Load Change Rate Research Articles

Study on control strategies of the MW-scale supercritical CO2 recompression Brayton cycle for lead-cooled fast reactor

The supercritical CO2 (sCO2) Brayton cycle for the lead-cooled fast reactor (LFR) is an ideal power generation system for the distributed energy supply in remote islands. To figure out the optimal operating modes of the MW-scale sCO2 LFR unit in different load demands, this work performs a dynamic simulation based on the developed control modules. A parametric analysis is conducted about the effects of rotational speed, split ratio, and main gas temperature on the dynamic characteristics. Control strategies are further studied based on the thermodynamic performance and safety under four variable temperature load regulation modes and three fixed temperature rapid load regulation modes. Results show that the tracking αopt mode has the highest average net efficiency (ηnetav) of 19.13 %. The tracking αsafe mode allows compressors to operate in the safest range by sacrificing a little ηnetav. Excellent load change rates are revealed by using the main circuit regulating valve control mode and the turbine bypass control mode, with −12.48 %Pe/min & 11.92 %Pe/min, and −8.25 %Pe/min & 9.70 %Pe/min, respectively. Though the load change rate of the RS control mode is −3.96 %Pe/min & 3.47 %Pe/min, its ηnetav is higher. Our work guides the efficient, flexible, and safe operation of the sCO2 LFR unit.

Heat transport and load response characteristics of a molten salt solar tower power station engaged in peak regulation

Power system flexibility can be improved effectively, if the advantages of the peak shaving ability of molten salt solar tower power (STP) plant can be developed and utilized. In this paper, the heat transport and load response characteristics of the molten salt STP plant in the regulation process are studied, aiming at serving the development of the regulation method in the rapid peak regulation process. The steam generation system and turbine system models of a 50 MW STP station are established. Two load regulation methods and operation modes are used to investigate the inertia and delay effects of heat transfer and evaporation, as well as load response characteristics during the actual regulation operation, including steam generation system following (SF), turbine following (TF), constant pressure operation (CP), and sliding pressure operation (SP). The results show that when the plant load is reduced by 10% Pe at the rate of 3% Pe/min, the heat transfer of salt/water and the evaporation process of water in the whole regulation process have a 250 s delay compared with the load. The larger heat storage characteristics of the plant help to improve the load response speed. The load response speed of the plant is faster in SF mode. TF mode is beneficial to the safe operation of the plant. Considering the operational safety of thick-wall component, the recommended running mode is the collocation of SF and SP mode, TF and CP mode. The results show that the load change rate of 10% Pe/min is permittable under TF and CP modes. The conclusion of this paper lays a foundation for the formulation of a peak regulation strategy for molten salt STPs.

Investigation on the dynamic characteristics under load regulation in CFB boiler with whole loop model

CFB boilers face an increasing significance for load change rate in China. However, there is currently a lack of mechanistic understanding on limitation on fast peak shaving. Based on the mass and energy balance in the full loop, this paper conducts a dynamic model to describe the coupling effect of gas–solid two-phase flow, heat transfer, and combustion processes under load regulation conditions. In particular, the material throughput pattern of cyclone and standpipe are systemically described. Finally, the model was validated by field test data in a 135 MW commercial CFB boiler. On this basis, the impact of factors such as the draining ash strategy and adding/discharging circulating ash on the load regulation characteristics of the boiler were deeply explored, and a comprehensive optimization solution was proposed. The results showed that the boiler’s ramp could be maximized to about 4 %/min after adopting this solution.

Analyzing activity and injury risk in elite curling athletes: seven workload monitoring metrics from session-RPE.

