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Energy flexibility and demand management in buildings
Full text linkLo sfruttamento della flessibilità energetica negli edifici rappresenta una delle soluzioni più promettenti per consentire il passaggio a sistemi energetici ad alta penetrazione di rinnovabili. Disporre di un edificio flessibile significa poter applicare efficientemente strategie di gestione della domanda (Demand Side Management, DSM) che rappresentano uno degli aspetti principali caratterizzanti il concetto di Smart Grid. Il DMS è definito come l'insieme di tutte quelle strategie volte a influenzare gli usi dell'elettricità degli utenti in modo da produrre cambiamenti nella forma della loro curva di carico.
Data la crescente domanda elettrica del settore residenziale, soprattutto per la diffusione di impianti di riscaldamento e raffrescamento alimentati elettricamente (es. split e pompe di calore), gli edifici mostrano una predisposizione a produrre variazioni programmate della loro domanda elettrica, grazie ai diversi livelli di inerzia termica in essi già disponibile (es. massa termica dell’involucro o dispositivi dedicati come serbatoi di acqua calda o fredda). Inoltre, grazie a tecniche di controllo avanzate, possono sfruttare diverse fonti energetiche per soddisfare i propri fabbisogni termici, riducendo al contempo i prelievi dalla rete elettrica.
Il lavoro presentato in questa tesi si inserisce in questo contesto. L'obiettivo è quello di fornire un'analisi dei diversi aspetti che caratterizzano la flessibilità ottenibile dalla gestione dei carichi termici ed elettrici negli edifici residenziali dotati di pompe di calore. L'analisi si estende progressivamente dal contesto dello scenario progettuale dei singoli edifici a quello operativo degli aggregati. Nella tesi inoltre sono presentate metodologie innovative di quantificazione in aggiunta alla simulazione di diversi casi di studio. In generale, tutti i risultati consentono di confermare la potenzialità degli edifici nella fornitura di servizi di flessibilità energetica.The exploitation of energy flexibility in buildings represents one of the most promising solutions to allow the transition to energy systems with a high penetration of renewable energy sources. Having a high flexible building means to be able to efficiently apply demand side management strategies (DSMs) which represent one of the main aspects characterizing the concept of Smart Grid. DMS is defined as the set of all those strategies aimed at influencing customer uses of electricity in ways that will produce desired changes in the utility’s load shape.
Given the increasing electricity demand in the residential sector, especially for the diffusion of heating and cooling systems electrically powered (e.g., split systems and heat pumps), buildings show a predisposition to produce variations in the electrical demand, due to the different levels of thermal inertia already available in them (e.g., the thermal mass embedded in the envelope or dedicated devices as cold and/or hot water tank). Moreover, thanks to advanced control techniques, buildings could exploit different energy sources to satisfy their thermal requirements, while reducing withdrawals from the power grid.
The work presented in this thesis fits into this context. The objective is to provide an overview of the different aspects that characterize the energy flexibility obtainable from the management of thermal and electrical loads in residential buildings equipped with heat pumps. The analysis is gradually extended from the context of the design scenario of single buildings to the operative analysis of clusters of buildings. Novel methodologies of quantification and evaluation are introduced in addition with the examination of different simulation-based case studies. In general, all the analyses allow to confirm the great potential of residential buildings in providing energy flexibility services
Flexible heat pumps in clusters of buildings: energy flexibility quantification of space cooling loads
No full textThe energy demand for building cooling has experienced a significant growth in the past years, with significant implications for power grids. Consequently, building cooling flexible energy demand management is a good instrument to provide grid stability and favour integration of Renewable Energy Sources. By using reversible heat pump systems to provide cooling loads, energy flexibility can be provided to the grid, that, in case of widespread installations, can be activated as reserves. This is especially relevant giving the increasing share on the market of heat pumps. However, quantifying the energy flexibility that heat pumps in clusters of buildings can provide is still very difficult. Therefore, the aim of this paper is to investigate the response of a cluster of buildings representative of the Italian building stock to different peak-shaving strategies. For this purpose, a tool developed by the authors was implemented to assess the flexible characteristics of the space cooling systems
Demand response for renewable energy communities: Exploring coordination of prosumer-generated PV and flexible aggregated demand in the Italian framework
No full textEnergy flexible buildings: A methodology for rating the flexibility performance of buildings with electric heating and cooling systems
Full text link© 2019 In the present energy scenario, buildings are playing more and more as energy prosumers. They can use and produce energy and also actively manage their energy demand. The energy flexibility quantifies their potential to adjust the energy demand on the basis of external requests. The objective of this paper is to propose a method for buildings energy flexibility labelling at design conditions in the same fashion as the energy performance label. The flexibility quantification is based on the calculation of four flexibility parameters, which contribute to the definition of the Flexibility Performance Indicator. In order to assess the Flexibility Performance Indicator, buildings dynamic simulations are necessary and the boundary conditions (i.e. demand response event, representative day, comfort constraints)to be considered during the evaluation are provided as part of the proposed methodology. The method was applied to different Italian buildings, which differ for geographic location and design specifications and, in particular, the effects of building structure, heating/cooling systems and energy storage systems were compared. Results show that the climatic conditions affect the flexibility performance, while the building feature more relevant is the thermal mass of the building envelope, more than that provided by the distribution system. A sensitivity analysis to evaluate how the results are influenced by the proposed boundary conditions was also performed. Their choice confirms to have a relevant impact on flexibility quantification, then their unique definition has a paramount importance within this methodology.sponsorship: This work has been supported by MIUR of Italy in the framework of PRIN2015 project: "Clean heating and cooling technologies for an energy efficient smart grid", Prot. 2015M8S2PA. (MIUR of Italy in the framework of PRIN2015 project: "Clean heating and cooling technologies for an energy efficient smart grid"|2015M8S2PA)status: Publishe
