HeHe is a Paris based art and design partnership set up in 1999 by Helen Evans and Heiko Hansen. Using a language based on light, sound and image, their practice explores the relationship between the individual and their architectural and urban environment.(info from here)
Nuage Vert proposes to use the chimney emissions of a power plant as a canvas for information flow. The intervention consists of tracking and projecting a laser image onto the contour of vapour, adjusting its shape and size to signal real-
time information. This information is collected by the power plant and relates to ecological activities of local residents.
Every night for two weeks during the February 2008, the vapour of Salmisaari will be illuminated, to show the current levels of electricity consumption by local residents. Before and during the event there will be a media campaign to ask
residents to consume less, climaxing with a date un-plug their electrical appliances to make the green cloud grow. (Info taken from the project pdf)