Tool measures solar incidence levels of roof structures

The Swedish researchers have surveyed Gothenburg in their pilot project, which they believe is able to determine the maximum magnitude of solar incidence in a whole town, a neighbourhood or one particular roof.

‘The roof structures of a town may be more or less suitable for the installation of solar panels, depending on factors such as how much a particular roof is shadowed by surrounding buildings and vegetation, the gradient of the roof and the angle of incidence of sunlight,’ said Fredrik Lindberg of Gothenburg University’s Department of Earth Sciences.

‘It is now possible for the first time to determine how much solar energy a particular roof will receive during the year,’ he continued.

The scientists at the university have worked together with consultancy WSP to develop a geographical information system (GIS) that can calculate the suitability of a roof to house solar panels. The system is called SEES — Solar Energy from Existing Structures — and will be freely available to companies and municipalities.

The tool is based on a computer-based GIS that collects, stores, analyses and presents geographical data. This means that the tool describes real roofs in their surroundings. The sun in the model illuminates the 3D built environment and simulates how surrounding buildings, terrain and vegetation throw shadows.

The shadow effect can be calculated for each month or for a complete year, and this means that certain parts of a roof may turn out to be unsuitable for collecting solar energy, even though the roof has both optimal direction and gradient. In this way, it is possible to calculate the total solar radiation on each part of a roof structure within a given area, calculated as kilowatt hours per square metre.

The developers claim that SEES can provide a map of the suitability, based on the user’s requirements for good, less good and poor annual solar incidence.

‘We have used Gothenburg as a pilot town in the project, but the method can be used in all municipalities where the necessary data is made available,’ said Lindberg. ‘The users can judge the suitability of a roof for solar voltaic panels or solar thermal panels across a wide range based on this.’