Optimal dispatch model for PV-electrolysis plants in self-consumption regime to produce green hydrogen: a Spanish case study

The production of green hydrogen from renewable energy by means of water electrolysis is a promising approach to support energy sector decarbonization. This paper presents a techno-economic model of plants with PV sources connected to electrolysis in self-consumption regime that considers the dynamics of electrolysis systems. The model calculates the optimal hourly dispatch of the electrolysis system including the operational states (production, standby, and idle), the load factor in production, and the energy imports and exports to the electricity grid. Results indicate that the model is a useful decision support tool to operate electrolysis plants connected to PV plants in self-consumption regimes with the target of reducing hydrogen production costs

Multi-state techno-economic model for optimal dispatch of grid connected hydrogen electrolysis systems operating under dynamic conditions

The production of hydrogen through water electrolysis is a promising pathway to decarbonize the energy sector. This paper presents a techno-economic model of electrolysis plants based on multiple states of operation: production, hot standby and idle. The model enables the calculation of the optimal hourly dispatch of electrolyzers to produce hydrogen for different end uses. This model has been tested with real data from an existing installation and compared with a simpler electrolyzer model that is based on two states. The results indicate that an operational strategy that considers the multi-state model leads to a decrease in final hydrogen production costs. These reduced costs will benefit businesses, especially while electrolysis plants grow in size to accommodate further increases in demand

Improved graph model for interdependent gas and electricity critical infrastructures

Interdependence between gas and electricity transmission networks is a subject of concern due to the expanding use of gas for electricity generation in combined-cycle power plants around the world. This paper proposes a novel and much more accurate representation of natural gas and electrical networks based on graph theory, which includes all the assets of both systems and their couplings and offers a more realistic topological model of the two coupled networks. The representation is proposed as a scale-free graph and is mathematically validated in test networks, finding that the representations maintain the same characteristics of traditional graphs, but with more topological detail of the infrastructures

Evaluation of a Thermoelectric Generation system based on Differential-Power Processing architecture under non-uniform temperature conditions

This paper presents a Differential Power Processing (DPP) architecture applied to series-connected thermoelectric generators (TEG). Currently, thermoelectric technology is being considered as a promising power generation technology that can be used to recover waste heat energy. Thus, a thermoelectric generation system is studied under non-uniform temperature conditions in multiple TEG devices. The main objective is to allow each thermoelectric sub-module to reach its maximum power point more quickly. The purpose has been to improve the maximum power point tracking (MPPT) in each sub-module, thus it is possible to increase the efficiency with respect to the traditional method based on a global MPPT. Differential Power converters have been implemented in each TEG sub-module to provide an effective solution and mitigate the impact of the mismatch in the power obtained. The DPP architecture consists of a small micro-converter, at the submodular level, applied to the thermoelectric cell. The control algorithm is oriented to polarize each TEG device at its optimal point, which allows us an active balancing among the different TEG sub-modules regardless of the operating temperature. Matlab-Simulink has been the software used to develop the TEG module-Array

Generalized discontinuous PWM strategy applied to a grid-connected modular multilevel converter

This paper presents a new PWM strategy for the control of active and reactive power flow, applied to a three-phase power inverter connected to a microgrid. Power quality and reactive compensation are essential in the integration of renewable energy sources in small grids (stand-alone mode or connected to the utility grid). The control algorithm of the grid-connected system is applied for voltage control. This technique provides independent control of the active and reactive power flow in the utility grid while maintaining constant the DC-link voltage. As a novelty, a Generalized Discontinuous PWM technique is implemented in the control algorithm of the grid-connected converter. Losses in the converter are reduced while the efficiency of the equipment is increased. As a technological innovation, in addition to the power flow control technique, a modular multilevel converter (MMC) is introduced. The main purpose of the system is to improve voltage unbalance and harmonic compensation in stand-alone grids. Some advantages of the model developed here include the cellular concept, easy thermal design, increased system efficiency and improvement in the system expansion capacity. The simulation model has been developed and tested using MATLAB/Simulink software

Vulnerability assessment of a large electrical grid by new graph theory approach

In previous research a novel methodology to assess structural vulnerability was proposed and applied in IEEE test system and high voltage transmission networks of 94 buses, by using graph theory to investigate various risk scenarios that can trigger cascading failures. In this paper we validate the application of this methodology in larger networks by applying a case study on the transmission network 230 and 400 kV of Mexico. The events of cascading failures are simulated through two elimination strategies: by deliberate attacks on critical nodes or by random errors. Iterations are performed by running successive N-1 contingencies on a network that is constantly changing its structure with the elimination of each node. The power flows are not necessary and only the calculation of the graph statistical parameter geodesic vulnerability is required. This reduces the computation time and leads to a comparative analysis of structural vulnerability

