1,720,975 research outputs found
Computational aspects of modeling different strategies for kitchen ventilation: a comparison between the multi-zone approach and CFD modelling with reference to predicted indoor pollutant concentrations
No full textThis paper deals with the evaluation of different simulation approaches to kitchen ventilation modelling. Multi-zone, CFD and zonal approach are discussed.
The investigation moves its steps from the analysis of a controlled ventilation system intended for individual and collective housing. The question of natural ventilation being able of ensuring ventilation rates consistent with acceptable indoor air quality is dealt with. Buildings have become increasingly airproof and natural ventilation, as it will be presented, may result inadequate. It follows that ensuring a proper airflow by mechanical means is necessary to provide occupants with good IAQ. The analyzed ventilation system supplies the main rooms (living rooms and dining rooms) with fresh air. Air sweeps through the occupied space and eventually is extracted by means of grilles located in the technical rooms such as kitchens and bathrooms, i.e. the rooms that are the most polluted as a result of every day life. The objective is to develop a design model suitable for long term, whole year, analysis that is able to offer advantages over multi-zone models without the issues associated with CFD modelling. Different flow scenarios have been tested. Well mixed and zonal modelling results have been compared to CFD predicted pollutant distribution which has been used as reference solution. CFD simulations have been validated by means of literature available experimental data. Sensitivity analysis has been performed to determine the impact of various modelling parameters on the accuracy of the simulation. In particular, the influence of capturing local effects, such as the plume rising from the cooking range, is presented
The Use of Ceiling Fans in Reverse-Flow Mode for Comfort Cooling: Physiological Aspects and Relationship with International Standards
No full textIn a warming planet, the energy demand for space cooling is constantly increasing. Air movement can be considered an energy efficient mean to provide thermal comfort in warm season. Ceiling fans are among the most adopted sources of air movement in buildings, and they are widely used in many countries. In warm environmental conditions, ceiling fans usually blow air from the ceiling to the occupants. While the heat generated from a human body does not vary, this forced convection accelerates the heat transfer between the parts of the body skin hit by the air flow and the surrounding thermal environment. The elevated air speed increases the convective heat transfer coefficients and the rate of evaporation from those parts of the skin. In cold seasons, ceiling fans are often used in reverse-flow mode for destratification purposes. In this case, the air speed is usually much lower than the direct flow, but considerably more uniform in the room. Some manufacturing companies lately raised their interest in analyzing the reverse-flow as a means to provide thermal comfort also in summer, providing a gentler airflow that might be less likely to cause draft for the users. Hence, the aim of this study is to investigate the extent to which the reverse-flow could be used also for cooling in warm conditions. CFD simulations were used to evaluate (i) the air speed field generated using direct and reverse flow (magnitude and spatial distribution), and (ii) how the heat transfer coefficients on the different body parts vary in both cases. The former enables to provide thermo-physiological insights, while the latter a comparison with air speed values reported in standards such as ASHRAE55. The results indicate that, although more evenly distributed within the room, the generated air speed with the reverse flow is considerably low. Hence, from a physiological point of view, it would not be sufficient to provide comfort cooling. Further work with human participants will investigate whether this low speed might generate a subjective perception of comfort cooling
The challenge of archetypes representativity for wide scale building investigation in Italy
No full textOffice 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
Product traits, decision-makers, and household low-carbon technology adoptions: moving beyond single empirical studies
No full textAlthough single empirical studies provide important insights into who adopts a specific LCT for what reason, fundamental questions concerning the relations between decision subject (= who decides), decision object (= what is decided upon) and context (= when and where it is decided) remain unanswered. In this paper, this research gap is addressed by deriving a decision framework for residential decision-making, suggesting that traits of decision subject and object are determinants of financial, environmental, symbolic, normative, effort and technical considerations preceding adoption. Thereafter, the decision framework is initially verified by employing literature on the adoption of photovoltaic systems, energy efficient appliances and green tariffs. Of the six proposed relations, two could be confirmed (financial and environmental), one could be rejected (effort), and three could neither be confirmed nor rejected due to lacking evidence. Future research on LCT adoption could use the decision framework as guidepost to establish a more coordinated and integrated approach, ultimately allowing to address fundamental questions
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
A framework to support the design of a regenerative indoor environment