Selection maps based on multi-objective optimization of design and control for residential heat pumps systems
No full textAlthough heat pumps are one of the most promising technologies to support the energy transition in space heating sector more knowledge is needed on how to design their installation for different plant configuration and control strategy. In this work a methodology to obtain selection maps, which consider both the sizing of the system and the influence of the control strategy, is proposed. Both the optimal design parameters and control strategies are evaluated to minimize seasonal energy consumption and investment cost. The methodology is applied to a reference Italian residential building. Results show that, regardless of the objective function, the optimal size of the heat pump increases as the temperature level of the hot source increases. Furthermore, the selection maps show how the optimal sizing varies according to the control strategy (i.e., fixed supply temperature or compensation curve) and the presence of a thermal storage device. In general, however, the proposed methodology aims to extrapolate the link between the design and the operation of a heat pump system. Therefore, the selection maps can represent an important instrument to select the main features of the installation depending on the operating conditions
Energy analysis of a hydrogen integrated system in the residential sector
Full text linkNowadays, buildings are responsible for almost 40% of global energy consumption, which is addressed
by thermal (e.g., heating, cooling, and hot water) and electric (e.g., lighting and household appliances) loads. To
meet the residential energy demand and, at the same time, ensure the decarbonisation of the energy infrastructure,
hydrogen-based cogeneration systems might represent a viable solution. This work aims at evaluating the
performance of a green hydrogen integrated system consisting of a Proton Exchange Membrane (PEM)
electrolyser, hydrogen storage tanks, and a PEM fuel cell to meet both the electricity and, partially, the thermal
energy demands of a condominium located in the center of Italy. The analysis considers a single energy scenario
in which a Photovoltaic (PV) plant installed on the roof is directly connected with the hydrogen integrated system
without any withdrawal from the national grid (e.g., off-grid operation mode). Results showed that, during the
year, the user is completely self-sufficient from the electricity demand point of view. Furthermore, 22% of the
thermal need can be satisfied through the fuel cell cogeneration system
Valorization of olive mill wastewater for Arthrospira platensis production
No full textIntending to reduce the related environmental impact of olive oil wastewater while producing new by-products, this research paper proposes an innovative solution for the treatment of wastewater that combines microfiltration and ultrafiltration techniques with microalgae cultivation. Laboratory scale analysis and pilot scale operation have been performed to assess the techno-economic viability of the olive mill wastewater for Arthrospira platensis production. More precisely, growth rate, time of division, and characterization (lipids, carbohydrates, proteins, and so forth) of microalgae are evaluated. The results obtained from the techno-economic analysis show that the integration of the systems makes it possible to efficiently exploit the inorganic nutrients of the olive mill wastewater for the cultivation of Arthrospira platensis. In particular, the quality of the obtained biomass complies with the food grade regulations, whereas avoided costs for the olive mill wastewater disposal bring a reduction of 70% in the biomass production cost
Role of Non-Adiabatic Capillary Tube in Water Cooler Performance
Full text linkIn this paper, a numerical model of a capillary tube is developed. The considered expansion device is placed against the suction line at the inlet of the compressor. Wrapping the capillary tube around the suction line allows heat to be recovered by superheating the refrigerant leaving the evaporator. This increases the degree to which the fluid is superheated, preventing liquid droplets from entering the compressor and causing damage. The open-source software PYTHON is used for modelling the non adiabatic capillary tube, and the results are validated by comparing them with experimental tests. This study demonstrates that an accurate contact of the capillary tube with the suction line affects the superheating of the compressor inlet fluid by increasing its temperature by up to 5 degrees and produces an increase in COP of 3–4%. On the other hand, the length of the capillary tube affects the flow rate of the refrigerant circulating in the cycle; in particular, it is noted that a 300% increase in the capillary tube length leads to a decrease in the refrigerant flow rate of up to 50–60%
Dynamic building thermal mass clustering for energy flexibility assessment: An application to demand response events
Full text linkDemand response programs encompass a range of externally control strategies designed to modify consumer end-use load according to specific grid demands. In the current renewable integration context, power systems need to implement such demand strategies to provide energy flexibility during grid stress periods. Nevertheless, the extensive adoption of demand response initiatives in the building sector is confronted by notable obstacles, mainly due to the absence of standardized assessment methods and metrics, and the lack of established regulatory frameworks, all of which hinder the formation of competitive flexibility asset portfolios. Indeed, energy flexibility quantification frameworks are not unified and are usually based on the control objectives and quantification indicators. In this framework, this paper proposes a methodology to cluster residential buildings based on the analytical assessment of their dynamic thermal response, regardless the boundary conditions (i.e., weather data, occupancies, ...) and the type of demand response event. The proposed methodology provides a quick and simple quantification of how a building is expected to respond under different demand response events and durations, which is critical for both customers and demand response agents to decide and select the involvement of buildings in each event and potentially to design personalized demand response events for each building. An extensive analysis was conducted to evaluate the methodology based on 28 real residential buildings, whose data were presented in a previous study. Results provide the potential effectiveness and application for energy flexibility purposes of this methodology based on dynamic thermal building clustering. Moreover, it can be concluded that it is not possible to deduce a thermal inertia available classification exclusively based on design thermal and geometric characteristics of the building; being necessary to consider the duration of involvement, since they highly influence on the residential building thermal behavior, and thus, on the corresponding clustering
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