Моделирование притока тепла от солнечной радиации через решеточные смарт-окна

Разработан метод расчёта притока тепла от солнечной радиации для помещений с решеточными смарт-окнами с целью дальнейшей оценки влияния на функционирование систем ОВК. Получены формулы для расчёта коэффициентов пропускания прямой и диффузной солнечной радиации через смарт-окна с учётом геометрических параметров двух решёток фильтра. На основе коэффициентов пропускания рассчитывается первичная составляющая теплопритока от солнечной радиации, непосредственно прошедшая через решёточное смарт-окно, в виде суммы прямой и диффузной радиации. Вторичная составляющая теплопритока от поглощённой оконными стеклами солнечной радиации в виде излучения, а также поток тепла за счёт теплопередачи, рассчитываются известными методами, как и для помещений с обычными смарт-окнами. Разработанный метод апробирован с помощью численного моделирования в условиях города Оренбурга для одного выбранного хромогенного материала для обеих решёток фильтра. Предварительно выявлены некоторые преимущества и недостатки решёточных смарт-окон по сравнению с обычными

A parametric sensitivity analysis of the impact of built environment geometrical variables on building energy consumption

The growth of urban communities creates the need for analytical frameworks that have a multiobjective and holistic approach. It is important to integrate these frameworks within commonly used architectural tools. The urban environment is mostly designed and formed by architects and urban planners who can create more sustainable urban growth. In this paper, urban geometry will be explored as it has a significant influence on the building heat loss/gain that determines the energy demand needed to achieve indoor thermal comfort. Simulation tools have been created to analyse and optimize urban geometrical variables in a multiobjective approach. This study analysed urban geometrical variables such as (height, capacity, orientation and window to wall ratio). In addition, it gives an insight of the buildings’ inter-shadowing effect by adding the context buildings’ capacity in the grid. The results show that daylighting analysis consumes almost triple the time using multi-objective, multi-zone geometrical iterations. In this set of inputs for hot arid climates there is a minor impact on cooling energy consumption, suggesting that the study daylighting distribution should be postponed to a later design stage rather being a key component of energy analysis in early design stage. This study shows that WWR has the highest impact on the building thermal cooling consumption in this urban context, then comes built area ratio and finally building height for midrise residential buildings

Proposal for Prioritizing the Retrofitting of Residential Buildings in Energy Poverty Circumstances

The energy poverty derived from socio-economic imbalances affects mostly households with fewer economic resources, being social housing complexes one of the most vulnerable sectors. The insufficient access to energy and the incapability to maintain dwellings at an adequate temperature can have negative impact on people’s health due to the prolonged exposure to poor hygrothermal conditions. Therefore, the prioritization of building retrofitting actions must be carried out regarding the actual state of the housing and the family economy. This paper proposes the definition of a prioritization map that gave a general knowledge of the energy vulnerability situation of the existing building stock. To this end, the dwelling’s energy performance is analysed, focusing on the correlation among its characteristics and the energy vulnerability of its inhabitants. In this way, dwellings with high energy poverty potential are identified in order to develop different energy retrofitting strategies. By applying this method to 14 case studies of social housing in Bilbao, Spain, it was obtained a prioritization map with six levels of vulnerability that can serve as a tool for public entities to design their future strategies. It has been proven that building compactness and year of construction are important factors with a great impact on the heating demand and final consumption in dwellings. Acknowledging the vulnerability context of the building stock eases the decision-making process and the definition of intervention guidelines, prioritizing those in a situation of greater vulnerability

Setting intelligent city tiling strategies for urban shading simulations

Assessing accurately the solar potential of all building surfaces in cities, including shading and multiple reflections between buildings, is essential for urban energy modelling. However, since the number of surface interactions and radiation exchanges increase exponentially with the scale of the district, innovative computational strategies are needed, some of which will be introduced in the present work. They should hold the best compromise between result accuracy and computational efficiency, i.e. computational time and memory requirements. In this study, different approaches that may be used for the computation of urban solar irradiance in large areas are presented. Two concrete urban case studies of different densities have been used to compare and evaluate three different methods: the Perez Sky model, the Simplified Radiosity Algorithm and a new scene tiling method implemented in our urban simulation platform SimStadt, used for feasible estimations on a large scale. To quantify the influence of shading, the new concept of Urban Shading Ratio has been introduced and used for this evaluation process. In high density urban areas, this index may reach 60% for facades and 25% for roofs. Tiles of 500 m width and 200 m overlap are a minimum requirement in this case to compute solar irradiance with an acceptable accuracy. In medium density areas, tiles of 300 m width and 100 m overlap meet perfectly the accuracy requirements. In addition, the solar potential for various solar energy thresholds as well as the monthly variation of the Urban Shading Ratio have been quantified for both case studies, distinguishing between roofs and facades of different orientations

