Dance clubs are also getting in on the action. In the Netherlands, Rotterdam's new Club WATT has a floor that harnesses the energy created by the dancers' steps. Designed by a Dutch company called the Sustainable Dance Club, the floor is based on the piezoelectric effect, in which certain materials produce an electric current when compressed or bent. (The most common example is a cigarette lighter, in which a hammer causes a spark to be emitted when it strikes a piezoelectric crystal.) As clubgoers dance, the floor is compressed by less than half an inch. It makes contact with the piezoelectric material under it and generates anywhere from two to 20 watts of electricity, depending on the impact of the patrons' feet. For now, it's just enough to power LED lights in the floor, but in the future, more output is expected from newer technology. In London, Surya, another new eco-nightclub, uses the same principle for its dance floor, which the owners hope will one day generate 60 percent of the club's electricity.