of the capacity degradation model used by the operator significantly impacts the optimality of the scheduling plan. • The scheduling model of VPP consider capacity degradation of ESSs, carbon trading, and DR strategies. • A lease mechanism for coal-fired units based on the combination of carbon credits and prices is proposed. • This paper proposes ISBDR strategies for reduceable loads. • The ESSs capacity degradation model adopted takes into account DOD and SOC. • A multi-time scale scheduling strategy of VPP is adopted to deal with multiple uncertainties. [ABSTRACT FROM AUTHOR]

Currently, tail flues of coal-fired power plants are treated using wet desulfurization process to remove pollutants. But, the treated flue gas has a significant moisture loss and this process also contributes to environmental pollution. Acoustic agglomeration is a non-contact treatment process that can effectively solve the problem of moisture loss in flue gas; however, there are few theoretical and experimental studies on acoustic droplet agglomeration applied to coal-fired power generation. In this paper, an experimental platform for acoustic droplet agglomeration is demonstrated to recover moisture. Further, the effects of important factors such as acoustic frequency, sound pressure level and droplet flow rate on the agglomeration efficiency are investigated. The experimental results show that there are two optimal frequencies exist, namely 500 Hz and 1200 Hz, for the droplets used in this experiment with acoustic droplet agglomeration. A highest efficiency of 58% is achieved at 500 Hz. The acoustic action differs between the 500 Hz and 1200 Hz cases. The analysis suggests that the primary force driving droplet agglomeration at 500 Hz is likely the acoustic flow effect. On the other hand, the main mechanism behind acoustic agglomeration at 1200 Hz could be related to the acoustic wake effect. Sound pressure level is the primary factor affecting droplet agglomeration, and the agglomeration efficiency increases with sound pressure, reaching 96.7% at 150 dB. Furthermore, the agglomeration effect shows a positive correlation with droplet flow rate, while the agglomerated particle size also increases simultaneously. This research provides a new idea for moisture recovery, which could offer valuable insights for implementing acoustic droplet agglomeration and moisture recovery in power plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel coal-fired power plant coupling with waste incineration scheme is proposed. • The PCDD/Fs emission could be suppressed by a three stages controlling method. • The flue gas circulation can also suppress the emission of PCDD/Fs effectively. The production of organic solid waste is increasing as the development of society. However, the investment of waste incineration power plant is very high and the thermal efficiency is very low. At the same time, the load of coal-fired power plant is suppressed due to the carbon neutralization policy. Therefore, using the existed coal-fired power plant to co-process the organic solid waste is a feasible method. In this paper, a coal-fired power plant indirect coupling with waste incineration technology based on flue gas circulation was proposed and studied on a 100 kW pilot-test bench. In this technology, the polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) was reduced by a three stages controlling method, which adopts the blending of multi-source organic wastes, high-temperature decomposition and selective catalytic reduction (SCR) catalyst decomposition, simultaneously. The effects of waste incineration coupling, replacement ratio of coal, and flue gas circulation on the combustion and pollutant emission characteristics of the system were studied. The experimental results indicate that the waste incineration coupling has minor influence on the temperature distribution and the toxicity of fly ash of the coal-fired furnace. The NO, HCl, and PCDD/Fs concentrations of flue gas of coal-fired furnace generally decrease as the replacement ratio of coal increases, while the SO 2 concentration increases. With the help of three stages controlling method or the flue gas circulation, the PCDDFs concentration of the flue gas of coal-fired furnace can be much lower than 0.1 TEQ ng/Nm3. [ABSTRACT FROM AUTHOR]

