UDC7: Buildings climate and energy consumption II : temperate and cold climate cities
URBAN MICROCLIMATE AND BUILDING ENERGY: A COUPLED SIMULATION APPROACH
1EDF R&D EnerBaT, Moret-sur-Loing, France; 2CNRS CERMA,, Nantes, France; 3HPC SA, Toulouse, France
Nowadays, a large share of buildings are built in urban context. Therefore the various interactions between buildings and their urban environment should be carefully considered when dealing with building energy or micro-climate simulation. A building is exposed to a local microclimate, surrounded by other buildings that mask solar inputs and/or trap long wave radiation. On the other hand, the microclimate is very sensitive to anthropogenic heat gains from HVAC systems and roughness of urban canopy.
In addition, one of the main concept for low-energy or passive buildings is to rely massively on free heating and cooling ressources, such as solar, occupancy and outdoor air to satisfy their needs. As a consequence they are much more insulated to decrease their needs. From a certain point of view, they are paradoxically disconnected from their environment but also very sensitive to outdoor air, solar and long wave radiation through windows and ventilation.
Therefore, when designing a new building in the early stages it is important to take into account its interactions with surronding buildings and the microclimate. It supports optimization of the building’s energy performance in more realistic conditions as the one of the overall district. Consequently, there is a strong need for tools capable of performing urban energy simulation taking into account buildings and their surroundings based on available data.
The French ANR project MERUBBI aims at developing an interdisciplinary method based on building energy, radiation, microclimate and economics analysis. Assessments of various indicators, for resources exploitation and economics consideration for instance are then carried out for optimizing the overall system.
In that context, we developed a tool-coupling framework between BuildSysPro, EDF’s Modelica library for building energy simulation, Solene-Microclimat, a urban microclimate simulation tool developed by the CERMA and ArchiWizard, a ray-tracing solution from HPC SA.
We applied our methodology on a real district, the test case being the construction of a new building in the already existing district of Nantes Ranzey in France, composed of 25 buildings. The process was unfold from the architectural plan taken from the cadastre to the Modelica energy simulation. The results show a 20% increase in annual heating demand compared to the same building in a remote location used as reference.
The urban heat island and its influence on building energy consumption in England and South Korea
1The University of Manchester, School of Mechanical, Aerospace and Civil Engeineering,United Kingdom; 2School of Space Design, Ulsan College, South Korea; 3The University of Manchester, School of Mathematics, UK
This paper examines the measurements of the urban heat island in a number of sites around Manchester, England, UK and also Ulsan in South Korea. The measurements and the actual weather are considered and compared and the possible reasons for the different urban heat islands are discussed. Although a significant urban heat island intensity (UHII) is found in the UK site it is not as high as the intensity in South Korea. However, the UHII is steadily rising in the UK but it is not in South Korea. A number of identical commercial office buildings are then simulated with and without the UHII added. The increase in energy consumption in the warm periods is increased by the UHII by about 8% in the UK and almost 20% in South Korea. The heating in cooler periods is consequently reduced but not by as much as the summer cooling. The glazed area of the buildings is also influential in the energy used.
Assessment of urban cooling strategies impact using a coupled model for urban microclimate and building energy simulation
1University of La Rochelle, LaSIE FRE CNRS 3474 (France); 2Institut de Recherche des Sciences et Techniques de la Ville (France)
The EVA project is being carried out to evaluate the cooling efficiency of three types of systems:
• Vegetation (tree, green wall and green roof),
• Water (watering road),
• High albedo values (Cool paint on walls or roof).
This study is realized thanks to two numerical modelling scales. The first one is a district scale while the second is a higher scale containing several districts in order to evaluate the impact of districts on one another. Three models are used for this study: Solene-microclimat (Malys, Musy, et Inard 2014), EnviBatE (Gros, Bozonnet, et Inard 2011) and ARPS-canopy (Maché 2012).
The assessment of these different strategies is applied to an existing district: Part-Dieu in Lyon, France. This district has a high urban density and is composed of buildings which rehabilitation is expected to be difficult. It is particularly sensitive to summer heat waves which frequency of occurrence will increase with global warming. Three places were chosen for this study: Moncey Street, Francfort place and Buire Street.
