sentences:  Energy exchanges have become an established part of the liberalized energy markets in Europe.They serve as an important supplement to short-term OTC trading and also function as an independent price indicator for electric energy on the wholesale market.While the energy markets in Central Europe often involve a single electricity producer, or multiple electricity producers that auction their energy in tranches, or via long-term bilateral supply contracts,
  an energy exchange contributes to increasing price efficiency and allows electric utilities to react flexibly when facing a changing demand/supply structure.