A Model for Mapping Solar Radiation in Urban Environment to Support the Design Process

Amir Eran
M.Sc. Thesis, 2012


Today, Architects and city planners are challenged with minimizing environmental impact and buildings’ energy footprint without increasing construction costs. Facilitating the use of energy from renewable sources and matching the human-made habitat to its natural climate and environment can be the solution. Recent laws standardizing the private solar energy production and the resell of surplus produced electricity to the state-owned electrical company are driving renewable energy solutions forward. The Israeli standard #5281 was updated in 2011 to conform to international standards, and was adapted to the local climate.
In addition to migrating from polluting fossil energy to clean renewable energy, efforts are also made to improve comfort conditions in buildings and their surroundings. Collection of solar energy is dependent on amount of solar irradiance, while ensuring thermal comfort relies on limiting the time of sunlight exposure or shading. An accurate evaluation of solar irradiance collected on BIPV surfaces can contribute to improving their performance and cost effectiveness. However, calculating the solar irradiance in a dense urban environment where mutual influence exists between buildings is a difficult, resource-intensive task. Mapping solar irradiance in an urban environment is desired by engineers for optimizing solar energy as well as for designers and planners for improving comfort conditions with shading solutions.
Multiple software tools are used in the process of modeling solar effects and optimizing BIPV systems. Architects and engineers use CAD software for building modeling, and energy simulation software for planning PV systems, as accurate estimation of system productivity is valuable for determining its profitability.
CAD software is used for modeling the buildings with their BIPV systems, and for calculating the shading effect on every surface. Engineering Software, on the other hand, is commonly used for determining the system configuration and technical parameters. This evaluation is done, most of the times, at a later stage, when the major building and structure decisions are already made.
The insufficient utilization of solar potential today is mostly due to lack of education of architects and planners, a shortage of accessible and simple software tools that are suitable for the early design phases. It is obvious that introducing “solar requirements” at a later phase is more expensive and does not allow for considerable changes.
Although multiple building energy simulation software are available today for evaluating building performance, most of them were initially developed with government funding with energy savings and efficiency in mind. As such, they remain an expert tool for analysts and engineers, and are not used by architects and planners. Their main disadvantage is the division between modeling software and engineering software, where there is no interaction between these two processes. Moreover, these tools are in use, most of the time, after the building design is already completed.
This work presents a model for mapping solar radiation in urban environment to support the design process. Our intention is to assist architects and urban planners in considering the solar energy potential during the initial design phases, when decisions that mostly impact the solar potential utilization of the building are made.
This model for mapping solar irradiance uses analysis and visualization of solar potential as a tool that assist in placing BIPV collectors in an urban environment.
In addition, this tool can assist with improving thermal comfort conditions in open spaces by determining the mutual influences of buildings surrounding these spaces.
The leading concept of this work is in presenting the solar energy potential directly on the 3D model itself thus allowing designers to use this evaluative layer of information to dynamically improve the model according to different parameters of solar irradiance, day lighting and shading. Using this tool during the initial design stages enable architects and planners to generate multiple design alternatives, evaluate and compare them, and iterate this process until a final design is achieved. The advantage of the early design phase is the flexibility to modify the design to maximize the solar potential. In addition, working with a single display that superimposes all data in one modeling environment is simpler since it does not require a transition between different environments, converting file formats, or learning new methods and workflows. Another advantage of working in a single modeling environment is the significant shortening of the irradiance calculation process, which in turn enables dynamic work and a more creative design experience.
The novelty of this work in comparison with other software environments for calculating solar irradiance collection is in the combination of these features:

  1. Uniting the 3D modeling environment with the solar irradiance collection energy simulation process, and displaying the simulation results as an additional information layer on top of the 3D model.
  2. Development and validation of a quick calculation method which allows multiple fast and accurate evaluations, to assist the design process.
  3. This tool can be used as a design generator, in creating and testing of multiple design alternatives for urban development, rather than a tool for evaluating the building’s energy performance after-the-fact.
  4. The variety of calculated data that is presented to the modeler for analysis includes not only the statistics of collected irradiance and shading, but also the amount of hours of direct sunlight exposure, a very useful feature for sustainable urban planning.