• Stacked target enhanced autoencoder used to extract the useful features. • Attention mechanism-based long short-term memory used to predict the target output. • Data cleaning strategy used to filter the redundant data. • A three-layer-based attention network is designed to allocate different weights. Accurate and robust measurement of the oxygen content in the flue gas of power plant is significant to optimal the coal combustion process. Conventional hard measurement algorithms have low accuracy, short lifetime and high cost. Therefore, it is urgent to establish a precise and reliable soft measurement model. However, how to extract effective feature representations from complex process data is still the difficult and hot spot in the soft measurement field. The paper develops a novel soft measurement model, which integrates stacked target-enhanced autoencoder (STAE) with attention mechanism-based long short-term memory (ALSTM) in view of the above issues. The data cleaning strategy is firstly designed to filter the redundant data from the original data. Then STAE is developed to extract the useful features, which introduces target output into each autoencoder to ensure the feature representation is output-related and stacks several autoencoder units to learn high-level information. The extracted hierarchical features can not only represent the input data, but also have high correlation with the target output. A three-layer-based attention network is designed to allocate different weights on the different levels' features. Finally, due to the dynamic characteristic of the problem, a LSTM-based prediction network is dexterously designed to learn the potential relation from extracted features to target output, i.e., oxygen content. Numerous real-word data is collected from a 300 MW power plant and extensive experiments are conducted. The maximum prediction errors of A and B are 0.42 and 0.41. The 95.1 % prediction errors of A side are within [−0.2, 0.2], and the 96.2 % prediction errors of B side are within [−0.2, 0.2]. [ABSTRACT FROM AUTHOR]

Accurate measurement of flue gas velocity is of great significance for the safe production, energy saving, and emission reduction of coal-fired power plants. In this paper, a method of flue gas velocimetry based on a hyperbolic chirp-modulating acoustic source was proposed, and its superiority was verified by numerical simulations and field experiments. For an acoustic velocimeter, it is crucial to ensure the accuracy of the acoustic Time-of-Flight (TOF), which directly affects the flue gas velocity measurements. The improvement of the accuracy of estimation of the TOF directly determines the accuracy of the flue gas velocity measurement. Simulation on the different types of acoustic sources at different signal-to-noise ratios (SNRs) was conducted, and the results proved that the hyperbolic chirp signal is more accurate in the measurement of TOF. In the strong noise range of − 10 dB to − 20 dB, the average relative root mean square error (RRMSE) obtained using this hyperbolic chirp modulating acoustic source is 0.60 dB and 0.36 dB lower than obtained using the linear and logarithmic modulating modes, respectively. The average relative error (RE) is approximately 0.87 times that of the linear chirp. Power plant flue field experiments show that the measurement error using this hyperbolic modulating mode is about 0.52 times and 0.74 times that of using linear and logarithmic modulating modes, respectively. In harsh measurement environments with strong noise, the proposed acoustic source modulation scheme can significantly improve the measurement SNR and effectively enhance the accuracy and robustness of flue gas velocimetry. [Display omitted] • The proposed method is a flue gas velocimetry method based on a hyperbolic chirp modulating acoustic source. • This method can be applied to the non-contact measurement of velocity of gaseous media in coal-fired power plants. • The proposed method is able to iomprove the estimation accuracy of acoustic TOF. • The proposed method offers better noise resistance, and reduced attenuation. [ABSTRACT FROM AUTHOR]

CO 2 capture, utilization, and storage (CCUS) are critical technical measures to effectively mitigate the global climate change problem. However, most of the existing research has focused on the capture end and lacks in-depth analysis of subsequent processes such as compression, leading to limitations in the improvement of system economics. Therefore, a novel CCS system for a 300 MW coal-fired power plant was proposed in this paper with two strategies: (1) a CCS system integrating CO 2 refrigeration cycle (CFPP-CCS-CRC); and (2) a CCS co-generation plant integrating CO 2 refrigeration cycle (CHP-CCS-CRC). The proposed systems' performance was comparatively evaluated by applying energy, exergy, and economic (3E) analyses. The results demonstrated that at different CO 2 capture percentages (13.1 %∼72.9 %), the CHP-CCS-CRC system has improved energy utilization efficiency by 1.2 %∼5.6 % and exergy efficiency by 7.7 %∼25.8 %, compared to the conventional CCUS system (CFPP-CCS). In particular, at a percentage of 13.1 %, the combined energy consumption of the CHP-CCS-CRC system was 0.39 GJ/tCO 2 , a 79 % reduction compared to 1.87 GJ/tCO 2 of the CFPP-CCS system, which resulted in a static payback period of less than 2 years. In general, the newly proposed system features more adequate energy utilization, lower operating costs, and higher economic efficiency. [Display omitted] • A novel CCUS system coupled with CO 2 refrigeration were proposed. • The performance of the proposed systems is comparatively evaluated by 3E analysis. • The energy consumption of the proposed CCUS systems is reduced by 29.24 %–79 %. • The exergy efficiency of the proposed CCUS systems is reduced by 7.7 %–25.8 %. • The static payback period for the proposed systems is reduced to less than 2 years. [ABSTRACT FROM AUTHOR]