The study aimed to compare the differences in the performance of seven session-rating of perceived exertion (RPE)-derived metrics (coupled and uncoupled acute: chronic workload ratio (ACWR), weekly ratio of workload change, monotony, standard deviation of weekly workload change, exponentially weighted moving average (EWMA), and robust exponential decreasing index (REDI)) in classifying the performance of an injury prediction model after taking into account the time series (no latency, 5-day latency, and 10-day latency). The study documented the RPE of eight curlers in their daily training routine for 211 days prior to the Olympic Games. Seven Session-RPE (sRPE)-derived metrics were used to build models at three time series nodes using logistic regression and multilayer perceptron. Receiver operating characteristic plots were plotted to evaluate the model's performance. Among the seven sRPE-derived metrics multilayer perceptron models, the model without time delay (same-day load corresponding to same-day injury) exhibited the highest average classification performance (86.5%, AUC = 0.773). EMWA and REDI demonstrated the best classification performance (84.4%, p < 0.001). Notably, EMWA achieved the highest classifying accuracy in the no-delay time series (90.0%, AUC = 0.899), followed by the weekly load change rate under the 5-day delay time series (88.9%, AUC = 0.841). EWMA without delay is a more sensitive indicator for detecting injury risk.

Experimental study on the flexible peak shaving with pulverized coal self-preheating technology under load variability

The integration of renewable energy sources into power grids has led to power fluctuations, necessitating coal-fired power units to provide flexible peak shaving. The pulverized coal self-preheating technology can potentially provide broad-load regulation and rapidly respond to load changes. In this study, the impact of the self-preheating technology on fuel preheating modification, combustion characteristics, and NOx emissions are investigated. Load-stabilization bases are proposed based on preheating temperature, preheated coal gas composition, combustion temperature, and flue gas emissions. Load change rates are calculated using these bases to character the load response. The results demonstrate that the preheated fuel has similar properties as the highly reactive gaseous fuel and exhibits excellent ignition and combustion performances at 25 % load. Preheating treatment improves combustion efficiency, and burnout ratio and reduces NOx emissions. The NOx concentration approaches the ultra-low emission standard at 50 % load. Four load-stabilization bases, covering the preheating and combustion sides, comprehensively characterize the load response performance. The rates based on preheating indicators and combustion indicators maximize to 3.30 %/minute and 2.71 %/minute, respectively. The load change rate in the ramp-up phase is higher than that in the ramp-down phase, which is related to the effective internal heat storage carrier and external thermal insulation conditions. The driving force formed by high load step ranges and the deviation from the full load capacity are conducive to increasing the load change rates.

Design approach of thrust-matched rotor for basin model tests of floating straight-bladed vertical axis wind turbines

Rotor redesign approaches have been widely proposed to solve the thrust mismatch issue caused by scaling effects for basin model tests of horizontal axis floating wind turbines (FWTs). However, limited basin model tests utilized the thrust-matched rotor (TMR) to accurately evaluate the aerodynamic loads applying to the vertical axis FWTs. This paper described the detailed design approach of the TMR of floating straight-bladed vertical axis wind turbines (VAWTs) with a rated power of 5.3 MW. First, the AG455 airfoil was selected to replace the NACA0018 airfoil. AG455 airfoil can show a larger lift coefficient and a smaller drag coefficient at low Reynolds number. On this basis, the load distribution match algorithm was used to assign the blade pitch angle and chord length at each section of the blade. This method takes the spanwise load and load change rate of model-scaled blade and full-scaled blade as the constraint conditions. By adopting this method, the rotor thrust can be tailored to match the prototype values across a wide range of tip speed ratios. This design approach proves advantageous in assessing the aerodynamic performance of VAWTs under varying inflow wind speeds and unsteady wind conditions. The redesigned TMR model under low Reynolds number can meet Froude similarity criterion, which is helpful to improve the accuracy of vertical axis FWT model tests in the wave basin.