URBAN FACADE GEOMETRY ON OUTDOOR COMFORT CONDITIONS: A REVIEW

Designing urban facades is considered as a major factor influencing issuessuch as natural ventilation of buildings and urban areas, radiations in theurban canyon for designing low-energy buildings, cooling demand forbuildings in urban area, and thermal comfort in urban streets. However, sofar, most studies on urban topics have been focused on flat facadeswithout details of urban layouts. Hence, the effect of urban facades withdetails such as the balcony and corbelling on thermal comfort conditionsand air flow behavior are discussed in this literature review. Aim: Thisstudy was carried out to investigate the effective factors of urban facades,including the effects of building configuration, geometry and urbancanyon’s orientation. Methodology and Results: According to the results,the air flow behavior is affected by a wide range of factors such as windconditions, urban geometry and wind direction. Urban façade geometrycan change outdoor air flow pattern, thermal comfort and solar access.Conclusion, significance and impact study: In particular, the geometry ofthe facade, such as indentation and protrusion, has a significant effect onthe air flow and thermal behavior in urban facades and can enhanceoutdoor comfort conditions. Also, Alternation in façade geometry canaffect pedestrians' comfort and buildings energy demands

La radiación solar en el Ensanche de Barcelona: estudio tipológico de la radiación solar en las fachadas del Ensanche de Barcelona a través de un recorrido por las distintas ordenanzas urbanísticas

Las sucesivas modificaciones de las ordenanzas urbanísticas desde el año 1860 hasta el 1976, supusieron el aumento de la edificabilidad, hasta tres veces superior a la proyectada por Cerdà, en el ensanche de Barcelona. El aumento de la edificabilidad geométricamente se traducía en el aumento de la altura máxima edificable y la profundidad construible. Suponiendo una disminución del factor de vista de cielo y de la radiación solar. La disminución del factor de vista tiene su repercursión en la iluminación natural en el interior de las edificaciones, siendo la geometría la que determiana la porción de cielo vista desde un punto. En el caso de la radiación, disminuyendo la eficacia de los sistemas pasivos de captación. Pero en el caso de la radiación, no sólo vendrá determinada por la geometría del volumen que producirá el enmascaramiento, sino que también influirá el recorrido solar y la orientación. En la tesina se desarrolla un estudio tipológico de la radiación solar y del factor de vista en las fachadas del ensanche de Barcelona a través de un recorrido por las distintas ordenanzas urbanísticas

Photovoltaic potential in building façades

Tese de doutoramento, Sistemas Sustentáveis de Energia, Universidade de Lisboa, Faculdade de Ciências, 2018Consistent reductions in the costs of photovoltaic (PV) systems have prompted interest in applications with less-than-optimum inclinations and orientations. That is the case of building façades, with plenty of free area for the deployment of solar systems. Lower sun heights benefit vertical façades, whereas rooftops are favoured when the sun is near the zenith, therefore the PV potential in urban environments can increase twofold when the contribution from building façades is added to that of the rooftops. This complementarity between façades and rooftops is helpful for a better match between electricity demand and supply. This thesis focuses on: i) the modelling of façade PV potential; ii) the optimization of façade PV yields; and iii) underlining the overall role that building façades will play in future solar cities. Digital surface and solar radiation modelling methodologies were reviewed. Special focus is given to the 3D LiDAR-based model SOL and the CAD/plugin models DIVA and LadyBug. Model SOL was validated against measurements from the BIPV system in the façade of the Solar XXI building (Lisbon), and used to evaluate façade PV potential in different urban sites in Lisbon and Geneva. The plugins DIVA and LadyBug helped assessing the potential for PV glare from façade integrated photovoltaics in distinct urban blocks. Technologies for PV integration in façades were also reviewed. Alternative façade designs, including louvers, geometric forms and balconies, were explored and optimized for the maximization of annual solar irradiation using DIVA. Partial shading impacts on rooftops and façades were addressed through SOL simulations and the interconnections between PV modules were optimized using a custom Multi-Objective Genetic Algorithm. The contribution of PV façades to the solar potential of two dissimilar neighbourhoods in Lisbon was quantified using SOL, considering local electricity consumption. Cost-efficient rooftop/façade PV mixes are proposed based on combined payback times. Impacts of larger scale PV deployment on the spare capacity of power distribution transformers were studied through LadyBug and SolarAnalyst simulations. A new empirical solar factor was proposed to account for PV potential in future upgrade interventions. The combined effect of aggregating building demand, photovoltaic generation and storage on the self-consumption of PV and net load variance was analysed using irradiation results from DIVA, metered distribution transformer loads and custom optimization algorithms. SOL is shown to be an accurate LiDAR-based model (nMBE ranging from around 7% to 51%, nMAE from 20% to 58% and nRMSE from 29% to 81%), being the isotropic diffuse radiation algorithm its current main limitation. In addition, building surface material properties should be regarded when handling façades, for both irradiance simulation and PV glare evaluation. The latter appears to be negligible in comparison to glare from typical glaze/mirror skins used in high-rises. Irradiation levels in the more sunlit façades reach about 50-60% of the rooftop levels. Latitude biases the potential towards the vertical surfaces, which can be enhanced when the proportion of diffuse radiation is high. Façade PV potential can be increased in about 30% if horizontal folded louvers becomes a more common design and in another 6 to 24% if the interconnection of PV modules are optimized. In 2030, a mix of PV systems featuring around 40% façade and 60% rooftop occupation is shown to comprehend a combined financial payback time of 10 years, if conventional module efficiencies reach 20%. This will trigger large-scale PV deployment that might overwhelm current grid assets and lead to electricity grid instability. This challenge can be resolved if the placement of PV modules is optimized to increase self-sufficiency while keeping low net load variance. Aggregated storage within solar communities might help resolving the conflicting interests between prosumers and grid, although the former can achieve self-sufficiency levels above 50% with storage capacities as small as 0.25kWh/kWpv. Business models ought to adapt in order to create conditions for both parts to share the added value of peak power reduction due to optimized solar façades.Fundação para a Ciência e a Tecnologia (FCT), SFRH/BD/52363/201

