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A new framework to switch from Zero Energy to Zero Power Buildings
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From Zero Energy to Zero Power Buildings: A new framework to define high-energy performance and carbon-neutral buildings
Full text linkThe definition of Zero Energy Building (ZEB) has often been controversial both in regulation and research. This work explores a new evaluation framework introducing the Zero Power Building (ZPB) concept, a novel method that studies the relationship of buildings to the physical boundary, weighting system and analysis timeframe,
approaching performance assessment at reduced time intervals. The methodology proposed in this paper showcases how the limitations of the ZEB can be overcome by adopting the ZPB concept on a reference com mercial building. The case study was analysed under two different scenarios, with and without an electric storage system. The application of the ZPB concept on an hourly basis poses a challenge to the case study performance, considering both final energy use and CO2 emissions. Specifically, the building commonly accepted as a ZEB turns as a ZPB for only 54.76% of annual hours and as carbon-neutral building for 55.58% of annual hours. The paper presents an innovative methodology that aims to assist in the design and operation of future buildings, as well as provide guidance for policymakers and regulators. The findings emphasize the significance of using dynamic assessment strategies to accurately evaluate the buildings performances and enable meaningful com parisons in various contexts
The role of Renewable Energy Communities in urban decarbonization and the achievement of Positive Energy Districts
No full textEnergy assessment of a district by integrating solar thermal in district heating network: a dynamic analysis approach
Full text linkThis work focuses on the energy upgrade of a neighbourhood located in Yverdon-les-Bains, Switzerland. Starting from a potential low-temperature district heating network, the possible integration of new buildings equipped with solar thermal collectors capable of interacting with the network is explored. The methodology proposed in this work focuses on the study of the energy balance of the district at reduced time intervals. Bringing the level of detail to every single hour of the year, the concept of energy balance is superseded by the hourly averaged power balance as a specific tool for a detailed exploration of the energy flows exchanged within the district. Self-sufficiency has also been identified as key performance indicators to better understand the ability of the entire district to satisfy its heating and domestic hot water needs, modelled in CitySim's urban energy environment. The outcomes have shown that an annual energy balance is ineffective and unrealistic for describing performances of the district. On the other hand, the hourly averaged power balance proves to be a powerful tool for understanding the dynamics of the neighbourhood. The district's energy flexibility, which relies on energy sharing, is a characteristic that cannot be assessed annually. Using the new proposed methodology to evaluate the district's thermal energy sharing, it was discovered that the district functions as a Zero Energy District for 28.9% of the year. With the outcomes presented in this study, it is now possible to comprehend how a dynamic performance assessment positively impacts a district's redevelopment strategies
Performance assessment and optimization of a solar cooling system to satisfy renewable energy ratio (RER) requirements in multi-family buildings
Full text linkIn order to meet European targets for decarbonisation in 2050, the amount of building energy needs that must be covered through RES is going to increase. Considering the increasing needs for space cooling, mainly due to climate change, technical solutions involving renewable sources of energy for cooling purposes are of great interest. Solar absorption chillers represent a valid answer, but their use in the residential sector is at early stage. This work explores the ability of a solar cooling system to meet the summer energy demand of a multi-family building located in the Mediterranean area. An energy model was developed in TRNSYS® and a simulation-based optimization framework was used to optimize the system design, maximize its energy benefits and relate energy performance to investment and operational costs. The resulting optimal design has reduced the initial non-renewable primary energy demand by 48%, increasing the renewable energy ratio up to 83%. Results demonstrate the ability of the proposed approach to support valuable design choices in this field and reveal the potential of solar cooling to reach the NZEB target in view of future climate change and the future developments of energy requirements for buildings
From Zero Energy to Zero Power Buildings: A new paradigm for a sustainable transition of the building stock
Full text linkThis research introduces an innovative method aimed at evaluating building energy performance within urban environments and communities, departing from the conventional Zero Energy Building (ZEB) concept and introducing the Zero Power Building (ZPB) framework. This approach, overcoming the limitations of the ZEB concept, offers a holistic definition in line with the goal of achieving a Zero -emission Building stock. By employing a power balance assessment coupled with dynamic Key Performance Indicators (KPIs), this methodology surpasses traditional techniques, providing a more accurate assessment of energy consumption and generation patterns. The method was applied to a district case study encompassing seven nearly Zero Energy Buildings (nZEBs), demonstrating its potential efficacy. Findings indicate how the proposed framework can accurately evaluate the integration of energy storage and sharing strategies, increasing the Zero Power target from 29 % to 51 % of annual hours. KPIs were also dynamically examined at the building and district level, introducing the concept of KPI accuracy and identifying pivotal hourly patterns to guide a sustainable transistion. The adoption of the Zero Power Building framework and the utilization of dynamic KPIs offer viable solutions to address conventional limitations in building energy assessments. This approach aids in guiding targeted energy efficiency measures aimed at fostering sustainable and Zero -emission Communities
The role of solar cooling for nearly zero energy multifamily buildings: Performance analysis across different climates