Dynamic process simulation of a 780 MW combined cycle power plant during shutdown procedure

The share of variable renewables in power generation is increasing due to the push to reduce emissions, and the flexibility of conventional power plants has become a major concern. There are many ways to increase the flexibility of existing power plants and implement a more flexible system for the future, such as a fast start-up procedure and higher load change rates. In this study, a 2D dynamic process simulation model of a reference combined cycle power plant is presented to increase the flexibility of cyclic operation by investigating, for the first time in the literature, the shutdown procedure using APROS software. The 780 MWel Tambak Lorok reference combined cycle power plant consists of the GE 9HA.02 heavy-duty gas turbine and a three-stage horizontal heat recovery steam generator with reheat. Several steps were considered to improve the accuracy of the developed dynamic process simulation model, including varying the steam leakage to the atmosphere to control how much thermal energy remains in the heat recovery steam generator, changing the shape loss coefficients of the tubes to achieve higher or lower recirculation, and decoupling the reheater and the intermediate pressure drum. The developed model is validated with real data from three different combined cycle power plants in different countries with various capacities. The comparison shows that the developed dynamic simulation model can accurately represent the real behaviour of natural convection in the heat recovery steam generator. The main outcome was to provide detailed information on the shutdown procedure of large-scale combined cycle power plants, addressing the aspect of the development of new start-up strategies to reduce the time required for the start-up procedure.

Study on the heat transfer of a concrete wall outfitted with phase change materials

This paper tested and simulated the thermal performance of a concrete wall outfitted with Phase change materials (PCMs) under 5 climate conditions in China. The PCMs were encapsulated in high-density polyethylene spherical shells in the concrete to form a PCMs-concrete layer. The daily thermal load change rate through the wall when the PCMs-concrete layer was placed in different positions in five typical climate regions in China were studied. The results show that to make the best use of the PCMs in summer, the phase transition temperature is suggested to be between the outer and inner surface temperatures. For the cases when the outer and inner surface temperatures are higher than the phase transition temperature, the PCMs should be installed in the middle of the wall; To make the best use of the PCMs in winter, the location of PCM should be adjusted according to the range of ambient temperature, when the ambient air is warm enough, the PCMs layer should be installed near to the inner surface, when the ambient air is tepid, the PCMs layer should be installed near to the outer surface, when the ambient air is cold, results do not suggest using PCMs.

A static voltage stability index based on P-V curve for the medium-voltage distribution network with distributed PV

With the rapid increase of distributed photovoltaic (DPV) generations, the static voltage stability (SVS) of distribution network (DN) is faced with more and more challenges. Considering the characteristics of DPV and the network structure, an appropriate static voltage stability index (SVSI) in the medium-voltage DN with DPV is studied in this paper. In terms of the limitation of the traditional SVSI that only reflects the load change, based on P-V curve, a novel voltage change rate - network load change rate index (M-index) is proposed. The M-index considers the impacts of double changes in DPV power output and load level. The model of classic 33-node network with a DPV source is established to investigate the proposed M-index. By changing the DPV penetration percentage and the DPV access point, and comparing with the existing Load-index, the validity and superiority of M-index is verified. Comparing with the traditional SVSI, the M-index is more propitious to evaluate the SVS for the medium-voltage DN with DPV.

Diffuse pollutant load predictions in areas that implement the total maximum daily load due to climate change

Total maximum daily load (TMDL), which is implemented for water quality management in a watershed, necessitates the use of a watershed model to predict the load. However, such a model consumes a lot of time and effort until the results are simulated. Therefore, the present study aimed to compare and evaluate load changes following the revision of the land-based diffuse pollutant unit load values, which are used to calculate the diffuse pollutant discharge loads in the total maximum daily load (TMDL) guidelines established for TMDL control by watersheds in South Korea, using the Natural Resources Conservation Service (NRCS) method. When the revised unit load was used, the loads were reduced by an average of 56.8% compared with the prior unit load. The descending order of load change rate was biochemical oxygen demand (BOD) > total phosphorus (TP) > total nitrogen (TN). Although the difference in load discharge trends between the Representative Concentration Pathway (RCP) 2.6 and RCP8.5 scenarios was insignificant, the load discharge under the worst scenario (RCP8.5) may increase. When the future period was split into 30-year increments, the load of precipitation and diffuse pollutants increased in the intermediate future (2041–2070). This study examined how the management ratio of diffuse pollutants in a watershed changes when the legal standard value of institutionally managed diffuse pollutants changes. The findings of this study provide useful information for the efficient management of present and future diffuse pollutants.

