Markus Kayser’s Solar Sinter Project is a 3D printer powered by the sun and it uses the sand as the medium to create the objects it prints.

“In a world increasingly concerned with questions of energy production and raw material shortages, this project explores the potential of desert manufacturing, where energy and material occur in abundance.
In this experiment sunlight and sand are used as raw energy and material to produce glass objects using a 3D printing process, that combines natural energy and material with high-tech production technology.” 

via Slash Gear