6 research outputs found
An ad hoc control system for managing the dynamic behaviour of a Brayton-based Carnot battery
No full textCarnot batteries (CBs) are considered a suitable grid-scale electricity storage technology to overcome the imbalance between power demand and production in a power grids with high renewable energy sources penetration.
In the literature, several studies propose different configurations, according to thermal storage technology as well as the charge/discharge cycle. Several investigations focus on the thermodynamics and optimisation of these systems.
However, the literature still lacks research dealing with CBs control systems and their dynamic behaviour during transient operations.
For this reason, in this work, an ad hoc dynamic model of a Brayton-based Carnot battery, along with its control system, has been developed in an OpenModelica environment.
The investigated configuration is the so-called Integrated Energy Storage System (I-ESS).
During the charge phase, a high temperature air flow, heated by electric heaters, releases heat to a packed-bed thermal energy storage.
The discharge system is basically a modified gas turbine in which the combustion chamber is replaced by thermal energy storage.
This work focusses on the discharge phase of the system, which is more complex and intrinsically characterised by dynamic behaviour.
To develop the CB’s control system, the authors started from the control system of a conventional gas turbine, which usually acts on two manipulated variables: the fuel mass flow rate and the compressor variable inlet guide vanes position (VIGV).
These variables are devoted to the regulation of the shaft speed and the turbine inlet temperature.
In CBs, on the other hand, the turbine inlet temperature is fixed by the storage temperature, and, since there is no fuel flow, the only manipulated variable remains the VIGV.
Therefore, a dedicated control system is needed.
The control system developed in this work consists of a proportional-integral-derivative (PI(D)) controller that receives as input the shaft rotational speed error and gives as output the signal for the VIGV regulation.
The developed controller was validated and properly tuned to achieve good results in terms of time domain specifications such as overshooting, undershooting, and settling time.
The optimal proportional gain, integral, and derivative time constants are 1.1, 3.5 and 1.1, respectively.
The results show that, given a power step function from 60% to 100%, a 10 MW Carnot battery can achieve a power settling time of approximately 1.2 to 3.3 seconds, with an overshoot of 2.0 to 4.6%.
The maximum shaft speed undershoot is 1.4%.
According to the results, a properly tuned PID controller allows Brayton-based Carnot batteries to have a dynamic response similar to that of a conventional gas turbine, with the additional value that the control system layout of a CB is much simpler and, therefore, easier to manage
An optimized approach to design Thermal Energy Storage Tank for electricity purposes
No full textIn recent years, electricity grids have experienced rapid penetration of power generation units based on variable and unpredictable renewable energy sources such as wind and solar. These sources are crucial for the transition to a more sustainable way of generating energy and therefore in achieving both the reduction of harmful emissions and the climate targets. However, high renewable penetration leads to some negative problems associated with the intermittent and fluctuating behaviour of such sources, such as a decrease in the quality of the energy transmitted through the electrical grid and an increase in the mismatch between power production and demand. To mitigate and/or compensate for such issues, it is extremely important to identify technologies capable of both storing and delivering the surplus of renewable electricity when the production from, for example, solar and wind, is null or insufficient to cover the demand of users. In this context, over the years, numerous energy storage technologies have been studied and developed. But many of them are characterised by significant geographical and morphological constraints, such as compressed air energy storage and pumped hydro energy storage, or suffer from low energy efficiency, such as flow batteries. Among emerging energy storage technologies, Carnot batteries (CBs) offer interesting performance without stringent geographic limitations, making them an attractive solution. Among CBs, integrated thermal energy storage systems (IT-ESS) seem to be a feasible and interesting solution because of their ease of installation and compatibility with existing power plants. Despite their potential, the most important component of this technology is the sensible heat thermal energy storage unit, designed as a packed bed. However, the literature lacks precise methods for designing this storage tank, a gap that motivated the authors to develop an innovative approach to determine the optimal size of the storage device. To this end, and with the aim of properly studying a complex system with the possibility of exchanging power with both users and the electrical grid and to account for the variability of renewable sources, the sizing procedure has been investigated through an optimisation algorithm developed in the Matlab environment. At the same time, the optimal storage device volume and the proper IT-ESS management strategy have been identified. The investigation performed considers real scenarios, analysing real users and describing in an accurate way the intermittent behaviour of renewable sources
Design and management of an Integrated Thermal Energy Storage System
No full textopenNowadays our society is experiencing an energy transition, in which renewable energy sources are assuming a newer and more central role in the energetic mix. In these scenarios, to boost the decarbonization and the usage of sustainable energy systems, Thermal Energy Storage Systems will play a fundamental role. In fact, given the discontinuous and intermittent behaviour of renewable sources, storage devices allow the mitigation of these effects and the enhancement of the electrical grid. These devices can find room not only for electrical applications, but even in the residential and industrial sectors. In this Master's thesis, the scope is to individuate how it is possible to size and manage, in an optimum way, Thermal Energy Storage Systems, starting from the production curves of a renewable energy sources power plantNowadays our society is experiencing an energy transition, in which renewable energy sources are assuming a newer and more central role in the energetic mix. In these scenarios, to boost the decarbonization and the usage of sustainable energy systems, Thermal Energy Storage Systems will play a fundamental role. In fact, given the discontinuous and intermittent behaviour of renewable sources, storage devices allow the mitigation of these effects and the enhancement of the electrical grid. These devices can find room not only for electrical applications, but even in the residential and industrial sectors. In this Master's thesis, the scope is to individuate how it is possible to size and manage, in an optimum way, Thermal Energy Storage Systems, starting from the production curves of a renewable energy sources power plan
Abdome agudo cirúrgico: abordagem diagnóstica e terapêutica nas emergências
No full textConsiderando a relevância clínica e epidemiológica do abdome agudo de origem cirúrgica, especialmente no contexto das urgências hospitalares, destaca-se a necessidade de condutas rápidas, seguras e embasadas em evidências. Diante da diversidade etiológica e da possibilidade de rápida evolução para quadros críticos, o diagnóstico precoce e a escolha terapêutica adequada são determinantes para a redução da morbimortalidade. Objetiva-se, neste estudo, revisar as principais estratégias diagnósticas e terapêuticas empregadas no manejo do abdome agudo cirúrgico em serviços de urgência. Para tanto, foi realizada uma revisão integrativa da literatura, com busca sistemática nas bases PubMed, SciELO, LILACS e Web of Science, abrangendo publicações entre 2020 e 2025. Após triagem e aplicação dos critérios de elegibilidade, 11 artigos foram incluídos. Desse modo, observa-se que a utilização de algoritmos clínicos, a valorização do exame físico aliado aos exames de imagem e a atuação multiprofissional favorecem a identificação precoce de quadros cirúrgicos e a escolha adequada da conduta. Isso permite concluir que a padronização de fluxos, aliada à capacitação contínua das equipes, contribui significativamente para a melhoria dos desfechos clínicos de pacientes com abdome agudo cirúrgico
