1,720,994 research outputs found
The calibration process of building energy models
No full textThe importance of model calibration has been growing up as a result of the energy refurbishment policy promoted by the recast Energy Performance of Buildings Directive (EPBD 2010/31/EU). In fact, with the purpose of ensuring a suitable refurbishment design with effective energy conservation measures (ECM), an accurate model has to be defined in order to assess the energy behaviour of the as-built building. In this chapter, some issues related to the model calibration are presented, starting from the definition of an operative procedure step by step. Furthermore, for the most critical phases of the procedure, analysis techniques and experimental methods are described both through theory and practical examples. Finally, throughout the chapter, the analysis of a case study is presented
Assessing the energy flexibility of building clusters under different forcing factors
No full textGiven the increasing penetration of variable renewable resources in energy networks, future buildings should become flexible, i.e., able to modify their energy demands in response to external forcing factors to pursue specific goals. Furthermore, strong interaction among interconnected prosumer buildings and energy systems will require flexible energy management strategies at cluster level. Accordingly, this study implements the IEA EBC Annex 67 approach and proposes a quantification methodology to assess the energy flexibility performance of building clusters. The availability of renewable energy sources and carbon intensity in the energy mix are selected as forcing factors and a rule-based control scheme is applied to the space heating set-point to exploit thermal storage in the building structure. Specific indicators are defined to quantify flexibility as (i) a reduction in energy demand not covered by renewables or (ii) a percentage decrease in carbon emissions enabled by smart control of the cluster, compared to a reference scenario. The methodology is applied to four cluster configurations characterized by different building thermal mass levels, modeled in Dymola dynamic simulation environment. Results show that smart operation for simulated clusters enables an improvement of renewable energy usage (up to a 13% saving of the residual annual heating demand), and up to an 18% reduction of energy-related carbon emissions. The suggested quantitative assessment and indicators represent valuable support for building designers to easily compare multiple technological solutions and design strategies in terms of energy flexibility
Bottom-up building stock retrofit based on levelized cost of saved energy
No full textPolicy makers need scientific support to set ambitious yet realistic environmental targets for the transition to energy efficient buildings and to develop cost-effective policies to meet these targets, but comprehensive, manageable procedures to this aim are still lacking. Our proposed method ranges from baseline creation to transition scenarios depending on annual retrofit budget and specifies the buildings to renovate according to location, size, and age, and the energy efficiency measures to apply based on cost and energy saving. We show how to extrapolate a baseline from few available data, determine retrofit costs, and create calibrated models to estimate energy savings. Retrofits are ranked by levelized cost of saved energy, which ensures that for any budget allocated to retrofit maximum energy savings are obtained at minimum cost to society. The results are summarized in an energy efficiency cost curve enabling policy makers to estimate potential costs and energy savings. We demonstrate the method on a housing stock in northern Italy and show that facade insulation of old buildings in colder climates can compete with gas heating. About 60% baseline energy consumption can be saved doubling current investments, while a maximum saving of 75% requires over three times the current investments
On the influence of several parameters in energy model calibration: The case of a historical building
No full textThe aim of this work is to investigate the extent to which several different variables (e.g. climate conditions, infiltration rates and envelope characteristics) could affect the calibration process and, consequently, the reliability of the simulation outcomes. In this regard, in this paper the calibration phases of a dynamic hourly energy model for an existing building are presented. The test case is a historical construction built at the end of the nineteenth century in northern Italy. The building, originally designed for tobacco processing, has a massive envelope and it has no HVAC system. Therefore, the simulation model is calibrated using the actual air and wall surface temperature as control variables. Finally, a sensitivity analysis is carried out in order to assess the incidence of different inputs in building thermal behaviour and to identify which parameters have to be refined with the aim of optimizing the model calibration
Assessment of nanoparticle emission in additive manufacturing: Comparing wire and powder laser metal deposition processes
Full text linkAdditive manufacturing (AM), often referred to as 3D printing, is an emerging technology with a wide range of industrial applications and process typologies. Although the release of metal nanoparticles as by-products could occur, occupational exposure limits and cogent safety standards are not currently available due to the novelty of the technology. To support the definition of benchmarks, this study aims to provide a preliminary comparison between the nanoparticle release patterns of laser metal deposition, adopting different feedstocks, namely, metal wire and metal powder. The monitored device is a university research setup, and the work presents the results of two different processes with AISI 316 L as a feedstock in powder and wired form, respectively. The monitoring confirmed the outcomes of previous studies, with a high release of nanoparticles from the powder head on the device (average 138,713 n/cm3 during printing, with maximum values exceeding 106 n/cm3). Moreover, the results show a significant concentration of nanoparticles with a wire head during the printing phase (average release of 628,156 n/cm3 with a maximum of 1,114,987 n/cm3) and pauses (average of 32,633 n/cm3 and a maximum of 733,779 n/cm3). The monitored values during pauses are particularly relevant since no personal protection equipment was used in the wire processes and the operators could access the printing room during pauses for device interventions, thus being exposed to significant nanoparticle concentrations. This study presents a preliminary evaluation of the potential exposure during laser metal deposition while implementing different technologies and provides evidence for defining effective operational safety procedures for the operators
Nearly Zero Energy Buildings: An overview of the main construction features across Europe
