1,721,026 research outputs found
An optimization procedure based on thermal discomfort minimization to support the design of comfortable net zero energy buildings
No full textThe European standard EN 15251 specifies design criteria for dimensioning of building systems. In detail, it proposes that the adaptive comfort model is used, at first, for dimensioning passive means; but, if indoor operative temperature does not meet the chosen long-term adaptive comfort criterion in the “cooling season”, the design would include a mechanical cooling system. In this case, the reference design criteria are provided accordingly the Fanger comfort model. However, there is a discontinuity by switching from the adaptive to the Fanger model, since the best building variant, according to the former, may not coincide with the optimal according to the latter.
In this paper, an optimization procedure to support the design of a comfort-optimized net zero energy building is proposed. It uses an optimization engine (GenOpt) for driving a dynamic simulation engine (EnergyPlus) towards those building variants that minimize, at first, two seasonal long-term discomfort indices based on an adaptive model; and if indoor conditions do not meet the adaptive comfort limits or analyst’s expectations, it minimizes two seasonal long-term discomfort indices based on the Fanger model. The calculation of such indices has been introduced in EnergyPlus via the Energy Management System module, by writing computer codes in the EnergyPlus Reference Language.
The used long-term discomfort indices proved to provide similar ranking capabilities of building variants, even if they are based on different comfort models, and the proposed procedure meets the two- step procedure suggested by EN 15251 without generating significant discontinuities.The European standard EN 15251 specifies design criteria for dimensioning of building systems. In detail, it proposes that the adaptive comfort model is used, at first, for dimensioning passive means; but, if indoor operative temperature does not meet the chosen long-term adaptive comfort criterion in the "cooling season", the design would include a mechanical cooling system. In this case, the reference design criteria are provided accordingly the Fanger comfort model. However, there is a discontinuity by switching from the adaptive to the Fanger model, since the best building variant, according to the former, may not coincide with the optimal according to the latter. In this paper, an optimization procedure to support the design of a comfort-optimized net zero energy building is proposed. It uses an optimization engine (GenOpt) for driving a dynamic simulation engine (EnergyPlus) towards those building variants that minimize, at first, two seasonal long-term discomfort indices based on an adaptive model; and if indoor conditions do not meet the adaptive comfort limits or analyst's expectations, it minimizes two seasonal long-term discomfort indices based on the Fanger model. The calculation of such indices has been introduced in EnergyPlus via the Energy Management System module, by writing computer codes in the EnergyPlus Reference Language. The used long-term discomfort indices proved to provide similar ranking capabilities of building variants, even if they are based on different comfort models, and the proposed procedure meets the two step procedure suggested by EN 15251 without generating significant discontinuities
The Italian energy saving obligation to gas and electricity distribution companies. Scenario and case studies calculations show high environmental and economic benefits to actors (DISCOs, ESCOs, customers) and society
No full textAnalisi critica degli indicatori per la valutazione del comfort termico indoor
Full text linkOggetto del contratto è l’analisi critica degli indicatori proposti dalla norma UNI EN 15251:2008 per valutare attraverso misura o calcolo le condizioni termiche generali del clima degli ambienti interni; in particolare essa consiste in un’analisi comparata degli indicatori di lungo termine applicati alla valutazione del comfort termico durante la stagione estiva. Gli indici di valutazione di lungo periodo sono strumenti utili sia per la valutazione in esercizio delle condizioni di comfort termico in edifici esistenti, sia per guidare il processo di ottimizzazione del progetto di un nuovo edificio, sia per ottimizzare il funzionamento degli impianti termici. Focalizzandosi esclusivamente al periodo estivo, gli indici di valutazione di lungo periodo delle condizioni di comfort termico proposti dalla norma UNI EN 15251:2008 sono stati usati per valutare 54 differenti varianti di un ampio edificio per uffici di riferimento localizzato in diverse città italiane caratterizzate da differenti condizioni climatiche. Le 54 varianti dell’edificio sono state ottenute combinando quattro parametri di riferimento dell’involucro edilizio assumendo due o tre differenti livelli di prestazione per ogni parametro. Tuttavia gli indicatori proposti dalla norma UNI EN 15251 restituiscono diversi risultati, a volte anche in contrasto, a causa del fatto che alcuni considerano nella valutazione del discomfort solo il surriscaldamento ambientale, mentre altri anche il sottoraffreddamento e se cambia il modello di comfort rispetto al quale vengono calcolati