Modelling solar access at the window level of buildings – a case study for urban densification simulations in Sweden

Inglés. Buildings are a are a major consumer of energy in urban areas. The use of solar energy in buildings can help reduce CO2 emitting energy consumption in these urban areas. One way to use solar energy is through passive solar energy systems. Passive solar energy systems allow a building to use daylight as an energy source. The use of daylight as passive solar energy in Sweden could reduce the energy consumption in buildings by 23% to 42% which would help reduce CO2 emissions. Architects can design these passive solar energy systems for individual buildings in building modelling software suites, but to model them and study how they interact within a built environment, a 3D city modelling approach is needed. In Sweden, a project called 3CIM (3 city information model) is currently working on a 3D city modelling national standard in CityGML. The aim of this case study is to propose methods to study the effects of urban densification on buildings access to daylight in the Bellevue area in Malmö, Sweden. These methods enable estimation on how much daylight will reach the windows of a building’s façade. To do this 3D city models, data collected in the field, meteorological data, and building data for future planned buildings are used to simulate buildings daylight access. Since window information for buildings is not readily available in the current 3D city model, data collection methods for windows are also designed and implemented in support of this aim. A handheld camera was used for data collection and photoshop and OpenCV was used for photo corrections. From there Blender, a 3D modelling software, was used for 3D modelling of the windows. Next, the urban multi-scale environmental predictor (UMEP) was the tool used to model the estimated solar irradiance or “daylight” on the building roofs and façades. Finally, the daylight estimation tool (DET) was used to model the estimated solar irradiance at window level. The estimation methods developed are evaluated in two cycles. The first cycle includes the buildings that are present in physical space at the time of writing the thesis. The second cycle also includes proposed buildings in the Bellevue area. The output of this will be two reports of the results that includes the windows for each building façade, their geometry, and their solar irradiance values. The results showed a measurable change in the amount of solar energy that reaches the windows of the building facades. These results show that the data collection methods were successful in a scenario where window information isn’t readily available and needs to be collected. Next, the methods for 3D modelling the windows were also successful, though the process is time intensive. Future automation could streamline this process. Additionally, the methods for estimating the solar irradiance at façade level and window level were successful, with some limitations being data type and data availability. Finally, the overall results when comparing the results of the two cycles show that some buildings were affected more than others. The highest change to a building was ~20% and the lowest change was ~0% with the total buildings show an estimated ~4% change.

Inglés. As the global population increases, urban densification is one strategy that is implemented to accommodate the rising number of people in urban area. Urban densification is the increase of population per square kilometer that is often achieved by building taller, more compact buildings, closer together. It is important to study the effects of urban densification to determine the positive and negatives that may arise from these new implementations. One important aspect to study is access to daylight and solar energy. As new buildings inhabit formerly empty spaces, they risk negatively impacting the access to daylight which can have a correlated effect on energy consumption. The aim of this case study is to propose methods to study how urban areas access to daylight is affected when that area becomes denser from new buildings being built. This study was conducted in the Bellevue area in Malmö, Sweden. These methods estimate how much daylight will reach the windows located on the outer shell of the buildings. This requires the use of a 3D city model of the area, data collected while in the field, meteorological data to simulate sunlight, and drawings of buildings that are being proposed or planned for future construction in the area. Since the window information is not already included in the 3D city model of the area, a process to collect photos of the windows in the field was also designed and implemented in support of this aim. The first step used the window information collected to add windows to the 3D city model. The rest of this case study was carried out in two different cycles. The first cycle included only the buildings that are present in the study area at the time the study was conducted. The second cycle then adds in the planned buildings into the scenario. Each of these cycles involved two steps. The first step modelled how much daylight is estimated to reach the buildings. The second step estimated how much of that daylight is expected to reach the windows of the buildings. The comparison of the first and second cycle’s results showed an overall loss in access to daylight at the window level to the buildings in the study area. When looking at the individual buildings, some showed higher loss than others, while some buildings were not affected. The methods of this case study could be useful to city planners and developers when considering site selection for new buildings.