No full textThe building sector has great potential for contributing to the 2030 EU goals of decreasing greenhouse gas emissions and increasing production from renewable sources. This is even more important considering the increasing cooling energy needs. Among the available technologies, solar cooling (SC) represents a good alternative to traditional electric chillers. However, its use in residential buildings is still limited. The aim of this paper is to analyse the potential of solar cooling system in multi-family buildings. A dynamic model of a complete SC system with auxiliary components was developed in TRNSYS to meet the energy demand of a representative nearly zero energy multi-family building in Italy. The performance of different system design alternatives was analysed in eight different climates with special focus on energy storages. The results show how solar cooling should be optimally designed and provide quantification of achievable renewable energy ratios and related costs in the different climates
A numerical model for the energy assessment of a fifth-generation district heating and cooling (5GDHC) network
No full textAchieving the new energy efficiency targets set by recent European directives is not a foregone conclusion for most new building construction projects. The regulatory limits are increasingly stringent and the energy design of buildings becomes more complex and detailed. The transition process towards nearly Zero Energy Buildings (nZEB) now affects almost all European countries, and will be the subject of future challenges in the construction sector. To overcome this problem, not only the role of individual buildings will be crucial, but also the function of future districts, whose cooperation in terms of energy exchange and sharing of resources could be a key aspect to face climate change in a sustainable and efficient way. In this context, a recently studied topic is represented by the fifth generation of low temperature district heating and cooling (5GDHC) networks. The potential of this new generation of thermal networks is to operate at low temperatures, usually below 25 °C, in order to be used as a heat source for the operation of reversible heat pumps, capable of satisfying both heating and cooling needs of the users connected to the network. This feature allows the network users to be prosumers, sharing the heat produced or removed from the network to generate a benefit for other users. Furthermore, this new generation of thermal networks allows an effective integration of renewable sources and low temperature waste heat sources, which can easily be integrated into the network. In this work, a dynamic numerical model has been developed in order to simulate the behaviour of a 5GDHC. A simulation scenario has been defined consisting of 15 different users belonging to the same district and their interaction within the network has been studied. The energy performance of the network was assessed by means of some global performance indexes, with the aim of characterizing the energy potential and response of the network. Thanks to the results presented in this work, it is possible to understand the positive effects of 5GDHC networks, encouraging the spread of this technology and its future application developments
Analisi delle prestazioni energetiche di un impianto solar cooling per la climatizzazione estiva di edifici residenziali multifamiliari
No full textNell’attuale scenario normativo italiano, il 50% del fabbisogno energetico per il riscaldamento, il raffrescamento e la produzione di acqua calda sanitaria di un edificio ad uso residenziale deve essere coperto da fonti rinnovabili ed in futuro, in vista degli obiettivi europei di decarbonizzazione del 2050, si prevede un ulteriore incremento di tale percentuale. Un tale obiettivo è però ostacolato dal progressivo aumento del fabbisogno energetico dell’edificio dovuto all’adozione di sistemi impiantistici per la climatizzazione estiva. Di qui l’interesse verso l’impiego di soluzioni impiantistiche per il raffrescamento degli ambienti che utilizzano fonti rinnovabili. Fra queste vi sono le macchine frigorifere ad assorbimento alimentate da fonte solare (solar cooling).
Nel presente lavoro, a partire dalla domanda energetica di un edificio residenziale multifamiliare, sono state analizzate le prestazioni di un impianto di solar cooling presente sul mercato italiano. Lo studio è stato sviluppato in modo dettagliato attraverso l’ausilio di un software di simulazione termoenergetica dinamica (TRNSYS®).
I risultati ottenuti hanno evidenziato che l’impiego del solar cooling nel settore re-sidenziale presenta indubbi vantaggi dal punto di vista energetico e merita di essere approfondito per gli aspetti di carattere economico – costi di investimento e costi di esercizio – non ancora trattati nel presente lavoro
The role of Primary Energy Factors (PEF) for electricity in the evaluation and comparison of building energy performance: An investigation on European nZEBs according to EN 17423:2020
Full text linkEvaluating the energy performance of buildings is a fundamental aspect for quantifying the impact of national energy policies supporting energy transition and sustainable development of countries. However, evaluations carried out on final energy consumption risk leading to approximate solutions that do not take into account the generation, transmission and distribution efficiency of energy systems. Furthermore, it is increasingly difficult to compare similar buildings that belong to different geographical contexts. To overcome these problems, a common solution, that is adopted at European and international level, is the use of the concept of primary energy, and the relative primary energy factor (PEF). The current assessment of primary energy for the performance of European buildings is governed by individual national laws, which are often out-to-date and not representative of current national energy systems. In this work, the recent EN 17423:2020 standard was adopted to apply a harmonized methodology in the evaluation of PEF for different European countries, considering the electricity energy vector. The results demonstrated first an important variation in the primary energy factor over the last 20 years, with decreases from -7% (in France) to -32% (in Denmark). Using this methodology, the primary energy needs of 37 European representatives nearly Zero Energy Buildings (nZEBs), located in 11 different member countries, were assessed. For the first time in literature, it was possible to compare European buildings energy performance following a standardized assessment procedure. The implications of this work represent a starting point for comparisons on the European building stock, also indicating the need for an update of national regulations regarding the assessments of the energy performance of buildings
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