•Primary and secondary energy forms introduced.•Different (electrical and thermal) energy storage technologies presented and compared.•Real life energy storage application analysed to understand the ...most widely applied technology.•Challenges facing the energy storage industry summarised.•Future prospects of the energy storage sector predicted.
Energy storage is nowadays recognised as a key element in modern energy supply chain. This is mainly because it can enhance grid stability, increase penetration of renewable energy resources, improve the efficiency of energy systems, conserve fossil energy resources and reduce environmental impact of energy generation. Although there are many energy storage technologies already reviewed in the literature, these technologies are currently at different levels of technological maturity with a few already proven for commercial scale application. Most of the review papers in energy storage highlight these technologies in details, however; there remains limited information on the real life application of these technologies for energy storage purpose. This review paper aims to address this gap by providing a detailed analysis of real life application and performance of the different energy storage technologies. The paper discusses the concept of energy storage, the different technologies for the storage of energy with more emphasis on the storage of secondary forms of energy (electricity and heat) as well as a detailed analysis of various energy storage projects all over the world. In the final part of this paper, some of the challenges hindering the commercial deployment of energy storage technologies are also highlighted.
•Dynamic modelling of coal-fired subcritical power plant based on first principles.•Shrink and swell characteristics considered in modelling the drum dynamics.•Steady state model validation of ...coal-fired subcritical power plant at different operating loads.•Process analysis for load changes through ramping better than step change.
Coal-fired power plants are the main source of global electricity. As environmental regulations tighten, there is need to improve the design, operation and control of existing or new built coal-fired power plants. Modelling and simulation is identified as an economic, safe and reliable approach to reach this objective. In this study, a detailed dynamic model of a 500MWe coal-fired subcritical power plant was developed using gPROMS based on first principles. Model validations were performed against actual plant measurements and the relative error was less than 5%. The model is able to predict plant performance reasonably from 70% load level to full load. Our analysis showed that implementing load changes through ramping introduces less process disturbances than step change. The model can be useful for providing operator training and for process troubleshooting among others.
In this paper, the potential of improving the energy efficiency of a conventional cryogenic air separation unit (ASU) was investigated through modelling and simulation using Aspen Plus® v 8.1. It is ...achieved through converting the heat from the compressor effluent to electricity using organic Ranking cycle (ORC). Two different arrangements of combining compressor and waste heat recovery ORC system were compared with the conventional cryogenic ASU which was used as the benchmark. The benchmark is a conventional cryogenic ASU with 3 stages of compression which uses water for intercooling. In the first arrangement the water used as the cooling fluid of the intercooler/after cooler heat exchanger of a conventional cryogenic ASU process was replaced by R134a which also acts as the working fluid for the ORC system (C3WHR) while in the second arrangement, the 3 stages compressor of the conventional process was replaced with a single stage compressor with the same overall pressure ratio as the conventional process and the hot compressor effluent cooled with R134a which also acts as the working fluid of the ORC system (C1WHR).
The simulation results based on a cryogenic ASU capable of processing 100 kg/s of atmospheric air at 30 °C as feedstock show that the specific power consumption for the pure products which was 0.32 kWh/kg, 0.37 kWh/kg and 17.35 kWh/kg for oxygen, nitrogen and argon respectively for the conventional cryogenic ASU process was reduced by the addition of the waste heat recovery ORC system. The C1WHR reduced the specific power consumption by an average of 0.2% across the aforementioned pure products while the C3WHR reduced it by an average of 11%. The net power consumption of the conventional cryogenic ASU which was 21826.19 kW was also found to be reduced by the same percentage.
•We model two cryogenic air separation unit with compressor waste heat recovery.•We compare the specific energy consumption of the models.•We compare the overall energy consumption of the models.•Compressor heat recovery improve the energy efficiency of the process.