Vulnerability and Resilience Assessment of Power Systems: From Deterioration to Recovery via a Topological Model based on Graph Theory

Traditionally, vulnerability is the level of degradation caused by failures or disturbances, and resilience is the ability to recover after a high-impact event. This paper presents a topological procedure based on graph theory to evaluate the vulnerability and resilience of power grids. A cascading failures model is developed by eliminating lines both deliberately and randomly, and four restoration strategies inspired by the network approach are proposed. In the two cases, the degradation and recovery of the electrical infrastructure are quantified through four centrality measures. Here, an index called flow-capacity is proposed to measure the level of network overload during the iterative processes. The developed sequential framework was tested on a graph of 600 nodes and 1196 edges built from the 400 kV high-voltage power system in Spain. The conclusions obtained show that the statistical graph indices measure different topological aspects of the network, so it is essential to combine the results to obtain a broader view of the structural behaviour of the infrastructure

EGFR inhibitors erlotinib and lapatinib ameliorate epidermal blistering in pemphigus vulgaris in a non-linear, V-shaped relationship

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Outcomes of renal replacement therapy in boys with prune belly syndrome : findings from the ESPN/ERA-EDTA Registry

As outcome data for prune belly syndrome (PBS) complicated by end-stage renal disease are scarce, we analyzed characteristics and outcomes of children with PBS using the European Society for Pediatric Nephrology/European Renal Association-European Dialysis and Transplant Association (ESPN/ERA-EDTA) Registry data. Data were available for 88 male PBS patients aged <20 years who started renal replacement therapy (RRT) between 1990 and 2013 in 35 European countries. Patient characteristics, survival, and transplantation outcomes were compared with those of male patients requiring RRT due to congenital obstructive uropathy (COU) and renal hypoplasia or dysplasia (RHD). Median age at onset of RRT in PBS was lower [7.0; interquartile range (IQR) 0.9-12.2 years] than in COU (9.6; IQR: 3.0-14.1 years) and RHD (9.4; IQR: 2.7-14.2 years). Unadjusted 10-year patient survival was 85% for PBS, 94% for COU, and 91% for RHD. After adjustment for country, period, and age, PBS mortality was similar to that of RHD but higher compared with COU [hazard ratio (HR) 1.96, 95% confidence interval (CI) 1.03-3.74]. Seventy-four PBS patients (84%) received a first kidney transplant after a median time on dialysis of 8.4 (IQR 0.0-21.1) months. Outcomes with respect to time on dialysis before transplantation, chance of receiving a first transplant within 2 years after commencing RRT, and death-censored, adjusted risk of graft loss were similar for all groups. This study in the largest cohort of male patients with PBS receiving RRT to date demonstrates that outcomes are comparable with other congenital anomalies of the kidney and urinary tract, except for a slightly higher mortality risk compared with patients with COU.Peer reviewe

Data quality and patient characteristics in European ANCA-associated vasculitis registries: data retrieval by federated querying

Objectives This study aims to describe the data structure and harmonisation process, explore data quality and define characteristics, treatment, and outcomes of patients across six federated antineutrophil cytoplasmic antibody-associated vasculitis (AAV) registries.Methods Through creation of the vasculitis-specific Findable, Accessible, Interoperable, Reusable, VASCulitis ontology, we harmonised the registries and enabled semantic interoperability. We assessed data quality across the domains of uniqueness, consistency, completeness and correctness. Aggregated data were retrieved using the semantic query language SPARQL Protocol and Resource Description Framework Query Language (SPARQL) and outcome rates were assessed through random effects meta-analysis.Results A total of 5282 cases of AAV were identified. Uniqueness and data-type consistency were 100% across all assessed variables. Completeness and correctness varied from 49%–100% to 60%–100%, respectively. There were 2754 (52.1%) cases classified as granulomatosis with polyangiitis (GPA), 1580 (29.9%) as microscopic polyangiitis and 937 (17.7%) as eosinophilic GPA. The pattern of organ involvement included: lung in 3281 (65.1%), ear-nose-throat in 2860 (56.7%) and kidney in 2534 (50.2%). Intravenous cyclophosphamide was used as remission induction therapy in 982 (50.7%), rituximab in 505 (17.7%) and pulsed intravenous glucocorticoid use was highly variable (11%–91%). Overall mortality and incidence rates of end-stage kidney disease were 28.8 (95% CI 19.7 to 42.2) and 24.8 (95% CI 19.7 to 31.1) per 1000 patient-years, respectively.Conclusions In the largest reported AAV cohort-study, we federated patient registries using semantic web technologies and highlighted concerns about data quality. The comparison of patient characteristics, treatment and outcomes was hampered by heterogeneous recruitment settings