From here.
The environmental association Enviu (Environment and You) ans Döll – studio for the art of building, develop The Critical Mass: the idea of a dance club with a low enironmental footprint.
The concept was realized at the Off_Corso dance club in Rotterdam.

With the Sustainable Dance Club, Enviu and Doll have taken on the challenge of creating a sustainable environment within clubbing. Next to physical and design solutions, we’ve also looked at the organisation itself, but foremost at how to create a sustainable and fully recyclable environment. You only have to imagine the amount of energy, warmth and humidity that a club crowd produces on such an evening to see the great potential. Furthermore important are the program of the club, the food and beverages that are served and creating the natural conditions in which drinking and flirting can take place. As thus a place is constructed in which people can make a sustainable contribution to their environment whilst enjoying life.

In the sustainable dance club, electric energy is created by the moving of dancers on a piezoelectric floor. Piezoelectricity is the ability of crystals to generate a voltage in response to applied mechanical stress.
Such crystals are embedded in the dance club floor, generating electricity while people are jumping and dancing on.