Sense of purpose in life and allostatic load in two longitudinal cohorts

ObjectiveSense of purpose in life has been linked with better physical health, longevity, and reduced risk for disability and dementia, but the mechanisms linking sense of purpose with diverse health outcomes are unclear. Sense of purpose may promote better physiological regulation in response to stressors and health challenges, leading to lower allostatic load and disease risk over time. The current study examined the association between sense of purpose in life and allostatic load over time in adults over age 50. MethodsData from the nationally representative US Health and Retirement Study (HRS) and English Longitudinal Study of Ageing (ELSA) were used to examine associations between sense of purpose and allostatic load across 8 and 12 years of follow-up, respectively. Blood-based and anthropometric biomarkers were collected at four-year intervals and used to compute allostatic load scores based on clinical cut-off values representing low, moderate, and high risk. ResultsPopulation-weighted multilevel models revealed that sense of purpose in life was associated with lower overall levels of allostatic load in HRS, but not in ELSA after adjusting for relevant covariates. Sense of purpose in life did not predict rate of change in allostatic load in either sample. ConclusionsThe present investigation supports sense of purpose predicting preserved differentiation of allostatic regulation, with more purposeful individuals demonstrating consistently lower allostatic load over time. Persistent differences in allostatic burden may account for divergent health trajectories between individuals low and high in sense of purpose.

A wastewater-based risk index for SARS-CoV-2 infections among three cities on the Canadian Prairie

Wastewater surveillance (WWS) is useful to better understand the spreading of coronavirus disease 2019 (COVID-19) in communities, which can help design and implement suitable mitigation measures. The main objective of this study was to develop the Wastewater Viral Load Risk Index (WWVLRI) for three Saskatchewan cities to offer a simple metric to interpret WWS. The index was developed by considering relationships between reproduction number, clinical data, daily per capita concentrations of virus particles in wastewater, and weekly viral load change rate. Trends of daily per capita concentrations of SARS-CoV-2 in wastewater for Saskatoon, Prince Albert, and North Battleford were similar during the pandemic, suggesting that per capita viral load can be useful to quantitatively compare wastewater signals among cities and develop an effective and comprehensible WWVLRI. The effective reproduction number (Rt) and the daily per capita efficiency adjusted viral load thresholds of 85 × 106 and 200 × 106 N2 gene counts (gc)/population day (pd) were determined. These values with rates of change were used to categorize the potential for COVID-19 outbreaks and subsequent declines. The weekly average was considered ‘low risk’ when the per capita viral load was 85 × 106 N2 gc/pd. A ‘medium risk’ occurs when the per capita copies were between 85 × 106 and 200 × 106 N2 gc/pd. with a rate of change <100 %. The start of an outbreak is indicated by a ‘medium-high’ risk classification when the week-over-week rate of change was >100 %, and the absolute magnitude of concentrations of viral particles was >85 × 106 N2 gc/pd. Lastly, a ‘high risk’ occurs when the viral load exceeds 200 × 106 N2 gc/pd. This methodology provides a valuable resource for decision-makers and health authorities, specifically given the limitation of COVID-19 surveillance based on clinical data.

Experimental Investigation of Oil Transport during Low Load to High Load Transient in Internal Combustion Engines

Reducing the Lubricating Oil Consumption (LOC) has been a critical focus for engine manufacturers. LOC not only depends on engine operating condition but also the history of the operating condition variations. This work seeks to understand the oil transport in the ring pack during the low load to high load transient through experimental investigations. An optical engine with 2D Laser Induced Fluorescence (2D-LIF) technique, equipped with a modern low-tension Three-Piece Oil Control Ring (TPOCR), was applied to investigate the oil transport in the ring pack. It was found that, after the engine stayed under the blowby separation line long enough, a sudden increase to high load can result in a huge increase of oil ejection to the liner from the top ring groove in the expansion strokes. The mechanism behind it is that, when the load is increased, the oil accumulated inside the top ring groove during the low load condition is pushed out by the gas flow after the peak cylinder pressure is reached. Different combinations of load, speed, rate of change in load and time duration at low load were tested to examine their influence on this leakage mechanism. An operation with a gradual increase of engine load was found to be able to reduce the amount of oil leaked to the liner by releasing more oil to the second land. These findings can help the effort to reduce the oil emission (OE) generated from Spark Ignited (SI) engines equipped with TPOCR in the real-world transient driving conditions as well as the emission tests.

