Search

[Display omitted] • A holistic optimization approach is proposed for district heating plants. • The backup boiler should be placed upstream of the storage tank and in parallel. • The optimal storage volume is around 37.5 L per kW peak demand. • The storage tank reduces the life cycle costs by up to 1.343%. • Thermal storage cut down carbon emissions by up to 17.33%. A large fraction of district heating networks in Europe are still operating without thermal energy storage. While offering operational flexibility, the presence of energy storage complicates the problems of optimal sizing and control of the heat production plant. This necessitates a novel approach to system sizing based on non-linear programming in order to capture the system's thermal response and inertia. Therefore, the present study focuses on such a typical plant in France and describes a holistic approach to optimize the capacities/parameters of system components, positions of the energy sources, as well as hourly flow rates. Such a simultaneous tuning of the system parameters and operating variables is essential to maximize the cost savings over the system's lifetime. The proposed framework here maintains the original non-linear form of the objective function and the constraints for more accuracy while allowing precise modeling of the thermally stratified storage tank by decoupling its calculations at a lower simulation level. Hence, the computation time in MATLAB® R2020A is mostly below 20 min on a typical personal computer. The lowest levelized cost of heat (57.259 EUR/MWh) is achieved when placing the gas boiler on a parallel line between the biomass boiler and the storage tank while sizing the two boilers using fractions of 0.33 and 0.73 of the maximum hourly demand, respectively, as well as a storage volume of 318.9 m3. Such relatively small storage reduces the lifecycle costs by a maximum of 1.34 % while reducing the specific carbon emissions by 17.33 %. Besides, it dampens the fluctuations in supply flow rates, minimizes unnecessary flow recirculation, and ensures a stable heat supply. Overall, thermal storage has a reasonable positive impact from an economic perspective, but a substantial impact on operational flexibility and mitigated carbon emissions. [ABSTRACT FROM AUTHOR]

Intraoperative surgical prosthetic heart valve (SHV) choice is a key determinant of successful surgery and positive postoperative outcomes. Currently, many controversies exist around the sizing and labelling of SHVs rendering the comparison of different valves difficult. To explore solutions, an expert Valve Labelling Task Force was jointly initiated by the European Association for Cardio-Thoracic Surgery (EACTS), The Society of Thoracic Surgeons (STS) and the American Association for Thoracic Surgery (AATS). The EACTS–STS–AATS Valve Labelling Task Force, comprising cardiac surgeons, cardiologists, engineers, regulators and representatives from the International Organization for Standardization (ISO) and major valve manufacturers, held its first in-person meeting in February 2018 in Paris, France. This article was derived from the meeting's discussions. The Task Force identified the following areas for improvement and clarification: reporting of physical dimensions and characteristics of SHVs determining and labelling of SHV size, in vivo and in vitro testing and reporting of SHV haemodynamic performance and thrombogenicity. Furthermore, a thorough understanding of the regulatory background and the role of the applicable ISO standards, together with close cooperation between all stakeholders (including regulatory and standard-setting bodies), is necessary to improve the current situation. Cardiac surgeons should be provided with appropriate information to allow for optimal SHV choice. This first article from the EACTS–STS–AATS Valve Labelling Task Force summarizes the background of SHV sizing and labelling and identifies the most important elements where further standardization is necessary. [ABSTRACT FROM AUTHOR]

In France, most of the trains are electrical and some are fed by 1500 V DC voltage. When a train is traveling, the power consumption creates a voltage drop. Therefore, below a certain limit, the train has to slow down its speed. This limitation prevents the increase of traffic in some area that needs an electric reinforcement. This paper proposes to use embedded storage systems to support the voltage of the catenary. The main issue is how to size such an energy storage system? In this way, several aspects (e.g.: the energy management strategy) have to be taken into account. The paper deals with an optimization-based sizing method for the embedded energy storage systems. The proposed method takes into account the energy management strategy in the sizing by optimization. A comparison is made between the use of batteries or supercapacitors. [ABSTRACT FROM AUTHOR]