No full textNearly Zero Energy Buildings (nZEBs) represent the backbone to achieve ambitious European goals in terms of energy efficiency and CO2 emissions reduction. As defined in the EPBD, by 31 December 2020, all of the new buildings will have to reach a target of nearly zero energy. This target encourages the adoption of innovative business models as well as the technology development in the building sector, aimed at reducing energy demand and exploiting local renewable energy sources (RES). Assessing the share of implementation and the performance of technologies in new or renovated nZEBs is strategic to identify the market trends and to define design guidelines with the most effective solutions according to the context. In this regard, this paper analyses the construction features of a set of nZEBs, collected in 17 European countries within the EU IEE ZEBRA2020 project, with a special focus on the influence of the boundary conditions on the technologies adopted. The results show a general high insulation level of the envelope and recurrent specific technologies in the Heating Ventilation Air Conditioning (HVAC) system (i.e., heat pumps and mechanical ventilation), while the climatic conditions do not drive significantly the design approach and the nZEB features
Towards the definition of a nZEB cost spreadsheet as a support tool for the design
No full textThe 2010 Energy Performance of Buildings Directive (EPBD recast) [1] established that all new buildings have to reach, by the end of 2020, the nearly-Zero Energy (nZEB) target as set by the Member States. In order to achieve the nZEB standards, while keeping investments sustainable, it is strategic to focus more on the operational phase and to guide the decision-support with a lifetime perspective. In this regard, a crucial step is to adopt a shared methodology for evaluating the Life-Cycle Cost (LCC), in order to minimize the effect of uncertainties, the impact of calculation approach and the variability of the boundaries at EU level. The H2020 CRAVEzero project developed a LCC spreadsheet, aimed at calculating a set of relevant indicators for assessing the cost during the investment phase (design, labour and material costs) as well as during the operational phase of a building (energy and maintenance costs). The LCC spreadsheet implements an approach for normalising the results according to the main relevant boundaries that can affect the comparability at EU level (e.g. energy prices, the national construction costs, the climatic conditions, etc.). Moreover, it introduces a sensitivity analysis that aims to provide the impact that the boundary conditions can have on the results, reducing the uncertainties in the LCC calculations due to a long-term perspective (http://www.cravezero.eu/lcc spreadsheet/). This paper presents the structure of the LCC calculation approach defined within the project, the structure of the spreadsheet and the main indicators as evaluated for a set of relevant nZEB case studies across Europe
New domain for promoting energy efficiency: Energy Flexible Building Cluster
No full textThe ongoing energy system shift—from traditional centralized fossil fuel based to decentralized renewable energy sources based—requires a strengthened control of energy matching. Smart buildings represent the latest step in building energy evolution and perform as active participants in the cluster/energy infrastructure scale, becoming energy prosumers. In this framework, the IEA EBC Annex 67 introduces the concept of ‘Energy Flexible Building’ defined as a building able to manage its demand and generation in accordance with local climate conditions, user needs and grid requirements. Currently, there is no insight into how much flexibility a building may offer, and this study aims to overview the theoretical approaches and existing indicators to evaluate the Energy Flexibility of building clusters. The focus on cluster scale allows for the exploitation of the variation in energy consumption patterns between different types of buildings and the coordination of load shifting for the improvement of renewable energy use. The reviewed indicators can contribute to the definition of the Smart Readiness Indicator, introduced in the European Commission proposal for the EPBD revision, in order to test a building's technological readiness to adapt to the needs of the occupants and the energy environment, as well as to operate more efficiently
Office occupants’ perspective dealing with energy flexibility: A large-scale survey in the province of bolzano
No full textThe current energy system is dealing with an increasing share of renewable energy that, because of its intermittent availability, can affect the effectiveness of the energy supply. To cope with the problem, buildings need to become energy flexible. According to the definition given by IEA EBC Annex 67, energy flexibility is the ability of a building to manage its demand and generation according to local climate conditions, user needs and grid requirements. Users of energy-flexible buildings play a crucial role for an effective implementation, thus user acceptance and proper behaviour are important factors. In order to understand the current level of awareness on the topic and the general acceptance of the users, this paper presents the results of a large-scale survey distributed in the office buildings of the Province of Bolzano (Italy). This study investigates the information, experience, beliefs, and desires of the building users (i.e., office employees) with concepts and technologies dealing with energy flexibility, such as smart grids, smart appliances, and smart meters. This study identifies (i) the main socio-demographic characteristics associated to the information and desires about energy flexibility in office buildings, and (ii) the main conditions of social acceptance of flexible energy usages. Although this work is focused on a specific user type (i.e., office workers in the Province of Bolzano) and the results cannot be generalized, the analysis offers an interesting insight on the user perspectives and acceptance on energy flexibility and can be easily replicated. The results can be used at local level to provide insights for policies and strategies to encourage building users to be more flexible
Analysis of the building smart readiness indicator calculation: A comparative case-study with two panels of experts
No full textThe last release of the Energy Performance of Buildings Directive 2018/844/EU stated that smart buildings will play a crucial role in the future energy systems. Consequently, the Directive introduced the Smart Readiness Indicator in order to provide a common framework to highlight the value of building smartness across Europe. The methodology for the calculation of the Smart Readiness Indicator is currently under development and therefore not yet officially adopted at the European Union level. In this context, the current research analyzed the second public release of the proposed methodology, discussing the feasibility of its implementation and the obtained results through a practical application. Specifically, the methodology was applied to a nearly zero-energy office building located in Italy, and the evaluation was carried out in parallel by two different expert groups composed by researchers and technical building systems specialists. With the aim of analyzing the impact of subjective evaluations on the calculated indicator, a two-step assessment was adopted: in a first phase the two groups worked separately, and only in a second phase they were allowed to compare results, discuss discrepancies and identify the difficulties in applying the methodology. As the main outcome of this research, a set of recommendations are presented for an effective broad implementation of the Smart Readiness Indicator, able to increase the relevance of its evaluation and effectiveness, as well as to enhance the comparability of smart readiness of buildings through the definition of benchmarks and to integrate with other measurable key indicators, especially concerning energy flexibility
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