1,738 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
AN INNOVATIVE TOOL FOR OPTIMIZING THE ENERGY HUB OF LARGE BUILDINGS: THE CASE STUDY OF A NEW HOSPITAL IN NORTHERN ITALY
No full textThe challenge of achieving net zero emissions by 2050 necessitates to drastically reduce the energy consumption of the building sector, which alone contributes for almost 40% of the anthropic CO_2 emissions. In recent years, growing attention has been paid to the minimization of costs and emissions of large buildings by optimizing the design and operation of their energy systems. Most of the works available in the literature consider a limited set of technologies to meet only the electrical and heating demands.
In this work an innovative model is developed for the optimization of the energy hub of a hospital, characterized by 5 distinct energy demands: Electrical, Heating, Cooling, Steam and Sanitary Hot Water. To satisfy such demands, the proposed model considers a large set of technologies including cogeneration units, absorbers, reversible and multipurpose heat pumps. The tool consists of two sequential Python codes for the size optimization and the operation optimization, respectively. The first code defines the size of each technology considering the energy needs of four representative days obtained using the k-medoid method, with two extreme days added to ensure load supply. A preliminary investigation demonstrated that this clustering technique leads to an overestimation in the objective function of less than 3%, compared to a 365-days simulation. Therefore, the computational time is drastically reduced with a small impact on the results accuracy. The optimal sizes obtained from the first part of the model are used as input for the second code, which defines the optimal operation of the system throughout the year. The optimization problems are solved using the Python extension of Gurobi, a software that allows for the assessment of MIQP and MILP models by exploiting the branch and bound method. Two different objective functions are considered: total annual costs and CO_2 emissions. The first code results show that, according to the considered objective function, a reduction of 14.4% in the annual costs or a reduction of 12.36% in the CO_2 emissions can be reached with respect to a non-optimized reference configuration, with a difference between the two optimized solutions of 20.60\% in the CO_2 emissions and of 42.07% in the total costs. Between the two solutions, the one provided by the economical optimization is chosen for the entire year simulation. Once the technologies to be used were selected, the simulation of the model was performed resulting in a cost increase with respect to the first code of 4.44 %, and an increase of CO_2 emissions of 4.5%
TUTELA DEL LAVORO E LIBERTA' D'IMPRESA NEI PROCESSI DI ESTERNALIZZAZIONE
No full textL’elaborato analizza le conseguenze lavoristiche della successione fra imprenditori, muovendo da una ricognizione delle varie tipologie di esternalizzazione con le relative esigenze e principali criticità.
L’indagine si concentra in primo luogo sul trasferimento d’azienda, esaminando la normativa e la giurisprudenza europee per passare poi alla disciplina di diritto interno, alle procedure sindacali e a uno specifico focus sul trasferimento delle aziende in crisi.
Successivamente l’autore si sofferma sull’appalto, prendendone in particolare considerazione gli indici di genuinità, i criteri di distinzione dalla somministrazione illecita di manodopera e la tutela delle maestranze in caso di avvicendamento fra imprese.
Da ultimo, la ricerca approfondisce le c.d. “clausole sociali”, sia di prima che di seconda generazione, valutandone la compatibilità con il diritto eurounitario e con la costituzione nonché riflettendo sui possibili rimedi in caso di loro violazione.The author analyzes the labour consequences of the succession between entrepreneurs, starting from a recognition of the various types of outsourcing with the related needs and main critical issues.
The survey focuses primarily on the transfer of businesses, examining European legislation and case-law and then moving on to internal legislation, trade union procedures and a specific focus on the transfer of companies in crisis.
The author then dwells on the contract, taking into account in particular the indications of authenticity, the criteria of distinction from the illicit administration of labour and the protection of workers in the event of turnover between companies.
Finally, the research deepens the "social clauses", both first and second generation, assessing their compatibility with European law and with the constitution and reflecting on possible remedies in case of their violation
Ultra Low Carbon Vehicles: New Parameters for Automotive Design
No full textAs the influence of vehicle emissions on our environment has become better understood, the UK government has recently placed urgent emphasis on the implementation of low carbon
technologies in the automotive industry through: the UK Low Carbon Industrial Strategy. The overall objective is to offer big incentives to consumers and support for the development of infrastructure and engineering solutions. This scheme however does not consider how the development of functional and experiential user value might drive consumer demand, contributing to the adoption of low carbon vehicles (LCVs) in the mass market.
With the emergence of the North East of England as the UK’s first specialised region for the development of ultra-low carbon vehicles (ULCVs), ONE North East, as a development agency for the region's economic and business development, and Northumbria University Ideas-lab have supported a project to facilitate innovation through the collaboration of technology, research and development (R&D) and business. The High Value Low Carbon (HVLC) project aims to envisage
new user value made possible by the integration of low carbon vehicle platforms with new process and network technologies. The HVLC consortium represents vehicle manufacturers and their suppliers as well as technology based companies and through an ongoing process of design concept generation the project offers a hub for innovation led enterprise.
Whilst new technological developments in areas such as power generation, nano materials, hydrogen fuel cells, printed electronics and networked communications will all impact on future automotive design, the mass adoption of low carbon technologies represents a paradigm shift for the motorist. This paper aims to describe how the mapping of new parameters will lead to new transport scenarios that will create the space for new collaborative research on user experiences supported by innovative technologies and related services
Optimization and assessment method to approach industrial site decarbonization: A case study of a light industry
No full textThe industrial sector includes a wide range of industries and processes for which a single approach or universal strategies for decarbonization can hardly be identified. In general, the most efficient way to decarbonize building sites consists of two phases: (i) reduce the energy demand and (ii) replace the fossil-based power generation units with renewable energy sources, possibly working on the management of HVAC systems to reduce the required peak power. Literature provides general rules and schemes, but no specific works on the energy retrofit of industrial buildings have been found in literature so far. The present study investigates an existing industrial district, using dynamic energy models of buildings tuned with the current conditions and compared with seven decarbonization scenarios. A neutral water loop exchanging heat with the ground has been studied, representing a widely replicable solution due to the higher heat exchange efficiency and the modular installation, which can be expanded within the site. The significant energy savings (28%) and CO2 emission reduction (up to 70%) obtained are representative of the potential achievable for many industrial sites in mild European climates, where decarbonization should achieve optimal cost-benefit results while minimizing the impact on the production through modular approaches
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Matteo Maria Boiardo (1441-1494)
No full textMatteo Maria Boiardo – contemporary of Sir Thomas Malory and forerunner of Shakespeare, Spenser, Milton, Cervantes, Tolkien, and C.S. Lewis – is best known as the author of the Orlando Innamorato [Orlando in Love], a poem in ottava rima organically merging Carolingian epic and Arthurian romance. He was also a lyric and pastoral poet, playwright, and translator of classical texts into the Italian vernacular. Matteo was active in Italy during the years of 1463 throughout 1494, the year of his death
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