Flexible operation of supercritical power plant via integration of thermal energy storage

© 2018 The Author(s).This chapter presents the recent research on various strategies for power plant flexible operations to meet the requirements of load balance. The aim of this study is to investigate whether it is feasible to integrate the thermal energy storage (TES) with the thermal power plant steam-water cycle. Optional thermal charge and discharge locations in the cycle have been proposed and compared. Dynamic modeling and simulations have been carried out to demonstrate the capability of TES integration in supporting the flexible operation of the power plant. The simulation software named SimuEngine is adopted, and a 600 MW supercritical coal-fired power plant model is implemented onto the software platform. Three TES charging strategies and two TES discharging strategies are proposed and verified via the simulation platform. The simulation results show that it is feasible to extract steam from steam turbines to charge the TES and to discharge the stored thermal energy back to the power generation processes. The improved capability of the plant flexible operation is further studied in supporting the responses to the grid load demand changes. The results demonstrated that the TES integration has led to much faster and more flexible responses to the load demand changes.Peer reviewe

Direct methane conversion to methanol by ionic liquid-dissolved platinum catalysts

Ternary systems of inorganic Pt salts and oxides, ionic liquids and concentrated sulfuric acid are effective at catalyzing the direct, selective oxidation of methane to methanol and appear to be more water tolerant than the Catalytica reaction

Study of supercritical power plant integration with high temperature thermal energy storage for flexible operation

The paper presents the recent research in study of the strategies for the power plant flexible operation to serve the requirement of grid frequency control and load balance. The study aims to investigate whether it is feasible to bring the High Temperature Thermal Storage (HTTS) to the thermal power plant steam-water cycle, to identify the suitable thermal charge and discharge locations in the cycle and to test how the HTTS integration can help support grid operation via power plant dynamic mathematical modelling and simulation. The simulation software named SimuEngine is adopted and a 600 MW supercritical coal-fired power plant model is implemented onto the software platform. Three HTTS charging strategies and two HTTS discharging strategies are proposed and tested via the simulation platform. The simulation results show that it is feasible to extract steam from the steam turbine to charge the HTTS, and to discharge the stored thermal energy back to the power generation processes. With the integration of the HTTS charge and discharge processes, the power plant simulation model is also connected to a simplified GB (Great Britain) grid model. Then the study is extended to test the improved capability of the plant flexible operation in supporting the responses to the grid load demand changes. The simulation results show that the power plant with HTTS integration has faster dynamic responses to the load demand changes and, in turn, faster responses to grid frequency services

Block-regularized 5×\times2 Cross-validated McNemar's Test for Comparing Two Classification Algorithms

In the task of comparing two classification algorithms, the widely-used McNemar's test aims to infer the presence of a significant difference between the error rates of the two classification algorithms. However, the power of the conventional McNemar's test is usually unpromising because the hold-out (HO) method in the test merely uses a single train-validation split that usually produces a highly varied estimation of the error rates. In contrast, a cross-validation (CV) method repeats the HO method in multiple times and produces a stable estimation. Therefore, a CV method has a great advantage to improve the power of McNemar's test. Among all types of CV methods, a block-regularized 5$\times$2 CV (BCV) has been shown in many previous studies to be superior to the other CV methods in the comparison task of algorithms because the 5$\times$2 BCV can produce a high-quality estimator of the error rate by regularizing the numbers of overlapping records between all training sets. In this study, we compress the 10 correlated contingency tables in the 5$\times$2 BCV to form an effective contingency table. Then, we define a 5$\times$2 BCV McNemar's test on the basis of the effective contingency table. We demonstrate the reasonable type I error and the promising power of the proposed 5$\times$2 BCV McNemar's test on multiple simulated and real-world data sets.Comment: 12 pages, 6 figures, and 5 table

Retinoic Acid Receptor Signaling in the Differentiation of Pluripotent Stem Cells into Skeletal Muscle Lineage

Pluripotent stem cells have the capacity to differentiate into many types of cell lineages including skeletal myocytes. Nevertheless, the frequency of pluripotent stem cells generating skeletal myocytes in the absence of developmental cues is very low, and signaling molecules are required to commit them to muscle lineage. Thereby, in vitro stem cell differentiation has been used for decades to study molecular mechanisms of myogenic specification. Similar to human embryonic stem (ES) cells, various mouse pluripotent stem cells respond well to development cues in vitro to differentiate into cell types of all three primary germ layers. In tissue cultures, they can be induced into myogenic differentiation with an aggregation protocol which involves the formation of embryoid bodies (EBs). Their commitment into the skeletal muscle lineage recapitulates closely the cellular and molecular processes occurring in the early embryogenesis. Treatment of these stem cells with regulatory signals important for embryonic development, such as ligands of nuclear receptors, during EB formation markedly enhances the efficiency of myogenic differentiation. However, many challenges remain. Understanding on a molecular level, how different signaling pathways and chromatin dynamics converge during stem cell differentiation to specify the muscle lineage is imperative for identifying effective signaling molecules to generate sufficient amount of muscle progenitor cells for potential therapeutics. To this end, mouse stem cells will continue to serve as valuable model systems due to their close resemblance to skeletal myogenesis in vivo, and the ease of manipulation in experimental procedures. In this chapter, we will focus on recent research findings on nuclear receptor signaling in the specification of skeletal muscle lineage

Proteolytic processing and activation of Clostridium perfringens epsilon toxin by caprine small intestinal contents.

Epsilon toxin (ETX), a pore-forming toxin produced by type B and D strains of Clostridium perfringens, mediates severe enterotoxemia in livestock and possibly plays a role in human disease. During enterotoxemia, the nearly inactive ETX prototoxin is produced in the intestines but then must be activated by proteolytic processing. The current study sought to examine ETX prototoxin processing and activation ex vivo using the intestinal contents of a goat, a natural host species for ETX-mediated disease. First, this study showed that the prototoxin has a KEIS N-terminal sequence with a molecular mass of 33,054 Da. When the activation of ETX prototoxin ex vivo by goat small intestinal contents was assessed by SDS-PAGE, the prototoxin was processed in a stepwise fashion into an ~27-kDa band or higher-molecular-mass material that could be toxin oligomers. Purified ETX corresponding to the ~27-kDa band was cytotoxic. When it was biochemically characterized by mass spectrometry, the copresence of three ETX species, each with different C-terminal residues, was identified in the purified ~27-kDa ETX preparation. Cytotoxicity of each of the three ETX species was then demonstrated using recombinant DNA approaches. Serine protease inhibitors blocked the initial proteotoxin processing, while carboxypeptidase inhibitors blocked further processing events. Taken together, this study provides important new insights indicating that, in the intestinal lumen, serine protease (including trypsin and possibly chymotrypsin) initiates the processing of the prototoxin but other proteases, including carboxypeptidases, then process the prototoxin into multiple active and stable species. Importance: Processing and activation by intestinal proteases is a prerequisite for ETX-induced toxicity. Previous studies had characterized the activation of ETX using only arbitrarily chosen amounts of purified trypsin and/or chymotrypsin. Therefore, the current study examined ETX activation ex vivo by natural host intestinal contents. These analyses demonstrated that (i) ETX processing in host intestinal contents occurs in an ordered, stepwise fashion, (ii) processing of prototoxin by host intestinal contents results in higher-molecular-mass material and 3 distinct ~27-kDa ETX species, and (iii) serine proteases, such as trypsin, chymotrypsin, and other proteases, including carboxypeptidases, play a role in the activation of ETX by intestinal contents. These studies provide new insights into the activation and processing of ETX and demonstrate that this process is more complicated than previously appreciated