A flexible hydrogen-electricity coproduction system through the decoupling of units with different dynamic characteristics

Regarding the carbon neutrality target, the proportion of renewable energy in global energy sources is predicted to increase to 50% by 2050, and the increment in penetration requires fossil fuel power plants to play a key role in grid peak regulation. The integrated gasification combined cycle (IGCC) is a promising peak-regulating method for power grids. However, due to the strong coupling between units, the flexibility of gas turbines cannot be fully utilized in response to power demand. This paper proposed a novel polygeneration system integrating syngas storage, hydrogen production, and gas turbines for power. Through syngas storage, the dynamic characteristic of each unit can be decoupled to take advantage of the flexibility of the gas turbine. Compared to the general IGCC system, the load change rate of the new system could be increased from 0.5%/min to 3-5%/min without altering the dynamic characteristics of the original equipment. The design capacity of the syngas storage tank could be reduced by decreasing the ramp rate of the power generation unit or increasing the load change rate of the gasification and hydrogen production units. For the new 300-MW system, the required syngas storage tank capacity reached only approximately 1872 m3 under storage conditions of 35 bar and 25 °C. Furthermore, the investment in the syngas storage tank only accounted for approximately 6.6% of the total investment cost. In general, the novel system can be more flexibly operated under variable loads with low carbon emissions, which can help to increase the penetration of renewable energy in the power grid.

Design of Energy Storage for Assisting Extraction Condensing Unit to Peak Regulation and Frequency Modulation

Abstract Coupling energy storage system is one of the potential ways to improve the peak regulation and frequency modulation performance for the existing combined heat power plant. Based on the characteristics of energy storage types, achieving the accurate parameter design for multiple energy storage has been a necessary step to coordinate regulation. In this work, heat storage tank for peak regulation and flywheel energy storage for frequency modulation have been carried out, including the parameters design and performance evaluation for their charging (or discharging) rate and capacity, and the collaborative optimization of dual energy storage systems has been realized. First, the effects of increasing peak depth, load change rate (frequency modulation) range, and energy storage parameters are further analyzed. It is worth noting that the power curves of regional thermal and electrical loads would be adjusted according to the set requirements. Results showed that, the set rate of charge and discharge as well as the capacity of energy storage is conducive to improving the peak regulation depth of the system, and the peak regulation depth would reach its limit at 96.35 MW and 40.83 MWh in the calculation cases, respectively. On this basis, the cooperative regulation of dual energy storage can further increase the capability of peak regulation and frequency modulation. The extreme point is that when the charge and discharge rates are both 3 MW, and meanwhile the peak clipping coefficient, a self-defined parameter, reaches 22.34 MW. Furthermore, an example calculation is carried out to verify the reliability of the design method of energy storage parameter. The specific parameters set include the charging and discharging rate of energy storage tank equipment is 61.67 MW, and its capacity is 10.64 MWh, and the charging and discharging rate of flywheel energy storage equipment is 3 MW. The example results confirmed that there was only a very small error between the set results and the calculation results. Finally, the thermal-electric load region has been drawn to contrast the key roles of dual energy storage systems, which indicates that the heat storage tank can be used for peak regulation and flywheel energy storage for frequency modulation. Overall, the parameter design method for dual energy storage can meet the engineering requirements and provide a new direction for the subsequent parameter design of thermal power unit coupled energy storage system.