Urban geometry and environmental performance in real urban forms

Solar radiation is energy, a natural and inexhaustible source of heat and light, and as such a major factor to be considered for enhancing urban environmental sustainability. Solar availability on buildings determines to a large degree their active and passive solar potential; whereas, the insolation of open spaces affects their microclimate and in turn, their use and liveability. Solar objectives are thus multiple and may also be conflicting in time and space, especially in temperate climates, where thermal comfort needs vary in seasons. The subject of the thesis is the relationship between urban geometry and environmental performance of urban forms, explored at the neighbourhood scale and in real urban areas. Specifically, the research investigates statistically casual relationships of urban geometry with environmental phenomena related, directly or indirectly, to the availability of solar radiation. Full consideration is given to the varying solar geometry as a major parameter affecting the interaction between urban geometry and solar radiation, lending it a temporal and geographical -related to latitude- character. The research subject is explored through three distinct studies, which share the same methodology investigating particular topics under the same thematic umbrella. The first and the third study, in the order of these being presented, investigate phenomena occurring in open spaces, namely insolation and thermal diversity; whereas, the second study examines solar availability in open spaces and on building façades. In the methodology, urban geometry is distinguished into built density, which is associated negatively with solar availability but positively with sustainability at the city-scale, and urban layout. The former expresses total built volume in a site, and the latter is represented by a set of quantified geometric parameters which characterise the way in which the built volume is allocated and distributed within the site. This distinction aims to provide evidence for the significance of urban layout in modifying the solar urban environment as well as addressing conflicting solar design objectives. The performance of the urban forms is examined through a series of performance indicators, namely sky view factor, insolation, solar irradiance and thermal diversity values. Both urban geometry variables and performance indicators are calculated on average in each urban form. The great size of the sample analysed allows their relationships to be investigated in statistical means. The research belongs to the new era of urban environmental studies which make use of digital 3D models of cities to study spatially expressed phenomena in the built environment. It is based entirely on the analysis of existing urban forms, of 500x500m area, found in two European cities, London and Paris. London constitutes the main case study city, whereas Paris is examined for comparison purposes. The two cities are located at similar geographical latitudes and within the same climatic context, but their urban fabrics exemplify very different geometries. The geometric and environmental analysis of the urban forms as well as the elaboration and processing of the output data are performed using computer-based tools and methods, such as MATLAB software and image processing techniques applied in urban digital elevation models (DEMs) and, SOLWEIG and the RADIANCE-based software, PPF, for SVF and solar simulations. The research findings contribute to the field of urban environmental studies and design at multiple levels, presenting a significant theoretical, practical, and methodological value. First, they produce a critical insight about the factors affecting the relationship of urban geometry and sun-related phenomena occurring in the urban environment and lending it a dynamic character. In addition, they provide solid evidence about the enormous potential of urban geometry for promoting multiple -and sometimes conflicting- solar and urban design objectives, informing the relevant on-going discourse. Third, having as case studies real forms in London and Paris, a part of the findings is interpreted into urban design guidelines for enhancing the environmental performance of new and existing areas in the two cities. Last, as the research employs new methods and techniques to explore diverse topics, some of which are relatively new in the literature, it constitutes an important, methodological precedent for future research works