Working for experimental company Cloud9, James Clar is building a working prototype for a model of the Habitat Hotel, near Barcelona. He says:

It is a hotel with a light mesh that wraps the whole building. The light mesh has sensors that will read the daylight sun amplitude and then at night each node will give off color according to how much that node collected sun. Therefore, the mesh reflects the energy levels of each day, it will change over seasons and due to weather.

[found on pixelsumo]