Estimating and analysing the solar resource in territories

How much sun reaches a façade, a rooftop, a valley. And how to describe the variation without simulating every hour of every year.

In an open field, the solar resource fits into a single time series. In a city, the resource becomes a four-dimensional field. Every façade and every roof sees a different sky. Neighbouring buildings cast shade at different hours. The whole pattern turns with the seasons. In mountains, terrain adds cast shadows of its own.

This axis measures the variation and looks for compact descriptions. Principal component analysis, proper orthogonal decomposition and higher-order multilinear decomposition separate the spatial and temporal structures of the urban radiation field. A small number of modes then replaces a full simulation.

The workflows run on open tools and open data. Digital elevation models, BD TOPO, QGIS with the UMEP plugin, typical meteorological years from PVGIS. We compare façade irradiation tools against each other and we validate them. An unchecked model gives you nothing to plan with.