Conventional assessment methods of albedo measurement, like satellite imagery and on-site single-point measurements, lack the precision to address surface textural variances that can lead to power mismatches in a string of bifacial photovoltaic modules (BF-PV). To overcome this, we propose an innovative solution — an autonomous rover equipped with back-to-back pyranometers on its arm to measure the upward (plane-of-array) and downward (albedo) irradiance of a given surface. Employing an efficient path-planning algorithm, the rover ensures comprehensive spatial albedo data collection, overcoming the limitations of existing methods. The paper details the verification of the proposed methodology, its efficacy, and its importance over traditional approaches. This system enables holistic spatial albedo mapping of large areas, capturing textural/topographical non-uniformity, which is crucial for BF-PV installations. Simulations are conducted at the MBR Solar Park in Dubai, UAE, using albedo values measured and collected by the rover. The simulations involved calculating power output for a string of 20 modules across three cases of spatial albedo variations (0.32–0.38, 0.329–0.330, and 0.12–0.36). In the worst-case scenario (case 3), a power mismatch of 18.7% across the module string and a 4.2 °C temperature mismatch are observed. Cases 1 and 2 showed 4.6% and 0.2% power mismatch losses, respectively. These results underscore the critical role of precise spatial albedo measurements in optimizing installation conditions, emphasizing the need for spatial mapping to enhance energy yield estimates. • Developed a new methodology for spatial albedo mapping using a rover. • Highlighted importance of non-uniform spatial albedo on bifacial PV. • A novel albedo-map of an area of 1 sq. km to visualize topographical variation. • Power mismatch of 18.7% for a string of 20 modules when albedo variation is within 0.12–0.36. • Precise estimate for bifacial PV plant installation. [ABSTRACT FROM AUTHOR]

Ammonia/coal co-firing in coal-fired power plants is an effective way to achieve CO 2 reduction. In this paper, the ammonia/coal co-firing study was carried out in a 45 kW wall-temperature-controlled staged combustion downstream furnace at 1100 °C. Bituminous coal was used as the experimental object to analyze the effects of ammonia injected at the main combustion zone, reduction zone, with the burnout air, and at the burnout zone on NO release characteristics at different ammonia co-firing ratios. To ascertain the significant reaction of NO production in the ammonia/coal co-firing, chemical reaction kinetics calculations were performed. When co-firing ratios of 10∼30%, the NO emission concentration is lower by the ammonia injection position of the main combustion zone which is 275–346 mg/m3. When co-firing ratios reach to 40% and 50%, NO releases are lower by the ammonia injection position of burnout zone which is 511–574 mg/m3. In addition to exhibiting a greater capacity to decrease NO in environments with low oxygen concentrations and high NO concentrations, ammonia can also, under specific circumstances, have a significant capacity to decrease NO in environments with high oxygen concentrations. Based on the experimental results and chemical kinetic calculations, the NO release pattern and mechanism during ammonia-coal co-combustion with different ammonia injection methods under air staged combustion were investigated, which provides a technically feasible solution to reduce CO 2 and NOx emissions from coal-fired power plants. • Conducted NH 3 /coal co-firing tests in a one-dimensional down-fired furnace. • Ammonia injection methods is analysed in detail. • NH 3 injected in main combustion zone is better with low co-firing ratio. • The fuel-lean/rich atmosphere transformation promotes NO reduction ability of NH 3. [ABSTRACT FROM AUTHOR]

• The NO emission characteristics of co-combustion of pulverized coal and NH 3 at O 2 /N 2 and O 2 /CO 2 atmospheres were studied. • The effects of temperature, NH 3 blending ratio and combustion atmosphere on NO emission during co-combustion were investigated. • The molecular dynamics simulation was used to study the migration pathways of N in NH 3. The use of ammonia as a co-combustion fuel instead of fossil fuel combustion is an important way to reduce carbon emissions from coal-fired power plants. This paper investigates the NO emission characteristics of coal/NH 3 co-combustion at O 2 /N 2 and O 2 /CO 2 atmospheres through experiments and molecular dynamics studies. The results demonstrate that increasing the combustion temperature enhances the formation of NO with the NH 3 blending ratio is 0–60 %. When coal and NH 3 are burned together, the emission of NO is lower at O 2 /CO 2 atmosphere compared to that at O 2 /N 2 atmosphere. Reactive force field molecular dynamics (ReaxFF MD) simulation results show that the effect of high concentration of CO 2 on nitrogen conversion is mainly related to temperature. When the temperature is low, the physical characteristics of CO 2 with large specific heat capacity inhibits the conversion of NH 3 to NO. However, at high temperature, CO 2 participates in the reaction in large amounts, which increases the number of OH radicals in the combustion process and promotes the conversion of NH 3 to NO. The results show that with the increase of combustion temperature, the conversion of nitrogen-containing intermediates to NO is promoted. Furthermore, the reactive molecular dynamics simulation revealed the transfer pathway of N atoms in NH 3 during co-combustion process at two atmospheres. [ABSTRACT FROM AUTHOR]