SENSE OF PURPOSE IN LIFE AND ALLOSTATIC BURDEN IN TWO LONGITUDINAL COHORTS

Abstract Sense of purpose in life has been linked with better physical health, longevity, and reduced risk for disability and dementia, but the mechanisms linking purposefulness with diverse health outcomes is unclear. Chronic activation and dysregulation of neural, immune, and other bodily systems, known as allostatic load, may contribute to these underlying mechanisms. Specifically, sense of purpose may promote better physiological regulation in response to stressors and health challenges, leading to lower allostatic burden and disease risk over time. Data from the nationally representative US Health and Retirement Study (HRS) and English Longitudinal Study on Ageing (ELSA) (Total N=5846; Mean Age=67.24, SD=10.68, 59.08% female) were used to examine associations between sense of purpose and repeated assessments of allostatic load across 8 and 12 years of follow-up. Allostatic load scores were constructed from 12 blood-based and anthropometric biomarkers of cardiovascular, metabolic, immune, and lung function, with higher scores representing higher allostatic burden. Population-weighted multilevel models revealed that sense of purpose in life was associated with lower overall levels of allostatic load in HRS (b = -0.22, 95% CI: -0.27,-0.17) and in ELSA (b = -0.19, 95% CI: -0.35,-0.03). Sense of purpose in life did not predict rate of change in allostatic load in either sample. Associations with sense of purpose were highest among cardiovascular and immune biomarkers, suggesting that preservation of these bodily systems may underlie associations between purposefulness and reduced risk for chronic health conditions. Discussion will focus on biological and behavioral pathways connecting sense of purpose in life and health.

A day-ahead industrial load forecasting model using load change rate features and combining FA-ELM and the AdaBoost algorithm

Industrial customers consume a large part of the total electricity demand. In the operation of industrial energy systems, accurate prediction of electric loads is a prerequisite to help industrial users adjust their electric load dispatch and improve energy efficiency. Therefore, this paper proposes a day-ahead industrial load forecasting model employing load change rate features and combining the firefly algorithm to optimize the extreme learning machine and adaptive boosting algorithm (LCR-AdaBoost-FA-ELM). The industrial load is mainly influenced by the power users’ production schedules, making its forecasting laws mainly analyzed by the changing laws of the load data itself. Given this, the rate of load change feature is introduced to form a candidate feature set with variables such as the date and lag load. In order to decrease the number of parameters required to train the model, the Spearman correlation coefficient is used to select high-quality input features and eliminate variables that are weakly associated with electricity consumption. The basic algorithm of the prediction model is the ELM, based on which the FA is used to optimize its weights and biases. Finally, the ensemble learning concept is introduced to learn to combine multiple FA-ELM weak predictors by AdaBoost to correct the prediction errors. In this paper, the proposed model is validated using a typical industrial industry, a furniture factory, as a research case. The results show that the proposed LCR features can capture the nonlinear characteristics of the load sequence, resulting in more precise prediction outcomes. Additionally, based on the FA boosting ELM prediction accuracy, AdaBoost can lower the day-ahead load prediction error once more. Using the mean absolute percentage error (MAPE) as an example, AdaBoost-FA-ELM declines by 76.85% compared to ELM and decreases by 23.90% before and after the LCR features are applied. The proposed forecasting model framework in this paper provides a new research strategy for the field of energy forecasting.

Study of Peak-load regulation characteristics of a 1000MWe S-CO2 Coal-fired power plant and a comprehensive evaluation method for dynamic performance

