Superconductors have long been considered a promising technology for the energy systems of the future. They can conduct electricity without resistance, thus eliminating both conduction losses and waste heat. Up to now, however, superconductors have only been applied in special cases, as in the immensely powerful magnet coils of particle accelerators such as the Large Hadron Collider at CERN. This is because superconductors must be well cooled, down to extremely low temperatures for some materials.