• Studied the effects of NH 3 cofiring ratio, injection mode and OFA on NO x emission. • NO x exhibited a variety of trends under different injection modes and OFA rates. • Revealed all the different NO x trends are governed by the same NO mechanism. • Found air-staging is not always effective in the NO x reduction of NH 3 cofiring. Ammonia (NH 3) cofiring is a promising approach to reduce the CO 2 emissions from coal-fired power plants. However, the potential drastic increase of NO x emissions may inhibit the wide implementation of NH 3 cofiring. To explore the potential NO x control strategies, the effects of NH 3 cofiring ratio (R N H 3 ), NH 3 injection mode and overfire air (OFA) rates on the NO x emission characteristics of NH 3 /coal cofiring are studied in a test furnace that allow for flexible control of the injection positions and combustion environment of NH 3. The results show that when NH 3 is injected with coal stream (top mixing mode), the NO x emissions increase and then decrease with the increase of R N H 3 under all OFA rates. However, when NH 3 is fed through the side port of furnace separately (side mixing mode), the NO x emissions exhibit distinct trends under different OFA rates. Under lower OFA rates, the NO x emissions show monotonical decrease with the increase of R N H 3 , while under higher OFA rates the NO x emissions first decrease and then increase with the increase of R N H 3 . Consequently, higher OFA rates could produce higher NO x emissions than lower OFA rates. This indicates that air-staging is not always effective in the NO x reduction of NH 3 cofiring. Thus, although the side mixing mode of NH 3 cofiring exhibits overall better performance in NO x control, caution is needed to accommodate the OFA rate with NH 3 cofiring ratio. Although a variety of trends of NO x emissions were observed in this study, the results demonstrate that all these trends are in fact governed by the same mechanism – the competition between the NO-formation and NO-reduction reactions of NH 3 in the varying O 2 environment in the furnace. By creating appropriate O 2 environment in the furnace, the NO x emissions of NH 3 /coal cofiring could be substantially lower than that of pure coal combustion. The findings of these paper are instrumental in the design and operation of NH 3 cofiring system in full scale coal-fired boilers to achieve effective NO x control. [ABSTRACT FROM AUTHOR]

• Amine emissions and their volatile degradation products from carbon capture pilot plant. • Long-term measurement of purity of the CO 2 produced from the desorber. • Process parameters for treating 200 m3/h of flue gas from coal-fired boiler. • Gas analysis from different sections of the absorber using FTIR analyzer. • Evaluation of the pretreatment section, which cleans the flue gas entering the CO 2 absorber. Carbon dioxide reduction by amine absorption is considered the most technologically advanced method. This method is particularly recommended for gases with low CO 2 concentrations, such as flue gases. On the other hand, the use of amine absorption solutions can contribute to the emission of harmful chemicals into the atmosphere. This paper presents the emission of amines and their degradation products from a CO 2 capture pilot plant treating a slipstream (approximately 200 m3 N /h) of flue gas from a pulverized coal-fired boiler. The studies were conducted during a 2-week research campaign at the Łaziska Power Plant in Poland. An aqueous blend of 2-amino-2-methyl-1-propanol (25 % AMP) with piperazine (9 % PZ) was used as the absorption liquid. Among others, ammonia (12 ppmv), acetone (1 ppmv) and AMP (20 ppmv) were found to be the main contaminants in the clean gas (from the absorber). However, it should be noted that only single water wash section was used. The composition of the CO 2 produced (from the desorber) was also measured. It was shown that the main pollutants were water vapor (3–4 % vol.), ammonia (2–6 ppmv), nitrogen oxide, formaldehyde, and formic acid (sum, up to 10 ppmv). Traces of acetone were also detected. The composition of this gas is of practical importance for the planned management of the captured CO 2 stream. During the studies, the CO 2 capture efficiency was in the range of 86.6 %-94.6 %. The average specific reboiler heat duty (gross) was 3.24 MJ/kg of removed CO 2. [ABSTRACT FROM AUTHOR]