No full textIn recent decades, a new generation of “green indoor” spaces has fulfilled the latest regulations and guidelines for a carbon-neutral society. Their targets are reachable through certifications embracing sets of measures and the adverse effects on occupants. Notwithstanding this, it has constituted a significant step forward in building design. However, the challenges given by climate change and the ecological crises lead to the need for new disruptive approaches to indoor design and function, enhancing human health and adopting regenerative design” at the forefront of buildings’ conception. Besides the positive energy-performance attributes, the creation of a Regenerative Indoor Environment utilizes appropriate construction technologies and systems, to reinforce human health, and enhance users’ experience. This regenerative paradigm shift foresees putting ecosystems at the centre and the users’ psycho-physiological wellbeing, thus magnifying their collaboration. Despite regenerative design gaining some attention, a framework towards its implementation promoting the actual performances of the indoor environment is still missing, and designers do navigate among guidelines with no apparent performance indicators to be achieved, technologies to be implemented, or methodologies for post-occupancy evaluations. These three levels, constituting a stepwise methodology, are addressed by the authors within the sections of this paper, and validated as an example of the office buildings’ typology. i) What characterizes a Regenerative Indoor Environment? ii) What technical solutions underpin the realization of a Regenerative Indoor Environment? iii) What methods or standards are crucial for its evaluation? With these premises, the paper contributes to supporting the creation of a regenerative indoor’ design, by sampling and outlining regenerative indoor performances to be obtained, describing the adequate tools to implement them, as well as by displaying approaches and solutions for their final verification
Unlocking thermal comfort in transitional spaces: A field study in three Italian shopping centres
Full text linkShopping centres are commonly laid out as small individual stores connected by transitional spaces. Setpoint temperatures used to control transitional spaces are normally the same as in traditional indoor environments despite substantial differences in use, time of permanence and users' needs. Currently, there are no comfort guidelines for transitional spaces and the literature lacks relevant studies on the topic. There is an untapped potential for energy savings and improved indoor environmental quality. The main objective of this work is to evaluate the suitability of Fanger's comfort model and adaptive comfort model for transitional spaces. We assessed users' thermal perception and potential impacting factors in three Italian shopping centres. 724 customers were interviewed on their thermal comfort, thermal sensation, thermal preference, and clothing level while experiencing the transitional space. In addition, the thermal environment at the interview locations (dry-bulb temperature, globe temperature, relative humidity, and air speed at different levels) and the outdoor temperature were monitored. The study demonstrated that Fanger's model and the adaptive comfort model are not suitable for transitional spaces. Customers were inclined to adapt to a much wider range of indoor environmental conditions. An operative temperature of up to 27.5 °C was still deemed comfortable by more than 80% of the customers. These results unlock a large potential for energy savings and pave the way for passive solutions such as natural ventilation
A model to simulate the energy consumption of the Italian residential building stock with regional resolution
No full textDevelopment of climate-based thermal comfort ranges from existing data: Analysis of the Smart Controls and thermal comfort (SCATS) database
Full text linkDespite the multifaceted nature of notion of thermal comfort, designers have embraced a very strict definition of it, which consists of very tight and static environments, were transition and stimuli are not admitted, and with very narrow ranges of microclimatic parameters required equally for all the subjects. This neglects all the potential implications related to different users. However, when it comes to thermal comfort, the long-term history of subjects and their climatic background play a pivotal role towards their own thermal sensations and preferences. In this work, to address these diversities, the authors analysed the existing database of the Smart Controls and Thermal Comfort (SCATS) project, which was built from monitoring and survey campaigns conducted in the late 90s in five different European countries. Data were studied by means of statistical techniques to grasp and define the potential combined influence of climatic location, seasonal variations, subjective variables and ventilation modes on the occupants’ thermal feeling and preference. Different scenarios recommended by standard EN 16798 were tested to address the differences in the thermal feelings of users living in different European countries. Finally, country-based operative temperatures that optimize users’ thermal feeling and preference were determined. Results highlight that users in different countries differently evaluate indoor thermal parameters both in terms of thermal feeling and thermal preferences. This results in differences among countries for acceptability levels associated with standardised indoor conditions. Furthermore, the results highlight the importance of air movement to improve acceptability at higher indoor temperatures for all the countries
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