Two different methods are used to evaluate the cooling efficiency of each strategy. The first consists in studying different urban planning corresponding to each type of system. The second one is to study a single urban planning but with climatic data that take global warming into consideration. The systems will be evaluate by studying their impact one microclimate (microclimatic variables and outdoor comfort), on indoor comfort and building energy demand.
In this paper we present the results obtained with the EnviBatE model. Among the three places, two will be evaluated using EnviBatE: Moncey Street and Buire Street. They represent respectively 60.000 m² and 70.000 m² and are composed of about ten building blocks. EnviBatE is used to compute the building energy demand and the microclimate for a seasonal period (from the first of May to the 30th of September). Modellings are realized for standard meteorological data and for data taking into account the global warming .The results show the impact of the different cooling strategies on the urban microclimate and building energy demand.
Outdoor human comfort and climate change. A case study in the EPFL campus in Lausanne
LESO-PB, EPFL, Switzerland
The increase of the population, the growing urbanisation and the climate change are the present challenges for a sustainable urban development. This paper proposes a methodology to study how the microclimate and the analysis of the outdoor human comfort in the built environment can influence the future city design.
The methodology makes use of an Urban Energy Modelling tool to define the energy demand of buildings and the outdoor conditions, considering the energy exchange between pedestrians and the urban microclimate. The model of the EPFL campus in Lausanne (Switzerland) is analysed with the software CitySim and ENVImet, showing the actual energy demand of buildings, the microclimatic map of the site, and the outdoor human comfort according to different biometerological indexes. The dynamic model of the site, in the present scenario, is validated with on-site monitoring: the buildings energy demand (correlation factor R²=0.89), the BiPV power plant model for the solar electricity produced on the EPFL buildings roofs (correlation factor R²=0.93) and the Mean Radiant Temperature model (correlation factor R²=0.92). The model is then analysed, according to the International Panel of Climate Change (IPCC), in three different future scenarios (B1, A1B and B2) for 2050 and 2100. The models show the impact of climate change in the energy demand of buildings, and in the urban microclimate. Two hypothetical refurbishment of the site, according to the Swiss Minergie and Minergie-P labels, are proposed to reduce the energy demand of buildings. Passive cooling strategies are applied in the future outdoor environment, able to decrease the hours of discomfort of pedestrians, according to their metabolic activity. Finally an optimal solution for 2050 is defined, which reduces the energy demand for heating and cooling (by 37% compared with the current thermo-physical characteristics of buildings projected in 2050), and ensures a comfortable outdoor environment for pedestrians during the different seasons.
This paper contains the simulations methodology, the simulations results and gives some insights about how to improve sustainability for the future urban design.
Keywords: outdoor thermal comfort, climate change, urban energy simulations
Taking into account building environment in the energy consumption evaluation
1IRSTV – FR CNRS 2488, France; 2CERMA - UMR MCC/CNRS 1563
In a context of new building regulations, buildings in France have now to be designed to keep their annual consumption under 50 kWh/m².year. Futur regulations could lead to build buildings which won't require any energy and will be able to ensure thermal comfort in summer. This substantially increases the need to use tools able to evaluate thermal behavior of buildings in a very precise way. In particular, evaluating heating and summer comfort needs at architectural design step become more and more crucial.
One of the main improvement which can be brought to the dynamic thermal simulation tools is to better consider the whole environment of the studied building. In particular, the long wave radiation exchanges between all buildings of an urban scene need be taken into account.
The aim of the study is to quantify the impact of considering infrared radiation exchanges between the building whose thermal behavior is simulated and its whole urban environment. The modifications of the infrared radiation fluxes are analysed and its impact on both energy needs and thermal comfort are then investigated.
Numerical simulations were carried out six buildings inserted into different French districts (three in Lyon and one in Nantes, Strasbourg and Paris) with different building densities. The 3D numerical tool takes into account the unsteady building thermal behavior using the SOLENE thermo-radiative model to evaluated both solar and infrared radiations. The urban surfaces are meshed into triangles on which energy balance are compute to estimate temperature. These surface temperature are coupled with the building thermal multi-zonal model which considers each floor of the building.
The six buildings are first studied without and then with their urban environment. Infrared radiation values modification between the two situations are analysed for the six buildings. As infrared radiation depends on the temperature surfaces involved in the case study, simulation for both summer and winter situations are carried out. The influence of the infrared modifications on energy need is evaluated in winter and on the thermal comfort in summer.