This study aims to provide insights into the design and operation of full-scale post-combustion CO2 capture for a 500MWe sub-critical power plant through dynamic modelling and simulation. The ...development and validation of the dynamic models of the power plant and CO2 capture plant are described. In addition, the scale-up of the CO2 capture plant from pilot plant scale (where it was validated) to full scale is discussed. Subsequently the manner in which the two plant models were linked is discussed. A floating IP/LP crossover pressure configuration is used. A throttling valve is included between the LP turbine and draw-off point to prevent pressures at the crossover from dropping below required levels in the reboiler for solvent regeneration. The flue gas from the power plant is treated before it is sent to the CO2 capture plant. Four case studies are considered. The first investigates the effect of increasing solvent concentration on the performance of the power plant with the capture plant. The second investigates which absorber packing height offers a good balance between capital and operating costs. The two dynamic case studies show that the CO2 capture plant has a slower response than the power plant. They also reveal an interaction of CO2 capture level and power plant output control loops making it difficult to achieve steady power output levels quickly.
•Experimental studies of pyrolysis and gasification of polyethylene and pine sawdust.•New catalyst Ni-CaO-C synthesised by attaching Ni onto CaO and activated carbon.•Tests indicating high ...performance for H2 production and CO2 adsorption using Ni-CaO-C.•Very good reactivity, pore structure and reductivity of activated carbon demonstrated.•Optimal H2 production (86.74 mol% and 115.33 mmol/g) found experimentally using Ni-CaO-C.
Energy security and environmental pollution have been important topics over the world. With depletion of traditional fossil fuels, it is necessary to find new kinds of substitute energies that are green and renewable. Co-pyrolysis/gasification of mixture of waste (i.e. plastics) and biomass is a potential solution and H2 is an ideal energy carrier with wide range of use. This paper aims to develop a new catalyst Ni-CaO-C and to examine its performance under optimal operating conditions of pyrolysis/gasification of plastics and biomass for H2 production. Experimental studies adjusting Ni loads and support ratios of catalyst were performed to explore the catalytic activity and CO2 adsorption capability of the new catalyst. Operating conditions such as feedstock ratio, pyrolysis temperature, reforming temperature and water injection flowrate were also examined experimentally to find optimal operating conditions. Consequently, experiment results indicated that high H2 production (86.74 mol% and 115.33 mmol/g) and low CO2 concentration (7.31 mol%) in the gaseous products can be achieved with new catalyst Ni-CaO-C under the optimal operating conditions. Therefore, this study points to effective new approaches to increase H2 production from the pyrolysis/gasification of waste plastics and biomass.
•Closed-cycle gas turbine applicable to a wide range of heat sources.•Working fluids include air, nitrogen, supercritical CO2 and helium.•Review of important R&D programmes and operated plants.•Heat ...exchangers are significant driver in the capital cost and technical viability.•Demonstration plant essential before commercial deployment.
In the last few years, there has been considerable interest in closed-cycle gas turbine power plants due to the important contribution it can make to meeting worldwide energy demands. Closed-cycle gas turbine has the potential to serve as power conversion system for a wide range of energy sources such as fossil fuel, concentrated solar power, nuclear, biomass and waste heat. However, there is a need to provide an update on the development of closed-cycle gas turbine with a view to identifying the challenges and the opportunities for future commercialisation. This paper is a review of the research activities and studies carried out worldwide so far on closed-cycle gas turbine. The historical development in chronological order was presented first, followed by a review of some fundamental features such as heat sources, working fluids, heat exchangers and cycle layouts/configurations. Important research programmes and experimental/pilot plants as well as previous commercially operated plants were also reviewed. Moreover, various studies based on modelling and simulation of closed-cycle gas turbine were reviewed, in addition to the operation and control strategies. Based on the review studies, the challenges ahead and potential future breakthroughs were highlighted in different aspects such as heat source technologies, power conversion system and demonstration plant.
Knowledge graphs (KGs) have been widely used in the field of artificial intelligence, such as in information retrieval, natural language processing, recommendation systems, etc. However, the open ...nature of KGs often implies that they are incomplete, having self-defects. This creates the need to build a more complete knowledge graph for enhancing the practical utilization of KGs. Link prediction is a fundamental task in knowledge graph completion that utilizes existing relations to infer new relations so as to build a more complete knowledge graph. Numerous methods have been proposed to perform the link-prediction task based on various representation techniques. Among them, KG-embedding models have significantly advanced the state of the art in the past few years. In this paper, we provide a comprehensive survey on KG-embedding models for link prediction in knowledge graphs. We first provide a theoretical analysis and comparison of existing methods proposed to date for generating KG embedding. Then, we investigate several representative models that are classified into five categories. Finally, we conducted experiments on two benchmark datasets to report comprehensive findings and provide some new insights into the strengths and weaknesses of existing models.