Improving the peaking capacity of coal-fired units is imperative to ensure the stability of the power grid, thus facilitating the grid integration and popularization of large-scale renewable energy. To address this issue, this paper introduces a new concept that combines molten salt energy storage with coal-fired power plants. The proposed design consists of extracting a portion of steam from the turbine side and adjusting the extracted steam mass flow rate by adjusting the valve opening to improve the dynamic characteristics of a coal-fired power plant in terms of both increasing the peaking depth and peaking speed. A coal-fired boiler with integrated thermal energy storage was dynamically modeled using Dymola and its accuracy was verified. The results show that the highest equivalent round-trip efficiency is achieved by extracting from the main steam and discharging into the feedwater during charging process and from reheater1 and discharging into the feedwater during discharging process; The peaking potential during charging and discharging is 12.83 % P e and 6.86 % P e respectively, with maximum peaking rates of 9.27 % P e /min and 5.11 % P e /min respectively, and the optimal peaking method is also proposed according to the different peaking situations. The total cost of equipment and materials to retrofit the conventional coal-fired units was 19,948,193 USD and the levelized cost of delivery was 151.29 USD/MWh. • Coal-fired power plant systems incorporating molten salt energy storage. • Dynamic characteristics and economic analysis of coal-fired power plants. • A peaking potential of 12.83 % P e during charging process and 6.86 % P e during discharging process. • A theoretical maximum peaking rate of 9.27 % P e /min during charging process and 5.11 % P e /min during discharging process. • LCOD is determined to be 151.29 USD/MWh. [ABSTRACT FROM AUTHOR]

Steam system plays a crucial role in industrial energy usage. Steam generation in the industry domain is transferring from coal-fired or gas-fired plant/boiler to green-electricity steamer for net-zero purpose. The increasing coupling of the electricity-steam energy system in the industry domain, called electricity-steam coupled industrial energy system (ES-IES), brings enormous challenges to the system day-ahead operation optimization due to the uncertainties of renewable generation and the nonlinearities of the system mathematical model. Therefore, this paper introduces the steam accumulator (SA) into the steam system to mitigate the renewable fluctuations, proposes an isothermal linearization method of the steam flow model, and optimizes the operation based on an interactive iteration scheme between optimization and simulation for the global optimum and a balance between accuracy and speed. Results show that considering the storage characteristics of SA and the complementary coordination of electricity and steam through coupling equipment can significantly optimize the operation of ES-IES with an increase in the renewable energy consumption rate by 23.81 % and a decrease in the total operating cost by 11.39 %. The static payback period for the investment of EB and SA is 7 years, indicating a favorable application prospect. • Linearization methods of steam flow model are used for global optimum. • Equivalent energy storage model of steam accumulator is proposed for optimization. • An interactive iteration scheme between optimization and simulation is presented. • Economic and efficiency performance of the electricity-steam coupled system is evaluated. [ABSTRACT FROM AUTHOR]

Large-scale distributed renewable energy sources as well as emerging controllable loads such as electric vehicles connected to the distribution grids have posed challenges to the efficient management of these distributed energy resources. Promoting energy-sharing of distributed energy resources through economic incentives is a cost-effective and equitable solution to the challenge. This paper proposes a two-stage transactive energy control mechanism by the virtual power plant (VPP) for energy-sharing of multiple prosumers. Firstly, a VPP internal price mechanism based on the supply-demand ratio of prosumers in the energy-sharing alliance is proposed. Then, a two-stage economic optimization model is developed. Trading prices between VPP and prosumers are established in the first stage, and prosumers make operating plans based on those prices in the second stage. Then, considering that prosumers and VPP are independent stakeholders, a decentralized optimization algorithm based on the analytical target cascading method is developed. The upper-level VPP coordinates the energy-sharing alliance and sets the transaction price following the overall supply and demand ratio. Lower-level prosumers independently make decisions and feedback on the trading power of the VPP. Then, iterative calculations provide a distributed and independent solution. Finally, the case study verifies that the proposed energy-sharing model can reduce the operating cost of prosumers by 14.29 %. Moreover, prosumer privacy protection is achieved by the analytical target cascading-based distributed model at a cost of less than 1.5 % accuracy. [ABSTRACT FROM AUTHOR]

