Abstract
Solar3D is an open-source software application designed to interactively calculate solar irradiation on three-dimensional (3D) surfaces in a virtual environment constructed with combinations of 3D-city models, digital elevation models (DEMs), digital surface models (DSMs) and feature layers. The GRASS GIS r.sun solar radiation model computes solar irradiation based on two-dimensional (2D) raster maps for a given day, latitude, surface and atmospheric conditions. With the increasing availability of 3D-city models and demand for solar energy, there is an urgent need for better tools to computes solar radiation directly with 3D-city models. Solar3D extends the GRASS GIS r.sun model from 2D to 3D by feeding the model with input, including surface slope, aspect and time-resolved shading, which is derived directly from the 3D scene using computer graphics techniques. To summarize, Solar3D offers several new features that—as a whole—distinguish this novel approach from existing 3D solar irradiation tools in the following ways. (1) Solar3D can consume massive heterogeneous 3D-city models, including massive 3D-city models such as oblique airborne photogrammetry-based 3D-city models (OAP3Ds or integrated meshes); (2) Solar3D can perform near real-time pointwise calculation for duration from daily to annual; (3) Solar3D can integrate and interactively explore large-scale heterogeneous geospatial data; (4) Solar3D can calculate solar irradiation at arbitrary surface positions including on rooftops, facades and the ground.
Highlights
Solar radiation models are used to estimate solar energy that reaches the Earth’s surface
Bearing in mind the above limitations, we developed a new solar irradiation tool designed to meet the following requirements. (1) to support pointwise calculation of daily to annual irradiation at arbitrary surfaces including at rooftops, facades and the ground; (2) to provide near real-time computation and feedback; (3) support for interactive exploration and calculation; (4) to support heterogeneous 3D-model formats, including common computer-aided design (CAD) model formats, OAP3Ds and building footprint extrusions; and (5) to support the mash-up of local- to global-scale geospatial data sources, including digital elevation models (DEMs), digital surface models (DSMs), imagery and feature layers with 2D and 3D symbology
The business logic of the core framework works in a loop triggered by user requests (Figure 2): (1) a user request is started by mouse-clicking at an exposed surface in a 3D scene rendered in an OpenSceneGraph view overlaid with the Solar3D user interface (UI) elements; (2) the 3D position, slope and aspect angle are derived from the clicked surface; (3) a cube map is rendered at the 3D position as described above; (4) all required model input [15], including the geographic location, Linkie turbidity factor, duration, temporal resolution
Summary
Solar radiation models are used to estimate solar energy that reaches the Earth’s surface. When modeling solar irradiation on the building scale, 2D raster maps are not able to represent complex geometric features such as vertical surfaces and overhangs, and the complexity of urban morphology can best be represented in three-dimensional (3D) city models in the form of triangular meshes. (1) to support pointwise calculation of daily to annual irradiation at arbitrary surfaces including at rooftops, facades and the ground; (2) to provide near real-time computation and feedback; (3) support for interactive exploration and calculation; (4) to support heterogeneous 3D-model formats, including common CAD model formats, OAP3Ds and building footprint extrusions; and (5) to support the mash-up of local- to global-scale geospatial data sources, including DEMs, DSMs, imagery and feature layers with 2D and 3D symbology Bearing in mind the above limitations, we developed a new solar irradiation tool designed to meet the following requirements. (1) to support pointwise calculation of daily to annual irradiation at arbitrary surfaces including at rooftops, facades and the ground; (2) to provide near real-time computation and feedback; (3) support for interactive exploration and calculation; (4) to support heterogeneous 3D-model formats, including common CAD model formats, OAP3Ds and building footprint extrusions; and (5) to support the mash-up of local- to global-scale geospatial data sources, including DEMs, DSMs, imagery and feature layers with 2D and 3D symbology
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