Alterations to the gut microbiota have been previously suggested to be tightly linked to chronic systemic inflammation, which is a major contributing factor to complications and disease progression ...in chronic kidney disease (CKD). Nevertheless, the effect of gut dysbiosis on the pathogenesis and/or production of inflammatory factors in CKD has not been extensively studied to date. In the present study, we conducted 16S ribosomal DNA pyrosequencing using fecal microbiota samples and analyzed the production of serum inflammatory factors in 50 patients with CKD and 22 healthy control (HC) subjects. The results revealed that compared to the HC subjects, patients with CKD exhibited a significant reduction in the richness and structure of their fecal microbiota. At the phylum level, compared to the HC group, patients with CKD also presented reduced abundance of Actinobacteria but increased abundance of Verrucomicrobia. Moreover, the genera
, and
were enriched in the fecal samples of patients with CKD, while
and
were enriched in those of the HC subjects. The abundance of
in the CKD group was significantly lower than that in the HC group (3.08 vs. 0.67%); this decrease in the abundance of
, an important probiotic, in patients with CKD is a striking discovery as it has not been previously reported. Finally, we analyzed whether these changes to the fecal microbiota correlated with CKD clinical characteristics and/or the production of known inflammatory factors. Altered levels of the microbiota genera
, and
were shown to be correlated with CKD disease-severity indicators, including the estimated glomerular filtration rate. Most notably,
was significantly negatively correlated with the production of interleukin-10. The results of the present study suggest that microbiota dysbiosis may promote chronic systemic inflammation in CKD. Furthermore, they support that modifying the gut microbiota, especially
, may be a promising potential therapeutic strategy to attenuate the progression of, and/or systemic inflammation in, CKD.
has a strong carbohydrate utilization ability. This characteristic plays an important role in its gastrointestinal tract colonization and probiotic effects.
LP-F1 presents a high carbohydrate ...utilization capacity. The genome analysis of 165
strains indicated the species has a plenty of carbohydrate metabolism genes, presenting a strain specificity. Furthermore, two-component systems (TCSs) analysis revealed that the species has more TCSs than other lactic acid bacteria, and the distribution of TCS also shows the strain specificity. In order to clarify the sugar metabolism mechanism under different carbohydrate fermentation conditions, the expressions of 27 carbohydrate metabolism genes, catabolite control protein A (CcpA) gene
and TCSs genes were analyzed by quantitative real-time PCR technology. The correlation analysis between the expressions of regulatory genes and sugar metabolism genes showed that some regulatory genes were correlated with most of the sugar metabolism genes, suggesting that some TCSs might be involved in the regulation of sugar metabolism.
•Process simulation for chemical looping combustion (CLC) and its model validation.•Process simulation of humid air turbine (HAT) for power generation.•Process simulation and analysis of CLC–HAT ...cycle.•Economic analysis of the CLC–HAT cycle for natural gas-fired power plant with CO2 capture.•Comparison between CLC–HAT cycle and conventional HAT cycle.
Power generation from fossil fuel-fired power plant is the largest single source of CO2 emission. CO2 emission contributes to climate change. On the other hand, renewable energy is hindered by complex constraints in dealing with large scale application and high price. Power generation from fossil fuels with CO2 capture is therefore necessary to meet the increasing energy demand, and reduce the emission of CO2. This paper presents a process simulation and economic analysis of the chemical looping combustion (CLC) integrated with humid air turbine (HAT) cycle for natural gas-fired power plant with CO2 capture. The study shows that the CLC–HAT including CO2 capture has a thermal efficiency of 57% at oxidizing temperature of 1200°C and reducer inlet temperature of 530°C. The economic evaluation shows that the 50MWth plant with a projected lifetime of 30years will have a payback period of 7years and 6years for conventional HAT and CLC–HAT cycles respectively. The analysis indicates that CLC–HAT process has a high potential to be commercialised.
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