In the new power system with large-scale grid-connection of intermittent new energy, the coal-fired power plants (CFPPs) play an important role of the ballast stone. In the process of grid-connection, CFPPs receive variable load instructions in real time. Higher peak-load regulation capacity and more flexible response for CFPPs are needed to provide a stable support to the power grid. The supercritical carbon dioxide (S-CO2) cycle has better variable working condition performance, which may improve the flexibility of the CFPPs peak-load regulation process. To explore the peak-load regulation characteristics of the S-CO2 CFPP, the variable load characteristics of a tri-compressions double-reheating intercooling (TC-DRH-IC) S-CO2 CFPP under five control methods are studied. Furthermore, a comprehensive evaluation method for the dynamic performance is proposed. First, the dynamic model of the TC-DRH-IC S-CO2 cycle with the modified isentropic efficiency of turbo-machineries, the unsteady flow heat transfer model of heat exchangers and a proportion integration differentiation (PID) controller is established. Second, the peak-load regulation characteristics of the TC-DRH-IC S-CO2 cycle are analyzed. A comprehensive evaluation method of dynamic control performance considering load change rate, dynamic response time, load rate variation range and cycle efficiency is proposed. Finally, the inventory control method is improved, which can improve the cycle efficiency at low loads. The results show that the improved inventory control method has a rapid practical load change rate of about 10%/min and a wide range of variable-load regulation from 10% to 100%. And the cycle efficiency is improved by 3.67% at 50% of the rated power. The S-CO2 CFPP has the potential of flexible peak-load regulation.

Effects of air change rate and moisture load related to moisture index and the expected moisture performance of a wall assembly

Mould may grow in wood frame wall assemblies when subjected to excessive moisture load over prolonged periods of time. To permit estimating the moisture risk in wood-frame wall assemblies, one approach is to use hygrothermal simulations. This process requires access to relevant climate data and as well, knowledge and experience regarding the use of hygrothermal simulation tools. As well, it may not be practical to undertake such an analysis for each different type of wall being considered for a given location and use. In this regard, the moisture index is usually considered when designing measures for protection from precipitation as it is a useful indicator that reflects the intensity and duration of moisture loads to which a building envelope may be subjected over time. Hence, in the study described in this paper, consideration was given to determining the correlation between mould growth index and moisture index as this would be beneficial to building practitioners in determining the level of protection to mould growth as may be achieved in different climate regions having a particular value for moisture index. The mould growth indices were generated for Oriented Strand Board (OSB) incorporated within a wood-frame vinyl-clad wall assembly located in selected Canadian cities from which moisture indices were derived. Effects of moisture load and air change rate were also taken into account when assessing the correlation between the two indices. The results indicate that when the air change rate and moisture load are favourable to maintain a humid environment, strong correlations were observed between the two indices, vice versa.

Discussion on the Feasibility of Deep Peak Regulation for Ultra-Supercritical Circulating Fluidized Bed Boiler

In order to meet the flexibility operation needs of coal-fired units under the goal of carbon peak and carbon neutralization, it is imperative for circulating fluidized bed (CFB) units to participate in deep peak regulation. By systematically summarizing deep peak regulation operation practice of existing SC and subcritical-parameter-levels CFB units, the feasibility of deep peak regulation technology of an ultra-supercritical (USC) CFB unit under development and being built is analyzed and demonstrated; meanwhile, the deep peak regulation capacity of the boiler is also predicted. The results show that by analyzing the structural characteristics and design performance of the USC-CFB boiler, for technical problems such as stable combustion under low load, hydrodynamic safety, denitration performance under wide load, and rapid boiler load change rate existing in deep peak regulation, technical measures were implemented by selecting advanced boiler furnace type, adopting good design technology of the secondary rising water wall and uniformity design of bed temperature and bed pressure, strengthening the reducing atmosphere inside the furnace, improving the performance of wear-resistant refractory materials, quickly controlling the furnace bed material stock under variable load, optimizing the control strategy of CFB unit, and so on. The boiler achieved good operation characteristics and good deep peak regulation performance, and the pollutant emissions can steadily achieve ultra-low emission standards. When the USC-CFB unit participates in deep peak regulation, the minimum stable combustion load of the boiler can reach 20~30% BMCR, and a boiler load change rate under 30% BMCR or above could reach 1.5~2% BMCR/min, while that below 30% BMCR could reach 1% BMCR/min. The research results can provide references for the deep peak regulation of in-service supercritical (SC) CFB units and design optimization of similar USC-CFB units.