gli indicatori. Tutti gli indici analizzati in questo lavoro dipendono dalle categorie di comfort, ma sono disponibili in letteratura altri indici che invece non dipendono dalle categorie di comfort, ma magari solo da una temperatura fissa generalmente usata come estremo superiore della zona di comfort. Invece, sotto il profilo progettuale, l’analisi condotta ha permesso di identificare alcuni parametri di progetto che maggiormente influenzano la valutazione del discomfort termico. In particolare si è individuato che la ventilazione naturale notturna è il parametro che maggiormente influenza il condizioni termiche dell’edificio e quindi ha il maggiore impatto sul comfort termico e un’efficace protezione solare delle superfici trasparenti aumenta sempre il comfort durante il periodi estivo, anche se il suo potenziale è minore di quello della ventilazione notturna (almeno nei climi analizzati in questo lavoro e relativamente alle tipologie edilizie considerate, in cui il rapporto superfici vetrate/superfici opache non è particolarmente elevato). L’aumento dell’isolamento termico e la diminuzione della permeabilità all’aria dell’involucro possono ridurre in estate il comfort termico interno, ma solo se le superfici vetrate non sono opportunamente schermate e se non è implementata una strategia di ventilazione notturna adeguata. In generale evacuare i carichi termici estivi attraverso le pareti (e quindi peggiorarne il comportamento invernale) appare come una strategia errata se questi carichi possono essere controllati con le protezioni solari e smaltiti efficacemente con la ventilazione notturna, con vantaggi dal punto di vista energetico e di comfort. L’aumento della massa termica dà benefici in tutti i contesti climatici analizzati, con un beneficio marginale che si riduce all’aumentare della massa oltre certi valori
The Framework for control of the consumption trends and energy management activities in Italy
No full textTechnical and economic assessment of a battery storage system for a nZEB in the Mediterranean climate
Full text linkIn recent years, the promotion of nearly-Zero Energy Buildings (nZEB), has become a priority for European member states. In order to get this label, typically, a monthly or yearly energy balance of energy use through the exploitation of renewable energy sources (RES) is required, but not a hourly balance. This approach may determine a low exploitation of the RES on site in the case of solar and wind energy, because they are intermittent by nature. Moreover, energy production and energy use peaks are often in mismatch during the day. Battery energy storage systems (BESS) offer a solution to better integrate RES into buildings as well as into the grid, increasing its reliability and minimizing interactions. The cost of these systems is rapidly decreasing, opening new economic opportunities for investors. However, for many applications they do not yet represent the optimal cost-effective solution due to the lifespan of their short-lived components. The paper investigates the technical and economic feasibility of integrating a BESS into a high-performance residential building in the Mediterranean climate based on the outcomes of an original case study based research. The existing photovoltaic system combined with the BESS may substantially optimize the energy use, maximizing the self-consumption and minimizing grid interactions; nevertheless, the pay-back time may become fully-attractive for the analysed building, only if BESS costs will halve by 2030
Mercati dell’energia, efficienza economica ed efficienza energetica negli usi finali
No full textn. 4/200
Decreti per l’efficienza negli usi finali di energia. Costi e benefici per i vari attori coinvolti nel meccanismo
No full textPresent and future potential of natural night ventilation in nZEBs
Full text linkThe increase in the energy need for cooling is one of the major challenges in nearly Zero Energy Buildings. Recent constructions are characterized by high thermal insulation levels, which can be effective in preventing summer discomfort in combination with accurate control of solar gains through glazed surfaces and discharge of overall gains via ventilation. In addition, urbanization, densification and the global warming trends registered in the last decades can increase the risk and magnitude of overheating effect if an accurate design and use of correct technologies and good practices are not considered. The paper investigates the effects and the potential of natural night ventilation, as a strategy to reduce the energy need for cooling even taking into account the evolution of surrounding urban area with the exacerbation of urban heat island under future weather projections. Among the different tools available for the assessment of the cooling potential in buildings, the research focuses on two methodologies, which are adaptable to the conceptual design phase, where a first approximation of the natural ventilation potential is required. The study is developed on the weather datasets referred to the area of Milan and shows the future evolution of the night cooling potential, highlighting the importance of orienting building design towards greater integration between different passive cooling strategies for the summer period
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