The results are analysed to compare the average infrared radiation received by the studied building. The infrared radiation distribution on the building surfaces are also investigated in order to have information about the dispersion of the values around the average infrared radiation. The influences on thermal comfort and energy consumption are given in regards to some indicators representing the building density. These results are expected to be able to provide precious information about the situation where it is (or not) necessary to take into account the influence of the urban environment in dynamic thermal simulation models.
Urban Greening and the UHI: Seasonal Trade-offs in Heating and Cooling Energy Consumption in Manchester, UK
1Qatar Green Building Council, Qatar; 2School of Education, Environment and Development, University of Manchester; 3School of Mechanical, Aerospace, and Civil Engineering, University of Manchester
In the UK, climate change projections estimate that mean summer air temperature will rise by approximately 3.5 °C by the 2080’s (medium emissions scenario, 50% probability level, 1961-1990 baseline). For urban areas, increasing the proportion of greenspace is an adaptation strategy that is often suggested. While numerous studies have investigated the cooling effect of greenspace in terms of both air and surface temperatures, few studies have further investigated the links to building energy demand.
This research presents an interdisciplinary approach to model fine-scale microclimate changes due to greenspace additions, using the results to develop customised weather files for modelling building energy consumption in commercial buildings. The CBD was modelled with the microclimate model ENVI-met with a range of greening scenarios for a summer day in July 2010. Both modelled and measured microclimate data were then used to develop a series of weather files for building energy modelling of three commercial building types (a three-storey shallow plan, a 10-storey shallow plan, and a three-storey deep-plan).
For the most effective scenario of adding 5% mature trees to the urban case study, the microclimate modelling estimated a maximum hourly air temperature reduction of nearly 0.7 °C at 5 pm. The building energy modelling estimated a reduction of 2.7% in July chiller energy due to the combination of reduced UHI peak hours and eight additional trees (four on the north side and four on the south side) surrounding a three-storey shallow plan building, with savings increasing to 4.8% under a three-day period of peak UHI conditions. While winter boiler energy usage is substantially reduced for a building in an urban location with a low proportion (approximately 3%) of greenspace, the wintertime benefit is marginal when analysed in terms of carbon trade-offs between summer cooling and winter heating requirements.
URBAN CANYONS MORPHOLOGY, THERMAL COMFORT AND URBAN DESIGN IN CONCEPCION'S CITY, CHILE
Pontificia Universidad católica de Chile, Chile
URBAN CANYONS MORPHOLOGY, THERMAL COMFORT AND URBAN DESIGN IN CONCEPCION'S CITY, CHILE
CRISTÓBAL LAMARCA GARCÍA
Arquitecto Universidad Finisterrae,
Magíster en Geografía y Geomática, Instituto de Geografía, Pontificia Universidad Católica de Chile
CRISTIÁN HENRÍQUEZ RUIZ
Geógrafo, Doctor en Ciencias Ambientales
Instituto de Geografía, Pontificia Universidad Católica de Chile
Proyecto Fondecyt 1130305, Centro Conicyt/Fondap CEDEUS y CIGIDEN
This study is part of understanding the urban microclimate at scale of the urban canyon and its relationship with thermal comfort and urban design. It were selected 9 urban canyons located in the metropolitan center of the city of Concepcion, Chile. For morphology analysis, Local Climate Zone classification system (Stewart and Oke, 2009) was applied. Fish eye photographs (sky view factor), height of buildings using LIDAR data, air temperature and wind speed obtained from field measurements, and solar radiation data and shadowing by Ecotect software, were studied. All these inputs are integrated in the Actual Sensation Vote (ASV) thermal comfort index (Nikolopoulou et al. 2004).These results were compared with thermal comfort survey passers, and then were interpreted considering urban design factors that have a significant impact on the thermal comfort of the public space during the summer.
Finally it is noted that as there are covered canyons, corresponding to "Tulipas" project, having higher degree of discomfort. On the other hand, the canyon of the diagonal street Pedro Aguirre Cerda regarding the urban net due to its characteristics of orientation and morphology is the one with the best rates of thermal comfort in relation to the physical aspects. While generally the metropolitan center of Concepcion is a comfortable place in summer it is expected that the future effects of climate change shift this condition. It is concluded that urban regulatory plans play a relevant role in adaptation measures.
Keywords: ActualSensation Vote, GIS, Sky View Factor, Climate adaptation.