The paper undertakes a novel study that aims to analyze the performance characteristics of ten monocrystalline or polycrystalline silicon modules employing different emerging technologies in waters environment. In this work, monitoring data were collected over a duration of one year using a multi-technology empirical platform within a floating photovoltaic power plant. The energy performance of different module technologies was evaluated using multiple performance metrics such as array yield, performance ratio, capacity factor, efficiency and energy density. By considering environmental variables such as irradiance, ambient temperature, and water temperature, the thermal behavior of photovoltaic modules under water surface deployment conditions is revealed. Furthermore, the multiple variable coupling analysis was conducted to determine the correlation between the performance metrics of various technology type modules and meteorological variables in waters environment. The results indicate that the energy performance and reliability of monocrystalline silicon modules using double-glass double-sided P-type PERC technology is superior to other technologies in waters environment, and the performance ratio and capacity factor reach 88.95 % and 15.04 %, respectively. The heterojunction with intrinsic thin-layer (HIT) technology module exhibits better thermal stability and holds an advantage in the deployment of limited water surface areas due to its higher energy density. Moreover, the performance ratio of floating photovoltaic systems shows a weak correlation with irradiance, and is more significantly affected by the negative correlation of ambient temperature than water temperature. [ABSTRACT FROM AUTHOR]

To construct a new energy system during the low-carbon transition, renewable energy sources (RESs) are increasingly being installed on a large scale worldwide which require thermal power units to operate at low loads and respond quickly to compensate for frequency fluctuations of the power grid during deep peak shaving and frequent load changes. While coal-fired thermal power plants operate under the deep-peak shaving process, low-frequency oscillation (LFO) accidents from the generation side have occurred constantly. According to our investigation, the reasons are the overlook of the nonlinearity of control valves is obviously highlighted under low load, and the preset parameters of the original control device can not match the flow characteristics, which may seriously cause a recurrence of LFOs. This paper focuses on generation-side LFO caused by the prime mover and its governor under all operating conditions constructing a novel nonlinear model and designing an oscillation feature observation matrix to identify the LFO modes, and a hierarchy feature-state observation classification method preventing LFO on the generation side is proposed. The results show that the proposed method can suppress the LFOs ahead, and this approach can weaken the oscillation amplitude by 85% and reduce the oscillation duration by 30 s. • Retrofit the small frequency offset compensation and the valve flow module, simulate dynamic characteristics accuracy. • Propose an oscillation ranking method to evaluate the security level of power oscillation and verify its reliability. • Design the hierarchical prevention control strategy for LFO in stages and validate the effectiveness of thecontrol strategy. [ABSTRACT FROM AUTHOR]

• Methodology for assessing the operational flexibility of Virtual Power Plants. • Methodology to facilitate the integration of renewable energies into the power system. • Graphical representation of operational flexibility of distributed energy resources. • Assessment of the available flexibility to facilitate decision-making under uncertainty. • Participation of Virtual Power Plants in the ancillary services and power reserve offer. Distributed energy resources (DERs) are elements that actively participate in the supply of renewable energy and contribute to the decarbonization of the power system. However, they lack two factors necessary to take advantage of their operational flexibility: observability and controllability. In this sense, Virtual Power Plants (VPPs) are a feasible alternative to provide the necessary requirements for the optimal management of a set of distributed units. Therefore, knowledge of the technical and energy characteristics of each unit that makes up the VPP is a necessary condition for the effective integration of DERs into the power system. This paper proposes a methodology to graphically represent, quantify and exploit the aggregate operational flexibility of a set of units. The proposed methodology is based on five metrics related to active and reactive power, which serve as a tool to facilitate the VPP Operator's decision-making under uncertainty. Consequently, achieving the coordinated operation of several distributed units makes it possible to achieve common objectives. For instance, frequency and voltage regulation, compliance with a planned power curve, or dealing with the variability of renewable energies. The proposal is applied to a theoretical case study and through real operational tests between a hydroelectric unit and a photovoltaic plant. Finally, it is shown that the results obtained are a useful tool in real-time. [ABSTRACT FROM AUTHOR]